add a sanity alg/enc check on self-encrypted AES GCM JWTs

bump to 2.4.14.3rc0

Signed-off-by: Hans Zandbelt <[email protected]>

ChangeLog

@@ -1,3 +1,7 @@
+07/12/2023
+- add a sanity alg/enc check on self-encrypted AES GCM JWTs
+- bump to 2.4.14.3rc0
+
 06/05/2023
 - avoid using encryption keys as signing keys for request objects and private_key_jwt token endpoint auth
 - log the first Redis error as a warning before retrying

configure.ac

@@ -1,4 +1,4 @@
-AC_INIT([mod_auth_openidc],[2.4.14.2],[[email protected]])
+AC_INIT([mod_auth_openidc],[2.4.14.3rc0],[[email protected]])
 
 AC_SUBST(NAMEVER, AC_PACKAGE_TARNAME()-AC_PACKAGE_VERSION())
 

src/mod_auth_openidc.h

@@ -701,7 +701,7 @@ void oidc_proto_state_set_timestamp_now(oidc_proto_state_t *proto_state);
 
 apr_byte_t oidc_proto_token_endpoint_auth(request_rec *r, oidc_cfg *cfg, const char *token_endpoint_auth, const char *client_id, const char *client_secret, const apr_array_header_t *client_keys, const char *audience, apr_table_t *params, const char *bearer_access_token, char **basic_auth_str, char **bearer_auth_str);
 
-char *oidc_proto_peek_jwt_header(request_rec *r, const char *jwt, char **alg);
+char *oidc_proto_peek_jwt_header(request_rec *r, const char *jwt, char **alg, char **enc);
 int oidc_proto_authorization_request(request_rec *r, struct oidc_provider_t *provider, const char *login_hint, const char *redirect_uri, const char *state, oidc_proto_state_t *proto_state, const char *id_token_hint, const char *code_challenge, const char *auth_request_params, const char *path_scope);
 apr_byte_t oidc_proto_is_post_authorization_response(request_rec *r, oidc_cfg *cfg);
 apr_byte_t oidc_proto_is_redirect_authorization_response(request_rec *r, oidc_cfg *cfg);

src/oauth.c

@@ -575,7 +575,7 @@ static apr_byte_t oidc_oauth_validate_jwt_access_token(request_rec *r,
 		oidc_cfg *c, const char *access_token, json_t **token, char **response) {
 
 	oidc_debug(r, "enter: JWT access_token header=%s",
-			oidc_proto_peek_jwt_header(r, access_token, NULL));
+			oidc_proto_peek_jwt_header(r, access_token, NULL, NULL));
 
 	oidc_jose_error_t err;
 	oidc_jwk_t *jwk = NULL;

src/proto.c

@@ -464,7 +464,7 @@ char* oidc_proto_create_request_object(request_rec *r,
 	json_decref(request_object_config);
 
 	oidc_debug(r, "serialized request object JWT header = \"%s\"",
-			oidc_proto_peek_jwt_header(r, serialized_request_object, NULL));
+			oidc_proto_peek_jwt_header(r, serialized_request_object, NULL, NULL));
 	oidc_debug(r, "serialized request object = \"%s\"",
 			serialized_request_object);
 
@@ -1635,7 +1635,7 @@ apr_byte_t oidc_proto_jwt_verify(request_rec *r, oidc_cfg *cfg, oidc_jwt_t *jwt,
  * return the compact-encoded JWT header contents
  */
 char* oidc_proto_peek_jwt_header(request_rec *r,
-		const char *compact_encoded_jwt, char **alg) {
+		const char *compact_encoded_jwt, char **alg, char **enc) {
 	char *input = NULL, *result = NULL;
 	char *p = strstr(compact_encoded_jwt ? compact_encoded_jwt : "", ".");
 	if (p == NULL) {
@@ -1649,12 +1649,19 @@ char* oidc_proto_peek_jwt_header(request_rec *r,
 		oidc_warn(r, "oidc_base64url_decode returned an error");
 		return NULL;
 	}
-	if (alg) {
+	if ((alg != NULL) || (enc != NULL)) {
 		json_t *json = NULL;
 		oidc_util_decode_json_object(r, result, &json);
-		if (json)
-			*alg = apr_pstrdup(r->pool,
-					json_string_value(json_object_get(json, CJOSE_HDR_ALG)));
+		if (json) {
+			if (alg)
+				*alg = apr_pstrdup(r->pool,
+						json_string_value(
+								json_object_get(json, CJOSE_HDR_ALG)));
+			if (enc)
+				*enc = apr_pstrdup(r->pool,
+						json_string_value(
+								json_object_get(json, CJOSE_HDR_ENC)));
+		}
 		json_decref(json);
 	}
 	return result;
@@ -1669,7 +1676,7 @@ apr_byte_t oidc_proto_parse_idtoken(request_rec *r, oidc_cfg *cfg,
 
 	char *alg = NULL;
 	oidc_debug(r, "enter: id_token header=%s",
-			oidc_proto_peek_jwt_header(r, id_token, &alg));
+			oidc_proto_peek_jwt_header(r, id_token, &alg, NULL));
 	apr_hash_t *decryption_keys = NULL;
 
 	char buf[APR_RFC822_DATE_LEN + 1];
@@ -2170,7 +2177,7 @@ static apr_byte_t oidc_user_info_response_validate(request_rec *r,
 			|| (provider->userinfo_encrypted_response_alg != NULL)
 			|| (provider->userinfo_encrypted_response_enc != NULL)) {
 		oidc_debug(r, "JWT header=%s",
-				oidc_proto_peek_jwt_header(r, *response, &alg));
+				oidc_proto_peek_jwt_header(r, *response, &alg, NULL));
 	}
 
 	oidc_jose_error_t err;

src/util.c

@@ -268,9 +268,18 @@ apr_byte_t oidc_util_jwt_verify(request_rec *r, const char *secret,
 	char *plaintext = NULL;
 	int plaintext_len = 0;
 
+	char *alg = NULL;
+	char *enc = NULL;
+	oidc_proto_peek_jwt_header(r, compact_encoded_jwt, &alg, &enc);
+	if ((_oidc_strcmp(alg, CJOSE_HDR_ALG_DIR) != 0)
+			|| (_oidc_strcmp(enc, CJOSE_HDR_ENC_A256GCM) != 0)) {
+		oidc_error(r, "corrupted JWE header, alg=\"%s\" enc=\"%s\"", alg, enc);
+		goto end;
+	}
+
 	if (oidc_jwe_decrypt(r->pool, compact_encoded_jwt, keys, &plaintext,
 			&plaintext_len, &err, FALSE) == FALSE) {
-		oidc_error(r, "decrypting JWT failed: %s", oidc_jose_e2s(r->pool, err));
+		oidc_error(r, "decrypting JWE failed: %s", oidc_jose_e2s(r->pool, err));
 		goto end;
 	}