u-boot/lib/rsa/rsa-verify.c

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// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (c) 2013, Google Inc.
*/
#ifndef USE_HOSTCC
#include <common.h>
#include <fdtdec.h>
#include <malloc.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 <linux/kconfig.h>
#include <u-boot/rsa-mod-exp.h>
#include <u-boot/rsa.h>
#ifndef __UBOOT__
/*
* NOTE:
* Since host tools, like mkimage, make use of openssl library for
* RSA encryption, rsa_verify_with_pkey()/rsa_gen_key_prop() are
* of no use and should not be compiled in.
* So just turn off CONFIG_RSA_VERIFY_WITH_PKEY.
*/
#undef CONFIG_RSA_VERIFY_WITH_PKEY
#endif
/* 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
#if CONFIG_IS_ENABLED(FIT_SIGNATURE) || IS_ENABLED(CONFIG_RSA_VERIFY_WITH_PKEY)
/**
* 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;
}
#endif
#ifdef CONFIG_RSA_VERIFY_WITH_PKEY
/**
* rsa_verify_with_pkey() - Verify a signature against some data using
* only modulus and exponent as RSA key properties.
* @info: Specifies key information
* @hash: Pointer to the expected hash
* @sig: Signature
* @sig_len: Number of bytes in signature
*
* Parse a RSA public key blob in DER format pointed to in @info and fill
* a key_prop structure with properties of the key. Then verify a RSA PKCS1.5
* signature against an expected hash using the calculated properties.
*
* Return 0 if verified, -ve on error
*/
static int rsa_verify_with_pkey(struct image_sign_info *info,
const void *hash, uint8_t *sig, uint sig_len)
{
struct key_prop *prop;
int ret;
/* Public key is self-described to fill key_prop */
ret = rsa_gen_key_prop(info->key, info->keylen, &prop);
if (ret) {
debug("Generating necessary parameter for decoding failed\n");
return ret;
}
ret = rsa_verify_key(info, prop, sig, sig_len, hash,
info->crypto->key_len);
rsa_free_key_prop(prop);
return ret;
}
#else
static int rsa_verify_with_pkey(struct image_sign_info *info,
const void *hash, uint8_t *sig, uint sig_len)
{
return -EACCES;
}
#endif
#if CONFIG_IS_ENABLED(FIT_SIGNATURE)
/**
* 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;
}
#else
static int rsa_verify_with_keynode(struct image_sign_info *info,
const void *hash, uint8_t *sig,
uint sig_len, int node)
{
return -EACCES;
}
#endif
int rsa_verify(struct image_sign_info *info,
const struct image_region region[], int region_count,
uint8_t *sig, uint sig_len)
{
/* Reserve memory for maximum checksum-length */
uint8_t hash[info->crypto->key_len];
int ret = -EACCES;
/*
* 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;
}
/* 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;
}
if (IS_ENABLED(CONFIG_RSA_VERIFY_WITH_PKEY) && !info->fdt_blob) {
/* don't rely on fdt properties */
ret = rsa_verify_with_pkey(info, hash, sig, sig_len);
return ret;
}
if (CONFIG_IS_ENABLED(FIT_SIGNATURE)) {
const void *blob = info->fdt_blob;
int ndepth, noffset;
int sig_node, node;
char name[100];
sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
if (sig_node < 0) {
debug("%s: No signature node found\n", __func__);
return -ENOENT;
}
/* 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);
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;
}