fs_mgr/fs_mgr_verity.c - android-core - Git at Google

 /*
  * Copyright (C) 2013 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <ctype.h>
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <errno.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <libgen.h>
 #include <time.h>

 #include <private/android_filesystem_config.h>
 #include <cutils/properties.h>
 #include <logwrap/logwrap.h>

 #include "mincrypt/rsa.h"
 #include "mincrypt/sha.h"
 #include "mincrypt/sha256.h"

 #include "ext4_sb.h"

 #include "fs_mgr_priv.h"
 #include "fs_mgr_priv_verity.h"

 #define FSTAB_PREFIX "/fstab."

 #define VERITY_METADATA_SIZE 32768
 #define VERITY_TABLE_RSA_KEY "/verity_key"

 #define VERITY_STATE_HEADER 0x83c0ae9d
 #define VERITY_STATE_VERSION 1

 #define VERITY_KMSG_RESTART "dm-verity device corrupted"
 #define VERITY_KMSG_BUFSIZE 1024

 struct verity_state {
     uint32_t header;
     uint32_t version;
     uint32_t size;
     int32_t mode;
 };

 extern struct fs_info info;

 static RSAPublicKey *load_key(char *path)
 {
     FILE *f;
     RSAPublicKey *key;

     key = malloc(sizeof(RSAPublicKey));
     if (!key) {
         ERROR("Can't malloc key\n");
         return NULL;
     }

     f = fopen(path, "r");
     if (!f) {
         ERROR("Can't open '%s'\n", path);
         free(key);
         return NULL;
     }

     if (!fread(key, sizeof(*key), 1, f)) {
         ERROR("Could not read key!");
         fclose(f);
         free(key);
         return NULL;
     }

     if (key->len != RSANUMWORDS) {
         ERROR("Invalid key length %d\n", key->len);
         fclose(f);
         free(key);
         return NULL;
     }

     fclose(f);
     return key;
 }

 static int verify_table(char *signature, char *table, int table_length)
 {
     RSAPublicKey *key;
     uint8_t hash_buf[SHA_DIGEST_SIZE];
     int retval = -1;

     // Hash the table
     SHA_hash((uint8_t*)table, table_length, hash_buf);

     // Now get the public key from the keyfile
     key = load_key(VERITY_TABLE_RSA_KEY);
     if (!key) {
         ERROR("Couldn't load verity keys");
         goto out;
     }

     // verify the result
     if (!RSA_verify(key,
                     (uint8_t*) signature,
                     RSANUMBYTES,
                     (uint8_t*) hash_buf,
                     SHA_DIGEST_SIZE)) {
         ERROR("Couldn't verify table.");
         goto out;
     }

     retval = 0;

 out:
     free(key);
     return retval;
 }

 static int get_target_device_size(char *blk_device, uint64_t *device_size)
 {
     int data_device;
     struct ext4_super_block sb;
     struct fs_info info;

     info.len = 0;  /* Only len is set to 0 to ask the device for real size. */

     data_device = TEMP_FAILURE_RETRY(open(blk_device, O_RDONLY | O_CLOEXEC));
     if (data_device == -1) {
         ERROR("Error opening block device (%s)", strerror(errno));
         return -1;
     }

     if (TEMP_FAILURE_RETRY(lseek64(data_device, 1024, SEEK_SET)) < 0) {
         ERROR("Error seeking to superblock");
         TEMP_FAILURE_RETRY(close(data_device));
         return -1;
     }

     if (TEMP_FAILURE_RETRY(read(data_device, &sb, sizeof(sb))) != sizeof(sb)) {
         ERROR("Error reading superblock");
         TEMP_FAILURE_RETRY(close(data_device));
         return -1;
     }

     ext4_parse_sb(&sb, &info);
     *device_size = info.len;

     TEMP_FAILURE_RETRY(close(data_device));
     return 0;
 }

 static int read_verity_metadata(char *block_device, char **signature, char **table)
 {
     unsigned magic_number;
     unsigned table_length;
     uint64_t device_length;
     int protocol_version;
     int device;
     int retval = FS_MGR_SETUP_VERITY_FAIL;
     *signature = 0;
     *table = 0;

     device = TEMP_FAILURE_RETRY(open(block_device, O_RDONLY | O_CLOEXEC));
     if (device == -1) {
         ERROR("Could not open block device %s (%s).\n", block_device, strerror(errno));
         goto out;
     }

     // find the start of the verity metadata
     if (get_target_device_size(block_device, &device_length) < 0) {
         ERROR("Could not get target device size.\n");
         goto out;
     }
     if (TEMP_FAILURE_RETRY(lseek64(device, device_length, SEEK_SET)) < 0) {
         ERROR("Could not seek to start of verity metadata block.\n");
         goto out;
     }

     // check the magic number
     if (TEMP_FAILURE_RETRY(read(device, &magic_number, sizeof(magic_number))) !=
             sizeof(magic_number)) {
         ERROR("Couldn't read magic number!\n");
         goto out;
     }

 #ifdef ALLOW_ADBD_DISABLE_VERITY
     if (magic_number == VERITY_METADATA_MAGIC_DISABLE) {
         retval = FS_MGR_SETUP_VERITY_DISABLED;
         INFO("Attempt to cleanly disable verity - only works in USERDEBUG");
         goto out;
     }
 #endif

     if (magic_number != VERITY_METADATA_MAGIC_NUMBER) {
         ERROR("Couldn't find verity metadata at offset %"PRIu64"!\n",
               device_length);
         goto out;
     }

     // check the protocol version
     if (TEMP_FAILURE_RETRY(read(device, &protocol_version,
             sizeof(protocol_version))) != sizeof(protocol_version)) {
         ERROR("Couldn't read verity metadata protocol version!\n");
         goto out;
     }
     if (protocol_version != 0) {
         ERROR("Got unknown verity metadata protocol version %d!\n", protocol_version);
         goto out;
     }

