Say govips gives pixa no way to stop an encode; give AVIF's worst case

libvips can stop a running encode, but govips gives pixa no way to ask
it to, which README.md "Routes" and the Process and encode comments
now say in place of "libvips cannot stop an encode". The avifEffort
comment gives its 51 seconds as the RGB time and 110 seconds with an
alpha channel as the worst case, as README.md does.

Model: opus-5-5

README.md

@@ -71,10 +71,9 @@ The state directory (`state_dir`, `/var/lib/pixa` in the container) holds the
 database and the disk cache:
 
 - It needs a persistent volume: without one, every restart starts with an empty
-  cache and forgets the latest logout, so the login sessions that logout ended
-  work again (see Encrypted URLs). In the container, the startup script gives
-  the directory to the user pixa runs as (uid 65532) and sets its mode to `750`;
-  outside it, that user must be able to write the directory.
+  cache. In the container, the startup script gives the directory to the user
+  pixa runs as (uid 65532) and sets its mode to `750`; outside it, that user
+  must be able to write the directory.
 - `cache_max_bytes` limits the source and transformed images together. The
   database, the metadata files, the `.meta` file beside each transformed image
   and files still being written come on top, and eviction runs in the
@@ -185,10 +184,7 @@ path under `/v1/` answers 200, in maintenance mode too.
   session it answers 303 to `/`. Answers: 200 with the page showing the URL; 400
   with the page naming a field that is not valid; 500 when the URL cannot be
   made.
-- `GET /logout` — end every login session, in every browser (see Encrypted
-  URLs), and remove the session cookie. Needs: a login session; without one it
-  only removes the cookie. Answers: 303 to `/`; 500 when the logout cannot be
-  saved in the database.
+- `GET /logout` — end the login session. Needs: nothing. Answers: 303 to `/`.
 - `GET` or `HEAD` `/v1/image/<host>/<path>/<size>.<format>`, or
   `/v1/image/<host>/<path>/<size>` with no format — an image, fetched, resized
   and converted (below). Needs: a signature, unless the host is allowlisted (see
@@ -204,9 +200,10 @@ path under `/v1/` answers 200, in maintenance mode too.
   `image_requests_per_minute` (below); 415 when the upstream answers with a
   `Content-Type` that is not one of the source formats (below), or with an image
   whose first bytes libvips reads as another format; 502 when the upstream
-  answered with an error status, and for 5 minutes after that for the same
-  source URL; 503 when pixa is busy or in maintenance mode; 500 for any other
-  failure.
+  answered with an error status, and for 5 minutes after that for an image of
+  the same source URL that pixa can neither serve from its cache nor make from
+  the source image still in its cache; 503 when pixa is busy or in maintenance
+  mode; 500 for any other failure.
 - `GET` or `HEAD` `/v1/e/<token>/<name>` — an image through an encrypted URL
   (see Encrypted URLs). Needs: nothing but the URL. Answers: 200; 304 when
   `If-None-Match` matches the image's `ETag`; 400 for a token that does not
@@ -317,9 +314,26 @@ cache at once, they share one upstream fetch (or one read of the cached source)
 and one transcode: the first request does the work, and the others wait for its
 image or its error, holding no upstream connection or processing slot of their
 own. A waiting request stops waiting when its own client goes away. The work
-goes on for the others even if the first request's client goes away, until that
-request's `downstream_timeout` ends. The shared fetch sends the first request's
-ID upstream, and the lines logged for the fetch and the transcode carry that ID.
+goes on for the others even if the first request's client goes away. The shared
+fetch sends the first request's ID upstream, and the lines logged for the fetch
+and the transcode carry that ID.
+
+A transcode whose request's `downstream_timeout` has ended (for a shared one,
+the first request's) stops waiting for a processing slot, or, once it has one,
+gives it back without beginning to encode. A request waiting for a shared
+transcode that stops this way is answered 503 with the error
+`server busy, try again later`, though its own `downstream_timeout` may not have
+ended. govips gives pixa no way to stop libvips once an encode has begun, so an
+encode keeps its slot until it finishes, which can be after
+`downstream_timeout`. The limit of 8192 on each side of the source and of the
+output bounds how long that takes. With one libvips thread, as pixad runs it,
+encoding 8192x8192 random pixels takes up to about 1 second as JPEG, 15 as PNG,
+16 as GIF, 63 as WebP, 110 as AVIF and 96 as JPEG XL, the slowest of 8 or 16
+bits per sample, with or without an alpha channel. WebP, AVIF and JPEG XL are
+that slow only with an alpha channel: 8-bit RGB takes about 44, 53 and 28
+seconds. Decoding such a source adds up to about 11 seconds. A WebP, AVIF or
+JPEG XL encode can therefore hold its slot past the default `downstream_timeout`
+of 60 seconds.
 
 The login form (`POST /`) is limited to 5 attempts per minute per client
 address, counting an IPv6 client by its /64; an attempt over the limit is
@@ -356,11 +370,7 @@ nor change what it asks for.
 
 1. Open `/` in a browser over HTTPS (or over plain HTTP while `debug` is on, see
    Routes) and log in with the signing key (`signing_key`). The login session
-   lasts 30 days, or until someone logs out at `/logout`. Every login is made
-   with the one signing key, so logging out ends every login session, in every
-   browser: pixa saves the time of the latest logout in its database and refuses
-   a login session made before it, a copy of the session cookie included, also
-   after a restart that keeps the state directory (see Deployment).
+   lasts 30 days, or until `/logout`.
 2. On the generator page, give the source image's URL, the width and height, the
    format, quality and fit, and how long the URL lasts, then submit the form
    (`POST /generate`). The format is JPEG XL unless another is chosen; a form
@@ -426,9 +436,14 @@ HMAC-SHA256(secret, "host:path:query:width:height:format:expiration:quality:fit"
 
 Where:
 
-- `host` — source origin hostname (e.g. `cdn.example.com`)
-- `path` — source path (e.g. `/photos/cat.jpg`)
-- `query` — source query string, empty string if none
+- `host` — source host as the URL writes it up to the first `/`, in lower case,
+  keeping an IPv6 address's brackets and any `:` and port after it (e.g.
+  `cdn.example.com`, `cdn.example.com:8443`, `[2001:db8::1]:8443`)
+- `path` — source path (e.g. `/photos/cat.jpg`), with each `%` written as `%25`
+  and each `:` as `%3A`, so `/photos/a:b.jpg` is signed as `/photos/a%3Ab.jpg`
+- `query` — source query string, empty string if none, with `%` and `:` written
+  as in `path`; neither then holds a `:`, so path `/a:b` with no query and path
+  `/a` with query `b:` are signed differently
 - `width` — requested width in pixels, `0` for original
 - `height` — requested height in pixels, `0` for original
 - `format` — output format, one of those listed under Routes, with `original`
@@ -478,6 +493,12 @@ entry that is neither a host name (letters, digits, hyphens, underscores and
 dots, with at most one leading dot) nor an IP address, such as one with a port
 or a `*.` wildcard, aborts startup.
 
