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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 be64_add_cpu(&iv->b, 1); 95 if (!iv->b) 96 be64_add_cpu(&iv->a, 1); 97 } 98 99 static inline void lrw_round(struct sinfo *s, void *dst, const void *src) 100 { 101 be128_xor(dst, &s->t, src); /* PP <- T xor P */ 102 s->fn(s->tfm, dst, dst); /* CC <- E(Key2,PP) */ 103 be128_xor(dst, dst, &s->t); /* C <- T xor CC */ 104 } 105 106 /* this returns the number of consequative 1 bits starting 107 * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */ 108 static inline int get_index128(be128 *block) 109 { 110 int x; 111 __be32 *p = (__be32 *) block; 112 113 for (p += 3, x = 0; x < 128; p--, x += 32) { 114 u32 val = be32_to_cpup(p); 115 116 if (!~val) 117 continue; 118 119 return x + ffz(val); 120 } 121 122 return x; 123 } 124 125 static int crypt(struct blkcipher_desc *d, 126 struct blkcipher_walk *w, struct priv *ctx, 127 void (*fn)(struct crypto_tfm *, u8 *, const u8 *)) 128 { 129 int err; 130 unsigned int avail; 131 const int bs = crypto_cipher_blocksize(ctx->child); 132 struct sinfo s = { 133 .tfm = crypto_cipher_tfm(ctx->child), 134 .fn = fn 135 }; 136 be128 *iv; 137 u8 *wsrc; 138 u8 *wdst; 139 140 err = blkcipher_walk_virt(d, w); 141 if (!(avail = w->nbytes)) 142 return err; 143 144 wsrc = w->src.virt.addr; 145 wdst = w->dst.virt.addr; 146 147 /* calculate first value of T */ 148 iv = (be128 *)w->iv; 149 s.t = *iv; 150 151 /* T <- I*Key2 */ 152 gf128mul_64k_bbe(&s.t, ctx->table); 153 154 goto first; 155 156 for (;;) { 157 do { 158 /* T <- I*Key2, using the optimization 159 * discussed in the specification */ 160 be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]); 161 inc(iv); 162 163 first: 164 lrw_round(&s, wdst, wsrc); 165 166 wsrc += bs; 167 wdst += bs; 168 } while ((avail -= bs) >= bs); 169 170 err = blkcipher_walk_done(d, w, avail); 171 if (!(avail = w->nbytes)) 172 break; 173 174 wsrc = w->src.virt.addr; 175 wdst = w->dst.virt.addr; 176 } 177 178 return err; 179 } 180 181 static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst, 182 struct scatterlist *src, unsigned int nbytes) 183 { 184 struct priv *ctx = crypto_blkcipher_ctx(desc->tfm); 185 struct blkcipher_walk w; 186 187 blkcipher_walk_init(&w, dst, src, nbytes); 188 return crypt(desc, &w, ctx, 189 crypto_cipher_alg(ctx->child)->cia_encrypt); 190 } 191 192 static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst, 193 struct scatterlist *src, unsigned int nbytes) 194 { 195 struct priv *ctx = crypto_blkcipher_ctx(desc->tfm); 196 struct blkcipher_walk w; 197 198 blkcipher_walk_init(&w, dst, src, nbytes); 199 return crypt(desc, &w, ctx, 200 crypto_cipher_alg(ctx->child)->cia_decrypt); 201 } 202 203 static int init_tfm(struct crypto_tfm *tfm) 204 { 205 struct crypto_cipher *cipher; 206 struct crypto_instance *inst = (void *)tfm->__crt_alg; 207 struct crypto_spawn *spawn = crypto_instance_ctx(inst); 208 struct priv *ctx = crypto_tfm_ctx(tfm); 209 u32 *flags = &tfm->crt_flags; 210 211 cipher = crypto_spawn_cipher(spawn); 212 if (IS_ERR(cipher)) 213 return PTR_ERR(cipher); 214 215 if (crypto_cipher_blocksize(cipher) != 16) { 216 *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN; 217 return -EINVAL; 218 } 219 220 ctx->child = cipher; 221 return 0; 222 } 223 224 static void exit_tfm(struct crypto_tfm *tfm) 225 { 226 struct priv *ctx = crypto_tfm_ctx(tfm); 227 if (ctx->table) 228 gf128mul_free_64k(ctx->table); 229 crypto_free_cipher(ctx->child); 230 } 231 232 static struct crypto_instance *alloc(struct rtattr **tb) 233 { 234 struct crypto_instance *inst; 235 struct crypto_alg *alg; 236 int err; 237 238 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER); 239 if (err) 240 return ERR_PTR(err); 241 242 alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, 243 CRYPTO_ALG_TYPE_MASK); 244 if (IS_ERR(alg)) 245 return ERR_CAST(alg); 246 247 inst = crypto_alloc_instance("lrw", alg); 248 if (IS_ERR(inst)) 249 goto out_put_alg; 250 251 inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER; 252 inst->alg.cra_priority = alg->cra_priority; 253 inst->alg.cra_blocksize = alg->cra_blocksize; 254 255 if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7; 256 else inst->alg.cra_alignmask = alg->cra_alignmask; 257 inst->alg.cra_type = &crypto_blkcipher_type; 258 259 if (!(alg->cra_blocksize % 4)) 260 inst->alg.cra_alignmask |= 3; 261 inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize; 262 inst->alg.cra_blkcipher.min_keysize = 263 alg->cra_cipher.cia_min_keysize + alg->cra_blocksize; 264 inst->alg.cra_blkcipher.max_keysize = 265 alg->cra_cipher.cia_max_keysize + alg->cra_blocksize; 266 267 inst->alg.cra_ctxsize = sizeof(struct priv); 268 269 inst->alg.cra_init = init_tfm; 270 inst->alg.cra_exit = exit_tfm; 271 272 inst->alg.cra_blkcipher.setkey = setkey; 273 inst->alg.cra_blkcipher.encrypt = encrypt; 274 inst->alg.cra_blkcipher.decrypt = decrypt; 275 276 out_put_alg: 277 crypto_mod_put(alg); 278 return inst; 279 } 280 281 static void free(struct crypto_instance *inst) 282 { 283 crypto_drop_spawn(crypto_instance_ctx(inst)); 284 kfree(inst); 285 } 286 287 static struct crypto_template crypto_tmpl = { 288 .name = "lrw", 289 .alloc = alloc, 290 .free = free, 291 .module = THIS_MODULE, 292 }; 293 294 static int __init crypto_module_init(void) 295 { 296 return crypto_register_template(&crypto_tmpl); 297 } 298 299 static void __exit crypto_module_exit(void) 300 { 301 crypto_unregister_template(&crypto_tmpl); 302 } 303 304 module_init(crypto_module_init); 305 module_exit(crypto_module_exit); 306 307 MODULE_LICENSE("GPL"); 308 MODULE_DESCRIPTION("LRW block cipher mode"); 309
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