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drive/driveimpl: use sudo or su to run file server

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Some systems have `sudo`, some have `su`. This tries both, increasing
the chance that we can run the file server as an unprivileged user.

Updates #14629

Signed-off-by: Percy Wegmann <percy@tailscale.com>
This commit is contained in:
Percy Wegmann 2025-07-29 09:11:36 -05:00 committed by Percy Wegmann
parent 3d1e4f147a
commit aa6a2d1e56
1 changed files with 21 additions and 3 deletions
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24
drive/driveimpl/remote_impl.go
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@ -333,8 +333,14 @@ func (s *userServer) run() error {
args = append(args, s.Name, s.Path)
}
var cmd *exec.Cmd
if su := s.canSU(); su != "" {
s.logf("starting taildrive file server as user %q", s.username)
if s.canSudo() {
s.logf("starting taildrive file server with sudo as user %q", s.username)
allArgs := []string{"-n", "-u", s.username, s.executable}
allArgs = append(allArgs, args...)
cmd = exec.Command("sudo", allArgs...)
} else if su := s.canSU(); su != "" {
s.logf("starting taildrive file server with su as user %q", s.username)
// Quote and escape arguments. Use single quotes to prevent shell substitutions.
for i, arg := range args {
args[i] = "'" + strings.ReplaceAll(arg, "'", "'\"'\"'") + "'"
@ -343,7 +349,7 @@ func (s *userServer) run() error {
allArgs := []string{s.username, "-c", cmdString}
cmd = exec.Command(su, allArgs...)
} else {
// If we were root, we should have been able to sudo as a specific
// If we were root, we should have been able to sudo or su as a specific
// user, but let's check just to make sure, since we never want to
// access shared folders as root.
err := s.assertNotRoot()
@ -409,6 +415,18 @@ func (s *userServer) run() error {
"DELETE": true,
}
// canSudo checks wether we can sudo -u the configured executable as the
// configured user by attempting to call the executable with the '-h' flag to
// print help.
func (s *userServer) canSudo() bool {
ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
defer cancel()
if err := exec.CommandContext(ctx, "sudo", "-n", "-u", s.username, s.executable, "-h").Run(); err != nil {
return false
}
return true
}
// canSU checks whether the current process can run su with the right username.
// If su can be run, this returns the path to the su command.
// If not, this returns the empty string "".