fix: validate dimensions and fit mode on encrypted URLs (closes #62)

The encrypted /v1/e/ route built its image request straight from the
decrypted payload, so a token could request an over-limit dimension
(reaching libvips and exhausting memory) or an unknown fit mode
(surfacing as a 500 from the processor). The token generator discarded
every strconv.Atoi error, silently turning non-numeric width, height,
quality, or ttl into 0 and applying no upper bound on dimensions.

Add a shared ValidateImageRequest in internal/imgcache enforcing the
MaxDimension bound and ValidateFitMode, and apply it on both the plain
image route and the encrypted route so both reject an over-limit size or
an unrecognized fit mode with 400. The generator now parses each numeric
field explicitly and returns 400 naming the field for non-numeric or
out-of-range input, with width and height bounds-checked so an unusable
token cannot be minted.

Model: opus-4-8

README.md

@@ -122,19 +122,6 @@ Configured via YAML file (`--config`). Key settings:
 
 - `access_control_allow_origin` — CORS origin
 - `allowlist_hosts` — list of allowed upstream hosts
-- `blocked_networks` — list of CIDR ranges to refuse for SSRF protection,
-  added to the always-enforced built-in ranges (loopback, private,
-  link-local, CGNAT, benchmark, NAT64, and the like); an invalid CIDR
-  aborts startup
-- `trusted_proxies` — list of CIDR ranges of the reverse proxies in front
-  of pixa. `X-Forwarded-For` is believed only when the direct peer falls
-  inside one of these ranges; the logged and login-recorded client
-  address is then the rightmost forwarded entry that is not itself a
-  trusted proxy. Otherwise the direct peer address is used and the header
-  is ignored, so a client connecting directly cannot spoof its address.
-  Omitted or empty trusts no one; an invalid CIDR aborts startup. Set
-  this to your proxy's address range when deploying behind a reverse
-  proxy
 - `upstream_fetch_timeout` — timeout for origin requests
 - `upstream_max_response_size` — max origin response size
 - `downstream_timeout` — client response timeout

TODO.md

@@ -25,31 +25,21 @@ The disk cache is now size-bounded with LRU eviction
 
 # Next Step
 
-P1: rate limit global concurrent upstream fetches to prevent resource
-exhaustion
+P1: implement blocked networks configuration to extend SSRF protection
 
 # Completed Steps
 
-- 2026-09-21 trusted-proxy client IP resolution (closes #94): a
-  `trusted_proxies` config key taking a list of CIDRs, parsed by the same
-  `net/netip` list parser as `blocked_networks` (an invalid entry aborts
-  startup naming the key and value; omitted or empty trusts no one); a new
-  `internal/clientip` package resolves the client address by honoring
-  `X-Forwarded-For` only when the direct peer is a trusted proxy, walking
-  the chain right-to-left to the rightmost non-proxy entry, so a client
-  connecting directly cannot spoof its address; the resolved address is
-  stored in the request context by a new middleware and used by the
-  request-logging middleware and the login-attempt logs in place of the
-  raw peer address; documented in `README.md` and `config.example.yml`.
-- 2026-09-21 blocked networks configuration extending SSRF protection: a
-  `blocked_networks` config key taking a list of CIDRs (parsed with
-  `net/netip`, an invalid entry aborts startup naming the key and value),
-  added to the built-in blocklist rather than replacing it; the built-in
-  ranges extended to CGNAT `100.64.0.0/10`, IETF protocol assignments
-  `192.0.0.0/24`, benchmark `198.18.0.0/15`, and NAT64 `64:ff9b::/96`
-  (IPv4-mapped forms covered); enforcement stays in the dial-time
-  re-resolution so the DNS-rebinding window remains closed; documented in
-  `README.md` and `config.example.yml`.
+- 2026-09-21 validate dimensions and fit mode on the encrypted-URL
+  route and the token generator (closes #62): added a shared
+  `ValidateImageRequest` in `internal/imgcache` enforcing the
+  `MaxDimension` bound and `ValidateFitMode`, applied by both the
+  `/v1/image/` and `/v1/e/` routes, so an over-limit size or an unknown
+  fit mode is a 400 rather than an out-of-memory or a 500 from the
+  processor; the URL generator now checks every numeric form field and
+  rejects a non-numeric or out-of-range `width`, `height`, `quality`,
+  or `ttl` with a 400 naming the field instead of coercing it to `0`,
+  and `width`/`height` are bounds-checked so an unusable token cannot be
+  minted
 - 2026-09-21 http.Server hardening (closes #92): added
   `HTTPReadHeaderTimeout` (10s, bounds the slowloris header dribble) and
   `HTTPIdleTimeout` (120s, bounds keep-alive reuse) alongside the
@@ -151,6 +141,8 @@ exhaustion
 
 # Future Steps
 
+- P1: rate limit global concurrent upstream fetches to prevent
+  resource exhaustion
 - P1: strip EXIF and other metadata from processed images (privacy)
 - P2: security
     - referer blacklist

config.example.yml

@@ -22,27 +22,6 @@ allowlist_hosts:
   - github.com
   - user-images.githubusercontent.com
 
-# Additional CIDR ranges to refuse when fetching upstream, extending the
-# SSRF protection. These are added to the always-enforced built-in ranges
-# (loopback, RFC 1918 private, link-local, CGNAT, benchmark, NAT64, and
-# similar), never replacing them. Each entry must be a valid CIDR in IPv4
-# or IPv6 form; an invalid entry aborts startup.
-# blocked_networks:
-#   - 100.64.0.0/10
-#   - 2001:db8::/32
-
-# CIDR ranges of the reverse proxies in front of pixa. X-Forwarded-For
-# is believed only when the direct peer is inside one of these ranges;
-# the client address in the access log and login records is then the
-# rightmost forwarded entry that is not itself a trusted proxy. A client
-# connecting directly (peer outside these ranges) cannot spoof its
-# address: the header is ignored and the peer address is used. Omitted or
-# empty trusts no one; an invalid CIDR aborts startup. Set this when
-# deploying behind a proxy.
-# trusted_proxies:
-#   - 10.0.0.0/8
-#   - 2001:db8::/32
-
 # Allow HTTP upstream (only for testing, always use HTTPS in production)
 allow_http: false
 

