Ruchika Gupta | b92ebab | 2015-01-23 16:01:50 +0530 | [diff] [blame] | 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> |
Masahiro Yamada | 56a931c | 2016-09-21 11:28:55 +0900 | [diff] [blame] | 12 | #include <linux/errno.h> |
Ruchika Gupta | b92ebab | 2015-01-23 16:01:50 +0530 | [diff] [blame] | 13 | #include <asm/types.h> |
| 14 | #include <asm/unaligned.h> |
| 15 | #else |
| 16 | #include "fdt_host.h" |
| 17 | #include "mkimage.h" |
| 18 | #include <fdt_support.h> |
| 19 | #endif |
| 20 | #include <u-boot/rsa.h> |
| 21 | #include <u-boot/rsa-mod-exp.h> |
| 22 | |
| 23 | #define UINT64_MULT32(v, multby) (((uint64_t)(v)) * ((uint32_t)(multby))) |
| 24 | |
| 25 | #define get_unaligned_be32(a) fdt32_to_cpu(*(uint32_t *)a) |
| 26 | #define put_unaligned_be32(a, b) (*(uint32_t *)(b) = cpu_to_fdt32(a)) |
| 27 | |
| 28 | /* Default public exponent for backward compatibility */ |
| 29 | #define RSA_DEFAULT_PUBEXP 65537 |
| 30 | |
| 31 | /** |
| 32 | * subtract_modulus() - subtract modulus from the given value |
| 33 | * |
| 34 | * @key: Key containing modulus to subtract |
| 35 | * @num: Number to subtract modulus from, as little endian word array |
| 36 | */ |
| 37 | static void subtract_modulus(const struct rsa_public_key *key, uint32_t num[]) |
| 38 | { |
| 39 | int64_t acc = 0; |
| 40 | uint i; |
| 41 | |
| 42 | for (i = 0; i < key->len; i++) { |
| 43 | acc += (uint64_t)num[i] - key->modulus[i]; |
| 44 | num[i] = (uint32_t)acc; |
| 45 | acc >>= 32; |
| 46 | } |
| 47 | } |
| 48 | |
| 49 | /** |
| 50 | * greater_equal_modulus() - check if a value is >= modulus |
| 51 | * |
| 52 | * @key: Key containing modulus to check |
| 53 | * @num: Number to check against modulus, as little endian word array |
| 54 | * @return 0 if num < modulus, 1 if num >= modulus |
| 55 | */ |
| 56 | static int greater_equal_modulus(const struct rsa_public_key *key, |
| 57 | uint32_t num[]) |
| 58 | { |
| 59 | int i; |
| 60 | |
| 61 | for (i = (int)key->len - 1; i >= 0; i--) { |
| 62 | if (num[i] < key->modulus[i]) |
| 63 | return 0; |
| 64 | if (num[i] > key->modulus[i]) |
| 65 | return 1; |
| 66 | } |
| 67 | |
| 68 | return 1; /* equal */ |
| 69 | } |
| 70 | |
| 71 | /** |
| 72 | * montgomery_mul_add_step() - Perform montgomery multiply-add step |
| 73 | * |
| 74 | * Operation: montgomery result[] += a * b[] / n0inv % modulus |
| 75 | * |
| 76 | * @key: RSA key |
| 77 | * @result: Place to put result, as little endian word array |
| 78 | * @a: Multiplier |
| 79 | * @b: Multiplicand, as little endian word array |
| 80 | */ |
| 81 | static void montgomery_mul_add_step(const struct rsa_public_key *key, |
| 82 | uint32_t result[], const uint32_t a, const uint32_t b[]) |
| 83 | { |
| 84 | uint64_t acc_a, acc_b; |
| 85 | uint32_t d0; |
| 86 | uint i; |
| 87 | |
| 88 | acc_a = (uint64_t)a * b[0] + result[0]; |
| 89 | d0 = (uint32_t)acc_a * key->n0inv; |
| 90 | acc_b = (uint64_t)d0 * key->modulus[0] + (uint32_t)acc_a; |
| 91 | for (i = 1; i < key->len; i++) { |
| 92 | acc_a = (acc_a >> 32) + (uint64_t)a * b[i] + result[i]; |
| 93 | acc_b = (acc_b >> 32) + (uint64_t)d0 * key->modulus[i] + |
| 94 | (uint32_t)acc_a; |
| 95 | result[i - 1] = (uint32_t)acc_b; |
| 96 | } |
| 97 | |
| 98 | acc_a = (acc_a >> 32) + (acc_b >> 32); |
| 99 | |
| 100 | result[i - 1] = (uint32_t)acc_a; |
| 101 | |
| 102 | if (acc_a >> 32) |
| 103 | subtract_modulus(key, result); |
| 104 | } |