+pixa lower-cases the host of a `/v1/image/` URL before anything else uses it, so
+`CDN.Example.com` is matched, fetched, cached and counted against
+`upstream_connections_per_host` as `cdn.example.com`. Such a URL whose host has
+a port, as in `cdn.example.com:8443`, or a `:` with no port, needs a signature
+even when the host is allowlisted. A host holding `@` is refused with 400.
+
 ### Configuration
 
 Every setting can be given as an environment variable, in a YAML config file

TODO.md

@@ -30,18 +30,53 @@ P2: security: per-origin rate limiting
 
 # Completed Steps
 
-- 2026-10-15 logging out ends every login session (closes #256): a login session
-  was a cookie with nothing kept on the server, so `/logout` removed it from one
-  browser and a copy of it kept working for its 30 days. Every login is made
-  with the one signing key, so `/logout` now ends them all: the session manager
-  keeps the time of the latest logout, saves it in the new `logout` table so
-  that it outlasts a restart, and refuses a session made before it. A restart
-  without a persistent volume for the state directory forgets it. A `/logout`
-  without a valid login session, such as one another site makes a browser send
-  without the `SameSite=Strict` cookie, ends none and only removes the cookie. A
-  logout that cannot be saved answers 500. `session.NewManager`, which the tests
-  use, keeps logouts in memory only; pixad uses
-  `session.NewManagerWithDatabase`.
+- 2026-10-15 a transcode stops once its request's `downstream_timeout` has
+  ended, unless it has begun encoding (closes #243): the image processor looked
+  at its context only while it waited for a processing slot, so an image was
+  decoded and encoded, holding the slot, however long after its request's
+  deadline that took. `Process` now returns the context's error, and gives the
+  slot back, when the context has ended by the time it has the slot or before it
+  encodes. A request that waited for a shared transcode stopped at the first
+  request's deadline is answered 503 `server busy, try again later`, not 500,
+  though its own `downstream_timeout` may not have ended. govips gives pixa no
+  way to stop libvips once an encode has begun, so that encode keeps its slot
+  until it finishes; the limit of 8192 on each side of the source and of the
+  output bounds how long that takes. With one libvips thread, 8192x8192 random
+  pixels take up to about 1 second to encode as JPEG, 15 as PNG, 16 as GIF, 63
+  as WebP, 110 as AVIF and 96 as JPEG XL, the last three with an alpha channel,
+  plus up to about 11 seconds to decode the source; `README.md` gives these
+  times and no longer says the work stops when `downstream_timeout` ends. The
+  settings of the WebP, AVIF and JPEG XL encoders, which can hold a slot past
+  the default `downstream_timeout` of 60 seconds, are unchanged.
+- 2026-10-15 a cached variant is served while its source URL is in the negative
+  cache (closes #245): `Get` checked the negative cache before the variant
+  cache, so once a fetch of the source failed, as one does when another variant
+  misses after the source was evicted and the upstream is down, every variant of
+  that source answered 502 for 5 minutes, also one on disk or one that could be
+  made from the cached source. The negative cache is now checked only just
+  before a fetch from the upstream, so a cached variant is served and a variant
+  not in the cache is made from the cached source when there is one. `README.md`
+  says so under `/v1/image/`. A refusal from the negative cache now counts as a
+  miss, as any other request that misses the variant cache does.
+- 2026-10-15 the host of a `/v1/image/` URL is lower-cased, and one with a port
+  needs a signature (closes #246): with `cdn.example.com` allowlisted,
+  `CDN.Example.com` and `cdn.example.com:8443` passed the allowlist too, and
+  each spelling was fetched and cached on its own and had connections of its own
+  under `upstream_connections_per_host`. The image URL parser now lower-cases
+  the host and refuses one holding `@`, which a URL reads as a user name and
+  password, with 400. A host with a port, or with a `:` and no port, needs a
+  signature even when it is allowlisted. That is checked in the image service,
+  not in `allowlist.IsAllowed`, which also matches `referer_blocklist`, where a
+  `Referer` is blocked whatever its port. A URL is signed over its host as it
+  writes it, in lower case, with any IPv6 brackets, `:` and port kept.
+- 2026-10-15 a `:` in the source path or query no longer moves where the path
+  ends and the query begins (closes #247): the signed data and the cache key
+  joined host, path and query with `:` and no escaping, so a URL signed for
+  `https://h/a:b` verified for `https://h/a?b:`; the two also shared a cache
+  key, and whichever was fetched first was served for both. In both, the path
+  and the query now have each `%` written as `%25` and each `:` as `%3A`; a path
+  and query holding neither are signed and keyed as before. Signature
+  Specification in `README.md` says so.
 - 2026-10-15 the example config allowlists no host (closes #249): it allowlisted
   `github.com` and `user-images.githubusercontent.com`, where anyone can put an
   image, so a deployment set up as Getting Started says served those images to
@@ -505,11 +540,11 @@ P2: security: per-origin rate limiting
   cancellation but keeps its deadline, and the others wait for its image or
   error holding no upstream connection or processing slot, and stop waiting when
   their own context ends; the request doing the processing waits for it even
-  then, up to its deadline; a request whose context has already ended starts
-  nothing; each request counts one miss, and the processing counts its fetch and
-  transcode once; a panic while processing is reported to Sentry when
-  `sentry_dsn` is set and becomes an error for every waiting request instead of
-  stopping pixad; documented in `README.md`.
+  then, until it ends, which can be after its deadline; a request whose context
+  has already ended starts nothing; each request counts one miss, and the
+  processing counts its fetch and transcode once; a panic while processing is
+  reported to Sentry when `sentry_dsn` is set and becomes an error for every
+  waiting request instead of stopping pixad; documented in `README.md`.
 - 2026-09-29 only the image routes send CORS headers (closes #98): the CORS
   middleware, with the `access_control_allow_origin` origin, moved from the
   router root onto a `/v1` subrouter holding `/v1/image/` and `/v1/e/`, where it

internal/db/migrations/001_schema.sql

@@ -176,10 +176,3 @@ CREATE TABLE IF NOT EXISTS cache_stats (
     last_updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
 );
 INSERT OR IGNORE INTO cache_stats (id) VALUES (1);
-
--- Time of the latest logout. A login session made before it is refused,
--- so logging out ends every login session. No row: nobody has logged out.
-CREATE TABLE IF NOT EXISTS logout (
-    id INTEGER PRIMARY KEY CHECK (id = 1),
-    logged_out_at DATETIME NOT NULL
-);

internal/handlers/auth.go

@@ -89,18 +89,10 @@ func (s *Handlers) handleLoginPost(w http.ResponseWriter, r *http.Request) {
 	http.Redirect(w, r, "/", http.StatusSeeOther)
 }
 
-// HandleLogout logs out, which ends every login session (see
-// session.Manager.Logout), and redirects to login.
+// HandleLogout clears the session and redirects to login.
 func (s *Handlers) HandleLogout() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		err := s.sessMgr.Logout(w, r)
-		if err != nil {
-			s.log.Error("failed to log out", "error", err)
-			http.Error(w, "Failed to log out", http.StatusInternalServerError)
-
-			return
-		}
-
+		s.sessMgr.ClearSession(w)
 		http.Redirect(w, r, "/", http.StatusSeeOther)
 	}
 }

internal/handlers/auth_session_internal_test.go

@@ -185,98 +185,6 @@ func TestHandleLogout_ClearsSessionCookie(t *testing.T) {
 	}
 }
 
-// TestHandleLogout_EndsCopiedSession verifies that after GET /logout a copy
-// of the session cookie taken before it shows the login page, not the
-// generator page.
-func TestHandleLogout_EndsCopiedSession(t *testing.T) {
-	t.Parallel()
-
-	h, srv := newCSRFTestRouter(t)
-
-	copied := newSessionCookie(t, h)
-
-	req := httptest.NewRequestWithContext(
-		t.Context(), http.MethodGet, "/logout", nil)
-	req.AddCookie(copied)
-
-	rec := httptest.NewRecorder()
-	h.HandleLogout().ServeHTTP(rec, req)
-
-	if rec.Code != http.StatusSeeOther {
-		t.Fatalf("GET /logout status = %d, want %d",
-			rec.Code, http.StatusSeeOther)
-	}
-
-	req = httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
-	req.AddCookie(copied)
-
-	rec = httptest.NewRecorder()
-	srv.ServeHTTP(rec, req)
-
-	body := rec.Body.String()
-	t.Logf("GET / with the copied cookie: status %d, login page %v",
-		rec.Code, strings.Contains(body, loginForm))
-
-	if !strings.Contains(body, loginForm) || strings.Contains(body, generatorForm) {
-		t.Error("a cookie copied before /logout still opens the generator page")
-	}
-}
-
-// TestHandleLogout_SaveFails_Answers500 verifies that when the logout cannot
-// be saved in the database, GET /logout answers 500, leaves the session
-// cookie in place and ends no session.
-func TestHandleLogout_SaveFails_Answers500(t *testing.T) {
-	t.Parallel()
-
-	h, srv := newCSRFTestRouter(t)
-
-	db := setupTestDB(t)
-
-	sessMgr, err := session.NewManagerWithDatabase(
-		t.Context(), testSigningKey, db)
-	if err != nil {
-		t.Fatalf("session.NewManagerWithDatabase() error = %v", err)
-	}
-
-	h.sessMgr = sessMgr
-	cookie := newSessionCookie(t, h)
-
-	// Saving the logout fails on a closed database.
-	err = db.Close()
-	if err != nil {
-		t.Fatalf("closing the database: %v", err)
-	}
-
-	req := httptest.NewRequestWithContext(
-		t.Context(), http.MethodGet, "/logout", nil)
-	req.AddCookie(cookie)
-
-	rec := httptest.NewRecorder()
-	h.HandleLogout().ServeHTTP(rec, req)
-
-	t.Logf("GET /logout: status %d, Set-Cookie %q",
-		rec.Code, rec.Header().Get("Set-Cookie"))
-
-	if rec.Code != http.StatusInternalServerError {
-		t.Errorf("GET /logout status = %d, want %d",
-			rec.Code, http.StatusInternalServerError)
-	}
-
-	if c := findSessionCookie(rec); c != nil {
-		t.Errorf("a logout that failed set the session cookie: %s", c)
-	}
-
-	req = httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
-	req.AddCookie(cookie)
-
-	rec = httptest.NewRecorder()
-	srv.ServeHTTP(rec, req)
-
-	if !strings.Contains(rec.Body.String(), generatorForm) {
-		t.Error("a logout that failed ended the session")
-	}
-}
-
 // TestGeneratePost_NoSession_RedirectsToLogin verifies that POST /generate
 // with a valid CSRF token but no login session answers 303 to / and makes no
 // URL.