internal/clientip/clientip.go

@@ -1,119 +0,0 @@
-// Package clientip resolves the real client IP address of an HTTP request
-// when pixa runs behind a reverse proxy. Forwarding headers are believed
-// only when the immediate peer is a configured trusted proxy, so an
-// untrusted client cannot spoof its address by sending the header.
-package clientip
-
-import (
-	"context"
-	"net"
-	"net/netip"
-	"slices"
-	"strings"
-)
-
-// ForwardedForHeader is the request header carrying the proxy chain. It is
-// honored only when the immediate peer is a trusted proxy.
-const ForwardedForHeader = "X-Forwarded-For"
-
-// Resolver determines the client IP of a request against a fixed set of
-// trusted proxy networks.
-type Resolver struct {
-	trusted []netip.Prefix
-}
-
-// NewResolver returns a Resolver that trusts forwarding headers only from
-// peers inside the given CIDR ranges. A nil or empty list trusts no one,
-// so the peer address is always used.
-func NewResolver(trusted []netip.Prefix) *Resolver {
-	return &Resolver{trusted: trusted}
-}
-
-// Resolve returns the client IP for a request whose direct peer is
-// remoteAddr (a "host:port" string as in http.Request.RemoteAddr) and
-// whose X-Forwarded-For header lines are forwardedFor (as returned by
-// http.Header.Values). When the peer is not a trusted proxy, the peer
-// address is returned and the header is ignored entirely. When the peer is
-// trusted, the header is walked right to left and the first address that is
-// not itself a trusted proxy is returned; this is the client the outermost
-// trusted proxy observed, and entries an untrusted client may have prepended
-// sit to its left and are never reached.
-func (r *Resolver) Resolve(remoteAddr string, forwardedFor []string) string {
-	peer := hostOnly(remoteAddr)
-
-	peerAddr, err := netip.ParseAddr(peer)
-	if err != nil || !r.isTrusted(peerAddr) {
-		return peer
-	}
-
-	for _, hop := range slices.Backward(forwardedForChain(forwardedFor)) {
-		hopAddr, err := netip.ParseAddr(hop)
-		if err != nil || r.isTrusted(hopAddr) {
-			continue
-		}
-
-		return hopAddr.String()
-	}
-
-	return peerAddr.String()
-}
-
-// isTrusted reports whether addr falls inside one of the trusted proxy
-// ranges. Addresses are unmapped first so an IPv4-mapped IPv6 form matches
-// an IPv4 range, matching the fetcher's blocklist comparison.
-func (r *Resolver) isTrusted(addr netip.Addr) bool {
-	if !addr.IsValid() {
-		return false
-	}
-
-	unmapped := addr.Unmap()
-
-	return slices.ContainsFunc(r.trusted, func(prefix netip.Prefix) bool {
-		return prefix.Contains(unmapped)
-	})
-}
-
-// hostOnly strips the port from a "host:port" address. A value without a
-// port (already a bare host) is returned unchanged.
-func hostOnly(remoteAddr string) string {
-	host, _, err := net.SplitHostPort(remoteAddr)
-	if err != nil {
-		return remoteAddr
-	}
-
-	return host
-}
-
-// forwardedForChain flattens the comma-separated entries of every
-// X-Forwarded-For header line into a single ordered, trimmed list.
-func forwardedForChain(values []string) []string {
-	var chain []string
-
-	for _, value := range values {
-		for part := range strings.SplitSeq(value, ",") {
-			trimmed := strings.TrimSpace(part)
-			if trimmed != "" {
-				chain = append(chain, trimmed)
-			}
-		}
-	}
-
-	return chain
-}
-
-// contextKey is the private key type under which the resolved client IP is
-// stored in a request context.
-type contextKey struct{}
-
-// WithClientIP returns a copy of ctx carrying the resolved client IP.
-func WithClientIP(ctx context.Context, ip string) context.Context {
-	return context.WithValue(ctx, contextKey{}, ip)
-}
-
-// FromContext returns the resolved client IP stored in ctx, or an empty
-// string if none was set.
-func FromContext(ctx context.Context) string {
-	ip, _ := ctx.Value(contextKey{}).(string)
-
-	return ip
-}

internal/clientip/clientip_test.go

@@ -1,189 +0,0 @@
-package clientip_test
-
-import (
-	"net/netip"
-	"testing"
-
-	"sneak.berlin/go/pixa/internal/clientip"
-)
-
-// Addresses reused across the resolver cases.
-const (
-	trustedRangeV4 = "10.0.0.0/8"
-	forwardedV4    = "203.0.113.7"
-	untrustedV4    = "198.51.100.9"
-	trustedPeer    = "10.0.0.1:5000"
-)
-
-// mustPrefixes parses CIDR strings into prefixes for building a resolver.
-func mustPrefixes(t *testing.T, cidrs ...string) []netip.Prefix {
-	t.Helper()
-
-	prefixes := make([]netip.Prefix, 0, len(cidrs))
-
-	for _, c := range cidrs {
-		p, err := netip.ParsePrefix(c)
-		if err != nil {
-			t.Fatalf("netip.ParsePrefix(%q) error = %v", c, err)
-		}
-
-		prefixes = append(prefixes, p)
-	}
-
-	return prefixes
-}
-
-type resolveCase struct {
-	name         string
-	trusted      []string
-	remoteAddr   string
-	forwardedFor []string
-	want         string
-}
-
-// runResolveCases runs each case against a resolver built from its trusted
-// list and checks the resolved address.
-func runResolveCases(t *testing.T, cases []resolveCase) {
-	t.Helper()
-
-	for _, tt := range cases {
-		t.Run(tt.name, func(t *testing.T) {
-			t.Parallel()
-
-			r := clientip.NewResolver(mustPrefixes(t, tt.trusted...))
-
-			got := r.Resolve(tt.remoteAddr, tt.forwardedFor)
-			if got != tt.want {
-				t.Errorf("Resolve(%q, %v) = %q, want %q",
-					tt.remoteAddr, tt.forwardedFor, got, tt.want)
-			}
-		})
-	}
-}
-
-// TestResolvePeerTrust covers the trust decision on the direct peer: a
-// forwarded header is believed only from a trusted peer, and a client
-// connecting directly cannot spoof its address.
-func TestResolvePeerTrust(t *testing.T) {
-	t.Parallel()
-
-	runResolveCases(t, []resolveCase{
-		{
-			name:         "trusted peer honors forwarded client",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   trustedPeer,
-			forwardedFor: []string{forwardedV4},
-			want:         forwardedV4,
-		},
-		{
-			name:         "untrusted peer ignores forwarded header",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   untrustedV4 + ":33333",
-			forwardedFor: []string{forwardedV4},
-			want:         untrustedV4,
-		},
-		{
-			name:         "spoofed chain from untrusted peer cannot influence result",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   untrustedV4 + ":33333",
-			forwardedFor: []string{"1.2.3.4, 10.9.9.9, 127.0.0.1"},
-			want:         untrustedV4,
-		},
-		{
-			name:         "empty trusted list always uses peer",
-			trusted:      nil,
-			remoteAddr:   forwardedV4 + ":80",
-			forwardedFor: []string{"10.0.0.5"},
-			want:         forwardedV4,
-		},
-		{
-			name:         "trusted peer with no forwarded header uses peer",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   trustedPeer,
-			forwardedFor: nil,
-			want:         "10.0.0.1",
-		},
-		{
-			name:         "unparseable peer is returned unchanged",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   "garbage",
-			forwardedFor: []string{forwardedV4},
-			want:         "garbage",
-		},
-	})
-}
-
-// TestResolveChainWalk covers walking the X-Forwarded-For chain from a
-// trusted peer to the rightmost entry that is not itself a trusted proxy.
-func TestResolveChainWalk(t *testing.T) {
-	t.Parallel()
-
-	runResolveCases(t, []resolveCase{
-		{
-			name:         "rightmost untrusted entry across a mixed chain",
-			trusted:      []string{trustedRangeV4, "192.168.0.0/16"},
-			remoteAddr:   trustedPeer,
-			forwardedFor: []string{forwardedV4 + ", 192.168.1.1, 10.0.0.2"},
-			want:         forwardedV4,
-		},
-		{
-			name:         "spoofed client behind a trusted proxy is not believed",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   trustedPeer,
-			forwardedFor: []string{"1.2.3.4, " + untrustedV4},
-			want:         untrustedV4,
-		},
-		{
-			name:         "chain split across multiple header lines",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   trustedPeer,
-			forwardedFor: []string{forwardedV4, "10.0.0.2"},
-			want:         forwardedV4,
-		},
-		{
-			name:         "garbage entries are skipped",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   trustedPeer,
-			forwardedFor: []string{forwardedV4 + ", not-an-ip"},
-			want:         forwardedV4,
-		},
-		{
-			name:         "all-trusted chain falls back to peer",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   trustedPeer,
-			forwardedFor: []string{"10.0.0.9, 10.0.0.2"},
-			want:         "10.0.0.1",
-		},
-		{
-			name:         "trusted IPv6 peer honors forwarded client",
-			trusted:      []string{"2001:db8::/32"},
-			remoteAddr:   "[2001:db8::1]:9000",
-			forwardedFor: []string{forwardedV4},
-			want:         forwardedV4,
-		},
-		{
-			name:         "IPv4-mapped peer matches IPv4 trusted range",
-			trusted:      []string{trustedRangeV4},
-			remoteAddr:   "[::ffff:10.0.0.1]:5000",
-			forwardedFor: []string{forwardedV4},
-			want:         forwardedV4,
-		},
-	})
-}
-
-func TestContextRoundTrip(t *testing.T) {
-	t.Parallel()
-
-	ctx := clientip.WithClientIP(t.Context(), forwardedV4)
-	if got := clientip.FromContext(ctx); got != forwardedV4 {
-		t.Errorf("FromContext = %q, want %q", got, forwardedV4)
-	}
-}
-
-func TestFromContextAbsent(t *testing.T) {
-	t.Parallel()
-
-	if got := clientip.FromContext(t.Context()); got != "" {
-		t.Errorf("FromContext with no value = %q, want empty", got)
-	}
-}

