1 /* 2 * echainiv: Encrypted Chain IV Generator 3 * 4 * This generator generates an IV based on a sequence number by xoring it 5 * with a salt and then encrypting it with the same key as used to encrypt 6 * the plain text. This algorithm requires that the block size be equal 7 * to the IV size. It is mainly useful for CBC. 8 * 9 * This generator can only be used by algorithms where authentication 10 * is performed after encryption (i.e., authenc). 11 * 12 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> 13 * 14 * This program is free software; you can redistribute it and/or modify it 15 * under the terms of the GNU General Public License as published by the Free 16 * Software Foundation; either version 2 of the License, or (at your option) 17 * any later version. 18 * 19 */ 20 21 #include <crypto/internal/geniv.h> 22 #include <crypto/null.h> 23 #include <crypto/rng.h> 24 #include <crypto/scatterwalk.h> 25 #include <linux/err.h> 26 #include <linux/init.h> 27 #include <linux/kernel.h> 28 #include <linux/mm.h> 29 #include <linux/module.h> 30 #include <linux/percpu.h> 31 #include <linux/spinlock.h> 32 #include <linux/string.h> 33 34 #define MAX_IV_SIZE 16 35 36 struct echainiv_ctx { 37 /* aead_geniv_ctx must be first the element */ 38 struct aead_geniv_ctx geniv; 39 struct crypto_blkcipher *null; 40 u8 salt[] __attribute__ ((aligned(__alignof__(u32)))); 41 }; 42 43 static DEFINE_PER_CPU(u32 [MAX_IV_SIZE / sizeof(u32)], echainiv_iv); 44 45 /* We don't care if we get preempted and read/write IVs from the next CPU. */ 46 static void echainiv_read_iv(u8 *dst, unsigned size) 47 { 48 u32 *a = (u32 *)dst; 49 u32 __percpu *b = echainiv_iv; 50 51 for (; size >= 4; size -= 4) { 52 *a++ = this_cpu_read(*b); 53 b++; 54 } 55 } 56 57 static void echainiv_write_iv(const u8 *src, unsigned size) 58 { 59 const u32 *a = (const u32 *)src; 60 u32 __percpu *b = echainiv_iv; 61 62 for (; size >= 4; size -= 4) { 63 this_cpu_write(*b, *a); 64 a++; 65 b++; 66 } 67 } 68 69 static void echainiv_encrypt_complete2(struct aead_request *req, int err) 70 { 71 struct aead_request *subreq = aead_request_ctx(req); 72 struct crypto_aead *geniv; 73 unsigned int ivsize; 74 75 if (err == -EINPROGRESS) 76 return; 77 78 if (err) 79 goto out; 80 81 geniv = crypto_aead_reqtfm(req); 82 ivsize = crypto_aead_ivsize(geniv); 83 84 echainiv_write_iv(subreq->iv, ivsize); 85 86 if (req->iv != subreq->iv) 87 memcpy(req->iv, subreq->iv, ivsize); 88 89 out: 90 if (req->iv != subreq->iv) 91 kzfree(subreq->iv); 92 } 93 94 static void echainiv_encrypt_complete(struct crypto_async_request *base, 95 int err) 96 { 97 struct aead_request *req = base->data; 98 99 echainiv_encrypt_complete2(req, err); 100 aead_request_complete(req, err); 101 } 102 103 static int echainiv_encrypt(struct aead_request *req) 104 { 105 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 106 struct echainiv_ctx *ctx = crypto_aead_ctx(geniv); 107 struct aead_request *subreq = aead_request_ctx(req); 108 crypto_completion_t compl; 109 void *data; 110 u8 *info; 111 unsigned int ivsize = crypto_aead_ivsize(geniv); 112 int err; 113 114 if (req->cryptlen < ivsize) 115 return -EINVAL; 116 117 aead_request_set_tfm(subreq, ctx->geniv.child); 118 119 compl = echainiv_encrypt_complete; 120 data = req; 121 info = req->iv; 122 123 if (req->src != req->dst) { 124 struct blkcipher_desc desc = { 125 .tfm = ctx->null, 126 }; 127 