lib/rsa/rsa-verify.c

   1 /*
   2  * Copyright (c) 2013, Google Inc.
   3  *
   4  * SPDX-License-Identifier:     GPL-2.0+
   5  */
   6
   7 #ifndef USE_HOSTCC
   8 #include <common.h>
   9 #include <fdtdec.h>
  10 #include <asm/types.h>
  11 #include <asm/byteorder.h>
  12 #include <asm/errno.h>
  13 #include <asm/types.h>
  14 #include <asm/unaligned.h>
  15 #include <dm.h>
  16 #else
  17 #include "fdt_host.h"
  18 #include "mkimage.h"
  19 #include <fdt_support.h>
  20 #endif
  21 #include <u-boot/rsa-mod-exp.h>
  22 #include <u-boot/rsa.h>
  23
  24 /* Default public exponent for backward compatibility */
  25 #define RSA_DEFAULT_PUBEXP      65537
  26
  27 /**
  28  * rsa_verify_key() - Verify a signature against some data using RSA Key
  29  *
  30  * Verify a RSA PKCS1.5 signature against an expected hash using
  31  * the RSA Key properties in prop structure.
  32  *
  33  * @prop:       Specifies key
  34  * @sig:        Signature
  35  * @sig_len:    Number of bytes in signature
  36  * @hash:       Pointer to the expected hash
  37  * @algo:       Checksum algo structure having information on RSA padding etc.
  38  * @return 0 if verified, -ve on error
  39  */
  40 static int rsa_verify_key(struct key_prop *prop, const uint8_t *sig,
  41                           const uint32_t sig_len, const uint8_t *hash,
  42                           struct checksum_algo *algo)
  43 {
  44         const uint8_t *padding;
  45         int pad_len;
  46         int ret;
  47 #if !defined(USE_HOSTCC)
  48         struct udevice *mod_exp_dev;
  49 #endif
  50
  51         if (!prop || !sig || !hash || !algo)
  52                 return -EIO;
  53
  54         if (sig_len != (prop->num_bits / 8)) {
  55                 debug("Signature is of incorrect length %d\n", sig_len);
  56                 return -EINVAL;
  57         }
  58
  59         debug("Checksum algorithm: %s", algo->name);
  60
  61         /* Sanity check for stack size */
  62         if (sig_len > RSA_MAX_SIG_BITS / 8) {
  63                 debug("Signature length %u exceeds maximum %d\n", sig_len,
  64                       RSA_MAX_SIG_BITS / 8);
  65                 return -EINVAL;
  66         }
  67
  68         uint8_t buf[sig_len];
  69
  70 #if !defined(USE_HOSTCC)
  71         ret = uclass_get_device(UCLASS_MOD_EXP, 0, &mod_exp_dev);
  72         if (ret) {
  73                 printf("RSA: Can't find Modular Exp implementation\n");
  74                 return -EINVAL;
  75         }
  76
  77         ret = rsa_mod_exp(mod_exp_dev, sig, sig_len, prop, buf);
  78 #else
  79         ret = rsa_mod_exp_sw(sig, sig_len, prop, buf);
  80 #endif
  81         if (ret) {
  82                 debug("Error in Modular exponentation\n");
  83                 return ret;
  84         }
  85
  86         padding = algo->rsa_padding;
  87         pad_len = algo->pad_len - algo->checksum_len;
  88
  89         /* Check pkcs1.5 padding bytes. */
  90         if (memcmp(buf, padding, pad_len)) {
  91                 debug("In RSAVerify(): Padding check failed!\n");
  92                 return -EINVAL;
  93         }
  94
  95         /* Check hash. */
  96         if (memcmp((uint8_t *)buf + pad_len, hash, sig_len - pad_len)) {
  97                 debug("In RSAVerify(): Hash check failed!\n");
  98                 return -EACCES;
  99         }
 100
 101         return 0;
 102 }
 103
 104 /**
 105  * rsa_verify_with_keynode() - Verify a signature against some data using
 106  * information in node with prperties of RSA Key like modulus, exponent etc.