internal/config/blocked_networks_internal_test.go

@@ -1,90 +0,0 @@
-package config
-
-import (
-	"testing"
-)
-
-// TestBlockedNetworksParsed loads a valid blocked_networks list and checks
-// each CIDR is parsed into the resolved prefixes in order.
-func TestBlockedNetworksParsed(t *testing.T) {
-	t.Parallel()
-
-	yamlContent := signingKeyLine + `blocked_networks:
-  - 203.0.113.0/24
-  - 2001:db8::/32
-`
-
-	c, err := configFromYAML(t, yamlContent)
-	if err != nil {
-		t.Fatalf("valid blocked_networks should load, got error: %v", err)
-	}
-
-	want := []string{"203.0.113.0/24", "2001:db8::/32"}
-	if len(c.BlockedNetworks) != len(want) {
-		t.Fatalf("BlockedNetworks = %v, want %d entries", c.BlockedNetworks, len(want))
-	}
-
-	for i, w := range want {
-		if got := c.BlockedNetworks[i].String(); got != w {
-			t.Errorf("BlockedNetworks[%d] = %q, want %q", i, got, w)
-		}
-	}
-}
-
-// TestBlockedNetworksOmittedIsEmpty confirms an omitted key leaves the
-// operator list empty; the built-in defaults still apply in the fetcher.
-func TestBlockedNetworksOmittedIsEmpty(t *testing.T) {
-	t.Parallel()
-
-	c, err := configFromYAML(t, signingKeyLine)
-	if err != nil {
-		t.Fatalf("minimal config should be valid, got error: %v", err)
-	}
-
-	if len(c.BlockedNetworks) != 0 {
-		t.Errorf("BlockedNetworks = %v, want empty", c.BlockedNetworks)
-	}
-}
-
-// TestBlockedNetworksInvalidAbortsStartup checks that malformed values abort
-// startup with an error naming the key and the offending value.
-func TestBlockedNetworksInvalidAbortsStartup(t *testing.T) {
-	t.Parallel()
-
-	runAbortCases(t, []abortCase{
-		{
-			name: "not-a-cidr",
-			yaml: signingKeyLine + `blocked_networks:
-  - not-a-cidr
-`,
-			wantErrSubstrings: []string{keyBlockedNetworks, "not-a-cidr"},
-		},
-		{
-			name: "bare-address-without-prefix",
-			yaml: signingKeyLine + `blocked_networks:
-  - 10.0.0.1
-`,
-			wantErrSubstrings: []string{keyBlockedNetworks, "10.0.0.1"},
-		},
-		{
-			name: "empty-entry",
-			yaml: signingKeyLine + `blocked_networks:
-  - ""
-`,
-			wantErrSubstrings: []string{keyBlockedNetworks},
-		},
-		{
-			name: "non-string-entry",
-			yaml: signingKeyLine + `blocked_networks:
-  - 42
-`,
-			wantErrSubstrings: []string{keyBlockedNetworks},
-		},
-		{
-			name: "null-value",
-			yaml: signingKeyLine + `blocked_networks:
-`,
-			wantErrSubstrings: []string{keyBlockedNetworks, nullValueText},
-		},
-	})
-}

internal/config/config.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"log/slog"
 	"math"
-	"net/netip"
 	"net/url"
 	"os"
 	"path/filepath"
@@ -43,8 +42,6 @@ const (
 	keyAllowHTTP                  = "allow_http"
 	keyUpstreamConnectionsPerHost = "upstream_connections_per_host"
 	keyCacheMaxBytes              = "cache_max_bytes"
-	keyBlockedNetworks            = "blocked_networks"
-	keyTrustedProxies             = "trusted_proxies"
 )
 
 // placeholderSigningKey is the dummy signing_key shipped in
@@ -63,7 +60,6 @@ var (
 	errNotAnInteger      = errors.New("not an integer")
 	errNotABoolean       = errors.New("not a boolean")
 	errNotAStringList    = errors.New("not a list of strings")
-	errNotAValidCIDR     = errors.New("not a valid CIDR network")
 	errNotAMetricsMap    = errors.New("not a map of metrics settings")
 	errEmptyListEntry    = errors.New("list contains an empty entry")
 	errEmptyEntry        = errors.New("contains an empty entry")
@@ -113,19 +109,6 @@ type Config struct {
 	AllowHTTP                  bool     // Allow non-TLS upstream (testing only)
 	UpstreamConnectionsPerHost int      // Max concurrent connections per upstream host
 
-	// BlockedNetworks are operator-supplied CIDR ranges to refuse in
-	// addition to the built-in SSRF blocklist. Enforced by the upstream
-	// fetcher's dialer; the built-in ranges always apply.
-	BlockedNetworks []netip.Prefix
-
-	// TrustedProxies are the CIDR ranges of reverse proxies whose
-	// forwarding headers may be believed. Forwarded headers are honored
-	// only when the immediate peer falls inside one of these ranges;
-	// otherwise the peer address is used and the headers are ignored, so
-	// an untrusted client cannot spoof its address. Empty means trust
-	// nothing and always use the peer address.
-	TrustedProxies []netip.Prefix
-
 	// CacheMaxBytes is the disk cache size limit in bytes. Zero
 	// disables the disk cache entirely. When cache_max_bytes is
 	// omitted from the configuration, this holds the computed default
@@ -194,16 +177,6 @@ func newFromSmartConfig(sc *smartconfig.Config) (*Config, error) {
 		}
 	}
 
-	blockedNetworks, err := parseCIDRList(sc, keyBlockedNetworks)
-	if err != nil {
-		return nil, err
-	}
-
-	trustedProxies, err := parseCIDRList(sc, keyTrustedProxies)
-	if err != nil {
-		return nil, err
-	}
-
 	loader := &strictLoader{sc: sc}
 
 	c := &Config{
@@ -219,9 +192,7 @@ func newFromSmartConfig(sc *smartconfig.Config) (*Config, error) {
 		AllowHTTP:       loader.boolVal(keyAllowHTTP, false),
 		UpstreamConnectionsPerHost: loader.intVal(
 			keyUpstreamConnectionsPerHost, DefaultUpstreamConnectionsPerHost),
-		CacheMaxBytes:   loader.int64Val(keyCacheMaxBytes, 0),
-		BlockedNetworks: blockedNetworks,
-		TrustedProxies:  trustedProxies,
+		CacheMaxBytes: loader.int64Val(keyCacheMaxBytes, 0),
 	}
 
 	// The computed default for cache_max_bytes needs a validated
@@ -253,7 +224,7 @@ func newFromSmartConfig(sc *smartconfig.Config) (*Config, error) {
 		return nil, loader.err
 	}
 
-	err = c.validate()
+	err := c.validate()
 	if err != nil {
 		return nil, err
 	}
@@ -337,8 +308,7 @@ func isKnownConfigKey(key string) bool {
 	switch key {
 	case keyDebug, keyMaintenanceMode, keyPort, keyStateDir, keySentryDSN,
 		keyDBURL, keyMetrics, keySigningKey, keyAllowlistHosts, keyAllowHTTP,
-		keyUpstreamConnectionsPerHost, keyCacheMaxBytes, keyBlockedNetworks,
-		keyTrustedProxies, "env":
+		keyUpstreamConnectionsPerHost, keyCacheMaxBytes, "env":
 		return true
 	}
 
