blob: 36ce3bed29bd93c2acccd24292e6af8a886a0383 [file] [log] [blame] [edit]
/*
* Copyright (C) 2015 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 "rpmb.h"
#include "error_reporting.h"
#include "rpmb_protocol.h"
#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <lk/compiler.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/hmac.h>
#include <openssl/mem.h>
#include <openssl/rand.h>
#define RPMB_DEBUG 0
#define MAX_PACKET_COUNT 2
#define RPMB_PROTOCOL_MMC 1
#define RPMB_PROTOCOL_UFS 2
#define RPMB_READ_COUNTER_MAX_RETRIES 3
#if RPMB_PROTOCOL != RPMB_PROTOCOL_MMC && RPMB_PROTOCOL != RPMB_PROTOCOL_UFS
#error "invalid RPMB_PROTOCOL!"
#endif
struct rpmb_state {
struct rpmb_key key;
void* mmc_handle;
uint32_t write_counter;
bool first_write_complete;
bool verify_failed;
};
#if RPMB_DEBUG
#define rpmb_dprintf(fmt, ...) fprintf(stderr, fmt, ##__VA_ARGS__)
#else
#define rpmb_dprintf(fmt, ...) \
do { \
} while (0)
#endif
static void rpmb_dprint_buf(const char* prefix,
const uint8_t* buf,
size_t size) {
#if RPMB_DEBUG
size_t i, j;
rpmb_dprintf("%s", prefix);
for (i = 0; i < size; i++) {
if (i && i % 32 == 0) {
rpmb_dprintf("\n");
j = strlen(prefix);
while (j--)
rpmb_dprintf(" ");
}
rpmb_dprintf(" %02x", buf[i]);
}
rpmb_dprintf("\n");
#endif
}
static void rpmb_dprint_u16(const char* prefix, const struct rpmb_u16 u16) {
rpmb_dprint_buf(prefix, u16.byte, sizeof(u16.byte));
}
static void rpmb_dprint_u32(const char* prefix, const struct rpmb_u32 u32) {
rpmb_dprint_buf(prefix, u32.byte, sizeof(u32.byte));
}
static void rpmb_dprint_key(const char* prefix,
const struct rpmb_key key,
const char* expected_prefix,
const struct rpmb_key expected_key) {
#if RPMB_DEBUG
rpmb_dprint_buf(prefix, key.byte, sizeof(key.byte));
if (CRYPTO_memcmp(key.byte, expected_key.byte, sizeof(key.byte)))
rpmb_dprint_buf(expected_prefix, expected_key.byte,
sizeof(expected_key.byte));
#endif
}
static struct rpmb_nonce rpmb_nonce_init(void) {
struct rpmb_nonce rpmb_nonce;
RAND_bytes(rpmb_nonce.byte, sizeof(rpmb_nonce.byte));
return rpmb_nonce;
}
static int rpmb_mac(struct rpmb_key key,
struct rpmb_packet* packet,
size_t packet_count,
struct rpmb_key* mac) {
size_t i;
int hmac_ret;
unsigned int md_len;
HMAC_CTX hmac_ctx;
HMAC_CTX_init(&hmac_ctx);
hmac_ret = HMAC_Init_ex(&hmac_ctx, &key, sizeof(key), EVP_sha256(), NULL);
if (!hmac_ret) {
fprintf(stderr, "HMAC_Init_ex failed\n");
goto err;
}
for (i = 0; i < packet_count; i++) {
STATIC_ASSERT(sizeof(*packet) - offsetof(__typeof__(*packet), data) ==
284);
hmac_ret = HMAC_Update(&hmac_ctx, packet[i].data, 284);
if (!hmac_ret) {
fprintf(stderr, "HMAC_Update failed\n");
goto err;
}
}
hmac_ret = HMAC_Final(&hmac_ctx, mac->byte, &md_len);
if (md_len != sizeof(mac->byte)) {
fprintf(stderr, "bad md_len %d != %zd\n", md_len, sizeof(mac->byte));
exit(1);
}
if (!hmac_ret) {
fprintf(stderr, "HMAC_Final failed\n");
goto err;
}
err:
HMAC_CTX_cleanup(&hmac_ctx);
return hmac_ret ? 0 : -1;
}
static int rpmb_check_response(const char* cmd_str,
enum rpmb_response response_type,
struct rpmb_packet* res,
int res_count,
struct rpmb_key* mac,
struct rpmb_nonce* nonce,
uint16_t* addrp,
uint32_t write_counter) {
int i;
for (i = 0; i < res_count; i++) {
