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 <linux/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_padding() - Verify RSA message padding is valid 29 * 30 * Verify a RSA message's padding is consistent with PKCS1.5 31 * padding as described in the RSA PKCS#1 v2.1 standard. 32 * 33 * @msg: Padded message 34 * @pad_len: Number of expected padding bytes 35 * @algo: Checksum algo structure having information on DER encoding etc. 36 * @return 0 on success, != 0 on failure 37 */ 38 static int rsa_verify_padding(const uint8_t *msg, const int pad_len, 39 struct checksum_algo *algo) 40 { 41 int ff_len; 42 int ret; 43 44 /* first byte must be 0x00 */ 45 ret = *msg++; 46 /* second byte must be 0x01 */ 47 ret |= *msg++ ^ 0x01; 48 /* next ff_len bytes must be 0xff */ 49 ff_len = pad_len - algo->der_len - 3; 50 ret |= *msg ^ 0xff; 51 ret |= memcmp(msg, msg+1, ff_len-1); 52 msg += ff_len; 53 /* next byte must be 0x00 */ 54 ret |= *msg++; 55 /* next der_len bytes must match der_prefix */ 56 ret |= memcmp(msg, algo->der_prefix, algo->der_len); 57 58 return ret; 59 } 60 61 /** 62 * rsa_verify_key() - Verify a signature against some data using RSA Key 63 * 64 * Verify a RSA PKCS1.5 signature against an expected hash using 65 * the RSA Key properties in prop structure. 66 * 67 * @prop: Specifies key 68 * @sig: Signature 69 * @sig_len: Number of bytes in signature 70 * @hash: Pointer to the expected hash 71 * @algo: Checksum algo structure having information on RSA padding etc. 72 * @return 0 if verified, -ve on error 73 */ 74 static int rsa_verify_key(struct key_prop *prop, const uint8_t *sig, 75 const uint32_t sig_len, const uint8_t *hash, 76 struct checksum_algo *algo) 77 { 78 const uint8_t *padding; 79 int pad_len; 80 int ret; 81 #if !defined(USE_HOSTCC) 82 struct udevice *mod_exp_dev; 83 #endif 84 85 if (!prop || !sig || !hash || !algo) 86 return -EIO; 87 88 if (sig_len != (prop->num_bits / 8)) { 89 debug("Signature is of incorrect length %d\n", sig_len); 90 return -EINVAL; 91 } 92 93 debug("Checksum algorithm: %s", algo->name); 94 95 /* Sanity check for stack size */ 96 if (sig_len > RSA_MAX_SIG_BITS / 8) { 97 debug("Signature length %u exceeds maximum %d\n", sig_len, 98 RSA_MAX_SIG_BITS / 8); 99 return -EINVAL; 100 } 101 102 uint8_t buf[sig_len]; 103 104 #if !defined(USE_HOSTCC) 105 ret = uclass_get_device(UCLASS_MOD_EXP, 0, &mod_exp_dev); 106 if (ret) { 107 printf("RSA: Can't find Modular Exp implementation\n"); 108 return -EINVAL; 109 } 110 111 ret = rsa_mod_exp(mod_exp_dev, sig, sig_len, prop, buf); 112 #else 113 ret = rsa_mod_exp_sw(sig, sig_len, prop, buf); 114 #endif 115 if (ret) { 116 debug("Error in Modular exponentation\n"); 117 return ret; 118 } 119 120 pad_len = algo->key_len - algo->checksum_len; 121 122 /* Check pkcs1.5 padding bytes. */ 123 ret = rsa_verify_padding(buf, pad_len, algo); 124 if (ret) { 125 debug("In RSAVerify(): Padding check failed!\n"); 126 return -EINVAL; 127 } 128 129 /* Check hash. */ 130 if (memcmp((uint8_t *)buf + pad_len, hash, sig_len - pad_len)) { 131 debug("In RSAVerify(): Hash check failed!