utils/settrans: improve --chroot functionality

Add an option '--chroot-chdir' to settrans and make it chdir to this
directory before executing the target program.  Also, look up the
executable in PATH.

With these changes we no longer need to use the shell inside the
chroot in the convenience scripts, and hence do not require it to be
installed inside the chroot.

* utils/fakeroot.sh: Simplify using the new option.
* utils/remap.sh: Likewise.
* utils/settrans.c (OPT_CHROOT_CHDIR): New constant.
(options): New option 'chroot-chdir'.
(main): Handle new option. Search for target executable in PATH.
* utils/fakeauth.c (main): Likewise.

4 files changed, 47 insertions, 20 deletions

diff --git a/utils/fakeauth.c b/utils/fakeauth.c
index ba6a3eef..004cc469 100644
--- a/utils/fakeauth.c
+++ b/utils/fakeauth.c
@@ -402,9 +402,13 @@ believe it has restricted them to different identities or no identity at all.\
   {
     task_t newtask;
     process_t proc;
-    file_t execfile = file_name_lookup (argv[argi], O_EXEC, 0);
+    char *prefixed_name;
+    file_t execfile = file_name_path_lookup (argv[argi], getenv ("PATH"),
+					     O_EXEC, 0, &prefixed_name);
     if (execfile == MACH_PORT_NULL)
       error (3, errno, "%s", argv[argi]);
+    if (prefixed_name)
+      argv[0] = prefixed_name;
 
     err = task_create (mach_task_self (),
 #ifdef KERN_INVALID_LEDGER
diff --git a/utils/fakeroot.sh b/utils/fakeroot.sh
index 6993365d..7bc5dc73 100644
--- a/utils/fakeroot.sh
+++ b/utils/fakeroot.sh
@@ -54,12 +54,9 @@ if [ $# -eq 0 ]; then
   set -- ${SHELL:-/bin/sh}
 fi
 
-# We exec settrans, which execs the "fakeauth" command in the chroot context.
-# The `pwd` is evaluated here and now, and that result interpreted inside
-# the shell running under fakeauth to chdir there inside the chroot world.
-# That shell then execs our arguments as a command line.
-exec /bin/settrans --chroot \
-     /bin/fakeauth \
-     /bin/sh -c 'cd "$1" || exit ; shift ; exec "$@"' \
-     "$1" "$PWD" "$@" \
-     -- / /hurd/fakeroot
+# We exec settrans, which execs the "fakeauth" command in the chroot
+# context provided by /hurd/fakeroot.
+exec /bin/settrans \
+     --chroot-chdir "$PWD" \
+     --chroot /bin/fakeauth "$@" -- \
+     / /hurd/fakeroot
diff --git a/utils/remap.sh b/utils/remap.sh
index f24ed0e7..40c2d76e 100644
--- a/utils/remap.sh
+++ b/utils/remap.sh
@@ -57,11 +57,9 @@ if [ $# -eq 0 ]; then
   set -- ${SHELL:-/bin/sh}
 fi
 
-# We exec settrans, which execs the "fakeauth" command in the chroot context.
-# The `pwd` is evaluated here and now, and that result interpreted inside
-# the shell running under fakeauth to chdir there inside the chroot world.
-# That shell then execs our arguments as a command line.
-exec /bin/settrans --chroot \
-     /bin/sh -c 'cd "$1" || exit ; shift ; exec "$@"' \
-     "$1" "$PWD" "$@" \
-     -- / /hurd/remap $MAPPED
+# We exec settrans, which execs the target command in the chroot
+# context provided by /hurd/remap.
+exec /bin/settrans \
+     --chroot-chdir "$PWD" \
+     --chroot "$@" -- \
+     / /hurd/remap $MAPPED
diff --git a/utils/settrans.c b/utils/settrans.c
index cd40c56f..00cc358c 100644
--- a/utils/settrans.c
+++ b/utils/settrans.c
@@ -18,6 +18,7 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
 
+#include <assert.h>
 #include <hurd.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -45,6 +46,8 @@ const char *argp_program_version = STANDARD_HURD_VERSION (settrans);
 #define _STRINGIFY(arg) #arg
 #define STRINGIFY(arg) _STRINGIFY (arg)
 
+#define OPT_CHROOT_CHDIR	-1
+
 static struct argp_option options[] =
 {
   {"active",      'a', 0, 0, "Start TRANSLATOR and set it as NODE's active translator" },
@@ -65,6 +68,9 @@ static struct argp_option options[] =
   {"chroot",      'C', 0, 0,
    "Instead of setting the node's translator, take following arguments up to"
    " `--' and run that command chroot'd to the translated node."},
+  {"chroot-chdir",      OPT_CHROOT_CHDIR, "DIR", 0,
+   "Change to DIR before running the chrooted command.  "
+   "DIR must be an absolute path."},
 
   {0,0,0,0, "When setting the passive translator, if there's an active translator:"},
   {"goaway",      'g', 0, 0, "Ask the active translator to go away"},
@@ -114,6 +120,7 @@ main(int argc, char *argv[])
   int excl = 0;
   int timeout = DEFAULT_TIMEOUT * 1000; /* ms */
   char **chroot_command = 0;
+  char *chroot_chdir = "/";
 
   /* Parse our options...  */
   error_t parse_opt (int key, char *arg, struct argp_state *state)
@@ -183,6 +190,12 @@ main(int argc, char *argv[])
 	  argp_error (state, "--chroot command must be terminated with `--'");
 	  return EINVAL;
 
+	case OPT_CHROOT_CHDIR:
+	  if (arg[0] != '/')
+	    argp_error (state, "--chroot-chdir must be absolute");
+	  chroot_chdir = arg;
+	  break;
+
 	case 'c': lookup_flags |= O_CREAT; break;
 	case 'L': lookup_flags &= ~O_NOTRANS; break;
 
@@ -325,6 +338,8 @@ main(int argc, char *argv[])
 	  char retry_name[1024];	/* XXX */
 	  retry_type do_retry;
 	  mach_port_t root;
+	  file_t executable;
+	  char *prefixed_name;
 	  err = fsys_getroot (active_control,
 			      MACH_PORT_NULL, MACH_MSG_TYPE_COPY_SEND,
 			      NULL, 0, NULL, 0, 0,
@@ -341,8 +356,21 @@ main(int argc, char *argv[])
 	  if (setcrdir (root))
 	    error (7, errno, "cannot install root port");
 	  mach_port_deallocate (mach_task_self (), root);
-	  if (chdir ("/"))
-	    error (8, errno, "cannot chdir to new root");
+	  if (chdir (chroot_chdir))
+	    error (8, errno, "%s", chroot_chdir);
+
+	  /* Lookup executable in PATH.  */
+	  executable = file_name_path_lookup (chroot_command[0],
+					      getenv ("PATH"),
+					      O_EXEC, 0,
+					      &prefixed_name);
+	  if (MACH_PORT_VALID (executable))
+	    {
+	      err = mach_port_deallocate (mach_task_self (), executable);
+	      assert_perror (err);
+	      if (prefixed_name)
+		chroot_command[0] = prefixed_name;
+	    }
 
 	  execvp (chroot_command[0], chroot_command);
 	  error (8, errno, "cannot execute %s", chroot_command[0]);