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test: add test that we close stdin on SSH session close #18711

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Merged
merged 1 commit into from
Jul 2, 2025
Merged

test: add test that we close stdin on SSH session close #18711

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4 changes: 3 additions & 1 deletion agent/agentssh/agentssh.go
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Original file line number Diff line number Diff line change
Expand Up @@ -609,7 +609,9 @@ func (s *Server) startNonPTYSession(logger slog.Logger, session ssh.Session, mag
// and SSH server close may be delayed.
cmd.SysProcAttr = cmdSysProcAttr()

// to match OpenSSH, we don't actually tear a non-TTY command down, even if the session ends.
// to match OpenSSH, we don't actually tear a non-TTY command down, even if the session ends. OpenSSH closes the
// pipes to the process when the session ends; which is what happens here since we wire the command up to the
// session for I/O.
// c.f. https://github.com/coder/coder/issues/18519#issuecomment-3019118271
cmd.Cancel = nil

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77 changes: 77 additions & 0 deletions agent/agentssh/agentssh_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,9 @@ import (
"context"
"fmt"
"net"
"os"
"os/user"
"path/filepath"
"runtime"
"strings"
"sync"
Expand Down Expand Up @@ -403,6 +405,81 @@ func TestNewServer_Signal(t *testing.T) {
})
}

func TestSSHServer_ClosesStdin(t *testing.T) {
t.Parallel()
if runtime.GOOS == "windows" {
t.Skip("bash doesn't exist on Windows")
}

ctx := testutil.Context(t, testutil.WaitMedium)
logger := testutil.Logger(t)
s, err := agentssh.NewServer(ctx, logger, prometheus.NewRegistry(), afero.NewMemMapFs(), agentexec.DefaultExecer, nil)
require.NoError(t, err)
defer s.Close()
err = s.UpdateHostSigner(42)
assert.NoError(t, err)

ln, err := net.Listen("tcp", "127.0.0.1:0")
require.NoError(t, err)

done := make(chan struct{})
go func() {
defer close(done)
err := s.Serve(ln)
assert.Error(t, err) // Server is closed.
}()
defer func() {
err := s.Close()
require.NoError(t, err)
<-done
}()

c := sshClient(t, ln.Addr().String())

sess, err := c.NewSession()
require.NoError(t, err)
stdout, err := sess.StdoutPipe()
require.NoError(t, err)
stdin, err := sess.StdinPipe()
require.NoError(t, err)
defer stdin.Close()

dir := t.TempDir()
err = os.MkdirAll(dir, 0o755)
require.NoError(t, err)
filePath := filepath.Join(dir, "result.txt")

// the shell command `read` will block until data is written to stdin, or closed. It will return
// exit code 1 if it hits EOF, which is what we want to test.
cmdErrCh := make(chan error, 1)
go func() {
cmdErrCh <- sess.Start(fmt.Sprintf("echo started; read; echo \"read exit code: $?\" > %s", filePath))
}()

cmdErr := testutil.RequireReceive(ctx, t, cmdErrCh)
require.NoError(t, cmdErr)

readCh := make(chan error, 1)
go func() {
buf := make([]byte, 8)
_, err := stdout.Read(buf)
assert.Equal(t, "started\n", string(buf))
readCh <- err
}()
err = testutil.RequireReceive(ctx, t, readCh)
require.NoError(t, err)

sess.Close()

var content []byte
testutil.Eventually(ctx, t, func(_ context.Context) bool {
content, err = os.ReadFile(filePath)
return err == nil
}, testutil.IntervalFast)
require.NoError(t, err)
require.Equal(t, "read exit code: 1\n", string(content))
}

func sshClient(t *testing.T, addr string) *ssh.Client {
conn, err := net.Dial("tcp", addr)
require.NoError(t, err)
Expand Down
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