Take the signature, the expiry and the URL scheme off the image request (closes #314)

The image request now holds only its source and its transform, exactly what
the variant key covers. The /v1/image/ handler checks the allowlist and
verifies the signature itself with Signer.Verify(req, sig, expires). Both
image handlers keep the URL's expiry as a local value for Cache-Control. The
image service holds no signer, allowlist or AllowHTTP, and ValidateRequest is
gone. The fetcher takes the source and builds its URL with Source.URL from its
own AllowHTTP, so no URL string is built and parsed again. chooseAutoFormat
returns the format it chooses instead of writing into the request. The signed
URL format and every route's answers are unchanged.

Model: opus-5-5

TODO.md

@@ -30,6 +30,27 @@ P2: security: per-origin rate limiting
 
 # Completed Steps
 
+- 2026-10-26 the image request holds only what names the cached object (closes
+  #314): its source and its transform, which the variant key covers. The signed
+  URL format, the signing algorithm and every route's answers are unchanged.
+    - The `/v1/image/` handler checks `allowlist_hosts` and verifies the
+      signature itself, with `Signer.Verify(req, sig, expires)`.
+    - Each image handler keeps its URL's expiry as a value of its own, for
+      `Cache-Control`. `encurl`'s `Generate` takes the expiry and its `Parse`
+      returns it.
+    - The fetcher takes the source and builds its URL with `Source.URL`, over
+      http only when the fetcher's own `AllowHTTP` is set. `validateURL` takes
+      that URL, so no URL string is built and parsed again.
+    - `chooseAutoFormat` returns the format it chooses, and the handler puts it
+      into the request it parsed.
+    - The image service serves images through `Get`, and has `WaitForProcessing`
+      for shutdown.
+    - Removed:
+        - `Signature`, `Expires`, `AllowHTTP` and `SourceURL` of the image
+          request
+        - `Service.ValidateRequest`, and the service's signer, allowlist and
+          `AllowHTTP`
+        - `extractHost` of the fetcher and `urlToFSPath` of the mock fetcher
 - 2026-10-26 pixad's fx graph builds the image pipeline (closes #313).
   `database.New` now opens the database, so the parts below can read it while
   they are built; its stop hook still runs after the cache's. The cache's

internal/encurl/encurl.go

@@ -59,12 +59,14 @@ func NewGenerator(signingKey string) (*Generator, error) {
 	return &Generator{key: key}, nil
 }
 
-// Generate creates an encrypted URL token from the request's source,
-// transform and expiry, each as the request holds it; an empty format, a
-// quality of 0 or an empty fit mode is left out of the token, and a zero
-// Expires makes a token that never expires. The token is CBOR-encoded,
+// Generate creates an encrypted URL token from the request's source and
+// transform, each as the request holds it, and from expires; an empty format,
+// a quality of 0 or an empty fit mode is left out of the token, and a zero
+// expires makes a token that never expires. The token is CBOR-encoded,
 // encrypted with NaCl secretbox, and base64url-encoded.
-func (g *Generator) Generate(req *imagerequest.Request) (string, error) {
+func (g *Generator) Generate(
+	req *imagerequest.Request, expires time.Time,
+) (string, error) {
 	p := &payload{
 		SourceHost:  req.Source.Host,
 		SourcePath:  req.Source.Path,
@@ -76,8 +78,8 @@ func (g *Generator) Generate(req *imagerequest.Request) (string, error) {
 		FitMode:     req.Transform.FitMode,
 	}
 
-	if !req.Expires.IsZero() {
-		p.ExpiresAt = req.Expires.Unix()
+	if !expires.IsZero() {
+		p.ExpiresAt = expires.Unix()
 	}
 
 	// CBOR encode the payload
@@ -91,19 +93,19 @@ func (g *Generator) Generate(req *imagerequest.Request) (string, error) {
 }
 
 // Parse decrypts and validates an encrypted URL token and returns the
-// request it holds, with default values for omitted optional fields. A token
-// that never expires gives the zero Expires.
+// request it holds, with default values for omitted optional fields, and its
+// expiry. A token that never expires gives the zero time.
 // Returns ErrExpired if the token has expired, or other errors for invalid tokens.
-func (g *Generator) Parse(token string) (*imagerequest.Request, error) {
+func (g *Generator) Parse(token string) (*imagerequest.Request, time.Time, error) {
 	// Decrypt
 	data, err := seal.Decrypt(g.key, token)
 	if err != nil {
 		if errors.Is(err, seal.ErrDecryptionFailed) ||
 			errors.Is(err, seal.ErrInvalidPayload) {
-			return nil, ErrDecryptFailed
+			return nil, time.Time{}, ErrDecryptFailed
 		}
 
-		return nil, err
+		return nil, time.Time{}, err
 	}
 
 	// CBOR decode
@@ -111,12 +113,12 @@ func (g *Generator) Parse(token string) (*imagerequest.Request, error) {
 
 	err = cbor.Unmarshal(data, &p)
 	if err != nil {
-		return nil, ErrInvalidFormat
+		return nil, time.Time{}, ErrInvalidFormat
 	}
 
 	// Check expiration (0 = never expires)
 	if p.ExpiresAt != 0 && time.Now().Unix() > p.ExpiresAt {
-		return nil, ErrExpired
+		return nil, time.Time{}, ErrExpired
 	}
 
 	format := p.Format
@@ -151,6 +153,5 @@ func (g *Generator) Parse(token string) (*imagerequest.Request, error) {
 			Quality: quality,
 			FitMode: fitMode,
 		},
-		Expires: expires,
-	}, nil
+	}, expires, nil
 }

internal/encurl/encurl_test.go

@@ -36,10 +36,10 @@ func TestGenerator_GenerateAndParse(t *testing.T) {
 			Quality: 90,
 			FitMode: imagerequest.FitContain,
 		},
-		Expires: time.Now().Add(time.Hour),
 	}
+	expires := time.Now().Add(time.Hour)
 
-	token, err := gen.Generate(req)
+	token, err := gen.Generate(req, expires)
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}
@@ -48,7 +48,7 @@ func TestGenerator_GenerateAndParse(t *testing.T) {
 		t.Fatal("Generate() returned empty token")
 	}
 
-	parsed, err := gen.Parse(token)
+	parsed, parsedExpires, err := gen.Parse(token)
 	if err != nil {
 		t.Fatalf("Parse() error = %v", err)
 	}
@@ -91,8 +91,8 @@ func TestGenerator_GenerateAndParse(t *testing.T) {
 			parsed.Transform.FitMode, req.Transform.FitMode)
 	}
 
-	if parsed.Expires.Unix() != req.Expires.Unix() {
-		t.Errorf("ExpiresAt = %d, want %d", parsed.Expires.Unix(), req.Expires.Unix())
+	if parsedExpires.Unix() != expires.Unix() {
+		t.Errorf("ExpiresAt = %d, want %d", parsedExpires.Unix(), expires.Unix())
 	}
 }
 
@@ -106,15 +106,14 @@ func TestGenerator_Parse_Expired(t *testing.T) {
 			Host: testSourceHost,
 			Path: testSourcePath,
 		},
-		Expires: time.Now().Add(-time.Hour), // Already expired
 	}
 
-	token, err := gen.Generate(req)
+	token, err := gen.Generate(req, time.Now().Add(-time.Hour)) // Already expired
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}
 
-	_, err = gen.Parse(token)
+	_, _, err = gen.Parse(token)
 	if err == nil {
 		t.Error("Parse() should fail for expired token")
 	}
@@ -129,7 +128,7 @@ func TestGenerator_Parse_InvalidToken(t *testing.T) {
 
 	gen, _ := encurl.NewGenerator("test-signing-key-12345")
 
-	_, err := gen.Parse("not-a-valid-token")
+	_, _, err := gen.Parse("not-a-valid-token")
 	if err == nil {
 		t.Error("Parse() should fail for invalid token")
 	}
@@ -145,10 +144,9 @@ func TestGenerator_Parse_TamperedToken(t *testing.T) {
 			Host: testSourceHost,
 			Path: testSourcePath,
 		},
-		Expires: time.Now().Add(time.Hour),
 	}
 
-	token, _ := gen.Generate(req)
+	token, _ := gen.Generate(req, time.Now().Add(time.Hour))
 
 	// Tamper with the token
 	tampered := []byte(token)
@@ -156,7 +154,7 @@ func TestGenerator_Parse_TamperedToken(t *testing.T) {
 		tampered[10] ^= 0x01
 	}
 
-	_, err := gen.Parse(string(tampered))
+	_, _, err := gen.Parse(string(tampered))
 	if err == nil {
 		t.Error("Parse() should fail for tampered token")
 	}
@@ -173,12 +171,11 @@ func TestGenerator_Parse_WrongKey(t *testing.T) {
 			Host: testSourceHost,
 			Path: testSourcePath,
 		},
-		Expires: time.Now().Add(time.Hour),
 	}
 
-	token, _ := gen1.Generate(req)
+	token, _ := gen1.Generate(req, time.Now().Add(time.Hour))
 
-	_, err := gen2.Parse(token)
+	_, _, err := gen2.Parse(token)
 	if err == nil {
 		t.Error("Parse() should fail with different signing key")
 	}
@@ -195,13 +192,12 @@ func TestGenerator_Parse_Defaults(t *testing.T) {
 			Host: testSourceHost,
 			Path: testSourcePath,
 		},
-		Expires: time.Now().Add(time.Hour),
-	})
+	}, time.Now().Add(time.Hour))
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}
 
-	req, err := gen.Parse(token)
+	req, _, err := gen.Parse(token)
 	if err != nil {
 		t.Fatalf("Parse() error = %v", err)
 	}
@@ -232,10 +228,9 @@ func TestGenerator_TokenIsURLSafe(t *testing.T) {
 			Host: testSourceHost,
 			Path: testSourcePath,
 		},
-		Expires: time.Now().Add(time.Hour),
 	}
 
-	token, _ := gen.Generate(req)
+	token, _ := gen.Generate(req, time.Now().Add(time.Hour))
 
 	// Check that token only contains URL-safe characters
 	for _, c := range token {

internal/handlers/auth.go

@@ -153,20 +153,20 @@ func (s *Handlers) HandleGenerateURL() http.HandlerFunc {
 			return
 		}
 
-		// The image URL must fetch the source URL as it was written
-		req.AllowHTTP = s.config.AllowHTTP
-		fetchURL := req.SourceURL()
+		// The image URL must fetch the source URL as it was written. The
+		// fetcher fetches over http only when allow_http is set.
+		fetchURL := req.Source.URL(s.config.AllowHTTP)
 
 		if !fetchedAsWritten(parsed, fetchURL) {
 			s.renderGeneratorWithForm(w, r, "Source URL cannot be fetched as "+
-				"written: pixa would fetch "+fetchURL,
+				"written: pixa would fetch "+fetchURL.String(),
 				r.Form, http.StatusBadRequest)
 
 			return
 		}
 
 		// Generate encrypted token
-		token, err := s.encGen.Generate(req)
+		token, err := s.encGen.Generate(req, expiresAt)
 		if err != nil {
 			s.log.Error("failed to generate encrypted URL", "error", err)
 			s.renderGeneratorWithForm(w, r, "Failed to generate URL", r.Form,
@@ -226,25 +226,23 @@ func parseSourceURL(sourceURL string) (*url.URL, error) {
 // in RawPath when it is not the decoded path percent-encoded again.
 // EscapedPath ignores RawPath when it also holds a character net/url encodes,
 // such as a space, so RawPath is compared itself.
-func fetchedAsWritten(source *url.URL, fetchURL string) bool {
+func fetchedAsWritten(source, fetchURL *url.URL) bool {
 	writtenPath := source.RawPath
 	if writtenPath == "" {
 		writtenPath = source.EscapedPath()
 	}
 
-	fetched, err := url.Parse(fetchURL)
-
-	return err == nil && source.User == nil && !source.ForceQuery &&
-		fetched.EscapedPath() == writtenPath &&
-		fetched.RawQuery == source.RawQuery
+	return source.User == nil && !source.ForceQuery &&
+		fetchURL.EscapedPath() == writtenPath &&
+		fetchURL.RawQuery == source.RawQuery
 }
 
 // buildGenerateRequest parses the numeric form fields and assembles the
-// image request the encrypted URL's token is made from. ttl=0 means never
-// expires (Expires stays the zero time). A non-numeric or out-of-range
-// width, height, quality or ttl, or an unrecognized fit mode, is a client
-// error naming the offending field. The format field is passed through
-// unchecked.
+// image request the encrypted URL's token is made from, and its expiry.
+// ttl=0 means never expires (the expiry is the zero time). A non-numeric or
+// out-of-range width, height, quality or ttl, or an unrecognized fit mode, is
+// a client error naming the offending field. The format field is passed
+// through unchecked.
 func buildGenerateRequest(
 	parsed *url.URL, form url.Values,
 ) (*imagerequest.Request, time.Time, int, error) {
@@ -294,7 +292,6 @@ func buildGenerateRequest(
 			Quality: quality,
 			FitMode: fitMode,
 		},
-		Expires: expiresAt,
 	}
 
 	return req, expiresAt, ttl, nil

internal/handlers/cache_hit_internal_test.go

@@ -19,11 +19,13 @@ import (
 	"github.com/go-chi/chi/v5"
 	"github.com/prometheus/client_golang/prometheus"
 
+	"sneak.berlin/go/pixa/internal/allowlist"
 	"sneak.berlin/go/pixa/internal/database"
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
 	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/imgcache"
+	"sneak.berlin/go/pixa/internal/signature"
 )
 
 // countingHost is the allowlisted host whose photoPath the server of
@@ -137,8 +139,6 @@ func newCountingDatabaseServer(
 			MaxInputBytes:           50 << 20,
 			MaxConcurrentProcessing: 2,
 		}),
-		SigningKey:      testSigningKey,
-		Allowlist:       []string{countingHost},
 		MaxResponseSize: 50 << 20,
 		Logger:          slog.New(slog.DiscardHandler),
 	})
@@ -159,15 +159,17 @@ func newCountingDatabaseServer(
 			Quality: 85,
 			FitMode: imagerequest.FitCover,
 		},
-	})
+	}, time.Time{})
 	if err != nil {
 		tb.Fatalf("encGen.Generate() error = %v", err)
 	}
 
 	h := &Handlers{
-		log:    slog.New(slog.DiscardHandler),
-		imgSvc: svc,
-		encGen: encGen,
+		log:       slog.New(slog.DiscardHandler),
+		imgSvc:    svc,
+		encGen:    encGen,
+		signer:    signature.New(testSigningKey),
+		allowlist: allowlist.New([]string{countingHost}),
 	}
 
 	r := chi.NewRouter()

internal/handlers/first_bytes_internal_test.go

@@ -13,11 +13,13 @@ import (
 
 	"github.com/go-chi/chi/v5"
 	"github.com/prometheus/client_golang/prometheus"
+	"sneak.berlin/go/pixa/internal/allowlist"
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
 	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/imgcache"
+	"sneak.berlin/go/pixa/internal/signature"
 )
 
 // mismatchedSourcePath is the path of the source that
@@ -27,8 +29,9 @@ import (
 const mismatchedSourcePath = "/images/source.png"
 
 // newRoutesFetchingThrough returns both image routes, and the Handlers behind
-// them, whose image service fetches through fetcher and has allowlistedHost on
-// its allowlist. The handlers and the image service log to log.
+// them, whose image service fetches through fetcher, and which have
+// allowlistedHost on their allowlist. The handlers and the image service log
+// to log.
 func newRoutesFetchingThrough(
 	t *testing.T, fetcher httpfetcher.Fetcher, log *slog.Logger,
 ) (*Handlers, http.Handler) {
@@ -50,8 +53,6 @@ func newRoutesFetchingThrough(
 			MaxInputBytes:           50 << 20,
 			MaxConcurrentProcessing: 2,
 		}),
-		SigningKey:      testSigningKey,
-		Allowlist:       []string{allowlistedHost},
 		MaxResponseSize: 50 << 20,
 		Logger:          log,
 	})
@@ -64,7 +65,13 @@ func newRoutesFetchingThrough(
 		t.Fatalf("encurl.NewGenerator() error = %v", err)
 	}
 
