Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2013, Google Inc. |
| 3 | * |
Wolfgang Denk | 1a45966 | 2013-07-08 09:37:19 +0200 | [diff] [blame] | 4 | * SPDX-License-Identifier: GPL-2.0+ |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 5 | */ |
| 6 | |
| 7 | #include <common.h> |
| 8 | #include <fdtdec.h> |
| 9 | #include <rsa.h> |
| 10 | #include <sha1.h> |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 11 | #include <sha256.h> |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 12 | #include <asm/byteorder.h> |
| 13 | #include <asm/errno.h> |
| 14 | #include <asm/unaligned.h> |
| 15 | |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 16 | #define UINT64_MULT32(v, multby) (((uint64_t)(v)) * ((uint32_t)(multby))) |
| 17 | |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 18 | /** |
| 19 | * subtract_modulus() - subtract modulus from the given value |
| 20 | * |
| 21 | * @key: Key containing modulus to subtract |
| 22 | * @num: Number to subtract modulus from, as little endian word array |
| 23 | */ |
| 24 | static void subtract_modulus(const struct rsa_public_key *key, uint32_t num[]) |
| 25 | { |
| 26 | int64_t acc = 0; |
| 27 | uint i; |
| 28 | |
| 29 | for (i = 0; i < key->len; i++) { |
| 30 | acc += (uint64_t)num[i] - key->modulus[i]; |
| 31 | num[i] = (uint32_t)acc; |
| 32 | acc >>= 32; |
| 33 | } |
| 34 | } |
| 35 | |
| 36 | /** |
| 37 | * greater_equal_modulus() - check if a value is >= modulus |
| 38 | * |
| 39 | * @key: Key containing modulus to check |
| 40 | * @num: Number to check against modulus, as little endian word array |
| 41 | * @return 0 if num < modulus, 1 if num >= modulus |
| 42 | */ |
| 43 | static int greater_equal_modulus(const struct rsa_public_key *key, |
| 44 | uint32_t num[]) |
| 45 | { |
| 46 | uint32_t i; |
| 47 | |
| 48 | for (i = key->len - 1; i >= 0; i--) { |
| 49 | if (num[i] < key->modulus[i]) |
| 50 | return 0; |
| 51 | if (num[i] > key->modulus[i]) |
| 52 | return 1; |
| 53 | } |
| 54 | |
| 55 | return 1; /* equal */ |
| 56 | } |
| 57 | |
| 58 | /** |
| 59 | * montgomery_mul_add_step() - Perform montgomery multiply-add step |
| 60 | * |
| 61 | * Operation: montgomery result[] += a * b[] / n0inv % modulus |
| 62 | * |
| 63 | * @key: RSA key |
| 64 | * @result: Place to put result, as little endian word array |
| 65 | * @a: Multiplier |
| 66 | * @b: Multiplicand, as little endian word array |
| 67 | */ |
| 68 | static void montgomery_mul_add_step(const struct rsa_public_key *key, |
| 69 | uint32_t result[], const uint32_t a, const uint32_t b[]) |
| 70 | { |
| 71 | uint64_t acc_a, acc_b; |
| 72 | uint32_t d0; |
| 73 | uint i; |
| 74 | |
| 75 | acc_a = (uint64_t)a * b[0] + result[0]; |
| 76 | d0 = (uint32_t)acc_a * key->n0inv; |
| 77 | acc_b = (uint64_t)d0 * key->modulus[0] + (uint32_t)acc_a; |
| 78 | for (i = 1; i < key->len; i++) { |
| 79 | acc_a = (acc_a >> 32) + (uint64_t)a * b[i] + result[i]; |
| 80 | acc_b = (acc_b >> 32) + (uint64_t)d0 * key->modulus[i] + |
| 81 | (uint32_t)acc_a; |
| 82 | result[i - 1] = (uint32_t)acc_b; |
| 83 | } |
| 84 | |
| 85 | acc_a = (acc_a >> 32) + (acc_b >> 32); |
| 86 | |
| 87 | result[i - 1] = (uint32_t)acc_a; |
| 88 | |
| 89 | if (acc_a >> 32) |
