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u-boot/lib/rsa/rsa-sign.c
mario.six@gdsys.cc 2b9ec762c4 rsa: Fix return value and masked error 
When signing images, we repeatedly call fit_add_file_data() with
successively increasing size values to include the keys in the DTB.

Unfortunately, if large keys are used (such as 4096 bit RSA keys), this
process fails sometimes, and mkimage needs to be called repeatedly to
integrate the keys into the DTB.

This is because fit_add_file_data actually returns the wrong error
code, and the loop terminates prematurely, instead of trying again with
a larger size value.

This patch corrects the return value by fixing the return value of
fdt_add_bignum, fixes a case where an error is masked by a unconditional
setting of a return value variable, and also removes a error message,
which is misleading, since we actually allow the function to fail. A
(hopefully helpful) comment is also added to explain the lack of error
message.

This is probably related to 1152a05 ("tools: Correct error handling in
fit_image_process_hash()") and the corresponding error reported here:

https://www.mail-archive.com/u-boot@lists.denx.de/msg217417.html

Signed-off-by: Mario Six <mario.six@gdsys.cc>
2016-07-22 14:46:24 -04:00

522 lines
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/*
* Copyright (c) 2013, Google Inc.
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include "mkimage.h"
#include <stdio.h>
#include <string.h>
#include <image.h>
#include <time.h>
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/err.h>
#include <openssl/ssl.h>
#include <openssl/evp.h>
#if OPENSSL_VERSION_NUMBER >= 0x10000000L
#define HAVE_ERR_REMOVE_THREAD_STATE
#endif
static int rsa_err(const char *msg)
{
unsigned long sslErr = ERR_get_error();
fprintf(stderr, "%s", msg);
fprintf(stderr, ": %s\n",
ERR_error_string(sslErr, 0));
return -1;
}
/**
* rsa_get_pub_key() - read a public key from a .crt file
*
* @keydir: Directory containins the key
* @name Name of key file (will have a .crt extension)
* @rsap Returns RSA object, or NULL on failure
* @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
*/
static int rsa_get_pub_key(const char *keydir, const char *name, RSA **rsap)
{
char path[1024];
EVP_PKEY *key;
X509 *cert;
RSA *rsa;
FILE *f;
int ret;
*rsap = NULL;
snprintf(path, sizeof(path), "%s/%s.crt", keydir, name);
f = fopen(path, "r");
if (!f) {
fprintf(stderr, "Couldn't open RSA certificate: '%s': %s\n",
path, strerror(errno));
return -EACCES;
}
/* Read the certificate */
cert = NULL;
if (!PEM_read_X509(f, &cert, NULL, NULL)) {
rsa_err("Couldn't read certificate");
ret = -EINVAL;
goto err_cert;
}
/* Get the public key from the certificate. */
key = X509_get_pubkey(cert);
if (!key) {
rsa_err("Couldn't read public key\n");
ret = -EINVAL;
goto err_pubkey;
}
/* Convert to a RSA_style key. */
rsa = EVP_PKEY_get1_RSA(key);
if (!rsa) {
rsa_err("Couldn't convert to a RSA style key");
ret = -EINVAL;
goto err_rsa;
}
fclose(f);
EVP_PKEY_free(key);
X509_free(cert);
*rsap = rsa;
return 0;
err_rsa:
EVP_PKEY_free(key);
err_pubkey:
X509_free(cert);
err_cert:
fclose(f);
return ret;
}
/**
* rsa_get_priv_key() - read a private key from a .key file
*
* @keydir: Directory containins the key
* @name Name of key file (will have a .key extension)
* @rsap Returns RSA object, or NULL on failure
* @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
*/
static int rsa_get_priv_key(const char *keydir, const char *name, RSA **rsap)
{
char path[1024];
RSA *rsa;
FILE *f;
*rsap = NULL;
snprintf(path, sizeof(path), "%s/%s.key", keydir, name);
f = fopen(path, "r");
if (!f) {
fprintf(stderr, "Couldn't open RSA private key: '%s': %s\n",
path, strerror(errno));
return -ENOENT;
}
rsa = PEM_read_RSAPrivateKey(f, 0, NULL, path);
if (!rsa) {
rsa_err("Failure reading private key");
fclose(f);
return -EPROTO;
}
fclose(f);