-	h := &Handlers{log: log, imgSvc: svc, encGen: encGen}
+	h := &Handlers{
+		log:       log,
+		imgSvc:    svc,
+		encGen:    encGen,
+		signer:    signature.New(testSigningKey),
+		allowlist: allowlist.New([]string{allowlistedHost}),
+	}
 
 	r := chi.NewRouter()
 	r.Get("/v1/image/*", h.HandleImage())
@@ -93,7 +100,7 @@ func mismatchedSourceEncURL(t *testing.T, h *Handlers) string {
 			Size:   imagerequest.Size{Width: 50, Height: 50},
 			Format: imagerequest.FormatJPEG,
 		},
-	})
+	}, time.Time{})
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}

internal/handlers/format_auto.go

@@ -18,16 +18,17 @@ var (
 		"image/jxl, image/avif, image/webp or image/jpeg")
 )
 
-// chooseAutoFormat replaces the format auto in req with the format
-// formatForAccept chooses from r's Accept header, and adds Vary: Accept to the
+// chooseAutoFormat returns the format to serve for the requested format: for
+// the format auto, the format formatForAccept chooses from r's Accept header,
+// and any other format as it is. For auto it adds Vary: Accept to the
 // response, which then depends on that header. It answers 400 for an Accept
 // header that is not valid and 406 for one that allows none of the formats,
-// and reports whether req can be served. Any other format is left as it is.
+// and reports whether the image can be served.
 func (s *Handlers) chooseAutoFormat(
-	w http.ResponseWriter, r *http.Request, req *imagerequest.Request,
-) bool {
-	if req.Transform.Format != imagerequest.FormatAuto {
-		return true
+	w http.ResponseWriter, r *http.Request, requested imagerequest.Format,
+) (imagerequest.Format, bool) {
+	if requested != imagerequest.FormatAuto {
+		return requested, true
 	}
 
 	w.Header().Add("Vary", "Accept")
@@ -36,18 +37,16 @@ func (s *Handlers) chooseAutoFormat(
 	if errors.Is(err, errNotAcceptable) {
 		s.respondError(w, err.Error(), http.StatusNotAcceptable)
 
-		return false
+		return "", false
 	}
 
 	if err != nil {
 		s.respondError(w, err.Error(), http.StatusBadRequest)
 
-		return false
+		return "", false
 	}
 
-	req.Transform.Format = format
-
-	return true
+	return format, true
 }
 
 // formatForAccept returns the format an auto URL is served in for the Accept

internal/handlers/format_auto_internal_test.go

@@ -75,9 +75,9 @@ func TestFormatForAccept(t *testing.T) {
 
 // autoPhotoURLs returns a signed /v1/image/ URL and an encrypted /v1/e/ URL,
 // both valid for a minute, for the JPEG at photoPath on signedHost at 50x50 in
-// the format auto. The first is signed with testSigningKey, the key of the
-// image service newSignedHostServer builds, and the second is made with h's
-// generator.
+// the format auto. The first is signed with testSigningKey, the key the
+// handlers that newSignedHostServer builds check signatures with. The second
+// is made with h's generator.
 func autoPhotoURLs(t *testing.T, h *Handlers) (string, string) {
 	t.Helper()
 
@@ -101,8 +101,7 @@ func autoPhotoURLs(t *testing.T, h *Handlers) (string, string) {
 			Size:   imagerequest.Size{Width: 50, Height: 50},
 			Format: imagerequest.FormatAuto,
 		},
-		Expires: time.Now().Add(time.Minute),
-	})
+	}, time.Now().Add(time.Minute))
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}

internal/handlers/handlers.go

@@ -16,6 +16,7 @@ import (
 	"sneak.berlin/go/pixa/internal/imgcache"
 	"sneak.berlin/go/pixa/internal/logger"
 	"sneak.berlin/go/pixa/internal/session"
+	"sneak.berlin/go/pixa/internal/signature"
 )
 
 // Params defines dependencies for Handlers.
@@ -41,6 +42,11 @@ type Handlers struct {
 	encGen      *encurl.Generator
 	csrfProtect func(http.Handler) http.Handler
 
+	// signer checks the signature of a /v1/image/ URL with signing_key.
+	signer *signature.Signer
+	// allowlist matches the hosts of allowlist_hosts, which a /v1/image/
+	// URL may name without a signature.
+	allowlist *allowlist.HostAllowList
 	// refererBlocklist matches the hosts of referer_blocklist; its IsAllowed
 	// reports whether a URL's host is on that list.
 	refererBlocklist *allowlist.HostAllowList
@@ -61,6 +67,8 @@ func New(_ fx.Lifecycle, params Params) (*Handlers, error) {
 		sessMgr:          params.SessionManager,
 		encGen:           params.EncryptedURLGenerator,
 		csrfProtect:      csrfProtect,
+		signer:           signature.New(params.Config.SigningKey),
+		allowlist:        allowlist.New(params.Config.AllowlistHosts),
 		refererBlocklist: allowlist.New(params.Config.RefererBlocklist),
 	}, nil
 }

internal/handlers/handlers_internal_test.go

@@ -19,10 +19,13 @@ import (
 
 	"github.com/go-chi/chi/v5"
 	"github.com/prometheus/client_golang/prometheus"
+	"sneak.berlin/go/pixa/internal/allowlist"
 	"sneak.berlin/go/pixa/internal/database"
 	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
+	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/imgcache"
+	"sneak.berlin/go/pixa/internal/signature"
 )
 
 // testFixtures contains test data.
@@ -62,8 +65,6 @@ func setupTestHandler(t *testing.T) *testFixtures {
 			MaxInputBytes:           50 << 20,
 			MaxConcurrentProcessing: 2,
 		}),
-		SigningKey:      "test-signing-key-must-be-32-chars",
-		Allowlist:       []string{goodHost},
 		MaxResponseSize: 50 << 20,
 	})
 	if err != nil {
@@ -71,8 +72,10 @@ func setupTestHandler(t *testing.T) *testFixtures {
 	}
 
 	h := &Handlers{
-		imgSvc: svc,
-		log:    slog.Default(),
+		imgSvc:    svc,
+		log:       slog.Default(),
+		signer:    signature.New("test-signing-key-must-be-32-chars"),
+		allowlist: allowlist.New([]string{goodHost}),
 	}
 
 	return &testFixtures{
@@ -127,10 +130,9 @@ func newMockFetcher(fs fs.FS) *mockFetcher {
 }
 
 func (f *mockFetcher) Fetch(
-	_ context.Context, url string,
+	_ context.Context, source imagerequest.Source,
 ) (*httpfetcher.FetchResult, error) {
-	// Remove https:// prefix
-	path := url[8:] // Remove "https://"
+	path := source.Host + source.Path
 
 	data, err := fs.ReadFile(f.fs, path)
 	if err != nil {

internal/handlers/image.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"net/url"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/go-chi/chi/v5/middleware"
@@ -27,13 +28,13 @@ func (s *Handlers) HandleImage() http.HandlerFunc {
 			return
 		}
 
-		req, ok := s.parseImageRequest(w, r)
+		req, sig, expires, ok := s.parseImageRequest(w, r)
 		if !ok {
 			return
 		}
 
 		// Validate signature if required
-		err := s.imgSvc.ValidateRequest(req)
+		err := s.validateSignature(req, sig, expires)
 		if err != nil {
 			s.log.Warn("signature validation failed",
 				"host", req.Source.Host,
@@ -46,10 +47,13 @@ func (s *Handlers) HandleImage() http.HandlerFunc {
 		}
 
 		// The signature covers the format auto, not the format chosen
-		if !s.chooseAutoFormat(w, r, req) {
+		format, ok := s.chooseAutoFormat(w, r, req.Transform.Format)
+		if !ok {
 			return
 		}
 
+		req.Transform.Format = format
+
 		// Get cache key for logging
 		cacheKey := imagerequest.CacheKey(req)
 
@@ -65,7 +69,7 @@ func (s *Handlers) HandleImage() http.HandlerFunc {
 
 		defer func() { _ = resp.Content.Close() }()
 
-		s.writeImageResponse(w, r, req, resp, cacheKey, startTime)
+		s.writeImageResponse(w, r, req, expires, resp, cacheKey, startTime)
 	}
 }
 
@@ -82,11 +86,11 @@ func (s *Handlers) HandleRobotsTxt() http.HandlerFunc {
 }
 
 // parseImageRequest parses the image URL's path and query parameters into
-// an image request. On invalid input it writes an error response and
-// returns false.
+// an image request, and returns it with the URL's signature and expiry. On
+// invalid input it writes an error response and returns false.
 func (s *Handlers) parseImageRequest(
 	w http.ResponseWriter, r *http.Request,
-) (*imagerequest.Request, bool) {
+) (*imagerequest.Request, string, time.Time, bool) {
 	// The path is parsed decoded once, as r.URL.Path holds it, and not from
 	// chi's wildcard: chi routes on the path as the client wrote it whenever
 	// that is not Go's own encoding of it, so its wildcard would still hold
@@ -100,7 +104,7 @@ func (s *Handlers) parseImageRequest(
 		)
 		s.respondError(w, "invalid image URL: "+err.Error(), http.StatusBadRequest)
 
-		return nil, false
+		return nil, "", time.Time{}, false
 	}
 
 	// Parse signature params from query string. r.URL.Query() would silently
@@ -113,7 +117,7 @@ func (s *Handlers) parseImageRequest(
 		s.respondError(w, fmt.Sprintf("invalid query string %q: %v",
 			r.URL.RawQuery, err), http.StatusBadRequest)
 
-		return nil, false
+		return nil, "", time.Time{}, false
 	}
 
 	for name, values := range query {
@@ -121,17 +125,15 @@ func (s *Handlers) parseImageRequest(
 			s.respondError(w, fmt.Sprintf("invalid %s: given more than once",
 				name), http.StatusBadRequest)
 
-			return nil, false
+			return nil, "", time.Time{}, false
 		}
 	}
 
-	req.Signature = query.Get("sig")
-
-	req.Expires, err = parseExpires(query)
+	expires, err := parseExpires(query)
 	if err != nil {
 		s.respondError(w, err.Error(), http.StatusBadRequest)
 
-		return nil, false
+		return nil, "", time.Time{}, false
 	}
 
 	// Parse optional quality and fit params. Only a q missing from the URL is
@@ -143,7 +145,7 @@ func (s *Handlers) parseImageRequest(
 		s.respondError(w, `invalid q: not a number, got ""`,
 			http.StatusBadRequest)
 
-		return nil, false
+		return nil, "", time.Time{}, false
 	}
 
 	req.Transform.Quality, err = parseFormInt(query, "q",
@@ -152,7 +154,7 @@ func (s *Handlers) parseImageRequest(
 		s.respondError(w, fmt.Sprintf("%v, got %q", err, qStr),
 			http.StatusBadRequest)
 
-		return nil, false
+		return nil, "", time.Time{}, false
 	}
 
 	// Only a fit missing from the URL is cover. A fit in the URL that is not a
@@ -162,7 +164,7 @@ func (s *Handlers) parseImageRequest(
 	if query.Has("fit") && req.Transform.FitMode == "" {
 		s.respondError(w, `invalid fit: not a fit mode, got ""`, http.StatusBadRequest)
 
-		return nil, false
+		return nil, "", time.Time{}, false
 	}
 
 	// Default fit mode if not set
@@ -179,10 +181,35 @@ func (s *Handlers) parseImageRequest(
 		s.respondError(w, "invalid image request: "+err.Error(),
 			http.StatusBadRequest)
 
-		return nil, false
+		return nil, "", time.Time{}, false
 	}
 
-	return req, true
+	return req, query.Get("sig"), expires, true
+}
+
+// validateSignature returns nil when the source host of req is on
+// allowlist_hosts and names no port. Otherwise it verifies sig, the URL's
+// signature of req, and expires, the URL's expiry.
+func (s *Handlers) validateSignature(
+	req *imagerequest.Request, sig string, expires time.Time,
+) error {
+	// An allowlist entry names no port, so a host followed by ":", with or
+	// without a port, needs a signature. Go's URL type reads the port as the
+	// fetcher does: in an IPv6 address written without brackets, such as
+	// 2001:db8::1:8443, it is what follows the last ":". This is checked here
+	// and not in allowlist.IsAllowed, which also matches referer_blocklist,
+	// where a Referer must be blocked whatever its port. Port and IsAllowed
+	// read only the host of a URL.
+	sourceURL := &url.URL{Host: req.Source.Host}
+	hostHasPort := sourceURL.Port() != "" ||
+		strings.HasSuffix(sourceURL.Host, ":")
+
+	if !hostHasPort && s.allowlist.IsAllowed(sourceURL) {
+		return nil
+	}
+
+	// Signature required for non-allowed hosts
+	return s.signer.Verify(req, sig, expires)
 }
 
 // parseExpires reads the exp query parameter, a Unix time in seconds. An exp
@@ -341,10 +368,11 @@ func notModified(w http.ResponseWriter, r *http.Request, etag string) bool {
 }
 
 // writeImageResponse writes headers and streams the image content,
-// handling conditional and HEAD requests.
+// handling conditional and HEAD requests. expires is the URL's expiry, which
+// ends the Cache-Control max-age.
 func (s *Handlers) writeImageResponse(
 	w http.ResponseWriter, r *http.Request,
-	req *imagerequest.Request, resp *imgcache.ImageResponse,
+	req *imagerequest.Request, expires time.Time, resp *imgcache.ImageResponse,
 	cacheKey imagerequest.VariantKey, startTime time.Time,
 ) {
 	// Set response headers
@@ -355,7 +383,7 @@ func (s *Handlers) writeImageResponse(
 	}
 
 	// Cache control headers
-	w.Header().Set("Cache-Control", cacheControl(req.Expires))
+	w.Header().Set("Cache-Control", cacheControl(expires))
 	w.Header().Set("X-Pixa-Cache", string(resp.CacheStatus))
 
 	if notModified(w, r, resp.ETag) {

internal/handlers/image_cache_control_internal_test.go

@@ -14,10 +14,12 @@ import (
 	"github.com/go-chi/chi/v5"
 	"github.com/prometheus/client_golang/prometheus"
 
+	"sneak.berlin/go/pixa/internal/allowlist"
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
 	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/imgcache"
+	"sneak.berlin/go/pixa/internal/signature"
 )
 
 // photoPath is the path of the JPEG that newSignedHostServer serves.
@@ -52,7 +54,6 @@ func newSignedHostServer(
 			MaxInputBytes:           50 << 20,
 			MaxConcurrentProcessing: 2,
 		}),
-		SigningKey:      testSigningKey,
 		MaxResponseSize: 50 << 20,
 		Logger:          log,
 	})
@@ -66,9 +67,11 @@ func newSignedHostServer(
 	}
 
 	h := &Handlers{
-		log:    log,
-		imgSvc: svc,
-		encGen: encGen,
+		log:       log,
+		imgSvc:    svc,
+		encGen:    encGen,
+		signer:    signature.New(testSigningKey),
+		allowlist: allowlist.New(nil),
 	}
 
 	r := chi.NewRouter()
@@ -202,8 +205,7 @@ func TestHandleImageEnc_MaxAge(t *testing.T) {
 					Size:   imagerequest.Size{Width: 50, Height: 50},
 					Format: imagerequest.FormatJPEG,
 				},
-				Expires: tt.expires,
-			})
+			}, tt.expires)
 			if err != nil {
 				t.Fatalf("Generate() error = %v", err)
 			}

internal/handlers/image_errors_internal_test.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/go-chi/chi/v5"
 	"github.com/prometheus/client_golang/prometheus"
+	"sneak.berlin/go/pixa/internal/allowlist"
 	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
 	"sneak.berlin/go/pixa/internal/imagerequest"
@@ -26,7 +27,7 @@ import (
 const allowlistedHost = "allowed.example.com"
 
 // newImageRoute returns the image route of a Handlers whose service fetches
-// with fetcher and checks signatures with testSigningKey.
+// with fetcher, and which checks signatures with testSigningKey.
 func newImageRoute(t *testing.T, fetcher httpfetcher.Fetcher) http.Handler {
 	t.Helper()
 
@@ -46,15 +47,18 @@ func newImageRoute(t *testing.T, fetcher httpfetcher.Fetcher) http.Handler {
 			MaxInputBytes:           50 << 20,
 			MaxConcurrentProcessing: 2,
 		}),
-		SigningKey:      testSigningKey,
-		Allowlist:       []string{allowlistedHost},
 		MaxResponseSize: 50 << 20,
 	})
 	if err != nil {
 		t.Fatalf("failed to create service: %v", err)
 	}
 
-	h := &Handlers{imgSvc: svc, log: slog.New(slog.DiscardHandler)}
+	h := &Handlers{
+		imgSvc:    svc,
+		log:       slog.New(slog.DiscardHandler),
+		signer:    signature.New(testSigningKey),
+		allowlist: allowlist.New([]string{allowlistedHost}),
+	}
 
 	r := chi.NewRouter()
 	r.Get("/v1/image/*", h.HandleImage())
@@ -63,7 +67,7 @@ func newImageRoute(t *testing.T, fetcher httpfetcher.Fetcher) http.Handler {
 }
 
