TODO.md

@@ -25,6 +25,13 @@ Bring the repo into policy compliance in one commit:
 
 # Completed Steps
 
+- 2026-10-03: Key material is wiped on every exit: `Entry()` returns
+  the exit code after its deferred `memguard.Purge()` has run, and only
+  `main` calls `os.Exit`. SIGINT and SIGTERM go through memguard's
+  handler, which wipes every buffer before exiting; when the process is
+  in the terminal's foreground process group it first restores the
+  terminal settings from startup, so an interrupted passphrase prompt no
+  longer leaves echo off.
 - 2026-10-03: Every command that builds a path from a secret name
   checks the name first with `vault.ValidateSecretName` and touches
   nothing when it is invalid: `rm`, `mv` (both names, within a vault

cmd/secret/main.go

@@ -1,8 +1,12 @@
 // Package main is the entry point for the secret CLI application.
 package main
 
-import "git.eeqj.de/sneak/secret/internal/cli"
+import (
+	"os"
+
+	"git.eeqj.de/sneak/secret/internal/cli"
+)
 
 func main() {
-	cli.Entry()
+	os.Exit(cli.Entry())
 }

internal/cli/entry_test.go

@@ -0,0 +1,108 @@
+package cli_test
+
+import (
+	"bufio"
+	"context"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"git.eeqj.de/sneak/secret/internal/cli"
+	"git.eeqj.de/sneak/secret/internal/secret"
+	"github.com/awnumar/memguard"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// Entry must return its exit code rather than exit, so that its deferred
+// memguard purge runs on the success and the error path alike.
+//
+//nolint:paralleltest // sets os.Args, and Entry wipes every buffer in the process
+func TestEntryWipesBuffersAndReturnsExitCode(t *testing.T) {
+	savedArgs := os.Args
+
+	t.Cleanup(func() { os.Args = savedArgs })
+
+	tests := []struct {
+		args     []string
+		exitCode int
+	}{
+		{args: []string{"secret", "--help"}, exitCode: 0},
+		{args: []string{"secret", "no-such-command"}, exitCode: 1},
+	}
+
+	for _, tt := range tests {
+		buf := memguard.NewBufferFromBytes([]byte("key material"))
+		os.Args = tt.args
+
+		assert.Equal(t, tt.exitCode, cli.Entry(), "exit code for %v", tt.args)
+		assert.False(t, buf.IsAlive(), "Entry left a buffer unwiped for %v", tt.args)
+	}
+}
+
+// Ctrl-C while `secret add` waits for the value on stdin must end the
+// process through memguard's signal handler, which wipes every buffer and
+// exits with status 1, not through Go's default handling, which kills the
+// process with the buffers intact.
+func TestInterruptExitsThroughMemguard(t *testing.T) {
+	t.Parallel()
+
+	const waitingForValue = "Reading secret value from stdin"
+
+	ctx, cancel := context.WithTimeout(t.Context(), time.Minute)
+	defer cancel()
+
+	wd, err := filepath.Abs("../..")
+	require.NoError(t, err)
+
+	secretPath := filepath.Join(wd, "secret")
+	env := []string{
+		secret.EnvStateDir + "=" + t.TempDir(),
+		secret.EnvMnemonic + "=" + testMnemonic,
+		secret.EnvUnlockPassphrase + "=test-passphrase",
+		"PATH=/usr/bin:/bin",
+		// The debug log on stderr shows when add starts waiting for the value.
+		"GODEBUG=berlin.sneak.pkg.secret",
+	}
+
+	//nolint:gosec // G204: test executes the freshly built secret binary
+	initCmd := exec.CommandContext(ctx, secretPath, "init")
+	initCmd.Env = env
+
+	output, err := initCmd.CombinedOutput()
+	require.NoError(t, err, "init should succeed: %s", output)
+
+	//nolint:gosec // G204: test executes the freshly built secret binary
+	addCmd := exec.CommandContext(ctx, secretPath, "add", "test/secret")
+	addCmd.Env = env
+
+	// Held open and never written, so add keeps waiting for the value.
+	stdin, err := addCmd.StdinPipe()
+	require.NoError(t, err)
+
+	defer func() { _ = stdin.Close() }()
+
+	stderr, err := addCmd.StderrPipe()
+	require.NoError(t, err)
+	require.NoError(t, addCmd.Start())
+
+	waiting := false
+
+	scanner := bufio.NewScanner(stderr)
+	for !waiting && scanner.Scan() {
+		waiting = strings.Contains(scanner.Text(), waitingForValue)
+	}
+
+	require.True(t, waiting, "add never logged %q", waitingForValue)
+	require.NoError(t, addCmd.Process.Signal(os.Interrupt))
+
+	err = addCmd.Wait()
+
+	var exitErr *exec.ExitError
+
+	require.ErrorAs(t, err, &exitErr)
+	assert.Equal(t, 1, exitErr.ExitCode(), "add ended with %v", err)
+}

internal/cli/root.go

@@ -4,17 +4,38 @@ import (
 	"os"
 
 	"git.eeqj.de/sneak/secret/internal/secret"
+	"github.com/awnumar/memguard"
 	"github.com/spf13/cobra"
+	"golang.org/x/sys/unix"
+	"golang.org/x/term"
 )
 
-// Entry is the entry point for the secret CLI application
-func Entry() {
-	cmd := newRootCmd()
+// Entry runs the secret CLI and returns the process exit code. It wipes
+// every memguard buffer before it returns, so the caller must do nothing
+// but exit with the code.
+func Entry() int {
+	// On SIGINT or SIGTERM memguard runs this function, wipes every buffer
+	// and exits with status 1. The passphrase prompt turns terminal echo
+	// off until the read finishes, so a signal there would leave echo off.
+	// Only a process in the terminal's foreground process group may reset
+	// it: one in the background that tries is stopped instead of exiting.
+	terminalState, terminalErr := term.GetState(unix.Stdin)
 
-	err := cmd.Execute()
+	memguard.CatchSignal(func(os.Signal) {
+		foreground, err := unix.IoctlGetInt(unix.Stdin, unix.TIOCGPGRP)
+		if terminalErr == nil && err == nil && foreground == unix.Getpgrp() {
+			_ = term.Restore(unix.Stdin, terminalState)
+		}
+	}, os.Interrupt, unix.SIGTERM)
+
+	defer memguard.Purge()
+
+	err := newRootCmd().Execute()
 	if err != nil {
-		os.Exit(1)
+		return 1
 	}
+
+	return 0
 }
 
 func newRootCmd() *cobra.Command {