u-boot/lib/rsa/rsa-verify.c
Philippe Reynes b02f2e79c6 rsa: check that pointer checksum isn't NULL before using it
The pointer checksum were used before checking that it
isn't NULL. We move the code that use it after the check.

Reported-by: Coverity (CID: 185835)
Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2019-03-25 11:44:12 -04:00

464 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (c) 2013, Google Inc.
*/
#ifndef USE_HOSTCC
#include <common.h>
#include <fdtdec.h>
#include <asm/types.h>
#include <asm/byteorder.h>
#include <linux/errno.h>
#include <asm/types.h>
#include <asm/unaligned.h>
#include <dm.h>
#else
#include "fdt_host.h"
#include "mkimage.h"
#include <fdt_support.h>
#endif
#include <u-boot/rsa-mod-exp.h>
#include <u-boot/rsa.h>
/* Default public exponent for backward compatibility */
#define RSA_DEFAULT_PUBEXP 65537
/**
* rsa_verify_padding() - Verify RSA message padding is valid
*
* Verify a RSA message's padding is consistent with PKCS1.5
* padding as described in the RSA PKCS#1 v2.1 standard.
*
* @msg: Padded message
* @pad_len: Number of expected padding bytes
* @algo: Checksum algo structure having information on DER encoding etc.
* @return 0 on success, != 0 on failure
*/
static int rsa_verify_padding(const uint8_t *msg, const int pad_len,
struct checksum_algo *algo)
{
int ff_len;
int ret;
/* first byte must be 0x00 */
ret = *msg++;
/* second byte must be 0x01 */
ret |= *msg++ ^ 0x01;
/* next ff_len bytes must be 0xff */
ff_len = pad_len - algo->der_len - 3;
ret |= *msg ^ 0xff;
ret |= memcmp(msg, msg+1, ff_len-1);
msg += ff_len;
/* next byte must be 0x00 */
ret |= *msg++;
/* next der_len bytes must match der_prefix */
ret |= memcmp(msg, algo->der_prefix, algo->der_len);
return ret;
}
int padding_pkcs_15_verify(struct image_sign_info *info,
uint8_t *msg, int msg_len,
const uint8_t *hash, int hash_len)
{
struct checksum_algo *checksum = info->checksum;
int ret, pad_len = msg_len - checksum->checksum_len;
/* Check pkcs1.5 padding bytes. */
ret = rsa_verify_padding(msg, pad_len, checksum);
if (ret) {
debug("In RSAVerify(): Padding check failed!\n");
return -EINVAL;
}
/* Check hash. */
if (memcmp((uint8_t *)msg + pad_len, hash, msg_len - pad_len)) {
debug("In RSAVerify(): Hash check failed!\n");
return -EACCES;
}
return 0;
}
#ifdef CONFIG_FIT_ENABLE_RSASSA_PSS_SUPPORT
static void u32_i2osp(uint32_t val, uint8_t *buf)
{
buf[0] = (uint8_t)((val >> 24) & 0xff);
buf[1] = (uint8_t)((val >> 16) & 0xff);
buf[2] = (uint8_t)((val >> 8) & 0xff);
buf[3] = (uint8_t)((val >> 0) & 0xff);
}
/**
* mask_generation_function1() - generate an octet string
*
* Generate an octet string used to check rsa signature.
* It use an input octet string and a hash function.
