fix: patch GHSA-6wcg-mqvh-fcvg (#1616 )

* fix: patch GHSA-6wcg-mqvh-fcvg PR https://github.com/TecharoHQ/anubis/pull/1015 added the ability for reverse proxies using Anubis in subrequest auth mode to look at the path of a request as there are many rules in the wild that rely on checking the path. This is how access to things like robots.txt or anything in the .well-known directory is unaffected by Anubis. However this logic was also enabled for non-subrequest deployments of Anubis, meaning that a specially crafted request could include a /.well-known/ path in it and then get around Anubis with little effort. This fix gates the logic behind a new plumbed variable named subrequestMode that only fires when Anubis is running in subrequest auth mode. This properly contains that workaround so that the logic does not fire in most deployments. Signed-off-by: Xe Iaso <me@xeiaso.net> * chore: spelling Signed-off-by: Xe Iaso <me@xeiaso.net> --------- Signed-off-by: Xe Iaso <me@xeiaso.net>
2026-05-09 08:32:51 +00:00 · 2026-05-08 19:17:25 -04:00
11 changed files with 138 additions and 26 deletions
@@ -120,6 +120,7 @@ fahedouch
 fastcgi
 FCr
 fcrdns
+fcvg
 fediverse
 ffprobe
 fhdr
@@ -238,6 +239,7 @@ mnt
 Mojeek
 mojeekbot
 mozilla
+mqvh
 myclient
 mymaster
 mypass
@@ -387,6 +389,7 @@ vnd
 VPS
 Vultr
 WAIFU
+wcg
 weblate
 webmaster
 webpage
@@ -259,7 +259,7 @@ func main() {
 	}

 	lg.Info("loading policy file", "fname", *policyFname)
-	policy, err := libanubis.LoadPoliciesOrDefault(ctx, *policyFname, *challengeDifficulty, *slogLevel)
+	policy, err := libanubis.LoadPoliciesOrDefault(ctx, *policyFname, *challengeDifficulty, *slogLevel, strings.TrimSpace(*target) == "")
 	if err != nil {
 		log.Fatalf("can't parse policy file: %v", err)
 	}
@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

 <!-- This changes the project to: -->

+- Patch [GHSA-6wcg-mqvh-fcvg](https://github.com/TecharoHQ/anubis/security/advisories/GHSA-6wcg-mqvh-fcvg) by containing subrequest logic to Anubis instances in subrequest mode.
 - Move metrics server configuration to [the policy file](./admin/policies.mdx#metrics-server).
 - Expose [pprof endpoints](https://pkg.go.dev/net/http/pprof) on the metrics listener to enable profiling Anubis in production.
 - fix: prevent nil pointer panic in challenge validation when threshold rules match during PassChallenge (#1463)
@@ -595,7 +595,7 @@ func spawnAnubisWithOptions(t *testing.T, basePrefix string) string {
 		fmt.Fprintf(w, "<html><body><span id=anubis-test>%d</span></body></html>", time.Now().Unix())
 	})

-	policy, err := libanubis.LoadPoliciesOrDefault(t.Context(), "", anubis.DefaultDifficulty, "info")
+	policy, err := libanubis.LoadPoliciesOrDefault(t.Context(), "", anubis.DefaultDifficulty, "info", false)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -58,7 +58,7 @@ func loadPolicies(t *testing.T, fname string, difficulty int) *policy.ParsedConf

 	t.Logf("loading policy file: %s", fname)

-	anubisPolicy, err := LoadPoliciesOrDefault(ctx, fname, difficulty, "info")
+	anubisPolicy, err := LoadPoliciesOrDefault(ctx, fname, difficulty, "info", false)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -250,7 +250,7 @@ func TestLoadPolicies(t *testing.T) {
 			}
 			defer fin.Close()

-			if _, err := policy.ParseConfig(t.Context(), fin, fname, 4, "info"); err != nil {
+			if _, err := policy.ParseConfig(t.Context(), fin, fname, 4, "info", false); err != nil {
 				t.Fatal(err)
 			}
 		})
@@ -55,7 +55,7 @@ type Options struct {
 	DifficultyInJWT          bool
 }