 // newPhotoFetcher returns a mock fetcher that serves a JPEG at photoPath on
-// each of hosts, and answers any other URL with an upstream error.
+// each of hosts, and answers any other source with an upstream error.
 func newPhotoFetcher(t *testing.T, hosts ...string) *httpfetcher.MockFetcher {
 	t.Helper()
 
@@ -90,10 +94,10 @@ func photoURLWithSig(host, sig string, expires time.Time) string {
 	return fmt.Sprintf("%s?sig=%s&exp=%d", photoURL(host), sig, expires.Unix())
 }
 
-// photoSignature returns the signature of photoURL(host) at the default
-// quality and fit, made with key and expiring at expires.
-func photoSignature(key, host string, expires time.Time) string {
-	return signature.New(key).Sign(&imagerequest.Request{
+// photoRequest returns the image request of photoURL(host) at the default
+// quality and fit.
+func photoRequest(host string) *imagerequest.Request {
+	return &imagerequest.Request{
 		Source: imagerequest.Source{
 			Host: host,
 			Path: photoPath,
@@ -104,8 +108,13 @@ func photoSignature(key, host string, expires time.Time) string {
 			Quality: 85,
 			FitMode: imagerequest.FitCover,
 		},
-		Expires: expires,
-	})
+	}
+}
+
+// photoSignature returns the signature of photoURL(host) at the default
+// quality and fit, made with key and expiring at expires.
+func photoSignature(key, host string, expires time.Time) string {
+	return signature.New(key).Sign(photoRequest(host), expires)
 }
 
 // sendGet sends a GET for target to route and returns the response.
@@ -286,10 +295,9 @@ func TestHandleImage_AllowlistOrSignature(t *testing.T) {
 // host can be, and checks that each is refused with 400 naming the host as
 // decoded: allowlistedHost with a character after it that a URL host cannot
 // hold, percent-encoded, an IPv6 address without brackets, and brackets
-// around something that is not an IPv6 address. A "?" or "#" after
-// allowlistedHost would otherwise end the host when the source URL is read,
-// so the request would pass the allowlist and be fetched and cached under a
-// host that is not the one fetched.
+// around something that is not an IPv6 address. Later steps put the host
+// unparsed into the allowlist check, the cache key and the upstream URL, so
+// such a host is refused first.
 func TestHandleImage_InvalidHost_Returns400(t *testing.T) {
 	t.Parallel()
 
@@ -360,10 +368,9 @@ func TestHandleImage_HostForms_Served(t *testing.T) {
 
 // TestHandleImage_HashInSourcePathOrQuery_Returns400 sends image URLs whose
 // source path or source query holds a "#", written as %23, and checks that
-// each is refused with 400, the one signed for that source path included. The
-// source URL would otherwise end at the "#" when it is fetched, so each text
-// after it would fetch the image at photoPath and cache it under keys of its
-// own.
+// each is refused with 400, the one signed for that source path included.
+// A "#" starts a URL's fragment, so neither the source path nor the source
+// query may hold one.
 func TestHandleImage_HashInSourcePathOrQuery_Returns400(t *testing.T) {
 	t.Parallel()
 
@@ -381,8 +388,7 @@ func TestHandleImage_HashInSourcePathOrQuery_Returns400(t *testing.T) {
 			Quality: 85,
 			FitMode: imagerequest.FitCover,
 		},
-		Expires: exp,
-	})
+	}, exp)
 
 	tests := []struct {
 		name   string

internal/handlers/image_signature_internal_test.go

@@ -38,40 +38,44 @@ func getImage(t *testing.T, fix *testFixtures, target string) int {
 }
 
 // generateSignedURL returns the /v1/image/ URL of req, signed with key and
-// expiring after ttl, and sets req's expiry. An unset quality or fit of req is
-// first set to 85 or cover, the values the route uses when a URL has no q or
-// fit. The URL carries q and fit next to sig and exp, so the route verifies it
-// for the quality and fit it was signed with.
+// expiring after ttl. It signs a copy of req, so req itself is not changed.
+// An unset quality or fit in the copy is set to 85 or cover, the values the
+// route uses when a URL has no q or fit. The URL carries q and fit next to sig
+// and exp, so the route verifies it for the quality and fit it was signed
+// with.
 func generateSignedURL(
 	key string, req *imagerequest.Request, ttl time.Duration,
 ) string {
-	if req.Transform.Quality == 0 {
-		req.Transform.Quality = 85
+	signed := *req
+
+	if signed.Transform.Quality == 0 {
+		signed.Transform.Quality = 85
 	}
 
-	if req.Transform.FitMode == "" {
-		req.Transform.FitMode = imagerequest.FitCover
+	if signed.Transform.FitMode == "" {
+		signed.Transform.FitMode = imagerequest.FitCover
 	}
 
-	req.Expires = time.Now().Add(ttl)
-	sig := signature.New(key).Sign(req)
+	expires := time.Now().Add(ttl)
+	sig := signature.New(key).Sign(&signed, expires)
 
 	// A source query follows the source path after a "?". The image route
 	// reads the path decoded once, so the whole path is written in Go's own
 	// percent-encoding of a URL path, which writes "?" as %3F and "%" as %25,
 	// and leaves "/", ";", ",", "=" and "&" as they are.
-	sourcePathAndQuery := req.Source.Path
-	if req.Source.Query != "" {
-		sourcePathAndQuery += "?" + req.Source.Query
+	sourcePathAndQuery := signed.Source.Path
+	if signed.Source.Query != "" {
+		sourcePathAndQuery += "?" + signed.Source.Query
 	}
 
 	unescapedPath := fmt.Sprintf("/v1/image/%s%s/%dx%d.%s",
-		req.Source.Host, sourcePathAndQuery,
-		req.Transform.Size.Width, req.Transform.Size.Height, req.Transform.Format)
+		signed.Source.Host, sourcePathAndQuery,
+		signed.Transform.Size.Width, signed.Transform.Size.Height,
+		signed.Transform.Format)
 
 	return fmt.Sprintf("%s?sig=%s&exp=%d&q=%d&fit=%s",
-		(&url.URL{Path: unescapedPath}).EscapedPath(), sig, req.Expires.Unix(),
-		req.Transform.Quality, req.Transform.FitMode)
+		(&url.URL{Path: unescapedPath}).EscapedPath(), sig, expires.Unix(),
+		signed.Transform.Quality, signed.Transform.FitMode)
 }
 
 // TestHandleImage_SignatureCoversQualityAndFit signs a URL for quality 85
@@ -93,8 +97,7 @@ func TestHandleImage_SignatureCoversQualityAndFit(t *testing.T) {
 			Quality: 85,
 			FitMode: imagerequest.FitCover,
 		},
-		Expires: expires,
-	})
+	}, expires)
 	signedURL := fmt.Sprintf("/v1/image/%s/images/photo.jpg/50x50.jpeg?sig=%s&exp=%d",
 		signedHost, sig, expires.Unix())
 
@@ -277,8 +280,7 @@ func TestHandleImage_SourceQueryEncodedAnyWay(t *testing.T) {
 			Quality: 85,
 			FitMode: imagerequest.FitCover,
 		},
-		Expires: expires,
-	})
+	}, expires)
 
 	tests := []struct {
 		name         string
@@ -344,8 +346,7 @@ func TestHandleImage_SourceURLHoldingPercent25Verifies(t *testing.T) {
 					Quality: 85,
 					FitMode: imagerequest.FitCover,
 				},
-				Expires: expires,
-			})
+			}, expires)
 
 			target := fmt.Sprintf("/v1/image/%s%s/50x50.jpeg?sig=%s&exp=%d",
 				signedHost, tt.writtenPathAndQuery, sig, expires.Unix())

internal/handlers/imageenc.go

@@ -31,11 +31,18 @@ func (s *Handlers) HandleImageEnc() http.HandlerFunc {
 		ctx := r.Context()
 		start := time.Now()
 
-		req, ok := s.parseImageEncRequest(w, r)
-		if !ok || !s.chooseAutoFormat(w, r, req) {
+		req, expires, ok := s.parseImageEncRequest(w, r)
+		if !ok {
 			return
 		}
 
+		format, ok := s.chooseAutoFormat(w, r, req.Transform.Format)
+		if !ok {
+			return
+		}
+
+		req.Transform.Format = format
+
 		// Log the request
 		s.log.Debug("encrypted image request",
 			"host", req.Source.Host,
@@ -64,7 +71,7 @@ func (s *Handlers) HandleImageEnc() http.HandlerFunc {
 		}
 
 		// Cache headers: max-age ends at the URL's expiry
-		w.Header().Set("Cache-Control", cacheControl(req.Expires))
+		w.Header().Set("Cache-Control", cacheControl(expires))
 		w.Header().Set("X-Pixa-Cache", string(resp.CacheStatus))
 
 		if notModified(w, r, resp.ETag) {
@@ -102,34 +109,34 @@ func (s *Handlers) HandleImageEnc() http.HandlerFunc {
 }
 
 // parseImageEncRequest decrypts the token of an encrypted image URL into an
-// image request and checks it. On a token that is missing, does not decrypt,
-// has expired or asks for something not valid, it writes an error response
-// and returns false.
+// image request and checks it, and returns it with the token's expiry. On a
+// token that is missing, does not decrypt, has expired or asks for something
+// not valid, it writes an error response and returns false.
 func (s *Handlers) parseImageEncRequest(
 	w http.ResponseWriter, r *http.Request,
-) (*imagerequest.Request, bool) {
+) (*imagerequest.Request, time.Time, bool) {
 	// Extract token from URL
 	token := chi.URLParam(r, "token")
 	if token == "" {
 		s.respondError(w, "missing token", http.StatusBadRequest)
 
-		return nil, false
+		return nil, time.Time{}, false
 	}
 
 	// Decrypt and validate the payload
-	req, err := s.encGen.Parse(token)
+	req, expires, err := s.encGen.Parse(token)
 	if err != nil {
 		if errors.Is(err, encurl.ErrExpired) {
 			s.log.Debug("encrypted URL expired", "error", err)
 			s.respondError(w, "URL has expired", http.StatusGone)
 
-			return nil, false
+			return nil, time.Time{}, false
 		}
 
 		s.log.Debug("failed to decrypt URL", "error", err)
 		s.respondError(w, "invalid encrypted URL", http.StatusBadRequest)
 
-		return nil, false
+		return nil, time.Time{}, false
 	}
 
 	// Apply the same dimension and fit-mode bounds as the plain image
@@ -142,10 +149,10 @@ func (s *Handlers) parseImageEncRequest(
 		s.respondError(w, "invalid encrypted URL: "+err.Error(),
 			http.StatusBadRequest)
 
-		return nil, false
+		return nil, time.Time{}, false
 	}
 
-	return req, true
+	return req, expires, true
 }
 
 // handleImageError converts image service errors to HTTP responses.

internal/handlers/imageenc_internal_test.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"testing"
+	"time"
 
 	"github.com/go-chi/chi/v5"
 
@@ -62,7 +63,7 @@ func TestHandleImageEnc_OverLimitDimension_Returns400(t *testing.T) {
 		Transform: imagerequest.Transform{
 			Size: imagerequest.Size{Width: 100000, Height: 100000},
 		},
-	})
+	}, time.Time{})
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}
@@ -91,7 +92,7 @@ func TestHandleImageEnc_InvalidFitMode_Returns400(t *testing.T) {
 			Size:    imagerequest.Size{Width: 800, Height: 600},
 			FitMode: imagerequest.Fit("bogus"),
 		},
-	})
+	}, time.Time{})
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}

internal/handlers/imageenc_token_internal_test.go

@@ -70,15 +70,12 @@ func TestHandleImageEnc_RejectedToken(t *testing.T) {
 		},
 	}
 
-	valid, err := h.encGen.Generate(&photo)
+	valid, err := h.encGen.Generate(&photo, time.Time{})
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}
 
-	expiredPhoto := photo
-	expiredPhoto.Expires = time.Now().Add(-time.Minute)
-
-	expired, err := h.encGen.Generate(&expiredPhoto)
+	expired, err := h.encGen.Generate(&photo, time.Now().Add(-time.Minute))
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}
@@ -88,7 +85,7 @@ func TestHandleImageEnc_RejectedToken(t *testing.T) {
 		t.Fatalf("encurl.NewGenerator() error = %v", err)
 	}
 
-	otherKey, err := otherGen.Generate(&photo)
+	otherKey, err := otherGen.Generate(&photo, time.Time{})
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}

internal/handlers/jpegxl_default_internal_test.go

@@ -69,8 +69,7 @@ func TestImageWithoutFormat_SignedAsJXL(t *testing.T) {
 			Quality: encurl.DefaultQuality,
 			FitMode: imagerequest.FitCover,
 		},
-		Expires: expires,
-	})
+	}, expires)
 	query := fmt.Sprintf("?sig=%s&exp=%d", sig, expires.Unix())
 
 	for _, size := range []string{"50x50.jxl", "50x50"} {
@@ -94,7 +93,7 @@ func TestImageEncWithoutFormat_ServesJPEGXL(t *testing.T) {
 		Transform: imagerequest.Transform{
 			Size: imagerequest.Size{Width: 50, Height: 50},
 		},
-	})
+	}, time.Time{})
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}

internal/handlers/referer_blocklist_internal_test.go

@@ -15,7 +15,9 @@ import (
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
+	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/imgcache"
+	"sneak.berlin/go/pixa/internal/signature"
 )
 
 // blockedReferer is a page on leech.example, which newRefererRoutes puts on
@@ -31,11 +33,11 @@ type countingFetcher struct {
 
 // Fetch counts the fetch and passes it on.
 func (f *countingFetcher) Fetch(
-	ctx context.Context, url string,
+	ctx context.Context, source imagerequest.Source,
 ) (*httpfetcher.FetchResult, error) {
 	f.fetches.Add(1)
 
-	return f.Fetcher.Fetch(ctx, url)
+	return f.Fetcher.Fetch(ctx, source)
 }
 
 // newRefererRoutes returns both image routes of a Handlers whose
@@ -65,8 +67,6 @@ func newRefererRoutes(t *testing.T) (http.Handler, *Handlers, *countingFetcher)
 			MaxInputBytes:           50 << 20,
 			MaxConcurrentProcessing: 2,
 		}),
-		SigningKey:      testSigningKey,
-		Allowlist:       []string{allowlistedHost},
 		MaxResponseSize: 50 << 20,
 	})
 	if err != nil {
@@ -79,9 +79,11 @@ func newRefererRoutes(t *testing.T) (http.Handler, *Handlers, *countingFetcher)
 	}
 
 	h := &Handlers{
-		log:    slog.New(slog.DiscardHandler),
-		imgSvc: svc,
-		encGen: encGen,
+		log:       slog.New(slog.DiscardHandler),
+		imgSvc:    svc,
+		encGen:    encGen,
+		signer:    signature.New(testSigningKey),
+		allowlist: allowlist.New([]string{allowlistedHost}),
 		refererBlocklist: allowlist.New(
 			[]string{"leech.example", ".hotlinker.example"}),
 	}

internal/handlers/request_id_internal_test.go

@@ -18,8 +18,8 @@ import (
 
 // signedPhotoURL returns a signed /v1/image/ URL, valid for a minute, for the
 // JPEG at photoPath on signedHost at 50x50. It is signed with testSigningKey,
-// the key of the image service newSignedHostServer builds. It takes a Handlers
-// it does not use, so that it has the type of encPhotoURL.
+// the key the handlers that newSignedHostServer builds check signatures with.
+// It takes a Handlers it does not use, so that it has the type of encPhotoURL.
 func signedPhotoURL(t *testing.T, _ *Handlers) string {
 	t.Helper()
 
