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/export.h> 14 #include <linux/err.h> 15 #include <crypto/aes.h> 16 17 #include <net/mac80211.h> 18 #include "key.h" 19 #include "aes_cmac.h" 20 21 #define CMAC_TLEN 8 /* CMAC TLen = 64 bits (8 octets) */ 22 #define CMAC_TLEN_256 16 /* CMAC TLen = 128 bits (16 octets) */ 23 #define AAD_LEN 20 24 25 26 static void gf_mulx(u8 *pad) 27 { 28 int i, carry; 29 30 carry = pad[0] & 0x80; 31 for (i = 0; i < AES_BLOCK_SIZE - 1; i++) 32 pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7); 33 pad[AES_BLOCK_SIZE - 1] <<= 1; 34 if (carry) 35 pad[AES_BLOCK_SIZE - 1] ^= 0x87; 36 } 37 38 static void aes_cmac_vector(struct crypto_cipher *tfm, size_t num_elem, 39 const u8 *addr[], const size_t *len, u8 *mac, 40 size_t mac_len) 41 { 42 u8 cbc[AES_BLOCK_SIZE], pad[AES_BLOCK_SIZE]; 43 const u8 *pos, *end; 44 size_t i, e, left, total_len; 45 46 memset(cbc, 0, AES_BLOCK_SIZE); 47 48 total_len = 0; 49 for (e = 0; e < num_elem; e++) 50 total_len += len[e]; 51 left = total_len; 52 53 e = 0; 54 pos = addr[0]; 55 end = pos + len[0]; 56 57 while (left >= AES_BLOCK_SIZE) { 58 for (i = 0; i < AES_BLOCK_SIZE; i++) { 59 cbc[i] ^= *pos++; 60 if (pos >= end) { 61 e++; 62 pos = addr[e]; 63 end = pos + len[e]; 64 } 65 } 66 if (left > AES_BLOCK_SIZE) 67 crypto_cipher_encrypt_one(tfm, cbc, cbc); 68 left -= AES_BLOCK_SIZE; 69 } 70 71 memset(pad, 0, AES_BLOCK_SIZE); 72 crypto_cipher_encrypt_one(tfm, pad, pad); 73 gf_mulx(pad); 74 75 if (left || total_len == 0) { 76 for (i = 0; i < left; i++) { 77 cbc[i] ^= *pos++; 78 if (pos >= end) { 79 e++; 80 pos = addr[e]; 81 end = pos + len[e]; 82 } 83 } 84 cbc[left] ^= 0x80; 85 gf_mulx(pad); 86 } 87 88 for (i = 0; i < AES_BLOCK_SIZE; i++) 89 pad[i] ^= cbc[i]; 90 crypto_cipher_encrypt_one(tfm, pad, pad); 91 memcpy(mac, pad, mac_len); 92 } 93 94 95 void ieee80211_aes_cmac(struct crypto_cipher *tfm, const u8 *aad, 96 const u8 *data, size_t data_len, u8 *mic) 97 { 98 const u8 *addr[3]; 99 size_t len[3]; 100 u8 zero[CMAC_TLEN]; 101 102 memset(zero, 0, CMAC_TLEN); 103 addr[0] = aad; 104 len[0] = AAD_LEN; 105 addr[1] = data; 106 len[1] = data_len - CMAC_TLEN; 107 addr[2] = zero; 108 len[2] = CMAC_TLEN; 109 110 aes_cmac_vector(tfm, 3, addr, len, mic, CMAC_TLEN); 111 } 112 113 void ieee80211_aes_cmac_256(struct crypto_cipher *tfm, const u8 *aad, 114 const u8 *data, size_t data_len, u8 *mic) 115 { 116 const u8 *addr[3]; 117 size_t len[3]; 118 u8 zero[CMAC_TLEN_256]; 119 120 memset(zero, 0, CMAC_TLEN_256); 121 addr[0] = aad; 122 len[0] = AAD_LEN; 123 addr[1] = data; 124 len[1] = data_len - CMAC_TLEN_256; 125 addr[2] = zero; 126 len[2] = CMAC_TLEN_256; 127 128 aes_cmac_vector(tfm, 3, addr, len, mic, CMAC_TLEN_256); 129 } 130 131 struct crypto_cipher *ieee80211_aes_cmac_key_setup(const u8 key[], 132 size_t key_len) 133 { 134 struct crypto_cipher *tfm; 135 136 tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC); 137 if (!IS_ERR(tfm)) 138 crypto_cipher_setkey(tfm, key, key_len); 139 140 return tfm; 141 } 142 143 144 void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm) 145 { 146 crypto_free_cipher(tfm); 147 } 148