fs_mgr_verity.cpp revision 183ca56ce22fa59d8b1a1372051b28984d1ab91c 
1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <ctype.h>
18#include <errno.h>
19#include <fcntl.h>
20#include <inttypes.h>
21#include <libgen.h>
22#include <stdio.h>
23#include <stdlib.h>
24#include <string.h>
25#include <sys/mount.h>
26#include <sys/stat.h>
27#include <sys/types.h>
28#include <sys/wait.h>
29#include <time.h>
30#include <unistd.h>
31
32#include <android-base/file.h>
33#include <android-base/strings.h>
34#include <android-base/unique_fd.h>
35#include <crypto_utils/android_pubkey.h>
36#include <cutils/properties.h>
37#include <logwrap/logwrap.h>
38#include <openssl/obj_mac.h>
39#include <openssl/rsa.h>
40#include <openssl/sha.h>
41#include <private/android_filesystem_config.h>
42
43#include "fec/io.h"
44
45#include "fs_mgr.h"
46#include "fs_mgr_priv.h"
47#include "fs_mgr_priv_dm_ioctl.h"
48#include "fs_mgr_priv_verity.h"
49
50#define FSTAB_PREFIX "/fstab."
51
52#define VERITY_TABLE_RSA_KEY "/verity_key"
53#define VERITY_TABLE_HASH_IDX 8
54#define VERITY_TABLE_SALT_IDX 9
55
56#define VERITY_TABLE_OPT_RESTART "restart_on_corruption"
57#define VERITY_TABLE_OPT_LOGGING "ignore_corruption"
58#define VERITY_TABLE_OPT_IGNZERO "ignore_zero_blocks"
59
60#define VERITY_TABLE_OPT_FEC_FORMAT \
61    "use_fec_from_device %s fec_start %" PRIu64 " fec_blocks %" PRIu64 \
62    " fec_roots %u " VERITY_TABLE_OPT_IGNZERO
63#define VERITY_TABLE_OPT_FEC_ARGS 9
64
65#define METADATA_MAGIC 0x01564c54
66#define METADATA_TAG_MAX_LENGTH 63
67#define METADATA_EOD "eod"
68
69#define VERITY_LASTSIG_TAG "verity_lastsig"
70
71#define VERITY_STATE_TAG "verity_state"
72#define VERITY_STATE_HEADER 0x83c0ae9d
73#define VERITY_STATE_VERSION 1
74
75#define VERITY_KMSG_RESTART "dm-verity device corrupted"
76#define VERITY_KMSG_BUFSIZE 1024
77
78#define READ_BUF_SIZE 4096
79
80#define __STRINGIFY(x) #x
81#define STRINGIFY(x) __STRINGIFY(x)
82
83struct verity_state {
84    uint32_t header;
85    uint32_t version;
86    int32_t mode;
87};
88
89extern struct fs_info info;
90
91static RSA *load_key(const char *path)
92{
93    uint8_t key_data[ANDROID_PUBKEY_ENCODED_SIZE];
94
95    FILE* f = fopen(path, "r");
96    if (!f) {
97        LERROR << "Can't open " << path;
98        return NULL;
99    }
100
101    if (!fread(key_data, sizeof(key_data), 1, f)) {
102        LERROR << "Could not read key!";
103        fclose(f);
104        return NULL;
105    }
106
107    fclose(f);
108
109    RSA* key = NULL;
110    if (!android_pubkey_decode(key_data, sizeof(key_data), &key)) {
111        LERROR << "Could not parse key!";
112        return NULL;
113    }
114
115    return key;
116}
117
118static int verify_table(const uint8_t *signature, size_t signature_size,
119        const char *table, uint32_t table_length)
120{
121    RSA *key;
122    uint8_t hash_buf[SHA256_DIGEST_LENGTH];
123    int retval = -1;
124
125    // Hash the table
126    SHA256((uint8_t*)table, table_length, hash_buf);
127
128    // Now get the public key from the keyfile
129    key = load_key(VERITY_TABLE_RSA_KEY);
130    if (!key) {
131        LERROR << "Couldn't load verity keys";
132        goto out;
133    }
134
135    // verify the result
136    if (!RSA_verify(NID_sha256, hash_buf, sizeof(hash_buf), signature,
137                    signature_size, key)) {
138        LERROR << "Couldn't verify table";
139        goto out;
140    }
141
142    retval = 0;
143
144out:
145    RSA_free(key);
146    return retval;
147}
148
149static int verify_verity_signature(const struct fec_verity_metadata& verity)
150{
151    if (verify_table(verity.signature, sizeof(verity.signature),
152            verity.table, verity.table_length) == 0 ||
153        verify_table(verity.ecc_signature, sizeof(verity.ecc_signature),