*rsap = rsa;
return 0;
}
static int rsa_init(void)
{
int ret;
ret = SSL_library_init();
if (!ret) {
fprintf(stderr, "Failure to init SSL library\n");
return -1;
}
SSL_load_error_strings();
OpenSSL_add_all_algorithms();
OpenSSL_add_all_digests();
OpenSSL_add_all_ciphers();
return 0;
}
static void rsa_remove(void)
{
CRYPTO_cleanup_all_ex_data();
ERR_free_strings();
#ifdef HAVE_ERR_REMOVE_THREAD_STATE
ERR_remove_thread_state(NULL);
#else
ERR_remove_state(0);
#endif
EVP_cleanup();
}
static int rsa_sign_with_key(RSA *rsa, struct checksum_algo *checksum_algo,
const struct image_region region[], int region_count,
uint8_t **sigp, uint *sig_size)
{
EVP_PKEY *key;
EVP_MD_CTX *context;
int size, ret = 0;
uint8_t *sig;
int i;
key = EVP_PKEY_new();
if (!key)
return rsa_err("EVP_PKEY object creation failed");
if (!EVP_PKEY_set1_RSA(key, rsa)) {
ret = rsa_err("EVP key setup failed");
goto err_set;
}
size = EVP_PKEY_size(key);
sig = malloc(size);
if (!sig) {
fprintf(stderr, "Out of memory for signature (%d bytes)\n",
size);
ret = -ENOMEM;
goto err_alloc;
}
context = EVP_MD_CTX_create();
if (!context) {
ret = rsa_err("EVP context creation failed");
goto err_create;
}
EVP_MD_CTX_init(context);
if (!EVP_SignInit(context, checksum_algo->calculate_sign())) {
ret = rsa_err("Signer setup failed");
goto err_sign;
}
for (i = 0; i < region_count; i++) {
if (!EVP_SignUpdate(context, region[i].data, region[i].size)) {
ret = rsa_err("Signing data failed");
goto err_sign;
}
}
if (!EVP_SignFinal(context, sig, sig_size, key)) {
ret = rsa_err("Could not obtain signature");
goto err_sign;
}
EVP_MD_CTX_cleanup(context);
EVP_MD_CTX_destroy(context);
EVP_PKEY_free(key);
debug("Got signature: %d bytes, expected %d\n", *sig_size, size);
*sigp = sig;
*sig_size = size;
return 0;
err_sign:
EVP_MD_CTX_destroy(context);
err_create:
free(sig);
err_alloc:
err_set:
EVP_PKEY_free(key);
return ret;
}
int rsa_sign(struct image_sign_info *info,
const struct image_region region[], int region_count,
uint8_t **sigp, uint *sig_len)
{
RSA *rsa;
int ret;
ret = rsa_init();
if (ret)
return ret;
ret = rsa_get_priv_key(info->keydir, info->keyname, &rsa);
if (ret)
goto err_priv;
ret = rsa_sign_with_key(rsa, info->algo->checksum, region,
region_count, sigp, sig_len);
if (ret)
goto err_sign;
RSA_free(rsa);
rsa_remove();
return ret;
err_sign:
RSA_free(rsa);
err_priv:
rsa_remove();
return ret;
}
/*
* rsa_get_exponent(): - Get the public exponent from an RSA key
*/
static int rsa_get_exponent(RSA *key, uint64_t *e)
{
int ret;
BIGNUM *bn_te;
uint64_t te;
ret = -EINVAL;
bn_te = NULL;
if (!e)
goto cleanup;
if (BN_num_bits(key->e) > 64)
goto cleanup;
*e = BN_get_word(key->e);
if (BN_num_bits(key->e) < 33) {
ret = 0;
goto cleanup;
}
bn_te = BN_dup(key->e);
if (!bn_te)
goto cleanup;
if (!BN_rshift(bn_te, bn_te, 32))
goto cleanup;
if (!BN_mask_bits(bn_te, 32))
goto cleanup;
te = BN_get_word(bn_te);
te <<= 32;
*e |= te;
ret = 0;
cleanup:
if (bn_te)
BN_free(bn_te);
return ret;
}
/*
* rsa_get_params(): - Get the important parameters of an RSA public key
*/
int rsa_get_params(RSA *key, uint64_t *exponent, uint32_t *n0_invp,
BIGNUM **modulusp, BIGNUM **r_squaredp)
{
BIGNUM *big1, *big2, *big32, *big2_32;
BIGNUM *n, *r, *r_squared, *tmp;
BN_CTX *bn_ctx = BN_CTX_new();
int ret = 0;
/* Initialize BIGNUMs */
big1 = BN_new();
big2 = BN_new();
big32 = BN_new();
r = BN_new();
r_squared = BN_new();
tmp = BN_new();
big2_32 = BN_new();
n = BN_new();
if (!big1 || !big2 || !big32 || !r || !r_squared || !tmp || !big2_32 ||
!n) {
fprintf(stderr, "Out of memory (bignum)\n");
return -ENOMEM;
}
if (0 != rsa_get_exponent(key, exponent))
ret = -1;
if (!BN_copy(n, key->n) || !BN_set_word(big1, 1L) ||
!BN_set_word(big2, 2L) || !BN_set_word(big32, 32L))
ret = -1;
/* big2_32 = 2^32 */
if (!BN_exp(big2_32, big2, big32, bn_ctx))
ret = -1;
/* Calculate n0_inv = -1 / n[0] mod 2^32 */