     // get the signature
     *signature = (char*) malloc(RSANUMBYTES);
     if (!*signature) {
         ERROR("Couldn't allocate memory for signature!\n");
         goto out;
     }
     if (TEMP_FAILURE_RETRY(read(device, *signature, RSANUMBYTES)) != RSANUMBYTES) {
         ERROR("Couldn't read signature from verity metadata!\n");
         goto out;
     }

     // get the size of the table
     if (TEMP_FAILURE_RETRY(read(device, &table_length, sizeof(table_length))) !=
             sizeof(table_length)) {
         ERROR("Couldn't get the size of the verity table from metadata!\n");
         goto out;
     }

     // get the table + null terminator
     *table = malloc(table_length + 1);
     if (!*table) {
         ERROR("Couldn't allocate memory for verity table!\n");
         goto out;
     }
     if (TEMP_FAILURE_RETRY(read(device, *table, table_length)) !=
             (ssize_t)table_length) {
         ERROR("Couldn't read the verity table from metadata!\n");
         goto out;
     }

     (*table)[table_length] = 0;
     retval = FS_MGR_SETUP_VERITY_SUCCESS;

 out:
     if (device != -1)
         TEMP_FAILURE_RETRY(close(device));

     if (retval != FS_MGR_SETUP_VERITY_SUCCESS) {
         free(*table);
         free(*signature);
         *table = 0;
         *signature = 0;
     }

     return retval;
 }

 static void verity_ioctl_init(struct dm_ioctl *io, char *name, unsigned flags)
 {
     memset(io, 0, DM_BUF_SIZE);
     io->data_size = DM_BUF_SIZE;
     io->data_start = sizeof(struct dm_ioctl);
     io->version[0] = 4;
     io->version[1] = 0;
     io->version[2] = 0;
     io->flags = flags | DM_READONLY_FLAG;
     if (name) {
         strlcpy(io->name, name, sizeof(io->name));
     }
 }

 static int create_verity_device(struct dm_ioctl *io, char *name, int fd)
 {
     verity_ioctl_init(io, name, 1);
     if (ioctl(fd, DM_DEV_CREATE, io)) {
         ERROR("Error creating device mapping (%s)", strerror(errno));
         return -1;
     }
     return 0;
 }

 static int get_verity_device_name(struct dm_ioctl *io, char *name, int fd, char **dev_name)
 {
     verity_ioctl_init(io, name, 0);
     if (ioctl(fd, DM_DEV_STATUS, io)) {
         ERROR("Error fetching verity device number (%s)", strerror(errno));
         return -1;
     }
     int dev_num = (io->dev & 0xff) | ((io->dev >> 12) & 0xfff00);
     if (asprintf(dev_name, "/dev/block/dm-%u", dev_num) < 0) {
         ERROR("Error getting verity block device name (%s)", strerror(errno));
         return -1;
     }
     return 0;
 }

 static int load_verity_table(struct dm_ioctl *io, char *name, char *blockdev, int fd, char *table,
         int mode)
 {
     char *verity_params;
     char *buffer = (char*) io;
     size_t bufsize;
     uint64_t device_size = 0;

     if (get_target_device_size(blockdev, &device_size) < 0) {
         return -1;
     }

     verity_ioctl_init(io, name, DM_STATUS_TABLE_FLAG);

     struct dm_target_spec *tgt = (struct dm_target_spec *) &buffer[sizeof(struct dm_ioctl)];

     // set tgt arguments here
     io->target_count = 1;
     tgt->status=0;
     tgt->sector_start=0;
     tgt->length=device_size/512;
     strcpy(tgt->target_type, "verity");

     // build the verity params here
     verity_params = buffer + sizeof(struct dm_ioctl) + sizeof(struct dm_target_spec);
     bufsize = DM_BUF_SIZE - (verity_params - buffer);

     if (mode == VERITY_MODE_EIO) {
         // allow operation with older dm-verity drivers that are unaware
         // of the mode parameter by omitting it; this also means that we
         // cannot use logging mode with these drivers, they always cause
         // an I/O error for corrupted blocks
         strcpy(verity_params, table);
     } else if (snprintf(verity_params, bufsize, "%s %d", table, mode) < 0) {
         return -1;
     }

     // set next target boundary
     verity_params += strlen(verity_params) + 1;
     verity_params = (char*) (((unsigned long)verity_params + 7) & ~8);
     tgt->next = verity_params - buffer;

     // send the ioctl to load the verity table
     if (ioctl(fd, DM_TABLE_LOAD, io)) {
         ERROR("Error loading verity table (%s)", strerror(errno));
         return -1;
     }

     return 0;
 }

 static int resume_verity_table(struct dm_ioctl *io, char *name, int fd)
 {
     verity_ioctl_init(io, name, 0);
     if (ioctl(fd, DM_DEV_SUSPEND, io)) {
         ERROR("Error activating verity device (%s)", strerror(errno));
         return -1;
     }
     return 0;
 }

 static int test_access(char *device) {
     int tries = 25;
     while (tries--) {
         if (!access(device, F_OK) || errno != ENOENT) {
             return 0;
         }
         usleep(40 * 1000);
     }
     return -1;
 }

 static int set_verified_property(char *name) {
     int ret;
     char *key;
     ret = asprintf(&key, "partition.%s.verified", name);
     if (ret < 0) {
         ERROR("Error formatting verified property\n");
         return ret;
     }
     ret = PROP_NAME_MAX - strlen(key);
     if (ret < 0) {
         ERROR("Verified property name is too long\n");
         free(key);
         return -1;
     }
     ret = property_set(key, "1");
     if (ret < 0)
         ERROR("Error setting verified property %s: %d\n", key, ret);
     free(key);
     return ret;
 }