if (rpmb_get_u16(res[i].req_resp) != response_type) {
fprintf(stderr, "%s: Bad response type, 0x%x, expected 0x%x\n",
cmd_str, rpmb_get_u16(res[i].req_resp), response_type);
return -1;
}
if (rpmb_get_u16(res[i].result) != RPMB_RES_OK) {
if (rpmb_get_u16(res[i].result) == RPMB_RES_ADDR_FAILURE) {
fprintf(stderr, "%s: Addr failure, %u\n", cmd_str,
rpmb_get_u16(res[i].address));
return -ENOENT;
}
fprintf(stderr, "%s: Bad result, 0x%x\n", cmd_str,
rpmb_get_u16(res[i].result));
return -1;
}
if (i == res_count - 1 && mac &&
CRYPTO_memcmp(res[i].key_mac.byte, mac->byte, sizeof(mac->byte))) {
fprintf(stderr, "%s: Bad MAC\n", cmd_str);
error_report_rpmb_mac_mismatch();
return -1;
}
if (nonce && CRYPTO_memcmp(res[i].nonce.byte, nonce->byte,
sizeof(nonce->byte))) {
fprintf(stderr, "%s: Bad nonce\n", cmd_str);
return -1;
}
if (write_counter &&
write_counter != rpmb_get_u32(res[i].write_counter)) {
fprintf(stderr, "%s: Bad write counter, got %u, expected %u\n",
cmd_str, rpmb_get_u32(res[i].write_counter), write_counter);
error_report_rpmb_counter_mismatch();
return -1;
}
if (addrp && *addrp != rpmb_get_u16(res[i].address)) {
fprintf(stderr, "%s: Bad addr, got %u, expected %u\n", cmd_str,
rpmb_get_u16(res[i].address), *addrp);
error_report_rpmb_addr_mismatch();
return -1;
}
}
return 0;
}
int rpmb_program_key(struct rpmb_state* state, const struct rpmb_key* key) {
int ret;
struct rpmb_packet cmd = {
.req_resp = rpmb_u16(RPMB_REQ_PROGRAM_KEY),
};
struct rpmb_packet rescmd = {
.req_resp = rpmb_u16(RPMB_REQ_RESULT_READ),
};
struct rpmb_packet res;
memcpy(cmd.key_mac.byte, key->byte, sizeof(cmd.key_mac.byte));
ret = rpmb_send(state->mmc_handle, &cmd, sizeof(cmd), &rescmd,
sizeof(rescmd), &res, sizeof(res), false, false);
if (ret < 0)
return ret;
rpmb_dprint_key(" key/mac ", res.key_mac, " expected mac ",
res.key_mac);
rpmb_dprint_buf(" nonce ", res.nonce.byte, sizeof(res.nonce.byte));
rpmb_dprint_u32(" write_counter ", res.write_counter);
rpmb_dprint_u16(" result ", res.result);
rpmb_dprint_u16(" req/resp ", res.req_resp);
ret = rpmb_check_response("program key", RPMB_RESP_PROGRAM_KEY, &res, 1,
NULL, NULL, NULL, 0);
return ret;
}
static int rpmb_read_counter(struct rpmb_state* state,
uint32_t* write_counter) {
int ret;
struct rpmb_key mac;
struct rpmb_nonce nonce = rpmb_nonce_init();
struct rpmb_packet cmd = {
.nonce = nonce,
.req_resp = rpmb_u16(RPMB_REQ_GET_COUNTER),
};
struct rpmb_packet res;
ret = rpmb_send(state->mmc_handle, NULL, 0, &cmd, sizeof(cmd), &res,
sizeof(res), false, false);
if (ret < 0)
return ret;
ret = rpmb_mac(state->key, &res, 1, &mac);
if (ret < 0)
return ret;
rpmb_dprintf("rpmb: read counter response:\n");
rpmb_dprint_key(" key/mac ", res.key_mac, " expected mac ", mac);
rpmb_dprint_buf(" nonce ", res.nonce.byte, sizeof(res.nonce.byte));
rpmb_dprint_u32(" write_counter ", res.write_counter);
rpmb_dprint_u16(" result ", res.result);
rpmb_dprint_u16(" req/resp ", res.req_resp);
ret = rpmb_check_response("read counter", RPMB_RESP_GET_COUNTER, &res, 1,
&mac, &nonce, NULL, 0);
if (ret < 0)
return ret;
if (write_counter)
*write_counter = rpmb_get_u32(res.write_counter);
return 0;
}
static int rpmb_read_counter_retry(struct rpmb_state* state,
uint32_t* write_counter) {