 107  *
 108  * Parse sign-node and fill a key_prop structure with properties of the
 109  * key.  Verify a RSA PKCS1.5 signature against an expected hash using
 110  * the properties parsed
 111  *
 112  * @info:       Specifies key and FIT information
 113  * @hash:       Pointer to the expected hash
 114  * @sig:        Signature
 115  * @sig_len:    Number of bytes in signature
 116  * @node:       Node having the RSA Key properties
 117  * @return 0 if verified, -ve on error
 118  */
 119 static int rsa_verify_with_keynode(struct image_sign_info *info,
 120                                    const void *hash, uint8_t *sig,
 121                                    uint sig_len, int node)
 122 {
 123         const void *blob = info->fdt_blob;
 124         struct key_prop prop;
 125         int length;
 126         int ret = 0;
 127
 128         if (node < 0) {
 129                 debug("%s: Skipping invalid node", __func__);
 130                 return -EBADF;
 131         }
 132
 133         prop.num_bits = fdtdec_get_int(blob, node, "rsa,num-bits", 0);
 134
 135         prop.n0inv = fdtdec_get_int(blob, node, "rsa,n0-inverse", 0);
 136
 137         prop.public_exponent = fdt_getprop(blob, node, "rsa,exponent", &length);
 138         if (!prop.public_exponent || length < sizeof(uint64_t))
 139                 prop.public_exponent = NULL;
 140
 141         prop.exp_len = sizeof(uint64_t);
 142
 143         prop.modulus = fdt_getprop(blob, node, "rsa,modulus", NULL);
 144
 145         prop.rr = fdt_getprop(blob, node, "rsa,r-squared", NULL);
 146
 147         if (!prop.num_bits || !prop.modulus) {
 148                 debug("%s: Missing RSA key info", __func__);
 149                 return -EFAULT;
 150         }
 151
 152         ret = rsa_verify_key(&prop, sig, sig_len, hash, info->algo->checksum);
 153
 154         return ret;
 155 }
 156
 157 int rsa_verify(struct image_sign_info *info,
 158                const struct image_region region[], int region_count,
 159                uint8_t *sig, uint sig_len)
 160 {
 161         const void *blob = info->fdt_blob;
 162         /* Reserve memory for maximum checksum-length */
 163         uint8_t hash[info->algo->checksum->pad_len];
 164         int ndepth, noffset;
 165         int sig_node, node;
 166         char name[100];
 167         int ret;
 168
 169         /*
 170          * Verify that the checksum-length does not exceed the
 171          * rsa-signature-length
 172          */
 173         if (info->algo->checksum->checksum_len >
 174             info->algo->checksum->pad_len) {
 175                 debug("%s: invlaid checksum-algorithm %s for %s\n",
 176                       __func__, info->algo->checksum->name, info->algo->name);
 177                 return -EINVAL;
 178         }
 179
 180         sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
 181         if (sig_node < 0) {
 182                 debug("%s: No signature node found\n", __func__);
 183                 return -ENOENT;
 184         }
 185
 186         /* Calculate checksum with checksum-algorithm */
 187         ret = info->algo->checksum->calculate(info->algo->checksum->name,
 188                                         region, region_count, hash);
 189         if (ret < 0) {
 190                 debug("%s: Error in checksum calculation\n", __func__);
 191                 return -EINVAL;
 192         }
 193
 194         /* See if we must use a particular key */
 195         if (info->required_keynode != -1) {
 196                 ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
 197                         info->required_keynode);
 198                 if (!ret)
 199                         return ret;
 200         }
 201
 202         /* Look for a key that matches our hint */
 203         snprintf(name, sizeof(name), "key-%s", info->keyname);
 204         node = fdt_subnode_offset(blob, sig_node, name);
 205         ret = rsa_verify_with_keynode(info, hash, sig, sig_len, node);
 206         if (!ret)
 207                 return ret;
 208
 209         /* No luck, so try each of the keys in turn */
 210         for (ndepth = 0, noffset = fdt_next_node(info->fit, sig_node, &ndepth);
 211                         (noffset >= 0) && (ndepth > 0);
 212                         noffset = fdt_next_node(info->fit, noffset, &ndepth)) {
 213                 if (ndepth == 1 && noffset != node) {
 214                         ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
 215                                                       noffset);
 216                         if (!ret)
 217                                 break;
 218                 }
 219         }
 220
 221         return ret;
 222 }