crypto/gcm.c

   1 /*
   2  * GCM: Galois/Counter Mode.
   3  *
   4  * Copyright (c) 2007 Nokia Siemens Networks - Mikko Herranen <mh1@iki.fi>
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 as published
   8  * by the Free Software Foundation.
   9  */
  10
  11 #include <crypto/algapi.h>
  12 #include <crypto/gf128mul.h>
  13 #include <crypto/scatterwalk.h>
  14 #include <linux/err.h>
  15 #include <linux/init.h>
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/slab.h>
  19
  20 #include "internal.h"
  21
  22 struct gcm_instance_ctx {
  23         struct crypto_spawn ctr;
  24 };
  25
  26 struct crypto_gcm_ctx {
  27         struct crypto_ablkcipher *ctr;
  28         struct gf128mul_4k *gf128;
  29 };
  30
  31 struct crypto_gcm_ghash_ctx {
  32         u32 bytes;
  33         u32 flags;
  34         struct gf128mul_4k *gf128;
  35         u8 buffer[16];
  36 };
  37
  38 struct crypto_gcm_req_priv_ctx {
  39         u8 auth_tag[16];
  40         u8 iauth_tag[16];
  41         u8 counter[16];
  42         struct crypto_gcm_ghash_ctx ghash;
  43         struct ablkcipher_request abreq;
  44 };
  45
  46 static void crypto_gcm_ghash_init(struct crypto_gcm_ghash_ctx *ctx, u32 flags,
  47                                   struct gf128mul_4k *gf128)
  48 {
  49         ctx->bytes = 0;
  50         ctx->flags = flags;
  51         ctx->gf128 = gf128;
  52         memset(ctx->buffer, 0, 16);
  53 }
  54
  55 static void crypto_gcm_ghash_update(struct crypto_gcm_ghash_ctx *ctx,
  56                                     const u8 *src, unsigned int srclen)
  57 {
  58         u8 *dst = ctx->buffer;
  59
  60         if (ctx->bytes) {
  61                 int n = min(srclen, ctx->bytes);
  62                 u8 *pos = dst + (16 - ctx->bytes);
  63
  64                 ctx->bytes -= n;
  65                 srclen -= n;
  66
  67                 while (n--)
  68                         *pos++ ^= *src++;
  69
  70                 if (!ctx->bytes)
  71                         gf128mul_4k_lle((be128 *)dst, ctx->gf128);
  72         }
  73
  74         while (srclen >= 16) {
  75                 crypto_xor(dst, src, 16);
  76                 gf128mul_4k_lle((be128 *)dst, ctx->gf128);
  77                 src += 16;
  78                 srclen -= 16;
  79         }
  80
  81         if (srclen) {
  82                 ctx->bytes = 16 - srclen;
  83                 while (srclen--)
  84                         *dst++ ^= *src++;
  85         }
  86 }
  87
  88 static void crypto_gcm_ghash_update_sg(struct crypto_gcm_ghash_ctx *ctx,
  89                                        struct scatterlist *sg, int len)
  90 {
  91         struct scatter_walk walk;
  92         u8 *src;
  93         int n;
  94
  95         if (!len)
  96                 return;
  97
  98         scatterwalk_start(&walk, sg);
  99
 100         while (len) {
 101                 n = scatterwalk_clamp(&walk, len);
 102
 103                 if (!n) {
 104                         scatterwalk_start(&walk, scatterwalk_sg_next(walk.sg));
 105                         n = scatterwalk_clamp(&walk, len);
 106                 }
 107
 108                 src = scatterwalk_map(&walk, 0);
 109
 110                 crypto_gcm_ghash_update(ctx, src, n);
 111                 len -= n;
 112
 113                 scatterwalk_unmap(src, 0);
 114                 scatterwalk_advance(&walk, n);
 115                 scatterwalk_done(&walk, 0, len);
 116                 if (len)
 117                         crypto_yield(ctx->flags);
 118         }
 119 }
 120
 121 static void crypto_gcm_ghash_flush(struct crypto_gcm_ghash_ctx *ctx)
 122 {
 123         u8 *dst = ctx->buffer;
 124
 125         if (ctx->bytes) {
 126                 u8 *tmp = dst + (16 - ctx->bytes);
 127
 128                 while (ctx->bytes--)
 129                         *tmp++ ^= 0;
 130
 131                 gf128mul_4k_lle((be128 *)dst, ctx->gf128);
 132         }
 133
 134         ctx->bytes = 0;
 135 }
 136
 137 static void crypto_gcm_ghash_final_xor(struct crypto_gcm_ghash_ctx *ctx,
 138                                        unsigned int authlen,
 139                                        unsigned int cryptlen, u8 *dst)
 140 {
 141         u8 *buf = ctx->buffer;
