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 15 #include <net/mac80211.h> 16 #include "key.h" 17 #include "aes_cmac.h" 18 19 #define AES_BLOCK_SIZE 16 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, u8 *scratch, 39 size_t num_elem, 40 const u8 *addr[], const size_t *len, u8 *mac) 41 { 42 u8 *cbc, *pad; 43 const u8 *pos, *end; 44 size_t i, e, left, total_len; 45 46 cbc = scratch; 47 pad = scratch + AES_BLOCK_SIZE; 48 49 memset(cbc, 0, AES_BLOCK_SIZE); 50 51 total_len = 0; 52 for (e = 0; e < num_elem; e++) 53 total_len += len[e]; 54 left = total_len; 55 56 e = 0; 57 pos = addr[0]; 58 end = pos + len[0]; 59 60 while (left >= AES_BLOCK_SIZE) { 61 for (i = 0; i < AES_BLOCK_SIZE; i++) { 62 cbc[i] ^= *pos++; 63 if (pos >= end) { 64 e++; 65 pos = addr[e]; 66 end = pos + len[e]; 67 } 68 } 69 if (left > AES_BLOCK_SIZE) 70 crypto_cipher_encrypt_one(tfm, cbc, cbc); 71 left -= AES_BLOCK_SIZE; 72 } 73 74 memset(pad, 0, AES_BLOCK_SIZE); 75 crypto_cipher_encrypt_one(tfm, pad, pad); 76 gf_mulx(pad); 77 78 if (left || total_len == 0) { 79 for (i = 0; i < left; i++) { 80 cbc[i] ^= *pos++; 81 if (pos >= end) { 82 e++; 83 pos = addr[e]; 84 end = pos + len[e]; 85 } 86 } 87 cbc[left] ^= 0x80; 88 gf_mulx(pad); 89 } 90 91 for (i = 0; i < AES_BLOCK_SIZE; i++) 92 pad[i] ^= cbc[i]; 93 crypto_cipher_encrypt_one(tfm, pad, pad); 94 memcpy(mac, pad, CMAC_TLEN); 95 } 96 97 98 void ieee80211_aes_cmac(struct crypto_cipher *tfm, u8 *scratch, const u8 *aad, 99 const u8 *data, size_t data_len, u8 *mic) 100 { 101 const u8 *addr[3]; 102 size_t len[3]; 103 u8 zero[CMAC_TLEN]; 104 105 memset(zero, 0, CMAC_TLEN); 106 addr[0] = aad; 107 len[0] = AAD_LEN; 108 addr[1] = data; 109 len[1] = data_len - CMAC_TLEN; 110 addr[2] = zero; 111 len[2] = CMAC_TLEN; 112 113 aes_128_cmac_vector(tfm, scratch, 3, addr, len, mic); 114 } 115 116 117 struct crypto_cipher * ieee80211_aes_cmac_key_setup(const u8 key[]) 118 { 119 struct crypto_cipher *tfm; 120 121 tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC); 122 if (IS_ERR(tfm)) 123 return NULL; 124 125 crypto_cipher_setkey(tfm, key, AES_CMAC_KEY_LEN); 126 127 return tfm; 128 } 129 130 131 void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm) 132 { 133 if (tfm) 134 crypto_free_cipher(tfm); 135 } 136