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Fix #826: Suppress cryptography FFDH deprecation warning and add decrepit fallback #830

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Fix #826: Suppress cryptography FFDH deprecation warning and add decrepit fallback #830

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dd8666e
Fix #826: Suppress cryptography FFDH deprecation warning and add decr…
sarthak-shubham Sep 27, 2026
43dd157
refactor: clean up DH warning suppression
sarthak-shubham Oct 7, 2026
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19 changes: 16 additions & 3 deletions asyncssh/crypto/dh.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,14 +20,27 @@

"""A shim around PyCA for Diffie Hellman key exchange"""

from cryptography.hazmat.primitives.asymmetric import dh
import warnings
from cryptography.utils import CryptographyDeprecationWarning

with warnings.catch_warnings():
warnings.simplefilter('ignore', CryptographyDeprecationWarning)

try:
from cryptography.hazmat.primitives.asymmetric.dh import \
DHParameterNumbers as _DHParameterNumbers, \
DHPublicNumbers as _DHPublicNumbers
except (ImportError, AttributeError):
from cryptography.hazmat.decrepit.asymmetric.dh import \
DHParameterNumbers as _DHParameterNumbers, \
DHPublicNumbers as _DHPublicNumbers


class DH:
"""A shim around PyCA for Diffie Hellman key exchange"""

def __init__(self, g: int, p: int):
self._pn = dh.DHParameterNumbers(p, g)
self._pn = _DHParameterNumbers(p, g)
self._priv_key = self._pn.parameters().generate_private_key()

def get_public(self) -> int:
Expand All @@ -40,7 +53,7 @@ def get_public(self) -> int:
def get_shared(self, peer_public: int) -> int:
"""Return the shared key from the peer's public key"""

peer_key = dh.DHPublicNumbers(peer_public, self._pn).public_key()
peer_key = _DHPublicNumbers(peer_public, self._pn).public_key()
shared_key = self._priv_key.exchange(peer_key)

return int.from_bytes(shared_key, 'big')