arch/arm64/crypto/aes-ce-ccm-glue.c

   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/algapi.h>
  15 #include <crypto/scatterwalk.h>
  16 #include <linux/crypto.h>
  17 #include <linux/module.h>
  18
  19 static int num_rounds(struct crypto_aes_ctx *ctx)
  20 {
  21         /*
  22          * # of rounds specified by AES:
  23          * 128 bit key          10 rounds
  24          * 192 bit key          12 rounds
  25          * 256 bit key          14 rounds
  26          * => n byte key        => 6 + (n/4) rounds
  27          */
  28         return 6 + ctx->key_length / 4;
  29 }
  30
  31 asmlinkage void ce_aes_ccm_auth_data(u8 mac[], u8 const in[], u32 abytes,
  32                                      u32 *macp, u32 const rk[], u32 rounds);
  33
  34 asmlinkage void ce_aes_ccm_encrypt(u8 out[], u8 const in[], u32 cbytes,
  35                                    u32 const rk[], u32 rounds, u8 mac[],
  36                                    u8 ctr[]);
  37
  38 asmlinkage void ce_aes_ccm_decrypt(u8 out[], u8 const in[], u32 cbytes,
  39                                    u32 const rk[], u32 rounds, u8 mac[],
  40                                    u8 ctr[]);
  41
  42 asmlinkage void ce_aes_ccm_final(u8 mac[], u8 const ctr[], u32 const rk[],
  43                                  u32 rounds);
  44
  45 static int ccm_setkey(struct crypto_aead *tfm, const u8 *in_key,
  46                       unsigned int key_len)
  47 {
  48         struct crypto_aes_ctx *ctx = crypto_aead_ctx(tfm);
  49         int ret;
  50
  51         ret = crypto_aes_expand_key(ctx, in_key, key_len);
  52         if (!ret)
  53                 return 0;
  54
  55         tfm->base.crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
  56         return -EINVAL;
  57 }
  58
  59 static int ccm_setauthsize(struct crypto_aead *tfm, unsigned int authsize)
  60 {
  61         if ((authsize & 1) || authsize < 4)
  62                 return -EINVAL;
  63         return 0;
  64 }
  65
  66 static int ccm_init_mac(struct aead_request *req, u8 maciv[], u32 msglen)
  67 {
  68         struct crypto_aead *aead = crypto_aead_reqtfm(req);
  69         __be32 *n = (__be32 *)&maciv[AES_BLOCK_SIZE - 8];
  70         u32 l = req->iv[0] + 1;
  71
  72         /* verify that CCM dimension 'L' is set correctly in the IV */
  73         if (l < 2 || l > 8)
  74                 return -EINVAL;
  75
  76         /* verify that msglen can in fact be represented in L bytes */
  77         if (l < 4 && msglen >> (8 * l))
  78                 return -EOVERFLOW;
  79
  80         /*
  81          * Even if the CCM spec allows L values of up to 8, the Linux cryptoapi
  82          * uses a u32 type to represent msglen so the top 4 bytes are always 0.
  83          */
  84         n[0] = 0;
  85         n[1] = cpu_to_be32(msglen);
  86
  87         memcpy(maciv, req->iv, AES_BLOCK_SIZE - l);
  88
  89         /*
  90          * Meaning of byte 0 according to CCM spec (RFC 3610/NIST 800-38C)
  91          * - bits 0..2  : max # of bytes required to represent msglen, minus 1
  92          *                (already set by caller)
  93          * - bits 3..5  : size of auth tag (1 => 4 bytes, 2 => 6 bytes, etc)
  94          * - bit 6      : indicates presence of authenticate-only data
  95          */
  96         maciv[0] |= (crypto_aead_authsize(aead) - 2) << 2;
  97         if (req->assoclen)
  98                 maciv[0] |= 0x40;
  99
 100         memset(&req->iv[AES_BLOCK_SIZE - l], 0, l);
 101         return 0;
 102 }
 103
 104 static void ccm_calculate_auth_mac(struct aead_request *req, u8 mac[])
 105 {
 106         struct crypto_aead *aead = crypto_aead_reqtfm(req);
 107         struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
 108         struct __packed { __be16 l; __be32 h; u16 len; } ltag;
 109         struct scatter_walk walk;
 110         u32 len = req->assoclen;
 111         u32 macp = 0;
 112
 113         /* prepend the AAD with a length tag */
 114         if (len < 0xff00) {
 115                 ltag.l = cpu_to_be16(len);
 116                 ltag.len = 2;
 117         } else  {
 118                 ltag.l = cpu_to_be16(0xfffe);
 119                 put_unaligned_be32(len, &ltag.h);
 120                 ltag.len = 6;
 121         }
 122
 123         ce_aes_ccm_auth_data(mac, (u8 *)&ltag, ltag.len, &macp, ctx->key_enc,
 124                              num_rounds(ctx));
 125         scatterwalk_start(&walk, req->assoc);
 126
 127         do {
 128                 u32 n = scatterwalk_clamp(&walk, len);
 129                 u8 *p;
 130
 131                 if (!n) {
 132                         scatterwalk_start(&walk, sg_next(walk.sg));
 133                         n = scatterwalk_clamp(&walk, len);
 134                 }
 135                 p = scatterwalk_map(&walk);
 136                 ce_aes_ccm_auth_data(mac, p, n, &macp, ctx->key_enc,
 137                                      num_rounds(ctx));
 138                 len -= n;
 139
 140                 scatterwalk_unmap(p);
 141                 scatterwalk_advance(&walk, n);
 142                 scatterwalk_done(&walk, 0, len);
 143         } while (len);
 144 }
 145
 146 static int ccm_encrypt(struct aead_request *req)
 147 {
 148         struct crypto_aead *aead = crypto_aead_reqtfm(req);
 149         struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
 150         struct blkcipher_desc desc = { .info = req->iv };