*
* @checksum: A Hash function
* @seed: Specifies an input variable octet string
* @seed_len: Size of the input octet string
* @output: Specifies the output octet string
* @output_len: Size of the output octet string
* @return 0 if the octet string was correctly generated, others on error
*/
static int mask_generation_function1(struct checksum_algo *checksum,
uint8_t *seed, int seed_len,
uint8_t *output, int output_len)
{
struct image_region region[2];
int ret = 0, i, i_output = 0, region_count = 2;
uint32_t counter = 0;
uint8_t buf_counter[4], *tmp;
int hash_len = checksum->checksum_len;
memset(output, 0, output_len);
region[0].data = seed;
region[0].size = seed_len;
region[1].data = &buf_counter[0];
region[1].size = 4;
tmp = malloc(hash_len);
if (!tmp) {
debug("%s: can't allocate array tmp\n", __func__);
ret = -ENOMEM;
goto out;
}
while (i_output < output_len) {
u32_i2osp(counter, &buf_counter[0]);
ret = checksum->calculate(checksum->name,
region, region_count,
tmp);
if (ret < 0) {
debug("%s: Error in checksum calculation\n", __func__);
goto out;
}
i = 0;
while ((i_output < output_len) && (i < hash_len)) {
output[i_output] = tmp[i];
i_output++;
i++;
}
counter++;
}
out:
free(tmp);
return ret;
}
static int compute_hash_prime(struct checksum_algo *checksum,
uint8_t *pad, int pad_len,
uint8_t *hash, int hash_len,
uint8_t *salt, int salt_len,
uint8_t *hprime)
{
struct image_region region[3];
int ret, region_count = 3;
region[0].data = pad;
region[0].size = pad_len;
region[1].data = hash;
region[1].size = hash_len;
region[2].data = salt;
region[2].size = salt_len;
ret = checksum->calculate(checksum->name, region, region_count, hprime);
if (ret < 0) {
debug("%s: Error in checksum calculation\n", __func__);
goto out;
}
out:
return ret;
}
int padding_pss_verify(struct image_sign_info *info,
uint8_t *msg, int msg_len,
const uint8_t *hash, int hash_len)
{
uint8_t *masked_db = NULL;
int masked_db_len = msg_len - hash_len - 1;
uint8_t *h = NULL, *hprime = NULL;
int h_len = hash_len;
uint8_t *db_mask = NULL;
int db_mask_len = masked_db_len;
uint8_t *db = NULL, *salt = NULL;
int db_len = masked_db_len, salt_len = msg_len - hash_len - 2;
uint8_t pad_zero[8] = { 0 };
int ret, i, leftmost_bits = 1;
uint8_t leftmost_mask;
struct checksum_algo *checksum = info->checksum;
/* first, allocate everything */
masked_db = malloc(masked_db_len);
h = malloc(h_len);
db_mask = malloc(db_mask_len);
db = malloc(db_len);
salt = malloc(salt_len);
hprime = malloc(hash_len);
if (!masked_db || !h || !db_mask || !db || !salt || !hprime) {
printf("%s: can't allocate some buffer\n", __func__);
ret = -ENOMEM;
goto out;
}
/* step 4: check if the last byte is 0xbc */
if (msg[msg_len - 1] != 0xbc) {
printf("%s: invalid pss padding (0xbc is missing)\n", __func__);
ret = -EINVAL;
goto out;
}
/* step 5 */
memcpy(masked_db, msg, masked_db_len);
memcpy(h, msg + masked_db_len, h_len);
/* step 6 */
leftmost_mask = (0xff >> (8 - leftmost_bits)) << (8 - leftmost_bits);
if (masked_db[0] & leftmost_mask) {
printf("%s: invalid pss padding ", __func__);
printf("(leftmost bit of maskedDB not zero)\n");
ret = -EINVAL;
goto out;
}
/* step 7 */
mask_generation_function1(checksum, h, h_len, db_mask, db_mask_len);
/* step 8 */
for (i = 0; i < db_len; i++)
db[i] = masked_db[i] ^ db_mask[i];
/* step 9 */
db[0] &= 0xff >> leftmost_bits;
/* step 10 */
if (db[0] != 0x01) {
printf("%s: invalid pss padding ", __func__);
printf("(leftmost byte of db isn't 0x01)\n");
ret = EINVAL;
goto out;
}
/* step 11 */
memcpy(salt, &db[1], salt_len);
/* step 12 & 13 */
compute_hash_prime(checksum, pad_zero, 8,
(uint8_t *)hash, hash_len,
salt, salt_len, hprime);
/* step 14 */
ret = memcmp(h, hprime, hash_len);
out:
free(hprime);
free(salt);
free(db);
free(db_mask);
free(h);
free(masked_db);
return ret;
}
#endif
/**
* rsa_verify_key() - Verify a signature against some data using RSA Key
*
* Verify a RSA PKCS1.5 signature against an expected hash using
* the RSA Key properties in prop structure.
