[Bug]: Match exec "step ssh check-host %h" causes SSH connections through ProxyJump to hang #1734

Steps to Reproduce

SSH hangs when the connection involves both ProxyJump and step ssh check-host.

Using an otherwise working ProxyJump configuration:

• Without any Step invocation during SSH startup, the connection succeeds.
• Adding only the following block causes it to fail:

Match exec "step ssh check-host %h"
    ServerAliveInterval 60

The failing nested SSH connection logs:

debug3: write ERROR from cb(2):87
debug2: channel 0: write failed

This reproduces without using step ssh proxycommand, isolating the trigger to executing check-host.

We suspect Go #80979. Step 0.31.0 embeds Go 1.27.1, before the relevant fix. We have not yet verified a rebuilt Step binary containing that fix. The issue described in that patch involves Windows pipes, which explains why both ProxyJump and step ssh check-host are required for the issue

Some other notes:

• Direct connections appear fine (i.e., ProxyJump is required to reproduce)
• We know that at least Step 0.31.0 is affected
• Downgrading to Step 0.28.7 resolves the issue (with the same config)
• We haven't identified the first affected version, but the Go issue notes a regression between Go 1.24.6 and 1.26.0

Full example:

Host jumphost
    HostName jumphost.example.com

Host targethost
    HostName targethost.example.com
    ProxyJump jumphost

Match exec "step ssh check-host %h"
    ServerAliveInterval 60

Summary: Bump to Go 1.27.2 should solve this issue.

Your Environment

Windows 11
Step 0.31.0

Expected Behavior

SSH works

Actual Behavior

SSH hangs

Additional Context

No response

Contributing

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