Doug Zongker | 35d9ad5 | 2012-07-25 12:08:33 -0700 | [diff] [blame] | 1 | /* rsa_e_f4.c |
| 2 | ** |
| 3 | ** Copyright 2012, The Android Open Source Project |
| 4 | ** |
| 5 | ** Redistribution and use in source and binary forms, with or without |
| 6 | ** modification, are permitted provided that the following conditions are met: |
| 7 | ** * Redistributions of source code must retain the above copyright |
| 8 | ** notice, this list of conditions and the following disclaimer. |
| 9 | ** * Redistributions in binary form must reproduce the above copyright |
| 10 | ** notice, this list of conditions and the following disclaimer in the |
| 11 | ** documentation and/or other materials provided with the distribution. |
| 12 | ** * Neither the name of Google Inc. nor the names of its contributors may |
| 13 | ** be used to endorse or promote products derived from this software |
| 14 | ** without specific prior written permission. |
| 15 | ** |
| 16 | ** THIS SOFTWARE IS PROVIDED BY Google Inc. ``AS IS'' AND ANY EXPRESS OR |
| 17 | ** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| 18 | ** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
| 19 | ** EVENT SHALL Google Inc. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 20 | ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| 21 | ** PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
| 22 | ** OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| 23 | ** WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
| 24 | ** OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| 25 | ** ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 26 | */ |
| 27 | |
| 28 | #include "mincrypt/rsa.h" |
| 29 | #include "mincrypt/sha.h" |
| 30 | |
| 31 | // a[] -= mod |
| 32 | static void subM(const RSAPublicKey* key, |
| 33 | uint32_t* a) { |
| 34 | int64_t A = 0; |
| 35 | int i; |
| 36 | for (i = 0; i < key->len; ++i) { |
| 37 | A += (uint64_t)a[i] - key->n[i]; |
| 38 | a[i] = (uint32_t)A; |
| 39 | A >>= 32; |
| 40 | } |
| 41 | } |
| 42 | |
| 43 | // return a[] >= mod |
| 44 | static int geM(const RSAPublicKey* key, |
| 45 | const uint32_t* a) { |
| 46 | int i; |
| 47 | for (i = key->len; i;) { |
| 48 | --i; |
| 49 | if (a[i] < key->n[i]) return 0; |
| 50 | if (a[i] > key->n[i]) return 1; |
| 51 | } |
| 52 | return 1; // equal |
| 53 | } |
| 54 | |
| 55 | // montgomery c[] += a * b[] / R % mod |
| 56 | static void montMulAdd(const RSAPublicKey* key, |
| 57 | uint32_t* c, |
| 58 | const uint32_t a, |
| 59 | const uint32_t* b) { |
| 60 | uint64_t A = (uint64_t)a * b[0] + c[0]; |
| 61 | uint32_t d0 = (uint32_t)A * key->n0inv; |
| 62 | uint64_t B = (uint64_t)d0 * key->n[0] + (uint32_t)A; |
| 63 | int i; |
| 64 | |
| 65 | for (i = 1; i < key->len; ++i) { |
| 66 | A = (A >> 32) + (uint64_t)a * b[i] + c[i]; |
| 67 | B = (B >> 32) + (uint64_t)d0 * key->n[i] + (uint32_t)A; |
| 68 | c[i - 1] = (uint32_t)B; |
| 69 | } |
| 70 | |
| 71 | A = (A >> 32) + (B >> 32); |
| 72 | |
| 73 | c[i - 1] = (uint32_t)A; |
| 74 | |
| 75 | if (A >> 32) { |
| 76 | subM(key, c); |
| 77 | } |
| 78 | } |
| 79 | |
| 80 | // montgomery c[] = a[] * b[] / R % mod |
| 81 | static void montMul(const RSAPublicKey* key, |
| 82 | uint32_t* c, |
| 83 | const uint32_t* a, |
| 84 | const uint32_t* b) { |
| 85 | int i; |
| 86 | for (i = 0; i < key->len; ++i) { |
| 87 | c[i] = 0; |
| 88 | } |
| 89 | for (i = 0; i < key->len; ++i) { |
| 90 | montMulAdd(key, c, a[i], b); |
| 91 | } |
| 92 | } |
| 93 | |
| 94 | // In-place public exponentiation. |
| 95 | // Input and output big-endian byte array in inout. |
| 96 | static void modpowF4(const RSAPublicKey* key, |
| 97 | uint8_t* inout) { |
| 98 | uint32_t a[RSANUMWORDS]; |
