Signals end every command, not only ssh to and ssh install (closes #48)

SIGINT, SIGTERM and SIGHUP were caught for the whole run, but only the
ssh and sftp children acted on them: the mnemonic prompt waited for
Enter, and an interrupted `age encrypt -o` went on to put the
encryption of the cut-off input in place. Now `ssh to` and
`ssh install` catch them from once the mnemonic is read until their
cleanup has run, and `age encrypt -o` and `age decrypt -o` catch them
while they write, to remove the unfinished file and exit with status 1;
everywhere else they end the tool at once. Tests cover an interrupted
`age encrypt -o` and `age decrypt -o` and the install working directory
on a signal.

Model: opus-5-5

README.md

@@ -288,6 +288,15 @@ girl mad pet galaxy egg matter matrix prison refuse sense ordinary nose
 Errors go to standard error and the exit status is 1, except for `ssh to`, which
 passes through `ssh`'s own exit status.
 
+SIGINT, SIGTERM and SIGHUP end any command at once, at the mnemonic prompt too,
+with the status a shell gives a program killed by that signal (130 for SIGINT).
+An interrupted `age encrypt -o` or `age decrypt -o` leaves no file: it removes
+the unfinished file it was writing, leaves a file already at the named path as
+it was, and exits with status 1. While `ssh to` or `ssh install` has `ssh` or
+`sftp` running, the signal ends that program instead, the tool removes its agent
+socket or working files, and it exits with status 1, or for `ssh to` with
+`ssh`'s own status if `ssh` reported one.
+
 ## Entrypoints
 
 The repo adheres to the

internal/cli/age/age.go

@@ -6,7 +6,9 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"os/signal"
 	"path/filepath"
+	"syscall"
 
 	"github.com/spf13/cobra"
 	"sneak.berlin/go/keyfunc/internal/agekey"
@@ -185,16 +187,38 @@ func output(cmd *cobra.Command) (io.Writer, func(error) error, error) {
 		}, nil
 	}
 
+	// From before the new file is made until it is renamed or removed,
+	// a signal removes it and ends the tool with status 1, even while
+	// the work is blocked reading its input, so an interrupted run
+	// leaves no file.
+	signals := make(chan os.Signal, 1)
+	signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)
+
 	// The file is made in the same directory so that putting it in
 	// place is a rename and never a copy, and it is readable only by
 	// its owner, which is the mode it keeps once renamed.
 	file, err := os.CreateTemp(filepath.Dir(name), filepath.Base(name)+".")
 	if err != nil {
+		signal.Stop(signals)
+
 		return nil, nil, fmt.Errorf("creating a file beside %s: %w", name, err)
 	}
 
+	go func() {
+		if _, received := <-signals; received {
+			_ = os.Remove(file.Name())
+
+			os.Exit(1)
+		}
+	}()
+
 	return file, func(failed error) error {
-		return finish(file, name, failed)
+		finished := finish(file, name, failed)
+
+		signal.Stop(signals)
+		close(signals)
+
+		return finished
 	}, nil
 }
 

internal/cli/age_test.go

@@ -1,10 +1,14 @@
 package cli_test
 
 import (
+	"io"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"strings"
+	"syscall"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/require"
 	"sneak.berlin/go/keyfunc/internal/agekey"
@@ -90,6 +94,78 @@ func TestARefusedDecryptionLeavesTheOutputFileAlone(t *testing.T) {
 	require.Equal(t, "what was already there\n", string(kept))
 }
 
