Merge pull request #3051 from greatroar/sanitize-env

Sanitize environment before starting backend processes (rclone, ssh)

internal/backend/foreground.go

@@ -0,0 +1,26 @@
+package backend
+
+import (
+	"os"
+	"os/exec"
+	"strings"
+)
+
+// StartForeground runs cmd in the foreground, by temporarily switching to the
+// new process group created for cmd. The returned function `bg` switches back
+// to the previous process group.
+//
+// The command's environment has all RESTIC_* variables removed.
+func StartForeground(cmd *exec.Cmd) (bg func() error, err error) {
+	env := os.Environ() // Returns a copy that we can modify.
+
+	cmd.Env = env[:0]
+	for _, kv := range env {
+		if strings.HasPrefix(kv, "RESTIC_") {
+			continue
+		}
+		cmd.Env = append(cmd.Env, kv)
+	}
+
+	return startForeground(cmd)
+}

internal/backend/foreground_solaris.go

@@ -7,10 +7,7 @@ import (
 	"github.com/restic/restic/internal/errors"
 )
 
-// StartForeground runs cmd in the foreground, by temporarily switching to the
-// new process group created for cmd. The returned function `bg` switches back
-// to the previous process group.
-func StartForeground(cmd *exec.Cmd) (bg func() error, err error) {
+func startForeground(cmd *exec.Cmd) (bg func() error, err error) {
 	// run the command in it's own process group so that SIGINT
 	// is not sent to it.
 	cmd.SysProcAttr = &syscall.SysProcAttr{

internal/backend/foreground_test.go

@@ -0,0 +1,38 @@
+// +build !windows
+
+package backend_test
+
+import (
+	"bufio"
+	"os"
+	"os/exec"
+	"strings"
+	"testing"
+
+	"github.com/restic/restic/internal/backend"
+	rtest "github.com/restic/restic/internal/test"
+)
+
+func TestForeground(t *testing.T) {
+	err := os.Setenv("RESTIC_PASSWORD", "supersecret")
+	rtest.OK(t, err)
+
+	cmd := exec.Command("env")
+	stdout, err := cmd.StdoutPipe()
+	rtest.OK(t, err)
+
+	bg, err := backend.StartForeground(cmd)
+	rtest.OK(t, err)
+	defer cmd.Wait()
+
+	err = bg()
+	rtest.OK(t, err)
+
+	sc := bufio.NewScanner(stdout)
+	for sc.Scan() {
+		if strings.HasPrefix(sc.Text(), "RESTIC_PASSWORD=") {
+			t.Error("subprocess got to see the password")
+		}
+	}
+	rtest.OK(t, err)
+}

internal/backend/foreground_unix.go

@@ -24,10 +24,7 @@ func tcsetpgrp(fd int, pid int) error {
 	return errno
 }
 
-// StartForeground runs cmd in the foreground, by temporarily switching to the
-// new process group created for cmd. The returned function `bg` switches back
-// to the previous process group.
-func StartForeground(cmd *exec.Cmd) (bg func() error, err error) {
+func startForeground(cmd *exec.Cmd) (bg func() error, err error) {
 	// open the TTY, we need the file descriptor
 	tty, err := os.OpenFile("/dev/tty", os.O_RDWR, 0)
 	if err != nil {

internal/backend/foreground_windows.go

@@ -6,10 +6,7 @@ import (
 	"github.com/restic/restic/internal/errors"
 )
 
-// StartForeground runs cmd in the foreground, by temporarily switching to the
-// new process group created for cmd. The returned function `bg` switches back
-// to the previous process group.
-func StartForeground(cmd *exec.Cmd) (bg func() error, err error) {
+func startForeground(cmd *exec.Cmd) (bg func() error, err error) {
 	// just start the process and hope for the best
 	err = cmd.Start()
 	if err != nil {