rustls-webpki 0.103 accepts only X.509 v3 certs and returns
`UnsupportedCertVersion` for anything older, aborting the mTLS handshake at
the `CertificateVerify` step before it ever checks the signature. The
moonlight-embedded client family (moonlight-embedded, aurora-tv, …) still mint
self-signed **v2** certs with no keyUsage extension, so pairing fails against
punktfunk while it works against Sunshine — whose OpenSSL verify callback never
inspects the cert version. (aurora-tv PR #53 worked around this client-side by
switching to v3 + keyUsage; this fixes it host-side for stock clients too.)
The cert's X.509 version and extensions carry no security weight here: the
client cert is self-signed and pinned by SHA-256 (`peer_is_paired`), and the PIN
pairing ceremony is the real proof of identity. The property that DOES matter —
that the peer holds the private key for the cert it presented — is still
enforced: when webpki rejects the cert we re-run exactly that `CertificateVerify`
check with a version-agnostic parser (x509-parser SPKI + the same `rsa` verify
`pairing::verify256` uses). This is a full cryptographic check, never a bypass:
a bad signature still fails, and non-RSA / unsupported schemes fall through to
webpki's original error. Matches Sunshine's leniency without loosening the
pinned trust model.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehlerandClaude Opus 4.8
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