-func LoadPoliciesOrDefault(ctx context.Context, fname string, defaultDifficulty int, logLevel string) (*policy.ParsedConfig, error) {
+func LoadPoliciesOrDefault(ctx context.Context, fname string, defaultDifficulty int, logLevel string, subrequestMode bool) (*policy.ParsedConfig, error) {
 	var fin io.ReadCloser
 	var err error

@@ -79,7 +79,7 @@ func LoadPoliciesOrDefault(ctx context.Context, fname string, defaultDifficulty
 		}
 	}(fin)

-	anubisPolicy, err := policy.ParseConfig(ctx, fin, fname, defaultDifficulty, logLevel)
+	anubisPolicy, err := policy.ParseConfig(ctx, fin, fname, defaultDifficulty, logLevel, subrequestMode)
 	if err != nil {
 		return nil, fmt.Errorf("can't parse policy file %s: %w", fname, err)
 	}
@@ -12,7 +12,7 @@ import (
 )

 func TestInvalidChallengeMethod(t *testing.T) {
-	if _, err := LoadPoliciesOrDefault(t.Context(), "testdata/invalid-challenge-method.yaml", 4, "info"); !errors.Is(err, policy.ErrChallengeRuleHasWrongAlgorithm) {
+	if _, err := LoadPoliciesOrDefault(t.Context(), "testdata/invalid-challenge-method.yaml", 4, "info", false); !errors.Is(err, policy.ErrChallengeRuleHasWrongAlgorithm) {
 		t.Fatalf("wanted error %v but got %v", policy.ErrChallengeRuleHasWrongAlgorithm, err)
 	}
 }
@@ -25,7 +25,7 @@ func TestBadConfigs(t *testing.T) {

 	for _, st := range finfos {
 		t.Run(st.Name(), func(t *testing.T) {
-			if _, err := LoadPoliciesOrDefault(t.Context(), filepath.Join("config", "testdata", "bad", st.Name()), anubis.DefaultDifficulty, "info"); err == nil {
+			if _, err := LoadPoliciesOrDefault(t.Context(), filepath.Join("config", "testdata", "bad", st.Name()), anubis.DefaultDifficulty, "info", false); err == nil {
 				t.Fatal(err)
 			} else {
 				t.Log(err)
@@ -44,13 +44,13 @@ func TestGoodConfigs(t *testing.T) {
 		t.Run(st.Name(), func(t *testing.T) {
 			t.Run("with-thoth", func(t *testing.T) {
 				ctx := thothmock.WithMockThoth(t)
-				if _, err := LoadPoliciesOrDefault(ctx, filepath.Join("config", "testdata", "good", st.Name()), anubis.DefaultDifficulty, "info"); err != nil {
+				if _, err := LoadPoliciesOrDefault(ctx, filepath.Join("config", "testdata", "good", st.Name()), anubis.DefaultDifficulty, "info", false); err != nil {
 					t.Fatal(err)
 				}
 			})

 			t.Run("without-thoth", func(t *testing.T) {
-				if _, err := LoadPoliciesOrDefault(t.Context(), filepath.Join("config", "testdata", "good", st.Name()), anubis.DefaultDifficulty, "info"); err != nil {
+				if _, err := LoadPoliciesOrDefault(t.Context(), filepath.Join("config", "testdata", "good", st.Name()), anubis.DefaultDifficulty, "info", false); err != nil {
 					t.Fatal(err)
 				}
 			})
@@ -94,23 +94,26 @@ func (hmc *HeaderMatchesChecker) Hash() string {
 }

 type PathChecker struct {
-	regexp *regexp.Regexp
-	hash   string
+	regexp         *regexp.Regexp
+	hash           string
+	subRequestMode bool
 }