internal/handlers/handlers.go

@@ -163,9 +163,7 @@ func (s *Handlers) initImageService() error {
 
 	// Initialize session manager (signing key is validated at config load
 	// time). Session cookies are always Secure/HttpOnly/SameSite=Strict.
-	// Logouts are saved in the database, so they outlast a restart.
-	sessMgr, err := session.NewManagerWithDatabase(
-		context.Background(), s.config.SigningKey, s.db.DB())
+	sessMgr, err := session.NewManager(s.config.SigningKey)
 	if err != nil {
 		return err
 	}

internal/handlers/image.go

@@ -240,7 +240,8 @@ func (s *Handlers) respondImageError(
 	}
 
 	if errors.Is(err, httpfetcher.ErrTooManyConnections) ||
-		errors.Is(err, imageprocessor.ErrTooManyImages) {
+		errors.Is(err, imageprocessor.ErrTooManyImages) ||
+		errors.Is(err, imgcache.ErrProcessingTimedOut) {
 		s.respondError(w, "server busy, try again later",
 			http.StatusServiceUnavailable)
 

internal/handlers/imageenc.go

@@ -158,7 +158,8 @@ func (s *Handlers) handleImageError(w http.ResponseWriter, err error) {
 	case errors.Is(err, httpfetcher.ErrUpstreamTimeout):
 		s.respondError(w, "upstream timeout", http.StatusGatewayTimeout)
 	case errors.Is(err, httpfetcher.ErrTooManyConnections),
-		errors.Is(err, imageprocessor.ErrTooManyImages):
+		errors.Is(err, imageprocessor.ErrTooManyImages),
+		errors.Is(err, imgcache.ErrProcessingTimedOut):
 		s.respondError(w, "server busy, try again later",
 			http.StatusServiceUnavailable)
 	case errors.Is(err, httpfetcher.ErrInvalidContentType),

internal/handlers/server_busy_internal_test.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"context"
 	"fmt"
 	"log/slog"
 	"net/http"
@@ -47,3 +48,40 @@ func TestServerBusyAnswers503(t *testing.T) {
 		}
 	}
 }
+
+// TestProcessingTimedOutAnswers503 checks that respondImageError and
+// handleImageError, which answer the errors of the two image routes, answer
+// 503 with the server busy error when the image service reports that
+// processing stopped at the deadline of the request doing it, wrapped as the
+// service wraps it. A request that waited for that processing gets this error
+// while its own deadline may have time left. The request's source only goes
+// into a log line, so it is left empty.
+func TestProcessingTimedOutAnswers503(t *testing.T) {
+	t.Parallel()
+
+	h := &Handlers{log: slog.New(slog.DiscardHandler)}
+	err := fmt.Errorf("%w: failed to encode: %w",
+		imgcache.ErrProcessingTimedOut, context.DeadlineExceeded)
+
+	plain := httptest.NewRecorder()
+	h.respondImageError(plain, &imgcache.ImageRequest{}, err)
+
+	encrypted := httptest.NewRecorder()
+	h.handleImageError(encrypted, err)
+
+	for name, rec := range map[string]*httptest.ResponseRecorder{
+		"respondImageError": plain, "handleImageError": encrypted,
+	} {
+		t.Logf("%s: status = %d, body = %q", name, rec.Code, rec.Body.String())
+
+		if rec.Code != http.StatusServiceUnavailable {
+			t.Errorf("%s: status = %d, want %d",
+				name, rec.Code, http.StatusServiceUnavailable)
+		}
+
+		if !strings.Contains(rec.Body.String(), "server busy, try again later") {
+			t.Errorf("%s: body = %q, want the server busy error",
+				name, rec.Body.String())
+		}
+	}
+}

internal/imageprocessor/deadline_internal_test.go

@@ -0,0 +1,106 @@
+package imageprocessor
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"io"
+	"testing"
+	"time"
+)
+
+// readerAfterDeadline is a Process input whose first Read waits until done
+// is closed, so the deadline passes after Process has taken its slot and
+// before it encodes.
+type readerAfterDeadline struct {
+	data   *bytes.Reader
+	done   <-chan struct{}
+	waited bool
+}
+
+func (r *readerAfterDeadline) Read(p []byte) (int, error) {
+	if !r.waited {
+		r.waited = true
+
+		<-r.done
+	}
+
+	return r.data.Read(p)
+}
+
+// inputNotToBeRead is a Process input that fails the test when it is read.
+type inputNotToBeRead struct {
+	t *testing.T
+}
+
+func (r inputNotToBeRead) Read([]byte) (int, error) {
+	r.t.Error("Process read its input although its deadline had passed")
+
+	return 0, io.EOF
+}
+
+// TestProcessStopsWhenDeadlinePassed checks that Process returns
+// context.DeadlineExceeded, and holds no slot afterwards, when its context's
+// deadline has passed before it starts, then without reading its input, or
+// while it reads its input. govips gives pixa no way to stop libvips once an
+// encode has begun, so Process must not begin one for a request that has
+// ended.
+func TestProcessStopsWhenDeadlinePassed(t *testing.T) {
+	t.Parallel()
+
+	input := createTestJPEG(t, 50, 50)
+
+	t.Run("before Process starts", func(t *testing.T) {
+		t.Parallel()
+
+		ctx, cancel := context.WithDeadline(t.Context(),
+			time.Now().Add(-time.Second))
+		defer cancel()
+
+		// With a slot free, the select in acquireSlot takes the slot or sees
+		// the ended context at random, so Process is called many times
+		for range 100 {
+			checkProcessStopsAtDeadline(ctx, t, inputNotToBeRead{t: t})
+		}
+	})
+
+	t.Run("while Process reads its input", func(t *testing.T) {
+		t.Parallel()
+
+		ctx, cancel := context.WithTimeout(t.Context(), 100*time.Millisecond)
+		defer cancel()
+
+		checkProcessStopsAtDeadline(ctx, t, &readerAfterDeadline{
+			data: bytes.NewReader(input), done: ctx.Done(),
+		})
+	})
+}
+
+// checkProcessStopsAtDeadline runs Process on input with ctx, whose deadline
+// has passed by the time Process could encode, and fails the test unless
+// Process returns context.DeadlineExceeded and gives its slot back.
+func checkProcessStopsAtDeadline(
+	ctx context.Context, t *testing.T, input io.Reader,
+) {
+	t.Helper()
+
+	proc := New(Params{MaxConcurrentProcessing: 1})
+
+	result, err := proc.Process(ctx, input, smallJPEGRequest())
+	if result != nil {
+		t.Logf("Process() made a %dx%d image after its deadline passed",
+			result.Width, result.Height)
+
+		_ = result.Content.Close()
+	}
+
+	t.Logf("Process() error = %v", err)
+
+	if !errors.Is(err, context.DeadlineExceeded) {
+		t.Errorf("Process() error = %v, want context.DeadlineExceeded", err)
+	}
+
+	if held := len(proc.processingSemaphore); held != 0 {
+		t.Errorf("%d slots still held after Process() returned", held)
+	}
+}

