feat: add support for rotating jwt keys

This allows jwt_secret to have multiple ',' separated secrets. The
first/leftmost should be used to sign new JWTs. All of them are used
(starting from left/newest) to try to verify a JWT.

If the first secret is < 32 chars in length JWTs are disabled. If any
of the other secrets are < 32 chars, the configuration code causes the
software to exit. This prevents insecure (too short) secrets from
being used.

Updated doc examples and tests.

CHANGES.txt

@@ -141,6 +141,8 @@ Features:
 - the roundup-admin history command now dumps the journal entries
   in a more human readable format. Use the raw option to get the older
   machine parsible output. (John Rouillard)
+- Multiple JWT secrets are supported to allow key rotation. See
+  an updated config.ini for details. (John Rouillard)
 
 
 2023-07-13 2.3.0

doc/rest.txt

@@ -2071,7 +2071,9 @@ only been tested with python3)::
                 claim['roles'] = newroles
             else:
                 claim['roles'] = user_roles
-            secret = self.db.config.WEB_JWT_SECRET
+
+            # Sign with newest/first secret.
+            secret = self.db.config.WEB_JWT_SECRET[0]
             myjwt = jwt.encode(claim, secret, algorithm='HS256')
 
             # if jwt.__version__ >= 2.0.0 jwt.encode() returns string
@@ -2090,7 +2092,10 @@ only been tested with python3)::
 
             myjwt = input['jwt'].value
 
-            secret = self.db.config.WEB_JWT_SECRET
+            secret = self.db.config.WEB_JWT_SECRET[0]
+
+            # only return decoded result if the newest signing key
+            # is used. Have older keys report an invalid signature.
             try:
                 result = jwt.decode(myjwt, secret,
                                     algorithms=['HS256'],

roundup/cgi/client.py

@@ -1111,23 +1111,42 @@ def authenticate_bearer_token(self, challenge):
             self.setHeader("WWW-Authenticate", "Basic")
             raise LoginError('Support for jwt disabled.')
 
-        secret = self.db.config.WEB_JWT_SECRET
-        if len(secret) < 32:
+
+        # If first ',' separated token is < 32, jwt is disabled.
+        # If second or later tokens are < 32 chars, the config system
+        # stops the tracker from starting so insecure tokens can not
+        # be used.
+        if len(self.db.config.WEB_JWT_SECRET[0]) < 32:
             # no support for jwt, this is fine.
             self.setHeader("WWW-Authenticate", "Basic")
             raise LoginError('Support for jwt disabled by admin.')
 
-        try:  # handle jwt exceptions
-            token = jwt.decode(challenge, secret,
-                               algorithms=['HS256'],
-                               audience=self.db.config.TRACKER_WEB,
-                               issuer=self.db.config.TRACKER_WEB)
-        except jwt.exceptions.InvalidTokenError as err:
-            self.setHeader("WWW-Authenticate", "Basic, Bearer")
-            self.make_user_anonymous()
-            raise LoginError(str(err))
+        last_error = "Unknown error validating bearer token."
+
+        for secret in self.db.config.WEB_JWT_SECRET:
+            try:  # handle jwt exceptions
+                token = jwt.decode(challenge, secret,
+                                   algorithms=['HS256'],
+                                   audience=self.db.config.TRACKER_WEB,
+                                   issuer=self.db.config.TRACKER_WEB)
+                return (token)
+
+            except jwt.exceptions.InvalidSignatureError as err:
+                # Try more signatures.
+                # If all signatures generate InvalidSignatureError,
+                # we exhaust the loop and last_error is used to
+                # report the final (but not only) InvalidSignatureError
+                last_error = str(err)  # preserve for end of loop
+            except jwt.exceptions.InvalidTokenError as err:
+                self.setHeader("WWW-Authenticate", "Basic, Bearer")
+                self.make_user_anonymous()
+                raise LoginError(str(err))
+
+        # reach here only if no valid signature was found
+        self.setHeader("WWW-Authenticate", "Basic, Bearer")
+        self.make_user_anonymous()
+        raise LoginError(last_error)
 
-        return (token)
 
     def determine_user(self, is_api=False):
         """Determine who the user is"""

roundup/configuration.py

@@ -826,6 +826,25 @@ class SecretNullableOption(NullableOption, SecretOption):
     get = SecretOption.get
     class_description = SecretOption.class_description
 
+class ListSecretOption(SecretOption):
+    # use get from SecretOption
+    def get(self):
+        value = SecretOption.get(self)
+        return [x.lstrip() for x in value.split(',')]
+
+    class_description = SecretOption.class_description
+
+    def validate(self, options):
+        if self.name == "WEB_JWT_SECRET":
+            secrets = self.get()
+            invalid_secrets = [ x for x in secrets[1:] if len(x) < 32]
+            if invalid_secrets:
+                raise OptionValueError(
+                    self, ", ".join(secrets),
+                    "One or more secrets less then 32 characters in length\n"
+                    "found: %s" % ', '.join(invalid_secrets))
+        else:
+            self.get()
 
 class RedisUrlOption(SecretNullableOption):
     """Do required check to make sure known bad parameters are not
@@ -1437,14 +1456,20 @@ def str2value(self, value):
             "(Note the default value changes every time\n"
             "     roundup-admin updateconfig\n"
             "is run, so it must be explicitly set to a non-empty string.\n"),
-        (SecretNullableOption, "jwt_secret", "disabled",
-            "This is used to generate/validate json web tokens (jwt).\n"
-            "Even if you don't use jwts it must not be empty.\n"
-            "If less than 256 bits (32 characters) in length it will\n"
-            "disable use of jwt. Changing this invalidates all jwts\n"
-            "issued by the roundup instance requiring *all* users to\n"
-            "generate new jwts. This is experimental and disabled by\n"
-            "default. It must be persistent across application restarts.\n"),
+        (ListSecretOption, "jwt_secret", "disabled",
+            "This is used to sign/validate json web tokens\n"
+            "(JWT). Even if you don't use JWTs it must not be\n"
+            "empty. You can use multiple secrets separated by a\n"
+            "comma ','. This allows for secret rotation. The newest\n"
+            "secret should be placed first and used for signing. The\n"
+            "rest of the secrets are used for validating an old JWT.\n"
+            "If the first secret is less than 256 bits (32\n"
+            "characters) in length JWTs are disabled. If other secrets\n"
+            "are less than 32 chars, the application will exit. Removing\n"
+            "a secret from this list invalidates all JWTs signed with\n"
+            "the secret. JWT support is experimental and disabled by\n"
+            "default. The secrets must be persistent across\n"
+            "application restarts.\n"),
     )),
     ("rdbms", (
         (DatabaseBackend, 'backend', NODEFAULT,