1 files changed, 26 insertions, 1 deletions

diff --git a/src/mailman_pgp/utils/pgp.py b/src/mailman_pgp/utils/pgp.py
index 4251693..621aa02 100644
--- a/src/mailman_pgp/utils/pgp.py
+++ b/src/mailman_pgp/utils/pgp.py
@@ -16,7 +16,10 @@
 # this program.  If not, see <http://www.gnu.org/licenses/>.
 
 """Miscellaneous PGP utilities."""
-from pgpy import PGPKey
+from pgpy import PGPKey, PGPSignature
+from pgpy.constants import SignatureType
+from pgpy.packet import Packet, Signature
+from pgpy.types import Armorable
 from public import public
 
 
@@ -72,3 +75,25 @@ def key_from_file(file):
     """
     key, _ = PGPKey.from_file(file)
     return key
+
+
+@public
+def revoc_from_blob(blob):
+    """
+
+    :param blob:
+    :return:
+    :rtype: pgpy.PGPSignature
+    """
+    dearm = Armorable.ascii_unarmor(blob)
+    p = Packet(dearm['body'])
+
+    if not isinstance(p, Signature):
+        raise ValueError('Not a key revocation signature.')
+    if p.sigtype not in (SignatureType.KeyRevocation,
+                         SignatureType.SubkeyRevocation):
+        raise ValueError('Not a key revocation.')
+
+    sig = PGPSignature()
+    sig |= p
+    return sig