1 /* 2 * AES SIV (RFC 5297) 3 * Copyright (c) 2013 Cozybit, Inc. 4 * 5 * This software may be distributed under the terms of the BSD license. 6 * See README for more details. 7 */ 8 9 #include "includes.h" 10 11 #include "common.h" 12 #include "aes.h" 13 #include "aes_wrap.h" 14 #include "aes_siv.h" 15 16 17 static const u8 zero[AES_BLOCK_SIZE]; 18 19 20 static void dbl(u8 *pad) 21 { 22 int i, carry; 23 24 carry = pad[0] & 0x80; 25 for (i = 0; i < AES_BLOCK_SIZE - 1; i++) 26 pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7); 27 pad[AES_BLOCK_SIZE - 1] <<= 1; 28 if (carry) 29 pad[AES_BLOCK_SIZE - 1] ^= 0x87; 30 } 31 32 33 static void xor(u8 *a, const u8 *b) 34 { 35 int i; 36 37 for (i = 0; i < AES_BLOCK_SIZE; i++) 38 *a++ ^= *b++; 39 } 40 41 42 static void xorend(u8 *a, int alen, const u8 *b, int blen) 43 { 44 int i; 45 46 if (alen < blen) 47 return; 48 49 for (i = 0; i < blen; i++) 50 a[alen - blen + i] ^= b[i]; 51 } 52 53 54 static void pad_block(u8 *pad, const u8 *addr, size_t len) 55 { 56 os_memset(pad, 0, AES_BLOCK_SIZE); 57 os_memcpy(pad, addr, len); 58 59 if (len < AES_BLOCK_SIZE) 60 pad[len] = 0x80; 61 } 62 63 64 static int aes_s2v(const u8 *key, size_t num_elem, const u8 *addr[], 65 size_t *len, u8 *mac) 66 { 67 u8 tmp[AES_BLOCK_SIZE], tmp2[AES_BLOCK_SIZE]; 68 u8 *buf = NULL; 69 int ret; 70 size_t i; 71 72 if (!num_elem) { 73 os_memcpy(tmp, zero, sizeof(zero)); 74 tmp[AES_BLOCK_SIZE - 1] = 1; 75 return omac1_aes_128(key, tmp, sizeof(tmp), mac); 76 } 77 78 ret = omac1_aes_128(key, zero, sizeof(zero), tmp); 79 if (ret) 80 return ret; 81 82 for (i = 0; i < num_elem - 1; i++) { 83 ret = omac1_aes_128(key, addr[i], len[i], tmp2); 84 if (ret) 85 return ret; 86 87 dbl(tmp); 88 xor(tmp, tmp2); 89 } 90 if (len[i] >= AES_BLOCK_SIZE) { 91 buf = os_malloc(len[i]); 92 if (!buf) 93 return -ENOMEM; 94 95 os_memcpy(buf, addr[i], len[i]); 96 xorend(buf, len[i], tmp, AES_BLOCK_SIZE); 97 ret = omac1_aes_128(key, buf, len[i], mac); 98 bin_clear_free(buf, len[i]); 99 return ret; 100 } 101 102 dbl(tmp); 103 pad_block(tmp2, addr[i], len[i]); 104 xor(tmp, tmp2); 105 106 return omac1_aes_128(key, tmp, sizeof(tmp), mac); 107 } 108 109 110 int aes_siv_encrypt(const u8 *key, const u8 *pw, 111 size_t pwlen, size_t num_elem, 112 const u8 *addr[], const size_t *len, u8 *out) 113 { 114 const u8 *_addr[6]; 115 size_t _len[6]; 116 const u8 *k1 = key, *k2 = key + 16; 117 u8 v[AES_BLOCK_SIZE]; 118 size_t i; 119 u8 *iv, *crypt_pw; 120 121 if (num_elem > ARRAY_SIZE(_addr) - 1) 122 return -1; 123 124 for (i = 0; i < num_elem; i++) { 125 _addr[i] = addr[i]; 126 _len[i] = len[i]; 127 } 128 _addr[num_elem] = pw; 129 _len[num_elem] = pwlen; 130 131 if (aes_s2v(k1, num_elem + 1, _addr, _len, v)) 132 return -1; 133 134 iv = out; 135 crypt_pw = out + AES_BLOCK_SIZE; 136 137 os_memcpy(iv, v, AES_BLOCK_SIZE); 138 os_memcpy(crypt_pw, pw, pwlen); 139 140 /* zero out 63rd and 31st bits of ctr (from right) */ 141 v[8] &= 0x7f; 142 v[12] &= 0x7f; 143 return aes_128_ctr_encrypt(k2, v, crypt_pw, pwlen); 144 } 145 146 147 int aes_siv_decrypt(const u8 *key, const u8 *iv_crypt, size_t iv_c_len, 148 size_t num_elem, const u8 *addr[], const size_t *len, 149 u8 *out) 150 { 151 const u8 *_addr[6]; 152 size_t _len[6]; 153 const u8 *k1 = key, *k2 = key + 16; 154 size_t crypt_len; 155 size_t i; 156 int ret; 157 u8 iv[AES_BLOCK_SIZE]; 158 u8 check[AES_BLOCK_SIZE]; 159 160 if (iv_c_len < AES_BLOCK_SIZE || num_elem > ARRAY_SIZE(_addr) - 1) 161 return -1; 162 crypt_len = iv_c_len - AES_BLOCK_SIZE; 163 164 for (i = 0; i < num_elem; i++) { 165 _addr[i] = addr[i]; 166 _len[i] = len[i]; 167 } 168 _addr[num_elem] = out; 169 _len[num_elem] = crypt_len; 170 171 os_memcpy(iv, iv_crypt, AES_BLOCK_SIZE); 172 os_memcpy(out, iv_crypt + AES_BLOCK_SIZE, crypt_len); 173 174 iv[8] &= 0x7f; 175 iv[12] &= 0x7f; 176 177 ret = aes_128_ctr_encrypt(k2, iv, out, crypt_len); 178 if (ret) 179 return ret; 180 181 ret = aes_s2v(k1, num_elem + 1, _addr, _len, check); 182 if (ret) 183 return ret; 184 if (os_memcmp(check, iv_crypt, AES_BLOCK_SIZE) == 0) 185 return 0; 186 187 return -1; 188 } 189