| 90 | subtract_modulus(key, result); |
| 91 | } |
| 92 | |
| 93 | /** |
| 94 | * montgomery_mul() - Perform montgomery mutitply |
| 95 | * |
| 96 | * Operation: montgomery result[] = a[] * b[] / n0inv % modulus |
| 97 | * |
| 98 | * @key: RSA key |
| 99 | * @result: Place to put result, as little endian word array |
| 100 | * @a: Multiplier, as little endian word array |
| 101 | * @b: Multiplicand, as little endian word array |
| 102 | */ |
| 103 | static void montgomery_mul(const struct rsa_public_key *key, |
| 104 | uint32_t result[], uint32_t a[], const uint32_t b[]) |
| 105 | { |
| 106 | uint i; |
| 107 | |
| 108 | for (i = 0; i < key->len; ++i) |
| 109 | result[i] = 0; |
| 110 | for (i = 0; i < key->len; ++i) |
| 111 | montgomery_mul_add_step(key, result, a[i], b); |
| 112 | } |
| 113 | |
| 114 | /** |
| 115 | * pow_mod() - in-place public exponentiation |
| 116 | * |
| 117 | * @key: RSA key |
| 118 | * @inout: Big-endian word array containing value and result |
| 119 | */ |
| 120 | static int pow_mod(const struct rsa_public_key *key, uint32_t *inout) |
| 121 | { |
| 122 | uint32_t *result, *ptr; |
| 123 | uint i; |
| 124 | |
| 125 | /* Sanity check for stack size - key->len is in 32-bit words */ |
| 126 | if (key->len > RSA_MAX_KEY_BITS / 32) { |
| 127 | debug("RSA key words %u exceeds maximum %d\n", key->len, |
| 128 | RSA_MAX_KEY_BITS / 32); |
| 129 | return -EINVAL; |
| 130 | } |
| 131 | |
| 132 | uint32_t val[key->len], acc[key->len], tmp[key->len]; |
| 133 | result = tmp; /* Re-use location. */ |
| 134 | |
| 135 | /* Convert from big endian byte array to little endian word array. */ |
| 136 | for (i = 0, ptr = inout + key->len - 1; i < key->len; i++, ptr--) |
| 137 | val[i] = get_unaligned_be32(ptr); |
| 138 | |
| 139 | montgomery_mul(key, acc, val, key->rr); /* axx = a * RR / R mod M */ |
| 140 | for (i = 0; i < 16; i += 2) { |
| 141 | montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod M */ |
| 142 | montgomery_mul(key, acc, tmp, tmp); /* acc = tmp^2 / R mod M */ |
| 143 | } |
| 144 | montgomery_mul(key, result, acc, val); /* result = XX * a / R mod M */ |
| 145 | |
| 146 | /* Make sure result < mod; result is at most 1x mod too large. */ |
| 147 | if (greater_equal_modulus(key, result)) |
| 148 | subtract_modulus(key, result); |
| 149 | |
| 150 | /* Convert to bigendian byte array */ |
| 151 | for (i = key->len - 1, ptr = inout; (int)i >= 0; i--, ptr++) |
| 152 | put_unaligned_be32(result[i], ptr); |
| 153 | |
| 154 | return 0; |
| 155 | } |
| 156 | |
| 157 | static int rsa_verify_key(const struct rsa_public_key *key, const uint8_t *sig, |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 158 | const uint32_t sig_len, const uint8_t *hash, |
| 159 | struct checksum_algo *algo) |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 160 | { |
| 161 | const uint8_t *padding; |
| 162 | int pad_len; |
| 163 | int ret; |
| 164 | |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 165 | if (!key || !sig || !hash || !algo) |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 166 | return -EIO; |
| 167 | |
| 168 | if (sig_len != (key->len * sizeof(uint32_t))) { |
| 169 | debug("Signature is of incorrect length %d\n", sig_len); |
| 170 | return -EINVAL; |
