craftin/PGPy-3_13_patch
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Permit skipping cross-signing unless strictly required

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This is done by setting 'crosssign' to False in the prefs parameter to
the sign function.

You probably don't want to use this feature! It is likely to make
OpenPGP certificates without cross-signatures that some other
implementations will reject.
This commit is contained in:
Daniel Kahn Gillmor
2019-06-05 15:48:07 -04:00
parent 6f4bb8d867
commit c066719eb4
1 changed files with 19 additions and 7 deletions
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26
pgpy/pgp.py
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@@ -2109,7 +2109,14 @@ class PGPKey(Armorable, ParentRef, PGPObject):
"""
Bind a subkey to this key.
Valid optional keyword arguments are identical to those of self-signatures for :py:meth:`PGPkey.certify`
In addition to the optional keyword arguments accepted for self-signatures by :py:meth:`PGPkey.certify`,
the following optional keyword arguments can be used with :py:meth:`PGPKey.bind`.
:keyword crosssign: If ``False``, do not attempt a cross-signature (defaults to ``True``). Subkeys
which are not capable of signing will not produce a cross-signature in any case.
Setting ``crosssign`` to ``False`` is likely to produce subkeys that will be rejected
by some other OpenPGP implementations.
:type crosssign: ``bool``
"""
hash_algo = prefs.pop('hash', None)
@@ -2131,19 +2138,24 @@ class PGPKey(Armorable, ParentRef, PGPObject):
if usage is not None:
sig._signature.subpackets.addnew('KeyFlags', hashed=True, flags=usage)
crosssig = None
# if possible, have the subkey create a primary key binding signature
if key.key_algorithm.can_sign:
if key.key_algorithm.can_sign and prefs.pop('crosssign', True):
subkeyid = key.fingerprint.keyid
esig = None
if not key.is_public:
esig = key.bind(self)
crosssig = key.bind(self)
elif subkeyid in self.subkeys: # pragma: no cover
esig = self.subkeys[subkeyid].bind(self)
crosssig = self.subkeys[subkeyid].bind(self)
if esig is not None:
sig._signature.subpackets.addnew('EmbeddedSignature', hashed=False, _sig=esig._signature)
if crosssig is None:
if usage is None:
raise PGPError('subkey with no key usage flags (may be used for any purpose, including signing) requires a cross-signature')
if KeyFlags.Sign in usage:
raise PGPError('subkey marked for signing usage requires a cross-signature')
else:
sig._signature.subpackets.addnew('EmbeddedSignature', hashed=False, _sig=crosssig._signature)
return self._sign(key, sig, **prefs)