Add basic verity support to fs_mgr.

This change adds a "verify" fs_mgr flag specifying that
the device in question should be verified.

Devices marked with this flag are expected to have a
footer immediately after their data containing all
the information needed to set up a verity instance.

Change-Id: I10101f2c3240228ee0932e3767fe35e673d2e720

7 files changed, 465 insertions, 7 deletions

diff --git a/fs_mgr/Android.mk b/fs_mgr/Android.mk
index 782ae99..790598a 100644
--- a/fs_mgr/Android.mk
+++ b/fs_mgr/Android.mk
@@ -3,12 +3,13 @@
 LOCAL_PATH:= $(call my-dir)
 include $(CLEAR_VARS)
 
-LOCAL_SRC_FILES:= fs_mgr.c
+LOCAL_SRC_FILES:= fs_mgr.c fs_mgr_verity.c
 
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
 
 LOCAL_MODULE:= libfs_mgr
-LOCAL_STATIC_LIBRARIES := liblogwrap
+LOCAL_STATIC_LIBRARIES := liblogwrap libmincrypt libext4_utils_static
+LOCAL_C_INCLUDES += system/extras/ext4_utils
 LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
 
 include $(BUILD_STATIC_LIBRARY)
@@ -28,7 +29,7 @@ LOCAL_FORCE_STATIC_EXECUTABLE := true
 LOCAL_MODULE_PATH := $(TARGET_ROOT_OUT)/sbin
 LOCAL_UNSTRIPPED_PATH := $(TARGET_ROOT_OUT_UNSTRIPPED)
 
-LOCAL_STATIC_LIBRARIES := libfs_mgr liblogwrap libcutils liblog libc
+LOCAL_STATIC_LIBRARIES := libfs_mgr liblogwrap libcutils liblog libc libmincrypt libext4_utils_static
 
 include $(BUILD_EXECUTABLE)
 
diff --git a/fs_mgr/fs_mgr.c b/fs_mgr/fs_mgr.c
index 2761545..82c5798 100644
--- a/fs_mgr/fs_mgr.c
+++ b/fs_mgr/fs_mgr.c
@@ -34,12 +34,18 @@
 #define SWAP_FLAG_PRIO_SHIFT    0
 #define SWAP_FLAG_DISCARD       0x10000
 
+#include <linux/loop.h>
 #include <private/android_filesystem_config.h>
 #include <cutils/partition_utils.h>
 #include <cutils/properties.h>
 #include <logwrap/logwrap.h>
 
+#include "mincrypt/rsa.h"
+#include "mincrypt/sha.h"
+#include "mincrypt/sha256.h"
+
 #include "fs_mgr_priv.h"
+#include "fs_mgr_priv_verity.h"
 
 #define KEY_LOC_PROP   "ro.crypto.keyfile.userdata"
 #define KEY_IN_FOOTER  "footer"
@@ -85,6 +91,7 @@ static struct flag_list fs_mgr_flags[] = {
     { "recoveryonly",MF_RECOVERYONLY },
     { "swapprio=",   MF_SWAPPRIO },
     { "zramsize=",   MF_ZRAMSIZE },
+    { "verify",      MF_VERIFY },
     { "defaults",    0 },
     { 0,             0 },
 };
@@ -588,9 +595,17 @@ int fs_mgr_mount_all(struct fstab *fstab)
                      fstab->recs[i].mount_point);
         }
 
+        if (fstab->recs[i].fs_mgr_flags & MF_VERIFY) {
+            if (fs_mgr_setup_verity(&fstab->recs[i]) < 0) {
+                ERROR("Could not set up verified partition, skipping!");
+                continue;
+            }
+        }
+
         mret = __mount(fstab->recs[i].blk_device, fstab->recs[i].mount_point,
-                       fstab->recs[i].fs_type, fstab->recs[i].flags,
-                       fstab->recs[i].fs_options);
+                     fstab->recs[i].fs_type, fstab->recs[i].flags,
+                     fstab->recs[i].fs_options);
+
         if (!mret) {
             /* Success!  Go get the next one */
             continue;
@@ -665,6 +680,13 @@ int fs_mgr_do_mount(struct fstab *fstab, char *n_name, char *n_blk_device,
                      fstab->recs[i].mount_point);
         }
 