@@ -832,87 +802,3 @@ func getStringSlice(sc *smartconfig.Config) []string {
 
 	return nil
 }
-
-// parseCIDRList parses the value of the named config key into CIDR
-// prefixes, or returns nil if the key is omitted. It accepts a YAML list
-// of strings or a comma-separated string. An explicitly null value, a
-// wrong type, an empty entry, a non-string entry, or an unparseable CIDR
-// aborts startup naming the key and the offending value; the default
-// (an empty list) applies only to an omitted key.
-func parseCIDRList(sc *smartconfig.Config, key string) ([]netip.Prefix, error) {
-	if sc == nil {
-		return nil, nil
-	}
-
-	raw, ok := sc.Get(key)
-	if !ok {
-		return nil, nil
-	}
-
-	if raw == nil {
-		return nil, errNullConfigValue(key)
-	}
-
-	entries, err := cidrListEntries(raw, key)
-	if err != nil {
-		return nil, err
-	}
-
-	prefixes := make([]netip.Prefix, 0, len(entries))
-
-	for _, entry := range entries {
-		prefix, err := netip.ParsePrefix(entry)
-		if err != nil {
-			return nil, fmt.Errorf("config key %q: value %q is %w",
-				key, entry, errNotAValidCIDR)
-		}
-
-		prefixes = append(prefixes, prefix)
-	}
-
-	return prefixes, nil
-}
-
-// cidrListEntries extracts the raw entries of the named CIDR-list key as
-// trimmed, non-empty strings, from either a YAML list of strings or a
-// comma-separated string. Any other shape is a configuration error.
-func cidrListEntries(raw any, key string) ([]string, error) {
-	switch val := raw.(type) {
-	case []any:
-		entries := make([]string, 0, len(val))
-
-		for _, item := range val {
-			str, ok := item.(string)
-			if !ok {
-				return nil, fmt.Errorf("config key %q: list entry %v (%T) is %w",
-					key, item, item, errNotAString)
-			}
-
-			if strings.TrimSpace(str) == "" {
-				return nil, fmt.Errorf("config key %q: %w",
-					key, errEmptyListEntry)
-			}
-
-			entries = append(entries, strings.TrimSpace(str))
-		}
-
-		return entries, nil
-	case string:
-		entries := make([]string, 0)
-
-		for part := range strings.SplitSeq(val, ",") {
-			trimmed := strings.TrimSpace(part)
-			if trimmed == "" {
-				return nil, fmt.Errorf("config key %q: value %q %w",
-					key, val, errEmptyEntry)
-			}
-
-			entries = append(entries, trimmed)
-		}
-
-		return entries, nil
-	default:
-		return nil, fmt.Errorf("config key %q: value %v (%T) is %w",
-			key, raw, raw, errNotAStringList)
-	}
-}

internal/config/trusted_proxies_internal_test.go

@@ -1,65 +0,0 @@
-package config
-
-import (
-	"strings"
-	"testing"
-)
-
-// TestTrustedProxiesConfig checks the trusted_proxies key wiring: a valid
-// CIDR list lands in TrustedProxies in order, and an omitted key trusts no
-// one. The list parser itself is shared with blocked_networks and is
-// exercised in depth by that key's tests.
-func TestTrustedProxiesConfig(t *testing.T) {
-	t.Parallel()
-
-	t.Run("valid list is parsed in order", func(t *testing.T) {
-		t.Parallel()
-
-		c, err := configFromYAML(t,
-			signingKeyLine+`trusted_proxies: ["10.0.0.0/8", "2001:db8::/32"]`+"\n")
-		if err != nil {
-			t.Fatalf("valid trusted_proxies should load: %v", err)
-		}
-
-		got := make([]string, len(c.TrustedProxies))
-		for i, p := range c.TrustedProxies {
-			got[i] = p.String()
-		}
-
-		if joined := strings.Join(got, ","); joined != "10.0.0.0/8,2001:db8::/32" {
-			t.Errorf("TrustedProxies = %v, want the two ranges in order", got)
-		}
-	})
-
-	t.Run("omitted key trusts no one", func(t *testing.T) {
-		t.Parallel()
-
-		c, err := configFromYAML(t, signingKeyLine)
-		if err != nil {
-			t.Fatalf("minimal config should load: %v", err)
-		}
-
-		if len(c.TrustedProxies) != 0 {
-			t.Errorf("TrustedProxies = %v, want empty", c.TrustedProxies)
-		}
-	})
-}
-
-// TestTrustedProxiesInvalidAbortsStartup checks that an invalid or null
-// value aborts startup with an error naming the key and the offending value.
-func TestTrustedProxiesInvalidAbortsStartup(t *testing.T) {
-	t.Parallel()
-
-	runAbortCases(t, []abortCase{
-		{
-			name:              "invalid cidr",
-			yaml:              signingKeyLine + `trusted_proxies: ["999.0.0.0/8"]` + "\n",
-			wantErrSubstrings: []string{keyTrustedProxies, "999.0.0.0/8"},
-		},
-		{
-			name:              "null value",
-			yaml:              signingKeyLine + "trusted_proxies:\n",
-			wantErrSubstrings: []string{keyTrustedProxies, nullValueText},
-		},
-	})
-}

internal/handlers/auth.go

@@ -2,18 +2,24 @@ package handlers
 
 import (
 	"crypto/subtle"
+	"errors"
+	"fmt"
 	"html/template"
 	"net/http"
 	"net/url"
 	"strconv"
 	"time"
 
-	"sneak.berlin/go/pixa/internal/clientip"
 	"sneak.berlin/go/pixa/internal/encurl"
 	"sneak.berlin/go/pixa/internal/imgcache"
 	"sneak.berlin/go/pixa/internal/templates"
 )
 
+// errInvalidFormField reports a generator form field whose value is
+// non-numeric or out of range. The offending field name is wrapped in so the
+// response can name it.
+var errInvalidFormField = errors.New("invalid")
+
 // HandleRoot serves the login page or generator page based on authentication state.
 func (s *Handlers) HandleRoot() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
@@ -48,8 +54,7 @@ func (s *Handlers) handleLoginPost(w http.ResponseWriter, r *http.Request) {
 
 	// Constant-time comparison to prevent timing attacks
 	if subtle.ConstantTimeCompare([]byte(submittedKey), []byte(s.config.SigningKey)) != 1 {
-		s.log.Warn("failed login attempt",
-			"remote_addr", clientip.FromContext(r.Context()))
+		s.log.Warn("failed login attempt", "remote_addr", r.RemoteAddr)
 		s.renderLogin(w, r, "Invalid signing key")
 
 		return
@@ -64,8 +69,7 @@ func (s *Handlers) handleLoginPost(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	s.log.Info("successful login",
-		"remote_addr", clientip.FromContext(r.Context()))
+	s.log.Info("successful login", "remote_addr", r.RemoteAddr)
 
 	// Redirect to generator page
 	http.Redirect(w, r, "/", http.StatusSeeOther)
@@ -101,18 +105,26 @@ func (s *Handlers) HandleGenerateURL() http.HandlerFunc {
 		// Validate source URL
 		parsed, err := url.Parse(sourceURL)
 		if err != nil || parsed.Host == "" {
-			s.renderGeneratorWithForm(w, r, "Invalid source URL", r.Form)
+			s.renderGeneratorWithForm(w, r, "Invalid source URL", r.Form,
+				http.StatusBadRequest)
 
 			return
 		}
 
-		payload, expiresAt, ttl := buildGeneratePayload(parsed, r.Form)
+		payload, expiresAt, ttl, err := buildGeneratePayload(parsed, r.Form)
+		if err != nil {
+			s.renderGeneratorWithForm(w, r, err.Error(), r.Form,
+				http.StatusBadRequest)
+
+			return
+		}
 
 		// Generate encrypted token
 		token, err := s.encGen.Generate(payload)
 		if err != nil {
 			s.log.Error("failed to generate encrypted URL", "error", err)
-			s.renderGeneratorWithForm(w, r, "Failed to generate URL", r.Form)
+			s.renderGeneratorWithForm(w, r, "Failed to generate URL", r.Form,
+				http.StatusInternalServerError)
 
 			return
 		}
@@ -140,17 +152,38 @@ func (s *Handlers) HandleGenerateURL() http.HandlerFunc {
 }
 
 // buildGeneratePayload parses the numeric form fields and assembles the
-// encrypted URL payload. ttl=0 means never expires (ExpiresAt stays 0).
+// encrypted URL payload. ttl=0 means never expires (ExpiresAt stays 0). A
+// non-numeric or out-of-range field, or an unrecognized fit mode, is a client
+// error naming the offending field, so an unusable token is never minted.
 func buildGeneratePayload(
 	parsed *url.URL, form url.Values,
-) (*encurl.Payload, time.Time, int) {
-	width, _ := strconv.Atoi(form.Get("width"))
-	height, _ := strconv.Atoi(form.Get("height"))
-	quality, _ := strconv.Atoi(form.Get("quality"))
-	ttl, _ := strconv.Atoi(form.Get("ttl"))
+) (*encurl.Payload, time.Time, int, error) {
+	width, err := parseFormDimension(form, "width")
+	if err != nil {
+		return nil, time.Time{}, 0, err
+	}
 