| 105 | |
| 106 | /** |
| 107 | * montgomery_mul() - Perform montgomery mutitply |
| 108 | * |
| 109 | * Operation: montgomery result[] = a[] * b[] / n0inv % modulus |
| 110 | * |
| 111 | * @key: RSA key |
| 112 | * @result: Place to put result, as little endian word array |
| 113 | * @a: Multiplier, as little endian word array |
| 114 | * @b: Multiplicand, as little endian word array |
| 115 | */ |
| 116 | static void montgomery_mul(const struct rsa_public_key *key, |
| 117 | uint32_t result[], uint32_t a[], const uint32_t b[]) |
| 118 | { |
| 119 | uint i; |
| 120 | |
| 121 | for (i = 0; i < key->len; ++i) |
| 122 | result[i] = 0; |
| 123 | for (i = 0; i < key->len; ++i) |
| 124 | montgomery_mul_add_step(key, result, a[i], b); |
| 125 | } |
| 126 | |
| 127 | /** |
| 128 | * num_pub_exponent_bits() - Number of bits in the public exponent |
| 129 | * |
| 130 | * @key: RSA key |
| 131 | * @num_bits: Storage for the number of public exponent bits |
| 132 | */ |
| 133 | static int num_public_exponent_bits(const struct rsa_public_key *key, |
| 134 | int *num_bits) |
| 135 | { |
| 136 | uint64_t exponent; |
| 137 | int exponent_bits; |
| 138 | const uint max_bits = (sizeof(exponent) * 8); |
| 139 | |
| 140 | exponent = key->exponent; |
| 141 | exponent_bits = 0; |
| 142 | |
| 143 | if (!exponent) { |
| 144 | *num_bits = exponent_bits; |
| 145 | return 0; |
| 146 | } |
| 147 | |
| 148 | for (exponent_bits = 1; exponent_bits < max_bits + 1; ++exponent_bits) |
| 149 | if (!(exponent >>= 1)) { |
| 150 | *num_bits = exponent_bits; |
| 151 | return 0; |
| 152 | } |
| 153 | |
| 154 | return -EINVAL; |
| 155 | } |
| 156 | |
| 157 | /** |
| 158 | * is_public_exponent_bit_set() - Check if a bit in the public exponent is set |
| 159 | * |
| 160 | * @key: RSA key |
| 161 | * @pos: The bit position to check |
| 162 | */ |
| 163 | static int is_public_exponent_bit_set(const struct rsa_public_key *key, |
| 164 | int pos) |
| 165 | { |
| 166 | return key->exponent & (1ULL << pos); |
| 167 | } |
| 168 | |
| 169 | /** |
| 170 | * pow_mod() - in-place public exponentiation |
| 171 | * |
| 172 | * @key: RSA key |
| 173 | * @inout: Big-endian word array containing value and result |
| 174 | */ |
| 175 | static int pow_mod(const struct rsa_public_key *key, uint32_t *inout) |
| 176 | { |
| 177 | uint32_t *result, *ptr; |
| 178 | uint i; |
| 179 | int j, k; |
| 180 | |
| 181 | /* Sanity check for stack size - key->len is in 32-bit words */ |
| 182 | if (key->len > RSA_MAX_KEY_BITS / 32) { |
| 183 | debug("RSA key words %u exceeds maximum %d\n", key->len, |
| 184 | RSA_MAX_KEY_BITS / 32); |
| 185 | return -EINVAL; |
| 186 | } |
| 187 | |
| 188 | uint32_t val[key->len], acc[key->len], tmp[key->len]; |
| 189 | uint32_t a_scaled[key->len]; |
| 190 | result = tmp; /* Re-use location. */ |
| 191 | |
| 192 | /* Convert from big endian byte array to little endian word array. */ |
| 193 | for (i = 0, ptr = inout + key->len - 1; i < key->len; i++, ptr--) |
| 194 | val[i] = get_unaligned_be32(ptr); |
| 195 | |
| 196 | if (0 != num_public_exponent_bits(key, &k)) |
| 197 | return -EINVAL; |
| 198 | |
| 199 | if (k < 2) { |
| 200 | debug("Public exponent is too short (%d bits, minimum 2)\n", |
| 201 | k); |
| 202 | return -EINVAL; |
| 203 | } |
| 204 | |
| 205 | if (!is_public_exponent_bit_set(key, 0)) { |
| 206 | debug("LSB of RSA public exponent must be set.\n"); |
| 207 | return -EINVAL; |