 142         u128 lengths;
 143
 144         lengths.a = cpu_to_be64(authlen * 8);
 145         lengths.b = cpu_to_be64(cryptlen * 8);
 146
 147         crypto_gcm_ghash_flush(ctx);
 148         crypto_xor(buf, (u8 *)&lengths, 16);
 149         gf128mul_4k_lle((be128 *)buf, ctx->gf128);
 150         crypto_xor(dst, buf, 16);
 151 }
 152
 153 static inline void crypto_gcm_set_counter(u8 *counterblock, u32 value)
 154 {
 155         *((u32 *)&counterblock[12]) = cpu_to_be32(value);
 156 }
 157
 158 static int crypto_gcm_encrypt_counter(struct crypto_aead *aead, u8 *block,
 159                                        u32 value, const u8 *iv)
 160 {
 161         struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
 162         struct crypto_ablkcipher *ctr = ctx->ctr;
 163         struct ablkcipher_request req;
 164         struct scatterlist sg;
 165         u8 counterblock[16];
 166
 167         if (iv == NULL)
 168                 memset(counterblock, 0, 12);
 169         else
 170                 memcpy(counterblock, iv, 12);
 171
 172         crypto_gcm_set_counter(counterblock, value);
 173
 174         sg_init_one(&sg, block, 16);
 175         ablkcipher_request_set_tfm(&req, ctr);
 176         ablkcipher_request_set_crypt(&req, &sg, &sg, 16, counterblock);
 177         ablkcipher_request_set_callback(&req, 0, NULL, NULL);
 178         memset(block, 0, 16);
 179         return crypto_ablkcipher_encrypt(&req);
 180 }
 181
 182 static int crypto_gcm_setkey(struct crypto_aead *aead, const u8 *key,
 183                              unsigned int keylen)
 184 {
 185         struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
 186         struct crypto_ablkcipher *ctr = ctx->ctr;
 187         int alignmask = crypto_ablkcipher_alignmask(ctr);
 188         u8 alignbuf[16+alignmask];
 189         u8 *hash = (u8 *)ALIGN((unsigned long)alignbuf, alignmask+1);
 190         int err = 0;
 191
 192         crypto_ablkcipher_clear_flags(ctr, CRYPTO_TFM_REQ_MASK);
 193         crypto_ablkcipher_set_flags(ctr, crypto_aead_get_flags(aead) &
 194                                    CRYPTO_TFM_REQ_MASK);
 195
 196         err = crypto_ablkcipher_setkey(ctr, key, keylen);
 197         if (err)
 198                 goto out;
 199
 200         crypto_aead_set_flags(aead, crypto_ablkcipher_get_flags(ctr) &
 201                                        CRYPTO_TFM_RES_MASK);
 202
 203         err = crypto_gcm_encrypt_counter(aead, hash, -1, NULL);
 204         if (err)
 205                 goto out;
 206
 207         if (ctx->gf128 != NULL)
 208                 gf128mul_free_4k(ctx->gf128);
 209
 210         ctx->gf128 = gf128mul_init_4k_lle((be128 *)hash);
 211
 212         if (ctx->gf128 == NULL)
 213                 err = -ENOMEM;
 214
 215  out:
 216         return err;
 217 }
 218
 219 static int crypto_gcm_init_crypt(struct ablkcipher_request *ablk_req,
 220                                  struct aead_request *req,
 221                                  unsigned int cryptlen,
 222                                  void (*done)(struct crypto_async_request *,
 223                                               int))
 224 {
 225         struct crypto_aead *aead = crypto_aead_reqtfm(req);
 226         struct crypto_gcm_ctx *ctx = crypto_aead_ctx(aead);
 227         struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
 228         u32 flags = req->base.tfm->crt_flags;
 229         u8 *auth_tag = pctx->auth_tag;
 230         u8 *counter = pctx->counter;
 231         struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
 232         int err = 0;
 233
 234         ablkcipher_request_set_tfm(ablk_req, ctx->ctr);
 235         ablkcipher_request_set_callback(ablk_req, aead_request_flags(req),
 236                                         done, req);
 237         ablkcipher_request_set_crypt(ablk_req, req->src, req->dst,
 238                                      cryptlen, counter);
 239
 240         err = crypto_gcm_encrypt_counter(aead, auth_tag, 0, req->iv);
 241         if (err)
 242                 goto out;
 243
 244         memcpy(counter, req->iv, 12);
 245         crypto_gcm_set_counter(counter, 1);
 246
 247         crypto_gcm_ghash_init(ghash, flags, ctx->gf128);
 248