-	if quality <= 0 {
-		quality = 85
+	height, err := parseFormDimension(form, "height")
+	if err != nil {
+		return nil, time.Time{}, 0, err
+	}
+
+	quality, err := parseFormCount(form, "quality", encurl.DefaultQuality)
+	if err != nil {
+		return nil, time.Time{}, 0, err
+	}
+
+	ttl, err := parseFormCount(form, "ttl", 0)
+	if err != nil {
+		return nil, time.Time{}, 0, err
+	}
+
+	fitMode := imgcache.FitMode(form.Get("fit"))
+
+	err = imgcache.ValidateFitMode(fitMode)
+	if err != nil {
+		return nil, time.Time{}, 0,
+			fmt.Errorf("%w: %s", imgcache.ErrInvalidFitMode, form.Get("fit"))
 	}
 
 	var (
@@ -171,11 +204,45 @@ func buildGeneratePayload(
 		Height:      height,
 		Format:      imgcache.ImageFormat(form.Get("format")),
 		Quality:     quality,
-		FitMode:     imgcache.FitMode(form.Get("fit")),
+		FitMode:     fitMode,
 		ExpiresAt:   expiresAtUnix,
 	}
 
-	return payload, expiresAt, ttl
+	return payload, expiresAt, ttl, nil
+}
+
+// parseFormDimension reads an optional width or height form field. An empty
+// value means "original size" (0). A non-numeric, negative, or over-limit
+// value is rejected with an error naming the field.
+func parseFormDimension(form url.Values, field string) (int, error) {
+	raw := form.Get(field)
+	if raw == "" {
+		return 0, nil
+	}
+
+	value, err := strconv.Atoi(raw)
+	if err != nil || value < 0 || value > imgcache.MaxDimension {
+		return 0, fmt.Errorf("%w %s", errInvalidFormField, field)
+	}
+
+	return value, nil
+}
+
+// parseFormCount reads an optional non-negative integer form field, returning
+// def when the field is empty and an error naming the field when the value is
+// non-numeric or negative.
+func parseFormCount(form url.Values, field string, def int) (int, error) {
+	raw := form.Get(field)
+	if raw == "" {
+		return def, nil
+	}
+
+	value, err := strconv.Atoi(raw)
+	if err != nil || value < 0 {
+		return 0, fmt.Errorf("%w %s", errInvalidFormField, field)
+	}
+
+	return value, nil
 }
 
 // generatorData holds template data for the generator page.
@@ -215,6 +282,15 @@ func (s *Handlers) renderLogin(
 
 func (s *Handlers) renderGenerator(
 	w http.ResponseWriter, r *http.Request, data *generatorData,
+) {
+	s.renderGeneratorStatus(w, r, data, http.StatusOK)
+}
+
+// renderGeneratorStatus renders the generator page with an explicit HTTP
+// status. The status is written before the body so both it and the
+// Content-Type header take effect; a rejected form uses 400.
+func (s *Handlers) renderGeneratorStatus(
+	w http.ResponseWriter, r *http.Request, data *generatorData, status int,
 ) {
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
 
@@ -224,17 +300,19 @@ func (s *Handlers) renderGenerator(
 
 	data.CSRFField = csrfField(r)
 
+	w.WriteHeader(status)
+
 	err := templates.Render(w, "generator.html", data)
 	if err != nil {
 		s.log.Error("failed to render generator template", "error", err)
-		http.Error(w, "Internal server error", http.StatusInternalServerError)
 	}
 }
 
 func (s *Handlers) renderGeneratorWithForm(
-	w http.ResponseWriter, r *http.Request, errorMsg string, form url.Values,
+	w http.ResponseWriter, r *http.Request, errorMsg string,
+	form url.Values, status int,
 ) {
-	s.renderGenerator(w, r, &generatorData{
+	s.renderGeneratorStatus(w, r, &generatorData{
 		Error:       errorMsg,
 		FormURL:     form.Get("url"),
 		FormWidth:   form.Get("width"),
@@ -243,7 +321,7 @@ func (s *Handlers) renderGeneratorWithForm(
 		FormQuality: form.Get("quality"),
 		FormFit:     form.Get("fit"),
 		FormTTL:     form.Get("ttl"),
-	})
+	}, status)
 }
 
 func (s *Handlers) buildGeneratedURL(r *http.Request, token, format string) string {

internal/handlers/auth_clientip_internal_test.go

@@ -1,41 +0,0 @@
-package handlers
-
-import (
-	"bytes"
-	"log/slog"
-	"net/http"
-	"net/http/httptest"
-	"net/url"
-	"strings"
-	"testing"
-
-	"sneak.berlin/go/pixa/internal/clientip"
-	"sneak.berlin/go/pixa/internal/config"
-)
-
-// TestFailedLoginLogsResolvedClientIP verifies the failed-login record
-// carries the resolved client IP from the request context, not the raw
-// proxy peer address.
-func TestFailedLoginLogsResolvedClientIP(t *testing.T) {
-	t.Parallel()
-
-	var buf bytes.Buffer
-
-	h := &Handlers{
-		log:    slog.New(slog.NewJSONHandler(&buf, nil)),
-		config: &config.Config{SigningKey: testSigningKey},
-	}
-
-	form := url.Values{loginKeyField: {"wrong-key"}}
-	req := httptest.NewRequestWithContext(
-		t.Context(), http.MethodPost, "/",
-		strings.NewReader(form.Encode()))
-	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	req = req.WithContext(clientip.WithClientIP(req.Context(), "203.0.113.7"))
-
-	h.handleLoginPost(httptest.NewRecorder(), req)
-
-	if !strings.Contains(buf.String(), `"remote_addr":"203.0.113.7"`) {
-		t.Errorf("failed-login log missing resolved client IP; got %q", buf.String())
-	}
-}

internal/handlers/auth_generate_internal_test.go

@@ -0,0 +1,66 @@
+package handlers
+
+import (
+	"maps"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+)
+
+// generatePost submits the /generate form with a valid session and CSRF token
+// plus the caller's extra fields, returning the recorder.
+func generatePost(
+	t *testing.T, extra url.Values,
+) *httptest.ResponseRecorder {
+	t.Helper()
+
+	h, srv := newCSRFTestRouter(t)
+
+	sessionCookie := newSessionCookie(t, h)
+	cookies, token := csrfCredentials(t, srv, []*http.Cookie{sessionCookie})
+	cookies = append(cookies, sessionCookie)
+
+	form := url.Values{
+		sourceURLField: {testSourceURL},
+		csrfTokenField: {token},
+	}
+	maps.Copy(form, extra)
+
+	return postForm(srv, "/generate", cookies, form)
+}
+
+// TestGeneratePostRejectsNonNumericWidth verifies that a non-numeric width is
+// rejected with 400 naming the field rather than being coerced to 0 and
+// minting a 0-width token.
+func TestGeneratePostRejectsNonNumericWidth(t *testing.T) {
+	t.Parallel()
+
+	rec := generatePost(t, url.Values{"width": {"abc"}})
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusBadRequest)
+	}
+
+	if strings.Contains(rec.Body.String(), "/v1/e/") {
+		t.Error("a token was generated for non-numeric width")
+	}
+}
+
+// TestGeneratePostRejectsOverLimitWidth verifies that a width beyond
+// MaxDimension is rejected at generation time so an unusable token cannot be
+// minted.
+func TestGeneratePostRejectsOverLimitWidth(t *testing.T) {
+	t.Parallel()
+
+	rec := generatePost(t, url.Values{"width": {"100000"}})
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusBadRequest)
+	}
+
+	if strings.Contains(rec.Body.String(), "/v1/e/") {
+		t.Error("a token was generated for an over-limit width")
+	}
+}

internal/handlers/handlers.go

@@ -111,8 +111,6 @@ func (s *Handlers) initImageService() error {
 		fetcherCfg.MaxConnectionsPerHost = s.config.UpstreamConnectionsPerHost
 	}
 
