1 /* 2 * AES-128-CMAC with TLen 16 for IEEE 802.11w BIP 3 * Copyright 2008, Jouni Malinen <j@w1.fi> 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License version 2 as 7 * published by the Free Software Foundation. 8 */ 9 10 #include <linux/kernel.h> 11 #include <linux/types.h> 12 #include <linux/crypto.h> 13 #include <linux/err.h> 14 #include <crypto/aes.h> 15 16 #include <net/mac80211.h> 17 #include "key.h" 18 #include "aes_cmac.h" 19 20 #define AES_CMAC_KEY_LEN 16 21 #define CMAC_TLEN 8 /* CMAC TLen = 64 bits (8 octets) */ 22 #define AAD_LEN 20 23 24 25 static void gf_mulx(u8 *pad) 26 { 27 int i, carry; 28 29 carry = pad[0] & 0x80; 30 for (i = 0; i < AES_BLOCK_SIZE - 1; i++) 31 pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7); 32 pad[AES_BLOCK_SIZE - 1] <<= 1; 33 if (carry) 34 pad[AES_BLOCK_SIZE - 1] ^= 0x87; 35 } 36 37 38 static void aes_128_cmac_vector(struct crypto_cipher *tfm, size_t num_elem, 39 const u8 *addr[], const size_t *len, u8 *mac) 40 { 41 u8 cbc[AES_BLOCK_SIZE], pad[AES_BLOCK_SIZE]; 42 const u8 *pos, *end; 43 size_t i, e, left, total_len; 44 45 memset(cbc, 0, AES_BLOCK_SIZE); 46 47 total_len = 0; 48 for (e = 0; e < num_elem; e++) 49 total_len += len[e]; 50 left = total_len; 51 52 e = 0; 53 pos = addr[0]; 54 end = pos + len[0]; 55 56 while (left >= AES_BLOCK_SIZE) { 57 for (i = 0; i < AES_BLOCK_SIZE; i++) { 58 cbc[i] ^= *pos++; 59 if (pos >= end) { 60 e++; 61 pos = addr[e]; 62 end = pos + len[e]; 63 } 64 } 65 if (left > AES_BLOCK_SIZE) 66 crypto_cipher_encrypt_one(tfm, cbc, cbc); 67 left -= AES_BLOCK_SIZE; 68 } 69 70 memset(pad, 0, AES_BLOCK_SIZE); 71 crypto_cipher_encrypt_one(tfm, pad, pad); 72 gf_mulx(pad); 73 74 if (left || total_len == 0) { 75 for (i = 0; i < left; i++) { 76 cbc[i] ^= *pos++; 77 if (pos >= end) { 78 e++; 79 pos = addr[e]; 80 end = pos + len[e]; 81 } 82 } 83 cbc[left] ^= 0x80; 84 gf_mulx(pad); 85 } 86 87 for (i = 0; i < AES_BLOCK_SIZE; i++) 88 pad[i] ^= cbc[i]; 89 crypto_cipher_encrypt_one(tfm, pad, pad); 90 memcpy(mac, pad, CMAC_TLEN); 91 } 92 93 94 void ieee80211_aes_cmac(struct crypto_cipher *tfm, const u8 *aad, 95 const u8 *data, size_t data_len, u8 *mic) 96 { 97 const u8 *addr[3]; 98 size_t len[3]; 99 u8 zero[CMAC_TLEN]; 100 101 memset(zero, 0, CMAC_TLEN); 102 addr[0] = aad; 103 len[0] = AAD_LEN; 104 addr[1] = data; 105 len[1] = data_len - CMAC_TLEN; 106 addr[2] = zero; 107 len[2] = CMAC_TLEN; 108 109 aes_128_cmac_vector(tfm, 3, addr, len, mic); 110 } 111 112 113 struct crypto_cipher * ieee80211_aes_cmac_key_setup(const u8 key[]) 114 { 115 struct crypto_cipher *tfm; 116 117 tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC); 118 if (!IS_ERR(tfm)) 119 crypto_cipher_setkey(tfm, key, AES_CMAC_KEY_LEN); 120 121 return tfm; 122 } 123 124 125 void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm) 126 { 127 crypto_free_cipher(tfm); 128 } 129 130 void ieee80211_aes_cmac_calculate_k1_k2(struct ieee80211_key_conf *keyconf, 131 u8 *k1, u8 *k2) 132 { 133 u8 l[AES_BLOCK_SIZE] = {}; 134 struct ieee80211_key *key = 135 container_of(keyconf, struct ieee80211_key, conf); 136 137 crypto_cipher_encrypt_one(key->u.aes_cmac.tfm, l, l); 138 139 memcpy(k1, l, AES_BLOCK_SIZE); 140 gf_mulx(k1); 141 142 memcpy(k2, k1, AES_BLOCK_SIZE); 143 gf_mulx(k2); 144 } 145 EXPORT_SYMBOL(ieee80211_aes_cmac_calculate_k1_k2); 146