stash

backend/authentication/signature_auth.py

@@ -16,6 +16,12 @@ def split_userhandle_or_throw(userhandle):
     return username, domain
 
 
+def split_grouphandle_or_throw(grouphandle):
+    if not grouphandle.startswith('#'):
+        raise ValueError('Group handle must be in the format #name@domain')
+    return split_userhandle_or_throw(grouphandle[1:])
+
+
 def verify_request(request, raw_request_body):
     authentication_header = request.META.get('HTTP_AUTHORIZATION')
 
@@ -74,6 +80,36 @@ def verify_incoming_friend_request(request, raw_request_body):
         return False
 
 
+def verify_incoming_group_invite(request, raw_request_body, handle_field, key_field):
+    """Self-certifying verifier for the two legs of the group invite/accept dance that land on a
+    backend which doesn't have the caller cached as a KnownIdentity yet (see
+    docs/design-in-progress/groups-mvp.md): the inviter delivering an invite to the invitee's own
+    backend (handle_field='inviter', key_field='inviter_key'), and the invitee accepting on the
+    group's home backend (handle_field='invitee', key_field='invitee_key'). Mirrors
+    verify_incoming_friend_request exactly, just with configurable field names."""
+    try:
+        username, domain, signed_data, signature_bytes_hex = verify_request(request, raw_request_body)
+    except ValueError:
+        return False
+    try:
+        claimed_handle = request.data[handle_field]
+        claimed_key = request.data[key_field]
+    except KeyError:
+        return False
+    if not claimed_handle or not claimed_key:
+        return False
+    if username + "@" + domain != claimed_handle:
+        return False
+    if len(claimed_key) != 64:
+        return False
+    verify_key = VerifyKey(bytes.fromhex(claimed_key))
+    try:
+        verify_key.verify(signed_data.encode('utf-8'), bytes.fromhex(signature_bytes_hex))
+        return True
+    except BadSignatureError:
+        return False
+
+
 def authenticate_request_against_known_identities(request, raw_request_body):
     try:
         username, domain, signed_data, signature_bytes_hex = verify_request(request, raw_request_body)