1 /* 2 * aes-ccm-glue.c - AES-CCM transform for ARMv8 with Crypto Extensions 3 * 4 * Copyright (C) 2013 - 2014 Linaro Ltd <ard.biesheuvel@linaro.org> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 */ 10 11 #include <asm/neon.h> 12 #include <asm/unaligned.h> 13 #include <crypto/aes.h> 14 #include <crypto/scatterwalk.h> 15 #include <crypto/internal/aead.h> 16 #include <crypto/internal/skcipher.h> 17 #include <linux/module.h> 18 19 #include "aes-ce-setkey.h" 20 21 static int num_rounds(struct crypto_aes_ctx *ctx) 22 { 23 /* 24 * # of rounds specified by AES: 25 * 128 bit key 10 rounds 26 * 192 bit key 12 rounds 27 * 256 bit key 14 rounds 28 * => n byte key => 6 + (n/4) rounds 29 */ 30 return 6 + ctx->key_length / 4; 31 } 32 33 asmlinkage void ce_aes_ccm_auth_data(u8 mac[], u8 const in[], u32 abytes, 34 u32 *macp, u32 const rk[], u32 rounds); 35 36 asmlinkage void ce_aes_ccm_encrypt(u8 out[], u8 const in[], u32 cbytes, 37 u32 const rk[], u32 rounds, u8 mac[], 38 u8 ctr[]); 39 40 asmlinkage void ce_aes_ccm_decrypt(u8 out[], u8 const in[], u32 cbytes, 41 u32 const rk[], u32 rounds, u8 mac[], 42 u8 ctr[]); 43 44 asmlinkage void ce_aes_ccm_final(u8 mac[], u8 const ctr[], u32 const rk[], 45 u32 rounds); 46 47 static int ccm_setkey(struct crypto_aead *tfm, const u8 *in_key, 48 unsigned int key_len) 49 { 50 struct crypto_aes_ctx *ctx = crypto_aead_ctx(tfm); 51 int ret; 52 53 ret = ce_aes_expandkey(ctx, in_key, key_len); 54 if (!ret) 55 return 0; 56 57 tfm->base.crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN; 58 return -EINVAL; 59 } 60 61 static int ccm_setauthsize(struct crypto_aead *tfm, unsigned int authsize) 62 { 63 if ((authsize & 1) || authsize < 4) 64 return -EINVAL; 65 return 0; 66 } 67 68 static int ccm_init_mac(struct aead_request *req, u8 maciv[], u32 msglen) 69 { 70 struct crypto_aead *aead = crypto_aead_reqtfm(req); 71 __be32 *n = (__be32 *)&maciv[AES_BLOCK_SIZE - 8]; 72 u32 l = req->iv[0] + 1; 73 74 /* verify that CCM dimension 'L' is set correctly in the IV */ 75 if (l < 2 || l > 8) 76 return -EINVAL; 77 78 /* verify that msglen can in fact be represented in L bytes */ 79 if (l < 4 && msglen >> (8 * l)) 80 return -EOVERFLOW; 81 82 /* 83 * Even if the CCM spec allows L values of up to 8, the Linux cryptoapi 84 * uses a u32 type to represent msglen so the top 4 bytes are always 0. 85 */ 86 n[0] = 0; 87 n[1] = cpu_to_be32(msglen); 88 89 memcpy(maciv, req->iv, AES_BLOCK_SIZE - l); 90 91 /* 92 * Meaning of byte 0 according to CCM spec (RFC 3610/NIST 800-38C) 93 * - bits 0..2 : max # of bytes required to represent msglen, minus 1 94 * (already set by caller) 95 * - bits 3..5 : size of auth tag (1 => 4 bytes, 2 => 6 bytes, etc) 96 * - bit 6 : indicates presence of authenticate-only data 97 */ 98 maciv[0] |= (crypto_aead_authsize(aead) - 2) << 2; 99 if (req->assoclen) 100 maciv[0] |= 0x40; 101 102 memset(&req->iv[AES_BLOCK_SIZE - l], 0, l); 103 return 0; 104 } 105 106 static void ccm_calculate_auth_mac(struct aead_request *req, u8 mac[]) 107 { 108 struct crypto_aead *aead = crypto_aead_reqtfm(req); 109 struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead); 110 struct __packed { __be16 l; __be32 h; u16 len; } ltag; 111 struct scatter_walk walk; 112 u32 len = req->assoclen; 113 u32 macp = 0; 114 115 /* prepend the AAD with a length tag */ 116 if (len < 0xff00) { 117 ltag.l = cpu_to_be16(len); 118 ltag.len = 2; 119 } else { 120 ltag.l = cpu_to_be16(0xfffe); 121 put_unaligned_be32(len, <ag.h); 122 ltag.len = 6; 123 } 124 125 ce_aes_ccm_auth_data(mac, (u8 *)<ag, ltag.len, &macp, ctx->key_enc, 126 num_rounds(ctx)); 127 scatterwalk_start(&walk, req->src); 128 129 do { 130 u32 n = scatterwalk_clamp(&walk, len); 131 u8 *p; 132 133 if (!n) { 134 scatterwalk_start(&walk, sg_next(walk.sg)); 135 n = scatterwalk_clamp(&walk, len); 136 } 137 p = scatterwalk_map(&walk); 138 ce_aes_ccm_auth_data(mac, p, n, &macp, ctx->key_enc, 139 num_rounds(ctx)); 