feat: glob matching for redirect domains (#1084)

* feat: glob matching for redirect domains

Signed-off-by: Xe Iaso <me@xeiaso.net>

* chore: spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

* docs: update CHANGELOG

Signed-off-by: Xe Iaso <me@xeiaso.net>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>

.github/actions/spelling/excludes.txt

@@ -88,6 +88,7 @@
 ^docs/manifest/.*$
 ^docs/static/\.nojekyll$
 ^lib/policy/config/testdata/bad/unparseable\.json$
+^internal/glob/glob_test.go$
 ignore$
 robots.txt
 ^lib/localization/locales/.*\.json$

docs/docs/CHANGELOG.md

@@ -43,6 +43,7 @@ A new ["proof of React"](./admin/configuration/challenges/preact.mdx) has been a
 - Add a default block rule for Alibaba Cloud.
 - Added support to use Traefik forwardAuth middleware.
 - Add X-Request-URI support so that Subrequest Authentication has path support.
+- Added glob matching for `REDIRECT_DOMAINS`. You can pass `*.bugs.techaro.lol` to allow redirecting to anything ending with `.bugs.techaro.lol`. There is a limit of 4 wildcards.
 
 ### Fixes
 

internal/glob/glob.go

@@ -0,0 +1,61 @@
+package glob
+
+import "strings"
+
+const GLOB = "*"
+
+const maxGlobParts = 5
+
+// Glob will test a string pattern, potentially containing globs, against a
+// subject string. The result is a simple true/false, determining whether or
+// not the glob pattern matched the subject text.
+func Glob(pattern, subj string) bool {
+	// Empty pattern can only match empty subject
+	if pattern == "" {
+		return subj == pattern
+	}
+
+	// If the pattern _is_ a glob, it matches everything
+	if pattern == GLOB {
+		return true
+	}
+
+	parts := strings.Split(pattern, GLOB)
+
+	if len(parts) > maxGlobParts {
+		return false // Pattern is too complex, reject it.
+	}
+
+	if len(parts) == 1 {
+		// No globs in pattern, so test for equality
+		return subj == pattern
+	}
+
+	leadingGlob := strings.HasPrefix(pattern, GLOB)
+	trailingGlob := strings.HasSuffix(pattern, GLOB)
+	end := len(parts) - 1
+
+	// Go over the leading parts and ensure they match.
+	for i := 0; i < end; i++ {
+		idx := strings.Index(subj, parts[i])
+
+		switch i {
+		case 0:
+			// Check the first section. Requires special handling.
+			if !leadingGlob && idx != 0 {
+				return false
+			}
+		default:
+			// Check that the middle parts match.
+			if idx < 0 {
+				return false
+			}
+		}
+
+		// Trim evaluated text from subj as we loop over the pattern.
+		subj = subj[idx+len(parts[i]):]
+	}
+
+	// Reached the last section. Requires special handling.
+	return trailingGlob || strings.HasSuffix(subj, parts[end])
+}