154            verity.table, verity.table_length) == 0) {
155        return 0;
156    }
157
158    return -1;
159}
160
161static int invalidate_table(char *table, size_t table_length)
162{
163    size_t n = 0;
164    size_t idx = 0;
165    size_t cleared = 0;
166
167    while (n < table_length) {
168        if (table[n++] == ' ') {
169            ++idx;
170        }
171
172        if (idx != VERITY_TABLE_HASH_IDX && idx != VERITY_TABLE_SALT_IDX) {
173            continue;
174        }
175
176        while (n < table_length && table[n] != ' ') {
177            table[n++] = '0';
178        }
179
180        if (++cleared == 2) {
181            return 0;
182        }
183    }
184
185    return -1;
186}
187
188struct verity_table_params {
189    char *table;
190    int mode;
191    struct fec_ecc_metadata ecc;
192    const char *ecc_dev;
193};
194
195typedef bool (*format_verity_table_func)(char *buf, const size_t bufsize,
196        const struct verity_table_params *params);
197
198static bool format_verity_table(char *buf, const size_t bufsize,
199        const struct verity_table_params *params)
200{
201    const char *mode_flag = NULL;
202    int res = -1;
203
204    if (params->mode == VERITY_MODE_RESTART) {
205        mode_flag = VERITY_TABLE_OPT_RESTART;
206    } else if (params->mode == VERITY_MODE_LOGGING) {
207        mode_flag = VERITY_TABLE_OPT_LOGGING;
208    }
209
210    if (params->ecc.valid) {
211        if (mode_flag) {
212            res = snprintf(buf, bufsize,
213                    "%s %u %s " VERITY_TABLE_OPT_FEC_FORMAT,
214                    params->table, 1 + VERITY_TABLE_OPT_FEC_ARGS, mode_flag, params->ecc_dev,
215                    params->ecc.start / FEC_BLOCKSIZE, params->ecc.blocks, params->ecc.roots);
216        } else {
217            res = snprintf(buf, bufsize,
218                    "%s %u " VERITY_TABLE_OPT_FEC_FORMAT,
219                    params->table, VERITY_TABLE_OPT_FEC_ARGS, params->ecc_dev,
220                    params->ecc.start / FEC_BLOCKSIZE, params->ecc.blocks, params->ecc.roots);
221        }
222    } else if (mode_flag) {
223        res = snprintf(buf, bufsize, "%s 2 " VERITY_TABLE_OPT_IGNZERO " %s", params->table,
224                    mode_flag);
225    } else {
226        res = snprintf(buf, bufsize, "%s 1 " VERITY_TABLE_OPT_IGNZERO, params->table);
227    }
228
229    if (res < 0 || (size_t)res >= bufsize) {
230        LERROR << "Error building verity table; insufficient buffer size?";
231        return false;
232    }
233
234    return true;
235}
236
237static bool format_legacy_verity_table(char *buf, const size_t bufsize,
238        const struct verity_table_params *params)
239{
240    int res;
241
242    if (params->mode == VERITY_MODE_EIO) {
243        res = strlcpy(buf, params->table, bufsize);
244    } else {
245        res = snprintf(buf, bufsize, "%s %d", params->table, params->mode);
246    }
247
248    if (res < 0 || (size_t)res >= bufsize) {
249        LERROR << "Error building verity table; insufficient buffer size?";
250        return false;
251    }
252
253    return true;
254}
255
256static int load_verity_table(struct dm_ioctl *io, const std::string &name,
257                             uint64_t device_size, int fd,
258        const struct verity_table_params *params, format_verity_table_func format)
259{
260    char *verity_params;
261    char *buffer = (char*) io;
262    size_t bufsize;
263
264    fs_mgr_verity_ioctl_init(io, name, DM_STATUS_TABLE_FLAG);
265
266    struct dm_target_spec *tgt = (struct dm_target_spec *) &buffer[sizeof(struct dm_ioctl)];
267
268    // set tgt arguments
269    io->target_count = 1;
270    tgt->status = 0;
271    tgt->sector_start = 0;
272    tgt->length = device_size / 512;