 249         crypto_gcm_ghash_update_sg(ghash, req->assoc, req->assoclen);
 250         crypto_gcm_ghash_flush(ghash);
 251
 252  out:
 253         return err;
 254 }
 255
 256 static int crypto_gcm_hash(struct aead_request *req)
 257 {
 258         struct crypto_aead *aead = crypto_aead_reqtfm(req);
 259         struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
 260         u8 *auth_tag = pctx->auth_tag;
 261         struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
 262
 263         crypto_gcm_ghash_update_sg(ghash, req->dst, req->cryptlen);
 264         crypto_gcm_ghash_final_xor(ghash, req->assoclen, req->cryptlen,
 265                                    auth_tag);
 266
 267         scatterwalk_map_and_copy(auth_tag, req->dst, req->cryptlen,
 268                                  crypto_aead_authsize(aead), 1);
 269         return 0;
 270 }
 271
 272 static void crypto_gcm_encrypt_done(struct crypto_async_request *areq, int err)
 273 {
 274         struct aead_request *req = areq->data;
 275
 276         if (!err)
 277                 err = crypto_gcm_hash(req);
 278
 279         aead_request_complete(req, err);
 280 }
 281
 282 static int crypto_gcm_encrypt(struct aead_request *req)
 283 {
 284         struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
 285         struct ablkcipher_request *abreq = &pctx->abreq;
 286         int err = 0;
 287
 288         err = crypto_gcm_init_crypt(abreq, req, req->cryptlen,
 289                                     crypto_gcm_encrypt_done);
 290         if (err)
 291                 return err;
 292
 293         if (req->cryptlen) {
 294                 err = crypto_ablkcipher_encrypt(abreq);
 295                 if (err)
 296                         return err;
 297         }
 298
 299         return crypto_gcm_hash(req);
 300 }
 301
 302 static void crypto_gcm_decrypt_done(struct crypto_async_request *areq, int err)
 303 {
 304         aead_request_complete(areq->data, err);
 305 }
 306
 307 static int crypto_gcm_decrypt(struct aead_request *req)
 308 {
 309         struct crypto_aead *aead = crypto_aead_reqtfm(req);
 310         struct crypto_gcm_req_priv_ctx *pctx = aead_request_ctx(req);
 311         struct ablkcipher_request *abreq = &pctx->abreq;
 312         u8 *auth_tag = pctx->auth_tag;
 313         u8 *iauth_tag = pctx->iauth_tag;
 314         struct crypto_gcm_ghash_ctx *ghash = &pctx->ghash;
 315         unsigned int cryptlen = req->cryptlen;
 316         unsigned int authsize = crypto_aead_authsize(aead);
 317         int err;
 318
 319         if (cryptlen < authsize)
 320                 return -EINVAL;
 321         cryptlen -= authsize;
 322
 323         err = crypto_gcm_init_crypt(abreq, req, cryptlen,
 324                                     crypto_gcm_decrypt_done);
 325         if (err)
 326                 return err;
 327
 328         crypto_gcm_ghash_update_sg(ghash, req->src, cryptlen);
 329         crypto_gcm_ghash_final_xor(ghash, req->assoclen, cryptlen, auth_tag);
 330
 331         scatterwalk_map_and_copy(iauth_tag, req->src, cryptlen, authsize, 0);
 332         if (memcmp(iauth_tag, auth_tag, authsize))
 333                 return -EBADMSG;
 334
 335         return crypto_ablkcipher_decrypt(abreq);
 336 }
 337
 338 static int crypto_gcm_init_tfm(struct crypto_tfm *tfm)
 339 {
 340         struct crypto_instance *inst = (void *)tfm->__crt_alg;
 341         struct gcm_instance_ctx *ictx = crypto_instance_ctx(inst);
 342         struct crypto_gcm_ctx *ctx = crypto_tfm_ctx(tfm);
 343         struct crypto_ablkcipher *ctr;
 344         unsigned long align;
 345         int err;
 346
 347         ctr = crypto_spawn_ablkcipher(&ictx->ctr);
 348         err = PTR_ERR(ctr);
 349         if (IS_ERR(ctr))
 350                 return err;
 351
 352         ctx->ctr = ctr;
 353         ctx->gf128 = NULL;
 354
 355         align = max_t(unsigned long, crypto_ablkcipher_alignmask(ctr),
 356                       __alignof__(u32) - 1);
 357         align &= ~(crypto_tfm_ctx_alignment() - 1);
 358         tfm->crt_aead.reqsize = align +
 359                                 sizeof(struct crypto_gcm_req_priv_ctx) +
 360                                 crypto_ablkcipher_reqsize(ctr);
 361