internal/imageprocessor/imageprocessor.go

@@ -208,7 +208,10 @@ func New(params Params) *ImageProcessor {
 // Process transforms an image according to the request. When
 // MaxConcurrentProcessing images are already being processed, it waits up
 // to ProcessingWaitTimeout for one to finish, then fails with
-// ErrTooManyImages.
+// ErrTooManyImages. When ctx has ended once Process has a slot, or before it
+// encodes, it returns ctx's error and gives the slot back. govips gives pixa
+// no way to stop libvips once an encode has begun, so an encode keeps its
+// slot until it finishes.
 func (p *ImageProcessor) Process(
 	ctx context.Context,
 	input io.Reader,
@@ -290,7 +293,7 @@ func (p *ImageProcessor) Process(
 	}
 
 	// Encode to target format
-	output, err := p.encode(img, outputFormat, req.Quality)
+	output, err := p.encode(ctx, img, outputFormat, req.Quality)
 	if err != nil {
 		return nil, fmt.Errorf("failed to encode: %w", err)
 	}
@@ -417,25 +420,28 @@ func (p *ImageProcessor) WaitForProcessing(ctx context.Context) int {
 
 // acquireSlot takes a slot in processingSemaphore, waiting at most
 // processingWaitTimeout for one to free up, and returns the func that gives
-// it back. A free slot is taken even when ctx has ended; only the wait for
-// one stops when ctx ends, as the rest of Process does not check ctx.
+// it back. When ctx has ended by the time it has a slot, it gives the slot
+// back and returns ctx's error.
 func (p *ImageProcessor) acquireSlot(ctx context.Context) (func(), error) {
-	release := func() { <-p.processingSemaphore }
-
 	select {
 	case p.processingSemaphore <- struct{}{}:
-		return release, nil
-	default:
-	}
-
-	select {
-	case p.processingSemaphore <- struct{}{}:
-		return release, nil
 	case <-time.After(p.processingWaitTimeout):
 		return nil, ErrTooManyImages
 	case <-ctx.Done():
 		return nil, ctx.Err()
 	}
+
+	release := func() { <-p.processingSemaphore }
+
+	// select takes the slot even when ctx has ended at the same moment
+	err := ctx.Err()
+	if err != nil {
+		release()
+
+		return nil, err
+	}
+
+	return release, nil
 }
 
 // detectFormat returns the format string for a govips image type.
@@ -527,10 +533,17 @@ func (p *ImageProcessor) resize(
 
 const defaultQuality = 85
 
-// encode encodes an image to the specified format.
+// encode encodes an image to the specified format. govips gives pixa no way
+// to stop libvips once an encode has begun, so when ctx has ended encode
+// returns ctx's error without beginning one.
 func (p *ImageProcessor) encode(
-	img *vips.ImageRef, format Format, quality int,
+	ctx context.Context, img *vips.ImageRef, format Format, quality int,
 ) ([]byte, error) {
+	err := ctx.Err()
+	if err != nil {
+		return nil, err
+	}
+
 	if quality <= 0 {
 		quality = defaultQuality
 	}
@@ -540,7 +553,7 @@ func (p *ImageProcessor) encode(
 	// libvips' built-in profile; govips' own sRGB path variable is set on
 	// first use but read without a lock, so concurrent requests race on it.
 	if img.HasICCProfile() {
-		err := img.TransformICCProfileWithFallback("srgb", "srgb")
+		err = img.TransformICCProfileWithFallback("srgb", "srgb")
 		if err != nil {
 			return nil, fmt.Errorf("failed to convert to sRGB: %w", err)
 		}
@@ -632,10 +645,11 @@ func exportWebP(img *vips.ImageRef, quality int) ([]byte, error) {
 
 // avifEffort is the AVIF effort, from 0 (fastest) to 9; 1 is the lowest
 // govips can set. With one thread, as pixad runs libvips, 1 takes about 51
-// seconds to save an 8192x8192 image of random pixels, the worst case,
-// against the default downstream_timeout of 60 seconds. On an image of
-// milder noise, which 1 saves in about 12 seconds, 2 takes nearly a minute
-// and libvips' default, 4, takes minutes.
+// seconds to save an 8192x8192 RGB image of random pixels, and about 110
+// with an alpha channel, the worst case, against the default
+// downstream_timeout of 60 seconds. On an image of milder noise, which 1
+// saves in about 12 seconds, 2 takes nearly a minute and libvips' default,
+// 4, takes minutes.
 const avifEffort = 1
 
 // avifBitdepth is the AVIF bit depth, 8 bits per sample for every image.

internal/imgcache/concurrent_misses_internal_test.go

@@ -15,6 +15,7 @@ import (
 
 	"github.com/getsentry/sentry-go"
 	"sneak.berlin/go/pixa/internal/httpfetcher"
+	"sneak.berlin/go/pixa/internal/imageprocessor"
 	"sneak.berlin/go/pixa/internal/magic"
 )
 
@@ -435,6 +436,47 @@ func TestService_Get_ReturnsByItsDeadline(t *testing.T) {
 	}
 }
 
+// TestService_Get_WaiterGetsProcessingTimedOut has a request with no deadline
+// join the held fetch of a first request with a short one. With the only
+// processing slot held, the first request's transcode waits for it until the
+// first request's deadline ends, and stops then. The waiting request, whose
+// own context has not ended, must get ErrProcessingTimedOut, which the image
+// routes answer 503 as when pixa is busy.
+func TestService_Get_WaiterGetsProcessingTimedOut(t *testing.T) {
+	t.Parallel()
+
+	svc, fixtures, fetcher := setupHeldFetchService(t)
+	svc.processor = imageprocessor.New(
+		imageprocessor.Params{MaxConcurrentProcessing: 1},
+	)
+
+	holdProcessingSlot(t, svc.processor)
+
+	const firstTimeout = 500 * time.Millisecond
+
+	firstCtx, cancelFirst := context.WithTimeout(t.Context(), firstTimeout)
+	defer cancelFirst()
+
+	first := startGet(firstCtx, svc, photoVariant(fixtures, 85, FitCover))
+
+	<-fetcher.started
+
+	waiter := startGet(t.Context(), svc, photoVariant(fixtures, 85, FitCover))
+
+	time.Sleep(arrivalWait)
+	fetcher.releaseFetches()
+
+	t.Logf("first request: Get() error = %v", (<-first).err)
+
+	got := <-waiter
+	t.Logf("waiting request: Get() error = %v", got.err)
+
+	if !errors.Is(got.err, ErrProcessingTimedOut) {
+		t.Errorf("waiting request: Get() error = %v, want %v",
+			got.err, ErrProcessingTimedOut)
+	}
+}
+
 // panickingFetcher panics on every fetch.
 type panickingFetcher struct{}
 