int retries;
int ret = 0;
for (retries = 0; retries < RPMB_READ_COUNTER_MAX_RETRIES; retries++) {
ret = rpmb_read_counter(state, write_counter);
if (ret >= 0) {
return ret;
}
}
/* Return the last error */
error_report_rpmb_counter_read_failure();
return ret;
}
static int rpmb_read_data(struct rpmb_state* state,
const void* cmp_buf,
void* out_buf,
uint16_t addr,
uint16_t count,
struct rpmb_key* mac) {
int i;
int ret;
struct rpmb_nonce nonce = rpmb_nonce_init();
struct rpmb_packet cmd = {
.nonce = nonce,
.address = rpmb_u16(addr),
#if RPMB_PROTOCOL == RPMB_PROTOCOL_UFS
.block_count = rpmb_u16(count),
#endif
.req_resp = rpmb_u16(RPMB_REQ_DATA_READ),
};
struct rpmb_packet res[MAX_PACKET_COUNT];
const uint8_t* cmp_bufp;
uint8_t* out_bufp;
assert(count <= MAX_PACKET_COUNT);
if (!state)
return -EINVAL;
if (state->verify_failed)
return -EIO;
ret = rpmb_send(state->mmc_handle, NULL, 0, &cmd, sizeof(cmd), res,
sizeof(res[0]) * count, false, false);
if (ret < 0)
return ret;
if (mac) {
ret = rpmb_mac(state->key, res, count, mac);
if (ret < 0)
return ret;
}
rpmb_dprintf("rpmb: read data, addr %d, count %d, response:\n", addr,
count);
for (i = 0; i < count; i++) {
rpmb_dprintf(" block %d\n", i);
if (i == count - 1 && mac)
rpmb_dprint_key(" key/mac ", res[i].key_mac,
" expected mac ", *mac);
rpmb_dprint_buf(" data ", res[i].data, sizeof(res[i].data));
rpmb_dprint_buf(" nonce ", res[i].nonce.byte,
sizeof(res[i].nonce.byte));
rpmb_dprint_u16(" address ", res[i].address);
rpmb_dprint_u16(" block_count ", res[i].block_count);
rpmb_dprint_u16(" result ", res[i].result);
rpmb_dprint_u16(" req/resp ", res[i].req_resp);
}
ret = rpmb_check_response("read data", RPMB_RESP_DATA_READ, res, count, mac,
&nonce, &addr, 0);
if (ret < 0)
return ret;
if (cmp_buf) {
for (cmp_bufp = cmp_buf, i = 0; i < count;
i++, cmp_bufp += sizeof(res[i].data)) {
if (memcmp(cmp_bufp, res[i].data, sizeof(res[i].data))) {
fprintf(stderr, "verify read: data compare failed\n");
return -1;
}
}
}
if (out_buf) {
for (out_bufp = out_buf, i = 0; i < count;
i++, out_bufp += sizeof(res[i].data)) {
memcpy(out_bufp, res[i].data, sizeof(res[i].data));
}
}
return 0;
}
int rpmb_read(struct rpmb_state* state,
void* buf,
uint16_t addr,
uint16_t count) {
struct rpmb_key mac;
return rpmb_read_data(state, NULL, buf, addr, count, &mac);
}
int rpmb_read_no_mac(struct rpmb_state* state,
void* buf,
uint16_t addr,
uint16_t count) {
return rpmb_read_data(state, NULL, buf, addr, count, NULL);
}
int rpmb_verify(struct rpmb_state* state,
const void* buf,
uint16_t addr,
uint16_t count) {
struct rpmb_key mac;
return rpmb_read_data(state, buf, NULL, addr, count, &mac);
}
/**
* check_write_counter() - Check that the write counter matches
* @expected_write_counter
* @state: Current RPMB state
* @expected_write_counter: Write counter we expect
*
* Return: %true if the write counter is confirmed to be
* @expected_write_counter
*/
static bool check_write_counter(struct rpmb_state* state,
uint32_t expected_write_counter) {
/*
* Query the RPMB chip for the current write counter. Although there was
* some sort of exceptional condition, we don't actually know if a
* write went through and therefore the counter was incremented.