@@ -49,7 +49,7 @@ func encPhotoURL(t *testing.T, h *Handlers) string {
 			Size:   imagerequest.Size{Width: 50, Height: 50},
 			Format: imagerequest.FormatJPEG,
 		},
-	})
+	}, time.Time{})
 	if err != nil {
 		t.Fatalf("Generate() error = %v", err)
 	}

internal/handlers/validate_signature_internal_test.go

@@ -0,0 +1,211 @@
+package handlers
+
+import (
+	"testing"
+	"time"
+
+	"sneak.berlin/go/pixa/internal/allowlist"
+	"sneak.berlin/go/pixa/internal/signature"
+)
+
+// Addresses the port tests below put on the allowlist.
+const (
+	allowlistedIPv4 = "203.0.113.5"
+	allowlistedIPv6 = "2001:db8::1"
+)
+
+// newSignatureChecker returns Handlers that check signatures with
+// testSigningKey and have allowlistHosts on their allowlist, as New builds
+// them from signing_key and allowlist_hosts.
+func newSignatureChecker(allowlistHosts ...string) *Handlers {
+	return &Handlers{
+		signer:    signature.New(testSigningKey),
+		allowlist: allowlist.New(allowlistHosts),
+	}
+}
+
+func TestValidateSignature_NonAllowlistedHost_NoSignature(t *testing.T) {
+	t.Parallel()
+
+	h := newSignatureChecker(allowlistedHost)
+
+	// Should fail validation - not allowlisted and no signature
+	err := h.validateSignature(photoRequest(signedHost), "", time.Time{})
+	if err == nil {
+		t.Error("validateSignature() expected error for non-allowlisted " +
+			"host without signature")
+	}
+}
+
+func TestValidateSignature_NonAllowlistedHost_ValidSignature(t *testing.T) {
+	t.Parallel()
+
+	h := newSignatureChecker(allowlistedHost)
+	req := photoRequest(signedHost)
+
+	// Generate a valid signature
+	expires := time.Now().Add(time.Hour)
+	sig := signature.New(testSigningKey).Sign(req, expires)
+
+	// Should pass validation
+	err := h.validateSignature(req, sig, expires)
+	if err != nil {
+		t.Errorf("validateSignature() error = %v", err)
+	}
+}
+
+func TestValidateSignature_NonAllowlistedHost_ExpiredSignature(t *testing.T) {
+	t.Parallel()
+
+	h := newSignatureChecker(allowlistedHost)
+	req := photoRequest(signedHost)
+
+	// Generate an expired signature
+	expires := time.Now().Add(-time.Hour)
+	sig := signature.New(testSigningKey).Sign(req, expires)
+
+	// Should fail validation
+	err := h.validateSignature(req, sig, expires)
+	if err == nil {
+		t.Error("validateSignature() expected error for expired signature")
+	}
+}
+
+func TestValidateSignature_NonAllowlistedHost_InvalidSignature(t *testing.T) {
+	t.Parallel()
+
+	h := newSignatureChecker(allowlistedHost)
+
+	// Should fail validation
+	err := h.validateSignature(photoRequest(signedHost), "invalid-signature",
+		time.Now().Add(time.Hour))
+	if err == nil {
+		t.Error("validateSignature() expected error for invalid signature")
+	}
+}
+
+// TestValidateSignature_NoAllowlist checks that with no host on the
+// allowlist, a request without a signature fails validation.
+func TestValidateSignature_NoAllowlist(t *testing.T) {
+	t.Parallel()
+
+	h := newSignatureChecker()
+
+	err := h.validateSignature(photoRequest(signedHost), "", time.Time{})
+	if err == nil {
+		t.Error("validateSignature() expected error when no host is allowlisted")
+	}
+}
+
+// TestValidateSignature_SignatureExactHostMatch verifies that
+// validateSignature enforces exact host matching for signatures. A
+// signature for one host must not verify for a different host, even
+// if they share a domain suffix.
+func TestValidateSignature_SignatureExactHostMatch(t *testing.T) {
+	t.Parallel()
+
+	h := newSignatureChecker()
+
+	// Sign a request for signedHost
+	signedReq := photoRequest(signedHost)
+	expires := time.Now().Add(time.Hour)
+	sig := signature.New(testSigningKey).Sign(signedReq, expires)
+
+	// The original request should pass validation
+	t.Run("exact host passes", func(t *testing.T) {
+		t.Parallel()
+
+		err := h.validateSignature(signedReq, sig, expires)
+		if err != nil {
+			t.Errorf("validateSignature() exact host failed: %v", err)
+		}
+	})
+
+	// Try to reuse the signature with different hosts
+	tests := []struct {
+		name string
+		host string
+	}{
+		{"parent domain", "example.com"},
+		{"sibling subdomain", "images.example.com"},
+		{"deeper subdomain", "a." + signedHost},
+		{"evil suffix domain", signedHost + ".evil.com"},
+		{"prefixed host", "evil" + signedHost},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name+" rejected", func(t *testing.T) {
+			t.Parallel()
+
+			err := h.validateSignature(photoRequest(tt.host), sig, expires)
+			if err == nil {
+				t.Errorf("validateSignature() should reject signature for "+
+					"host %q (signed for %q)", tt.host, signedHost)
+			}
+		})
+	}
+}
+
+// TestValidateSignature_HostWithPortNeedsSignature verifies that a host
+// followed by a port, or by a colon with no port, matches no allowlist entry,
+// so that a request for it without a signature is refused, while the same
+// host with no port is allowlisted.
+func TestValidateSignature_HostWithPortNeedsSignature(t *testing.T) {
+	t.Parallel()
+
+	h := newSignatureChecker(allowlistedHost, allowlistedIPv4, allowlistedIPv6)
+
+	tests := []struct {
+		host        string
+		allowlisted bool
+	}{
+		{allowlistedHost, true},
+		{allowlistedHost + ":8443", false},
+		{allowlistedHost + ":443", false},
+		{allowlistedHost + ":", false},
+		{allowlistedIPv4, true},
+		{allowlistedIPv4 + ":8080", false},
+		{"[" + allowlistedIPv6 + "]", true},
+		{"[" + allowlistedIPv6 + "]:8443", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.host, func(t *testing.T) {
+			t.Parallel()
+
+			err := h.validateSignature(photoRequest(tt.host), "", time.Time{})
+			t.Logf("validateSignature() for host %q with no signature: %v",
+				tt.host, err)
+
+			if allowlisted := err == nil; allowlisted != tt.allowlisted {
+				t.Errorf("host %q served without a signature = %v, want %v",
+					tt.host, allowlisted, tt.allowlisted)
+			}
+		})
+	}
+}
+
+// TestValidateSignature_UnbracketedIPv6PortNeedsSignature verifies that an
+// allowlisted IPv6 address written without brackets and followed by a port,
+// or by a colon with no port, needs a signature. Go's URL type reads
+// 2001:db8::1:8443 as the host 2001:db8::1 with the port 8443.
+func TestValidateSignature_UnbracketedIPv6PortNeedsSignature(t *testing.T) {
+	t.Parallel()
+
+	h := newSignatureChecker(allowlistedIPv6)
+
+	for _, host := range []string{allowlistedIPv6 + ":8443", allowlistedIPv6 + ":"} {
+		t.Run(host, func(t *testing.T) {
+			t.Parallel()
+
+			err := h.validateSignature(photoRequest(host), "", time.Time{})
+			t.Logf("validateSignature() for host %q with no signature: %v",
+				host, err)
+
+			if err == nil {
+				t.Errorf("host %q served without a signature, want refused",
+					host)
+			}
+		})
+	}
+}

internal/httpfetcher/dial_context_internal_test.go

@@ -51,12 +51,12 @@ func TestDialContextReplacesOnlyTheDialer(t *testing.T) {
 		t.Errorf("body = %q, want %q", body, imagePayload)
 	}
 
-	_, err := f.Fetch(testContext(t), "http://127.0.0.1/image")
+	_, err := f.Fetch(testContext(t), imageSourceOn("127.0.0.1"))
 	if !errors.Is(err, ErrSSRFBlocked) {
 		t.Errorf("Fetch(loopback URL) error = %v, want ErrSSRFBlocked", err)
 	}
 
-	_, err = f.Fetch(testContext(t), upstreamURL("/redirect/private"))
+	_, err = f.Fetch(testContext(t), upstreamSource("/redirect/private"))
 	if !errors.Is(err, ErrSSRFBlocked) {
 		t.Errorf("Fetch(/redirect/private) error = %v, want ErrSSRFBlocked", err)
 	}

internal/httpfetcher/fetch_internal_test.go

@@ -14,6 +14,8 @@ import (
 	"sync"
 	"testing"
 	"time"
+
+	"sneak.berlin/go/pixa/internal/imagerequest"
 )
 
 // testPublicHost is a TEST-NET-1 (RFC 5737) literal. isPrivateIP treats it as
@@ -29,9 +31,9 @@ const imagePayload = "fake-jpeg-bytes"
 // would mean SSRF protection let a forbidden target reach the transport.
 var errUnexpectedDial = errors.New("unexpected dial target")
 
-// upstreamURL builds a fetch URL on the fake public host for the given path.
-func upstreamURL(path string) string {
-	return "http://" + testPublicHost + path
+// upstreamSource returns the source at path on the fake public host.
+func upstreamSource(path string) imagerequest.Source {
+	return imagerequest.Source{Host: testPublicHost, Path: path}
 }
 
 // recordingDialer records every address the transport asks it to dial and
@@ -158,7 +160,7 @@ func testContext(t *testing.T) context.Context {
 func fetchImage(t *testing.T, f *HTTPFetcher, path string) *FetchResult {
 	t.Helper()
 
-	res, err := f.Fetch(testContext(t), upstreamURL(path))
+	res, err := f.Fetch(testContext(t), upstreamSource(path))
 	if err != nil {
 		t.Fatalf("Fetch(%s) error = %v", path, err)
 	}
@@ -170,7 +172,7 @@ func fetchImage(t *testing.T, f *HTTPFetcher, path string) *FetchResult {
 func fetchExpectError(t *testing.T, f *HTTPFetcher, path string) error {
 	t.Helper()
 
-	res, err := f.Fetch(testContext(t), upstreamURL(path))
+	res, err := f.Fetch(testContext(t), upstreamSource(path))
 	if err == nil {
 		_ = res.Content.Close()
 
@@ -222,7 +224,7 @@ func TestFetchRedirectToPrivateIPBlocked(t *testing.T) {
 	srv := startUpstream(t)
 	f, dialer := newServerFetcher(t, srv, nil)
 
-	_, err := f.Fetch(testContext(t), upstreamURL("/redirect/private"))
+	_, err := f.Fetch(testContext(t), upstreamSource("/redirect/private"))
 	if !errors.Is(err, ErrSSRFBlocked) {
 		t.Fatalf("Fetch() error = %v, want ErrSSRFBlocked", err)
 	}
@@ -590,3 +592,53 @@ func TestSSRFSafeDialerAllowsPublicTarget(t *testing.T) {
 		t.Errorf("public target was SSRF-blocked: %v", err)
 	}
 }
+
+// TestFetchSchemeFollowsAllowHTTP checks that the fetcher fetches a source
+// over https, on port 443, unless AllowHTTP is set, and then over http, on
+// port 80. The test server speaks plain HTTP, so only the fetch over http
+// succeeds.
+func TestFetchSchemeFollowsAllowHTTP(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		allowHTTP bool
+		wantAddr  string
+	}{
+		{false, net.JoinHostPort(testPublicHost, "443")},
+		{true, net.JoinHostPort(testPublicHost, "80")},
+	}
+
+	for _, tt := range tests {
+		t.Run(fmt.Sprintf("AllowHTTP %v", tt.allowHTTP), func(t *testing.T) {
+			t.Parallel()
+
+			srv := startUpstream(t)
+			dialer := &recordingDialer{target: srv.Listener.Addr().String()}
+
+			f := New(&Config{
+				Timeout:               30 * time.Second,
+				MaxResponseSize:       50 << 20,
+				AllowHTTP:             tt.allowHTTP,
+				MaxConnectionsPerHost: 20,
+				MaxConnections:        64,
+				DialContext:           dialer.dialContext,
+			})
+
+			res, err := f.Fetch(testContext(t), upstreamSource("/image"))
+			if err == nil {
+				_ = res.Content.Close()
+			}
+
+			dialed := dialer.dialedAddrs()
+			t.Logf("Fetch(): error %v, dialed %v", err, dialed)
+
+			if served := err == nil; served != tt.allowHTTP {
+				t.Errorf("served = %v, want %v", served, tt.allowHTTP)
+			}
+
+			if len(dialed) != 1 || dialed[0] != tt.wantAddr {
+				t.Errorf("dialed %v, want only %s", dialed, tt.wantAddr)
+			}
+		})
+	}
+}

internal/httpfetcher/httpfetcher.go

@@ -20,6 +20,7 @@ import (
 	"time"
 
 	"github.com/go-chi/chi/v5/middleware"
+	"sneak.berlin/go/pixa/internal/imagerequest"
 )
 
 // Fetcher configuration constants.
@@ -91,8 +92,8 @@ var (
 
 // Fetcher retrieves content from upstream origins.
 type Fetcher interface {
-	// Fetch retrieves content from the given URL.
-	Fetch(ctx context.Context, url string) (*FetchResult, error)
+	// Fetch retrieves the content of the source image.
+	Fetch(ctx context.Context, source imagerequest.Source) (*FetchResult, error)
 }
 
 // FetchResult contains the result of fetching from upstream.
@@ -139,7 +140,8 @@ type Config struct {
 	Timeout time.Duration
 	// MaxResponseSize is the maximum allowed response body size.
 	MaxResponseSize int64
-	// AllowHTTP allows non-TLS connections (for testing only).
+	// AllowHTTP makes the fetcher fetch sources over http instead of https,
+	// and follow redirects to http (for testing only).
 	AllowHTTP bool
 	// MaxConnectionsPerHost limits concurrent connections to each upstream host.
 	MaxConnectionsPerHost int
@@ -211,7 +213,7 @@ func New(config *Config) *HTTPFetcher {
 			}
 
 			// Validate the redirect target
-			err := validateURL(req.Context(), req.URL.String(), config.AllowHTTP)
+			err := validateURL(req.Context(), req.URL, config.AllowHTTP)
 			if err != nil {
 				return fmt.Errorf("redirect blocked: %w", err)
 			}
@@ -229,18 +231,22 @@ func New(config *Config) *HTTPFetcher {
 	}
 }
 
-// Fetch retrieves content from the given URL with SSRF protection. When
-// MaxConnections fetches are already in progress, it waits up to
-// ConnectionWaitTimeout for one to finish, then fails with
-// ErrTooManyConnections.
-func (f *HTTPFetcher) Fetch(ctx context.Context, url string) (*FetchResult, error) {
+// Fetch retrieves the source image with SSRF protection, over https, or over
+// http when AllowHTTP is set. When MaxConnections fetches are already in
+// progress, it waits up to ConnectionWaitTimeout for one to finish, then
+// fails with ErrTooManyConnections.
+func (f *HTTPFetcher) Fetch(
+	ctx context.Context, source imagerequest.Source,
+) (*FetchResult, error) {
+	sourceURL := source.URL(f.config.AllowHTTP)
+
 	// Validate URL before making request
-	err := validateURL(ctx, url, f.config.AllowHTTP)
+	err := validateURL(ctx, sourceURL, f.config.AllowHTTP)
 	if err != nil {
 		return nil, err
 	}
 
-	release, err := f.acquireConnection(ctx, extractHost(url))
+	release, err := f.acquireConnection(ctx, source.Host)
 	if err != nil {
 		return nil, err
 	}
@@ -254,14 +260,9 @@ func (f *HTTPFetcher) Fetch(ctx context.Context, url string) (*FetchResult, erro
 		}
 	}()
 
-	parsedURL, err := neturl.Parse(url)
-	if err != nil {
-		return nil, fmt.Errorf("failed to parse URL: %w", err)
-	}
-
 	req := &http.Request{
 		Method: http.MethodGet,
-		URL:    parsedURL,
+		URL:    sourceURL,
 		Header: make(http.Header),
 	}
 
@@ -455,19 +456,14 @@ func (f *HTTPFetcher) isAllowedContentType(contentType string) bool {
 }
 
 // validateURL checks if a URL is safe to fetch (not internal/private).
-func validateURL(ctx context.Context, rawURL string, allowHTTP bool) error {
-	if !allowHTTP && !strings.HasPrefix(rawURL, "https://") {
+func validateURL(ctx context.Context, fetchURL *neturl.URL, allowHTTP bool) error {
+	if !allowHTTP && fetchURL.Scheme != "https" {
 		return ErrUnsupportedScheme
 	}
 
-	parsedURL, err := neturl.Parse(rawURL)
-	if err != nil {
-		return fmt.Errorf("%w: %w", ErrInvalidHost, err)
-	}
-
 	// Hostname drops any port, and the brackets of an IPv6 address whether
 	// or not a port follows them
-	host := parsedURL.Hostname()
+	host := fetchURL.Hostname()
 	if host == "" {
 		return ErrInvalidHost
 	}
@@ -493,25 +489,6 @@ func validateURL(ctx context.Context, rawURL string, allowHTTP bool) error {
 	return nil
 }
 
