Advisories for Golang/Golang.org/X/Crypto/Ssh/Agent package

For certain crafted inputs, a 'ed25519.PrivateKey' was created by casting malformed wire bytes, leading to a panic when used.

The in-memory keyring returned by NewKeyring() silently accepted keys with the ConfirmBeforeUse constraint but never enforced it. The key would sign without any confirmation prompt, with no indication to the caller that the constraint was not in effect. NewKeyring() now returns an error when unsupported constraints are requested.

When adding a key to a remote agent constraint extensions such as restrict-destination-v00@openssh.com were not serialized in the request. Destination restrictions were silently stripped when forwarding keys, allowing unrestricted use of the key on the remote host. The client now serializes all constraint extensions. Additionally, the in-memory keyring returned by NewKeyring() now rejects keys with unsupported constraint extensions instead of silently ignoring them.

SSH clients receiving SSH_AGENT_SUCCESS when expecting a typed response will panic and cause early termination of the client process.