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 ^ 0x78, b); 49 } 50 51 static int setkey(struct crypto_tfm *parent, const u8 *key, 52 unsigned int keylen) 53 { 54 struct priv *ctx = crypto_tfm_ctx(parent); 55 struct crypto_cipher *child = ctx->child; 56 int err, i; 57 be128 tmp = { 0 }; 58 int bsize = crypto_cipher_blocksize(child); 59 60 crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK); 61 crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) & 62 CRYPTO_TFM_REQ_MASK); 63 if ((err = crypto_cipher_setkey(child, key, keylen - bsize))) 64 return err; 65 crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) & 66 CRYPTO_TFM_RES_MASK); 67 68 if (ctx->table) 69 gf128mul_free_64k(ctx->table); 70 71 /* initialize multiplication table for Key2 */ 72 ctx->table = gf128mul_init_64k_bbe((be128 *)(key + keylen - bsize)); 73 if (!ctx->table) 74 return -ENOMEM; 75 76 /* initialize optimization table */ 77 for (i = 0; i < 128; i++) { 78 setbit128_bbe(&tmp, i); 79 ctx->mulinc[i] = tmp; 80 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table); 81 } 82 83 return 0; 84 } 85 86 struct sinfo { 87 be128 t; 88 struct crypto_tfm *tfm; 89 void (*fn)(struct crypto_tfm *, u8 *, const u8 *); 90 }; 91 92 static inline void inc(be128 *iv) 93 { 94 if (!(iv->b = cpu_to_be64(be64_to_cpu(iv->b) + 1))) 95 iv->a = cpu_to_be64(be64_to_cpu(iv->a) + 1); 96 } 97 98 static inline void lrw_round(struct sinfo *s, void *dst, const void *src) 99 { 100 be128_xor(dst, &s->t, src); /* PP <- T xor P */ 101 s->fn(s->tfm, dst, dst); /* CC <- E(Key2,PP) */ 102 be128_xor(dst, dst, &s->t); /* C <- T xor CC */ 103 } 104 105 /* this returns the number of consequative 1 bits starting 106 * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */ 107 static inline int get_index128(be128 *block) 108 { 109 int x; 110 __be32 *p = (__be32 *) block; 111 112 for (p += 3, x = 0; x < 128; p--, x += 32) { 113 u32 val = be32_to_cpup(p); 114 115 if (!~val) 116 continue; 117 118 return x + ffz(val); 119 } 120 121 return x; 122 } 123 124 static int crypt(struct blkcipher_desc *d, 125 struct blkcipher_walk *w, struct priv *ctx, 126 void (*fn)(struct crypto_tfm *, u8 *, const u8 *)) 127 { 128 int err; 129 unsigned int avail; 130 const int bs = crypto_cipher_blocksize(ctx->child); 131 struct sinfo s = { 132 .tfm = crypto_cipher_tfm(ctx->child), 133 .fn = fn 134 }; 135 be128 *iv; 136 u8 *wsrc; 137 u8 *wdst; 138 139 err = blkcipher_walk_virt(d, w); 140 if (!(avail = w->nbytes)) 141 return err; 142 143 wsrc = w->src.virt.addr; 144 wdst = w->dst.virt.addr; 145 146 /* calculate first value of T */ 147 iv = (be128 *)w->iv; 148 s.t = *iv; 149 150 /* T <- I*Key2 */ 151 gf128mul_64k_bbe(&s.t, ctx->table); 152 153 goto first; 154 155 for (;;) { 156 do { 157 /* T <- I*Key2, using the optimization 158 * discussed in the specification */ 159 be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]); 160 inc(iv); 161 162 first: 163 lrw_round(&s, wdst, wsrc); 164 165 wsrc += bs; 166 wdst += bs; 167 } while ((avail -= bs) >= bs); 168 169 err = blkcipher_walk_done(d, w, avail); 170 if (!