internal/glob/glob_test.go

@@ -0,0 +1,189 @@
+package glob
+
+import "testing"
+
+func TestGlob_EqualityAndEmpty(t *testing.T) {
+	cases := []struct {
+		name    string
+		pattern string
+		subj    string
+		want    bool
+	}{
+		{"exact match", "hello", "hello", true},
+		{"exact mismatch", "hello", "hell", false},
+		{"empty pattern and subject", "", "", true},
+		{"empty pattern with non-empty subject", "", "x", false},
+		{"pattern star matches empty", "*", "", true},
+		{"pattern star matches anything", "*", "anything at all", true},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := Glob(tc.pattern, tc.subj); got != tc.want {
+				t.Fatalf("Glob(%q,%q) = %v, want %v", tc.pattern, tc.subj, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestGlob_LeadingAndTrailing(t *testing.T) {
+	cases := []struct {
+		name    string
+		pattern string
+		subj    string
+		want    bool
+	}{
+		{"prefix match - minimal", "foo*", "foo", true},
+		{"prefix match - extended", "foo*", "foobar", true},
+		{"prefix mismatch - not at start", "foo*", "xfoo", false},
+		{"suffix match - minimal", "*foo", "foo", true},
+		{"suffix match - extended", "*foo", "xfoo", true},
+		{"suffix mismatch - not at end", "*foo", "foox", false},
+		{"contains match", "*foo*", "barfoobaz", true},
+		{"contains mismatch - missing needle", "*foo*", "f", false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := Glob(tc.pattern, tc.subj); got != tc.want {
+				t.Fatalf("Glob(%q,%q) = %v, want %v", tc.pattern, tc.subj, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestGlob_MiddleAndOrder(t *testing.T) {
+	cases := []struct {
+		name    string
+		pattern string
+		subj    string
+		want    bool
+	}{
+		{"middle wildcard basic", "f*o", "fo", true},
+		{"middle wildcard gap", "f*o", "fZZZo", true},
+		{"middle wildcard requires start f", "f*o", "xfyo", false},
+		{"order enforced across parts", "a*b*c*d", "axxbxxcxxd", true},
+		{"order mismatch fails", "a*b*c*d", "abdc", false},
+		{"must end with last part when no trailing *", "*foo*bar", "zzfooqqbar", true},
+		{"failing when trailing chars remain", "*foo*bar", "zzfooqqbarzz", false},
+		{"first part must start when no leading *", "foo*bar", "zzfooqqbar", false},
+		{"works with overlapping content", "ab*ba", "ababa", true},
+		{"needle not found fails", "foo*bar", "foobaz", false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := Glob(tc.pattern, tc.subj); got != tc.want {
+				t.Fatalf("Glob(%q,%q) = %v, want %v", tc.pattern, tc.subj, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestGlob_ConsecutiveStarsAndEmptyParts(t *testing.T) {
+	cases := []struct {
+		name    string
+		pattern string
+		subj    string
+		want    bool
+	}{
+		{"double star matches anything", "**", "", true},
+		{"double star matches anything non-empty", "**", "abc", true},
+		{"consecutive stars behave like single", "a**b", "ab", true},
+		{"consecutive stars with gaps", "a**b", "axxxb", true},
+		{"consecutive stars + trailing star", "a**b*", "axxbzzz", true},
+		{"consecutive stars still enforce anchors", "a**b", "xaBy", false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := Glob(tc.pattern, tc.subj); got != tc.want {
+				t.Fatalf("Glob(%q,%q) = %v, want %v", tc.pattern, tc.subj, got, tc.want)
+			}
+		})
+	}
+}
+
+func TestGlob_MaxPartsLimit(t *testing.T) {
+	// Allowed: up to 4 '*' (5 parts)
+	allowed := []struct {
+		pattern string
+		subj    string
+		want    bool
+	}{
+		{"a*b*c*d*e", "axxbxxcxxdxxe", true}, // 4 stars -> 5 parts
+		{"*a*b*c*d", "zzzaaaabbbcccddd", true},
+		{"a*b*c*d*e", "abcde", true},
+		{"a*b*c*d*e", "abxdxe", false}, // missing 'c' should fail
+	}
+	for _, tc := range allowed {
+		if got := Glob(tc.pattern, tc.subj); got != tc.want {
+			t.Fatalf("allowed pattern Glob(%q,%q) = %v, want %v", tc.pattern, tc.subj, got, tc.want)
+		}
+	}
+
+	// Disallowed: 5 '*' (6 parts) -> always false by complexity check
+	disallowed := []struct {
+		pattern string
+		subj    string
+	}{
+		{"a*b*c*d*e*f", "aXXbYYcZZdQQeRRf"},
+		{"*a*b*c*d*e*", "abcdef"},
+		{"******", "anything"}, // 6 stars -> 7 parts
+	}
+	for _, tc := range disallowed {
+		if got := Glob(tc.pattern, tc.subj); got {
+			t.Fatalf("disallowed pattern should fail Glob(%q,%q) = %v, want false", tc.pattern, tc.subj, got)
+		}
+	}
+}
+
+func TestGlob_CaseSensitivity(t *testing.T) {
+	cases := []struct {
+		pattern string
+		subj    string
+		want    bool
+	}{
+		{"FOO*", "foo", false},
+		{"*Bar", "bar", false},
+		{"Foo*Bar", "FooZZZBar", true},
+	}
+	for _, tc := range cases {
+		if got := Glob(tc.pattern, tc.subj); got != tc.want {
+			t.Fatalf("Glob(%q,%q) = %v, want %v", tc.pattern, tc.subj, got, tc.want)
+		}
+	}
+}
+
+func TestGlob_EmptySubjectInteractions(t *testing.T) {
+	cases := []struct {
+		pattern string
+		subj    string
+		want    bool
+	}{
+		{"*a", "", false},
+		{"a*", "", false},
+		{"**", "", true},
+		{"*", "", true},
+	}
+	for _, tc := range cases {
+		if got := Glob(tc.pattern, tc.subj); got != tc.want {
+			t.Fatalf("Glob(%q,%q) = %v, want %v", tc.pattern, tc.subj, got, tc.want)
+		}
+	}
+}
+
+func BenchmarkGlob(b *testing.B) {
+	patterns := []string{
+		"*", "*foo*", "foo*bar", "a*b*c*d*e", "a**b*", "*needle*end",
+	}
+	subjects := []string{
+		"", "foo", "barfoo", "foobarbaz", "axxbxxcxxdxxe", "zzfooqqbarzz",
+		"lorem ipsum dolor sit amet, consectetur adipiscing elit",
+	}
+	for _, p := range patterns {
+		for _, s := range subjects {
+			b.Run(p+"::"+s, func(b *testing.B) {
+				for i := 0; i < b.N; i++ {
+					_ = Glob(p, s)
+				}
+			})
+		}
+	}
+}