+func TestASignalStopsAnEncryptionAndLeavesNoFile(t *testing.T) {
+	t.Setenv(mnemonic.Variable, example())
+
+	for _, ending := range []os.Signal{
+		syscall.SIGTERM, syscall.SIGINT, syscall.SIGHUP,
+	} {
+		interrupted(t, ending, "encrypt", "the start of the secret\n")
+	}
+}
+
+func TestASignalStopsADecryptionAndLeavesNoFile(t *testing.T) {
+	t.Setenv(mnemonic.Variable, example())
+
+	// All of an encryption but its last byte, so the tool reads the
+	// header and then waits for the rest.
+	sealed := run(t, "age", "encrypt", written(t, "notes.txt", "the secret\n"))
+	cut := sealed[:len(sealed)-1]
+
+	for _, ending := range []os.Signal{
+		syscall.SIGTERM, syscall.SIGINT, syscall.SIGHUP,
+	} {
+		interrupted(t, ending, "decrypt", cut)
+	}
+}
+
+// interrupted runs "age encrypt -o" or "age decrypt -o", as the
+// operation says, as a subprocess writing into a directory of its own
+// and reading the input from a pipe that stays open. It waits until the
+// tool has begun writing the file beside the one it was named, and
+// sends it the signal. The tool has to end on the signal alone, with
+// status 1, and leave the directory empty. A tool that went on reading
+// would not end until the input did; one that did not remove the file
+// it was writing would leave it there, with what it had written so far.
+func interrupted(t *testing.T, signal os.Signal, operation, input string) {
+	t.Helper()
+
+	name := operation + " " + signal.String()
+	directory := t.TempDir()
+
+	//nolint:gosec // the binary is this test's own, re-run as the tool
+	command := exec.CommandContext(
+		t.Context(), os.Args[0], "age", operation,
+		"-o", filepath.Join(directory, "notes"),
+	)
+
+	command.Env = append(os.Environ(), runAsTool+"=1")
+
+	producer, err := command.StdinPipe()
+	require.NoError(t, err)
+	require.NoError(t, command.Start())
+
+	_, err = io.WriteString(producer, input)
+	require.NoError(t, err)
+
+	// The file beside the named one is made once the mnemonic has been
+	// read, before any input is.
+	require.Eventually(t, func() bool {
+		entries, err := os.ReadDir(directory)
+
+		return err == nil && len(entries) > 0
+	}, 5*time.Second, 5*time.Millisecond)
+
+	require.NoError(t, command.Process.Signal(signal))
+	waitForTool(t, name, command)
+
+	require.Equal(t, 1, command.ProcessState.ExitCode(), name)
+
+	left, err := os.ReadDir(directory)
+	require.NoError(t, err)
+	require.Empty(t, left, name)
+}
+
 // written puts the contents in a file of that name in a directory of
 // this test's own and returns the path to it.
 func written(t *testing.T, name, contents string) string {

internal/cli/cli.go

@@ -2,13 +2,10 @@
 package cli
 
 import (
-	"context"
 	"errors"
 	"fmt"
 	"os"
-	"os/signal"
 	"runtime/debug"
-	"syscall"
 
 	"github.com/spf13/cobra"
 	"sneak.berlin/go/keyfunc/internal/cli/age"
@@ -70,18 +67,15 @@ func Root() *cobra.Command {
 // ended with. ssh has already said whatever it had to say in that
 // case, so nothing more is printed.
 //
-// SIGINT, SIGTERM and SIGHUP cancel the command's context instead of
-// killing the process outright, so the child ssh or sftp ends and the
-// deferred cleanup that removes the agent socket and the install
-// working directory still runs.
+// SIGINT, SIGTERM and SIGHUP end the tool at once, as they end any Go
+// program, so a command waiting at the mnemonic prompt or reading what
+// it encrypts or decrypts goes no further. The exceptions catch the
+// signals to clean up first: "ssh to" and "ssh install" while they
+// have ssh or sftp running, so the child ends and their own cleanup
+// still runs, and "age encrypt -o" and "age decrypt -o" while they
+// write, so the unfinished file is removed.
 func Main() int {
-	ctx, stop := signal.NotifyContext(
-		context.Background(),
-		syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP,
-	)
-	defer stop()
-
-	err := Root().ExecuteContext(ctx)
+	err := Root().Execute()
 	if err == nil {
 		return 0
 	}

internal/cli/ssh/install.go

@@ -8,9 +8,11 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
+	"os/signal"
 	"path/filepath"
 	"slices"
 	"strings"
+	"syscall"
 
 	"github.com/spf13/cobra"
 )
@@ -62,6 +64,17 @@ func install() *cobra.Command {
 				return err
 			}
 
+			// From here on a signal cancels the context, which
+			// sftp runs under, instead of ending the tool, so sftp
+			// ends and the working directory is still removed.
+			ctx, stop := signal.NotifyContext(
+				cmd.Context(),
+				syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP,
+			)
+			defer stop()
+
+			cmd.SetContext(ctx)
+
 			return add(cmd, args[0], args[1:], line)
 		},
 	}

internal/cli/ssh/to.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
+	"os/signal"
 	"slices"
 	"syscall"
 
@@ -42,7 +43,17 @@ func to() *cobra.Command {
 				return err
 			}
 
-			served, err := key.Serve(cmd.Context(), comment)
+			// From here until the agent is taken down, a signal
+			// cancels the context instead of ending the tool, so
+			// ssh ends and the socket and its directory are still
+			// removed.
+			ctx, stop := signal.NotifyContext(
+				cmd.Context(),
+				syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP,
+			)
+			defer stop()
+
+			served, err := key.Serve(ctx, comment)
 			if err != nil {
 				return err
 			}
@@ -53,7 +64,7 @@ func to() *cobra.Command {
 				"-o", "IdentityAgent=" + served.Socket(),
 			}, args)
 
