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#1jay0lee wants to merge 1 commit into
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….14) PR googleapis#16976 replaced pyOpenSSL with stdlib ssl but changed the SSL_CTX* pointer offset formula from the stable: ctypes.sizeof(ctypes.c_void_p) * 2 to the fragile: sys.getsizeof(object()) Python 3.14 changed the PyObject header layout, causing sys.getsizeof(object()) to return a different value. This makes _cast_ssl_ctx_to_void_p_stdlib() read garbage memory, which is passed to OpenSSL as an SSL_CTX* → segfault during mTLS handshake. The standalone google-auth-library-python repo already had the correct formula. This commit restores it. Fixes segfault on Ubuntu 26.04 (Python 3.14) when using ECP mTLS offload.
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Problem
wif-bunkersegfaults on Ubuntu 26.04 (Python 3.14) during the mTLS TLS handshake when using ECP offload.Root Cause
PR googleapis/google-cloud-python#16976 (July 2, 2026) replaced pyOpenSSL with stdlib ssl but changed the SSL_CTX* pointer offset formula in
_custom_tls_signer.py:Before (standalone repo, stable):
After (PR googleapis#16976, broken on 3.14):
Python 3.14 changed the
PyObjectheader layout, sosys.getsizeof(object())returns a different value. The wrong offset reads garbage memory, which gets passed to OpenSSL as anSSL_CTX*pointer → segfault.Fix
Restore the stable offset formula:
ctypes.sizeof(ctypes.c_void_p) * 2. This equals theob_refcnt + ob_typeheader size and is consistent across CPython versions.The standalone
google-auth-library-pythonrepo already had this correct formula — it was lost during the monorepo refactor.Testing
--use-adcmTLS handshake