lib/anubis.go

@@ -11,7 +11,6 @@ import (
 	"net"
 	"net/http"
 	"net/url"
-	"slices"
 	"strings"
 	"time"
 
@@ -435,7 +434,7 @@ func (s *Server) PassChallenge(w http.ResponseWriter, r *http.Request) {
 		s.respondWithError(w, r, localizer.T("redirect_not_parseable"))
 		return
 	}
-	if (len(urlParsed.Host) > 0 && len(s.opts.RedirectDomains) != 0 && !slices.Contains(s.opts.RedirectDomains, urlParsed.Host)) || urlParsed.Host != r.URL.Host {
+	if (len(urlParsed.Host) > 0 && len(s.opts.RedirectDomains) != 0 && !matchRedirectDomain(s.opts.RedirectDomains, urlParsed.Host)) || urlParsed.Host != r.URL.Host {
 		lg.Debug("domain not allowed", "domain", urlParsed.Host)
 		s.respondWithError(w, r, localizer.T("redirect_domain_not_allowed"))
 		return

lib/http.go

@@ -7,12 +7,12 @@ import (
 	"net/http"
 	"net/url"
 	"regexp"
-	"slices"
 	"strings"
 	"time"
 
 	"github.com/TecharoHQ/anubis"
 	"github.com/TecharoHQ/anubis/internal"
+	"github.com/TecharoHQ/anubis/internal/glob"
 	"github.com/TecharoHQ/anubis/lib/challenge"
 	"github.com/TecharoHQ/anubis/lib/localization"
 	"github.com/TecharoHQ/anubis/lib/policy"
@@ -24,6 +24,26 @@ import (
 
 var domainMatchRegexp = regexp.MustCompile(`^((xn--)?[a-z0-9]+(-[a-z0-9]+)*\.)+[a-z]{2,}$`)
 
+// matchRedirectDomain returns true if host matches any of the allowed redirect
+// domain patterns. Patterns may contain '*' which are matched using the
+// internal glob matcher. Matching is case-insensitive on hostnames.
+func matchRedirectDomain(allowed []string, host string) bool {
+	h := strings.ToLower(strings.TrimSpace(host))
+ 	for _, pat := range allowed {
+ 		p := strings.ToLower(strings.TrimSpace(pat))
+ 		if strings.Contains(p, glob.GLOB) {
+ 			if glob.Glob(p, h) {
+ 				return true
+ 			}
+ 			continue
+ 		}
+ 		if p == h {
+ 			return true
+ 		}
+ 	}
+ 	return false
+}
+
 type CookieOpts struct {
 	Value  string
 	Host   string
@@ -217,8 +237,8 @@ func (s *Server) constructRedirectURL(r *http.Request) (string, error) {
 	if proto == "" || host == "" || uri == "" {
 		return "", errors.New(localizer.T("missing_required_forwarded_headers"))
 	}
-	// Check if host is allowed in RedirectDomains
+	// Check if host is allowed in RedirectDomains (supports '*' via glob)
-	if len(s.opts.RedirectDomains) > 0 && !slices.Contains(s.opts.RedirectDomains, host) {
+	if len(s.opts.RedirectDomains) > 0 && !matchRedirectDomain(s.opts.RedirectDomains, host) {
 		lg := internal.GetRequestLogger(s.logger, r)
 		lg.Debug("domain not allowed", "domain", host)
 		return "", errors.New(localizer.T("redirect_domain_not_allowed"))
@@ -290,7 +310,7 @@ func (s *Server) ServeHTTPNext(w http.ResponseWriter, r *http.Request) {
 
 		hostNotAllowed := len(urlParsed.Host) > 0 &&
 			len(s.opts.RedirectDomains) != 0 &&
-			!slices.Contains(s.opts.RedirectDomains, urlParsed.Host)
+			!matchRedirectDomain(s.opts.RedirectDomains, urlParsed.Host)
 		hostMismatch := r.URL.Host != "" && urlParsed.Host != r.URL.Host
 
 		if hostNotAllowed || hostMismatch {