1252190Srpaulo/* 2252190Srpaulo * Counter with CBC-MAC (CCM) with AES 3252190Srpaulo * 4252190Srpaulo * Copyright (c) 2010-2012, Jouni Malinen <j@w1.fi> 5252190Srpaulo * 6252190Srpaulo * This software may be distributed under the terms of the BSD license. 7252190Srpaulo * See README for more details. 8252190Srpaulo */ 9252190Srpaulo 10252190Srpaulo#include "includes.h" 11252190Srpaulo 12252190Srpaulo#include "common.h" 13252190Srpaulo#include "aes.h" 14252190Srpaulo#include "aes_wrap.h" 15252190Srpaulo 16252190Srpaulo 17252190Srpaulostatic void xor_aes_block(u8 *dst, const u8 *src) 18252190Srpaulo{ 19252190Srpaulo u32 *d = (u32 *) dst; 20252190Srpaulo u32 *s = (u32 *) src; 21252190Srpaulo *d++ ^= *s++; 22252190Srpaulo *d++ ^= *s++; 23252190Srpaulo *d++ ^= *s++; 24252190Srpaulo *d++ ^= *s++; 25252190Srpaulo} 26252190Srpaulo 27252190Srpaulo 28252190Srpaulostatic void aes_ccm_auth_start(void *aes, size_t M, size_t L, const u8 *nonce, 29252190Srpaulo const u8 *aad, size_t aad_len, size_t plain_len, 30252190Srpaulo u8 *x) 31252190Srpaulo{ 32252190Srpaulo u8 aad_buf[2 * AES_BLOCK_SIZE]; 33252190Srpaulo u8 b[AES_BLOCK_SIZE]; 34252190Srpaulo 35252190Srpaulo /* Authentication */ 36252190Srpaulo /* B_0: Flags | Nonce N | l(m) */ 37252190Srpaulo b[0] = aad_len ? 0x40 : 0 /* Adata */; 38252190Srpaulo b[0] |= (((M - 2) / 2) /* M' */ << 3); 39252190Srpaulo b[0] |= (L - 1) /* L' */; 40252190Srpaulo os_memcpy(&b[1], nonce, 15 - L); 41252190Srpaulo WPA_PUT_BE16(&b[AES_BLOCK_SIZE - L], plain_len); 42252190Srpaulo 43252190Srpaulo wpa_hexdump_key(MSG_EXCESSIVE, "CCM B_0", b, AES_BLOCK_SIZE); 44252190Srpaulo aes_encrypt(aes, b, x); /* X_1 = E(K, B_0) */ 45252190Srpaulo 46252190Srpaulo if (!aad_len) 47252190Srpaulo return; 48252190Srpaulo 49252190Srpaulo WPA_PUT_BE16(aad_buf, aad_len); 50252190Srpaulo os_memcpy(aad_buf + 2, aad, aad_len); 51252190Srpaulo os_memset(aad_buf + 2 + aad_len, 0, sizeof(aad_buf) - 2 - aad_len); 52252190Srpaulo 53252190Srpaulo xor_aes_block(aad_buf, x); 54252190Srpaulo aes_encrypt(aes, aad_buf, x); /* X_2 = E(K, X_1 XOR B_1) */ 55252190Srpaulo 56252190Srpaulo if (aad_len > AES_BLOCK_SIZE - 2) { 57252190Srpaulo xor_aes_block(&aad_buf[AES_BLOCK_SIZE], x); 58252190Srpaulo /* X_3 = E(K, X_2 XOR B_2) */ 59252190Srpaulo aes_encrypt(aes, &aad_buf[AES_BLOCK_SIZE], x); 60252190Srpaulo } 61252190Srpaulo} 62252190Srpaulo 63252190Srpaulo 64252190Srpaulostatic void aes_ccm_auth(void *aes, const u8 *data, size_t len, u8 *x) 65252190Srpaulo{ 66252190Srpaulo size_t last = len % AES_BLOCK_SIZE; 67252190Srpaulo size_t i; 68252190Srpaulo 69252190Srpaulo for (i = 0; i < len / AES_BLOCK_SIZE; i++) { 70252190Srpaulo /* X_i+1 = E(K, X_i XOR B_i) */ 71252190Srpaulo xor_aes_block(x, data); 72252190Srpaulo data += AES_BLOCK_SIZE; 73252190Srpaulo