273    strcpy(tgt->target_type, "verity");
274
275    // build the verity params
276    verity_params = buffer + sizeof(struct dm_ioctl) + sizeof(struct dm_target_spec);
277    bufsize = DM_BUF_SIZE - (verity_params - buffer);
278
279    if (!format(verity_params, bufsize, params)) {
280        LERROR << "Failed to format verity parameters";
281        return -1;
282    }
283
284    LINFO << "loading verity table: '" << verity_params << "'";
285
286    // set next target boundary
287    verity_params += strlen(verity_params) + 1;
288    verity_params = (char*)(((uintptr_t)verity_params + 7) & ~7);
289    tgt->next = verity_params - buffer;
290
291    // send the ioctl to load the verity table
292    if (ioctl(fd, DM_TABLE_LOAD, io)) {
293        PERROR << "Error loading verity table";
294        return -1;
295    }
296
297    return 0;
298}
299
300static int check_verity_restart(const char *fname)
301{
302    char buffer[VERITY_KMSG_BUFSIZE + 1];
303    int fd;
304    int rc = 0;
305    ssize_t size;
306    struct stat s;
307
308    fd = TEMP_FAILURE_RETRY(open(fname, O_RDONLY | O_CLOEXEC));
309
310    if (fd == -1) {
311        if (errno != ENOENT) {
312            PERROR << "Failed to open " << fname;
313        }
314        goto out;
315    }
316
317    if (fstat(fd, &s) == -1) {
318        PERROR << "Failed to fstat " << fname;
319        goto out;
320    }
321
322    size = VERITY_KMSG_BUFSIZE;
323
324    if (size > s.st_size) {
325        size = s.st_size;
326    }
327
328    if (lseek(fd, s.st_size - size, SEEK_SET) == -1) {
329        PERROR << "Failed to lseek " << (intmax_t)(s.st_size - size) << " " << fname;
330        goto out;
331    }
332
333    if (!android::base::ReadFully(fd, buffer, size)) {
334        PERROR << "Failed to read " << size << " bytes from " << fname;
335        goto out;
336    }
337
338    buffer[size] = '\0';
339
340    if (strstr(buffer, VERITY_KMSG_RESTART) != NULL) {
341        rc = 1;
342    }
343
344out:
345    if (fd != -1) {
346        close(fd);
347    }
348
349    return rc;
350}
351
352static int was_verity_restart()
353{
354    static const char *files[] = {
355        "/sys/fs/pstore/console-ramoops",
356        "/proc/last_kmsg",
357        NULL
358    };
359    int i;
360
361    for (i = 0; files[i]; ++i) {
362        if (check_verity_restart(files[i])) {
363            return 1;
364        }
365    }
366
367    return 0;
368}
369
370static int metadata_add(FILE *fp, long start, const char *tag,
371        unsigned int length, off64_t *offset)
372{
373    if (fseek(fp, start, SEEK_SET) < 0 ||
374        fprintf(fp, "%s %u\n", tag, length) < 0) {
375        return -1;
376    }
377
378    *offset = ftell(fp);
379
380    if (fseek(fp, length, SEEK_CUR) < 0 ||
381        fprintf(fp, METADATA_EOD " 0\n") < 0) {
382        return -1;
383    }
384
385    return 0;
386}
387
388static int metadata_find(const char *fname, const char *stag,
389        unsigned int slength, off64_t *offset)
390{
391    FILE *fp = NULL;
392    char tag[METADATA_TAG_MAX_LENGTH + 1];
393    int rc = -1;
394    int n;
395    long start = 0x4000; /* skip cryptfs metadata area */
396    uint32_t magic;
397    unsigned int length = 0;
398
399    if (!fname) {
400        return -1;
401    }
402
403    fp = fopen(fname, "r+");
404
405    if (!fp) {
406        PERROR << "Failed to open " << fname;
407        goto out;
408    }
409
410    /* check magic */
411    if (fseek(fp, start, SEEK_SET) < 0 ||
412        fread(&magic, sizeof(magic), 1, fp) != 1) {
413        PERROR << "Failed to read magic from " << fname;
414        goto out;
415    }
416
417    if (magic != METADATA_MAGIC) {
418        magic = METADATA_MAGIC;
419
420        if (fseek(fp, start, SEEK_SET) < 0 ||
