1 /* LRW: as defined by Cyril Guyot in 2 * http://grouper.ieee.org/groups/1619/email/pdf00017.pdf 3 * 4 * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org> 5 * 6 * Based om ecb.c 7 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au> 8 * 9 * This program is free software; you can redistribute it and/or modify it 10 * under the terms of the GNU General Public License as published by the Free 11 * Software Foundation; either version 2 of the License, or (at your option) 12 * any later version. 13 */ 14 /* This implementation is checked against the test vectors in the above 15 * document and by a test vector provided by Ken Buchanan at 16 * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html 17 * 18 * The test vectors are included in the testing module tcrypt.[ch] */ 19 #include <crypto/algapi.h> 20 #include <linux/err.h> 21 #include <linux/init.h> 22 #include <linux/kernel.h> 23 #include <linux/module.h> 24 #include <linux/scatterlist.h> 25 #include <linux/slab.h> 26 27 #include <crypto/b128ops.h> 28 #include <crypto/gf128mul.h> 29 30 struct priv { 31 struct crypto_cipher *child; 32 /* optimizes multiplying a random (non incrementing, as at the 33 * start of a new sector) value with key2, we could also have 34 * used 4k optimization tables or no optimization at all. In the 35 * latter case we would have to store key2 here */ 36 struct gf128mul_64k *table; 37 /* stores: 38 * key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 }, 39 * key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 } 40 * key2*{ 0,0,...1,1,1,1,1 }, etc 41 * needed for optimized multiplication of incrementing values 42 * with key2 */ 43 be128 mulinc[128]; 44 }; 45 46 static inline void setbit128_bbe(void *b, int bit) 47 { 48 __set_bit(bit ^ (0x80 - 49 #ifdef __BIG_ENDIAN 50 BITS_PER_LONG 51 #else 52 BITS_PER_BYTE 53 #endif 54 ), b); 55 } 56 57 static int setkey(struct crypto_tfm *parent, const u8 *key, 58 unsigned int keylen) 59 { 60 struct priv *ctx = crypto_tfm_ctx(parent); 61 struct crypto_cipher *child = ctx->child; 62 int err, i; 63 be128 tmp = { 0 }; 64 int bsize = crypto_cipher_blocksize(child); 65 66 crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); 67 crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) & 68 CRYPTO_TFM_REQ_MASK); 69 if ((err = crypto_cipher_setkey(child, key, keylen - bsize))) 70 return err; 71 crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) & 72 CRYPTO_TFM_RES_MASK); 73 74 if (ctx->table) 75 gf128mul_free_64k(ctx->table); 76 77 /* initialize multiplication table for Key2 */ 78 ctx->table = gf128mul_init_64k_bbe((be128 *)(key + keylen - bsize)); 79 if (!ctx->table) 80 return -ENOMEM; 81 82 /* initialize optimization table */ 83 for (i = 0; i < 128; i++) { 84 setbit128_bbe(&tmp, i); 85 ctx->mulinc[i] = tmp; 86 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table); 87 } 88 89 return 0; 90 } 91 92 struct sinfo { 93 be128 t; 94 struct crypto_tfm *tfm; 95 void (*fn)(struct crypto_tfm *, u8 *, const u8 *); 96 }; 97 98 static inline void inc(be128 *iv) 99 { 100 be64_add_cpu(&iv->b, 1); 101 if (!iv->b) 102 be64_add_cpu(&iv->a, 1); 103 } 104 105 static inline void lrw_round(struct sinfo *s, void *dst, const void *src) 106 { 107 be128_xor(dst, &s->t, src); /* PP <- T xor P */ 108 s->fn(s->tfm, dst, dst); /* CC <- E(Key2,PP) */ 109 be128_xor(dst, dst, &s->t); /* C <- T xor CC */ 110 } 111 112 /* this returns the number of consequative 1 bits starting 113 * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */ 114 static inline int get_index128(be128 *block) 115 { 116 int x; 117 __be32 *p = (__be32 *) block; 118 119 for (p += 3, x = 0; x < 128; p--, x += 32) { 120 u32 val = be32_to_cpup(p); 121 122 if (!~val) 123 continue; 124 125 return x + ffz(val); 126 } 127 128 return x; 129 } 130 131 static int crypt(struct blkcipher_desc *d, 132 struct blkcipher_walk *w, struct priv *ctx, 133 void (*fn)(struct crypto_tfm *, u8 *, const u8 *)) 134 { 135 int err; 136 unsigned int avail; 137 const int bs = crypto_cipher_blocksize(ctx->child); 138 struct sinfo s = { 139 .tfm = crypto_cipher_tfm(ctx->child), 140 .fn = fn 141 }; 142 be128 *iv; 143 u8 *wsrc; 144 u8 *wdst; 145 146 err = blkcipher_walk_virt(d, w); 147 if (!