-// extractHost extracts the host from a URL string.
-func extractHost(rawURL string) string {
-	// Simple extraction without full URL parsing
-	url := rawURL
-	if idx := strings.Index(url, "://"); idx != -1 {
-		url = url[idx+3:]
-	}
-
-	if idx := strings.Index(url, "/"); idx != -1 {
-		url = url[:idx]
-	}
-
-	if idx := strings.Index(url, "?"); idx != -1 {
-		url = url[:idx]
-	}
-
-	return url
-}
-
 // isLocalhost checks if the host is localhost.
 func isLocalhost(host string) bool {
 	host = strings.ToLower(host)

internal/httpfetcher/httpfetcher_internal_test.go

@@ -5,9 +5,12 @@ import (
 	"errors"
 	"io"
 	"net"
+	"net/url"
 	"testing"
 	"testing/fstest"
 	"time"
+
+	"sneak.berlin/go/pixa/internal/imagerequest"
 )
 
 // testHost is the hostname used by mock fetch tests.
@@ -49,33 +52,6 @@ func TestIsAllowedContentType(t *testing.T) {
 	}
 }
 
-func TestExtractHost(t *testing.T) {
-	t.Parallel()
-
-	tests := []struct {
-		url  string
-		want string
-	}{
-		{"https://example.com/path", testHost},
-		{"http://example.com:8080/path", "example.com:8080"},
-		{"https://example.com", testHost},
-		{"https://example.com?q=1", testHost},
-		{"example.com/path", testHost},
-		{"", ""},
-	}
-
-	for _, tc := range tests {
-		t.Run(tc.url, func(t *testing.T) {
-			t.Parallel()
-
-			got := extractHost(tc.url)
-			if got != tc.want {
-				t.Errorf("extractHost(%q) = %q, want %q", tc.url, got, tc.want)
-			}
-		})
-	}
-}
-
 func TestIsLocalhost(t *testing.T) {
 	t.Parallel()
 
@@ -188,7 +164,7 @@ func TestIsPrivateIPJudgesEmbeddedIPv4Address(t *testing.T) {
 func TestValidateURL_RejectsNonHTTPS(t *testing.T) {
 	t.Parallel()
 
-	err := validateURL(t.Context(), "http://example.com/path", false)
+	err := validateURL(t.Context(), &url.URL{Scheme: "http", Host: testHost}, false)
 	if !errors.Is(err, ErrUnsupportedScheme) {
 		t.Errorf("validateURL http = %v, want ErrUnsupportedScheme", err)
 	}
@@ -198,7 +174,8 @@ func TestValidateURL_AllowsHTTPWhenConfigured(t *testing.T) {
 	t.Parallel()
 
 	// Use a host that won't resolve (explicit .invalid TLD) so we don't hit DNS.
-	err := validateURL(t.Context(), "http://nonexistent.invalid/path", true)
+	err := validateURL(t.Context(),
+		&url.URL{Scheme: "http", Host: "nonexistent.invalid"}, true)
 	// We expect a host resolution error, not ErrUnsupportedScheme.
 	if errors.Is(err, ErrUnsupportedScheme) {
 		t.Error("validateURL with AllowHTTP should not return ErrUnsupportedScheme")
@@ -208,7 +185,7 @@ func TestValidateURL_AllowsHTTPWhenConfigured(t *testing.T) {
 func TestValidateURL_RejectsLocalhost(t *testing.T) {
 	t.Parallel()
 
-	err := validateURL(t.Context(), "https://localhost/path", false)
+	err := validateURL(t.Context(), &url.URL{Scheme: "https", Host: "localhost"}, false)
 	if !errors.Is(err, ErrSSRFBlocked) {
 		t.Errorf("validateURL localhost = %v, want ErrSSRFBlocked", err)
 	}
@@ -217,7 +194,7 @@ func TestValidateURL_RejectsLocalhost(t *testing.T) {
 func TestValidateURL_EmptyHost(t *testing.T) {
 	t.Parallel()
 
-	err := validateURL(t.Context(), "https:///path", false)
+	err := validateURL(t.Context(), &url.URL{Scheme: "https"}, false)
 	if !errors.Is(err, ErrInvalidHost) {
 		t.Errorf("validateURL empty host = %v, want ErrInvalidHost", err)
 	}
@@ -232,7 +209,8 @@ func TestMockFetcher_FetchesFile(t *testing.T) {
 
 	m := NewMock(mockFS)
 
-	result, err := m.Fetch(context.Background(), "https://example.com/images/photo.jpg")
+	result, err := m.Fetch(context.Background(),
+		imagerequest.Source{Host: testHost, Path: "/images/photo.jpg"})
 	if err != nil {
 		t.Fatalf("Fetch() error = %v", err)
 	}
@@ -263,7 +241,8 @@ func TestMockFetcher_MissingFileReturnsUpstreamError(t *testing.T) {
 	mockFS := fstest.MapFS{}
 	m := NewMock(mockFS)
 
-	_, err := m.Fetch(context.Background(), "https://example.com/missing.jpg")
+	_, err := m.Fetch(context.Background(),
+		imagerequest.Source{Host: testHost, Path: "/missing.jpg"})
 	if !errors.Is(err, ErrUpstreamError) {
 		t.Errorf("Fetch() error = %v, want ErrUpstreamError", err)
 	}
@@ -280,7 +259,7 @@ func TestMockFetcher_RespectsContextCancellation(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()
 
-	_, err := m.Fetch(ctx, "https://example.com/photo.jpg")
+	_, err := m.Fetch(ctx, imagerequest.Source{Host: testHost, Path: "/photo.jpg"})
 	if !errors.Is(err, context.Canceled) {
 		t.Errorf("Fetch() error = %v, want context.Canceled", err)
 	}

internal/httpfetcher/max_connections_internal_test.go

@@ -8,14 +8,20 @@ import (
 	"sync"
 	"testing"
 	"time"
+
+	"sneak.berlin/go/pixa/internal/imagerequest"
 )
 
-// imageURLOnPort is the fake upstream's image route on testPublicHost at
+// imageSourceOn is the fake upstream's image route on host.
+func imageSourceOn(host string) imagerequest.Source {
+	return imagerequest.Source{Host: host, Path: "/image"}
+}
+
+// imageSourceOnPort is the fake upstream's image route on testPublicHost at
 // port. Each port is a different host to the per-host limit, while the test
 // dialer sends every port to the one test server.
-func imageURLOnPort(port int) string {
-	return "http://" + net.JoinHostPort(testPublicHost, strconv.Itoa(port)) +
-		"/image"
+func imageSourceOnPort(port int) imagerequest.Source {
+	return imageSourceOn(net.JoinHostPort(testPublicHost, strconv.Itoa(port)))
 }
 
 // TestFetchLimitsConnectionsToAllHostsTogether checks that MaxConnections
@@ -39,12 +45,12 @@ func TestFetchLimitsConnectionsToAllHostsTogether(t *testing.T) {
 	f, _ := newServerFetcher(t, srv, cfg)
 	f.connectionWaitTimeout = 100 * time.Millisecond
 
-	first, err := f.Fetch(testContext(t), imageURLOnPort(81))
+	first, err := f.Fetch(testContext(t), imageSourceOnPort(81))
 	if err != nil {
 		t.Fatalf("first Fetch() error = %v", err)
 	}
 
-	second, err := f.Fetch(testContext(t), imageURLOnPort(82))
+	second, err := f.Fetch(testContext(t), imageSourceOnPort(82))
 	if err != nil {
 		t.Fatalf("second Fetch() error = %v", err)
 	}
@@ -53,7 +59,7 @@ func TestFetchLimitsConnectionsToAllHostsTogether(t *testing.T) {
 
 	start := time.Now()
 
-	_, err = f.Fetch(testContext(t), imageURLOnPort(83))
+	_, err = f.Fetch(testContext(t), imageSourceOnPort(83))
 	if !errors.Is(err, ErrTooManyConnections) {
 		t.Fatalf("third Fetch() error = %v, want ErrTooManyConnections", err)
 	}
@@ -72,7 +78,7 @@ func TestFetchLimitsConnectionsToAllHostsTogether(t *testing.T) {
 		t.Fatalf("close first body: %v", err)
 	}
 
-	third, err := f.Fetch(testContext(t), imageURLOnPort(83))
+	third, err := f.Fetch(testContext(t), imageSourceOnPort(83))
 	if err != nil {
 		t.Fatalf("Fetch() after a response was closed: error = %v", err)
 	}
@@ -99,7 +105,7 @@ func TestFetchFreesHostSlotWhenContextEndsWaitingForConnection(t *testing.T) {
 
 	f, _ := newServerFetcher(t, srv, cfg)
 
-	first, err := f.Fetch(testContext(t), imageURLOnPort(81))
+	first, err := f.Fetch(testContext(t), imageSourceOnPort(81))
 	if err != nil {
 		t.Fatalf("first Fetch() error = %v", err)
 	}
@@ -109,7 +115,7 @@ func TestFetchFreesHostSlotWhenContextEndsWaitingForConnection(t *testing.T) {
 	ctx, cancel := context.WithTimeout(t.Context(), 100*time.Millisecond)
 	defer cancel()
 
-	_, err = f.Fetch(ctx, imageURLOnPort(82))
+	_, err = f.Fetch(ctx, imageSourceOnPort(82))
 	if !errors.Is(err, context.DeadlineExceeded) {
 		t.Fatalf("second Fetch() error = %v, want context.DeadlineExceeded", err)
 	}
@@ -134,7 +140,7 @@ func TestFetchRemovesIdleHostSemaphores(t *testing.T) {
 
 	for i := range 100 {
 		wg.Go(func() {
-			res, err := f.Fetch(ctx, imageURLOnPort(1+i%50))
+			res, err := f.Fetch(ctx, imageSourceOnPort(1+i%50))
 			if err != nil {
 				t.Errorf("Fetch() error = %v", err)
 
@@ -173,12 +179,12 @@ func TestFetchRemovesHostSemaphoreWhenNoConnection(t *testing.T) {
 	f, _ := newServerFetcher(t, srv, cfg)
 	f.connectionWaitTimeout = 100 * time.Millisecond
 
-	open, err := f.Fetch(testContext(t), imageURLOnPort(81))
+	open, err := f.Fetch(testContext(t), imageSourceOnPort(81))
 	if err != nil {
 		t.Fatalf("first Fetch() error = %v", err)
 	}
 
-	_, err = f.Fetch(testContext(t), imageURLOnPort(82))
+	_, err = f.Fetch(testContext(t), imageSourceOnPort(82))
 	if !errors.Is(err, ErrTooManyConnections) {
 		t.Fatalf("Fetch() from another host: error = %v, "+
 			"want ErrTooManyConnections", err)
@@ -187,7 +193,7 @@ func TestFetchRemovesHostSemaphoreWhenNoConnection(t *testing.T) {
 	ctx, cancel := context.WithTimeout(t.Context(), 100*time.Millisecond)
 	defer cancel()
 
-	_, err = f.Fetch(ctx, imageURLOnPort(81))
+	_, err = f.Fetch(ctx, imageSourceOnPort(81))
 	if !errors.Is(err, context.DeadlineExceeded) {
 		t.Fatalf("Fetch() from the busy host: error = %v, "+
 			"want context.DeadlineExceeded", err)
@@ -199,7 +205,7 @@ func TestFetchRemovesHostSemaphoreWhenNoConnection(t *testing.T) {
 	ctx, cancel = context.WithTimeout(t.Context(), 100*time.Millisecond)
 	defer cancel()
 
-	_, err = f.Fetch(ctx, imageURLOnPort(83))
+	_, err = f.Fetch(ctx, imageSourceOnPort(83))
 	if !errors.Is(err, context.DeadlineExceeded) {
 		t.Fatalf("Fetch() from a host with nothing open: error = %v, "+
 			"want context.DeadlineExceeded", err)
@@ -222,15 +228,15 @@ func TestFetchReleasesConnectionOnError(t *testing.T) {
 	t.Parallel()
 
 	cases := []struct {
-		name string
-		url  string
-		want error
+		name   string
+		source imagerequest.Source
+		want   error
 	}{
-		{"upstream answers 500", upstreamURL("/status/500"), ErrUpstreamError},
-		{"upstream sends HTML", upstreamURL("/html"), ErrInvalidContentType},
+		{"upstream answers 500", upstreamSource("/status/500"), ErrUpstreamError},
+		{"upstream sends HTML", upstreamSource("/html"), ErrInvalidContentType},
 		// 198.51.100.7 (TEST-NET-2) passes the SSRF checks, and the test
 		// dialer refuses every host but testPublicHost.
-		{"connecting fails", "http://198.51.100.7/image", errUnexpectedDial},
+		{"connecting fails", imageSourceOn("198.51.100.7"), errUnexpectedDial},
 	}
 
 	for _, tc := range cases {
@@ -249,7 +255,7 @@ func TestFetchReleasesConnectionOnError(t *testing.T) {
 			f, _ := newServerFetcher(t, srv, cfg)
 			f.connectionWaitTimeout = 100 * time.Millisecond
 
-			_, err := f.Fetch(testContext(t), tc.url)
+			_, err := f.Fetch(testContext(t), tc.source)
 			if !errors.Is(err, tc.want) {
 				t.Fatalf("Fetch() error = %v, want %v", err, tc.want)
 			}

internal/httpfetcher/mock.go

@@ -7,14 +7,14 @@ import (
 	"io/fs"
 	"net/http"
 	"strings"
-)
 
-// errEmptyURLPath is returned when a mock URL has no usable path.
-var errEmptyURLPath = errors.New("empty URL path")
+	"sneak.berlin/go/pixa/internal/imagerequest"
+)
 
 // MockFetcher implements Fetcher using an embedded filesystem.
 // Files are organized as: hostname/path/to/file.ext
-// URLs like https://example.com/images/photo.jpg map to example.com/images/photo.jpg.
+// The source with host example.com and path /images/photo.jpg maps to
+// example.com/images/photo.jpg; the source query is ignored.
 type MockFetcher struct {
 	fs fs.FS
 }
@@ -24,8 +24,10 @@ func NewMock(fsys fs.FS) *MockFetcher {
 	return &MockFetcher{fs: fsys}
 }
 
-// Fetch retrieves content from the mock filesystem.
-func (m *MockFetcher) Fetch(ctx context.Context, url string) (*FetchResult, error) {
+// Fetch retrieves the source's content from the mock filesystem.
+func (m *MockFetcher) Fetch(
+	ctx context.Context, source imagerequest.Source,
+) (*FetchResult, error) {
 	// Check context cancellation
 	select {
 	case <-ctx.Done():
@@ -33,11 +35,7 @@ func (m *MockFetcher) Fetch(ctx context.Context, url string) (*FetchResult, erro
 	default:
 	}
 
-	// Parse URL to get filesystem path
-	path, err := urlToFSPath(url)
-	if err != nil {
-		return nil, err
-	}
+	path := source.Host + source.Path
 
 	// Open the file
 	f, err := m.fs.Open(path)
@@ -68,32 +66,6 @@ func (m *MockFetcher) Fetch(ctx context.Context, url string) (*FetchResult, erro
 	}, nil
 }
 
-// urlToFSPath converts a URL to a filesystem path.
-// https://example.com/images/photo.jpg -> example.com/images/photo.jpg
-func urlToFSPath(rawURL string) (string, error) {
-	// Strip scheme
-	url := rawURL
-	if idx := strings.Index(url, "://"); idx != -1 {
-		url = url[idx+3:]
-	}
-
-	// Remove query string
-	if idx := strings.Index(url, "?"); idx != -1 {
-		url = url[:idx]
-	}
-
-	// Remove fragment
-	if idx := strings.Index(url, "#"); idx != -1 {
-		url = url[:idx]
-	}
-
-	if url == "" {
-		return "", errEmptyURLPath
-	}
-
-	return url, nil
-}
-
 // detectContentTypeFromPath returns the MIME type based on file extension.
 func detectContentTypeFromPath(path string) string {
 	path = strings.ToLower(path)

internal/httpfetcher/request_id_internal_test.go

@@ -34,7 +34,7 @@ func TestFetchSendsRequestID(t *testing.T) {
 
 	ctx := context.WithValue(testContext(t), middleware.RequestIDKey, requestID)
 