 151         struct blkcipher_walk walk;
 152         u8 __aligned(8) mac[AES_BLOCK_SIZE];
 153         u8 buf[AES_BLOCK_SIZE];
 154         u32 len = req->cryptlen;
 155         int err;
 156
 157         err = ccm_init_mac(req, mac, len);
 158         if (err)
 159                 return err;
 160
 161         kernel_neon_begin_partial(6);
 162
 163         if (req->assoclen)
 164                 ccm_calculate_auth_mac(req, mac);
 165
 166         /* preserve the original iv for the final round */
 167         memcpy(buf, req->iv, AES_BLOCK_SIZE);
 168
 169         blkcipher_walk_init(&walk, req->dst, req->src, len);
 170         err = blkcipher_aead_walk_virt_block(&desc, &walk, aead,
 171                                              AES_BLOCK_SIZE);
 172
 173         while (walk.nbytes) {
 174                 u32 tail = walk.nbytes % AES_BLOCK_SIZE;
 175
 176                 if (walk.nbytes == len)
 177                         tail = 0;
 178
 179                 ce_aes_ccm_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
 180                                    walk.nbytes - tail, ctx->key_enc,
 181                                    num_rounds(ctx), mac, walk.iv);
 182
 183                 len -= walk.nbytes - tail;
 184                 err = blkcipher_walk_done(&desc, &walk, tail);
 185         }
 186         if (!err)
 187                 ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
 188
 189         kernel_neon_end();
 190
 191         if (err)
 192                 return err;
 193
 194         /* copy authtag to end of dst */
 195         scatterwalk_map_and_copy(mac, req->dst, req->cryptlen,
 196                                  crypto_aead_authsize(aead), 1);
 197
 198         return 0;
 199 }
 200
 201 static int ccm_decrypt(struct aead_request *req)
 202 {
 203         struct crypto_aead *aead = crypto_aead_reqtfm(req);
 204         struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
 205         unsigned int authsize = crypto_aead_authsize(aead);
 206         struct blkcipher_desc desc = { .info = req->iv };
 207         struct blkcipher_walk walk;
 208         u8 __aligned(8) mac[AES_BLOCK_SIZE];
 209         u8 buf[AES_BLOCK_SIZE];
 210         u32 len = req->cryptlen - authsize;
 211         int err;
 212
 213         err = ccm_init_mac(req, mac, len);
 214         if (err)
 215                 return err;
 216
 217         kernel_neon_begin_partial(6);
 218
 219         if (req->assoclen)
 220                 ccm_calculate_auth_mac(req, mac);
 221
 222         /* preserve the original iv for the final round */
 223         memcpy(buf, req->iv, AES_BLOCK_SIZE);
 224
 225         blkcipher_walk_init(&walk, req->dst, req->src, len);
 226         err = blkcipher_aead_walk_virt_block(&desc, &walk, aead,
 227                                              AES_BLOCK_SIZE);
 228
 229         while (walk.nbytes) {
 230                 u32 tail = walk.nbytes % AES_BLOCK_SIZE;
 231
 232                 if (walk.nbytes == len)
 233                         tail = 0;
 234
 235                 ce_aes_ccm_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
 236                                    walk.nbytes - tail, ctx->key_enc,
 237                                    num_rounds(ctx), mac, walk.iv);
 238
 239                 len -= walk.nbytes - tail;
 240                 err = blkcipher_walk_done(&desc, &walk, tail);
 241         }
 242         if (!err)
 243                 ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
 244
 245         kernel_neon_end();
 246
 247         if (err)
 248                 return err;
 249
 250         /* compare calculated auth tag with the stored one */
 251         scatterwalk_map_and_copy(buf, req->src, req->cryptlen - authsize,
 252                                  authsize, 0);
 253
 254         if (memcmp(mac, buf, authsize))
 255                 return -EBADMSG;
 256         return 0;
 257 }
 258
 259 static struct crypto_alg ccm_aes_alg = {
 260         .cra_name               = "ccm(aes)",
 261         .cra_driver_name        = "ccm-aes-ce",
 262         .cra_priority           = 300,
 263         .cra_flags              = CRYPTO_ALG_TYPE_AEAD,
 264         .cra_blocksize          = 1,
 265         .cra_ctxsize            = sizeof(struct crypto_aes_ctx),
 266         .cra_alignmask          = 7,
 267         .cra_type               = &crypto_aead_type,
 268         .cra_module             = THIS_MODULE,
 269         .cra_aead = {
 270                 .ivsize         = AES_BLOCK_SIZE,
 271                 .maxauthsize    = AES_BLOCK_SIZE,
 272                 .setkey         = ccm_setkey,
 273                 .setauthsize    = ccm_setauthsize,
 274                 .encrypt        = ccm_encrypt,
 275                 .decrypt        = ccm_decrypt,
 276         }
 277 };
 278
 279 static int __init aes_mod_init(void)
 280 {
 281         if (!(elf_hwcap & HWCAP_AES))
 282                 return -ENODEV;
 283         return crypto_register_alg(&ccm_aes_alg);
 284 }
 285
 286 static void __exit aes_mod_exit(void)
 287 {
 288         crypto_unregister_alg(&ccm_aes_alg);
 289 }
 290
 291 module_init(aes_mod_init);
 292 module_exit(aes_mod_exit);
 293
 294 MODULE_DESCRIPTION("Synchronous AES in CCM mode using ARMv8 Crypto Extensions");
 295 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
 296 MODULE_LICENSE("GPL v2");
 297 MODULE_ALIAS("ccm(aes)");