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Systemd/src/dissect/dissect.c
Lennart Poettering 2d3a5a73e0 nspawn: make sure images containing an ESP are compatible with userns -U mode 
In -U mode we might need to re-chown() all files and directories to
match the UID shift we want for the image. That's problematic on fat
partitions, such as the ESP (and which is generated by mkosi's
--bootable switch), because fat of course knows no UID/GID file
ownership natively.

With this change we take benefit of the uid= and gid= mount options FAT
knows: instead of chown()ing all files and directories we can just
specify the right UID/GID to use at mount time.

This beefs up the image dissection logic in two ways:

1. First of all support for mounting relevant file systems with
   uid=/gid= is added: when a UID is specified during mount it is used for
   all applicable file systems.

2. Secondly, two new mount flags are added:
   DISSECT_IMAGE_MOUNT_ROOT_ONLY and DISSECT_IMAGE_MOUNT_NON_ROOT_ONLY.
   If one is specified the mount routine will either only mount the root
   partition of an image, or all partitions except the root partition.
   This is used by nspawn: first the root partition is mounted, so that
   we can determine the UID shift in use so far, based on ownership of
   the image's root directory. Then, we mount the remaining partitions
   in a second go, this time with the right UID/GID information.
2017-12-05 13:49:12 +01:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
/***
This file is part of systemd.
Copyright 2016 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <fcntl.h>
#include <stdio.h>
#include <getopt.h>
#include "architecture.h"
#include "dissect-image.h"
#include "hexdecoct.h"
#include "log.h"
#include "loop-util.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
#include "util.h"
static enum {
ACTION_DISSECT,
ACTION_MOUNT,
} arg_action = ACTION_DISSECT;
static const char *arg_image = NULL;
static const char *arg_path = NULL;
static DissectImageFlags arg_flags = DISSECT_IMAGE_REQUIRE_ROOT|DISSECT_IMAGE_DISCARD_ON_LOOP;
static void *arg_root_hash = NULL;
static size_t arg_root_hash_size = 0;
static void help(void) {
printf("%s [OPTIONS...] IMAGE\n"
"%s [OPTIONS...] --mount IMAGE PATH\n"
"Dissect a file system OS image.\n\n"
" -h --help Show this help\n"
" --version Show package version\n"
" -m --mount Mount the image to the specified directory\n"
" -r --read-only Mount read-only\n"
" --discard=MODE Choose 'discard' mode (disabled, loop, all, crypto)\n"
" --root-hash=HASH Specify root hash for verity\n",
program_invocation_short_name,
program_invocation_short_name);
}
static int parse_argv(int argc, char *argv[]) {
enum {
ARG_VERSION = 0x100,
ARG_DISCARD,
ARG_ROOT_HASH,
};
static const struct option options[] = {
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, ARG_VERSION },
{ "mount", no_argument, NULL, 'm' },
{ "read-only", no_argument, NULL, 'r' },
{ "discard", required_argument, NULL, ARG_DISCARD },
{ "root-hash", required_argument, NULL, ARG_ROOT_HASH },
{}
};
int c, r;
assert(argc >= 0);
assert(argv);
while ((c = getopt_long(argc, argv, "hmr", options, NULL)) >= 0) {
switch (c) {
case 'h':
help();
return 0;
case ARG_VERSION:
return version();
case 'm':
arg_action = ACTION_MOUNT;
break;
case 'r':
arg_flags |= DISSECT_IMAGE_READ_ONLY;
break;
case ARG_DISCARD: {
DissectImageFlags flags;
if (streq(optarg, "disabled"))
flags = 0;
else if (streq(optarg, "loop"))
flags = DISSECT_IMAGE_DISCARD_ON_LOOP;
else if (streq(optarg, "all"))
flags = DISSECT_IMAGE_DISCARD_ON_LOOP | DISSECT_IMAGE_DISCARD;
else if (streq(optarg, "crypt"))
flags = DISSECT_IMAGE_DISCARD_ANY;
else {
log_error("Unknown --discard= parameter: %s", optarg);
return -EINVAL;
}
arg_flags = (arg_flags & ~DISSECT_IMAGE_DISCARD_ANY) | flags;
break;
}
case ARG_ROOT_HASH: {
void *p;
size_t l;
r = unhexmem(optarg, strlen(optarg), &p, &l);
if (r < 0)
return log_error_errno(r, "Failed to parse root hash: %s", optarg);
if (l < sizeof(sd_id128_t)) {
log_error("Root hash must be at least 128bit long: %s", optarg);
free(p);
return -EINVAL;
}
free(arg_root_hash);
arg_root_hash = p;
arg_root_hash_size = l;
