u-boot/lib/rsa/rsa-verify.c
Tom Rini 83d290c56f SPDX: Convert all of our single license tags to Linux Kernel style
When U-Boot started using SPDX tags we were among the early adopters and
there weren't a lot of other examples to borrow from.  So we picked the
area of the file that usually had a full license text and replaced it
with an appropriate SPDX-License-Identifier: entry.  Since then, the
Linux Kernel has adopted SPDX tags and they place it as the very first
line in a file (except where shebangs are used, then it's second line)
and with slightly different comment styles than us.

In part due to community overlap, in part due to better tag visibility
and in part for other minor reasons, switch over to that style.

This commit changes all instances where we have a single declared
license in the tag as both the before and after are identical in tag
contents.  There's also a few places where I found we did not have a tag
and have introduced one.

Signed-off-by: Tom Rini <trini@konsulko.com>
2018-05-07 09:34:12 -04:00

256 lines
6.6 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;
}
/**
* 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.
*
* @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
* @algo: Checksum algo structure having information on DER encoding etc.
* @return 0 if verified, -ve on error
*/
static int rsa_verify_key(struct key_prop *prop, const uint8_t *sig,
const uint32_t sig_len, const uint8_t *hash,
const uint32_t key_len, struct checksum_algo *algo)
{
int pad_len;
int ret;
#if !defined(USE_HOSTCC)
struct udevice *mod_exp_dev;
#endif
if (!prop || !sig || !hash || !algo)
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", algo->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];
#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;
}
pad_len = key_len - algo->checksum_len;
/* Check pkcs1.5 padding bytes. */
ret = rsa_verify_padding(buf, pad_len, algo);
if (ret) {
debug("In RSAVerify(): Padding check failed!\n");
return -EINVAL;
}
/* Check hash. */
if (memcmp((uint8_t *)buf + pad_len, hash, sig_len - pad_len)) {
debug("In RSAVerify(): Hash check failed!\n");
return -EACCES;
}
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(&prop, sig, sig_len, hash,
info->crypto->key_len, info->checksum);
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;
}