 static int check_verity_restart(const char *fname)
 {
     char buffer[VERITY_KMSG_BUFSIZE + 1];
     int fd;
     int rc = 0;
     ssize_t size;
     struct stat s;

     fd = TEMP_FAILURE_RETRY(open(fname, O_RDONLY | O_CLOEXEC));

     if (fd == -1) {
         if (errno != ENOENT) {
             ERROR("Failed to open %s (%s)\n", fname, strerror(errno));
         }
         goto out;
     }

     if (fstat(fd, &s) == -1) {
         ERROR("Failed to fstat %s (%s)\n", fname, strerror(errno));
         goto out;
     }

     size = VERITY_KMSG_BUFSIZE;

     if (size > s.st_size) {
         size = s.st_size;
     }

     if (lseek(fd, s.st_size - size, SEEK_SET) == -1) {
         ERROR("Failed to lseek %jd %s (%s)\n", (intmax_t)(s.st_size - size), fname,
             strerror(errno));
         goto out;
     }

     if (TEMP_FAILURE_RETRY(read(fd, buffer, size)) != size) {
         ERROR("Failed to read %zd bytes from %s (%s)\n", size, fname,
             strerror(errno));
         goto out;
     }

     buffer[size] = '\0';

     if (strstr(buffer, VERITY_KMSG_RESTART) != NULL) {
         rc = 1;
     }

 out:
     if (fd != -1) {
         TEMP_FAILURE_RETRY(close(fd));
     }

     return rc;
 }

 static int was_verity_restart()
 {
     static const char *files[] = {
         "/sys/fs/pstore/console-ramoops",
         "/proc/last_kmsg",
         NULL
     };
     int i;

     for (i = 0; files[i]; ++i) {
         if (check_verity_restart(files[i])) {
             return 1;
         }
     }

     return 0;
 }

 static int write_verity_state(const char *fname, off64_t offset, int32_t mode)
 {
     int fd;
     int rc = -1;

     struct verity_state s = {
         VERITY_STATE_HEADER,
         VERITY_STATE_VERSION,
         sizeof(struct verity_state),
         mode
     };

     fd = TEMP_FAILURE_RETRY(open(fname, O_WRONLY | O_SYNC | O_CLOEXEC));

     if (fd == -1) {
         ERROR("Failed to open %s (%s)\n", fname, strerror(errno));
         goto out;
     }

     if (TEMP_FAILURE_RETRY(lseek64(fd, offset, SEEK_SET)) < 0) {
         ERROR("Failed to seek %s to %" PRIu64 " (%s)\n", fname, offset, strerror(errno));
         goto out;
     }

     if (TEMP_FAILURE_RETRY(write(fd, &s, sizeof(s))) != sizeof(s)) {
         ERROR("Failed to write %zu bytes to %s (%s)\n", sizeof(s), fname, strerror(errno));
         goto out;
     }

     rc = 0;

 out:
     if (fd != -1) {
         TEMP_FAILURE_RETRY(close(fd));
     }

     return rc;
 }

 static int get_verity_state_location(char *location, off64_t *offset)
 {
     char state_off[PROPERTY_VALUE_MAX];

     if (property_get("ro.verity.state.location", location, NULL) <= 0) {
         return -1;
     }

     if (*location != '/' || access(location, R_OK | W_OK) == -1) {
         ERROR("Failed to access verity state %s (%s)\n", location, strerror(errno));
         return -1;
     }

     *offset = 0;

     if (property_get("ro.verity.state.offset", state_off, NULL) > 0) {
         *offset = strtoll(state_off, NULL, 0);

         if (errno == ERANGE || errno == EINVAL) {
             ERROR("Invalid value in ro.verity.state.offset (%s)\n", state_off);
             return -1;
         }
     }

     return 0;
 }

 int fs_mgr_load_verity_state(int *mode)
 {
     char fname[PROPERTY_VALUE_MAX];
     int fd = -1;
     int rc = -1;
     off64_t offset = 0;
     struct verity_state s;

     if (get_verity_state_location(fname, &offset) < 0) {
         /* location for dm-verity state is not specified, fall back to
          * default behavior: return -EIO for corrupted blocks */
         *mode = VERITY_MODE_EIO;
         rc = 0;
         goto out;
     }

     if (was_verity_restart()) {
         /* device was restarted after dm-verity detected a corrupted
          * block, so switch to logging mode */
         *mode = VERITY_MODE_LOGGING;
         rc = write_verity_state(fname, offset, *mode);
         goto out;
     }

     fd = TEMP_FAILURE_RETRY(open(fname, O_RDONLY | O_CLOEXEC));

     if (fd == -1) {
         ERROR("Failed to open %s (%s)\n", fname, strerror(errno));
         goto out;
     }

     if (TEMP_FAILURE_RETRY(lseek64(fd, offset, SEEK_SET)) < 0) {
         ERROR("Failed to seek %s to %" PRIu64 " (%s)\n", fname, offset, strerror(errno));
         goto out;
     }

     if (TEMP_FAILURE_RETRY(read(fd, &s, sizeof(s))) != sizeof(s)) {
         ERROR("Failed to read %zu bytes from %s (%s)\n", sizeof(s), fname, strerror(errno));
         goto out;
     }

     if (s.header != VERITY_STATE_HEADER) {
         goto out;
     }

     if (s.version != VERITY_STATE_VERSION) {
         ERROR("Unsupported verity state version (%u)\n", s.version);
         goto out;
     }

     if (s.size != sizeof(s)) {
         ERROR("Unexpected verity state size (%u)\n", s.size);
         goto out;
     }

     if (s.mode < VERITY_MODE_EIO ||
         s.mode > VERITY_MODE_LAST) {
         ERROR("Unsupported verity mode (%u)\n", s.mode);
         goto out;
     }