-	fetcherCfg.BlockedNetworks = s.config.BlockedNetworks
-
 	// Create the service
 	svc, err := imgcache.NewService(&imgcache.ServiceConfig{
 		Cache:         cache,

internal/handlers/image.go

@@ -110,13 +110,6 @@ func (s *Handlers) parseImageRequest(
 
 	if fit := query.Get("fit"); fit != "" {
 		req.FitMode = imgcache.FitMode(fit)
-
-		fitErr := imgcache.ValidateFitMode(req.FitMode)
-		if fitErr != nil {
-			s.respondError(w, "invalid fit mode: "+fit, http.StatusBadRequest)
-
-			return nil, false
-		}
 	}
 
 	// Default quality if not set
@@ -129,6 +122,18 @@ func (s *Handlers) parseImageRequest(
 		req.FitMode = imgcache.FitCover
 	}
 
+	// Enforce dimension and fit-mode bounds, shared with the encrypted-URL
+	// route. Dimensions are already bounded by the path parser above; this
+	// also rejects an unrecognized fit mode with 400 instead of letting it
+	// reach the processor as a 500.
+	err = imgcache.ValidateImageRequest(req)
+	if err != nil {
+		s.respondError(w, "invalid image request: "+err.Error(),
+			http.StatusBadRequest)
+
+		return nil, false
+	}
+
 	return req, true
 }
 

internal/handlers/imageenc.go

@@ -50,6 +50,19 @@ func (s *Handlers) HandleImageEnc() http.HandlerFunc {
 		// Convert payload to ImageRequest
 		req := payload.ToImageRequest()
 
+		// Apply the same dimension and fit-mode bounds as the plain image
+		// route: a sealed payload is trusted for its origin, not for staying
+		// within limits, so an over-limit size or unknown fit mode is a 400
+		// here rather than an out-of-memory or a 500 from the processor.
+		err = imgcache.ValidateImageRequest(req)
+		if err != nil {
+			s.log.Debug("encrypted URL failed validation", "error", err)
+			s.respondError(w, "invalid encrypted URL: "+err.Error(),
+				http.StatusBadRequest)
+
+			return
+		}
+
 		// Log the request
 		s.log.Debug("encrypted image request",
 			"host", req.SourceHost,

internal/handlers/imageenc_internal_test.go

@@ -0,0 +1,98 @@
+package handlers
+
+import (
+	"context"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/go-chi/chi/v5"
+
+	"sneak.berlin/go/pixa/internal/encurl"
+	"sneak.berlin/go/pixa/internal/imgcache"
+)
+
+// newEncTestServer builds a router serving the encrypted-URL route with a
+// generator seeded by the shared test signing key. The image service is left
+// nil: these tests exercise validation that rejects a token before any image
+// is fetched, so the handler must never reach the service.
+func newEncTestServer(t *testing.T) (*encurl.Generator, http.Handler) {
+	t.Helper()
+
+	encGen, err := encurl.NewGenerator(testSigningKey)
+	if err != nil {
+		t.Fatalf("encurl.NewGenerator() error = %v", err)
+	}
+
+	h := &Handlers{
+		log:    slog.New(slog.DiscardHandler),
+		encGen: encGen,
+	}
+
+	r := chi.NewRouter()
+	r.Get("/v1/e/{token}/*", h.HandleImageEnc())
+
+	return encGen, r
+}
+
+// getEncToken issues a GET for the given token and returns the recorder.
+func getEncToken(srv http.Handler, token string) *httptest.ResponseRecorder {
+	req := httptest.NewRequestWithContext(
+		context.Background(), http.MethodGet, "/v1/e/"+token+"/img.jpg", nil)
+	rec := httptest.NewRecorder()
+	srv.ServeHTTP(rec, req)
+
+	return rec
+}
+
+// TestHandleImageEnc_OverLimitDimension_Returns400 verifies that a decrypted
+// token requesting a dimension beyond MaxDimension is rejected with 400
+// instead of reaching the image processor and libvips.
+func TestHandleImageEnc_OverLimitDimension_Returns400(t *testing.T) {
+	t.Parallel()
+
+	encGen, srv := newEncTestServer(t)
+
+	token, err := encGen.Generate(&encurl.Payload{
+		SourceHost: "cdn.example.com",
+		SourcePath: "/photo.jpg",
+		Width:      100000,
+		Height:     100000,
+	})
+	if err != nil {
+		t.Fatalf("Generate() error = %v", err)
+	}
+
+	rec := getEncToken(srv, token)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusBadRequest)
+	}
+}
+
+// TestHandleImageEnc_InvalidFitMode_Returns400 verifies that a decrypted token
+// carrying an unrecognized fit mode is rejected with 400 rather than surfacing
+// as a 500 from the image processor's default branch.
+func TestHandleImageEnc_InvalidFitMode_Returns400(t *testing.T) {
+	t.Parallel()
+
+	encGen, srv := newEncTestServer(t)
+
+	token, err := encGen.Generate(&encurl.Payload{
+		SourceHost: "cdn.example.com",
+		SourcePath: "/photo.jpg",
+		Width:      800,
+		Height:     600,
+		FitMode:    imgcache.FitMode("bogus"),
+	})
+	if err != nil {
+		t.Fatalf("Generate() error = %v", err)
+	}
+
+	rec := getEncToken(srv, token)
+
+	if rec.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want %d", rec.Code, http.StatusBadRequest)
+	}
+}

internal/httpfetcher/blocked_networks_internal_test.go

@@ -1,111 +0,0 @@
-package httpfetcher
-
-import (
-	"context"
-	"errors"
-	"net"
-	"net/http"
-	"net/netip"
-	"testing"
-)
-
-// TestIsPrivateIPBlocksSpecialRanges covers the internal and special-use
-// ranges added to the built-in blocklist, in IPv4, IPv6, and IPv4-mapped
-// forms, alongside public controls that must stay reachable.
-func TestIsPrivateIPBlocksSpecialRanges(t *testing.T) {
-	t.Parallel()
-
-	tests := []struct {
-		name string
-		ip   string
-		want bool
-	}{
-		{"cgnat-low", "100.64.0.1", true},
-		{"cgnat-high", "100.127.255.254", true},
-		{"ietf-protocol", "192.0.0.1", true},
-		{"benchmark-low", "198.18.0.1", true},
-		{"benchmark-high", "198.19.255.254", true},
-		{"nat64", "64:ff9b::1", true},
-		{"nat64-embeds-private", "64:ff9b::a00:1", true}, // maps 10.0.0.1
-		{"ipv4-mapped-private", "::ffff:10.0.0.1", true},
-		{"cloud-metadata", "169.254.169.254", true},
-		{"public-v4", "8.8.8.8", false},
-		{"test-net-1-public", testPublicHost, false}, // TEST-NET-1, stays public
-		{"public-v6", "2001:4860:4860::8888", false},
-	}
-
-	for _, tc := range tests {
-		t.Run(tc.name, func(t *testing.T) {
-			t.Parallel()
-
-			ip := net.ParseIP(tc.ip)
-			if ip == nil {
-				t.Fatalf("failed to parse IP %q", tc.ip)
-			}
-
-			got := isPrivateIP(ip)
-			if got != tc.want {
-				t.Errorf("isPrivateIP(%q) = %v, want %v", tc.ip, got, tc.want)
-			}
-		})
-	}
-}
-
-// transportOf returns the *http.Transport backing a fetcher, so a test can
-// exercise the SSRF-safe dialer New installed with the operator blocklist.
-func transportOf(t *testing.T, f *HTTPFetcher) *http.Transport {
-	t.Helper()
-
-	transport, ok := f.client.Transport.(*http.Transport)
-	if !ok {
-		t.Fatalf("transport is %T, want *http.Transport", f.client.Transport)
-	}
-
-	return transport
-}
-
-// TestDialerEnforcesBlockedNetworks proves an operator-supplied
-// blocked_networks entry is enforced by the dialer, in addition to the
-// built-in ranges, while an address outside both stays dialable.
-func TestDialerEnforcesBlockedNetworks(t *testing.T) {
-	t.Parallel()
-
-	cfg := DefaultConfig()
-	// TEST-NET-2 (198.51.100.0/24) is public to the built-in check, so
-	// blocking it can only come from the operator-supplied list.
-	cfg.BlockedNetworks = []netip.Prefix{netip.MustParsePrefix("198.51.100.0/24")}
-
-	transport := transportOf(t, New(cfg))
-
-	blocked := []string{
-		"198.51.100.5:80", // operator-supplied range
-		"10.0.0.5:80",     // built-in RFC 1918, still enforced
-		"100.64.0.1:80",   // built-in CGNAT range
-	}
-
-	for _, addr := range blocked {
-		t.Run("blocked/"+addr, func(t *testing.T) {
-			t.Parallel()
-
-			_, err := transport.DialContext(context.Background(), "tcp", addr)
-			if !errors.Is(err, ErrSSRFBlocked) {
-				t.Errorf("DialContext(%q) = %v, want ErrSSRFBlocked", addr, err)
-			}
-		})
-	}
-
-	t.Run("public-not-blocked", func(t *testing.T) {
-		t.Parallel()
-
-		// A cancelled context makes the dial fail without touching the
-		// network; the point is only that a public literal outside every
-		// blocked range is not SSRF-blocked.
-		ctx, cancel := context.WithCancel(context.Background())
-		cancel()
-
-		_, err := transport.DialContext(ctx, "tcp", testPublicHost+":80")
-		if errors.Is(err, ErrSSRFBlocked) {
-			t.Errorf("public target SSRF-blocked with operator list set: %v", err)
-		}
-	})
-}

