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 <crypto/internal/aead.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, &ltag.h);
 122                 ltag.len = 6;
 123         }
 124
 125         ce_aes_ccm_auth_data(mac, (u8 *)&ltag, ltag.len, &macp, ctx->key_enc,
 126                              num_rounds(ctx));
 127         scatterwalk_start(&walk, req->assoc);
 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 blkcipher_desc desc = { .info = req->iv };
 153         struct blkcipher_walk walk;
 154         u8 __aligned(8) mac[AES_BLOCK_SIZE];
 155         u8 buf[AES_BLOCK_SIZE];
 156         u32 len = req->cryptlen;
 157         int err;
 158
 159         err = ccm_init_mac(req, mac, len);
 160         if (err)
 161                 return err;
 162
 163         kernel_neon_begin_partial(6);
 164
 165         if (req->assoclen)
 166                 ccm_calculate_auth_mac(req, mac);
 167
 168         /* preserve the original iv for the final round */
 169         memcpy(buf, req->iv, AES_BLOCK_SIZE);
 170
 171         blkcipher_walk_init(&walk, req->dst, req->src, len);
 172         err = blkcipher_aead_walk_virt_block(&desc, &walk, aead,
 173                                              AES_BLOCK_SIZE);
 174
 175         while (walk.nbytes) {
 176                 u32 tail = walk.nbytes % AES_BLOCK_SIZE;
 177
 178                 if (walk.nbytes == len)
 179                         tail = 0;
 180
 181                 ce_aes_ccm_encrypt(walk.dst.virt.addr, walk.src.virt.addr,
 182                                    walk.nbytes - tail, ctx->key_enc,
 183                                    num_rounds(ctx), mac, walk.iv);
 184
 185                 len -= walk.nbytes - tail;
 186                 err = blkcipher_walk_done(&desc, &walk, tail);
 187         }
 188         if (!err)
 189                 ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
 190
 191         kernel_neon_end();
 192
 193         if (err)
 194                 return err;
 195
 196         /* copy authtag to end of dst */
 197         scatterwalk_map_and_copy(mac, req->dst, req->cryptlen,
 198                                  crypto_aead_authsize(aead), 1);
 199
 200         return 0;
 201 }
 202
 203 static int ccm_decrypt(struct aead_request *req)
 204 {
 205         struct crypto_aead *aead = crypto_aead_reqtfm(req);
 206         struct crypto_aes_ctx *ctx = crypto_aead_ctx(aead);
 207         unsigned int authsize = crypto_aead_authsize(aead);
 208         struct blkcipher_desc desc = { .info = req->iv };
 209         struct blkcipher_walk walk;
 210         u8 __aligned(8) mac[AES_BLOCK_SIZE];
 211         u8 buf[AES_BLOCK_SIZE];
 212         u32 len = req->cryptlen - authsize;
 213         int err;
 214
 215         err = ccm_init_mac(req, mac, len);
 216         if (err)
 217                 return err;
 218
 219         kernel_neon_begin_partial(6);
 220
 221         if (req->assoclen)
 222                 ccm_calculate_auth_mac(req, mac);
 223
 224         /* preserve the original iv for the final round */
 225         memcpy(buf, req->iv, AES_BLOCK_SIZE);
 226
 227         blkcipher_walk_init(&walk, req->dst, req->src, len);
 228         err = blkcipher_aead_walk_virt_block(&desc, &walk, aead,
 229                                              AES_BLOCK_SIZE);
 230
 231         while (walk.nbytes) {
 232                 u32 tail = walk.nbytes % AES_BLOCK_SIZE;
 233
 234                 if (walk.nbytes == len)
 235                         tail = 0;
 236
 237                 ce_aes_ccm_decrypt(walk.dst.virt.addr, walk.src.virt.addr,
 238                                    walk.nbytes - tail, ctx->key_enc,
 239                                    num_rounds(ctx), mac, walk.iv);
 240
 241                 len -= walk.nbytes - tail;
 242                 err = blkcipher_walk_done(&desc, &walk, tail);
 243         }
 244         if (!err)
 245                 ce_aes_ccm_final(mac, buf, ctx->key_enc, num_rounds(ctx));
 246
 247         kernel_neon_end();
 248
 249         if (err)
 250                 return err;
 251
 252         /* compare calculated auth tag with the stored one */
 253         scatterwalk_map_and_copy(buf, req->src, req->cryptlen - authsize,
 254                                  authsize, 0);
 255
 256         if (memcmp(mac, buf, authsize))
 257                 return -EBADMSG;
 258         return 0;
 259 }
 260
 261 static struct crypto_alg ccm_aes_alg = {
 262         .cra_name               = "ccm(aes)",
 263         .cra_driver_name        = "ccm-aes-ce",
 264         .cra_priority           = 300,
 265         .cra_flags              = CRYPTO_ALG_TYPE_AEAD,
 266         .cra_blocksize          = 1,
 267         .cra_ctxsize            = sizeof(struct crypto_aes_ctx),
 268         .cra_alignmask          = 7,
 269         .cra_type               = &crypto_aead_type,
 270         .cra_module             = THIS_MODULE,
 271         .cra_aead = {
 272                 .ivsize         = AES_BLOCK_SIZE,
 273                 .maxauthsize    = AES_BLOCK_SIZE,
 274                 .setkey         = ccm_setkey,
 275                 .setauthsize    = ccm_setauthsize,
 276                 .encrypt        = ccm_encrypt,
 277                 .decrypt        = ccm_decrypt,
 278         }
 279 };
 280
 281 static int __init aes_mod_init(void)
 282 {
 283         if (!(elf_hwcap & HWCAP_AES))
 284                 return -ENODEV;
 285         return crypto_register_alg(&ccm_aes_alg);
 286 }
 287
 288 static void __exit aes_mod_exit(void)
 289 {
 290         crypto_unregister_alg(&ccm_aes_alg);
 291 }
 292
 293 module_init(aes_mod_init);
 294 module_exit(aes_mod_exit);
 295
 296 MODULE_DESCRIPTION("Synchronous AES in CCM mode using ARMv8 Crypto Extensions");
 297 MODULE_AUTHOR("Ard Biesheuvel <ard.biesheuvel@linaro.org>");
 298 MODULE_LICENSE("GPL v2");
 299 MODULE_ALIAS_CRYPTO("ccm(aes)");