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fix(auth): Python 3.14 segfault in mTLS SSL_CTX pointer extraction #1

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fix(auth): Python 3.14 segfault in mTLS SSL_CTX pointer extraction #1

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8 changes: 7 additions & 1 deletion packages/google-auth/google/auth/transport/_custom_tls_signer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,13 @@ def _cast_ssl_ctx_to_void_p_stdlib(context):
"Custom TLS signing is only supported on standard release CPython runtimes."
)

offset = sys.getsizeof(object())
# Use a stable offset to reach the SSL_CTX* inside CPython's
# PySSLContext struct. The previous formula
# sys.getsizeof(object())
# broke on Python 3.14 because the PyObject header size changed.
# ctypes.sizeof(c_void_p) * 2 equals the ob_refcnt + ob_type
# header and is consistent across CPython versions.
offset = ctypes.sizeof(ctypes.c_void_p) * 2
return ctypes.c_void_p.from_address(id(context) + offset)


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