internal/httpfetcher/httpfetcher.go

@@ -11,7 +11,6 @@ import (
 	"net"
 	"net/http"
 	"net/http/httptrace"
-	"net/netip"
 	neturl "net/url"
 	"slices"
 	"strings"
@@ -47,20 +46,6 @@ const (
 	localhostIPv6 = "::1"
 )
 
-// builtinBlockedPrefixes are internal or special-use ranges that Go's
-// net.IP predicates (IsPrivate, IsLinkLocalUnicast, and the like) do not
-// already cover. They are always blocked, in addition to any
-// operator-supplied networks. IPv4-mapped IPv6 addresses are unmapped
-// before matching, so these IPv4 ranges are caught in both forms.
-//
-//nolint:gochecknoglobals // immutable built-in blocklist
-var builtinBlockedPrefixes = []netip.Prefix{
-	netip.MustParsePrefix("100.64.0.0/10"), // RFC 6598 CGNAT / carrier-grade NAT
-	netip.MustParsePrefix("192.0.0.0/24"),  // RFC 6890 IETF protocol assignments
-	netip.MustParsePrefix("198.18.0.0/15"), // RFC 2544 benchmarking range
-	netip.MustParsePrefix("64:ff9b::/96"),  // RFC 6052 NAT64 (maps onto IPv4)
-}
-
 // Fetcher errors.
 var (
 	ErrSSRFBlocked        = errors.New("request blocked: private or internal IP")
@@ -122,9 +107,6 @@ type Config struct {
 	AllowHTTP bool
 	// MaxConnectionsPerHost limits concurrent connections to each upstream host.
 	MaxConnectionsPerHost int
-	// BlockedNetworks are operator-supplied CIDR ranges refused by the
-	// dialer, in addition to the always-enforced built-in ranges.
-	BlockedNetworks []netip.Prefix
 }
 
 // DefaultConfig returns a Config with sensible defaults.
@@ -160,13 +142,9 @@ func New(config *Config) *HTTPFetcher {
 		config = DefaultConfig()
 	}
 
-	// Create transport with SSRF-safe dialer. The dialer re-resolves and
-	// re-checks at connect time (closing the DNS-rebinding window) against
-	// both the built-in ranges and the operator-supplied blocklist.
+	// Create transport with SSRF-safe dialer
 	transport := &http.Transport{
-		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
-			return dialSSRFSafe(ctx, network, addr, config.BlockedNetworks)
-		},
+		DialContext:         ssrfSafeDialer,
 		TLSHandshakeTimeout: DefaultTLSTimeout,
 		MaxIdleConns:        DefaultMaxIdleConns,
 		IdleConnTimeout:     DefaultIdleConnTimeout,
@@ -473,53 +451,11 @@ func isPrivateIP(ip net.IP) bool {
 		}
 	}
 
-	// Special-use ranges the net.IP predicates above do not cover.
-	addr, ok := netip.AddrFromSlice(ip)
-	if !ok {
-		return true
-	}
-
-	addr = addr.Unmap()
-
-	return slices.ContainsFunc(builtinBlockedPrefixes, func(prefix netip.Prefix) bool {
-		return prefix.Contains(addr)
-	})
+	return false
 }
 
-// isBlockedIP reports whether ip is refused, either by the built-in
-// internal-range check or by one of the operator-supplied prefixes.
-func isBlockedIP(ip net.IP, blocked []netip.Prefix) bool {
-	if isPrivateIP(ip) {
-		return true
-	}
-
-	addr, ok := netip.AddrFromSlice(ip)
-	if !ok {
-		return true
-	}
-
-	addr = addr.Unmap()
-
-	return slices.ContainsFunc(blocked, func(prefix netip.Prefix) bool {
-		return prefix.Contains(addr)
-	})
-}
-
-// ssrfSafeDialer validates IP addresses against the built-in blocked ranges
-// before connecting. New wraps dialSSRFSafe with the operator-supplied
-// blocklist; this entry point enforces the built-in ranges alone.
+// ssrfSafeDialer is a custom dialer that validates IP addresses before connecting.
 func ssrfSafeDialer(ctx context.Context, network, addr string) (net.Conn, error) {
-	return dialSSRFSafe(ctx, network, addr, nil)
-}
-
-// dialSSRFSafe re-resolves addr and refuses to connect to any built-in
-// internal range or operator-supplied blocked prefix, closing the
-// DNS-rebinding window at connect time.
-func dialSSRFSafe(
-	ctx context.Context,
-	network, addr string,
-	blocked []netip.Prefix,
-) (net.Conn, error) {
 	host, port, err := net.SplitHostPort(addr)
 	if err != nil {
 		return nil, err
@@ -532,10 +468,8 @@ func dialSSRFSafe(
 	}
 
 	// Check all resolved IPs
-	for _, ip := range ips {
-		if isBlockedIP(ip, blocked) {
-			return nil, ErrSSRFBlocked
-		}
+	if slices.ContainsFunc(ips, isPrivateIP) {
+		return nil, ErrSSRFBlocked
 	}
 
 	// Connect using the first valid IP

internal/imgcache/imgcache.go

@@ -59,6 +59,23 @@ func ValidateFitMode(fit FitMode) error {
 	}
 }
 
+// ValidateImageRequest checks that a request's dimensions are within
+// MaxDimension and its fit mode is recognized. Both the plain /v1/image/
+// route and the encrypted /v1/e/ route validate through this function so a
+// request from either source enforces identical bounds, regardless of how it
+// was constructed. A width or height of 0 means "original size" and is valid.
+func ValidateImageRequest(req *ImageRequest) error {
+	if req.Size.Width < 0 || req.Size.Height < 0 {
+		return ErrInvalidSize
+	}
+
+	if req.Size.Width > MaxDimension || req.Size.Height > MaxDimension {
+		return ErrDimensionTooLarge
+	}
+
+	return ValidateFitMode(req.FitMode)
+}
+
 // ImageRequest represents a request for a processed image
 type ImageRequest struct {
 	// SourceHost is the origin host (e.g., "cdn.example.com")