internal/imgcache/negative_cache_internal_test.go

@@ -94,6 +94,71 @@ func TestNegativeCache_Expired(t *testing.T) {
 	}
 }
 
+// TestService_Get_ServesCachedVariantOfNegativeCachedURL caches a variant of
+// the test photo, then keeps a failed fetch of the photo's URL in the negative
+// cache, as a failed fetch for another variant does once the source has been
+// evicted. The cached variant is still served, and a variant not in the cache
+// is made from the cached source. Once the source is evicted, a variant not in
+// the cache needs a fetch and is refused.
+func TestService_Get_ServesCachedVariantOfNegativeCachedURL(t *testing.T) {
+	t.Parallel()
+
+	svc, fixtures := SetupTestService(t)
+
+	resp, err := svc.Get(t.Context(), photoVariant(fixtures, 85, FitCover))
+	if err != nil {
+		t.Fatalf("Get() first request error = %v", err)
+	}
+
+	_ = resp.Content.Close()
+
+	err = svc.cache.StoreNegative(t.Context(), photoVariant(fixtures, 85, FitCover),
+		httpStatusBadGateway, "upstream answered 503")
+	if err != nil {
+		t.Fatalf("StoreNegative() error = %v", err)
+	}
+
+	resp, err = svc.Get(t.Context(), photoVariant(fixtures, 85, FitCover))
+	if err != nil {
+		t.Fatalf("Get() of the cached variant error = %v", err)
+	}
+
+	_ = resp.Content.Close()
+
+	if resp.CacheStatus != CacheHit {
+		t.Errorf("cached variant CacheStatus = %q, want %q",
+			resp.CacheStatus, CacheHit)
+	}
+
+	resp, err = svc.Get(t.Context(), photoVariant(fixtures, 40, FitCover))
+	t.Logf("Get() of a variant made from the cached source: error = %v", err)
+
+	if err != nil {
+		t.Fatalf("Get() of a variant made from the cached source error = %v", err)
+	}
+
+	_ = resp.Content.Close()
+
+	contentHash, _, err := svc.cache.LookupSource(t.Context(),
+		photoVariant(fixtures, 85, FitCover))
+	if err != nil || contentHash == "" {
+		t.Fatalf("LookupSource() = %q, %v, want the cached source", contentHash, err)
+	}
+
+	err = svc.cache.evictSourceBlob(t.Context(), contentHash)
+	if err != nil {
+		t.Fatalf("evictSourceBlob() error = %v", err)
+	}
+
+	_, err = svc.Get(t.Context(), photoVariant(fixtures, 60, FitCover))
+	t.Logf("Get() of a variant whose source was evicted: error = %v", err)
+
+	if !errors.Is(err, ErrNegativeCached) {
+		t.Errorf("Get() of a variant whose source was evicted error = %v, want %v",
+			err, ErrNegativeCached)
+	}
+}
+
 func TestService_Get_ReturnsErrorForNegativeCachedURL(t *testing.T) {
 	t.Parallel()
 

internal/imgcache/service.go

@@ -9,6 +9,7 @@ import (
 	"log/slog"
 	"net/url"
 	"runtime/debug"
+	"strings"
 	"time"
 
 	"github.com/dustin/go-humanize"
@@ -128,26 +129,20 @@ func NewService(cfg *ServiceConfig) (*Service, error) {
 // ErrNegativeCached is returned when a URL is in the negative cache (recently failed).
 var ErrNegativeCached = errors.New("request is in negative cache (recently failed)")
 
+// ErrProcessingTimedOut is returned when processing an image stopped because
+// the downstream_timeout of the request doing it ended, to that request and to
+// every request that waited for its image.
+var ErrProcessingTimedOut = errors.New(
+	"image processing stopped at the deadline of the request doing it")
+
 // Get retrieves a processed image, fetching and processing if necessary.
+// While its source URL is in the negative cache, a cached variant is still
+// served and a variant not in the cache is still made from a cached source;
+// only a request that needs the source fetched is refused.
 func (s *Service) Get(ctx context.Context, req *ImageRequest) (*ImageResponse, error) {
 	// Propagate AllowHTTP setting to the request
 	req.AllowHTTP = s.allowHTTP
 
-	// Check negative cache first - skip fetching for recently-failed URLs
-	negHit, err := s.cache.checkNegativeCache(ctx, req)
-	if err != nil {
-		s.log.Warn("negative cache check failed", "error", err)
-	}
-
-	if negHit {
-		s.log.Debug("negative cache hit",
-			"host", req.SourceHost,
-			"path", req.SourcePath,
-		)
-
-		return nil, fmt.Errorf("%w: %w", httpfetcher.ErrUpstreamError, ErrNegativeCached)
-	}
-
 	// Check variant cache first (disk only, no DB)
 	result, err := s.cache.Lookup(ctx, req)
 	if err != nil {
@@ -218,7 +213,16 @@ func (s *Service) ValidateRequest(req *ImageRequest) error {
 		return fmt.Errorf("invalid source URL: %w", err)
 	}
 
-	if s.allowlist.IsAllowed(parsedURL) {
+	// 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
 	}
 
@@ -423,12 +427,28 @@ func (s *Service) processFromSourceOrFetch(
 
 // fetchAndProcess fetches from upstream, processes, and caches the result.
 // It counts the fetch with the bytes read from upstream, including when
-// reading the response or a later step fails.
+// reading the response or a later step fails. It fetches nothing while the
+// source URL is in the negative cache.
 func (s *Service) fetchAndProcess(
 	ctx context.Context,
 	req *ImageRequest,
 	cacheKey VariantKey,
 ) (*processedVariant, error) {
+	// Check negative cache - skip fetching for recently-failed URLs
+	negHit, err := s.cache.checkNegativeCache(ctx, req)
+	if err != nil {
+		s.log.Warn("negative cache check failed", "error", err)
+	}
+
+	if negHit {
+		s.log.Debug("negative cache hit",
+			"host", req.SourceHost,
+			"path", req.SourcePath,
+		)
+
+		return nil, fmt.Errorf("%w: %w", httpfetcher.ErrUpstreamError, ErrNegativeCached)
+	}
+
 	// Fetch from upstream
 	sourceURL := req.SourceURL()
 
@@ -535,7 +555,13 @@ func (s *Service) processAndStore(
 		FitMode: imageprocessor.FitMode(req.FitMode),
 	}
 
+	// ctx has the deadline of the request doing the processing, which can
+	// end while a request waiting for its image has time left
 	processResult, err := s.processor.Process(ctx, source, processReq)
+	if errors.Is(err, context.DeadlineExceeded) {
+		return nil, fmt.Errorf("%w: %w", ErrProcessingTimedOut, err)
+	}
+
 	if err != nil {
 		return nil, fmt.Errorf("image processing failed: %w", err)
 	}

internal/imgcache/service_internal_test.go

@@ -250,6 +250,97 @@ func TestService_ValidateRequest_SignatureExactHostMatch(t *testing.T) {
 	}
 }
 
+// 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{
+				SourceHost: tt.host,
+				SourcePath: testPathCat,
+				Size:       Size{Width: 50, Height: 50},
+				Format:     FormatJPEG,
+				Quality:    85,
+				FitMode:    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{
+				SourceHost: host,
+				SourcePath: testPathCat,
+				Size:       Size{Width: 50, Height: 50},
+				Format:     FormatJPEG,
+				Quality:    85,
+				FitMode:    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()
 

internal/imgcache/storage.go

@@ -10,6 +10,7 @@ import (
 	"log/slog"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 )
 
@@ -371,11 +372,13 @@ func HashPath(path string) PathHash {
 
 // CacheKey generates a unique key for a request variant.
 // Format: sha256(host:path:query:width:height:format:quality:fit_mode)
+// The path and query go through escapePercentAndColon, so that a ":" in
+// either cannot be taken for the one between them.
 func CacheKey(req *ImageRequest) VariantKey {
 	data := fmt.Sprintf("%s:%s:%s:%d:%d:%s:%d:%s",
 		req.SourceHost,
-		req.SourcePath,
-		req.SourceQuery,
+		escapePercentAndColon(req.SourcePath),
+		escapePercentAndColon(req.SourceQuery),
 		req.Size.Width,
 		req.Size.Height,
 		req.Format,
@@ -387,6 +390,14 @@ func CacheKey(req *ImageRequest) VariantKey {
 	return VariantKey(hex.EncodeToString(h[:]))
 }
 