-	res, err := f.Fetch(ctx, upstreamURL("/image"))
+	res, err := f.Fetch(ctx, upstreamSource("/image"))
 	if err != nil {
 		t.Fatalf("Fetch() error = %v", err)
 	}

internal/imagerequest/imagerequest.go

@@ -1,13 +1,12 @@
 // Package imagerequest holds the image request type, its parts, its checks,
-// the parsing of the /v1/image/ path, the variant key and the source key. It
-// imports no other package of this repo, so every package that handles an
-// image request can import it.
+// the parsing of the /v1/image/ path, the variant key, the source key and the
+// source's upstream URL. It imports no other package of this repo, so every
+// package that handles an image request can import it.
 package imagerequest
 
 import (
 	"errors"
 	"net/url"
-	"time"
 )
 
 // ErrInvalidFitMode is returned when an invalid fit mode is provided.
@@ -85,19 +84,13 @@ func ValidateImageRequest(req *Request) error {
 }
 
 // Request represents a request for a processed image: the source to fetch
-// and the transform to apply to it.
+// and the transform to apply to it. It holds exactly what the variant key
+// covers.
 type Request struct {
 	// Source is what to fetch
 	Source Source
 	// Transform is what to do to it
 	Transform Transform
-	// Signature is the HMAC signature for non-allowlisted hosts
-	Signature string
-	// Expires is when the URL expires: the exp of a signed URL, or the expiry
-	// of an encrypted URL; the zero time if it has none
-	Expires time.Time
-	// AllowHTTP indicates whether HTTP (non-TLS) is allowed for this request
-	AllowHTTP bool
 }
 
 // Source is the image a request fetches from the origin.
@@ -125,23 +118,20 @@ type Transform struct {
 	FitMode Fit
 }
 
-// SourceURL returns the full upstream URL to fetch: the source path
-// percent-encoded again, as net/url writes a path, so each source path is one
-// upstream path, and the source query as it is, with the characters
-// escapeQuery encodes percent-encoded. Uses http:// scheme when AllowHTTP is
-// true, otherwise https://.
-func (r *Request) SourceURL() string {
+// URL returns the source's upstream URL, with the scheme http when allowHTTP
+// is true and https otherwise. net/url writes its path percent-encoded again,
+// so each source path is one upstream path. Its query is the source query as
+// it is, with the characters escapeQuery encodes percent-encoded.
+func (s Source) URL(allowHTTP bool) *url.URL {
 	scheme := "https"
-	if r.AllowHTTP {
+	if allowHTTP {
 		scheme = "http"
 	}
 
-	sourceURL := url.URL{
+	return &url.URL{
 		Scheme:   scheme,
-		Host:     r.Source.Host,
-		Path:     r.Source.Path,
-		RawQuery: escapeQuery(r.Source.Query),
+		Host:     s.Host,
+		Path:     s.Path,
+		RawQuery: escapeQuery(s.Query),
 	}
-
-	return sourceURL.String()
 }

internal/imagerequest/sourceurl_internal_test.go

@@ -2,57 +2,49 @@ package imagerequest
 
 import "testing"
 
-func TestRequest_SourceURL_DefaultHTTPS(t *testing.T) {
+func TestSource_URL_DefaultHTTPS(t *testing.T) {
 	t.Parallel()
 
-	req := &Request{
-		Source: Source{
-			Host:  testHostCDN,
-			Path:  testPathCat,
-			Query: "v=2",
-		},
+	source := Source{
+		Host:  testHostCDN,
+		Path:  testPathCat,
+		Query: "v=2",
 	}
 
-	got := req.SourceURL()
+	got := source.URL(false).String()
 
 	want := "https://cdn.example.com/photos/cat.jpg?v=2"
 	if got != want {
-		t.Errorf("SourceURL() = %q, want %q", got, want)
+		t.Errorf("URL() = %q, want %q", got, want)
 	}
 }
 
-func TestRequest_SourceURL_AllowHTTP(t *testing.T) {
+func TestSource_URL_AllowHTTP(t *testing.T) {
 	t.Parallel()
 
-	req := &Request{
-		Source: Source{
-			Host: "localhost:8080",
-			Path: testPathCat,
-		},
-		AllowHTTP: true,
+	source := Source{
+		Host: "localhost:8080",
+		Path: testPathCat,
 	}
 
-	got := req.SourceURL()
+	got := source.URL(true).String()
 
 	want := "http://localhost:8080/photos/cat.jpg"
 	if got != want {
-		t.Errorf("SourceURL() = %q, want %q", got, want)
+		t.Errorf("URL() = %q, want %q", got, want)
 	}
 }
 
-func TestRequest_SourceURL_AllowHTTPFalse(t *testing.T) {
+func TestSource_URL_AllowHTTPFalse(t *testing.T) {
 	t.Parallel()
 
-	req := &Request{
-		Source: Source{
-			Host: testHostCDN,
-			Path: "/img.jpg",
-		},
-		AllowHTTP: false,
+	source := Source{
+		Host: testHostCDN,
+		Path: "/img.jpg",
 	}
 
-	got := req.SourceURL()
+	got := source.URL(false).String()
 	if got != "https://cdn.example.com/img.jpg" {
-		t.Errorf("SourceURL() = %q, want https scheme", got)
+		t.Errorf("URL() = %q, want https scheme", got)
 	}
 }

internal/imagerequest/urlparser.go

@@ -126,15 +126,15 @@ func parseImageComponents(remainder string) (*Request, error) {
 		return nil, ErrMissingHost
 	}
 
-	// Only the forms hostRegex describes are accepted. A "?", "#" or "@" in
-	// the host would make Go's URL parser, which the allowlist check and the
-	// fetcher use, read a different host from the one allowlisted and cached
+	// Later steps put the host unparsed into the allowlist check, the cache key
+	// and the upstream URL, so only the forms hostRegex describes are accepted
 	hostMatch := hostRegex.FindStringSubmatch(host)
 	if hostMatch == nil {
 		return nil, fmt.Errorf("%w: %q", ErrInvalidHost, host)
 	}
 
-	// Go's URL parser refuses brackets around anything but an IPv6 address
+	// The allowlist check and the fetcher drop the brackets, so brackets
+	// around anything but an IPv6 address would give a host a second spelling
 	if inBrackets := hostMatch[1]; inBrackets != "" {
 		addr, err := netip.ParseAddr(inBrackets)
 		if err != nil || !addr.Is6() {
@@ -147,9 +147,8 @@ func parseImageComponents(remainder string) (*Request, error) {
 	// host
 	host = strings.ToLower(host)
 
-	// Go's URL parser, which the fetcher uses, reads a "#" as the start of a
-	// fragment and drops the rest, so each text after it would be another
-	// spelling, cached under its own keys, of one upstream request
+	// A "#" starts a URL's fragment, so neither the source path nor the source
+	// query may hold one
 	if strings.Contains(path, "#") {
 		return nil, fmt.Errorf(
 			`%w: the source path or query holds a "#"`, ErrInvalidPath)

internal/imgcache/concurrent_misses_internal_test.go

@@ -36,7 +36,7 @@ type heldFetcher struct {
 }
 
 func (f *heldFetcher) Fetch(
-	ctx context.Context, url string,
+	ctx context.Context, source imagerequest.Source,
 ) (*httpfetcher.FetchResult, error) {
 	f.fetches.Add(1)
 
@@ -48,7 +48,7 @@ func (f *heldFetcher) Fetch(
 		return nil, ctx.Err()
 	}
 
-	return f.upstream.Fetch(ctx, url)
+	return f.upstream.Fetch(ctx, source)
 }
 
 // releaseFetches lets every held fetch, and every later one, go on.
@@ -79,8 +79,8 @@ func setupHeldFetchService(t *testing.T) (*Service, *TestFixtures, *heldFetcher)
 }
 
 // photoVariant asks for the test photo, 100x100, at 50x25 as a JPEG of the
-// given quality and fit mode. Each call returns a new request, as Get writes
-// to the request it is given.
+// given quality and fit mode. Each call returns a new request, which a test
+// may change.
 func photoVariant(
 	fixtures *TestFixtures, quality int, fit imagerequest.Fit,
 ) *imagerequest.Request {
@@ -489,7 +489,7 @@ func TestService_Get_WaiterGetsProcessingTimedOut(t *testing.T) {
 type panickingFetcher struct{}
 
 func (panickingFetcher) Fetch(
-	context.Context, string,
+	context.Context, imagerequest.Source,
 ) (*httpfetcher.FetchResult, error) {
 	panic("upstream fetcher panicked")
 }

internal/imgcache/service.go

@@ -7,21 +7,17 @@ import (
 	"fmt"
 	"io"
 	"log/slog"
-	"net/url"
 	"runtime/debug"
-	"strings"
 	"time"
 
 	"github.com/dustin/go-humanize"
 	"github.com/getsentry/sentry-go"
 	"github.com/go-chi/chi/v5/middleware"
 	"golang.org/x/sync/singleflight"
-	"sneak.berlin/go/pixa/internal/allowlist"
 	"sneak.berlin/go/pixa/internal/httpfetcher"
 	"sneak.berlin/go/pixa/internal/imageprocessor"
 	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/magic"
-	"sneak.berlin/go/pixa/internal/signature"
 )
 
 // Service orchestrates the cache, fetcher, and processor.
@@ -29,10 +25,7 @@ type Service struct {
 	cache           *Cache
 	fetcher         httpfetcher.Fetcher
 	processor       *imageprocessor.ImageProcessor
-	signer          *signature.Signer
-	allowlist       *allowlist.HostAllowList
 	log             *slog.Logger
-	allowHTTP       bool
 	maxResponseSize int64
 	// variantsInProgress lets the requests that miss the same variant at the
 	// same time share one fetch and one transcode.
@@ -47,13 +40,6 @@ type ServiceConfig struct {
 	Fetcher httpfetcher.Fetcher
 	// Processor converts and resizes the images
 	Processor *imageprocessor.ImageProcessor
-	// SigningKey is the HMAC signing key (empty disables signing)
-	SigningKey string
-	// Allowlist is the list of hosts that don't require signatures
-	Allowlist []string
-	// AllowHTTP makes the service fetch sources over http instead of
-	// https (testing only), so the fetcher must allow http too
-	AllowHTTP bool
 	// MaxResponseSize is the largest source accepted, in bytes; a cached
 	// source larger than this is fetched again
 	MaxResponseSize int64
@@ -61,11 +47,8 @@ type ServiceConfig struct {
 	Logger *slog.Logger
 }
 
-// Static errors for service construction.
-var (
-	errCacheRequired      = errors.New("cache is required")
-	errSigningKeyRequired = errors.New("signing key is required")
-)
+// errCacheRequired is returned when the service is built without a cache.
+var errCacheRequired = errors.New("cache is required")
 
 // NewService creates a new image service.
 func NewService(cfg *ServiceConfig) (*Service, error) {
@@ -73,10 +56,6 @@ func NewService(cfg *ServiceConfig) (*Service, error) {
 		return nil, errCacheRequired
 	}
 
-	if cfg.SigningKey == "" {
-		return nil, errSigningKeyRequired
-	}
-
 	log := cfg.Logger
 	if log == nil {
 		log = slog.Default()
@@ -93,10 +72,7 @@ func NewService(cfg *ServiceConfig) (*Service, error) {
 		cache:           cfg.Cache,
 		fetcher:         cfg.Fetcher,
 		processor:       cfg.Processor,
-		signer:          signature.New(cfg.SigningKey),
-		allowlist:       allowlist.New(cfg.Allowlist),
 		log:             log,
-		allowHTTP:       cfg.AllowHTTP,
 		maxResponseSize: cfg.MaxResponseSize,
 	}, nil
 }
@@ -123,9 +99,6 @@ var ErrProcessingTimedOut = errors.New(
 func (s *Service) Get(
 	ctx context.Context, req *imagerequest.Request,
 ) (*ImageResponse, error) {
-	// Propagate AllowHTTP setting to the request
-	req.AllowHTTP = s.allowHTTP
-
 	cacheKey := imagerequest.CacheKey(req)
 
 	reader, size, contentType, err := s.cache.GetVariant(cacheKey)
@@ -169,33 +142,6 @@ func (s *Service) WaitForProcessing(ctx context.Context) int {
 	return s.processor.WaitForProcessing(ctx)
 }
 
-// ValidateRequest validates the request signature if required.
-func (s *Service) ValidateRequest(req *imagerequest.Request) error {
-	// Check if host is allowed (no signature required)
-	sourceURL := req.SourceURL()
-
-	parsedURL, err := url.Parse(sourceURL)
-	if err != nil {
-		return fmt.Errorf("invalid source URL: %w", err)
-	}
-
-	// An allowlist entry names no port, so a host followed by ":", with or
-	// without a port, needs a signature. The port is read from the parsed
-	// URL, as the fetcher reads it: in an IPv6 address written without
-	// brackets, such as 2001:db8::1:8443, it is what follows the last ":".
-	// This is checked here and not in allowlist.IsAllowed, which also matches
-	// referer_blocklist, where a Referer must be blocked whatever its port.
-	hostHasPort := parsedURL.Port() != "" ||
-		strings.HasSuffix(parsedURL.Host, ":")
-
-	if !hostHasPort && s.allowlist.IsAllowed(parsedURL) {
-		return nil
-	}
-
-	// Signature required for non-allowed hosts
-	return s.signer.Verify(req)
-}
-
 // errPanicked is returned when processing a variant panicked.
 var errPanicked = errors.New("panic while processing image")
 
@@ -388,11 +334,10 @@ func (s *Service) fetchAndProcess(
 	}
 
 	// Fetch from upstream
-	sourceURL := req.SourceURL()
+	s.log.Debug("fetching from upstream", "host", req.Source.Host,
+		"path", req.Source.Path, "query", req.Source.Query)
 
-	s.log.Debug("fetching from upstream", "url", sourceURL)
-
-	fetchResult, err := s.fetcher.Fetch(ctx, sourceURL)
+	fetchResult, err := s.fetcher.Fetch(ctx, req.Source)
 	if err != nil {
 		// Store negative cache for certain errors
 		if isNegativeCacheable(err) {

internal/imgcache/service_internal_test.go

@@ -9,17 +9,15 @@ import (
 
 	"sneak.berlin/go/pixa/internal/imagerequest"
 	"sneak.berlin/go/pixa/internal/magic"
-	"sneak.berlin/go/pixa/internal/signature"
 )
 
 // Test data literals used repeatedly in this file (goconst).
 const (
 	testPathPhoto  = "/images/photo.jpg"
 	testPathUpload = "/uploads/image.jpg"
-	testSigningKey = "test-signing-key-12345"
 )
 
-func TestService_Get_AllowlistedHost(t *testing.T) {
+func TestService_Get_GoodHost(t *testing.T) {
 	t.Parallel()
 
 	svc, fixtures := SetupTestService(t)
@@ -60,36 +58,12 @@ func TestService_Get_AllowlistedHost(t *testing.T) {
 	}
 }
 
-func TestService_Get_NonAllowlistedHost_NoSignature(t *testing.T) {
+// TestService_Get_OtherHost checks that the image service serves a second host
+// as it serves GoodHost.
+func TestService_Get_OtherHost(t *testing.T) {
 	t.Parallel()
 
-	svc, fixtures := SetupTestService(t, WithSigningKey("test-key"))
-
-	req := &imagerequest.Request{
-		Source: imagerequest.Source{
-			Host: fixtures.OtherHost,
-			Path: testPathUpload,
-		},
-		Transform: imagerequest.Transform{
-			Size:    imagerequest.Size{Width: 50, Height: 50},
-			Format:  imagerequest.FormatJPEG,
-			Quality: 85,
-			FitMode: imagerequest.FitCover,
-		},
-	}
-
-	// Should fail validation - not allowlisted and no signature
-	err := svc.ValidateRequest(req)
-	if err == nil {
-		t.Error("ValidateRequest() expected error for non-allowlisted host without signature")
-	}
-}
-
-func TestService_Get_NonAllowlistedHost_ValidSignature(t *testing.T) {
-	t.Parallel()
-
-	signingKey := testSigningKey
-	svc, fixtures := SetupTestService(t, WithSigningKey(signingKey))
+	svc, fixtures := SetupTestService(t)
 	ctx := context.Background()
 
 	req := &imagerequest.Request{
@@ -105,17 +79,6 @@ func TestService_Get_NonAllowlistedHost_ValidSignature(t *testing.T) {
 		},
 	}
 
-	// Generate a valid signature
-	signer := signature.New(signingKey)
-	req.Expires = time.Now().Add(time.Hour)
-	req.Signature = signer.Sign(req)
-
-	// Should pass validation
-	err := svc.ValidateRequest(req)
-	if err != nil {
-		t.Errorf("ValidateRequest() error = %v", err)
-	}
-
 	// Should fetch successfully
 	resp, err := svc.Get(ctx, req)
 	if err != nil {
@@ -134,244 +97,6 @@ func TestService_Get_NonAllowlistedHost_ValidSignature(t *testing.T) {
 	}
 }
 