     *mode = s.mode;
     rc = 0;

 out:
     if (fd != -1) {
         TEMP_FAILURE_RETRY(close(fd));
     }

     return rc;
 }

 int fs_mgr_update_verity_state()
 {
     _Alignas(struct dm_ioctl) char buffer[DM_BUF_SIZE];
     char fstab_filename[PROPERTY_VALUE_MAX + sizeof(FSTAB_PREFIX)];
     char *mount_point;
     char propbuf[PROPERTY_VALUE_MAX];
     char state_loc[PROPERTY_VALUE_MAX];
     char *status;
     int fd = -1;
     int i;
     int rc = -1;
     off64_t offset = 0;
     struct dm_ioctl *io = (struct dm_ioctl *) buffer;
     struct fstab *fstab = NULL;

     if (get_verity_state_location(state_loc, &offset) < 0) {
         goto out;
     }

     fd = TEMP_FAILURE_RETRY(open("/dev/device-mapper", O_RDWR | O_CLOEXEC));

     if (fd == -1) {
         ERROR("Error opening device mapper (%s)\n", strerror(errno));
         goto out;
     }

     property_get("ro.hardware", propbuf, "");
     snprintf(fstab_filename, sizeof(fstab_filename), FSTAB_PREFIX"%s", propbuf);

     fstab = fs_mgr_read_fstab(fstab_filename);

     if (!fstab) {
         ERROR("Failed to read %s\n", fstab_filename);
         goto out;
     }

     for (i = 0; i < fstab->num_entries; i++) {
         if (!fs_mgr_is_verified(&fstab->recs[i])) {
             continue;
         }

         mount_point = basename(fstab->recs[i].mount_point);
         verity_ioctl_init(io, mount_point, 0);

         if (ioctl(fd, DM_TABLE_STATUS, io)) {
             ERROR("Failed to query DM_TABLE_STATUS for %s (%s)\n", mount_point,
                 strerror(errno));
             goto out;
         }

         status = &buffer[io->data_start + sizeof(struct dm_target_spec)];

         if (*status == 'C') {
             rc = write_verity_state(state_loc, offset, VERITY_MODE_LOGGING);
             goto out;
         }
     }

     /* Don't overwrite possible previous state if there's no corruption. */
     rc = 0;

 out:
     if (fstab) {
         fs_mgr_free_fstab(fstab);
     }

     if (fd) {
         TEMP_FAILURE_RETRY(close(fd));
     }

     return rc;
 }

 int fs_mgr_setup_verity(struct fstab_rec *fstab) {

     int retval = FS_MGR_SETUP_VERITY_FAIL;
     int fd = -1;
     int mode;

     char *verity_blk_name = 0;
     char *verity_table = 0;
     char *verity_table_signature = 0;

     _Alignas(struct dm_ioctl) char buffer[DM_BUF_SIZE];
     struct dm_ioctl *io = (struct dm_ioctl *) buffer;
     char *mount_point = basename(fstab->mount_point);

     // set the dm_ioctl flags
     io->flags |= 1;
     io->target_count = 1;

     // check to ensure that the verity device is ext4
     // TODO: support non-ext4 filesystems
     if (strcmp(fstab->fs_type, "ext4")) {
         ERROR("Cannot verify non-ext4 device (%s)", fstab->fs_type);
         return retval;
     }

     // read the verity block at the end of the block device
     // send error code up the chain so we can detect attempts to disable verity
     retval = read_verity_metadata(fstab->blk_device,
                                   &verity_table_signature,
                                   &verity_table);
     if (retval < 0) {
         goto out;
     }

     retval = FS_MGR_SETUP_VERITY_FAIL;

     // get the device mapper fd
     if ((fd = open("/dev/device-mapper", O_RDWR)) < 0) {
         ERROR("Error opening device mapper (%s)", strerror(errno));
         goto out;
     }

     // create the device
     if (create_verity_device(io, mount_point, fd) < 0) {
         ERROR("Couldn't create verity device!");
         goto out;
     }

     // get the name of the device file
     if (get_verity_device_name(io, mount_point, fd, &verity_blk_name) < 0) {
         ERROR("Couldn't get verity device number!");
         goto out;
     }

     // verify the signature on the table
     if (verify_table(verity_table_signature,
                             verity_table,
                             strlen(verity_table)) < 0) {
         goto out;
     }

     if (fs_mgr_load_verity_state(&mode) < 0) {
         mode = VERITY_MODE_RESTART; /* default dm-verity mode */
     }

     // load the verity mapping table
     if (load_verity_table(io, mount_point, fstab->blk_device, fd, verity_table,
             mode) < 0) {
         goto out;
     }

     // activate the device
     if (resume_verity_table(io, mount_point, fd) < 0) {
         goto out;
     }

     // mark the underlying block device as read-only
     fs_mgr_set_blk_ro(fstab->blk_device);

     // assign the new verity block device as the block device
     free(fstab->blk_device);
     fstab->blk_device = verity_blk_name;
     verity_blk_name = 0;

     // make sure we've set everything up properly
     if (test_access(fstab->blk_device) < 0) {
         goto out;
     }

     if (mode == VERITY_MODE_LOGGING) {
         retval = FS_MGR_SETUP_VERITY_SUCCESS;
     } else {
         // set the property indicating that the partition is verified
         retval = set_verified_property(mount_point);
     }

 out:
     if (fd != -1) {
         close(fd);
     }

     free(verity_table);
     free(verity_table_signature);
     free(verity_blk_name);

     return retval;
 }
	/*
	* Copyright (C) 2013 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include <inttypes.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>
	#include <fcntl.h>
	#include <ctype.h>
	#include <sys/mount.h>
	#include <sys/stat.h>
	#include <errno.h>
	#include <sys/types.h>
	#include <sys/wait.h>
	#include <libgen.h>
	#include <time.h>

	#include <private/android_filesystem_config.h>
	#include <cutils/properties.h>
	#include <logwrap/logwrap.h>

	#include "mincrypt/rsa.h"
	#include "mincrypt/sha.h"
	#include "mincrypt/sha256.h"

	#include "ext4_sb.h"

	#include "fs_mgr_priv.h"
	#include "fs_mgr_priv_verity.h"

	#define FSTAB_PREFIX "/fstab."

