Initial commit: Go 1.23 release state

src/syscall/exec_pdeathsig_test.go

@@ -0,0 +1,187 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build freebsd || linux
+
+package syscall_test
+
+import (
+	"bufio"
+	"fmt"
+	"internal/testenv"
+	"io"
+	"os"
+	"os/exec"
+	"os/signal"
+	"os/user"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"syscall"
+	"testing"
+)
+
+// TestDeathSignalSetuid verifies that a command run with a different UID still
+// receives PDeathsig; it is a regression test for https://go.dev/issue/9686.
+func TestDeathSignalSetuid(t *testing.T) {
+	if testing.Short() {
+		t.Skipf("skipping test that copies its binary into temp dir")
+	}
+
+	// Copy the test binary to a location that another user can read/execute
+	// after we drop privileges.
+	//
+	// TODO(bcmills): Why do we believe that another users will be able to
+	// execute a binary in this directory? (It could be mounted noexec.)
+	tempDir, err := os.MkdirTemp("", "TestDeathSignal")
+	if err != nil {
+		t.Fatalf("cannot create temporary directory: %v", err)
+	}
+	defer os.RemoveAll(tempDir)
+	os.Chmod(tempDir, 0755)
+
+	tmpBinary := filepath.Join(tempDir, filepath.Base(os.Args[0]))
+
+	src, err := os.Open(os.Args[0])
+	if err != nil {
+		t.Fatalf("cannot open binary %q, %v", os.Args[0], err)
+	}
+	defer src.Close()
+
+	dst, err := os.OpenFile(tmpBinary, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0755)
+	if err != nil {
+		t.Fatalf("cannot create temporary binary %q, %v", tmpBinary, err)
+	}
+	if _, err := io.Copy(dst, src); err != nil {
+		t.Fatalf("failed to copy test binary to %q, %v", tmpBinary, err)
+	}
+	err = dst.Close()
+	if err != nil {
+		t.Fatalf("failed to close test binary %q, %v", tmpBinary, err)
+	}
+
+	cmd := testenv.Command(t, tmpBinary)
+	cmd.Env = append(cmd.Environ(), "GO_DEATHSIG_PARENT=1")
+	chldStdin, err := cmd.StdinPipe()
+	if err != nil {
+		t.Fatalf("failed to create new stdin pipe: %v", err)
+	}
+	chldStdout, err := cmd.StdoutPipe()
+	if err != nil {
+		t.Fatalf("failed to create new stdout pipe: %v", err)
+	}
+	stderr := new(strings.Builder)
+	cmd.Stderr = stderr
+
+	err = cmd.Start()
+	defer func() {
+		chldStdin.Close()
+		cmd.Wait()
+		if stderr.Len() > 0 {
+			t.Logf("stderr:\n%s", stderr)
+		}
+	}()
+	if err != nil {
+		t.Fatalf("failed to start first child process: %v", err)
+	}
+
+	chldPipe := bufio.NewReader(chldStdout)
+
+	if got, err := chldPipe.ReadString('\n'); got == "start\n" {
+		syscall.Kill(cmd.Process.Pid, syscall.SIGTERM)
+
+		want := "ok\n"
+		if got, err = chldPipe.ReadString('\n'); got != want {
+			t.Fatalf("expected %q, received %q, %v", want, got, err)
+		}
+	} else if got == "skip\n" {
+		t.Skipf("skipping: parent could not run child program as selected user")
+	} else {
+		t.Fatalf("did not receive start from child, received %q, %v", got, err)
+	}
+}
+
+func deathSignalParent() {
+	var (
+		u   *user.User
+		err error
+	)
+	if os.Getuid() == 0 {
+		tryUsers := []string{"nobody"}
+		if testenv.Builder() != "" {
+			tryUsers = append(tryUsers, "gopher")
+		}
+		for _, name := range tryUsers {
+			u, err = user.Lookup(name)
+			if err == nil {
+				break
+			}
+			fmt.Fprintf(os.Stderr, "Lookup(%q): %v\n", name, err)
+		}
+	}
+	if u == nil {
+		// If we couldn't find an unprivileged user to run as, try running as
+		// the current user. (Empirically this still causes the call to Start to
+		// fail with a permission error if running as a non-root user on Linux.)
+		u, err = user.Current()
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			os.Exit(1)
+		}
+	}
+
+	uid, err := strconv.ParseUint(u.Uid, 10, 32)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "invalid UID: %v\n", err)
+		os.Exit(1)
+	}
+	gid, err := strconv.ParseUint(u.Gid, 10, 32)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "invalid GID: %v\n", err)
+		os.Exit(1)
+	}
+
+	cmd := exec.Command(os.Args[0])
+	cmd.Env = append(os.Environ(),
+		"GO_DEATHSIG_PARENT=",
+		"GO_DEATHSIG_CHILD=1",
+	)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	attrs := syscall.SysProcAttr{
+		Pdeathsig:  syscall.SIGUSR1,
+		Credential: &syscall.Credential{Uid: uint32(uid), Gid: uint32(gid)},
+	}
+	cmd.SysProcAttr = &attrs
+
+	fmt.Fprintf(os.Stderr, "starting process as user %q\n", u.Username)
+	if err := cmd.Start(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		if testenv.SyscallIsNotSupported(err) {
+			fmt.Println("skip")
+			os.Exit(0)
+		}
+		os.Exit(1)
+	}
+	cmd.Wait()
+	os.Exit(0)
+}
+
+func deathSignalChild() {
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, syscall.SIGUSR1)
+	go func() {
+		<-c
+		fmt.Println("ok")
+		os.Exit(0)
+	}()
+	fmt.Println("start")
+
+	buf := make([]byte, 32)
+	os.Stdin.Read(buf)
+
+	// We expected to be signaled before stdin closed
+	fmt.Println("not ok")
+	os.Exit(1)
+}