(avail = w->nbytes)) 148 return err; 149 150 wsrc = w->src.virt.addr; 151 wdst = w->dst.virt.addr; 152 153 /* calculate first value of T */ 154 iv = (be128 *)w->iv; 155 s.t = *iv; 156 157 /* T <- I*Key2 */ 158 gf128mul_64k_bbe(&s.t, ctx->table); 159 160 goto first; 161 162 for (;;) { 163 do { 164 /* T <- I*Key2, using the optimization 165 * discussed in the specification */ 166 be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]); 167 inc(iv); 168 169 first: 170 lrw_round(&s, wdst, wsrc); 171 172 wsrc += bs; 173 wdst += bs; 174 } while ((avail -= bs) >= bs); 175 176 err = blkcipher_walk_done(d, w, avail); 177 if (!(avail = w->nbytes)) 178 break; 179 180 wsrc = w->src.virt.addr; 181 wdst = w->dst.virt.addr; 182 } 183 184 return err; 185 } 186 187 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst, 188 struct scatterlist *src, unsigned int nbytes) 189 { 190 struct priv *ctx = crypto_blkcipher_ctx(desc->tfm); 191 struct blkcipher_walk w; 192 193 blkcipher_walk_init(&w, dst, src, nbytes); 194 return crypt(desc, &w, ctx, 195 crypto_cipher_alg(ctx->child)->cia_encrypt); 196 } 197 198 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst, 199 struct scatterlist *src, unsigned int nbytes) 200 { 201 struct priv *ctx = crypto_blkcipher_ctx(desc->tfm); 202 struct blkcipher_walk w; 203 204 blkcipher_walk_init(&w, dst, src, nbytes); 205 return crypt(desc, &w, ctx, 206 crypto_cipher_alg(ctx->child)->cia_decrypt); 207 } 208 209 static int init_tfm(struct crypto_tfm *tfm) 210 { 211 struct crypto_cipher *cipher; 212 struct crypto_instance *inst = (void *)tfm->__crt_alg; 213 struct crypto_spawn *spawn = crypto_instance_ctx(inst); 214 struct priv *ctx = crypto_tfm_ctx(tfm); 215 u32 *flags = &tfm->crt_flags; 216 217 cipher = crypto_spawn_cipher(spawn); 218 if (IS_ERR(cipher)) 219 return PTR_ERR(cipher); 220 221 if (crypto_cipher_blocksize(cipher) != 16) { 222 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN; 223 return -EINVAL; 224 } 225 226 ctx->child = cipher; 227 return 0; 228 } 229 230 static void exit_tfm(struct crypto_tfm *tfm) 231 { 232 struct priv *ctx = crypto_tfm_ctx(tfm); 233 if (ctx->table) 234 gf128mul_free_64k(ctx->table); 235 crypto_free_cipher(ctx->child); 236 } 237 238 static struct crypto_instance *alloc(struct rtattr **tb) 239 { 240 struct crypto_instance *inst; 241 struct crypto_alg *alg; 242 int err; 243 244 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER); 245 if (err) 246 return ERR_PTR(err); 247 248 alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, 249 CRYPTO_ALG_TYPE_MASK); 250 if (IS_ERR(alg)) 251 return ERR_CAST(alg); 252 253 inst = crypto_alloc_instance("lrw", alg); 254 if (IS_ERR(inst)) 255 goto out_put_alg; 256 257 inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER; 258 inst->alg.cra_priority = alg->cra_priority; 259 inst->alg.cra_blocksize = alg->cra_blocksize; 260 261 if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7; 262 else inst->alg.cra_alignmask = alg->cra_alignmask; 263 inst->alg.cra_type = &crypto_blkcipher_type; 264 265 if (!(alg->cra_blocksize % 4)) 266 inst->alg.cra_alignmask |= 3; 267 inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize; 268 inst->alg.cra_blkcipher.min_keysize = 269 alg->cra_cipher.cia_min_keysize + alg->cra_blocksize; 270 inst->alg.cra_blkcipher.max_keysize = 271 alg->cra_cipher.cia_max_keysize + alg->cra_blocksize; 272 273 inst->alg.cra_ctxsize = sizeof(struct priv); 274 275 inst->alg.cra_init = init_tfm; 276 inst->alg.cra_exit = exit_tfm; 277 278 inst->alg.cra_blkcipher.setkey = setkey; 279 inst->alg.cra_blkcipher.encrypt = encrypt; 280 inst->alg.cra_blkcipher.decrypt = decrypt; 281 282 out_put_alg: 283 crypto_mod_put(alg); 284 return inst; 285 } 286 287 static void free(struct crypto_instance *inst) 288 { 289 crypto_drop_spawn(crypto_instance_ctx(inst)); 290 kfree(inst); 291 } 292 293 static struct crypto_template crypto_tmpl = { 294 .name = "lrw", 295 .alloc = alloc, 296 .free = free, 297 .module = THIS_MODULE, 298 }; 299 300 static int __init crypto_module_init(void) 301 { 302 return crypto_register_template(&crypto_tmpl); 303 } 304 305 static void __exit crypto_module_exit(void) 306 { 307 crypto_unregister_template(&crypto_tmpl); 308 } 309 310 module_init(crypto_module_init); 311 module_exit(crypto_module_exit); 312 313 MODULE_LICENSE("GPL"); 314 MODULE_DESCRIPTION("LRW block cipher mode"); 315