-			return connect(cmd.Context(), argv)
+			return connect(ctx, argv)
 		},
 	}
 
@@ -76,7 +87,7 @@ func connect(ctx context.Context, argv []string) error {
 	command.Stdout = os.Stdout
 	command.Stderr = os.Stderr
 
-	// A cancelled context means a signal ended the tool. Send ssh a
+	// A cancelled context means a signal arrived. Send ssh a
 	// SIGTERM rather than the default kill, so it puts the terminal
 	// back the way it found it before it goes.
 	command.Cancel = func() error {

internal/cli/ssh_test.go

@@ -20,13 +20,13 @@ import (
 
 // runAsTool, set in the environment of a re-executed test binary, tells
 // TestMain to run the tool through Main rather than the suite, so the
-// signal test can drive the real signal path in a process it can send a
-// signal to.
+// signal tests can drive the real signal path in a process they can
+// send a signal to.
 const runAsTool = "KEYFUNC_TEST_RUN_AS_TOOL"
 
 // TestMain re-executes the test binary as the tool when runAsTool is
-// set, and otherwise runs the suite. The signal test starts the tool
-// this way, as a subprocess it can signal and watch clean up.
+// set, and otherwise runs the suite. The signal tests start the tool
+// this way, as a subprocess they can signal and watch end.
 func TestMain(m *testing.M) {
 	if os.Getenv(runAsTool) == "1" {
 		os.Exit(cli.Main())
@@ -209,6 +209,16 @@ fi
 sleep 5
 `
 
+// stalled is a stand-in for the system sftp that notes it has started
+// and then blocks, so a test can signal the tool while sftp is running
+// and watch it remove its working directory. The exec keeps the shell
+// from leaving a sleep behind that holds the output the tool reads sftp
+// through.
+const stalled = `
+touch "$KEYFUNC_TEST_STARTED"
+exec sleep 5
+`
+
 // pretended is where a stand-in writes down what it was asked to do.
 type pretended struct {
 	// home stands in for the home directory on the host.
@@ -544,7 +554,7 @@ func TestASignalTakesTheAgentDirectoryDown(t *testing.T) {
 // ssh that blocks, waits until the agent is up and ssh is running
 // against it, sends the tool the signal, and requires the agent socket
 // and its directory to be gone once the tool has ended. The subprocess
-// goes through Main and its signal handling, so with that handling
+// goes through Main and the command's signal handling, so with that handling
 // removed the signal kills the tool outright, no deferred cleanup runs,
 // the directory is left behind, and the check fails.
 func signalEndsTheTool(t *testing.T, name string, signal os.Signal) {
@@ -611,6 +621,56 @@ func waitForSocket(t *testing.T, noted string) string {
 	return socket
 }
 
+func TestASignalTakesTheInstallWorkingDirectoryDown(t *testing.T) {
+	t.Setenv(mnemonic.Variable, example())
+
+	for _, ending := range []os.Signal{
+		syscall.SIGTERM, syscall.SIGINT, syscall.SIGHUP,
+	} {
+		signalEndsTheInstall(t, ending.String(), ending)
+	}
+}
+
+// signalEndsTheInstall runs "ssh install" as a subprocess against a
+// stand-in sftp that blocks, with a temporary directory of the test's
+// own, waits until sftp is running, sends the tool the signal, and
+// requires the working directory the tool made there to be gone once
+// the tool has ended.
+func signalEndsTheInstall(t *testing.T, name string, signal os.Signal) {
+	t.Helper()
+
+	temporary := t.TempDir()
+	started := filepath.Join(t.TempDir(), "started")
+	t.Setenv("KEYFUNC_TEST_STARTED", started)
+	standIn(t, "sftp", stalled)
+
+	//nolint:gosec // the binary is this test's own, re-run as the tool
+	command := exec.CommandContext(
+		t.Context(), os.Args[0], subcommand, installing, host,
+	)
+
+	command.Env = append(os.Environ(), runAsTool+"=1", "TMPDIR="+temporary)
+	require.NoError(t, command.Start())
+
+	// sftp is started only once the working directory has been made.
+	require.Eventually(t, func() bool {
+		_, err := os.Stat(started)
+
+		return err == nil
+	}, 5*time.Second, 5*time.Millisecond)
+
+	working, err := os.ReadDir(temporary)
+	require.NoError(t, err)
+	require.Len(t, working, 1, name)
+
+	require.NoError(t, command.Process.Signal(signal))
+	waitForTool(t, name, command)
+
+	left, err := os.ReadDir(temporary)
+	require.NoError(t, err)
+	require.Empty(t, left, name)
+}
+
 func TestTheMnemonicIsNotHandedToSFTP(t *testing.T) {
 	t.Setenv(mnemonic.CommandVariable, "echo "+example())
 	t.Setenv(mnemonic.Variable, example())