pack: Factorize 'exec_in_user_namespace' wrapper.
* gnu/packages/aux-files/run-in-namespace.c (exec_in_user_namespace): New function, with code taken from... (main): ... here. Call it.
This commit is contained in:
Ludovic Courtès
parent
14928af2af
commit
bdb9b4e8d3
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@ -219,6 +219,83 @@ disallow_setgroups (pid_t pid)
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close (fd);
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}
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/* Run the wrapper program in a separate mount user namespace. Return only
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upon failure. */
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static void
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exec_in_user_namespace (const char *store, int argc, char *argv[])
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{
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/* Spawn @WRAPPED_PROGRAM@ in a separate namespace where STORE is
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bind-mounted in the right place. */
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int err;
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char *new_root = mkdtemp (strdup ("/tmp/guix-exec-XXXXXX"));
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char *new_store = concat (new_root, "@STORE_DIRECTORY@");
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char *cwd = get_current_dir_name ();
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/* Create a child with separate namespaces and set up bind-mounts from
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there. That way, bind-mounts automatically disappear when the child
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exits, which simplifies cleanup for the parent. Note: clone is more
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convenient than fork + unshare since the parent can directly write
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the child uid_map/gid_map files. */
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pid_t child = syscall (SYS_clone, SIGCHLD | CLONE_NEWNS | CLONE_NEWUSER,
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NULL, NULL, NULL);
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switch (child)
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{
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case 0:
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/* Note: Due to <https://bugzilla.kernel.org/show_bug.cgi?id=183461>
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we cannot make NEW_ROOT a tmpfs (which would have saved the need
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for 'rm_rf'.) */
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bind_mount ("/", new_root);
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mkdir_p (new_store);
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err = mount (store, new_store, "none", MS_BIND | MS_REC | MS_RDONLY,
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NULL);
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if (err < 0)
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assert_perror (errno);
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chdir (new_root);
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err = chroot (new_root);
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if (err < 0)
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assert_perror (errno);
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/* Change back to where we were before chroot'ing. */
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chdir (cwd);
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int err = execv ("@WRAPPED_PROGRAM@", argv);
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if (err < 0)
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assert_perror (errno);
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break;
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case -1:
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/* Failure: user namespaces not supported. */
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fprintf (stderr, "%s: error: 'clone' failed: %m\n", argv[0]);
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rm_rf (new_root);
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break;
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default:
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{
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/* Map the current user/group ID in the child's namespace (the
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default is to get the "overflow UID", i.e., the UID of
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"nobody"). We must first disallow 'setgroups' for that
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process. */
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disallow_setgroups (child);
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write_id_map (child, "uid_map", getuid ());
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write_id_map (child, "gid_map", getgid ());
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int status;
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waitpid (child, &status, 0);
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chdir ("/"); /* avoid EBUSY */
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rm_rf (new_root);
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free (new_root);
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if (WIFEXITED (status))
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exit (WEXITSTATUS (status));
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else
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/* Abnormal termination cannot really be reproduced, so exit
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with 255. */
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exit (255);
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}
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}
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}
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#ifdef PROOT_PROGRAM
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@ -285,81 +362,23 @@ main (int argc, char *argv[])
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if (strcmp (store, "@STORE_DIRECTORY@") != 0
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&& lstat ("@WRAPPED_PROGRAM@", &statbuf) != 0)
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{
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/* Spawn @WRAPPED_PROGRAM@ in a separate namespace where STORE is
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bind-mounted in the right place. */
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int err;
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char *new_root = mkdtemp (strdup ("/tmp/guix-exec-XXXXXX"));
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char *new_store = concat (new_root, "@STORE_DIRECTORY@");
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char *cwd = get_current_dir_name ();
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/* Buffer stderr so that nothing's displayed if 'exec_in_user_namespace'
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fails but 'exec_with_proot' works. */
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static char stderr_buffer[4096];
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setvbuf (stderr, stderr_buffer, _IOFBF, sizeof stderr_buffer);
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/* Create a child with separate namespaces and set up bind-mounts from
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there. That way, bind-mounts automatically disappear when the child
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exits, which simplifies cleanup for the parent. Note: clone is more
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convenient than fork + unshare since the parent can directly write
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the child uid_map/gid_map files. */
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pid_t child = syscall (SYS_clone, SIGCHLD | CLONE_NEWNS | CLONE_NEWUSER,
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NULL, NULL, NULL);
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switch (child)
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{
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case 0:
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/* Note: Due to <https://bugzilla.kernel.org/show_bug.cgi?id=183461>
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we cannot make NEW_ROOT a tmpfs (which would have saved the need
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for 'rm_rf'.) */
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bind_mount ("/", new_root);
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mkdir_p (new_store);
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err = mount (store, new_store, "none", MS_BIND | MS_REC | MS_RDONLY,
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NULL);
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if (err < 0)
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assert_perror (errno);
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chdir (new_root);
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err = chroot (new_root);
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if (err < 0)
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assert_perror (errno);
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/* Change back to where we were before chroot'ing. */
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chdir (cwd);
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break;
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case -1:
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rm_rf (new_root);
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exec_in_user_namespace (store, argc, argv);
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#ifdef PROOT_PROGRAM
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exec_with_proot (store, argc, argv);
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exec_with_proot (store, argc, argv);
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#else
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fprintf (stderr, "%s: error: 'clone' failed: %m\n", argv[0]);
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fprintf (stderr, "\
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fprintf (stderr, "\
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This may be because \"user namespaces\" are not supported on this system.\n\
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Consequently, we cannot run '@WRAPPED_PROGRAM@',\n\
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unless you move it to the '@STORE_DIRECTORY@' directory.\n\
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\n\
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Please refer to the 'guix pack' documentation for more information.\n");
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#endif
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return EXIT_FAILURE;
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default:
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{
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/* Map the current user/group ID in the child's namespace (the
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default is to get the "overflow UID", i.e., the UID of
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"nobody"). We must first disallow 'setgroups' for that
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process. */
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disallow_setgroups (child);
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write_id_map (child, "uid_map", getuid ());
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write_id_map (child, "gid_map", getgid ());
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int status;
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waitpid (child, &status, 0);
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chdir ("/"); /* avoid EBUSY */
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rm_rf (new_root);
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free (new_root);
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if (WIFEXITED (status))
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exit (WEXITSTATUS (status));
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else
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/* Abnormal termination cannot really be reproduced, so exit
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with 255. */
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exit (255);
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}
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}
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return EXIT_FAILURE;
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}
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/* The executable is available under @STORE_DIRECTORY@, so we can now
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