it was changed in the following draft https://datatracker.ietf.org/doc/html/draft-miller-ssh-agent-03 The id 3 is now used for SSH_AGENT_CONSTRAIN_MAXSIGN key constraint, an OpenSSH extension to the protocol that we do not currently support. Instead, we added a compatibility layer for SSH_AGENT_CONSTRAIN_EXTENSION with ID 3. Fixes golang/go#62311 Change-Id: I421aee92aee9e693e43f66e6a5515c055333cb9b Reviewed-on: https://go-review.googlesource.com/c/crypto/+/525355 Reviewed-by: Matthew Dempsky <mdempsky@google.com> Run-TryBot: Nicola Murino <nicola.murino@gmail.com> Reviewed-by: Filippo Valsorda <filippo@golang.org> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Than McIntosh <thanm@google.com>