	#define VERITY_METADATA_SIZE 32768
	#define VERITY_TABLE_RSA_KEY "/verity_key"

	#define VERITY_STATE_HEADER 0x83c0ae9d
	#define VERITY_STATE_VERSION 1

	#define VERITY_KMSG_RESTART "dm-verity device corrupted"
	#define VERITY_KMSG_BUFSIZE 1024

	struct verity_state {
	uint32_t header;
	uint32_t version;
	uint32_t size;
	int32_t mode;
	};

	extern struct fs_info info;

	static RSAPublicKey load_key(char path)
	{
	FILE *f;
	RSAPublicKey *key;

	key = malloc(sizeof(RSAPublicKey));
	if (!key) {
	ERROR("Can't malloc key\n");
	return NULL;
	}

	f = fopen(path, "r");
	if (!f) {
	ERROR("Can't open '%s'\n", path);
	free(key);
	return NULL;
	}

	if (!fread(key, sizeof(*key), 1, f)) {
	ERROR("Could not read key!");
	fclose(f);
	free(key);
	return NULL;
	}

	if (key->len != RSANUMWORDS) {
	ERROR("Invalid key length %d\n", key->len);
	fclose(f);
	free(key);
	return NULL;
	}

	fclose(f);
	return key;
	}

	static int verify_table(char signature, char table, int table_length)
	{
	RSAPublicKey *key;
	uint8_t hash_buf[SHA_DIGEST_SIZE];
	int retval = -1;

	// Hash the table
	SHA_hash((uint8_t*)table, table_length, hash_buf);

	// Now get the public key from the keyfile
	key = load_key(VERITY_TABLE_RSA_KEY);
	if (!key) {
	ERROR("Couldn't load verity keys");
	goto out;
	}

	// verify the result
	if (!RSA_verify(key,
	(uint8_t*) signature,
	RSANUMBYTES,
	(uint8_t*) hash_buf,
	SHA_DIGEST_SIZE)) {
	ERROR("Couldn't verify table.");
	goto out;
	}

	retval = 0;

	out:
	free(key);
	return retval;
	}

	static int get_target_device_size(char blk_device, uint64_t device_size)
	{
	int data_device;
	struct ext4_super_block sb;
	struct fs_info info;

	info.len = 0; /* Only len is set to 0 to ask the device for real size. */

	data_device = TEMP_FAILURE_RETRY(open(blk_device, O_RDONLY \| O_CLOEXEC));
	if (data_device == -1) {
	ERROR("Error opening block device (%s)", strerror(errno));
	return -1;
	}

	if (TEMP_FAILURE_RETRY(lseek64(data_device, 1024, SEEK_SET)) < 0) {
	ERROR("Error seeking to superblock");
	TEMP_FAILURE_RETRY(close(data_device));
	return -1;
	}

	if (TEMP_FAILURE_RETRY(read(data_device, &sb, sizeof(sb))) != sizeof(sb)) {
	ERROR("Error reading superblock");
	TEMP_FAILURE_RETRY(close(data_device));
	return -1;
	}

	ext4_parse_sb(&sb, &info);
	*device_size = info.len;

	TEMP_FAILURE_RETRY(close(data_device));
	return 0;
	}

	static int read_verity_metadata(char block_device, char signature, char *table)
	{
	unsigned magic_number;
	unsigned table_length;
	uint64_t device_length;
	int protocol_version;
	int device;
	int retval = FS_MGR_SETUP_VERITY_FAIL;
	*signature = 0;
	*table = 0;

	device = TEMP_FAILURE_RETRY(open(block_device, O_RDONLY \| O_CLOEXEC));
	if (device == -1) {
	ERROR("Could not open block device %s (%s).\n", block_device, strerror(errno));
	goto out;
	}

	// find the start of the verity metadata
	if (get_target_device_size(block_device, &device_length) < 0) {
	ERROR("Could not get target device size.\n");
	goto out;
	}
	if (TEMP_FAILURE_RETRY(lseek64(device, device_length, SEEK_SET)) < 0) {
	ERROR("Could not seek to start of verity metadata block.\n");
	goto out;
	}

	// check the magic number
	if (TEMP_FAILURE_RETRY(read(device, &magic_number, sizeof(magic_number))) !=
	sizeof(magic_number)) {
	ERROR("Couldn't read magic number!\n");
	goto out;
	}

	#ifdef ALLOW_ADBD_DISABLE_VERITY
	if (magic_number == VERITY_METADATA_MAGIC_DISABLE) {
	retval = FS_MGR_SETUP_VERITY_DISABLED;
	INFO("Attempt to cleanly disable verity - only works in USERDEBUG");
	goto out;
	}
	#endif

	if (magic_number != VERITY_METADATA_MAGIC_NUMBER) {
	ERROR("Couldn't find verity metadata at offset %"PRIu64"!\n",
	device_length);
	goto out;
	}