*
* @info: Specifies key and FIT information
* @prop: Specifies key
* @sig: Signature
* @sig_len: Number of bytes in signature
* @hash: Pointer to the expected hash
* @key_len: Number of bytes in rsa key
* @return 0 if verified, -ve on error
*/
static int rsa_verify_key(struct image_sign_info *info,
struct key_prop *prop, const uint8_t *sig,
const uint32_t sig_len, const uint8_t *hash,
const uint32_t key_len)
{
int ret;
#if !defined(USE_HOSTCC)
struct udevice *mod_exp_dev;
#endif
struct checksum_algo *checksum = info->checksum;
struct padding_algo *padding = info->padding;
int hash_len;
if (!prop || !sig || !hash || !checksum)
return -EIO;
if (sig_len != (prop->num_bits / 8)) {
debug("Signature is of incorrect length %d\n", sig_len);
return -EINVAL;
}
debug("Checksum algorithm: %s", checksum->name);
/* Sanity check for stack size */
if (sig_len > RSA_MAX_SIG_BITS / 8) {
debug("Signature length %u exceeds maximum %d\n", sig_len,
RSA_MAX_SIG_BITS / 8);
return -EINVAL;
}
uint8_t buf[sig_len];
hash_len = checksum->checksum_len;
#if !defined(USE_HOSTCC)
ret = uclass_get_device(UCLASS_MOD_EXP, 0, &mod_exp_dev);
if (ret) {
printf("RSA: Can't find Modular Exp implementation\n");
return -EINVAL;
}
ret = rsa_mod_exp(mod_exp_dev, sig, sig_len, prop, buf);
#else
ret = rsa_mod_exp_sw(sig, sig_len, prop, buf);
#endif
if (ret) {
debug("Error in Modular exponentation\n");
return ret;
}
ret = padding->verify(info, buf, key_len, hash, hash_len);
if (ret) {
debug("In RSAVerify(): padding check failed!\n");
return ret;
}
return 0;
}
/**
* rsa_verify_with_keynode() - Verify a signature against some data using
* information in node with prperties of RSA Key like modulus, exponent etc.
*
* Parse sign-node and fill a key_prop structure with properties of the
* key. Verify a RSA PKCS1.5 signature against an expected hash using
* the properties parsed
*
* @info: Specifies key and FIT information
* @hash: Pointer to the expected hash
* @sig: Signature
* @sig_len: Number of bytes in signature
* @node: Node having the RSA Key properties
* @return 0 if verified, -ve on error
*/
static int rsa_verify_with_keynode(struct image_sign_info *info,
const void *hash, uint8_t *sig,
uint sig_len, int node)
{
const void *blob = info->fdt_blob;
struct key_prop prop;
int length;
int ret = 0;
if (node < 0) {
debug("%s: Skipping invalid node", __func__);
return -EBADF;
}
prop.num_bits = fdtdec_get_int(blob, node, "rsa,num-bits", 0);
prop.n0inv = fdtdec_get_int(blob, node, "rsa,n0-inverse", 0);
prop.public_exponent = fdt_getprop(blob, node, "rsa,exponent", &length);
if (!prop.public_exponent || length < sizeof(uint64_t))
prop.public_exponent = NULL;
prop.exp_len = sizeof(uint64_t);
prop.modulus = fdt_getprop(blob, node, "rsa,modulus", NULL);
prop.rr = fdt_getprop(blob, node, "rsa,r-squared", NULL);
if (!prop.num_bits || !prop.modulus) {
debug("%s: Missing RSA key info", __func__);
return -EFAULT;
}
ret = rsa_verify_key(info, &prop, sig, sig_len, hash,
info->crypto->key_len);
return ret;
}
int rsa_verify(struct image_sign_info *info,
const struct image_region region[], int region_count,
uint8_t *sig, uint sig_len)
{
const void *blob = info->fdt_blob;
/* Reserve memory for maximum checksum-length */
uint8_t hash[info->crypto->key_len];
int ndepth, noffset;
int sig_node, node;
char name[100];
int ret;
/*
* Verify that the checksum-length does not exceed the
* rsa-signature-length
*/
if (info->checksum->checksum_len >
info->crypto->key_len) {
debug("%s: invlaid checksum-algorithm %s for %s\n",
__func__, info->checksum->name, info->crypto->name);
return -EINVAL;
}
sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
if (sig_node < 0) {
debug("%s: No signature node found\n", __func__);
return -ENOENT;
}
/* Calculate checksum with checksum-algorithm */
ret = info->checksum->calculate(info->checksum->name,
region, region_count, hash);
if (ret < 0) {
debug("%s: Error in checksum calculation\n", __func__);
return -EINVAL;
}
/* See if we must use a particular key */
if (info->required_keynode != -1) {
ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
info->required_keynode);
if (!ret)
return ret;
}
/* Look for a key that matches our hint */
snprintf(name, sizeof(name), "key-%s", info->keyname);
node = fdt_subnode_offset(blob, sig_node, name);
ret = rsa_verify_with_keynode(info, hash, sig, sig_len, node);
if (!ret)
return ret;
/* No luck, so try each of the keys in turn */
for (ndepth = 0, noffset = fdt_next_node(info->fit, sig_node, &ndepth);
(noffset >= 0) && (ndepth > 0);
noffset = fdt_next_node(info->fit, noffset, &ndepth)) {
if (ndepth == 1 && noffset != node) {
ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
noffset);
if (!ret)
break;
}
}
return ret;
}