 362         return 0;
 363 }
 364
 365 static void crypto_gcm_exit_tfm(struct crypto_tfm *tfm)
 366 {
 367         struct crypto_gcm_ctx *ctx = crypto_tfm_ctx(tfm);
 368
 369         if (ctx->gf128 != NULL)
 370                 gf128mul_free_4k(ctx->gf128);
 371
 372         crypto_free_ablkcipher(ctx->ctr);
 373 }
 374
 375 static struct crypto_instance *crypto_gcm_alloc(struct rtattr **tb)
 376 {
 377         struct crypto_instance *inst;
 378         struct crypto_alg *ctr;
 379         struct crypto_alg *cipher;
 380         struct gcm_instance_ctx *ctx;
 381         int err;
 382         char ctr_name[CRYPTO_MAX_ALG_NAME];
 383
 384         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_AEAD);
 385         if (err)
 386                 return ERR_PTR(err);
 387
 388         cipher = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
 389                               CRYPTO_ALG_TYPE_MASK);
 390
 391         inst = ERR_PTR(PTR_ERR(cipher));
 392         if (IS_ERR(cipher))
 393                 return inst;
 394
 395         inst = ERR_PTR(ENAMETOOLONG);
 396         if (snprintf(
 397                     ctr_name, CRYPTO_MAX_ALG_NAME,
 398                     "ctr(%s,0,16,4)", cipher->cra_name) >= CRYPTO_MAX_ALG_NAME)
 399                 return inst;
 400
 401         ctr = crypto_alg_mod_lookup(ctr_name, CRYPTO_ALG_TYPE_BLKCIPHER,
 402                                     CRYPTO_ALG_TYPE_MASK);
 403
 404         if (IS_ERR(ctr))
 405                 return ERR_PTR(PTR_ERR(ctr));
 406
 407         if (cipher->cra_blocksize != 16)
 408                 goto out_put_ctr;
 409
 410         inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
 411         err = -ENOMEM;
 412         if (!inst)
 413                 goto out_put_ctr;
 414
 415         err = -ENAMETOOLONG;
 416         if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
 417                      "gcm(%s)", cipher->cra_name) >= CRYPTO_MAX_ALG_NAME ||
 418             snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 419                      "gcm(%s)", cipher->cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
 420                 goto err_free_inst;
 421
 422
 423         ctx = crypto_instance_ctx(inst);
 424         err = crypto_init_spawn(&ctx->ctr, ctr, inst, CRYPTO_ALG_TYPE_MASK);
 425         if (err)
 426                 goto err_free_inst;
 427
 428         inst->alg.cra_flags = CRYPTO_ALG_TYPE_AEAD | CRYPTO_ALG_ASYNC;
 429         inst->alg.cra_priority = ctr->cra_priority;
 430         inst->alg.cra_blocksize = 16;
 431         inst->alg.cra_alignmask = __alignof__(u32) - 1;
 432         inst->alg.cra_type = &crypto_aead_type;
 433         inst->alg.cra_aead.ivsize = 12;
 434         inst->alg.cra_aead.maxauthsize = 16;
 435         inst->alg.cra_ctxsize = sizeof(struct crypto_gcm_ctx);
 436         inst->alg.cra_init = crypto_gcm_init_tfm;
 437         inst->alg.cra_exit = crypto_gcm_exit_tfm;
 438         inst->alg.cra_aead.setkey = crypto_gcm_setkey;
 439         inst->alg.cra_aead.encrypt = crypto_gcm_encrypt;
 440         inst->alg.cra_aead.decrypt = crypto_gcm_decrypt;
 441
 442 out:
 443         crypto_mod_put(ctr);
 444         return inst;
 445 err_free_inst:
 446         kfree(inst);
 447 out_put_ctr:
 448         inst = ERR_PTR(err);
 449         goto out;
 450 }
 451
 452 static void crypto_gcm_free(struct crypto_instance *inst)
 453 {
 454         struct gcm_instance_ctx *ctx = crypto_instance_ctx(inst);
 455
 456         crypto_drop_spawn(&ctx->ctr);
 457         kfree(inst);
 458 }
 459
 460 static struct crypto_template crypto_gcm_tmpl = {
 461         .name = "gcm",
 462         .alloc = crypto_gcm_alloc,
 463         .free = crypto_gcm_free,
 464         .module = THIS_MODULE,
 465 };
 466
 467 static int __init crypto_gcm_module_init(void)
 468 {
 469         return crypto_register_template(&crypto_gcm_tmpl);
 470 }
 471
 472 static void __exit crypto_gcm_module_exit(void)
 473 {
 474         crypto_unregister_template(&crypto_gcm_tmpl);
 475 }
 476
 477 module_init(crypto_gcm_module_init);
 478 module_exit(crypto_gcm_module_exit);
 479
 480 MODULE_LICENSE("GPL");
 481 MODULE_DESCRIPTION("Galois/Counter Mode");
 482 MODULE_AUTHOR("Mikko Herranen <mh1@iki.fi>");