*/
int ret;
uint32_t new_write_counter = 0;
ret = rpmb_read_counter_retry(state, &new_write_counter);
if (ret == 0) {
if (new_write_counter == expected_write_counter) {
return true;
} else {
fprintf(stderr,
"%s: Could not resync write counter. "
"expected write counter: %u, queried write counter: %u\n",
__func__, expected_write_counter, new_write_counter);
}
} else {
fprintf(stderr, "%s: rpmb_read_counter failed: %d\n", __func__, ret);
}
return false;
}
static int rpmb_write_data(struct rpmb_state* state,
const char* buf,
uint16_t addr,
uint16_t count,
bool sync,
bool sync_checkpoint) {
int i;
int ret;
struct rpmb_key mac;
struct rpmb_packet cmd[MAX_PACKET_COUNT];
struct rpmb_packet rescmd = {
.req_resp = rpmb_u16(RPMB_REQ_RESULT_READ),
};
struct rpmb_packet res;
assert(count <= MAX_PACKET_COUNT);
rpmb_dprintf("rpmb: write data, addr %d, count %d\n", addr, count);
for (i = 0; i < count; i++) {
memset(&cmd[i], 0, sizeof(cmd[i]));
memcpy(cmd[i].data, buf + i * sizeof(cmd[i].data), sizeof(cmd[i].data));
rpmb_dprint_buf(" data ", cmd[i].data, sizeof(cmd[i].data));
cmd[i].write_counter = rpmb_u32(state->write_counter);
cmd[i].address = rpmb_u16(addr);
cmd[i].block_count = rpmb_u16(count);
cmd[i].req_resp = rpmb_u16(RPMB_REQ_DATA_WRITE);
}
ret = rpmb_mac(state->key, cmd, count, &cmd[count - 1].key_mac);
if (ret < 0) {
fprintf(stderr, "rpmb command mac failed\n");
return ret;
}
ret = rpmb_send(state->mmc_handle, cmd, sizeof(cmd[0]) * count, &rescmd,
sizeof(rescmd), &res, sizeof(res), sync, sync_checkpoint);
if (ret < 0) {
fprintf(stderr, "rpmb send failed: %d, result: %hu\n", ret,
rpmb_get_u16(res.result));
goto err_sent;
}
ret = rpmb_mac(state->key, &res, 1, &mac);
if (ret < 0) {
fprintf(stderr, "rpmb response mac failed\n");
goto err_sent;
}
rpmb_dprintf(
"rpmb: write data, addr %d, count %d, write_counter %d, response\n",
addr, count, state->write_counter);
rpmb_dprint_key(" key/mac ", res.key_mac, " expected mac ", mac);
rpmb_dprint_buf(" nonce ", res.nonce.byte, sizeof(res.nonce.byte));
rpmb_dprint_u32(" write_counter ", res.write_counter);
rpmb_dprint_u16(" address ", res.address);
rpmb_dprint_u16(" result ", res.result);
rpmb_dprint_u16(" req/resp ", res.req_resp);
ret = rpmb_check_response("write data", RPMB_RESP_DATA_WRITE, &res, 1, &mac,
NULL, &addr, state->write_counter + 1);
if (ret < 0) {
fprintf(stderr, "rpmb_check_response_failed: %d, result: %hu\n", ret,
rpmb_get_u16(res.result));
if (check_write_counter(state, state->write_counter + 1)) {
state->write_counter++;
fprintf(stderr,
"Write was committed with failed response. New write counter: %u\n",
state->write_counter);
error_report_rpmb_counter_mismatch_recovered();
/*
* Indicate to block device that the FS state is unknown and a clean
* superblock must be written.
*/
ret = -EUCLEAN;
}
goto err_sent;
}
state->write_counter++;
return 0;
err_sent:
/*
* An error occurred after the write request was sent. An attacker might
* have saved this write request and might send it to the rpmb device at
* any time. Any other write with this write counter value now needs extra
* checks to make sure there is no corruption.
*
* 1. The next write fails.
*
* 1.1. The failure is a count failure.
* A write operation that was previously reported as an error must have
* actually been written. The filesystem may now be in a state where is it
* not safe to write any other block. The write that actually went through
* may have been from a previous write attempt, so we don't know the current
* state.
*
* We pass BLOCK_WRITE_FAILED_UNKNOWN_STATE to block_cache_complete_write()
* in this case which causes the block device to queue writes of all
* filesystem superblocks before doing any new writes.
*
* 1.1.1. The block actually written was a super-block.
* This means a transaction was committed to disk that the file-system code
* thought was aborted. The in-memory view of free blocks will not match the
* on disk state. It is not safe to proceed with any other write operations
* in this state as the file-system could pick a block to write to that is
* not actually free until the super block gets updated again with the
* in-memory state.
