fix: handle certificate chains returned by OPC UA servers#853
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diericd wants to merge 2 commits intogopcua:mainfrom
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fix: handle certificate chains returned by OPC UA servers#853diericd wants to merge 2 commits intogopcua:mainfrom
diericd wants to merge 2 commits intogopcua:mainfrom
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Replace x509.ParseCertificate (which fails with "trailing data" when the server sends a certificate chain) with uapolicy.ParseCertificate, a new helper that uses x509.ParseCertificates and returns the first (leaf) certificate.
Remove the SecurityMode override to SignAndEncrypt in readChunk during OPN response processing. This was likely a workaround from before the isAsymmetric flag was added to signAndEncrypt/verifyAndDecrypt. The isAsymmetric check already ensures OPN messages are always encrypted regardless of the configured security mode, making the override redundant. It was harmless in SignAndEncrypt mode (a no-op) but broke Sign mode by causing MSG messages to be encrypted instead of just signed, resulting in BadSecurityChecksFailed from the server.
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Summary
Some OPC UA servers — notably Siemens WinCC OA — return a full certificate chain (leaf + intermediate/root CA certificates concatenated as DER) rather than a single DER-encoded certificate. This caused several failures:
x509.ParseCertificatefails with "trailing data" when the response contains multiple concatenated certificatesThumbprinthashed the entire chain instead of just the leaf certificate, producing a thumbprint the server didn't recognizeSecurityModeoverride toSignAndEncryptinreadChunkbrokeSignmode by encrypting MSG messages that should only be signedChanges
uapolicy.ParseCertificate— a helper that usesx509.ParseCertificates(plural) and returns the first (leaf) certificate. All call sites inuasc/secure_channel.goanduasc/secure_channel_crypto.gonow use this instead ofx509.ParseCertificate.uapolicy.Thumbprint— parse the DER bytes first and hash only the leaf certificate's raw bytes, with a fallback to hashing the full input if parsing fails.SecurityModeoverride inreadChunk— theisAsymmetricflag already ensures OPN messages use asymmetric encryption regardless of the configured security mode, making the override redundant.Tested with