Impact
The QUIC client did not authenticate the server during the TLS 1.3 handshake. The CertificateVerify signature was not checked, the certificate chain was not validated, and the hostname was not compared against the certificate, so verify was effectively a no-op on the client. A man-in-the-middle on the network path could present any certificate and impersonate any server, defeating the confidentiality and integrity of the connection. HTTP/3 uses the same client and was equally affected. Handshakes authenticated by a PSK (session resumption) are not affected, because the peer is authenticated by the PSK binder and no certificate is sent.
Patches
Fixed in 1.4.4. The client now verifies the CertificateVerify signature, validates the certificate chain against the trust store (cacerts option, the operating system store by default), and checks the hostname. Client verify now defaults to on; set verify => false to accept any certificate (for example a self-signed test server).
Workarounds
None before 1.4.4. verify => true had no effect, and inspecting the certificate after connecting does not help because without the signature check the peer is never proven to own the certificate it presents.
Credit
Reported by benmmurphy.
References
benmmurphy Reporter
Impact
The QUIC client did not authenticate the server during the TLS 1.3 handshake. The CertificateVerify signature was not checked, the certificate chain was not validated, and the hostname was not compared against the certificate, so
verifywas effectively a no-op on the client. A man-in-the-middle on the network path could present any certificate and impersonate any server, defeating the confidentiality and integrity of the connection. HTTP/3 uses the same client and was equally affected. Handshakes authenticated by a PSK (session resumption) are not affected, because the peer is authenticated by the PSK binder and no certificate is sent.Patches
Fixed in 1.4.4. The client now verifies the CertificateVerify signature, validates the certificate chain against the trust store (
cacertsoption, the operating system store by default), and checks the hostname. Clientverifynow defaults to on; setverify => falseto accept any certificate (for example a self-signed test server).Workarounds
None before 1.4.4.
verify => truehad no effect, and inspecting the certificate after connecting does not help because without the signature check the peer is never proven to own the certificate it presents.Credit
Reported by benmmurphy.
References