aes_encrypt(aes, x, x); 74252190Srpaulo } 75252190Srpaulo if (last) { 76252190Srpaulo /* XOR zero-padded last block */ 77252190Srpaulo for (i = 0; i < last; i++) 78252190Srpaulo x[i] ^= *data++; 79252190Srpaulo aes_encrypt(aes, x, x); 80252190Srpaulo } 81252190Srpaulo} 82252190Srpaulo 83252190Srpaulo 84252190Srpaulostatic void aes_ccm_encr_start(size_t L, const u8 *nonce, u8 *a) 85252190Srpaulo{ 86252190Srpaulo /* A_i = Flags | Nonce N | Counter i */ 87252190Srpaulo a[0] = L - 1; /* Flags = L' */ 88252190Srpaulo os_memcpy(&a[1], nonce, 15 - L); 89252190Srpaulo} 90252190Srpaulo 91252190Srpaulo 92252190Srpaulostatic void aes_ccm_encr(void *aes, size_t L, const u8 *in, size_t len, u8 *out, 93252190Srpaulo u8 *a) 94252190Srpaulo{ 95252190Srpaulo size_t last = len % AES_BLOCK_SIZE; 96252190Srpaulo size_t i; 97252190Srpaulo 98252190Srpaulo /* crypt = msg XOR (S_1 | S_2 | ... | S_n) */ 99252190Srpaulo for (i = 1; i <= len / AES_BLOCK_SIZE; i++) { 100252190Srpaulo WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i); 101252190Srpaulo /* S_i = E(K, A_i) */ 102252190Srpaulo aes_encrypt(aes, a, out); 103252190Srpaulo xor_aes_block(out, in); 104252190Srpaulo out += AES_BLOCK_SIZE; 105252190Srpaulo in += AES_BLOCK_SIZE; 106252190Srpaulo } 107252190Srpaulo if (last) { 108252190Srpaulo WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i); 109252190Srpaulo aes_encrypt(aes, a, out); 110252190Srpaulo /* XOR zero-padded last block */ 111252190Srpaulo for (i = 0; i < last; i++) 112252190Srpaulo *out++ ^= *in++; 113252190Srpaulo } 114252190Srpaulo} 115252190Srpaulo 116252190Srpaulo 117252190Srpaulostatic void aes_ccm_encr_auth(void *aes, size_t M, u8 *x, u8 *a, u8 *auth) 118252190Srpaulo{ 119252190Srpaulo size_t i; 120252190Srpaulo u8 tmp[AES_BLOCK_SIZE]; 121252190Srpaulo 122252190Srpaulo wpa_hexdump_key(MSG_EXCESSIVE, "CCM T", x, M); 123252190Srpaulo /* U = T XOR S_0; S_0 = E(K, A_0) */ 124252190Srpaulo WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0); 125252190Srpaulo aes_encrypt(aes, a, tmp); 126252190Srpaulo for (i = 0; i < M; i++) 127252190Srpaulo auth[i] = x[i] ^ tmp[i]; 128252190Srpaulo wpa_hexdump_key(MSG_EXCESSIVE, "CCM U", auth, M); 129252190Srpaulo} 130252190Srpaulo 131252190Srpaulo 132252190Srpaulostatic void aes_ccm_decr_auth(void *aes, size_t M, u8 *a, const u8 *auth, u8 *t) 133252190Srpaulo{ 134252190Srpaulo size_t i; 135252190Srpaulo u8 tmp[AES_BLOCK_SIZE]; 136252190Srpaulo 137252190Srpaulo wpa_hexdump_key(MSG_EXCESSIVE, "CCM U", auth, M); 138252190Srpaulo /* U = T XOR S_0; S_0 = E(K, A_0) */ 139252190Srpaulo WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0); 140252190Srpaulo aes_encrypt(aes, a, tmp); 141252190Srpaulo for (i = 0; i < M; i++) 142252190Srpaulo t[i] = auth[i] ^ tmp[i]; 143252190Srpaulo wpa_hexdump_key(MSG_EXCESSIVE, "CCM