421            fwrite(&magic, sizeof(magic), 1, fp) != 1) {
422            PERROR << "Failed to write magic to " << fname;
423            goto out;
424        }
425
426        rc = metadata_add(fp, start + sizeof(magic), stag, slength, offset);
427        if (rc < 0) {
428            PERROR << "Failed to add metadata to " << fname;
429        }
430
431        goto out;
432    }
433
434    start += sizeof(magic);
435
436    while (1) {
437        n = fscanf(fp, "%" STRINGIFY(METADATA_TAG_MAX_LENGTH) "s %u\n",
438                tag, &length);
439
440        if (n == 2 && strcmp(tag, METADATA_EOD)) {
441            /* found a tag */
442            start = ftell(fp);
443
444            if (!strcmp(tag, stag) && length == slength) {
445                *offset = start;
446                rc = 0;
447                goto out;
448            }
449
450            start += length;
451
452            if (fseek(fp, length, SEEK_CUR) < 0) {
453                PERROR << "Failed to seek " << fname;
454                goto out;
455            }
456        } else {
457            rc = metadata_add(fp, start, stag, slength, offset);
458            if (rc < 0) {
459                PERROR << "Failed to write metadata to " << fname;
460            }
461            goto out;
462        }
463   }
464
465out:
466    if (fp) {
467        fflush(fp);
468        fclose(fp);
469    }
470
471    return rc;
472}
473
474static int write_verity_state(const char *fname, off64_t offset, int32_t mode)
475{
476    int fd;
477    int rc = -1;
478    struct verity_state s = { VERITY_STATE_HEADER, VERITY_STATE_VERSION, mode };
479
480    fd = TEMP_FAILURE_RETRY(open(fname, O_WRONLY | O_SYNC | O_CLOEXEC));
481
482    if (fd == -1) {
483        PERROR << "Failed to open " << fname;
484        goto out;
485    }
486
487    if (TEMP_FAILURE_RETRY(pwrite64(fd, &s, sizeof(s), offset)) != sizeof(s)) {
488        PERROR << "Failed to write " << sizeof(s) << " bytes to " << fname
489               << " to offset " << offset;
490        goto out;
491    }
492
493    rc = 0;
494
495out:
496    if (fd != -1) {
497        close(fd);
498    }
499
500    return rc;
501}
502
503static int read_verity_state(const char *fname, off64_t offset, int *mode)
504{
505    int fd = -1;
506    int rc = -1;
507    struct verity_state s;
508
509    fd = TEMP_FAILURE_RETRY(open(fname, O_RDONLY | O_CLOEXEC));
510
511    if (fd == -1) {
512        PERROR << "Failed to open " << fname;
513        goto out;
514    }
515
516    if (TEMP_FAILURE_RETRY(pread64(fd, &s, sizeof(s), offset)) != sizeof(s)) {
517        PERROR << "Failed to read " <<  sizeof(s) << " bytes from " << fname
518               << " offset " << offset;
519        goto out;
520    }
521
522    if (s.header != VERITY_STATE_HEADER) {
523        /* space allocated, but no state written. write default state */
524        *mode = VERITY_MODE_DEFAULT;
525        rc = write_verity_state(fname, offset, *mode);
526        goto out;
527    }
528
529    if (s.version != VERITY_STATE_VERSION) {
530        LERROR << "Unsupported verity state version (" << s.version << ")";
531        goto out;
532    }
533
534    if (s.mode < VERITY_MODE_EIO ||
535        s.mode > VERITY_MODE_LAST) {
536        LERROR << "Unsupported verity mode (" << s.mode << ")";
537        goto out;
538    }
539
540    *mode = s.mode;
541    rc = 0;
542
543out:
544    if (fd != -1) {
545        close(fd);
546    }
547
548    return rc;
549}
550
551static int read_partition(const char *path, uint64_t size)
552{
553    char buf[READ_BUF_SIZE];
554    ssize_t size_read;
555    android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(path, O_RDONLY | O_CLOEXEC)));
556
557    if (fd == -1) {
558        PERROR << "Failed to open " << path;