	// check the protocol version
	if (TEMP_FAILURE_RETRY(read(device, &protocol_version,
	sizeof(protocol_version))) != sizeof(protocol_version)) {
	ERROR("Couldn't read verity metadata protocol version!\n");
	goto out;
	}
	if (protocol_version != 0) {
	ERROR("Got unknown verity metadata protocol version %d!\n", protocol_version);
	goto out;
	}

	// get the signature
	signature = (char) malloc(RSANUMBYTES);
	if (!*signature) {
	ERROR("Couldn't allocate memory for signature!\n");
	goto out;
	}
	if (TEMP_FAILURE_RETRY(read(device, *signature, RSANUMBYTES)) != RSANUMBYTES) {
	ERROR("Couldn't read signature from verity metadata!\n");
	goto out;
	}

	// get the size of the table
	if (TEMP_FAILURE_RETRY(read(device, &table_length, sizeof(table_length))) !=
	sizeof(table_length)) {
	ERROR("Couldn't get the size of the verity table from metadata!\n");
	goto out;
	}

	// get the table + null terminator
	*table = malloc(table_length + 1);
	if (!*table) {
	ERROR("Couldn't allocate memory for verity table!\n");
	goto out;
	}
	if (TEMP_FAILURE_RETRY(read(device, *table, table_length)) !=
	(ssize_t)table_length) {
	ERROR("Couldn't read the verity table from metadata!\n");
	goto out;
	}

	(*table)[table_length] = 0;
	retval = FS_MGR_SETUP_VERITY_SUCCESS;

	out:
	if (device != -1)
	TEMP_FAILURE_RETRY(close(device));

	if (retval != FS_MGR_SETUP_VERITY_SUCCESS) {
	free(*table);
	free(*signature);
	*table = 0;
	*signature = 0;
	}

	return retval;
	}

	static void verity_ioctl_init(struct dm_ioctl io, char name, unsigned flags)
	{
	memset(io, 0, DM_BUF_SIZE);
	io->data_size = DM_BUF_SIZE;
	io->data_start = sizeof(struct dm_ioctl);
	io->version[0] = 4;
	io->version[1] = 0;
	io->version[2] = 0;
	io->flags = flags \| DM_READONLY_FLAG;
	if (name) {
	strlcpy(io->name, name, sizeof(io->name));
	}
	}

	static int create_verity_device(struct dm_ioctl io, char name, int fd)
	{
	verity_ioctl_init(io, name, 1);
	if (ioctl(fd, DM_DEV_CREATE, io)) {
	ERROR("Error creating device mapping (%s)", strerror(errno));
	return -1;
	}
	return 0;
	}

	static int get_verity_device_name(struct dm_ioctl io, char name, int fd, char **dev_name)
	{
	verity_ioctl_init(io, name, 0);
	if (ioctl(fd, DM_DEV_STATUS, io)) {
	ERROR("Error fetching verity device number (%s)", strerror(errno));
	return -1;
	}
	int dev_num = (io->dev & 0xff) \| ((io->dev >> 12) & 0xfff00);
	if (asprintf(dev_name, "/dev/block/dm-%u", dev_num) < 0) {
	ERROR("Error getting verity block device name (%s)", strerror(errno));
	return -1;
	}
	return 0;
	}

	static int load_verity_table(struct dm_ioctl io, char name, char blockdev, int fd, char table,
	int mode)
	{
	char *verity_params;
	char buffer = (char) io;
	size_t bufsize;
	uint64_t device_size = 0;

	if (get_target_device_size(blockdev, &device_size) < 0) {
	return -1;
	}

	verity_ioctl_init(io, name, DM_STATUS_TABLE_FLAG);

	struct dm_target_spec tgt = (struct dm_target_spec ) &buffer[sizeof(struct dm_ioctl)];

	// set tgt arguments here
	io->target_count = 1;
	tgt->status=0;
	tgt->sector_start=0;
	tgt->length=device_size/512;
	strcpy(tgt->target_type, "verity");

	// build the verity params here
	verity_params = buffer + sizeof(struct dm_ioctl) + sizeof(struct dm_target_spec);
	bufsize = DM_BUF_SIZE - (verity_params - buffer);

	if (mode == VERITY_MODE_EIO) {
	// allow operation with older dm-verity drivers that are unaware
	// of the mode parameter by omitting it; this also means that we
	// cannot use logging mode with these drivers, they always cause
	// an I/O error for corrupted blocks
	strcpy(verity_params, table);
	} else if (snprintf(verity_params, bufsize, "%s %d", table, mode) < 0) {
	return -1;
	}

	// set next target boundary
	verity_params += strlen(verity_params) + 1;
	verity_params = (char*) (((unsigned long)verity_params + 7) & ~8);
	tgt->next = verity_params - buffer;

	// send the ioctl to load the verity table
	if (ioctl(fd, DM_TABLE_LOAD, io)) {
	ERROR("Error loading verity table (%s)", strerror(errno));
	return -1;
	}

	return 0;
	}

	static int resume_verity_table(struct dm_ioctl io, char name, int fd)
	{
	verity_ioctl_init(io, name, 0);
	if (ioctl(fd, DM_DEV_SUSPEND, io)) {
	ERROR("Error activating verity device (%s)", strerror(errno));
	return -1;
	}
	return 0;
	}

	static int test_access(char *device) {
	int tries = 25;
	while (tries--) {
	if (!access(device, F_OK) \|\| errno != ENOENT) {
	return 0;
	}
	usleep(40 * 1000);
	}
	return -1;
	}

	static int set_verified_property(char *name) {
	int ret;
	char *key;
	ret = asprintf(&key, "partition.%s.verified", name);
	if (ret < 0) {
	ERROR("Error formatting verified property\n");
	return ret;
	}
	ret = PROP_NAME_MAX - strlen(key);
	if (ret < 0) {
	ERROR("Verified property name is too long\n");
	free(key);
	return -1;
	}
	ret = property_set(key, "1");
	if (ret < 0)
	ERROR("Error setting verified property %s: %d\n", key, ret);
	free(key);
	return ret;
	}