| 171 | } |
| 172 | |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 173 | debug("Checksum algorithm: %s", algo->name); |
| 174 | |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 175 | /* Sanity check for stack size */ |
| 176 | if (sig_len > RSA_MAX_SIG_BITS / 8) { |
| 177 | debug("Signature length %u exceeds maximum %d\n", sig_len, |
| 178 | RSA_MAX_SIG_BITS / 8); |
| 179 | return -EINVAL; |
| 180 | } |
| 181 | |
| 182 | uint32_t buf[sig_len / sizeof(uint32_t)]; |
| 183 | |
| 184 | memcpy(buf, sig, sig_len); |
| 185 | |
| 186 | ret = pow_mod(key, buf); |
| 187 | if (ret) |
| 188 | return ret; |
| 189 | |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 190 | padding = algo->rsa_padding; |
Heiko Schocher | db1b5f3 | 2014-03-03 12:19:27 +0100 | [diff] [blame] | 191 | pad_len = algo->pad_len - algo->checksum_len; |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 192 | |
| 193 | /* Check pkcs1.5 padding bytes. */ |
| 194 | if (memcmp(buf, padding, pad_len)) { |
| 195 | debug("In RSAVerify(): Padding check failed!\n"); |
| 196 | return -EINVAL; |
| 197 | } |
| 198 | |
| 199 | /* Check hash. */ |
| 200 | if (memcmp((uint8_t *)buf + pad_len, hash, sig_len - pad_len)) { |
| 201 | debug("In RSAVerify(): Hash check failed!\n"); |
| 202 | return -EACCES; |
| 203 | } |
| 204 | |
| 205 | return 0; |
| 206 | } |
| 207 | |
| 208 | static void rsa_convert_big_endian(uint32_t *dst, const uint32_t *src, int len) |
| 209 | { |
| 210 | int i; |
| 211 | |
| 212 | for (i = 0; i < len; i++) |
| 213 | dst[i] = fdt32_to_cpu(src[len - 1 - i]); |
| 214 | } |
| 215 | |
| 216 | static int rsa_verify_with_keynode(struct image_sign_info *info, |
| 217 | const void *hash, uint8_t *sig, uint sig_len, int node) |
| 218 | { |
| 219 | const void *blob = info->fdt_blob; |
| 220 | struct rsa_public_key key; |
| 221 | const void *modulus, *rr; |
| 222 | int ret; |
| 223 | |
| 224 | if (node < 0) { |
| 225 | debug("%s: Skipping invalid node", __func__); |
| 226 | return -EBADF; |
| 227 | } |
| 228 | if (!fdt_getprop(blob, node, "rsa,n0-inverse", NULL)) { |
| 229 | debug("%s: Missing rsa,n0-inverse", __func__); |
| 230 | return -EFAULT; |
| 231 | } |
| 232 | key.len = fdtdec_get_int(blob, node, "rsa,num-bits", 0); |
| 233 | key.n0inv = fdtdec_get_int(blob, node, "rsa,n0-inverse", 0); |
| 234 | modulus = fdt_getprop(blob, node, "rsa,modulus", NULL); |
| 235 | rr = fdt_getprop(blob, node, "rsa,r-squared", NULL); |
| 236 | if (!key.len || !modulus || !rr) { |
| 237 | debug("%s: Missing RSA key info", __func__); |
| 238 | return -EFAULT; |
| 239 | } |
| 240 | |
| 241 | /* Sanity check for stack size */ |
| 242 | if (key.len > RSA_MAX_KEY_BITS || key.len < RSA_MIN_KEY_BITS) { |
| 243 | debug("RSA key bits %u outside allowed range %d..%d\n", |
| 244 | key.len, RSA_MIN_KEY_BITS, RSA_MAX_KEY_BITS); |
| 245 | return -EFAULT; |
| 246 | } |
| 247 | key.len /= sizeof(uint32_t) * 8; |
| 248 | uint32_t key1[key.len], key2[key.len]; |
| 249 | |
| 250 | key.modulus = key1; |
| 251 | key.rr = key2; |
| 252 | rsa_convert_big_endian(key.modulus, modulus, key.len); |
| 253 | rsa_convert_big_endian(key.rr, rr, key.len); |
| 254 | if (!key.modulus || !key.rr) { |
| 255 | debug("%s: Out of memory", __func__); |