if (!BN_mod_inverse(tmp, n, big2_32, bn_ctx) ||
!BN_sub(tmp, big2_32, tmp))
ret = -1;
*n0_invp = BN_get_word(tmp);
/* Calculate R = 2^(# of key bits) */
if (!BN_set_word(tmp, BN_num_bits(n)) ||
!BN_exp(r, big2, tmp, bn_ctx))
ret = -1;
/* Calculate r_squared = R^2 mod n */
if (!BN_copy(r_squared, r) ||
!BN_mul(tmp, r_squared, r, bn_ctx) ||
!BN_mod(r_squared, tmp, n, bn_ctx))
ret = -1;
*modulusp = n;
*r_squaredp = r_squared;
BN_free(big1);
BN_free(big2);
BN_free(big32);
BN_free(r);
BN_free(tmp);
BN_free(big2_32);
if (ret) {
fprintf(stderr, "Bignum operations failed\n");
return -ENOMEM;
}
return ret;
}
static int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
BIGNUM *num, int num_bits)
{
int nwords = num_bits / 32;
int size;
uint32_t *buf, *ptr;
BIGNUM *tmp, *big2, *big32, *big2_32;
BN_CTX *ctx;
int ret;
tmp = BN_new();
big2 = BN_new();
big32 = BN_new();
big2_32 = BN_new();
if (!tmp || !big2 || !big32 || !big2_32) {
fprintf(stderr, "Out of memory (bignum)\n");
return -ENOMEM;
}
ctx = BN_CTX_new();
if (!tmp) {
fprintf(stderr, "Out of memory (bignum context)\n");
return -ENOMEM;
}
BN_set_word(big2, 2L);
BN_set_word(big32, 32L);
BN_exp(big2_32, big2, big32, ctx); /* B = 2^32 */
size = nwords * sizeof(uint32_t);
buf = malloc(size);
if (!buf) {
fprintf(stderr, "Out of memory (%d bytes)\n", size);
return -ENOMEM;
}
/* Write out modulus as big endian array of integers */
for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
*ptr = cpu_to_fdt32(BN_get_word(tmp));
BN_rshift(num, num, 32); /* N = N/B */
}
/* We try signing with successively increasing size values, so this
* might fail several times */
ret = fdt_setprop(blob, noffset, prop_name, buf, size);
if (ret)
return -FDT_ERR_NOSPACE;
free(buf);
BN_free(tmp);
BN_free(big2);
BN_free(big32);
BN_free(big2_32);
return ret;
}
int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
{
BIGNUM *modulus, *r_squared;
uint64_t exponent;
uint32_t n0_inv;
int parent, node;
char name[100];
int ret;
int bits;
RSA *rsa;
debug("%s: Getting verification data\n", __func__);
ret = rsa_get_pub_key(info->keydir, info->keyname, &rsa);
if (ret)
return ret;
ret = rsa_get_params(rsa, &exponent, &n0_inv, &modulus, &r_squared);
if (ret)
return ret;
bits = BN_num_bits(modulus);
parent = fdt_subnode_offset(keydest, 0, FIT_SIG_NODENAME);
if (parent == -FDT_ERR_NOTFOUND) {
parent = fdt_add_subnode(keydest, 0, FIT_SIG_NODENAME);
if (parent < 0) {
ret = parent;
if (ret != -FDT_ERR_NOSPACE) {
fprintf(stderr, "Couldn't create signature node: %s\n",
fdt_strerror(parent));
}
}
}
if (ret)
goto done;
/* Either create or overwrite the named key node */
snprintf(name, sizeof(name), "key-%s", info->keyname);
node = fdt_subnode_offset(keydest, parent, name);
if (node == -FDT_ERR_NOTFOUND) {
node = fdt_add_subnode(keydest, parent, name);
if (node < 0) {
ret = node;
if (ret != -FDT_ERR_NOSPACE) {
fprintf(stderr, "Could not create key subnode: %s\n",
fdt_strerror(node));
}
}
} else if (node < 0) {
fprintf(stderr, "Cannot select keys parent: %s\n",
fdt_strerror(node));
ret = node;
}
if (!ret) {
ret = fdt_setprop_string(keydest, node, "key-name-hint",
info->keyname);
}
if (!ret)
ret = fdt_setprop_u32(keydest, node, "rsa,num-bits", bits);
if (!ret)
ret = fdt_setprop_u32(keydest, node, "rsa,n0-inverse", n0_inv);
if (!ret) {
ret = fdt_setprop_u64(keydest, node, "rsa,exponent", exponent);
}
if (!ret) {
ret = fdt_add_bignum(keydest, node, "rsa,modulus", modulus,
bits);
}
if (!ret) {
ret = fdt_add_bignum(keydest, node, "rsa,r-squared", r_squared,
bits);
}
if (!ret) {
ret = fdt_setprop_string(keydest, node, FIT_ALGO_PROP,
info->algo->name);
}
if (!ret && info->require_keys) {
ret = fdt_setprop_string(keydest, node, "required",
info->require_keys);
}
done:
BN_free(modulus);
BN_free(r_squared);
if (ret)
return ret == -FDT_ERR_NOSPACE ? -ENOSPC : -EIO;
return 0;
}
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