	static int check_verity_restart(const char *fname)
	{
	char buffer[VERITY_KMSG_BUFSIZE + 1];
	int fd;
	int rc = 0;
	ssize_t size;
	struct stat s;

	fd = TEMP_FAILURE_RETRY(open(fname, O_RDONLY \| O_CLOEXEC));

	if (fd == -1) {
	if (errno != ENOENT) {
	ERROR("Failed to open %s (%s)\n", fname, strerror(errno));
	}
	goto out;
	}

	if (fstat(fd, &s) == -1) {
	ERROR("Failed to fstat %s (%s)\n", fname, strerror(errno));
	goto out;
	}

	size = VERITY_KMSG_BUFSIZE;

	if (size > s.st_size) {
	size = s.st_size;
	}

	if (lseek(fd, s.st_size - size, SEEK_SET) == -1) {
	ERROR("Failed to lseek %jd %s (%s)\n", (intmax_t)(s.st_size - size), fname,
	strerror(errno));
	goto out;
	}

	if (TEMP_FAILURE_RETRY(read(fd, buffer, size)) != size) {
	ERROR("Failed to read %zd bytes from %s (%s)\n", size, fname,
	strerror(errno));
	goto out;
	}

	buffer[size] = '\0';

	if (strstr(buffer, VERITY_KMSG_RESTART) != NULL) {
	rc = 1;
	}

	out:
	if (fd != -1) {
	TEMP_FAILURE_RETRY(close(fd));
	}

	return rc;
	}

	static int was_verity_restart()
	{
	static const char *files[] = {
	"/sys/fs/pstore/console-ramoops",
	"/proc/last_kmsg",
	NULL
	};
	int i;

	for (i = 0; files[i]; ++i) {
	if (check_verity_restart(files[i])) {
	return 1;
	}
	}

	return 0;
	}

	static int write_verity_state(const char *fname, off64_t offset, int32_t mode)
	{
	int fd;
	int rc = -1;

	struct verity_state s = {
	VERITY_STATE_HEADER,
	VERITY_STATE_VERSION,
	sizeof(struct verity_state),
	mode
	};

	fd = TEMP_FAILURE_RETRY(open(fname, O_WRONLY \| O_SYNC \| O_CLOEXEC));

	if (fd == -1) {
	ERROR("Failed to open %s (%s)\n", fname, strerror(errno));
	goto out;
	}

	if (TEMP_FAILURE_RETRY(lseek64(fd, offset, SEEK_SET)) < 0) {
	ERROR("Failed to seek %s to %" PRIu64 " (%s)\n", fname, offset, strerror(errno));
	goto out;
	}

	if (TEMP_FAILURE_RETRY(write(fd, &s, sizeof(s))) != sizeof(s)) {
	ERROR("Failed to write %zu bytes to %s (%s)\n", sizeof(s), fname, strerror(errno));
	goto out;
	}

	rc = 0;

	out:
	if (fd != -1) {
	TEMP_FAILURE_RETRY(close(fd));
	}

	return rc;
	}

	static int get_verity_state_location(char location, off64_t offset)
	{
	char state_off[PROPERTY_VALUE_MAX];

	if (property_get("ro.verity.state.location", location, NULL) <= 0) {
	return -1;
	}

	if (*location != '/' \|\| access(location, R_OK \| W_OK) == -1) {
	ERROR("Failed to access verity state %s (%s)\n", location, strerror(errno));
	return -1;
	}

	*offset = 0;

	if (property_get("ro.verity.state.offset", state_off, NULL) > 0) {
	*offset = strtoll(state_off, NULL, 0);

	if (errno == ERANGE \|\| errno == EINVAL) {
	ERROR("Invalid value in ro.verity.state.offset (%s)\n", state_off);
	return -1;
	}
	}

	return 0;
	}

	int fs_mgr_load_verity_state(int *mode)
	{
	char fname[PROPERTY_VALUE_MAX];
	int fd = -1;
	int rc = -1;
	off64_t offset = 0;
	struct verity_state s;

	if (get_verity_state_location(fname, &offset) < 0) {
	/* location for dm-verity state is not specified, fall back to
	* default behavior: return -EIO for corrupted blocks */
	*mode = VERITY_MODE_EIO;
	rc = 0;
	goto out;
	}

	if (was_verity_restart()) {
	/* device was restarted after dm-verity detected a corrupted
	* block, so switch to logging mode */
	*mode = VERITY_MODE_LOGGING;
	rc = write_verity_state(fname, offset, *mode);
	goto out;
	}

	fd = TEMP_FAILURE_RETRY(open(fname, O_RDONLY \| O_CLOEXEC));

	if (fd == -1) {
	ERROR("Failed to open %s (%s)\n", fname, strerror(errno));
	goto out;
	}

	if (TEMP_FAILURE_RETRY(lseek64(fd, offset, SEEK_SET)) < 0) {
	ERROR("Failed to seek %s to %" PRIu64 " (%s)\n", fname, offset, strerror(errno));
	goto out;
	}

	if (TEMP_FAILURE_RETRY(read(fd, &s, sizeof(s))) != sizeof(s)) {
	ERROR("Failed to read %zu bytes from %s (%s)\n", sizeof(s), fname, strerror(errno));
	goto out;
	}

	if (s.header != VERITY_STATE_HEADER) {
	goto out;
	}

	if (s.version != VERITY_STATE_VERSION) {
	ERROR("Unsupported verity state version (%u)\n", s.version);
	goto out;
	}

	if (s.size != sizeof(s)) {
	ERROR("Unexpected verity state size (%u)\n", s.size);
	goto out;
	}

	if (s.mode < VERITY_MODE_EIO \|\|
	s.mode > VERITY_MODE_LAST) {
	ERROR("Unsupported verity mode (%u)\n", s.mode);
	goto out;
	}