559        return -errno;
560    }
561
562    while (size) {
563        size_read = TEMP_FAILURE_RETRY(read(fd, buf, READ_BUF_SIZE));
564        if (size_read == -1) {
565            PERROR << "Error in reading partition " << path;
566            return -errno;
567        }
568        size -= size_read;
569    }
570
571    return 0;
572}
573
574static int compare_last_signature(struct fstab_rec *fstab, int *match)
575{
576    char tag[METADATA_TAG_MAX_LENGTH + 1];
577    int fd = -1;
578    int rc = -1;
579    off64_t offset = 0;
580    struct fec_handle *f = NULL;
581    struct fec_verity_metadata verity;
582    uint8_t curr[SHA256_DIGEST_LENGTH];
583    uint8_t prev[SHA256_DIGEST_LENGTH];
584
585    *match = 1;
586
587    if (fec_open(&f, fstab->blk_device, O_RDONLY, FEC_VERITY_DISABLE,
588            FEC_DEFAULT_ROOTS) == -1) {
589        PERROR << "Failed to open '" << fstab->blk_device << "'";
590        return rc;
591    }
592
593    // read verity metadata
594    if (fec_verity_get_metadata(f, &verity) == -1) {
595        PERROR << "Failed to get verity metadata '" << fstab->blk_device << "'";
596        goto out;
597    }
598
599    SHA256(verity.signature, sizeof(verity.signature), curr);
600
601    if (snprintf(tag, sizeof(tag), VERITY_LASTSIG_TAG "_%s",
602            basename(fstab->mount_point)) >= (int)sizeof(tag)) {
603        LERROR << "Metadata tag name too long for " << fstab->mount_point;
604        goto out;
605    }
606
607    if (metadata_find(fstab->verity_loc, tag, SHA256_DIGEST_LENGTH,
608            &offset) < 0) {
609        goto out;
610    }
611
612    fd = TEMP_FAILURE_RETRY(open(fstab->verity_loc, O_RDWR | O_SYNC | O_CLOEXEC));
613
614    if (fd == -1) {
615        PERROR << "Failed to open " << fstab->verity_loc;
616        goto out;
617    }
618
619    if (TEMP_FAILURE_RETRY(pread64(fd, prev, sizeof(prev),
620            offset)) != sizeof(prev)) {
621        PERROR << "Failed to read " << sizeof(prev) << " bytes from "
622               << fstab->verity_loc << " offset " << offset;
623        goto out;
624    }
625
626    *match = !memcmp(curr, prev, SHA256_DIGEST_LENGTH);
627
628    if (!*match) {
629        /* update current signature hash */
630        if (TEMP_FAILURE_RETRY(pwrite64(fd, curr, sizeof(curr),
631                offset)) != sizeof(curr)) {
632            PERROR << "Failed to write " << sizeof(curr) << " bytes to "
633                   << fstab->verity_loc << " offset " << offset;
634            goto out;
635        }
636    }
637
638    rc = 0;
639
640out:
641    fec_close(f);
642    return rc;
643}
644
645static int get_verity_state_offset(struct fstab_rec *fstab, off64_t *offset)
646{
647    char tag[METADATA_TAG_MAX_LENGTH + 1];
648
649    if (snprintf(tag, sizeof(tag), VERITY_STATE_TAG "_%s",
650            basename(fstab->mount_point)) >= (int)sizeof(tag)) {
651        LERROR << "Metadata tag name too long for " << fstab->mount_point;
652        return -1;
653    }
654
655    return metadata_find(fstab->verity_loc, tag, sizeof(struct verity_state),
656                offset);
657}
658
659static int load_verity_state(struct fstab_rec *fstab, int *mode)
660{
661    char propbuf[PROPERTY_VALUE_MAX];
662    int match = 0;
663    off64_t offset = 0;
664
665    /* unless otherwise specified, use EIO mode */
666    *mode = VERITY_MODE_EIO;
667
668    /* use the kernel parameter if set */
669    property_get("ro.boot.veritymode", propbuf, "");
670
671    if (*propbuf != '\0') {
672        if (!strcmp(propbuf, "enforcing")) {
673            *mode = VERITY_MODE_DEFAULT;
674        }
675        return 0;
676    }
677
678    if (get_verity_state_offset(fstab, &offset) < 0) {
679        /* fall back to stateless behavior */
680        return 0;
681    }
682
