Join GitHub today
GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.Sign up
crypto/tls: back RSA-PSS out of TLS 1.2 in Go 1.13 #32425
8834353 enabled again RSA-PSS in TLS 1.2. Unfortunately, there are broken
TLS 1.3 requires RSA-PSS, so there is no way around ripping this band-aid off, but partially because of this TLS 1.3 was opt-in in Go 1.12 and is opt-out in Go 1.13 (#30055). RSA-PSS in TLS 1.2 would just be enabled with no way to turn it off, and both adding another
What finally tipped the scale is that #28660 provides a nice way for code to opt-out of RSA-PSS in TLS 1.2 if needed. Let's wait to force RSA-PSS in TLS 1.2 until Go 1.14, when TLS 1.3 is also forced on, and there is a code path to disabling it.
Signing with RSA-PSS can uncover faulty crypto.Signer implementations, and it can fail for (broken) small keys. We'll have to take that breakage eventually, but it would be nice for it to be opt-out at first. TLS 1.3 requires RSA-PSS and is opt-out in Go 1.13. Instead of making a TLS 1.3 opt-out influence a TLS 1.2 behavior, let's wait to add RSA-PSS to TLS 1.2 until TLS 1.3 is on without opt-out. Note that since the Client Hello is sent before a protocol version is selected, we have to advertise RSA-PSS there to support TLS 1.3. That means that we still support RSA-PSS on the client in TLS 1.2 for verifying server certificates, which is fine, as all issues arise on the signing side. We have to be careful not to pick (or consider available) RSA-PSS on the client for client certificates, though. We'd expect tests to change only in TLS 1.2: * the server won't pick PSS to sign the key exchange (Server-TLSv12-* w/ RSA, TestHandshakeServerRSAPSS); * the server won't advertise PSS in CertificateRequest (Server-TLSv12-ClientAuthRequested*, TestClientAuth); * and the client won't pick PSS for its CertificateVerify (Client-TLSv12-ClientCert-RSA-*, TestHandshakeClientCertRSAPSS, Client-TLSv12-Renegotiate* because "R" requests a client cert). Client-TLSv13-ClientCert-RSA-RSAPSS was updated because of a fix in the test. This effectively reverts 8834353. Testing was made more complex by the undocumented semantics of OpenSSL's -[client_]sigalgs (see openssl/openssl#9172). Updates golang#32425 Change-Id: Iaddeb2df1f5c75cd090cc8321df2ac8e8e7db349 Reviewed-on: https://go-review.googlesource.com/c/go/+/182339 Reviewed-by: Adam Langley <firstname.lastname@example.org>