feat(lib): Add optional restrictions for JWT based on a specific header value

cmd/anubis/main.go

@@ -73,9 +73,10 @@ var (
 	versionFlag              = flag.Bool("version", false, "print Anubis version")
 	xffStripPrivate          = flag.Bool("xff-strip-private", true, "if set, strip private addresses from X-Forwarded-For")
 
-	thothInsecure = flag.Bool("thoth-insecure", false, "if set, connect to Thoth over plain HTTP/2, don't enable this unless support told you to")
-	thothURL      = flag.String("thoth-url", "", "if set, URL for Thoth, the IP reputation database for Anubis")
-	thothToken    = flag.String("thoth-token", "", "if set, API token for Thoth, the IP reputation database for Anubis")
+	thothInsecure        = flag.Bool("thoth-insecure", false, "if set, connect to Thoth over plain HTTP/2, don't enable this unless support told you to")
+	thothURL             = flag.String("thoth-url", "", "if set, URL for Thoth, the IP reputation database for Anubis")
+	thothToken           = flag.String("thoth-token", "", "if set, API token for Thoth, the IP reputation database for Anubis")
+	jwtRestrictionHeader = flag.String("jwt-restriction-header", "X-Real-IP", "If set, the JWT is only valid if the current value of this header matched the value when the JWT was created")
 )
 
 func keyFromHex(value string) (ed25519.PrivateKey, error) {
@@ -341,18 +342,19 @@ func main() {
 	}
 
 	s, err := libanubis.New(libanubis.Options{
-		BasePrefix:        *basePrefix,
-		StripBasePrefix:   *stripBasePrefix,
-		Next:              rp,
-		Policy:            policy,
-		ServeRobotsTXT:    *robotsTxt,
-		PrivateKey:        priv,
-		CookieDomain:      *cookieDomain,
-		CookieExpiration:  *cookieExpiration,
-		CookiePartitioned: *cookiePartitioned,
-		RedirectDomains:   redirectDomainsList,
-		Target:            *target,
-		WebmasterEmail:    *webmasterEmail,
+		BasePrefix:           *basePrefix,
+		StripBasePrefix:      *stripBasePrefix,
+		Next:                 rp,
+		Policy:               policy,
+		ServeRobotsTXT:       *robotsTxt,
+		PrivateKey:           priv,
+		CookieDomain:         *cookieDomain,
+		CookieExpiration:     *cookieExpiration,
+		CookiePartitioned:    *cookiePartitioned,
+		RedirectDomains:      redirectDomainsList,
+		Target:               *target,
+		WebmasterEmail:       *webmasterEmail,
+		JWTRestrictionHeader: *jwtRestrictionHeader,
 	})
 	if err != nil {
 		log.Fatalf("can't construct libanubis.Server: %v", err)

docs/docs/CHANGELOG.md

@@ -40,6 +40,11 @@ And some cleanups/refactors were added:
 - Bump AI-robots.txt to version 1.37
 - Make progress bar styling more compatible (UXP, etc)
 - Add `--strip-base-prefix` flag/envvar to strip the base prefix from request paths when forwarding to target servers
+- Add `robots2policy` CLI utility to convert robots.txt files to Anubis challenge policies using CEL expressions ([#409](https://github.com/TecharoHQ/anubis/issues/409))
+- Implement GeoIP and ASN based checks via [Thoth](https://anubis.techaro.lol/docs/admin/thoth) ([#206](https://github.com/TecharoHQ/anubis/issues/206))
+- Replace internal SHA256 hashing with xxhash for 4-6x performance improvement in policy evaluation and cache operations
+- Add [custom weight thresholds](./admin/configuration/thresholds.mdx) via CEL ([#688](https://github.com/TecharoHQ/anubis/pull/688))
+- Add optional restrictions for JWT based on the value of a header ([#697](https://github.com/TecharoHQ/anubis/pull/697))
 - Fix an off-by-one in the default threshold config
 
 Request weight is one of the biggest ticket features in Anubis. This enables Anubis to be much closer to a Web Application Firewall and when combined with custom thresholds allows administrators to have Anubis take advanced reactions. For more information about request weight, see [the request weight section](./admin/policies.mdx#request-weight) of the policy file documentation.