+        if (fstab->recs[i].fs_mgr_flags & MF_VERIFY) {
+            if (fs_mgr_setup_verity(&fstab->recs[i]) < 0) {
+                ERROR("Could not set up verified partition, skipping!");
+                continue;
+            }
+        }
+
         /* Now mount it where requested */
         if (tmp_mount_point) {
             m = tmp_mount_point;
@@ -909,4 +931,3 @@ int fs_mgr_is_encryptable(struct fstab_rec *fstab)
 {
     return fstab->fs_mgr_flags & MF_CRYPT;
 }
-
diff --git a/fs_mgr/fs_mgr_priv.h b/fs_mgr/fs_mgr_priv.h
index 465f51e..f284ca6 100644
--- a/fs_mgr/fs_mgr_priv.h
+++ b/fs_mgr/fs_mgr_priv.h
@@ -71,6 +71,9 @@
 #define MF_RECOVERYONLY 0x40
 #define MF_SWAPPRIO     0x80
 #define MF_ZRAMSIZE     0x100
+#define MF_VERIFY       0x200
+
+#define DM_BUF_SIZE 4096
 
 #endif /* __CORE_FS_MGR_PRIV_H */
 
diff --git a/fs_mgr/fs_mgr_priv_verity.h b/fs_mgr/fs_mgr_priv_verity.h
new file mode 100644
index 0000000..6193784
--- /dev/null
+++ b/fs_mgr/fs_mgr_priv_verity.h
@@ -0,0 +1,17 @@
+/*
+ * 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.
+ */
+
+int fs_mgr_setup_verity(struct fstab_rec *fstab);
\ No newline at end of file
diff --git a/fs_mgr/fs_mgr_verity.c b/fs_mgr/fs_mgr_verity.c
new file mode 100644
index 0000000..969eab2
--- /dev/null
+++ b/fs_mgr/fs_mgr_verity.c
@@ -0,0 +1,410 @@
+/*
+ * 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 <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 <logwrap/logwrap.h>
+
+#include "mincrypt/rsa.h"
+#include "mincrypt/sha.h"
+#include "mincrypt/sha256.h"
+
+#include "ext4_utils.h"
+#include "ext4.h"
+
+#include "fs_mgr_priv.h"
+#include "fs_mgr_priv_verity.h"
+
+#define VERITY_METADATA_SIZE 32768
+#define VERITY_METADATA_MAGIC_NUMBER 0xb001b001
+#define VERITY_TABLE_RSA_KEY "/verity_key"
+
+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)
+{
+    int fd;
+    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;
+
+    data_device = open(blk_device, O_RDONLY);
+    if (data_device < 0) {
+        ERROR("Error opening block device (%s)", strerror(errno));
+        return -1;
+    }
+
+    if (lseek64(data_device, 1024, SEEK_SET) < 0) {
+        ERROR("Error seeking to superblock");
+        close(data_device);
+        return -1;
+    }
+
+    if (read(data_device, &sb, sizeof(sb)) != sizeof(sb)) {
+        ERROR("Error reading superblock");
+        close(data_device);
+        return -1;
+    }
+
+    ext4_parse_sb(&sb);
+    *device_size = info.len;
+
+    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;
+    FILE *device;
+    int retval = -1;
+
+    device = fopen(block_device, "r");
+    if (!device) {
+        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 (fseek(device, device_length, SEEK_SET) < 0) {
+        ERROR("Could not seek to start of verity metadata block.\n");
+        goto out;
+    }
+
+    // check the magic number
+    if (!fread(&magic_number, sizeof(int), 1, device)) {
+        ERROR("Couldn't read magic number!\n");
+        goto out;
+    }
+    if (magic_number != VERITY_METADATA_MAGIC_NUMBER) {
+        ERROR("Couldn't find verity metadata at offset %llu!\n", device_length);
+        goto out;
+    }
+
+    // check the protocol version
+    if (!fread(&protocol_version, sizeof(int), 1, device)) {
+        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 * sizeof(char));
+    if (!*signature) {
+        ERROR("Couldn't allocate memory for signature!\n");
+        goto out;
+    }
+    if (!fread(*signature, RSANUMBYTES, 1, device)) {