683    if (was_verity_restart()) {
684        /* device was restarted after dm-verity detected a corrupted
685         * block, so use EIO mode */
686        return write_verity_state(fstab->verity_loc, offset, *mode);
687    }
688
689    if (!compare_last_signature(fstab, &match) && !match) {
690        /* partition has been reflashed, reset dm-verity state */
691        *mode = VERITY_MODE_DEFAULT;
692        return write_verity_state(fstab->verity_loc, offset, *mode);
693    }
694
695    return read_verity_state(fstab->verity_loc, offset, mode);
696}
697
698int fs_mgr_load_verity_state(int *mode)
699{
700    char fstab_filename[PROPERTY_VALUE_MAX + sizeof(FSTAB_PREFIX)];
701    char propbuf[PROPERTY_VALUE_MAX];
702    int rc = -1;
703    int i;
704    int current;
705    struct fstab *fstab = NULL;
706
707    /* return the default mode, unless any of the verified partitions are in
708     * logging mode, in which case return that */
709    *mode = VERITY_MODE_DEFAULT;
710
711    property_get("ro.hardware", propbuf, "");
712    snprintf(fstab_filename, sizeof(fstab_filename), FSTAB_PREFIX"%s", propbuf);
713
714    fstab = fs_mgr_read_fstab(fstab_filename);
715
716    if (!fstab) {
717        LERROR << "Failed to read " << fstab_filename;
718        goto out;
719    }
720
721    for (i = 0; i < fstab->num_entries; i++) {
722        if (!fs_mgr_is_verified(&fstab->recs[i])) {
723            continue;
724        }
725
726        rc = load_verity_state(&fstab->recs[i], &current);
727        if (rc < 0) {
728            continue;
729        }
730
731        if (current != VERITY_MODE_DEFAULT) {
732            *mode = current;
733            break;
734        }
735    }
736
737    rc = 0;
738
739out:
740    if (fstab) {
741        fs_mgr_free_fstab(fstab);
742    }
743
744    return rc;
745}
746
747int fs_mgr_update_verity_state(fs_mgr_verity_state_callback callback)
748{
749    alignas(dm_ioctl) char buffer[DM_BUF_SIZE];
750    bool system_root = false;
751    char fstab_filename[PROPERTY_VALUE_MAX + sizeof(FSTAB_PREFIX)];
752    std::string mount_point;
753    char propbuf[PROPERTY_VALUE_MAX];
754    const char *status;
755    int fd = -1;
756    int i;
757    int mode;
758    int rc = -1;
759    struct dm_ioctl *io = (struct dm_ioctl *) buffer;
760    struct fstab *fstab = NULL;
761
762    if (!callback) {
763        return -1;
764    }
765
766    if (fs_mgr_load_verity_state(&mode) == -1) {
767        return -1;
768    }
769
770    fd = TEMP_FAILURE_RETRY(open("/dev/device-mapper", O_RDWR | O_CLOEXEC));
771
772    if (fd == -1) {
773        PERROR << "Error opening device mapper";
774        goto out;
775    }
776
777    property_get("ro.hardware", propbuf, "");
778    snprintf(fstab_filename, sizeof(fstab_filename), FSTAB_PREFIX"%s", propbuf);
779
780    property_get("ro.build.system_root_image", propbuf, "");
781    system_root = !strcmp(propbuf, "true");
782
783    fstab = fs_mgr_read_fstab(fstab_filename);
784
785    if (!fstab) {
786        LERROR << "Failed to read " << fstab_filename;
787        goto out;
788    }
789
790    for (i = 0; i < fstab->num_entries; i++) {
791        if (!fs_mgr_is_verified(&fstab->recs[i])) {
792            continue;
793        }
794
795        if (system_root && !strcmp(fstab->recs[i].mount_point, "/")) {
796            mount_point = "system";
797        } else {
798            mount_point = basename(fstab->recs[i].mount_point);
799        }
800
801        fs_mgr_verity_ioctl_init(io, mount_point, 0);
802
803        if (ioctl(fd, DM_TABLE_STATUS, io)) {
804            if (fstab->recs[i].fs_mgr_flags & MF_VERIFYATBOOT) {
805                status = "V";
806            } else {
807                PERROR << "Failed to query DM_TABLE_STATUS for "
