build(deps): bump charm.land/ssh from 0.4.2 to 0.4.3 in the go-modules group

[dependabot]

Bumps the go-modules group with 1 update: charm.land/ssh.

Updates charm.land/ssh from 0.4.2 to 0.4.3

Release notes

Sourced from charm.land/ssh's releases.

v0.4.3

What's New in charm.land/ssh v0.4.3

A small release that fixes a data race in connection deadline handling.

If your server sets both HandshakeTimeout and IdleTimeout, running under -race would turn up something like this:

WARNING: DATA RACE
Write at 0x00c000a95468 by goroutine 347:
  charm.land/ssh.(*Server).handleConn()
Previous read at 0x00c000a95468 by goroutine 348:

charm.land/ssh.(*serverConn).updateDeadline()

charm.land/ssh.(*serverConn).Read()

golang.org/x/crypto/ssh.(*handshakeTransport).readLoop()

The server clears the handshake deadline once the handshake finishes. By that point crypto/ssh has already started its read loop, and every read consults that same deadline whenever IdleTimeout is set. Nothing stood between the two.

The field is now guarded by a mutex and every access goes through it.

srv := &ssh.Server{
    HandshakeTimeout: 30 * time.Second,
    IdleTimeout:      10 * time.Minute,
}

There's nothing to configure. Upgrade and the warning goes away.

The racing write lands after the handshake has already succeeded, so it could never widen the window for an unauthenticated connection. The handshake deadline had done its job by then. The only problem was that a stale read could leave a connection holding a deadline it should have dropped, and a torn read could hand SetDeadline an incorrect value.

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Commits

• 7273fef v0.4.3
• e934df5 ci: sync golangci-lint config (#55)
• 26f0c8c fix: guard handshakeDeadline against concurrent access
• See full diff in compare view

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[dependabot]

Looks like charm.land/ssh is updatable in another way, so this is no longer needed.