Support connecting to Windows OpenSSH agent over named pipe

[antoineco]

Windows 11 connects to the built-in OpenSSH agent over a named pipe (\\.\pipe\openssh-ssh-agent).

This doesn't seem supported in libssh-rs.
The syntax IdentityAgent \\.\pipe\openssh-ssh-agent — which works with Window's built-in OpenSSH client (OpenSSH_for_Windows_8.6p1, LibreSSL 3.4.3) — is recognized as a UNIX socket instead of a Windows named pipe, at least in WezTerm:

libssh::ssh_socket_unix   > Error from connect(\\.\pipe\openssh-ssh-agent): No such file or directory

Ref.

• wez/wezterm#3772
• https://github.com/PowerShell/openssh-portable

[wez]

This needs support from the underlying ssh library. Please file an issue in the upstream:
https://gitlab.com/libssh/libssh-mirror/-/issues

[antoineco]

I assumed too fast that libssh already supported that because v0.10.0 claims to have "support for ssh-agent on Windows" (cf. CHANGELOG). I'll dig upstream 👍

edit: ah! You added that feature! libssh/libssh-mirror@51a53cc