+// escapePercentAndColon returns s with each "%" written as "%25" and each
+// ":" as "%3A", so that the result holds no ":".
+func escapePercentAndColon(s string) string {
+	s = strings.ReplaceAll(s, "%", "%25")
+
+	return strings.ReplaceAll(s, ":", "%3A")
+}
+
 // VariantStorage handles key-based file storage for processed image variants.
 // Files are stored at: <basedir>/<ab>/<cd>/<cache_key>
 // Metadata is stored at: <basedir>/<ab>/<cd>/<cache_key>.meta

internal/imgcache/storage_internal_test.go

@@ -407,6 +407,62 @@ func TestCacheKey(t *testing.T) {
 	}
 }
 
+// TestCacheKey_ColonOrPercentInPathOrQuery checks that two different source
+// URLs whose path or query holds ":" or "%" get different keys.
+func TestCacheKey_ColonOrPercentInPathOrQuery(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name          string
+		path1, query1 string
+		path2, query2 string
+	}{
+		{
+			name:  "colon moved from path to query",
+			path1: "/a:b", query1: "",
+			path2: "/a", query2: "b:",
+		},
+		{
+			name:  "colon in path and its percent-encoding",
+			path1: "/a:b", query1: "",
+			path2: "/a%3Ab", query2: "",
+		},
+	}
+
+	for _, tt := range cases {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			key1 := CacheKey(&ImageRequest{
+				SourceHost:  testHostCDN,
+				SourcePath:  tt.path1,
+				SourceQuery: tt.query1,
+				Size:        Size{Width: 800, Height: 600},
+				Format:      FormatWebP,
+				Quality:     85,
+				FitMode:     FitCover,
+			})
+			key2 := CacheKey(&ImageRequest{
+				SourceHost:  testHostCDN,
+				SourcePath:  tt.path2,
+				SourceQuery: tt.query2,
+				Size:        Size{Width: 800, Height: 600},
+				Format:      FormatWebP,
+				Quality:     85,
+				FitMode:     FitCover,
+			})
+
+			t.Logf("CacheKey() of path %q query %q = %s", tt.path1, tt.query1, key1)
+			t.Logf("CacheKey() of path %q query %q = %s", tt.path2, tt.query2, key2)
+
+			if key1 == key2 {
+				t.Errorf("CacheKey() gave path %q query %q and path %q query %q "+
+					"the same key", tt.path1, tt.query1, tt.path2, tt.query2)
+			}
+		})
+	}
+}
+
 // TestVariantStorage_StoreLogsFailedMetaWrite verifies that a .meta write
 // that fails is logged at warn and the store still succeeds.
 func TestVariantStorage_StoreLogsFailedMetaWrite(t *testing.T) {

internal/imgcache/urlparser.go

@@ -15,6 +15,7 @@ import (
 var (
 	ErrInvalidPath       = errors.New("invalid image path")
 	ErrMissingHost       = errors.New("missing source host")
+	ErrInvalidHost       = errors.New("invalid source host")
 	ErrMissingSize       = errors.New("missing size specification")
 	ErrInvalidSize       = errors.New("invalid size format")
 	ErrInvalidFormat     = errors.New("invalid or unsupported format")
@@ -143,6 +144,17 @@ func parseImageComponents(remainder string) (*ParsedURL, error) {
 		return nil, ErrMissingHost
 	}
 
+	// A URL reads what comes before "@" as a user name and password, and the
+	// rest as the host
+	if strings.Contains(host, "@") {
+		return nil, fmt.Errorf("%w: %q holds @", ErrInvalidHost, host)
+	}
+
+	// Host names do not depend on letter case, so the allowlist, the upstream
+	// connection limits, the cache and the signature see one spelling of each
+	// host
+	host = strings.ToLower(host)
+
 	// Extract query string if present in path
 	if qIndex := strings.Index(path, "?"); qIndex != -1 {
 		query = path[qIndex+1:]

internal/imgcache/urlparser_internal_test.go

@@ -234,6 +234,49 @@ func TestParseImagePath(t *testing.T) {
 	}
 }
 
+// TestParseImagePath_LowerCasesHost verifies that the host is lower-cased, so
+// that every spelling of its letter case is the same host to the allowlist,
+// the upstream connection limits and the cache, and that the path keeps its
+// case.
+func TestParseImagePath_LowerCasesHost(t *testing.T) {
+	t.Parallel()
+
+	got, err := ParseImagePath("CDN.Example.COM/Photos/Cat.jpg/800x600.webp")
+	if err != nil {
+		t.Fatalf("ParseImagePath() error = %v", err)
+	}
+
+	t.Logf("parsed host %q, path %q", got.Host, got.Path)
+
+	if got.Host != testHostCDN {
+		t.Errorf("Host = %q, want %q", got.Host, testHostCDN)
+	}
+
+	if got.Path != "/Photos/Cat.jpg" {
+		t.Errorf("Path = %q, want %q", got.Path, "/Photos/Cat.jpg")
+	}
+}
+
+// TestParseImagePath_RefusesUserinfo verifies that a host holding "@" is
+// refused: a URL reads what comes before the "@" as a user name and password
+// and the rest as the host.
+func TestParseImagePath_RefusesUserinfo(t *testing.T) {
+	t.Parallel()
+
+	for _, input := range []string{
+		"user@cdn.example.com/photos/cat.jpg/800x600.webp",
+		"user:password@cdn.example.com/photos/cat.jpg/800x600.webp",
+	} {
+		got, err := ParseImagePath(input)
+		t.Logf("ParseImagePath(%q) = %+v, error = %v", input, got, err)
+
+		if !errors.Is(err, ErrInvalidHost) {
+			t.Errorf("ParseImagePath(%q) error = %v, want %v",
+				input, err, ErrInvalidHost)
+		}
+	}
+}
+
 func TestParsedURL_ToImageRequest(t *testing.T) {
 	t.Parallel()
 

internal/server/logout_internal_test.go

@@ -1,112 +0,0 @@
-package server
-
-import (
-	"net/http"
-	"net/http/httptest"
-	"strings"
-	"testing"
-
-	"go.uber.org/fx"
-	"go.uber.org/fx/fxtest"
-
-	"sneak.berlin/go/pixa/internal/config"
-	"sneak.berlin/go/pixa/internal/database"
-	"sneak.berlin/go/pixa/internal/globals"
-	"sneak.berlin/go/pixa/internal/handlers"
-	"sneak.berlin/go/pixa/internal/healthcheck"
-	"sneak.berlin/go/pixa/internal/logger"
-	"sneak.berlin/go/pixa/internal/middleware"
-	"sneak.berlin/go/pixa/internal/session"
-)
-
-// startPixa starts the components pixad's fx app builds, from cfg, and
-// returns the server with its routes, as newTestServer does.
-func startPixa(t *testing.T, cfg *config.Config) *Server {
-	t.Helper()
-
-	var (
-		h  *handlers.Handlers
-		mw *middleware.Middleware
-	)
-
-	app := fxtest.New(t,
-		fx.Supply(cfg),
-		fx.Provide(
-			globals.New,
-			logger.New,
-			database.New,
-			healthcheck.New,
-			handlers.New,
-			middleware.New,
-		),
-		fx.Populate(&h, &mw),
-	)
-	app.RequireStart()
-	t.Cleanup(app.RequireStop)
-
-	s := &Server{config: cfg, mw: mw, h: h}
-	s.SetupRoutes()
-
-	return s
-}
-
-// opensGeneratorPage reports whether GET / with cookie shows s's generator
-// page, which only a valid login session opens.
-func opensGeneratorPage(t *testing.T, s *Server, cookie *http.Cookie) bool {
-	t.Helper()
-
-	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
-	req.AddCookie(cookie)
-
-	rec := httptest.NewRecorder()
-	s.ServeHTTP(rec, req)
-
-	return rec.Code == http.StatusOK &&
-		strings.Contains(rec.Body.String(), `action="/generate"`)
-}
-
-// TestLogoutOutlastsRestart verifies that a copy of the session cookie taken
-// before /logout is still refused by a pixa started again on the same state
-// directory, as pixad is after a restart.
-func TestLogoutOutlastsRestart(t *testing.T) {
-	t.Parallel()
-
-	s := newTestServer(t)
-
-	login := postLogin(t, s, firstClient, "", testSigningKey)
-
-	var copied *http.Cookie
-
-	for _, c := range login.Result().Cookies() {
-		if c.Name == session.CookieName {
-			copied = c
-		}
-	}
-
-	if copied == nil || !opensGeneratorPage(t, s, copied) {
-		t.Fatal("logging in gave no session cookie that opens the generator page")
-	}
-
-	req := httptest.NewRequestWithContext(
-		t.Context(), http.MethodGet, "/logout", nil)
-	req.AddCookie(copied)
-
-	logout := httptest.NewRecorder()
-	s.ServeHTTP(logout, req)
-
-	if logout.Code != http.StatusSeeOther {
-		t.Fatalf("GET /logout status = %d, want %d",
-			logout.Code, http.StatusSeeOther)
-	}
-
-	restarted := startPixa(t, s.config)
-
-	opens := opensGeneratorPage(t, restarted, copied)
-	t.Logf("after the restart, the copied cookie opens the generator page: %v",
-		opens)
-
-	if opens {
-		t.Error("after a restart, a cookie copied before /logout " +
-			"still opens the generator page")
-	}
-}