140 len -= n; 141 142 scatterwalk_unmap(p); 143 scatterwalk_advance(&walk, n); 144 scatterwalk_done(&walk, 0, len); 145 } while (len); 146 } 147 148 static int ccm_encrypt(struct aead_request *req) 149 { 150 struct crypto_aead *aead = crypto_aead_reqtfm(req); 151 struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead); 152 struct skcipher_walk walk; 153 u8 __aligned(8) mac[AES_BLOCK_SIZE]; 154 u8 buf[AES_BLOCK_SIZE]; 155 u32 len = req->cryptlen; 156 int err; 157 158 err = ccm_init_mac(req, mac, len); 159 if (err) 160 return err; 161 162 kernel_neon_begin_partial(6); 163 164 if (req->assoclen) 165 ccm_calculate_auth_mac(req, mac); 166 167 /* preserve the original iv for the final round */ 168 memcpy(buf, req->iv, AES_BLOCK_SIZE); 169 170 err = skcipher_walk_aead_encrypt(&walk, req, true); 171 172 while (walk.nbytes) { 173 u32 tail = walk.nbytes % AES_BLOCK_SIZE; 174 175 if (walk.nbytes == walk.total) 176 tail = 0; 177 178 ce_aes_ccm_encrypt(walk.dst.virt.addr, walk.src.virt.addr, 179 walk.nbytes - tail, ctx->key_enc, 180 num_rounds(ctx), mac, walk.iv); 181 182 err = skcipher_walk_done(&walk, tail); 183 } 184 if (!err) 185 ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx)); 186 187 kernel_neon_end(); 188 189 if (err) 190 return err; 191 192 /* copy authtag to end of dst */ 193 scatterwalk_map_and_copy(mac, req->dst, req->assoclen + req->cryptlen, 194 crypto_aead_authsize(aead), 1); 195 196 return 0; 197 } 198 199 static int ccm_decrypt(struct aead_request *req) 200 { 201 struct crypto_aead *aead = crypto_aead_reqtfm(req); 202 struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead); 203 unsigned int authsize = crypto_aead_authsize(aead); 204 struct skcipher_walk walk; 205 u8 __aligned(8) mac[AES_BLOCK_SIZE]; 206 u8 buf[AES_BLOCK_SIZE]; 207 u32 len = req->cryptlen - authsize; 208 int err; 209 210 err = ccm_init_mac(req, mac, len); 211 if (err) 212 return err; 213 214 kernel_neon_begin_partial(6); 215 216 if (req->assoclen) 217 ccm_calculate_auth_mac(req, mac); 218 219 /* preserve the original iv for the final round */ 220 memcpy(buf, req->iv, AES_BLOCK_SIZE); 221 222 err = skcipher_walk_aead_decrypt(&walk, req, true); 223 224 while (walk.nbytes) { 225 u32 tail = walk.nbytes % AES_BLOCK_SIZE; 226 227 if (walk.nbytes == walk.total) 228 tail = 0; 229 230 ce_aes_ccm_decrypt(walk.dst.virt.addr, walk.src.virt.addr, 231 walk.nbytes - tail, ctx->key_enc, 232 num_rounds(ctx), mac, walk.iv); 233 234 err = skcipher_walk_done(&walk, tail); 235 } 236 if (!err) 237 ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx)); 238 239 kernel_neon_end(); 240 241 if (err) 242 return err; 243 244 /* compare calculated auth tag with the stored one */ 245 scatterwalk_map_and_copy(buf, req->src, 246 req->assoclen + req->cryptlen - authsize, 247 authsize, 0); 248 249 if (crypto_memneq(mac, buf, authsize)) 250 return -EBADMSG; 251 return 0; 252 } 253 254 static struct aead_alg ccm_aes_alg = { 255 .base = { 256 .cra_name = "ccm(aes)", 257 .cra_driver_name = "ccm-aes-ce", 258 .cra_priority = 300, 259 .cra_blocksize = 1, 260 .cra_ctxsize = sizeof(struct crypto_aes_ctx), 261 .cra_module = THIS_MODULE, 262 }, 263 .ivsize = AES_BLOCK_SIZE, 264 .chunksize = AES_BLOCK_SIZE, 265 .maxauthsize = AES_BLOCK_SIZE, 266 .setkey = ccm_setkey, 267 .setauthsize = ccm_setauthsize, 268 .encrypt = ccm_encrypt, 269 .decrypt = ccm_decrypt, 270 }; 271 272 static int __init aes_mod_init(void) 273 { 274 if (!(elf_hwcap & HWCAP_AES)) 275 return -ENODEV; 276 return crypto_register_aead(&ccm_aes_alg); 277 } 278 279 static void __exit aes_mod_exit(void) 280 { 281 crypto_unregister_aead(&ccm_aes_alg); 282 } 283 284 module_init(aes_mod_init); 285 module_exit(aes_mod_exit); 286 287 MODULE_DESCRIPTION("Synchronous AES in CCM mode using ARMv8 Crypto Extensions"); 288 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>"); 289 MODULE_LICENSE("GPL v2"); 290 MODULE_ALIAS_CRYPTO("ccm(aes)"); 291