808                       << mount_point.c_str();
809                continue;
810            }
811        }
812
813        status = &buffer[io->data_start + sizeof(struct dm_target_spec)];
814
815        if (*status == 'C' || *status == 'V') {
816            callback(&fstab->recs[i], mount_point.c_str(), mode, *status);
817        }
818    }
819
820    rc = 0;
821
822out:
823    if (fstab) {
824        fs_mgr_free_fstab(fstab);
825    }
826
827    if (fd) {
828        close(fd);
829    }
830
831    return rc;
832}
833
834static void update_verity_table_blk_device(char *blk_device, char **table)
835{
836    std::string result, word;
837    auto tokens = android::base::Split(*table, " ");
838
839    for (const auto& token : tokens) {
840        if (android::base::StartsWith(token, "/dev/block/") &&
841            android::base::StartsWith(blk_device, token.c_str())) {
842            word = blk_device;
843        } else {
844            word = token;
845        }
846
847        if (result.empty()) {
848            result = word;
849        } else {
850            result += " " + word;
851        }
852    }
853
854    if (result.empty()) {
855        return;
856    }
857
858    free(*table);
859    *table = strdup(result.c_str());
860}
861
862int fs_mgr_setup_verity(struct fstab_rec *fstab, bool verify_dev)
863{
864    int retval = FS_MGR_SETUP_VERITY_FAIL;
865    int fd = -1;
866    std::string verity_blk_name;
867    struct fec_handle *f = NULL;
868    struct fec_verity_metadata verity;
869    struct verity_table_params params = { .table = NULL };
870
871    alignas(dm_ioctl) char buffer[DM_BUF_SIZE];
872    struct dm_ioctl *io = (struct dm_ioctl *) buffer;
873    const std::string mount_point(basename(fstab->mount_point));
874    bool verified_at_boot = false;
875
876    if (fec_open(&f, fstab->blk_device, O_RDONLY, FEC_VERITY_DISABLE,
877            FEC_DEFAULT_ROOTS) < 0) {
878        PERROR << "Failed to open '" << fstab->blk_device << "'";
879        return retval;
880    }
881
882    // read verity metadata
883    if (fec_verity_get_metadata(f, &verity) < 0) {
884        PERROR << "Failed to get verity metadata '" << fstab->blk_device << "'";
885        goto out;
886    }
887
888#ifdef ALLOW_ADBD_DISABLE_VERITY
889    if (verity.disabled) {
890        retval = FS_MGR_SETUP_VERITY_DISABLED;
891        LINFO << "Attempt to cleanly disable verity - only works in USERDEBUG";
892        goto out;
893    }
894#endif
895
896    // read ecc metadata
897    if (fec_ecc_get_metadata(f, &params.ecc) < 0) {
898        params.ecc.valid = false;
899    }
900
901    params.ecc_dev = fstab->blk_device;
902
903    // get the device mapper fd
904    if ((fd = open("/dev/device-mapper", O_RDWR)) < 0) {
905        PERROR << "Error opening device mapper";
906        goto out;
907    }
908
909    // create the device
910    if (!fs_mgr_create_verity_device(io, mount_point, fd)) {
911        LERROR << "Couldn't create verity device!";
912        goto out;
913    }
914
915    // get the name of the device file
916    if (!fs_mgr_get_verity_device_name(io, mount_point, fd, &verity_blk_name)) {
917        LERROR << "Couldn't get verity device number!";
918        goto out;
919    }
920
921    if (load_verity_state(fstab, &params.mode) < 0) {
922        /* if accessing or updating the state failed, switch to the default
923         * safe mode. This makes sure the device won't end up in an endless
924         * restart loop, and no corrupted data will be exposed to userspace
925         * without a warning. */
926        params.mode = VERITY_MODE_EIO;
927    }
928
929    if (!verity.table) {
930        goto out;
931    }
932
933    params.table = strdup(verity.table);
934    if (!params.table) {
935        goto out;
936    }
937