| 208 | } |
| 209 | |
| 210 | /* the bit at e[k-1] is 1 by definition, so start with: C := M */ |
| 211 | montgomery_mul(key, acc, val, key->rr); /* acc = a * RR / R mod n */ |
| 212 | /* retain scaled version for intermediate use */ |
| 213 | memcpy(a_scaled, acc, key->len * sizeof(a_scaled[0])); |
| 214 | |
| 215 | for (j = k - 2; j > 0; --j) { |
| 216 | montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */ |
| 217 | |
| 218 | if (is_public_exponent_bit_set(key, j)) { |
| 219 | /* acc = tmp * val / R mod n */ |
| 220 | montgomery_mul(key, acc, tmp, a_scaled); |
| 221 | } else { |
| 222 | /* e[j] == 0, copy tmp back to acc for next operation */ |
| 223 | memcpy(acc, tmp, key->len * sizeof(acc[0])); |
| 224 | } |
| 225 | } |
| 226 | |
| 227 | /* the bit at e[0] is always 1 */ |
| 228 | montgomery_mul(key, tmp, acc, acc); /* tmp = acc^2 / R mod n */ |
| 229 | montgomery_mul(key, acc, tmp, val); /* acc = tmp * a / R mod M */ |
| 230 | memcpy(result, acc, key->len * sizeof(result[0])); |
| 231 | |
| 232 | /* Make sure result < mod; result is at most 1x mod too large. */ |
| 233 | if (greater_equal_modulus(key, result)) |
| 234 | subtract_modulus(key, result); |
| 235 | |
| 236 | /* Convert to bigendian byte array */ |
| 237 | for (i = key->len - 1, ptr = inout; (int)i >= 0; i--, ptr++) |
| 238 | put_unaligned_be32(result[i], ptr); |
| 239 | return 0; |
| 240 | } |
| 241 | |
| 242 | static void rsa_convert_big_endian(uint32_t *dst, const uint32_t *src, int len) |
| 243 | { |
| 244 | int i; |
| 245 | |
| 246 | for (i = 0; i < len; i++) |
| 247 | dst[i] = fdt32_to_cpu(src[len - 1 - i]); |
| 248 | } |
| 249 | |
| 250 | int rsa_mod_exp_sw(const uint8_t *sig, uint32_t sig_len, |
| 251 | struct key_prop *prop, uint8_t *out) |
| 252 | { |
| 253 | struct rsa_public_key key; |
| 254 | int ret; |
| 255 | |
| 256 | if (!prop) { |
| 257 | debug("%s: Skipping invalid prop", __func__); |
| 258 | return -EBADF; |
| 259 | } |
| 260 | key.n0inv = prop->n0inv; |
| 261 | key.len = prop->num_bits; |
| 262 | |
| 263 | if (!prop->public_exponent) |
| 264 | key.exponent = RSA_DEFAULT_PUBEXP; |
| 265 | else |
| 266 | key.exponent = |
| 267 | fdt64_to_cpu(*((uint64_t *)(prop->public_exponent))); |
| 268 | |
| 269 | if (!key.len || !prop->modulus || !prop->rr) { |
| 270 | debug("%s: Missing RSA key info", __func__); |
| 271 | return -EFAULT; |
| 272 | } |
| 273 | |
| 274 | /* Sanity check for stack size */ |
| 275 | if (key.len > RSA_MAX_KEY_BITS || key.len < RSA_MIN_KEY_BITS) { |
| 276 | debug("RSA key bits %u outside allowed range %d..%d\n", |
| 277 | key.len, RSA_MIN_KEY_BITS, RSA_MAX_KEY_BITS); |
| 278 | return -EFAULT; |
| 279 | } |
| 280 | key.len /= sizeof(uint32_t) * 8; |
| 281 | uint32_t key1[key.len], key2[key.len]; |
| 282 | |
| 283 | key.modulus = key1; |
| 284 | key.rr = key2; |
| 285 | rsa_convert_big_endian(key.modulus, (uint32_t *)prop->modulus, key.len); |
| 286 | rsa_convert_big_endian(key.rr, (uint32_t *)prop->rr, key.len); |
| 287 | if (!key.modulus || !key.rr) { |
| 288 | debug("%s: Out of memory", __func__); |
| 289 | return -ENOMEM; |
| 290 | } |
| 291 | |
| 292 | uint32_t buf[sig_len / sizeof(uint32_t)]; |
| 293 | |
| 294 | memcpy(buf, sig, sig_len); |
| 295 | |
| 296 | ret = pow_mod(&key, buf); |
| 297 | if (ret) |
| 298 | return ret; |
| 299 | |
| 300 | memcpy(out, buf, sig_len); |
| 301 | |
| 302 | return 0; |
| 303 | } |