-func NewPathChecker(rexStr string) (checker.Impl, error) {
+func NewPathChecker(rexStr string, subrequestMode bool) (checker.Impl, error) {
 	rex, err := regexp.Compile(strings.TrimSpace(rexStr))
 	if err != nil {
 		return nil, fmt.Errorf("%w: regex %s failed parse: %w", ErrMisconfiguration, rexStr, err)
 	}
-	return &PathChecker{rex, internal.FastHash(rexStr)}, nil
+	return &PathChecker{rex, internal.FastHash(rexStr), subrequestMode}, nil
 }

 func (pc *PathChecker) Check(r *http.Request) (bool, error) {
-	originalUrl := r.Header.Get("X-Original-URI")
-	if originalUrl != "" {
-		if pc.regexp.MatchString(originalUrl) {
-			return true, nil
+	if pc.subRequestMode {
+		originalUrl := r.Header.Get("X-Original-URI")
+		if originalUrl != "" {
+			if pc.regexp.MatchString(originalUrl) {
+				return true, nil
+			}
 		}
 	}

@@ -272,8 +272,8 @@ func TestPathChecker_XOriginalURI(t *testing.T) {

 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			// Create the PathChecker
-			pc, err := NewPathChecker(tt.regex)
+			// Create the PathChecker in subrequest mode so X-Original-URI is honored.
+			pc, err := NewPathChecker(tt.regex, true)
 			if err != nil {
 				if !tt.expectError {
 					t.Fatalf("NewPathChecker() unexpected error: %v", err)
@@ -305,3 +305,108 @@ func TestPathChecker_XOriginalURI(t *testing.T) {
 		})
 	}
 }
+
+// TestPathChecker_GHSA_6wcg_mqvh_fcvg is a regression test for
+// https://github.com/TecharoHQ/anubis/security/advisories/GHSA-6wcg-mqvh-fcvg.
+//
+// PR https://github.com/TecharoHQ/anubis/pull/1015 added the ability for
+// reverse proxies using Anubis in subrequest auth mode to look at the path
+// of a request as there are many rules in the wild that rely on checking
+// the path. This is how access to things like robots.txt or anything in the
+// .well-known directory is unaffected by Anubis.
+//
+// However this logic was also enabled for non-subrequest deployments of Anubis,
+// meaning that a specially crafted request could include a /.well-known/
+// path in it and then get around Anubis with little effort.
+//
+// This fix gates the logic behind a new plumbed variable named subrequestMode
+// that only fires when Anubis is running in subrequest auth mode. This
+// properly contains that workaround so that the logic does not fire in
+// most deployments.
+func TestPathChecker_GHSA_6wcg_mqvh_fcvg(t *testing.T) {
+	tests := []struct {
+		name           string
+		regex          string
+		urlPath        string
+		xOriginalURI   string
+		subRequestMode bool
+		want           bool
+	}{
+		{
+			name:           "default mode ignores spoofed X-Original-URI when real path matches",
+			regex:          "^/admin/.*",
+			urlPath:        "/admin/secret",
+			xOriginalURI:   "/public/index",
+			subRequestMode: false,
+			want:           true,
+		},
+		{
+			name:           "default mode ignores spoofed X-Original-URI when real path does not match",
+			regex:          "^/admin/.*",
+			urlPath:        "/public/index",
+			xOriginalURI:   "/admin/secret",
+			subRequestMode: false,
+			want:           false,
+		},
+		{
+			name:           "default mode without X-Original-URI matches real path",
+			regex:          "^/admin/.*",
+			urlPath:        "/admin/dashboard",
+			xOriginalURI:   "",
+			subRequestMode: false,
+			want:           true,
+		},
+		{
+			name:           "subrequest mode honors X-Original-URI",
+			regex:          "^/admin/.*",
+			urlPath:        "/auth",
+			xOriginalURI:   "/admin/secret",
+			subRequestMode: true,
+			want:           true,
+		},
+		{
+			name:           "subrequest mode falls back to URL.Path when X-Original-URI does not match",
+			regex:          "^/admin/.*",
+			urlPath:        "/admin/dashboard",
+			xOriginalURI:   "/public/index",
+			subRequestMode: true,
+			want:           true,
+		},
+		{
+			name:           "subrequest mode with empty X-Original-URI uses URL.Path",
+			regex:          "^/admin/.*",
+			urlPath:        "/admin/dashboard",
+			xOriginalURI:   "",
+			subRequestMode: true,
+			want:           true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			pc, err := NewPathChecker(tt.regex, tt.subRequestMode)
+			if err != nil {
+				t.Fatalf("NewPathChecker(%q, %v) returned error: %v", tt.regex, tt.subRequestMode, err)
+			}
+
+			req, err := http.NewRequest(http.MethodGet, "http://example.com"+tt.urlPath, nil)
+			if err != nil {
+				t.Fatalf("http.NewRequest: %v", err)
+			}
+
+			if tt.xOriginalURI != "" {
+				req.Header.Set("X-Original-URI", tt.xOriginalURI)
+			}
+
+			got, err := pc.Check(req)
+			if err != nil {
+				t.Fatalf("Check() unexpected error: %v", err)
+			}
+
+			if got != tt.want {
+				t.Errorf("Check() = %v, want %v (subRequestMode=%v, urlPath=%q, X-Original-URI=%q)",
+					got, tt.want, tt.subRequestMode, tt.urlPath, tt.xOriginalURI)
+			}
+		})
+	}
+}
@@ -60,7 +60,7 @@ func newParsedConfig(orig *config.Config) *ParsedConfig {
 	}
 }

