Previously, a revoked 'SignatureKey' belonging to a CA was not correctly checked for revocation. Now, both the 'key' and 'key.SignatureKey' are checked for @revoked.
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.
Previously, CVE-2024-45337 fixed an authorization bypass for misused ssh server configurations; if any other type of callback is passed other than public key, then the source-address validation would be skipped.
The RSA and DSA public key parsers did not enforce size limits on key parameters. A crafted public key with an excessively large modulus or DSA parameter could cause several minutes of CPU consumption during signature verification. This could be triggered by unauthenticated clients during public key authentication. RSA moduli are now limited to 8192 bits, and DSA parameters are validated per FIPS 186-2.
An authenticated SSH client that repeatedly opened channels which were rejected by the server caused unbounded memory growth, eventually crashing the server process and affecting all connected users. Rejected channels are now properly removed from the connection's internal state and released for garbage collection.
A malicious SSH peer could send unsolicited global request responses to fill an internal buffer, blocking the connection's read loop. The blocked goroutine could not be released by calling Close(), resulting in a resource leak per connection. Unsolicited global responses are now discarded.
An incorrectly placed cast from bytes to int allowed for server-side panic in the AES-GCM packet decoder for well-crafted inputs.
When an SSH server authentication callback returned PartialSuccessError with non-nil Permissions, those permissions were silently discarded, potentially dropping certificate restrictions such as force-command after a second factor succeeded. Returning non-nil Permissions with PartialSuccessError now results in a connection error.
When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation.
SSH servers which use CertChecker as a public key callback without setting IsUserAuthority or IsHostAuthority could be caused to panic by a client presenting a certificate. CertChecker now returns an error instead of panicking when these callbacks are nil.
The Verify() method for FIDO/U2F security key types (sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519@openssh.com) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. To restore the previous behavior, return a "no-touch-required" extension in Permissions.Extensions from PublicKeyCallback.
SSH clients receiving SSH_AGENT_SUCCESS when expecting a typed response will panic and cause early termination of the client process.
The Go SSH library (x/crypto/ssh) by default does not verify host keys, facilitating man-in-the-middle attacks. Default behavior changed in commit e4e2799 to require explicitly registering a hostkey verification mechanism.
The x/crypto/ssh package before 0.0.0-20211202192323-5770296d904e of golang.org/x/crypto allows an attacker to panic an SSH server.
A nil pointer dereference in the golang.org/x/crypto/ssh component through v0.0.0-20201203163018-be400aefbc4c for Go allows remote attackers to cause a denial of service against SSH servers.
golang.org/x/crypto/ssh before 0.0.0-20220314234659-1baeb1ce4c0b in Go through 1.16.15 and 1.17.x through 1.17.8 allows an attacker to crash a server in certain circumstances involving AddHostKey.