-func TestService_Get_NonAllowlistedHost_ExpiredSignature(t *testing.T) {
-	t.Parallel()
-
-	signingKey := testSigningKey
-	svc, fixtures := SetupTestService(t, WithSigningKey(signingKey))
-
-	req := &imagerequest.Request{
-		Source: imagerequest.Source{
-			Host: fixtures.OtherHost,
-			Path: testPathUpload,
-		},
-		Transform: imagerequest.Transform{
-			Size:    imagerequest.Size{Width: 50, Height: 50},
-			Format:  imagerequest.FormatJPEG,
-			Quality: 85,
-			FitMode: imagerequest.FitCover,
-		},
-	}
-
-	// Generate an expired signature
-	signer := signature.New(signingKey)
-	req.Expires = time.Now().Add(-time.Hour) // Already expired
-	req.Signature = signer.Sign(req)
-
-	// Should fail validation
-	err := svc.ValidateRequest(req)
-	if err == nil {
-		t.Error("ValidateRequest() expected error for expired signature")
-	}
-}
-
-func TestService_Get_NonAllowlistedHost_InvalidSignature(t *testing.T) {
-	t.Parallel()
-
-	signingKey := testSigningKey
-	svc, fixtures := SetupTestService(t, WithSigningKey(signingKey))
-
-	req := &imagerequest.Request{
-		Source: imagerequest.Source{
-			Host: fixtures.OtherHost,
-			Path: testPathUpload,
-		},
-		Transform: imagerequest.Transform{
-			Size:    imagerequest.Size{Width: 50, Height: 50},
-			Format:  imagerequest.FormatJPEG,
-			Quality: 85,
-			FitMode: imagerequest.FitCover,
-		},
-	}
-
-	// Set an invalid signature
-	req.Signature = "invalid-signature"
-	req.Expires = time.Now().Add(time.Hour)
-
-	// Should fail validation
-	err := svc.ValidateRequest(req)
-	if err == nil {
-		t.Error("ValidateRequest() expected error for invalid signature")
-	}
-}
-
-// TestService_ValidateRequest_SignatureExactHostMatch verifies that
-// ValidateRequest enforces exact host matching for signatures. A
-// signature for one host must not verify for a different host, even
-// if they share a domain suffix.
-func TestService_ValidateRequest_SignatureExactHostMatch(t *testing.T) {
-	t.Parallel()
-
-	signingKey := "test-signing-key-must-be-32-chars"
-	svc, _ := SetupTestService(t,
-		WithSigningKey(signingKey),
-		WithNoAllowlist(),
-	)
-
-	signer := signature.New(signingKey)
-
-	// Sign a request for "cdn.example.com"
-	signedReq := &imagerequest.Request{
-		Source: imagerequest.Source{
-			Host: testHostCDN,
-			Path: testPathCat,
-		},
-		Transform: imagerequest.Transform{
-			Size:    imagerequest.Size{Width: 50, Height: 50},
-			Format:  imagerequest.FormatJPEG,
-			Quality: 85,
-			FitMode: imagerequest.FitCover,
-		},
-		Expires: time.Now().Add(time.Hour),
-	}
-	signedReq.Signature = signer.Sign(signedReq)
-
-	// The original request should pass validation
-	t.Run("exact host passes", func(t *testing.T) {
-		t.Parallel()
-
-		err := svc.ValidateRequest(signedReq)
-		if err != nil {
-			t.Errorf("ValidateRequest() exact host failed: %v", err)
-		}
-	})
-
-	// Try to reuse the signature with different hosts
-	tests := []struct {
-		name string
-		host string
-	}{
-		{"parent domain", testHostExample},
-		{"sibling subdomain", "images.example.com"},
-		{"deeper subdomain", "a.cdn.example.com"},
-		{"evil suffix domain", "cdn.example.com.evil.com"},
-		{"prefixed host", "evilcdn.example.com"},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name+" rejected", func(t *testing.T) {
-			t.Parallel()
-
-			req := &imagerequest.Request{
-				Source: imagerequest.Source{
-					Host:  tt.host,
-					Path:  signedReq.Source.Path,
-					Query: signedReq.Source.Query,
-				},
-				Transform: signedReq.Transform,
-				Expires:   signedReq.Expires,
-				Signature: signedReq.Signature,
-			}
-
-			err := svc.ValidateRequest(req)
-			if err == nil {
-				t.Errorf(
-					"ValidateRequest() should reject signature for host %q (signed for %q)",
-					tt.host, signedReq.Source.Host)
-			}
-		})
-	}
-}
-
-// TestService_ValidateRequest_HostWithPortNeedsSignature verifies that a host
-// followed by a port, or by a colon with no port, matches no allowlist entry,
-// so that a request for it without a signature is refused, while the same
-// host with no port is allowlisted.
-func TestService_ValidateRequest_HostWithPortNeedsSignature(t *testing.T) {
-	t.Parallel()
-
-	svc, _ := SetupTestService(t,
-		WithSigningKey(testSigningKey),
-		WithAllowlist(testHostCDN, "203.0.113.5", "2001:db8::1"),
-	)
-
-	tests := []struct {
-		host        string
-		allowlisted bool
-	}{
-		{testHostCDN, true},
-		{"cdn.example.com:8443", false},
-		{"cdn.example.com:443", false},
-		{"cdn.example.com:", false},
-		{"203.0.113.5", true},
-		{"203.0.113.5:8080", false},
-		{"[2001:db8::1]", true},
-		{"[2001:db8::1]:8443", false},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.host, func(t *testing.T) {
-			t.Parallel()
-
-			req := &imagerequest.Request{
-				Source: imagerequest.Source{
-					Host: tt.host,
-					Path: testPathCat,
-				},
-				Transform: imagerequest.Transform{
-					Size:    imagerequest.Size{Width: 50, Height: 50},
-					Format:  imagerequest.FormatJPEG,
-					Quality: 85,
-					FitMode: imagerequest.FitCover,
-				},
-			}
-
-			err := svc.ValidateRequest(req)
-			t.Logf("ValidateRequest() for host %q with no signature: %v",
-				tt.host, err)
-
-			if allowlisted := err == nil; allowlisted != tt.allowlisted {
-				t.Errorf("host %q served without a signature = %v, want %v",
-					tt.host, allowlisted, tt.allowlisted)
-			}
-		})
-	}
-}
-
-// TestService_ValidateRequest_UnbracketedIPv6PortNeedsSignature verifies that
-// an allowlisted IPv6 address written without brackets and followed by a
-// port, or by a colon with no port, needs a signature. Go's URL parser, which
-// the fetcher uses, reads 2001:db8::1:8443 as the host 2001:db8::1 with the
-// port 8443.
-func TestService_ValidateRequest_UnbracketedIPv6PortNeedsSignature(
-	t *testing.T,
-) {
-	t.Parallel()
-
-	svc, _ := SetupTestService(t,
-		WithSigningKey(testSigningKey),
-		WithAllowlist("2001:db8::1"),
-	)
-
-	for _, host := range []string{"2001:db8::1:8443", "2001:db8::1:"} {
-		t.Run(host, func(t *testing.T) {
-			t.Parallel()
-
-			req := &imagerequest.Request{
-				Source: imagerequest.Source{
-					Host: host,
-					Path: testPathCat,
-				},
-				Transform: imagerequest.Transform{
-					Size:    imagerequest.Size{Width: 50, Height: 50},
-					Format:  imagerequest.FormatJPEG,
-					Quality: 85,
-					FitMode: imagerequest.FitCover,
-				},
-			}
-
-			err := svc.ValidateRequest(req)
-			t.Logf("ValidateRequest() for host %q with no signature: %v",
-				host, err)
-
-			if err == nil {
-				t.Errorf("host %q served without a signature, want refused",
-					host)
-			}
-		})
-	}
-}
-
 func TestService_Get_InvalidFile(t *testing.T) {
 	t.Parallel()
 
@@ -692,33 +417,6 @@ func TestService_Get_DifferentSizes(t *testing.T) {
 	}
 }
 
-func TestService_ValidateRequest_NoSigningKey(t *testing.T) {
-	t.Parallel()
-
-	// Service with no signing key - all non-allowlisted requests should fail
-	svc, fixtures := SetupTestService(t, WithNoAllowlist())
-
-	req := &imagerequest.Request{
-		Source: imagerequest.Source{
-			Host: fixtures.OtherHost,
-			Path: testPathUpload,
-		},
-		Transform: imagerequest.Transform{
-			Size:    imagerequest.Size{Width: 50, Height: 50},
-			Format:  imagerequest.FormatJPEG,
-			Quality: 85,
-			FitMode: imagerequest.FitCover,
-		},
-	}
-
-	err := svc.ValidateRequest(req)
-	if err == nil {
-		t.Error(
-			"ValidateRequest() expected error when no signing key and host not allowlisted",
-		)
-	}
-}
-
 func TestService_Get_ContextCancellation(t *testing.T) {
 	t.Parallel()
 

internal/imgcache/stats_internal_test.go

@@ -93,7 +93,7 @@ type fakeUpstream struct {
 }
 
 func (u *fakeUpstream) Fetch(
-	context.Context, string,
+	context.Context, imagerequest.Source,
 ) (*httpfetcher.FetchResult, error) {
 	return &httpfetcher.FetchResult{
 		Content:       io.NopCloser(u),

internal/imgcache/testutil_internal_test.go

@@ -31,11 +31,11 @@ const (
 // TestFixtures contains paths to test files in the mock filesystem.
 type TestFixtures struct {
 	// Valid image files
-	GoodHostJPEG  string // allowlisted host, valid JPEG
-	GoodHostPNG   string // allowlisted host, valid PNG
-	GoodHostGIF   string // allowlisted host, valid GIF
-	OtherHostJPEG string // non-allowlisted host, valid JPEG
-	OtherHostPNG  string // non-allowlisted host, valid PNG
+	GoodHostJPEG  string // valid JPEG on GoodHost
+	GoodHostPNG   string // valid PNG on GoodHost
+	GoodHostGIF   string // valid GIF on GoodHost
+	OtherHostJPEG string // valid JPEG on OtherHost
+	OtherHostPNG  string // valid PNG on OtherHost
 
 	// Invalid/edge case files
 	InvalidFile string // file with wrong magic bytes
@@ -43,8 +43,8 @@ type TestFixtures struct {
 	TextFile    string // text file masquerading as image
 
 	// Hostnames
-	GoodHost  string // allowlisted hostname
-	OtherHost string // non-allowlisted hostname
+	GoodHost  string // a host the mock fetcher serves
+	OtherHost string // a second host the mock fetcher serves
 }
 
 // DefaultFixtures returns the standard test fixture paths.
@@ -161,22 +161,11 @@ func generateTestGIF(t *testing.T, width, height int, c color.Color) []byte {
 }
 
 // SetupTestService creates a Service with mock fetcher for testing.
-func SetupTestService(
-	t *testing.T, opts ...TestServiceOption,
-) (*Service, *TestFixtures) {
+func SetupTestService(t *testing.T) (*Service, *TestFixtures) {
 	t.Helper()
 
 	mockFS, fixtures := NewTestFS(t)
 
-	cfg := &testServiceConfig{
-		allowlist:  []string{fixtures.GoodHost},
-		signingKey: "test-signing-key-must-be-32-chars",
-	}
-
-	for _, opt := range opts {
-		opt(cfg)
-	}
-
 	// Create temp directory for cache
 	tmpDir := t.TempDir()
 
@@ -199,8 +188,6 @@ func SetupTestService(
 			MaxInputBytes:           50 << 20,
 			MaxConcurrentProcessing: 2,
 		}),
-		SigningKey:      cfg.signingKey,
-		Allowlist:       cfg.allowlist,
 		MaxResponseSize: 50 << 20,
 	})
 	if err != nil {
@@ -228,32 +215,3 @@ func setupServiceTestDB(t *testing.T) *sql.DB {
 
 	return db
 }
-
-type testServiceConfig struct {
-	allowlist  []string
-	signingKey string
-}
-
-// TestServiceOption configures the test service.
-type TestServiceOption func(*testServiceConfig)
-
-// WithAllowlist sets the allowlist for the test service.
-func WithAllowlist(hosts ...string) TestServiceOption {
-	return func(c *testServiceConfig) {
-		c.allowlist = hosts
-	}
-}
-
-// WithSigningKey sets the signing key for the test service.
-func WithSigningKey(key string) TestServiceOption {
-	return func(c *testServiceConfig) {
-		c.signingKey = key
-	}
-}
-
-// WithNoAllowlist removes all allowlisted hosts.
-func WithNoAllowlist() TestServiceOption {
-	return func(c *testServiceConfig) {
-		c.allowlist = nil
-	}
-}

internal/providers/providers.go

@@ -212,21 +212,15 @@ type imageServiceParams struct {
 }
 
 // newImageService builds the image service from the cache, the fetcher
-// and the processor, with the signing key, the allowlist and the upstream
-// settings of the config.
+// and the processor, with the largest upstream response the config allows.
 func newImageService(
 	_ fx.Lifecycle, params imageServiceParams,
 ) (*imgcache.Service, error) {
-	cfg := params.Config
-
 	return imgcache.NewService(&imgcache.ServiceConfig{
 		Cache:           params.Cache,
 		Fetcher:         params.Fetcher,
 		Processor:       params.Processor,
-		SigningKey:      cfg.SigningKey,
-		Allowlist:       cfg.AllowlistHosts,
-		AllowHTTP:       cfg.AllowHTTP,
-		MaxResponseSize: cfg.UpstreamMaxResponseSize,
+		MaxResponseSize: params.Config.UpstreamMaxResponseSize,
 		Logger:          params.Logger.Get(),
 	})
 }

internal/server/computed_side_internal_test.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"testing"
+	"time"
 
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/imagerequest"
@@ -76,7 +77,7 @@ func TestImageProxyRefusesComputedSideAboveMaximum(t *testing.T) {
 				Size:   imagerequest.Size{Width: tt.width, Height: tt.height},
 				Format: imagerequest.FormatJPEG,
 			},
-		})
+		}, time.Time{})
 		if err != nil {
 			t.Fatalf("encurl Generate: %v", err)
 		}

internal/server/fit_outside_internal_test.go

@@ -5,6 +5,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"testing"
+	"time"
 
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/imagerequest"
@@ -66,7 +67,7 @@ func TestImageProxyRefusesFitOutsideAboveMaximum(t *testing.T) {
 				Format:  imagerequest.FormatJPEG,
 				FitMode: imagerequest.FitOutside,
 			},
-		})
+		}, time.Time{})
 		if err != nil {
 			t.Fatalf("encurl Generate: %v", err)
 		}

internal/server/source_url_internal_test.go

@@ -524,8 +524,7 @@ func signedImageURL(t *testing.T, sourceHost string) string {
 			Quality: 85,
 			FitMode: imagerequest.FitCover,
 		},
-		Expires: expires,
-	})
+	}, expires)
 
 	// Go's percent-encoding of a URL path writes the brackets of the IPv6
 	// host as %5B and %5D.
@@ -549,7 +548,7 @@ func encryptedImageURL(t *testing.T, sourceHost string) string {
 	token, err := generator.Generate(&imagerequest.Request{
 		Source:    imagerequest.Source{Host: sourceHost, Path: ipv6SourcePath},
 		Transform: imagerequest.Transform{Format: imagerequest.FormatPNG},
-	})
+	}, time.Time{})
 	if err != nil {
 		t.Fatalf("encurl Generate: %v", err)
 	}

internal/server/svg_as_avif_internal_test.go

@@ -6,6 +6,7 @@ import (
 	"net/http/httptest"
 	"strings"
 	"testing"
+	"time"
 