internal/imgcache/validate_internal_test.go

@@ -0,0 +1,64 @@
+package imgcache
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestValidateImageRequest(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		req     ImageRequest
+		wantErr error
+	}{
+		{
+			name: "within bounds",
+			req:  ImageRequest{Size: Size{Width: 800, Height: 600}, FitMode: FitCover},
+		},
+		{
+			name: "original size and empty fit",
+			req:  ImageRequest{Size: Size{Width: 0, Height: 0}},
+		},
+		{
+			name:    "width over limit",
+			req:     ImageRequest{Size: Size{Width: MaxDimension + 1, Height: 600}},
+			wantErr: ErrDimensionTooLarge,
+		},
+		{
+			name:    "height over limit",
+			req:     ImageRequest{Size: Size{Width: 800, Height: MaxDimension + 1}},
+			wantErr: ErrDimensionTooLarge,
+		},
+		{
+			name:    "negative width",
+			req:     ImageRequest{Size: Size{Width: -1, Height: 600}},
+			wantErr: ErrInvalidSize,
+		},
+		{
+			name:    "invalid fit mode",
+			req:     ImageRequest{Size: Size{Width: 800, Height: 600}, FitMode: "bogus"},
+			wantErr: ErrInvalidFitMode,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			err := ValidateImageRequest(&tt.req)
+			if tt.wantErr == nil {
+				if err != nil {
+					t.Fatalf("ValidateImageRequest() error = %v, want nil", err)
+				}
+
+				return
+			}
+
+			if !errors.Is(err, tt.wantErr) {
+				t.Fatalf("ValidateImageRequest() error = %v, want %v", err, tt.wantErr)
+			}
+		})
+	}
+}

internal/middleware/client_ip_internal_test.go

@@ -1,118 +0,0 @@
-package middleware
-
-import (
-	"bytes"
-	"log/slog"
-	"net/http"
-	"net/http/httptest"
-	"net/netip"
-	"strings"
-	"testing"
-
-	"sneak.berlin/go/pixa/internal/clientip"
-	"sneak.berlin/go/pixa/internal/config"
-)
-
-// testForwardedClient is the client address the proxy forwards.
-const testForwardedClient = "203.0.113.7"
-
-// newTestMiddleware builds a Middleware whose resolver trusts the given
-// CIDRs and whose logger writes JSON to buf.
-func newTestMiddleware(t *testing.T, buf *bytes.Buffer, trusted ...string) *Middleware {
-	t.Helper()
-
-	prefixes := make([]netip.Prefix, 0, len(trusted))
-
-	for _, c := range trusted {
-		p, err := netip.ParsePrefix(c)
-		if err != nil {
-			t.Fatalf("netip.ParsePrefix(%q) error = %v", c, err)
-		}
-
-		prefixes = append(prefixes, p)
-	}
-
-	return &Middleware{
-		log:      slog.New(slog.NewJSONHandler(buf, nil)),
-		config:   &config.Config{TrustedProxies: prefixes},
-		clientIP: clientip.NewResolver(prefixes),
-	}
-}
-
-// TestClientIPMiddlewareStoresResolvedIP verifies the ClientIP middleware
-// puts the resolved address into the request context for a trusted and an
-// untrusted peer.
-func TestClientIPMiddlewareStoresResolvedIP(t *testing.T) {
-	t.Parallel()
-
-	tests := []struct {
-		name       string
-		remoteAddr string
-		forwarded  string
-		want       string
-	}{
-		{
-			name:       "trusted peer honors forwarded client",
-			remoteAddr: "10.0.0.1:5000",
-			forwarded:  testForwardedClient,
-			want:       testForwardedClient,
-		},
-		{
-			name:       "untrusted peer ignores forwarded header",
-			remoteAddr: "198.51.100.9:5000",
-			forwarded:  testForwardedClient,
-			want:       "198.51.100.9",
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			t.Parallel()
-
-			mw := newTestMiddleware(t, &bytes.Buffer{}, "10.0.0.0/8")
-
-			var got string
-
-			handler := mw.ClientIP()(http.HandlerFunc(
-				func(_ http.ResponseWriter, r *http.Request) {
-					got = clientip.FromContext(r.Context())
-				}))
-
-			req := httptest.NewRequestWithContext(
-				t.Context(), http.MethodGet, "/", nil)
-			req.RemoteAddr = tt.remoteAddr
-			req.Header.Set("X-Forwarded-For", tt.forwarded)
-
-			handler.ServeHTTP(httptest.NewRecorder(), req)
-
-			if got != tt.want {
-				t.Errorf("client IP in context = %q, want %q", got, tt.want)
-			}
-		})
-	}
-}
-
-// TestLoggingUsesResolvedClientIP verifies the logging middleware records
-// the resolved forwarded client IP rather than the proxy peer address.
-func TestLoggingUsesResolvedClientIP(t *testing.T) {
-	t.Parallel()
-
-	var buf bytes.Buffer
-
-	mw := newTestMiddleware(t, &buf, "10.0.0.0/8")
-
-	handler := mw.ClientIP()(mw.Logging()(http.HandlerFunc(
-		func(w http.ResponseWriter, _ *http.Request) {
-			w.WriteHeader(http.StatusOK)
-		})))
-
-	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
-	req.RemoteAddr = "10.0.0.1:5000"
-	req.Header.Set("X-Forwarded-For", testForwardedClient)
-
-	handler.ServeHTTP(httptest.NewRecorder(), req)
-
-	if !strings.Contains(buf.String(), `"remoteIP":"`+testForwardedClient+`"`) {
-		t.Errorf("log output missing resolved client IP; got %q", buf.String())
-	}
-}

internal/middleware/middleware.go

@@ -3,6 +3,7 @@ package middleware
 
 import (
 	"log/slog"
+	"net"
 	"net/http"
 	"time"
 
@@ -13,7 +14,6 @@ import (
 	ghmm "github.com/slok/go-http-metrics/middleware"
 	"github.com/slok/go-http-metrics/middleware/std"
 	"go.uber.org/fx"
-	"sneak.berlin/go/pixa/internal/clientip"
 	"sneak.berlin/go/pixa/internal/config"
 	"sneak.berlin/go/pixa/internal/logger"
 )
@@ -58,34 +58,31 @@ type Params struct {
 
 // Middleware provides HTTP middleware functions.
 type Middleware struct {
-	log      *slog.Logger
-	config   *config.Config
-	clientIP *clientip.Resolver
+	log    *slog.Logger
+	config *config.Config
 }
 
 // New creates a new Middleware instance.
 func New(_ fx.Lifecycle, params Params) (*Middleware, error) {
 	s := &Middleware{
-		log:      params.Logger.Get(),
-		config:   params.Config,
-		clientIP: clientip.NewResolver(params.Config.TrustedProxies),
+		log:    params.Logger.Get(),
+		config: params.Config,
 	}
 
 	return s, nil
 }
 
-// ClientIP returns a middleware that resolves the real client IP,
-// honoring X-Forwarded-For only from trusted proxies, and stores it in
-// the request context for the logging middleware and handlers to read.
-func (s *Middleware) ClientIP() func(http.Handler) http.Handler {
-	return func(next http.Handler) http.Handler {
-		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			ip := s.clientIP.Resolve(
-				r.RemoteAddr, r.Header.Values(clientip.ForwardedForHeader))
-			ctx := clientip.WithClientIP(r.Context(), ip)
-			next.ServeHTTP(w, r.WithContext(ctx))
-		})
+func ipFromHostPort(hp string) string {
+	h, _, err := net.SplitHostPort(hp)
+	if err != nil {
+		return ""
 	}
+
+	if len(h) > 0 && h[0] == '[' {
+		return h[1 : len(h)-1]
+	}
+
+	return h
 }
 
 type loggingResponseWriter struct {
@@ -130,7 +127,7 @@ func (s *Middleware) Logging() func(http.Handler) http.Handler {
 					"request_id", reqID,
 					"referer", r.Referer(),
 					"proto", r.Proto,
-					"remoteIP", clientip.FromContext(ctx),
+					"remoteIP", ipFromHostPort(r.RemoteAddr),
 					"status", lrw.statusCode,
 					"response_bytes", lrw.bytesWritten,
 					"latency_ms", latency.Milliseconds(),

internal/server/routes.go

@@ -18,7 +18,6 @@ func (s *Server) SetupRoutes() {
 
 	s.router.Use(middleware.Recoverer)
 	s.router.Use(middleware.RequestID)
-	s.router.Use(s.mw.ClientIP())
 	s.router.Use(s.mw.SecurityHeaders())
 	s.router.Use(s.mw.Logging())