docs/docs/admin/installation.mdx

@@ -83,6 +83,7 @@ Anubis uses these environment variables for configuration:
 | `USE_REMOTE_ADDRESS`           | unset                   | If set to `true`, Anubis will take the client's IP from the network socket. For production deployments, it is expected that a reverse proxy is used in front of Anubis, which pass the IP using headers, instead.                                                                                                                                                                                                                                                                                       |
 | `WEBMASTER_EMAIL`              | unset                   | If set, shows a contact email address when rendering error pages. This email address will be how users can get in contact with administrators.                                                                                                                                                                                                                                                                                                                                                          |
 | `XFF_STRIP_PRIVATE`            | `true`                  | If set, strip private addresses from `X-Forwarded-For` headers. To unset this, you must set `XFF_STRIP_PRIVATE=false` or `--xff-strip-private=false`.                                                                                                                                                                                                                                                                                                                                                   |
+| `JWT_RESTRICTION_HEADER`       | `X-Real-IP`             | If set, the JWT is only valid if the current value of this header matches the value when the JWT was created. You can use it e.g. to restrict a JWT to the source IP of the user using `X-Real-IP`.                                                                                                                                                                                                                                                                                                     |
 
 <details>
 <summary>Advanced configuration settings</summary>

lib/anubis.go

@@ -189,6 +189,13 @@ func (s *Server) maybeReverseProxy(w http.ResponseWriter, r *http.Request, httpS
 		return
 	}
 
+	if s.opts.JWTRestrictionHeader != "" && claims["restriction"] != internal.SHA256sum(r.Header.Get(s.opts.JWTRestrictionHeader)) {
+		lg.Debug("JWT restriction header is invalid")
+		s.ClearCookie(w, s.cookieName, cookiePath)
+		s.RenderIndex(w, r, rule, httpStatusOnly)
+		return
+	}
+
 	r.Header.Add("X-Anubis-Status", "PASS")
 	s.ServeHTTPNext(w, r)
 }
@@ -384,12 +391,33 @@ func (s *Server) PassChallenge(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// generate JWT cookie
-	tokenString, err := s.signJWT(jwt.MapClaims{
-		"challenge":  challengeStr,
-		"method":     rule.Challenge.Algorithm,
-		"policyRule": rule.Hash(),
-		"action":     string(cr.Rule),
-	})
+	var tokenString string
+
+	// check if JWTRestrictionHeader is set and header is in request
+	if s.opts.JWTRestrictionHeader != "" {
+		if r.Header.Get(s.opts.JWTRestrictionHeader) == "" {
+			lg.Error("JWTRestrictionHeader is set in config but not found in request, please check your reverse proxy config.")
+			s.ClearCookie(w, s.cookieName, cookiePath)
+			s.respondWithError(w, r, "failed to sign JWT")
+			return
+		} else {
+			tokenString, err = s.signJWT(jwt.MapClaims{
+				"challenge":   challengeStr,
+				"method":      rule.Challenge.Algorithm,
+				"policyRule":  rule.Hash(),
+				"action":      string(cr.Rule),
+				"restriction": internal.SHA256sum(r.Header.Get(s.opts.JWTRestrictionHeader)),
+			})
+		}
+	} else {
+		tokenString, err = s.signJWT(jwt.MapClaims{
+			"challenge":  challengeStr,
+			"method":     rule.Challenge.Algorithm,
+			"policyRule": rule.Hash(),
+			"action":     string(cr.Rule),
+		})
+	}
+
 	if err != nil {
 		lg.Error("failed to sign JWT", "err", err)
 		s.ClearCookie(w, s.cookieName, cookiePath)

lib/config.go

@@ -27,20 +27,21 @@ import (
 )
 
 type Options struct {
-	Next              http.Handler
-	Policy            *policy.ParsedConfig
-	Target            string
-	CookieDomain      string
-	CookieName        string
-	BasePrefix        string
-	WebmasterEmail    string
-	RedirectDomains   []string
-	PrivateKey        ed25519.PrivateKey
-	CookieExpiration  time.Duration
-	StripBasePrefix   bool
-	OpenGraph         config.OpenGraph
-	CookiePartitioned bool
-	ServeRobotsTXT    bool
+	Next                 http.Handler
+	Policy               *policy.ParsedConfig
+	Target               string
+	CookieDomain         string
+	CookieName           string
+	BasePrefix           string
+	WebmasterEmail       string
+	RedirectDomains      []string
+	PrivateKey           ed25519.PrivateKey
+	CookieExpiration     time.Duration
+	StripBasePrefix      bool
+	OpenGraph            config.OpenGraph
+	CookiePartitioned    bool
+	ServeRobotsTXT       bool
+	JWTRestrictionHeader string
 }
 
 func LoadPoliciesOrDefault(ctx context.Context, fname string, defaultDifficulty int) (*policy.ParsedConfig, error) {