+        ERROR("Couldn't read signature from verity metadata!\n");
+        free(*signature);
+        goto out;
+    }
+
+    // get the size of the table
+    if (!fread(&table_length, sizeof(int), 1, device)) {
+        ERROR("Couldn't get the size of the verity table from metadata!\n");
+        free(*signature);
+        goto out;
+    }
+
+    // get the table + null terminator
+    table_length += 1;
+    *table = malloc(table_length);
+    if(!*table) {
+        ERROR("Couldn't allocate memory for verity table!\n");
+        goto out;
+    }
+    if (!fgets(*table, table_length, device)) {
+        ERROR("Couldn't read the verity table from metadata!\n");
+        free(*table);
+        free(*signature);
+        goto out;
+    }
+
+    retval = 0;
+
+out:
+    if (device)
+        fclose(device);
+    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)
+{
+    char *verity_params;
+    char *buffer = (char*) io;
+    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);
+    if (sprintf(verity_params, "%s", table) < 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;
+}
+
+int fs_mgr_setup_verity(struct fstab_rec *fstab) {
+
+    int retval = -1;
+
+    char *verity_blk_name;
+    char *verity_table;
+    char *verity_table_signature;
+
+    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;
+
+    // get the device mapper fd
+    int fd;
+    if ((fd = open("/dev/device-mapper", O_RDWR)) < 0) {
+        ERROR("Error opening device mapper (%s)", strerror(errno));
+        return retval;
+    }
+
+    // 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;
+    }
+
+    // read the verity block at the end of the block device
+    if (read_verity_metadata(fstab->blk_device,
+                                    &verity_table_signature,
+                                    &verity_table) < 0) {
+        goto out;
+    }
+
+    // verify the signature on the table
+    if (verify_table(verity_table_signature,
+                            verity_table,
+                            strlen(verity_table)) < 0) {
+        goto out;
+    }
+
+    // load the verity mapping table
+    if (load_verity_table(io, mount_point, fstab->blk_device, fd, verity_table) < 0) {
+        goto out;
+    }
+
+    // activate the device
+    if (resume_verity_table(io, mount_point, fd) < 0) {
+        goto out;
+    }
+
+    // assign the new verity block device as the block device
+    free(fstab->blk_device);
+    fstab->blk_device = verity_blk_name;
+
+    // make sure we've set everything up properly
+    if (test_access(fstab->blk_device) < 0) {
+        goto out;
+    }
+
+    retval = 0;
+
+out:
+    close(fd);
+    return retval;
+}
diff --git a/fs_mgr/include/fs_mgr.h b/fs_mgr/include/fs_mgr.h
index 110e738..384d195 100644
--- a/fs_mgr/include/fs_mgr.h
+++ b/fs_mgr/include/fs_mgr.h
@@ -17,6 +17,9 @@
 #ifndef __CORE_FS_MGR_H
 #define __CORE_FS_MGR_H
 
+#include <stdint.h>
+#include <linux/dm-ioctl.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -35,6 +38,7 @@ struct fstab_rec {
     char *fs_options;
     int fs_mgr_flags;
     char *key_loc;
+    char *verity_loc;
     long long length;
     char *label;
     int partnum;
diff --git a/init/Android.mk b/init/Android.mk
index ef62bce..abfc68a 100644
--- a/init/Android.mk
+++ b/init/Android.mk
@@ -39,7 +39,9 @@ LOCAL_STATIC_LIBRARIES := \
 	libcutils \
 	liblog \
 	libc \
-	libselinux
+	libselinux \
+	libmincrypt \
+	libext4_utils_static
 
 include $(BUILD_EXECUTABLE)