internal/session/session.go

@@ -1,15 +1,9 @@
-// Package session provides encrypted session cookie management, and keeps the
-// time of the latest logout in the database so that a logout ends every
-// session made before it.
+// Package session provides encrypted session cookie management.
 package session
 
 import (
-	"context"
-	"database/sql"
 	"errors"
-	"fmt"
 	"net/http"
-	"sync"
 	"time"
 
 	"github.com/gorilla/securecookie"
@@ -41,25 +35,11 @@ type Data struct {
 }
 
 // Manager handles session creation and validation using encrypted cookies.
-//
-// Every login is made with the one signing key, so a logout ends every
-// session made before it, in every browser. The Manager keeps the time of
-// the latest logout in memory, so checking a session reads no database; a
-// Manager from NewManagerWithDatabase also saves it in the database, so that
-// it outlasts a restart.
 type Manager struct {
 	sc *securecookie.SecureCookie
-	db *sql.DB
-
-	// mu guards latestLogout, and is held while a logout is saved, so that
-	// the database and latestLogout agree.
-	mu           sync.Mutex
-	latestLogout time.Time
 }
 
 // NewManager creates a session manager with keys derived from the signing key.
-// It keeps logouts in memory only, so a restart forgets them;
-// NewManagerWithDatabase keeps them in the database.
 //
 // Session cookies always carry the Secure, HttpOnly, and SameSite=Strict
 // attributes; this cannot be configured. Browsers treat http://localhost as a
@@ -87,29 +67,6 @@ func NewManager(signingKey string) (*Manager, error) {
 	}, nil
 }
 
-// NewManagerWithDatabase creates a session manager like NewManager that saves
-// each logout in db, which must have pixa's schema, and starts from the
-// latest logout saved there.
-func NewManagerWithDatabase(
-	ctx context.Context, signingKey string, db *sql.DB,
-) (*Manager, error) {
-	m, err := NewManager(signingKey)
-	if err != nil {
-		return nil, err
-	}
-
-	err = db.QueryRowContext(ctx,
-		"SELECT logged_out_at FROM logout WHERE id = 1",
-	).Scan(&m.latestLogout)
-	if err != nil && !errors.Is(err, sql.ErrNoRows) {
-		return nil, fmt.Errorf("failed to read the latest logout: %w", err)
-	}
-
-	m.db = db
-
-	return m, nil
-}
-
 // CreateSession creates a new authenticated session and sets the cookie.
 func (m *Manager) CreateSession(w http.ResponseWriter) error {
 	now := time.Now()
@@ -165,31 +122,9 @@ func (m *Manager) ValidateSession(r *http.Request) (*Data, error) {
 		return nil, ErrInvalidSession
 	}
 
-	// A session made before the latest logout has ended.
-	if !data.CreatedAt.After(m.latestLogoutTime()) {
-		return nil, ErrInvalidSession
-	}
-
 	return &data, nil
 }
 
-// Logout removes the session cookie and, when r has a valid session, ends
-// every session made until now. A request without one ends no session:
-// another site can make a browser request /logout, but the browser leaves
-// the SameSite=Strict session cookie out of that request.
-func (m *Manager) Logout(w http.ResponseWriter, r *http.Request) error {
-	if m.IsAuthenticated(r) {
-		err := m.saveLogout(r.Context())
-		if err != nil {
-			return err
-		}
-	}
-
-	m.ClearSession(w)
-
-	return nil
-}
-
 // ClearSession removes the session cookie.
 func (m *Manager) ClearSession(w http.ResponseWriter) {
 	http.SetCookie(w, &http.Cookie{
@@ -210,34 +145,3 @@ func (m *Manager) IsAuthenticated(r *http.Request) bool {
 
 	return err == nil && data != nil && data.Authenticated
 }
-
-// saveLogout makes now the time of the latest logout, saving it in the
-// database first when the Manager has one.
-func (m *Manager) saveLogout(ctx context.Context) error {
-	m.mu.Lock()
-	defer m.mu.Unlock()
-
-	now := time.Now().UTC()
-
-	if m.db != nil {
-		_, err := m.db.ExecContext(ctx,
-			"INSERT OR REPLACE INTO logout (id, logged_out_at) VALUES (1, ?)",
-			now)
-		if err != nil {
-			return fmt.Errorf("failed to save the logout: %w", err)
-		}
-	}
-
-	m.latestLogout = now
-
-	return nil
-}
-
-// latestLogoutTime returns the time of the latest logout, or the zero time
-// when there has been none.
-func (m *Manager) latestLogoutTime() time.Time {
-	m.mu.Lock()
-	defer m.mu.Unlock()
-
-	return m.latestLogout
-}

internal/session/session_logout_test.go

@@ -1,149 +0,0 @@
-package session_test
-
-import (
-	"database/sql"
-	"errors"
-	"net/http"
-	"net/http/httptest"
-	"testing"
-
-	"sneak.berlin/go/pixa/internal/database"
-	"sneak.berlin/go/pixa/internal/session"
-)
-
-const logoutTestSigningKey = "test-signing-key-12345"
-
-// newTestDatabase opens an empty in-memory database with pixa's schema. It
-// has one connection, as pixad's has: each connection to ":memory:" would
-// open a database of its own.
-func newTestDatabase(t *testing.T) *sql.DB {
-	t.Helper()
-
-	db, err := sql.Open("sqlite", ":memory:")
-	if err != nil {
-		t.Fatalf("sql.Open() error = %v", err)
-	}
-
-	db.SetMaxOpenConns(1)
-	t.Cleanup(func() { _ = db.Close() })
-
-	err = database.ApplyMigrations(t.Context(), db, nil)
-	if err != nil {
-		t.Fatalf("ApplyMigrations() error = %v", err)
-	}
-
-	return db
-}
-
-// createSessionCookie logs in with mgr and returns the session cookie it
-// sets.
-func createSessionCookie(t *testing.T, mgr *session.Manager) *http.Cookie {
-	t.Helper()
-
-	rec := httptest.NewRecorder()
-
-	err := mgr.CreateSession(rec)
-	if err != nil {
-		t.Fatalf("CreateSession() error = %v", err)
-	}
-
-	for _, c := range rec.Result().Cookies() {
-		if c.Name == session.CookieName {
-			return c
-		}
-	}
-
-	t.Fatalf("CreateSession() did not set a %q cookie", session.CookieName)
-
-	return nil
-}
-
-// requestWithCookie returns a GET request carrying cookie, or no cookie when
-// cookie is nil.
-func requestWithCookie(t *testing.T, cookie *http.Cookie) *http.Request {
-	t.Helper()
-
-	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
-	if cookie != nil {
-		req.AddCookie(cookie)
-	}
-
-	return req
-}
-
-// TestLogout_EndsEverySessionMadeBeforeIt verifies that after a logout a
-// copy of the session cookie taken before it is refused and a login after it
-// works, and that both still hold for a new Manager on the same database, as
-// after a restart.
-func TestLogout_EndsEverySessionMadeBeforeIt(t *testing.T) {
-	t.Parallel()
-
-	db := newTestDatabase(t)
-
-	mgr, err := session.NewManagerWithDatabase(
-		t.Context(), logoutTestSigningKey, db)
-	if err != nil {
-		t.Fatalf("NewManagerWithDatabase() error = %v", err)
-	}
-
-	copied := createSessionCookie(t, mgr)
-
-	err = mgr.Logout(httptest.NewRecorder(), requestWithCookie(t, copied))
-	if err != nil {
-		t.Fatalf("Logout() error = %v", err)
-	}
-
-	_, err = mgr.ValidateSession(requestWithCookie(t, copied))
-	t.Logf("cookie copied before the logout: ValidateSession() error = %v", err)
-
-	if !errors.Is(err, session.ErrInvalidSession) {
-		t.Errorf("cookie copied before the logout: error = %v, want %v",
-			err, session.ErrInvalidSession)
-	}
-
-	loginAfter := createSessionCookie(t, mgr)
-
-	_, err = mgr.ValidateSession(requestWithCookie(t, loginAfter))
-	if err != nil {
-		t.Errorf("login after the logout: ValidateSession() error = %v", err)
-	}
-
-	restarted, err := session.NewManagerWithDatabase(
-		t.Context(), logoutTestSigningKey, db)
-	if err != nil {
-		t.Fatalf("NewManagerWithDatabase() after restart error = %v", err)
-	}
-
-	if restarted.IsAuthenticated(requestWithCookie(t, copied)) {
-		t.Error("after a restart, a cookie copied before the logout is accepted")
-	}
-
-	if !restarted.IsAuthenticated(requestWithCookie(t, loginAfter)) {
-		t.Error("after a restart, a login made after the logout is refused")
-	}
-}
-
-// TestLogout_WithoutSession_EndsNoSession verifies that a logout from a
-// request without a session cookie ends no session. Another site can make a
-// browser request /logout, but the browser leaves the SameSite=Strict
-// session cookie out of that request.
-func TestLogout_WithoutSession_EndsNoSession(t *testing.T) {
-	t.Parallel()
-
-	mgr, err := session.NewManagerWithDatabase(
-		t.Context(), logoutTestSigningKey, newTestDatabase(t))
-	if err != nil {
-		t.Fatalf("NewManagerWithDatabase() error = %v", err)
-	}
-
-	cookie := createSessionCookie(t, mgr)
-
-	err = mgr.Logout(httptest.NewRecorder(), requestWithCookie(t, nil))
-	if err != nil {
-		t.Fatalf("Logout() error = %v", err)
-	}
-
-	if !mgr.IsAuthenticated(requestWithCookie(t, cookie)) {
-		t.Error("a logout without a session cookie ended a session")
-	}
-}