break;
}
case '?':
return -EINVAL;
default:
assert_not_reached("Unhandled option");
}
}
switch (arg_action) {
case ACTION_DISSECT:
if (optind + 1 != argc) {
log_error("Expected a file path as only argument.");
return -EINVAL;
}
arg_image = argv[optind];
arg_flags |= DISSECT_IMAGE_READ_ONLY;
break;
case ACTION_MOUNT:
if (optind + 2 != argc) {
log_error("Expected a file path and mount point path as only arguments.");
return -EINVAL;
}
arg_image = argv[optind];
arg_path = argv[optind + 1];
break;
default:
assert_not_reached("Unknown action.");
}
return 1;
}
int main(int argc, char *argv[]) {
_cleanup_(loop_device_unrefp) LoopDevice *d = NULL;
_cleanup_(decrypted_image_unrefp) DecryptedImage *di = NULL;
_cleanup_(dissected_image_unrefp) DissectedImage *m = NULL;
int r;
log_parse_environment();
log_open();
r = parse_argv(argc, argv);
if (r <= 0)
goto finish;
r = loop_device_make_by_path(arg_image, (arg_flags & DISSECT_IMAGE_READ_ONLY) ? O_RDONLY : O_RDWR, &d);
if (r < 0) {
log_error_errno(r, "Failed to set up loopback device: %m");
goto finish;
}
if (!arg_root_hash) {
r = root_hash_load(arg_image, &arg_root_hash, &arg_root_hash_size);
if (r < 0) {
log_error_errno(r, "Failed to read root hash file for %s: %m", arg_image);
goto finish;
}
}
r = dissect_image(d->fd, arg_root_hash, arg_root_hash_size, arg_flags, &m);
if (r == -ENOPKG) {
log_error_errno(r, "Couldn't identify a suitable partition table or file system in %s.", arg_image);
goto finish;
}
if (r == -EADDRNOTAVAIL) {
log_error_errno(r, "No root partition for specified root hash found in %s.", arg_image);
goto finish;
}
if (r == -ENOTUNIQ) {
log_error_errno(r, "Multiple suitable root partitions found in image %s.", arg_image);
goto finish;
}
if (r == -ENXIO) {
log_error_errno(r, "No suitable root partition found in image %s.", arg_image);
goto finish;
}
if (r == -EPROTONOSUPPORT) {
log_error_errno(r, "Device %s is loopback block device with partition scanning turned off, please turn it on.", arg_image);
goto finish;
}
if (r < 0) {
log_error_errno(r, "Failed to dissect image: %m");
goto finish;
}
switch (arg_action) {
case ACTION_DISSECT: {
unsigned i;
for (i = 0; i < _PARTITION_DESIGNATOR_MAX; i++) {
DissectedPartition *p = m->partitions + i;
int k;
if (!p->found)
continue;
printf("Found %s '%s' partition",
p->rw ? "writable" : "read-only",
partition_designator_to_string(i));
if (!sd_id128_is_null(p->uuid))
printf(" (UUID " SD_ID128_FORMAT_STR ")", SD_ID128_FORMAT_VAL(p->uuid));
if (p->fstype)
printf(" of type %s", p->fstype);
if (p->architecture != _ARCHITECTURE_INVALID)
printf(" for %s", architecture_to_string(p->architecture));
k = PARTITION_VERITY_OF(i);
if (k >= 0)
printf(" %s verity", m->partitions[k].found ? "with" : "without");
if (p->partno >= 0)
printf(" on partition #%i", p->partno);
if (p->node)
printf(" (%s)", p->node);
putchar('\n');
}
r = dissected_image_acquire_metadata(m);
if (r < 0) {
log_error_errno(r, "Failed to acquire image metadata: %m");
goto finish;
}
if (m->hostname)
printf(" Hostname: %s\n", m->hostname);
if (!sd_id128_is_null(m->machine_id))
printf("Machine ID: " SD_ID128_FORMAT_STR "\n", SD_ID128_FORMAT_VAL(m->machine_id));
if (!strv_isempty(m->machine_info)) {
char **p, **q;
STRV_FOREACH_PAIR(p, q, m->machine_info)
printf("%s %s=%s\n",
p == m->machine_info ? "Mach. Info:" : " ",
*p, *q);
}
if (!strv_isempty(m->os_release)) {
char **p, **q;
STRV_FOREACH_PAIR(p, q, m->os_release)
printf("%s %s=%s\n",
p == m->os_release ? "OS Release:" : " ",
*p, *q);
}
break;
}
case ACTION_MOUNT:
r = dissected_image_decrypt_interactively(m, NULL, arg_root_hash, arg_root_hash_size, arg_flags, &di);
if (r < 0)
goto finish;
r = dissected_image_mount(m, arg_path, UID_INVALID, arg_flags);
if (r < 0) {
log_error_errno(r, "Failed to mount image: %m");
goto finish;
}
if (di) {
r = decrypted_image_relinquish(di);
if (r < 0) {
log_error_errno(r, "Failed to relinquish DM devices: %m");
goto finish;
}
}
loop_device_relinquish(d);
break;
default:
assert_not_reached("Unknown action.");
}
finish:
free(arg_root_hash);
return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}
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