	*mode = s.mode;
	rc = 0;

	out:
	if (fd != -1) {
	TEMP_FAILURE_RETRY(close(fd));
	}

	return rc;
	}

	int fs_mgr_update_verity_state()
	{
	_Alignas(struct dm_ioctl) char buffer[DM_BUF_SIZE];
	char fstab_filename[PROPERTY_VALUE_MAX + sizeof(FSTAB_PREFIX)];
	char *mount_point;
	char propbuf[PROPERTY_VALUE_MAX];
	char state_loc[PROPERTY_VALUE_MAX];
	char *status;
	int fd = -1;
	int i;
	int rc = -1;
	off64_t offset = 0;
	struct dm_ioctl io = (struct dm_ioctl ) buffer;
	struct fstab *fstab = NULL;

	if (get_verity_state_location(state_loc, &offset) < 0) {
	goto out;
	}

	fd = TEMP_FAILURE_RETRY(open("/dev/device-mapper", O_RDWR \| O_CLOEXEC));

	if (fd == -1) {
	ERROR("Error opening device mapper (%s)\n", strerror(errno));
	goto out;
	}

	property_get("ro.hardware", propbuf, "");
	snprintf(fstab_filename, sizeof(fstab_filename), FSTAB_PREFIX"%s", propbuf);

	fstab = fs_mgr_read_fstab(fstab_filename);

	if (!fstab) {
	ERROR("Failed to read %s\n", fstab_filename);
	goto out;
	}

	for (i = 0; i < fstab->num_entries; i++) {
	if (!fs_mgr_is_verified(&fstab->recs[i])) {
	continue;
	}

	mount_point = basename(fstab->recs[i].mount_point);
	verity_ioctl_init(io, mount_point, 0);

	if (ioctl(fd, DM_TABLE_STATUS, io)) {
	ERROR("Failed to query DM_TABLE_STATUS for %s (%s)\n", mount_point,
	strerror(errno));
	goto out;
	}

	status = &buffer[io->data_start + sizeof(struct dm_target_spec)];

	if (*status == 'C') {
	rc = write_verity_state(state_loc, offset, VERITY_MODE_LOGGING);
	goto out;
	}
	}

	/* Don't overwrite possible previous state if there's no corruption. */
	rc = 0;

	out:
	if (fstab) {
	fs_mgr_free_fstab(fstab);
	}

	if (fd) {
	TEMP_FAILURE_RETRY(close(fd));
	}

	return rc;
	}

	int fs_mgr_setup_verity(struct fstab_rec *fstab) {

	int retval = FS_MGR_SETUP_VERITY_FAIL;
	int fd = -1;
	int mode;

	char *verity_blk_name = 0;
	char *verity_table = 0;
	char *verity_table_signature = 0;

	_Alignas(struct dm_ioctl) char buffer[DM_BUF_SIZE];
	struct dm_ioctl io = (struct dm_ioctl ) buffer;
	char *mount_point = basename(fstab->mount_point);

	// set the dm_ioctl flags
	io->flags \|= 1;
	io->target_count = 1;

	// check to ensure that the verity device is ext4
	// TODO: support non-ext4 filesystems
	if (strcmp(fstab->fs_type, "ext4")) {
	ERROR("Cannot verify non-ext4 device (%s)", fstab->fs_type);
	return retval;
	}

	// read the verity block at the end of the block device
	// send error code up the chain so we can detect attempts to disable verity
	retval = read_verity_metadata(fstab->blk_device,
	&verity_table_signature,
	&verity_table);
	if (retval < 0) {
	goto out;
	}

	retval = FS_MGR_SETUP_VERITY_FAIL;

	// get the device mapper fd
	if ((fd = open("/dev/device-mapper", O_RDWR)) < 0) {
	ERROR("Error opening device mapper (%s)", strerror(errno));
	goto out;
	}

	// create the device
	if (create_verity_device(io, mount_point, fd) < 0) {
	ERROR("Couldn't create verity device!");
	goto out;
	}

	// get the name of the device file
	if (get_verity_device_name(io, mount_point, fd, &verity_blk_name) < 0) {
	ERROR("Couldn't get verity device number!");
	goto out;
	}

	// verify the signature on the table
	if (verify_table(verity_table_signature,
	verity_table,
	strlen(verity_table)) < 0) {
	goto out;
	}

	if (fs_mgr_load_verity_state(&mode) < 0) {
	mode = VERITY_MODE_RESTART; /* default dm-verity mode */
	}

	// load the verity mapping table
	if (load_verity_table(io, mount_point, fstab->blk_device, fd, verity_table,
	mode) < 0) {
	goto out;
	}

	// activate the device
	if (resume_verity_table(io, mount_point, fd) < 0) {
	goto out;
	}

	// mark the underlying block device as read-only
	fs_mgr_set_blk_ro(fstab->blk_device);

	// assign the new verity block device as the block device
	free(fstab->blk_device);
	fstab->blk_device = verity_blk_name;
	verity_blk_name = 0;

	// make sure we've set everything up properly
	if (test_access(fstab->blk_device) < 0) {
	goto out;
	}

	if (mode == VERITY_MODE_LOGGING) {
	retval = FS_MGR_SETUP_VERITY_SUCCESS;
	} else {
	// set the property indicating that the partition is verified
	retval = set_verified_property(mount_point);
	}

	out:
	if (fd != -1) {
	close(fd);
	}

	free(verity_table);
	free(verity_table_signature);
	free(verity_blk_name);

	return retval;
	}