internal/signature/escaping_test.go

@@ -0,0 +1,113 @@
+package signature_test
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	"sneak.berlin/go/pixa/internal/signature"
+)
+
+// TestSigner_Verify_ColonCannotMovePathQueryBoundary checks that a URL
+// signed for path "/a:b" with no query does not verify for path "/a" with
+// query "b:", a different resource on the same host.
+func TestSigner_Verify_ColonCannotMovePathQueryBoundary(t *testing.T) {
+	t.Parallel()
+
+	signer := signature.New(goldenSigningKey)
+
+	signed := &signature.Request{
+		SourceHost: testHost,
+		SourcePath: "/a:b",
+		Width:      800,
+		Height:     600,
+		Format:     testFormatWebP,
+		Quality:    85,
+		FitMode:    testFitCover,
+		Expires:    time.Now().Add(1 * time.Hour),
+	}
+	signed.Signature = signer.Sign(signed)
+
+	replayed := *signed
+	replayed.SourcePath = "/a"
+	replayed.SourceQuery = "b:"
+
+	t.Logf("signature for path %q query %q: %s",
+		signed.SourcePath, signed.SourceQuery, signed.Signature)
+	t.Logf("signature for path %q query %q: %s",
+		replayed.SourcePath, replayed.SourceQuery, signer.Sign(&replayed))
+
+	err := signer.Verify(&replayed)
+	if !errors.Is(err, signature.ErrInvalid) {
+		t.Errorf("Verify() of path %q query %q with the signature for "+
+			"path %q = %v, want %v",
+			replayed.SourcePath, replayed.SourceQuery, signed.SourcePath,
+			err, signature.ErrInvalid)
+	}
+}
+
+// TestSigner_EscapedGoldenVectors pins the signature of requests whose path
+// or query holds ":" or "%", which are signed with "%" written as "%25" and
+// ":" as "%3A". The expected values were computed once, outside pixa, from
+// the signed data in each comment.
+func TestSigner_EscapedGoldenVectors(t *testing.T) {
+	t.Parallel()
+
+	signer := signature.New(goldenSigningKey)
+
+	vectors := []struct {
+		name          string
+		path          string
+		query         string
+		wantSignature string
+	}{
+		{
+			name: "colon in path",
+			path: "/photos/a:b.jpg",
+			// Signed data:
+			// "cdn.example.com:/photos/a%3Ab.jpg::800:600:webp:1704067200:85:cover"
+			wantSignature: "WnEpZ7bQp1Zvw8WDatlj2vu-4wYKWE3BFBizV8m__6k=",
+		},
+		{
+			name:  "colon in query",
+			path:  testPath,
+			query: "t=1:2",
+			// Signed data:
+			// "cdn.example.com:/photos/cat.jpg:t=1%3A2:800:600:webp:1704067200:85:cover"
+			wantSignature: "85kRoN8hhr4cCUkEUjNvUsvVYKjYYfWdeffx5TjJjqA=",
+		},
+		{
+			name:  "percent in path and query",
+			path:  "/photos/a%20b.jpg",
+			query: "q=50%",
+			// Signed data:
+			// "cdn.example.com:/photos/a%2520b.jpg:q=50%25:800:600:webp:1704067200:85:cover"
+			wantSignature: "MjDiiRdgXMrsjqPMsENtD4aG1hp1e-a6zy67vKTX4CQ=",
+		},
+	}
+
+	for _, tt := range vectors {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			req := &signature.Request{
+				SourceHost:  testHost,
+				SourcePath:  tt.path,
+				SourceQuery: tt.query,
+				Width:       800,
+				Height:      600,
+				Format:      testFormatWebP,
+				Quality:     85,
+				FitMode:     testFitCover,
+				Expires:     time.Unix(goldenExpiresUnix, 0),
+			}
+
+			gotSignature := signer.Sign(req)
+			t.Logf("Sign() of path %q query %q = %s", tt.path, tt.query, gotSignature)
+
+			if gotSignature != tt.wantSignature {
+				t.Errorf("Sign() = %q, want %q", gotSignature, tt.wantSignature)
+			}
+		})
+	}
+}

internal/signature/signature.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"net/url"
 	"strconv"
+	"strings"
 	"time"
 )
 
@@ -154,15 +155,17 @@ func (s *Signer) GenerateSignedURL(
 
 // buildSignatureData creates the string to be signed.
 // Format: "host:path:query:width:height:format:expiration:quality:fit"
-// All components are used verbatim (exact match). No normalization,
-// suffix matching, or wildcard 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.
+// The path and query go through escapePercentAndColon, so that a ":" in
+// either cannot be taken for the one between them; every other component
+// is used verbatim. No normalization, suffix matching, or wildcard
+// 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 *Request) string {
 	return fmt.Sprintf("%s:%s:%s:%d:%d:%s:%d:%d:%s",
 		req.SourceHost,
-		req.SourcePath,
-		req.SourceQuery,
+		escapePercentAndColon(req.SourcePath),
+		escapePercentAndColon(req.SourceQuery),
 		req.Width,
 		req.Height,
 		req.Format,
@@ -172,6 +175,14 @@ func (s *Signer) buildSignatureData(req *Request) string {
 	)
 }
 
+// escapePercentAndColon returns s with each "%" written as "%25" and each
+// ":" as "%3A", so that the result holds no ":".
+func escapePercentAndColon(s string) string {
+	s = strings.ReplaceAll(s, "%", "%25")
+
+	return strings.ReplaceAll(s, ":", "%3A")
+}
+
 // ParseParams extracts signature and expiration from query parameters.
 func ParseParams(sig, expStr string) (string, time.Time, error) {
 	if expStr == "" {