T", t, M); 144252190Srpaulo} 145252190Srpaulo 146252190Srpaulo 147252190Srpaulo/* AES-CCM with fixed L=2 and aad_len <= 30 assumption */ 148252190Srpauloint aes_ccm_ae(const u8 *key, size_t key_len, const u8 *nonce, 149252190Srpaulo size_t M, const u8 *plain, size_t plain_len, 150252190Srpaulo const u8 *aad, size_t aad_len, u8 *crypt, u8 *auth) 151252190Srpaulo{ 152252190Srpaulo const size_t L = 2; 153252190Srpaulo void *aes; 154252190Srpaulo u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE]; 155252190Srpaulo 156252190Srpaulo if (aad_len > 30 || M > AES_BLOCK_SIZE) 157252190Srpaulo return -1; 158252190Srpaulo 159252190Srpaulo aes = aes_encrypt_init(key, key_len); 160252190Srpaulo if (aes == NULL) 161252190Srpaulo return -1; 162252190Srpaulo 163252190Srpaulo aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, plain_len, x); 164252190Srpaulo aes_ccm_auth(aes, plain, plain_len, x); 165252190Srpaulo 166252190Srpaulo /* Encryption */ 167252190Srpaulo aes_ccm_encr_start(L, nonce, a); 168252190Srpaulo aes_ccm_encr(aes, L, plain, plain_len, crypt, a); 169252190Srpaulo aes_ccm_encr_auth(aes, M, x, a, auth); 170252190Srpaulo 171252190Srpaulo aes_encrypt_deinit(aes); 172252190Srpaulo 173252190Srpaulo return 0; 174252190Srpaulo} 175252190Srpaulo 176252190Srpaulo 177252190Srpaulo/* AES-CCM with fixed L=2 and aad_len <= 30 assumption */ 178252190Srpauloint aes_ccm_ad(const u8 *key, size_t key_len, const u8 *nonce, 179252190Srpaulo size_t M, const u8 *crypt, size_t crypt_len, 180252190Srpaulo const u8 *aad, size_t aad_len, const u8 *auth, u8 *plain) 181252190Srpaulo{ 182252190Srpaulo const size_t L = 2; 183252190Srpaulo void *aes; 184252190Srpaulo u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE]; 185252190Srpaulo u8 t[AES_BLOCK_SIZE]; 186252190Srpaulo 187252190Srpaulo if (aad_len > 30 || M > AES_BLOCK_SIZE) 188252190Srpaulo return -1; 189252190Srpaulo 190252190Srpaulo aes = aes_encrypt_init(key, key_len); 191252190Srpaulo if (aes == NULL) 192252190Srpaulo return -1; 193252190Srpaulo 194252190Srpaulo /* Decryption */ 195252190Srpaulo aes_ccm_encr_start(L, nonce, a); 196252190Srpaulo aes_ccm_decr_auth(aes, M, a, auth, t); 197252190Srpaulo 198252190Srpaulo /* plaintext = msg XOR (S_1 | S_2 | ... | S_n) */ 199252190Srpaulo aes_ccm_encr(aes, L, crypt, crypt_len, plain, a); 200252190Srpaulo 201252190Srpaulo aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, crypt_len, x); 202252190Srpaulo aes_ccm_auth(aes, plain, crypt_len, x); 203252190Srpaulo 204252190Srpaulo aes_encrypt_deinit(aes); 205252190Srpaulo 206252190Srpaulo if (os_memcmp(x, t, M) != 0) { 207252190Srpaulo wpa_printf(MSG_EXCESSIVE, "CCM: Auth mismatch"); 208252190Srpaulo return -1; 209252190Srpaulo } 210252190Srpaulo 211252190Srpaulo return 0; 212252190Srpaulo} 213