*
* We mitigate this case by immediately rewriting a new, valid super-block
* with the current in-memory (i.e. not including the current, failing
* transaction) state when a super-block write fails. If this second write
* fails, we are left with a failed transaction in fs->inital_super_block_tr
* and all future writes to this filesystem will fail. If it succeeds we
* validate the write in 2.1 below. If the device reboots before completing
* the second super-block write attempt, a malicious host can replay this
* block on a later boot. In the case of TD filesystems, this can cause
* detectable filesystem corruption as data blocks may not match the
* super-block now, however, that is allowed. For TP filesystems, the next
* data write will be validated as it is the first RPMB write after boot,
* and if it fails we abort the service (2.1.1), forcing a reboot and
* re-initializing the filesystem state from the now committed super-block.
*
* It's worth noting that in this case, we may have sent a failed response
* to a client for a transaction that was eventually committed.
*
* 1.1.2. The block actually written was a data block.
*
* The write must have been to a block that was free, and the transaction
* that block was part of could never have been committed. We don't actually
* care about this write, but we rewrite the superblock as described in
* 1.1.1. because we can't know what was written.
*
* 1.2. The failure is not reported as count failure.
* This can be handled the same way as the inital failure. We now have one
* more possible write request that can be saved and written at any time by
* an attacker, but it is in the same class as before.
*
* 2. The next write succeeds.
*
* 2.1. The same block number and counter value has already been sent.
* This success status cannot be trusted. We read back the data to verify.
* 2.1.1. Verify failed.
* This has the same effect as 1.1. We currently block all further
* read/write operations after this point (until reboot or FS re-mount)
* because it is not safe to recover from this state in a TP filesystem.
*
* 2.1.2. Verify passed.
* We are back to a normal state.
*
* 2.2. The same block number and counter has not already been sent.
* We are back to a normal state.
*/
fprintf(stderr, "rpmb: write failed for write counter %u\n",
state->write_counter);
state->first_write_complete = false;
return ret;
}
int rpmb_write(struct rpmb_state* state,
const void* buf,
uint16_t addr,
uint16_t count,
bool sync,
bool sync_checkpoint) {
int ret;
if (!state)
return -EINVAL;
if (state->verify_failed)
return -EIO;
ret = rpmb_write_data(state, buf, addr, count, sync, sync_checkpoint);
if (ret < 0)
return ret;
if (!state->first_write_complete) {
/*
* The first write request after reading the write counter could get a
* signed response from a different write request. There is no nonce in
* the write request, only a write counter. The response could be from
* another valid write request we generated on a previous boot that was
* not completed. Read back the data and verify that the correct data
* was written for this case. Note that this only works if we never
* send more than one write request to the non-secure proxy at once. If
* we later add support for pipelining rpmb operation we need to verify
* the first n write requests here instead, where n is the max pipeline
* depth of any build that may have run on the same device. We would
* also need ensure that a superblock write request is not sent until
* all other write requests have been validated and that an attacker
* cannot have any saved write requests to the same filesystem with a
* larger write-counter value than the superblock update (e.g. by
* repeating a non-superblock write request until only one write
* operation remains to be verified).
*/
ret = rpmb_verify(state, buf, addr, count);
if (ret < 0) {
fprintf(stderr,
"rpmb write verify failure: %d, addr: %hu, count: %hu\n",
ret, addr, count);
state->verify_failed = true;
return ret;
}
state->first_write_complete = true;
}
return 0;
}
void rpmb_set_key(struct rpmb_state* state, const struct rpmb_key* key) {
assert(state);
state->key = *key;
/*
* We need to read the counter before reading the super blocks. If an
* attacker writes to a super block after we read it, but before we read the
* write counter, or next write would succeed without us detecting that the
* in-memory super block does not match the on-disk state.
*
* We retry reading the write counter several times because
* we occasionally get an incorrect response
*/
int ret;
ret = rpmb_read_counter_retry(state, &state->write_counter);
if (ret < 0) {
fprintf(stderr, "failed to read rpmb write counter\n");
/*
* Ignore errors. Any future write will fail since we initialized the
* write_counter with the value where it expires.
*/
}
}
int rpmb_init(struct rpmb_state** statep, void* mmc_handle) {
struct rpmb_state* state = malloc(sizeof(*state));
if (!state)
return -ENOMEM;
state->mmc_handle = mmc_handle;
state->write_counter = RPMB_WRITE_COUNTER_EXPIRED_VALUE;
/*
* We don't know if the last write before reboot completed successfully.
* There may be writes for the current write counter that can be replayed at
* this point, so we need to validate our next write.
*/
state->first_write_complete = false;
state->verify_failed = false;
*statep = state;
return 0;
}
void rpmb_uninit(struct rpmb_state* statep) {
free(statep);
}