Fix CA pinning bypass in Python path - #71
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cisco-annikiti
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July 28, 2026 15:16
jeffreyparker
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Jul 31, 2026
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Description
Replace ssl.create_default_context() with ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT) in CertValidatingHTTPSConnection.connect() to prevent OS system CAs from being loaded alongside the bundled ca_certs.pem. Explicitly set check_hostname = True, verify_mode = CERT_REQUIRED, and disable SSLv2/SSLv3.
Motivation and Context
ssl.create_default_context() calls load_default_certs() internally, which loads the OS system trust store. The subsequent load_verify_locations(cafile=ca_certs) only ADDS bundled CAs on top - it does not replace the system CAs. This makes CA pinning a no-op: any certificate trusted by the OS is accepted even with pinning enabled. The fix ensures that when CA pinning is ON, only the bundled ca_certs.pem is used as the trust store
How Has This Been Tested?
python3 -m unittest test_duo_openvpn -v — 42 tests pass
Types of Changes