938    // verify the signature on the table
939    if (verify_verity_signature(verity) < 0) {
940        if (params.mode == VERITY_MODE_LOGGING) {
941            // the user has been warned, allow mounting without dm-verity
942            retval = FS_MGR_SETUP_VERITY_SUCCESS;
943            goto out;
944        }
945
946        // invalidate root hash and salt to trigger device-specific recovery
947        if (invalidate_table(params.table, verity.table_length) < 0) {
948            goto out;
949        }
950    }
951
952    LINFO << "Enabling dm-verity for " << mount_point.c_str()
953          << " (mode " << params.mode << ")";
954
955    if (fstab->fs_mgr_flags & MF_SLOTSELECT) {
956        // Update the verity params using the actual block device path
957        update_verity_table_blk_device(fstab->blk_device, &params.table);
958    }
959
960    // load the verity mapping table
961    if (load_verity_table(io, mount_point, verity.data_size, fd, &params,
962            format_verity_table) == 0) {
963        goto loaded;
964    }
965
966    if (params.ecc.valid) {
967        // kernel may not support error correction, try without
968        LINFO << "Disabling error correction for " << mount_point.c_str();
969        params.ecc.valid = false;
970
971        if (load_verity_table(io, mount_point, verity.data_size, fd, &params,
972                format_verity_table) == 0) {
973            goto loaded;
974        }
975    }
976
977    // try the legacy format for backwards compatibility
978    if (load_verity_table(io, mount_point, verity.data_size, fd, &params,
979            format_legacy_verity_table) == 0) {
980        goto loaded;
981    }
982
983    if (params.mode != VERITY_MODE_EIO) {
984        // as a last resort, EIO mode should always be supported
985        LINFO << "Falling back to EIO mode for " << mount_point.c_str();
986        params.mode = VERITY_MODE_EIO;
987
988        if (load_verity_table(io, mount_point, verity.data_size, fd, &params,
989                format_legacy_verity_table) == 0) {
990            goto loaded;
991        }
992    }
993
994    LERROR << "Failed to load verity table for " << mount_point.c_str();
995    goto out;
996
997loaded:
998
999    // activate the device
1000    if (!fs_mgr_resume_verity_table(io, mount_point, fd)) {
1001        goto out;
1002    }
1003
1004    // mark the underlying block device as read-only
1005    fs_mgr_set_blk_ro(fstab->blk_device);
1006
1007    // Verify the entire partition in one go
1008    // If there is an error, allow it to mount as a normal verity partition.
1009    if (fstab->fs_mgr_flags & MF_VERIFYATBOOT) {
1010        LINFO << "Verifying partition " << fstab->blk_device << " at boot";
1011        int err = read_partition(verity_blk_name.c_str(), verity.data_size);
1012        if (!err) {
1013            LINFO << "Verified verity partition "
1014                  << fstab->blk_device << " at boot";
1015            verified_at_boot = true;
1016        }
1017    }
1018
1019    // assign the new verity block device as the block device
1020    if (!verified_at_boot) {
1021        free(fstab->blk_device);
1022        fstab->blk_device = strdup(verity_blk_name.c_str());
1023    } else if (!fs_mgr_destroy_verity_device(io, mount_point, fd)) {
1024        LERROR << "Failed to remove verity device " << mount_point.c_str();
1025        goto out;
1026    }
1027
1028    // make sure we've set everything up properly
1029    if (verify_dev && fs_mgr_test_access(fstab->blk_device) < 0) {
1030        goto out;
1031    }
1032
1033    retval = FS_MGR_SETUP_VERITY_SUCCESS;
1034
1035out:
1036    if (fd != -1) {
1037        close(fd);
1038    }
1039
1040    fec_close(f);
1041    free(params.table);
1042
1043    return retval;
1044}
1045