\n"); 132 return -EACCES; 133 } 134 135 return 0; 136 } 137 138 /** 139 * rsa_verify_with_keynode() - Verify a signature against some data using 140 * information in node with prperties of RSA Key like modulus, exponent etc. 141 * 142 * Parse sign-node and fill a key_prop structure with properties of the 143 * key. Verify a RSA PKCS1.5 signature against an expected hash using 144 * the properties parsed 145 * 146 * @info: Specifies key and FIT information 147 * @hash: Pointer to the expected hash 148 * @sig: Signature 149 * @sig_len: Number of bytes in signature 150 * @node: Node having the RSA Key properties 151 * @return 0 if verified, -ve on error 152 */ 153 static int rsa_verify_with_keynode(struct image_sign_info *info, 154 const void *hash, uint8_t *sig, 155 uint sig_len, int node) 156 { 157 const void *blob = info->fdt_blob; 158 struct key_prop prop; 159 int length; 160 int ret = 0; 161 162 if (node < 0) { 163 debug("%s: Skipping invalid node", __func__); 164 return -EBADF; 165 } 166 167 prop.num_bits = fdtdec_get_int(blob, node, "rsa,num-bits", 0); 168 169 prop.n0inv = fdtdec_get_int(blob, node, "rsa,n0-inverse", 0); 170 171 prop.public_exponent = fdt_getprop(blob, node, "rsa,exponent", &length); 172 if (!prop.public_exponent || length < sizeof(uint64_t)) 173 prop.public_exponent = NULL; 174 175 prop.exp_len = sizeof(uint64_t); 176 177 prop.modulus = fdt_getprop(blob, node, "rsa,modulus", NULL); 178 179 prop.rr = fdt_getprop(blob, node, "rsa,r-squared", NULL); 180 181 if (!prop.num_bits || !prop.modulus) { 182 debug("%s: Missing RSA key info", __func__); 183 return -EFAULT; 184 } 185 186 ret = rsa_verify_key(&prop, sig, sig_len, hash, info->algo->checksum); 187 188 return ret; 189 } 190 191 int rsa_verify(struct image_sign_info *info, 192 const struct image_region region[], int region_count, 193 uint8_t *sig, uint sig_len) 194 { 195 const void *blob = info->fdt_blob; 196 /* Reserve memory for maximum checksum-length */ 197 uint8_t hash[info->algo->checksum->key_len]; 198 int ndepth, noffset; 199 int sig_node, node; 200 char name[100]; 201 int ret; 202 203 /* 204 * Verify that the checksum-length does not exceed the 205 * rsa-signature-length 206 */ 207 if (info->algo->checksum->checksum_len > 208 info->algo->checksum->key_len) { 209 debug("%s: invlaid checksum-algorithm %s for %s\n", 210 __func__, info->algo->checksum->name, info->algo->name); 211 return -EINVAL; 212 } 213 214 sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME); 215 if (sig_node < 0) { 216 debug("%s: No signature node found\n", __func__); 217 return -ENOENT; 218 } 219 220 /* Calculate checksum with checksum-algorithm */ 221 ret = info->algo->checksum->calculate(info->algo->checksum->name, 222 region, region_count, hash); 223 if (ret < 0) { 224 debug("%s: Error in checksum calculation\n", __func__); 225 return -EINVAL; 226 } 227 228 /* See if we must use a particular key */ 229 if (info->required_keynode != -1) { 230 ret = rsa_verify_with_keynode(info, hash, sig, sig_len, 231 info->required_keynode); 232 if (!ret) 233 return ret; 234 } 235 236 /* Look for a key that matches our hint */ 237 snprintf(name, sizeof(name), "key-%s", info->keyname); 238 node = fdt_subnode_offset(blob, sig_node, name); 239 ret = rsa_verify_with_keynode(info, hash, sig, sig_len, node); 240 if (!ret) 241 return ret; 242 243 /* No luck, so try each of the keys in turn */ 244 for (ndepth = 0, noffset = fdt_next_node(info->fit, sig_node, &ndepth); 245 (noffset >= 0) && (ndepth > 0); 246 noffset = fdt_next_node(info->fit, noffset, &ndepth)) { 247 if (ndepth == 1 && noffset != node) { 248 ret = rsa_verify_with_keynode(info, hash, sig, sig_len, 249 noffset); 250 if (!ret) 251 break; 252 } 253 } 254 255 return ret; 256 } 257