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/imagerequest"
@@ -45,7 +46,7 @@ func TestImageProxyRefusesSVGServedAsAVIF(t *testing.T) {
 				Size:   imagerequest.Size{Width: 32, Height: 24},
 				Format: format,
 			},
-		})
+		}, time.Time{})
 		if err != nil {
 			t.Fatalf("encurl Generate: %v", err)
 		}

internal/signature/escaping_test.go

@@ -28,20 +28,20 @@ func TestSigner_Verify_ColonCannotMovePathQueryBoundary(t *testing.T) {
 			Quality: 85,
 			FitMode: testFitCover,
 		},
-		Expires: time.Now().Add(1 * time.Hour),
 	}
-	signed.Signature = signer.Sign(signed)
+	expires := time.Now().Add(1 * time.Hour)
+	sig := signer.Sign(signed, expires)
 
 	replayed := *signed
 	replayed.Source.Path = "/a"
 	replayed.Source.Query = "b:"
 
 	t.Logf("signature for path %q query %q: %s",
-		signed.Source.Path, signed.Source.Query, signed.Signature)
+		signed.Source.Path, signed.Source.Query, sig)
 	t.Logf("signature for path %q query %q: %s",
-		replayed.Source.Path, replayed.Source.Query, signer.Sign(&replayed))
+		replayed.Source.Path, replayed.Source.Query, signer.Sign(&replayed, expires))
 
-	err := signer.Verify(&replayed)
+	err := signer.Verify(&replayed, sig, expires)
 	if !errors.Is(err, signature.ErrInvalid) {
 		t.Errorf("Verify() of path %q query %q with the signature for "+
 			"path %q = %v, want %v",
@@ -106,10 +106,9 @@ func TestSigner_EscapedGoldenVectors(t *testing.T) {
 					Quality: 85,
 					FitMode: testFitCover,
 				},
-				Expires: time.Unix(goldenExpiresUnix, 0),
 			}
 
-			gotSignature := signer.Sign(req)
+			gotSignature := signer.Sign(req, time.Unix(goldenExpiresUnix, 0))
 			t.Logf("Sign() of path %q query %q = %s", tt.path, tt.query, gotSignature)
 
 			if gotSignature != tt.wantSignature {

internal/signature/golden_test.go

@@ -19,8 +19,8 @@ type goldenVector struct {
 	name string
 	req  imagerequest.Request
 	// wantSignature is the exact base64url (RFC 4648 URL-safe,
-	// padded) HMAC-SHA256 signature for the request with Expires
-	// set to goldenExpiresUnix.
+	// padded) HMAC-SHA256 signature for the request expiring at
+	// goldenExpiresUnix.
 	wantSignature string
 }
 
@@ -124,9 +124,8 @@ func TestSigner_GoldenVectors(t *testing.T) {
 			t.Parallel()
 
 			signReq := tt.req
-			signReq.Expires = time.Unix(goldenExpiresUnix, 0)
 
-			gotSignature := signer.Sign(&signReq)
+			gotSignature := signer.Sign(&signReq, time.Unix(goldenExpiresUnix, 0))
 			if gotSignature != tt.wantSignature {
 				t.Errorf("Sign() = %q, want %q (signed byte format changed?)",
 					gotSignature, tt.wantSignature)

internal/signature/quality_fit_test.go

@@ -9,10 +9,12 @@ import (
 	"sneak.berlin/go/pixa/internal/signature"
 )
 
-// signedQualityFitRequest returns a request signed for quality 85 and fit
-// mode "cover", the effective defaults the handler applies before
-// verification.
-func signedQualityFitRequest(signer *signature.Signer) *imagerequest.Request {
+// signedQualityFitRequest returns a request, its signature for quality 85 and
+// fit mode "cover", the effective defaults the handler applies before
+// verification, and the expiry it was signed with.
+func signedQualityFitRequest(
+	signer *signature.Signer,
+) (*imagerequest.Request, string, time.Time) {
 	req := &imagerequest.Request{
 		Source: imagerequest.Source{
 			Host: testHost,
@@ -24,11 +26,10 @@ func signedQualityFitRequest(signer *signature.Signer) *imagerequest.Request {
 			Quality: 85,
 			FitMode: testFitCover,
 		},
-		Expires: time.Now().Add(1 * time.Hour),
 	}
-	req.Signature = signer.Sign(req)
+	expires := time.Now().Add(1 * time.Hour)
 
-	return req
+	return req, signer.Sign(req, expires), expires
 }
 
 // TestSigner_Verify_QualityAndFitAreSigned proves that quality and fit are
@@ -60,10 +61,10 @@ func TestSigner_Verify_QualityAndFitAreSigned(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
 
-			req := signedQualityFitRequest(signer)
+			req, sig, expires := signedQualityFitRequest(signer)
 			tt.tamper(req)
 
-			err := signer.Verify(req)
+			err := signer.Verify(req, sig, expires)
 			if !errors.Is(err, signature.ErrInvalid) {
 				t.Errorf("Verify() = %v, want %v", err, signature.ErrInvalid)
 			}

internal/signature/signature.go

@@ -34,14 +34,14 @@ func New(secretKey string) *Signer {
 	}
 }
 
-// Sign generates an HMAC-SHA256 signature for the given request.
-// The signature covers: host + path + query + width + height + format +
-// expiration + quality + fit. The quality and fit mode are the effective
-// values the request resolves to: callers pass the defaults when the request
-// omits those parameters, so an omitted quality or fit mode signs
+// Sign generates an HMAC-SHA256 signature for the given request, expiring at
+// expires. The signature covers: host + path + query + width + height +
+// format + expiration + quality + fit. The quality and fit mode are the
+// effective values the request resolves to: callers pass the defaults when
+// the request omits those parameters, so an omitted quality or fit mode signs
 // identically to that same value stated explicitly.
-func (s *Signer) Sign(req *imagerequest.Request) string {
-	data := s.buildSignatureData(req)
+func (s *Signer) Sign(req *imagerequest.Request, expires time.Time) string {
+	data := s.buildSignatureData(req, expires)
 	mac := hmac.New(sha256.New, s.secretKey)
 	mac.Write([]byte(data))
 	sig := mac.Sum(nil)
@@ -49,28 +49,31 @@ func (s *Signer) Sign(req *imagerequest.Request) string {
 	return base64.URLEncoding.EncodeToString(sig)
 }
 
-// Verify checks if the signature on the request is valid and not expired.
+// Verify checks that sig is the signature of the request expiring at expires,
+// and that expires has not passed.
 // Signatures are exact-match only: every component of the signed data
 // (host, path, query, dimensions, format, expiration, quality, fit) must
 // match exactly.
 // No suffix matching, wildcard matching, or partial matching is supported.
 // A signature for "cdn.example.com" will NOT verify for "example.com" or
 // "other.cdn.example.com", and vice versa.
-func (s *Signer) Verify(req *imagerequest.Request) error {
+func (s *Signer) Verify(
+	req *imagerequest.Request, sig string, expires time.Time,
+) error {
 	// Check expiration first
-	if req.Expires.IsZero() {
+	if expires.IsZero() {
 		return ErrMissingExpiration
 	}
 
-	if time.Now().After(req.Expires) {
+	if time.Now().After(expires) {
 		return ErrExpired
 	}
 
 	// Compute expected signature
-	expected := s.Sign(req)
+	expected := s.Sign(req, expires)
 
 	// Constant-time comparison to prevent timing attacks
-	if !hmac.Equal([]byte(req.Signature), []byte(expected)) {
+	if !hmac.Equal([]byte(sig), []byte(expected)) {
 		return ErrInvalid
 	}
 
@@ -85,7 +88,9 @@ func (s *Signer) Verify(req *imagerequest.Request) error {
 // expansion is performed. Quality and fit are the effective transform
 // values, so replaying a signed URL with a different quality or fit mode
 // fails verification.
-func (s *Signer) buildSignatureData(req *imagerequest.Request) string {
+func (s *Signer) buildSignatureData(
+	req *imagerequest.Request, expires time.Time,
+) string {
 	return fmt.Sprintf("%s:%s:%s:%d:%d:%s:%d:%d:%s",
 		req.Source.Host,
 		escapePercentAndColon(req.Source.Path),
@@ -93,7 +98,7 @@ func (s *Signer) buildSignatureData(req *imagerequest.Request) string {
 		req.Transform.Size.Width,
 		req.Transform.Size.Height,
 		req.Transform.Format,
-		req.Expires.Unix(),
+		expires.Unix(),
 		req.Transform.Quality,
 		req.Transform.FitMode,
 	)

internal/signature/signature_test.go

@@ -34,11 +34,11 @@ func TestSigner_Sign(t *testing.T) {
 			Size:   imagerequest.Size{Width: 800, Height: 600},
 			Format: testFormatWebP,
 		},
-		Expires: time.Unix(1704067200, 0), // Fixed timestamp for reproducibility
 	}
+	expires := time.Unix(1704067200, 0) // Fixed timestamp for reproducibility
 
-	sig1 := signer.Sign(req)
-	sig2 := signer.Sign(req)
+	sig1 := signer.Sign(req, expires)
+	sig2 := signer.Sign(req, expires)
 
 	// Same input should produce same signature
 	if sig1 != sig2 {
@@ -62,18 +62,17 @@ func TestSigner_Sign(t *testing.T) {
 			Size:   imagerequest.Size{Width: 800, Height: 600},
 			Format: testFormatWebP,
 		},
-		Expires: time.Unix(1704067200, 0),
 	}
 
-	sig3 := signer.Sign(req2)
+	sig3 := signer.Sign(req2, expires)
 	if sig1 == sig3 {
 		t.Error("Sign() produced same signature for different input")
 	}
 }
 
-// validVerifyRequest returns a fully-populated request that verifies
-// successfully once signed.
-func validVerifyRequest() *imagerequest.Request {
+// validVerifyRequest returns a fully-populated request, and an expiry an hour
+// ahead, that verify successfully once signed.
+func validVerifyRequest() (*imagerequest.Request, time.Time) {
 	return &imagerequest.Request{
 		Source: imagerequest.Source{
 			Host: testHost,
@@ -83,13 +82,13 @@ func validVerifyRequest() *imagerequest.Request {
 			Size:   imagerequest.Size{Width: 800, Height: 600},
 			Format: testFormatWebP,
 		},
-		Expires: time.Now().Add(1 * time.Hour),
-	}
+	}, time.Now().Add(1 * time.Hour)
 }
 
 type verifyCase struct {
-	name    string
-	setup   func() *imagerequest.Request
+	name string
+	// setup returns the request, the signature and the expiry to verify
+	setup   func() (*imagerequest.Request, string, time.Time)
 	wantErr error
 }
 
@@ -97,54 +96,49 @@ func verifyCases(signer *signature.Signer) []verifyCase {
 	return []verifyCase{
 		{
 			name: "valid signature",
-			setup: func() *imagerequest.Request {
-				req := validVerifyRequest()
-				req.Signature = signer.Sign(req)
+			setup: func() (*imagerequest.Request, string, time.Time) {
+				req, expires := validVerifyRequest()
 
-				return req
+				return req, signer.Sign(req, expires), expires
 			},
 			wantErr: nil,
 		},
 		{
 			name: "expired signature",
-			setup: func() *imagerequest.Request {
-				req := validVerifyRequest()
-				req.Expires = time.Now().Add(-1 * time.Hour)
-				req.Signature = signer.Sign(req)
+			setup: func() (*imagerequest.Request, string, time.Time) {
+				req, _ := validVerifyRequest()
+				expires := time.Now().Add(-1 * time.Hour)
 
-				return req
+				return req, signer.Sign(req, expires), expires
 			},
 			wantErr: signature.ErrExpired,
 		},
 		{
 			name: "invalid signature",
-			setup: func() *imagerequest.Request {
-				req := validVerifyRequest()
-				req.Signature = "invalid-signature"
+			setup: func() (*imagerequest.Request, string, time.Time) {
+				req, expires := validVerifyRequest()
 
-				return req
+				return req, "invalid-signature", expires
 			},
 			wantErr: signature.ErrInvalid,
 		},
 		{
 			name: "missing expiration",
-			setup: func() *imagerequest.Request {
-				req := validVerifyRequest()
-				req.Expires = time.Time{}
-				req.Signature = "some-signature"
+			setup: func() (*imagerequest.Request, string, time.Time) {
+				req, _ := validVerifyRequest()
 
-				return req
+				return req, "some-signature", time.Time{}
 			},
 			wantErr: signature.ErrMissingExpiration,
 		},
 		{
 			name: "tampered request",
-			setup: func() *imagerequest.Request {
-				req := validVerifyRequest()
-				req.Signature = signer.Sign(req)
+			setup: func() (*imagerequest.Request, string, time.Time) {
+				req, expires := validVerifyRequest()
+				sig := signer.Sign(req, expires)
 				req.Source.Path = "/photos/secret.jpg"
 
-				return req
+				return req, sig, expires
 			},
 			wantErr: signature.ErrInvalid,
 		},
@@ -160,8 +154,8 @@ func TestSigner_Verify(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
 
-			req := tt.setup()
-			err := signer.Verify(req)
+			req, sig, expires := tt.setup()
+			err := signer.Verify(req, sig, expires)
 
 			if tt.wantErr == nil {
 				if err != nil {
@@ -254,8 +248,9 @@ func TestSigner_Verify_ExactMatchOnly(t *testing.T) {
 
 	signer := signature.New("test-secret-key")
 
-	// Base request that we'll sign, then tamper with individual fields.
-	baseReq := func() *imagerequest.Request {
+	// Base request that we'll sign, then tamper with individual fields; it
+	// is returned with its signature and expiry.
+	baseReq := func() (*imagerequest.Request, string, time.Time) {
 		req := &imagerequest.Request{
 			Source: imagerequest.Source{
 				Host:  testHost,
@@ -266,21 +261,20 @@ func TestSigner_Verify_ExactMatchOnly(t *testing.T) {
 				Size:   imagerequest.Size{Width: 800, Height: 600},
 				Format: testFormatWebP,
 			},
-			Expires: time.Now().Add(1 * time.Hour),
 		}
-		req.Signature = signer.Sign(req)
+		expires := time.Now().Add(1 * time.Hour)
 
-		return req
+		return req, signer.Sign(req, expires), expires
 	}
 
 	for _, tt := range exactMatchTamperCases() {
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
 
-			req := baseReq()
+			req, sig, expires := baseReq()
 			tt.tamper(req)
 
-			err := signer.Verify(req)
+			err := signer.Verify(req, sig, expires)
 			if !errors.Is(err, signature.ErrInvalid) {
 				t.Errorf("Verify() = %v, want %v", err, signature.ErrInvalid)
 			}
@@ -291,9 +285,9 @@ func TestSigner_Verify_ExactMatchOnly(t *testing.T) {
 	t.Run("unmodified request passes", func(t *testing.T) {
 		t.Parallel()
 
-		req := baseReq()
+		req, sig, expires := baseReq()
 
-		err := signer.Verify(req)
+		err := signer.Verify(req, sig, expires)
 		if err != nil {
 			t.Errorf("Verify() unmodified request failed: %v", err)
 		}
@@ -329,10 +323,9 @@ func TestSigner_Sign_ExactHostInData(t *testing.T) {
 				Size:   imagerequest.Size{Width: 800, Height: 600},
 				Format: testFormatWebP,
 			},
-			Expires: time.Unix(1704067200, 0),
 		}
 
-		sig := signer.Sign(req)
+		sig := signer.Sign(req, time.Unix(1704067200, 0))
 		if existing, ok := sigs[sig]; ok {
 			t.Errorf("hosts %q and %q produced the same signature", existing, host)
 		}
@@ -356,20 +349,20 @@ func TestSigner_DifferentKeys(t *testing.T) {
 			Size:   imagerequest.Size{Width: 800, Height: 600},
 			Format: testFormatWebP,
 		},
-		Expires: time.Now().Add(1 * time.Hour),
 	}
+	expires := time.Now().Add(1 * time.Hour)
 
 	// Sign with key 1
-	req.Signature = signer1.Sign(req)
+	sig := signer1.Sign(req, expires)
 
 	// Verify with key 1 should succeed
-	err := signer1.Verify(req)
+	err := signer1.Verify(req, sig, expires)
 	if err != nil {
 		t.Errorf("Verify() with same key failed: %v", err)
 	}
 
 	// Verify with key 2 should fail
-	err = signer2.Verify(req)
+	err = signer2.Verify(req, sig, expires)
 	if !errors.Is(err, signature.ErrInvalid) {
 		t.Errorf("Verify() with different key should fail, got: %v", err)
 	}
@@ -395,12 +388,11 @@ func TestSign_ReadmeQueryExample(t *testing.T) {
 			Quality: 85,
 			FitMode: testFitCover,
 		},
-		Expires: time.Unix(1704067200, 0),
 	}
 
 	const wantSig = "37aFa9GSVCZM1kRY9SzMOk2fOg_M7Wt5gKNR4xM-FYA="
 
-	gotSig := signer.Sign(&req)
+	gotSig := signer.Sign(&req, time.Unix(1704067200, 0))
 	if gotSig != wantSig {
 		t.Errorf("Sign() = %q, want %q", gotSig, wantSig)
 	}