-func ParseConfig(ctx context.Context, fin io.Reader, fname string, defaultDifficulty int, logLevel string) (*ParsedConfig, error) {
+func ParseConfig(ctx context.Context, fin io.Reader, fname string, defaultDifficulty int, logLevel string, subrequestMode bool) (*ParsedConfig, error) {
 	c, err := config.Load(fin, fname)
 	if err != nil {
 		return nil, err
@@ -152,7 +152,7 @@ func ParseConfig(ctx context.Context, fin io.Reader, fname string, defaultDiffic
 		}

 		if b.PathRegex != nil {
-			c, err := NewPathChecker(*b.PathRegex)
+			c, err := NewPathChecker(*b.PathRegex, subrequestMode)
 			if err != nil {
 				validationErrs = append(validationErrs, fmt.Errorf("while processing rule %s path regex: %w", b.Name, err))
 			} else {
@@ -19,7 +19,7 @@ func TestDefaultPolicyMustParse(t *testing.T) {
 	}
 	defer fin.Close()

-	if _, err := ParseConfig(ctx, fin, "botPolicies.yaml", anubis.DefaultDifficulty, "info"); err != nil {
+	if _, err := ParseConfig(ctx, fin, "botPolicies.yaml", anubis.DefaultDifficulty, "info", false); err != nil {
 		t.Fatalf("can't parse config: %v", err)
 	}
 }
@@ -41,7 +41,7 @@ func TestGoodConfigs(t *testing.T) {
 				defer fin.Close()

 				ctx := thothmock.WithMockThoth(t)
-				if _, err := ParseConfig(ctx, fin, fin.Name(), anubis.DefaultDifficulty, "info"); err != nil {
+				if _, err := ParseConfig(ctx, fin, fin.Name(), anubis.DefaultDifficulty, "info", false); err != nil {
 					t.Fatal(err)
 				}
 			})
@@ -53,7 +53,7 @@ func TestGoodConfigs(t *testing.T) {
 				}
 				defer fin.Close()

-				if _, err := ParseConfig(t.Context(), fin, fin.Name(), anubis.DefaultDifficulty, "info"); err != nil {
+				if _, err := ParseConfig(t.Context(), fin, fin.Name(), anubis.DefaultDifficulty, "info", false); err != nil {
 					t.Fatal(err)
 				}
 			})
@@ -77,7 +77,7 @@ func TestBadConfigs(t *testing.T) {
 			}
 			defer fin.Close()

-			if _, err := ParseConfig(ctx, fin, fin.Name(), anubis.DefaultDifficulty, "info"); err == nil {
+			if _, err := ParseConfig(ctx, fin, fin.Name(), anubis.DefaultDifficulty, "info", false); err == nil {
 				t.Fatal(err)
 			} else {
 				t.Log(err)