| 99 | uint32_t aR[RSANUMWORDS]; |
| 100 | uint32_t aaR[RSANUMWORDS]; |
| 101 | uint32_t* aaa = aaR; // Re-use location. |
| 102 | int i; |
| 103 | |
| 104 | // Convert from big endian byte array to little endian word array. |
| 105 | for (i = 0; i < key->len; ++i) { |
| 106 | uint32_t tmp = |
| 107 | (inout[((key->len - 1 - i) * 4) + 0] << 24) | |
| 108 | (inout[((key->len - 1 - i) * 4) + 1] << 16) | |
| 109 | (inout[((key->len - 1 - i) * 4) + 2] << 8) | |
| 110 | (inout[((key->len - 1 - i) * 4) + 3] << 0); |
| 111 | a[i] = tmp; |
| 112 | } |
| 113 | |
| 114 | montMul(key, aR, a, key->rr); // aR = a * RR / R mod M |
| 115 | for (i = 0; i < 16; i += 2) { |
| 116 | montMul(key, aaR, aR, aR); // aaR = aR * aR / R mod M |
| 117 | montMul(key, aR, aaR, aaR); // aR = aaR * aaR / R mod M |
| 118 | } |
| 119 | montMul(key, aaa, aR, a); // aaa = aR * a / R mod M |
| 120 | |
| 121 | // Make sure aaa < mod; aaa is at most 1x mod too large. |
| 122 | if (geM(key, aaa)) { |
| 123 | subM(key, aaa); |
| 124 | } |
| 125 | |
| 126 | // Convert to bigendian byte array |
| 127 | for (i = key->len - 1; i >= 0; --i) { |
| 128 | uint32_t tmp = aaa[i]; |
| 129 | *inout++ = tmp >> 24; |
| 130 | *inout++ = tmp >> 16; |
| 131 | *inout++ = tmp >> 8; |
| 132 | *inout++ = tmp >> 0; |
| 133 | } |
| 134 | } |
| 135 | |
| 136 | // Expected PKCS1.5 signature padding bytes, for a keytool RSA signature. |
| 137 | // Has the 0-length optional parameter encoded in the ASN1 (as opposed to the |
| 138 | // other flavor which omits the optional parameter entirely). This code does not |
| 139 | // accept signatures without the optional parameter. |
| 140 | /* |
| 141 | static const uint8_t padding[RSANUMBYTES] = { |
| 142 | 0x00,0x01,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2b,0x0e,0x03,0x02,0x1a,0x05,0x00,0x04,0x14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 |
| 143 | }; |
| 144 | */ |
| 145 | |
| 146 | // SHA-1 of PKCS1.5 signature padding for 2048 bit, as above. |
| 147 | // At the location of the bytes of the hash all 00 are hashed. |
| 148 | static const uint8_t kExpectedPadShaRsa2048[SHA_DIGEST_SIZE] = { |
| 149 | 0xdc, 0xbd, 0xbe, 0x42, 0xd5, 0xf5, 0xa7, 0x2e, 0x6e, 0xfc, |
| 150 | 0xf5, 0x5d, 0xaf, 0x9d, 0xea, 0x68, 0x7c, 0xfb, 0xf1, 0x67 |
| 151 | }; |
| 152 | |
| 153 | // Verify a 2048 bit RSA e=65537 PKCS1.5 signature against an expected |
| 154 | // SHA-1 hash. Returns 0 on failure, 1 on success. |
| 155 | int RSA_e_f4_verify(const RSAPublicKey* key, |
| 156 | const uint8_t* signature, |
| 157 | const int len, |
| 158 | const uint8_t* sha) { |
| 159 | uint8_t buf[RSANUMBYTES]; |
| 160 | int i; |
| 161 | |
| 162 | if (key->len != RSANUMWORDS) { |
| 163 | return 0; // Wrong key passed in. |
| 164 | } |
| 165 | |
| 166 | if (len != sizeof(buf)) { |
| 167 | return 0; // Wrong input length. |
| 168 | } |
| 169 | |
| 170 | if (key->exponent != 65537) { |
| 171 | return 0; // Wrong exponent. |
| 172 | } |
| 173 | |
| 174 | for (i = 0; i < len; ++i) { // Copy input to local workspace. |
| 175 | buf[i] = signature[i]; |
| 176 | } |
| 177 | |
| 178 | modpowF4(key, buf); // In-place exponentiation. |
| 179 | |
| 180 | // Xor sha portion, so it all becomes 00 iff equal. |
| 181 | for (i = len - SHA_DIGEST_SIZE; i < len; ++i) { |
| 182 | buf[i] ^= *sha++; |
| 183 | } |
| 184 | |
| 185 | // Hash resulting buf, in-place. |
| 186 | SHA(buf, len, buf); |
| 187 | |
| 188 | // Compare against expected hash value. |
| 189 | for (i = 0; i < SHA_DIGEST_SIZE; ++i) { |
| 190 | if (buf[i] != kExpectedPadShaRsa2048[i]) { |
| 191 | return 0; |
| 192 | } |
| 193 | } |
| 194 | |
| 195 | return 1; // All checked out OK. |
| 196 | } |