1 files changed, 45 insertions, 0 deletions

diff --git a/src/mailman_pgp/utils/pgp.py b/src/mailman_pgp/utils/pgp.py
index be97a75..05721b4 100644
--- a/src/mailman_pgp/utils/pgp.py
+++ b/src/mailman_pgp/utils/pgp.py
@@ -179,3 +179,48 @@ def key_usable(key, flags_required):
         if bool(verified):
             return False
     return flags_required.issubset(key_flags(key))
+
+
+@public
+def key_merge(privkey, new_key, signer_key):
+    """
+
+    :param privkey:
+    :type privkey: pgpy.PGPKey
+    :param new_key:
+    :type new_key: pgpy.PGPKey
+    """
+    if privkey.pubkey.key_material != new_key.key_material:
+        raise ValueError('You sent a wrong key.')
+
+    uid_map = {}
+    for uid in privkey.userids:
+        for uid_other in new_key.userids:
+            if uid == uid_other:
+                uid_map[uid] = uid_other
+
+    if len(uid_map) == 0:
+        raise ValueError('No signed UIDs found.')
+
+    uid_sigs = {}
+    for uid, uid_other in uid_map.items():
+        for sig in uid_other.signatures:
+            if sig in uid.signatures:
+                continue
+            if sig.signer != signer_key.fingerprint.keyid:
+                continue
+            # sig is a new signature, not currenctly on uid, ans seems to
+            # be made by the pgp_address.key
+            try:
+                verification = signer_key.verify(uid, sig)
+                if bool(verification):
+                    uid_sigs.setdefault(uid, []).append(sig)
+            except PGPError:
+                pass
+
+    if len(uid_sigs) == 0:
+        raise ValueError('No new certifications found.')
+
+    for uid, sigs in uid_sigs.items():
+        for sig in sigs:
+            uid |= sig