e282cbb112
If the client hello legacy version is >= TLS 1.3, and no supported_versions extension is sent, negotiate TLS 1.2 or lower when supported. On the topic of supported version negotiation RFC 8446 4.2.1 indicates TLS 1.3 implementations MUST send a supported_versions extension with a list of their supported protocol versions. The crypto/tls package enforces this when the client hello legacy version indicates TLS 1.3 (0x0304), aborting the handshake with an alertMissingExtension alert if no supported_versions were received. However, section 4.2.1 indicates different behaviour should be used when the extension is not present and TLS 1.2 or prior are supported: If this extension is not present, servers which are compliant with this specification and which also support TLS 1.2 MUST negotiate TLS 1.2 or prior as specified in [RFC5246], even if ClientHello.legacy_version is 0x0304 or later. This commit updates the client hello processing logic to allow this behaviour. If no supported_versions extension was received we ignore the legacy version being >= TLS 1.3 and instead negotiate a lower supported version if the server configuration allows. This fix in turn allows enabling the BoGo ClientHelloVersionTooHigh, MinorVersionTolerance, and MajorVersionTolerance tests. Updates #72006 Change-Id: I27a2cd231e4b8762b0d9e2dbd3d8ddd5b87fd5c9 Reviewed-on: https://go-review.googlesource.com/c/go/+/671235 Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Roland Shoemaker <roland@golang.org> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> |
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