| 256 | return -ENOMEM; |
| 257 | } |
| 258 | |
| 259 | debug("key length %d\n", key.len); |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 260 | ret = rsa_verify_key(&key, sig, sig_len, hash, info->algo->checksum); |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 261 | if (ret) { |
| 262 | printf("%s: RSA failed to verify: %d\n", __func__, ret); |
| 263 | return ret; |
| 264 | } |
| 265 | |
| 266 | return 0; |
| 267 | } |
| 268 | |
| 269 | int rsa_verify(struct image_sign_info *info, |
| 270 | const struct image_region region[], int region_count, |
| 271 | uint8_t *sig, uint sig_len) |
| 272 | { |
| 273 | const void *blob = info->fdt_blob; |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 274 | /* Reserve memory for maximum checksum-length */ |
Heiko Schocher | db1b5f3 | 2014-03-03 12:19:27 +0100 | [diff] [blame] | 275 | uint8_t hash[info->algo->checksum->pad_len]; |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 276 | int ndepth, noffset; |
| 277 | int sig_node, node; |
| 278 | char name[100]; |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 279 | int ret; |
| 280 | |
| 281 | /* |
| 282 | * Verify that the checksum-length does not exceed the |
| 283 | * rsa-signature-length |
| 284 | */ |
Heiko Schocher | db1b5f3 | 2014-03-03 12:19:27 +0100 | [diff] [blame] | 285 | if (info->algo->checksum->checksum_len > |
| 286 | info->algo->checksum->pad_len) { |
| 287 | debug("%s: invlaid checksum-algorithm %s for %s\n", |
| 288 | __func__, info->algo->checksum->name, info->algo->name); |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 289 | return -EINVAL; |
| 290 | } |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 291 | |
| 292 | sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME); |
| 293 | if (sig_node < 0) { |
| 294 | debug("%s: No signature node found\n", __func__); |
| 295 | return -ENOENT; |
| 296 | } |
| 297 | |
Heiko Schocher | 646257d | 2014-03-03 12:19:26 +0100 | [diff] [blame] | 298 | /* Calculate checksum with checksum-algorithm */ |
| 299 | info->algo->checksum->calculate(region, region_count, hash); |
Simon Glass | 19c402a | 2013-06-13 15:10:02 -0700 | [diff] [blame] | 300 | |
| 301 | /* See if we must use a particular key */ |
| 302 | if (info->required_keynode != -1) { |
| 303 | ret = rsa_verify_with_keynode(info, hash, sig, sig_len, |
| 304 | info->required_keynode); |
| 305 | if (!ret) |
| 306 | return ret; |
| 307 | } |
| 308 | |
| 309 | /* Look for a key that matches our hint */ |
| 310 | snprintf(name, sizeof(name), "key-%s", info->keyname); |
| 311 | node = fdt_subnode_offset(blob, sig_node, name); |
| 312 | ret = rsa_verify_with_keynode(info, hash, sig, sig_len, node); |
| 313 | if (!ret) |
| 314 | return ret; |
| 315 | |
| 316 | /* No luck, so try each of the keys in turn */ |
| 317 | for (ndepth = 0, noffset = fdt_next_node(info->fit, sig_node, &ndepth); |
| 318 | (noffset >= 0) && (ndepth > 0); |
| 319 | noffset = fdt_next_node(info->fit, noffset, &ndepth)) { |
| 320 | if (ndepth == 1 && noffset != node) { |
| 321 | ret = rsa_verify_with_keynode(info, hash, sig, sig_len, |
| 322 | noffset); |
| 323 | if (!ret) |
| 324 | break; |
| 325 | } |
| 326 | } |
| 327 | |
| 328 | return ret; |
| 329 | } |