(avail = w->nbytes)) 171 break; 172 173 wsrc = w->src.virt.addr; 174 wdst = w->dst.virt.addr; 175 } 176 177 return err; 178 } 179 180 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst, 181 struct scatterlist *src, unsigned int nbytes) 182 { 183 struct priv *ctx = crypto_blkcipher_ctx(desc->tfm); 184 struct blkcipher_walk w; 185 186 blkcipher_walk_init(&w, dst, src, nbytes); 187 return crypt(desc, &w, ctx, 188 crypto_cipher_alg(ctx->child)->cia_encrypt); 189 } 190 191 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst, 192 struct scatterlist *src, unsigned int nbytes) 193 { 194 struct priv *ctx = crypto_blkcipher_ctx(desc->tfm); 195 struct blkcipher_walk w; 196 197 blkcipher_walk_init(&w, dst, src, nbytes); 198 return crypt(desc, &w, ctx, 199 crypto_cipher_alg(ctx->child)->cia_decrypt); 200 } 201 202 static int init_tfm(struct crypto_tfm *tfm) 203 { 204 struct crypto_cipher *cipher; 205 struct crypto_instance *inst = (void *)tfm->__crt_alg; 206 struct crypto_spawn *spawn = crypto_instance_ctx(inst); 207 struct priv *ctx = crypto_tfm_ctx(tfm); 208 u32 *flags = &tfm->crt_flags; 209 210 cipher = crypto_spawn_cipher(spawn); 211 if (IS_ERR(cipher)) 212 return PTR_ERR(cipher); 213 214 if (crypto_cipher_blocksize(cipher) != 16) { 215 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN; 216 return -EINVAL; 217 } 218 219 ctx->child = cipher; 220 return 0; 221 } 222 223 static void exit_tfm(struct crypto_tfm *tfm) 224 { 225 struct priv *ctx = crypto_tfm_ctx(tfm); 226 if (ctx->table) 227 gf128mul_free_64k(ctx->table); 228 crypto_free_cipher(ctx->child); 229 } 230 231 static struct crypto_instance *alloc(struct rtattr **tb) 232 { 233 struct crypto_instance *inst; 234 struct crypto_alg *alg; 235 int err; 236 237 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER); 238 if (err) 239 return ERR_PTR(err); 240 241 alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, 242 CRYPTO_ALG_TYPE_MASK); 243 if (IS_ERR(alg)) 244 return ERR_PTR(PTR_ERR(alg)); 245 246 inst = crypto_alloc_instance("lrw", alg); 247 if (IS_ERR(inst)) 248 goto out_put_alg; 249 250 inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER; 251 inst->alg.cra_priority = alg->cra_priority; 252 inst->alg.cra_blocksize = alg->cra_blocksize; 253 254 if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7; 255 else inst->alg.cra_alignmask = alg->cra_alignmask; 256 inst->alg.cra_type = &crypto_blkcipher_type; 257 258 if (!(alg->cra_blocksize % 4)) 259 inst->alg.cra_alignmask |= 3; 260 inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize; 261 inst->alg.cra_blkcipher.min_keysize = 262 alg->cra_cipher.cia_min_keysize + alg->cra_blocksize; 263 inst->alg.cra_blkcipher.max_keysize = 264 alg->cra_cipher.cia_max_keysize + alg->cra_blocksize; 265 266 inst->alg.cra_ctxsize = sizeof(struct priv); 267 268 inst->alg.cra_init = init_tfm; 269 inst->alg.cra_exit = exit_tfm; 270 271 inst->alg.cra_blkcipher.setkey = setkey; 272 inst->alg.cra_blkcipher.encrypt = encrypt; 273 inst->alg.cra_blkcipher.decrypt = decrypt; 274 275 out_put_alg: 276 crypto_mod_put(alg); 277 return inst; 278 } 279 280 static void free(struct crypto_instance *inst) 281 { 282 crypto_drop_spawn(crypto_instance_ctx(inst)); 283 kfree(inst); 284 } 285 286 static struct crypto_template crypto_tmpl = { 287 .name = "lrw", 288 .alloc = alloc, 289 .free = free, 290 .module = THIS_MODULE, 291 }; 292 293 static int __init crypto_module_init(void) 294 { 295 return crypto_register_template(&crypto_tmpl); 296 } 297 298 static void __exit crypto_module_exit(void) 299 { 300 crypto_unregister_template(&crypto_tmpl); 301 } 302 303 module_init(crypto_module_init); 304 module_exit(crypto_module_exit); 305 306 MODULE_LICENSE("GPL"); 307 MODULE_DESCRIPTION("LRW block cipher mode"); 308