128 err = crypto_blkcipher_encrypt( 129 &desc, req->dst, req->src, 130 req->assoclen + req->cryptlen); 131 if (err) 132 return err; 133 } 134 135 if (unlikely(!IS_ALIGNED((unsigned long)info, 136 crypto_aead_alignmask(geniv) + 1))) { 137 info = kmalloc(ivsize, req->base.flags & 138 CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL: 139 GFP_ATOMIC); 140 if (!info) 141 return -ENOMEM; 142 143 memcpy(info, req->iv, ivsize); 144 } 145 146 aead_request_set_callback(subreq, req->base.flags, compl, data); 147 aead_request_set_crypt(subreq, req->dst, req->dst, 148 req->cryptlen - ivsize, info); 149 aead_request_set_ad(subreq, req->assoclen + ivsize); 150 151 crypto_xor(info, ctx->salt, ivsize); 152 scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); 153 echainiv_read_iv(info, ivsize); 154 155 err = crypto_aead_encrypt(subreq); 156 echainiv_encrypt_complete2(req, err); 157 return err; 158 } 159 160 static int echainiv_decrypt(struct aead_request *req) 161 { 162 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 163 struct echainiv_ctx *ctx = crypto_aead_ctx(geniv); 164 struct aead_request *subreq = aead_request_ctx(req); 165 crypto_completion_t compl; 166 void *data; 167 unsigned int ivsize = crypto_aead_ivsize(geniv); 168 169 if (req->cryptlen < ivsize + crypto_aead_authsize(geniv)) 170 return -EINVAL; 171 172 aead_request_set_tfm(subreq, ctx->geniv.child); 173 174 compl = req->base.complete; 175 data = req->base.data; 176 177 aead_request_set_callback(subreq, req->base.flags, compl, data); 178 aead_request_set_crypt(subreq, req->src, req->dst, 179 req->cryptlen - ivsize, req->iv); 180 aead_request_set_ad(subreq, req->assoclen + ivsize); 181 182 scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); 183 if (req->src != req->dst) 184 scatterwalk_map_and_copy(req->iv, req->dst, 185 req->assoclen, ivsize, 1); 186 187 return crypto_aead_decrypt(subreq); 188 } 189 190 static int echainiv_init(struct crypto_tfm *tfm) 191 { 192 struct crypto_aead *geniv = __crypto_aead_cast(tfm); 193 struct echainiv_ctx *ctx = crypto_aead_ctx(geniv); 194 int err; 195 196 spin_lock_init(&ctx->geniv.lock); 197 198 crypto_aead_set_reqsize(geniv, sizeof(struct aead_request)); 199 200 err = crypto_get_default_rng(); 201 if (err) 202 goto out; 203 204 err = crypto_rng_get_bytes(crypto_default_rng, ctx->salt, 205 crypto_aead_ivsize(geniv)); 206 crypto_put_default_rng(); 207 if (err) 208 goto out; 209 210 ctx->null = crypto_get_default_null_skcipher(); 211 err = PTR_ERR(ctx->null); 212 if (IS_ERR(ctx->null)) 213 goto out; 214 215 err = aead_geniv_init(tfm); 216 if (err) 217 goto drop_null; 218 219 ctx->geniv.child = geniv->child; 220 geniv->child = geniv; 221 222 out: 223 return err; 224 225 drop_null: 226 crypto_put_default_null_skcipher(); 227 goto out; 228 } 229 230 static void echainiv_exit(struct crypto_tfm *tfm) 231 { 232 struct echainiv_ctx *ctx = crypto_tfm_ctx(tfm); 233 234 crypto_free_aead(ctx->geniv.child); 235 crypto_put_default_null_skcipher(); 236 } 237 238 static int echainiv_aead_create(struct crypto_template *tmpl, 239 struct rtattr **tb) 240 { 241 struct aead_instance *inst; 242 struct crypto_aead_spawn *spawn; 243 struct aead_alg *alg; 244 int err; 245 246 inst = aead_geniv_alloc(tmpl, tb, 0, 0); 247 248 if (IS_ERR(inst)) 249 return PTR_ERR(inst); 250 251 spawn = aead_instance_ctx(inst); 252 alg = crypto_spawn_aead_alg(spawn); 253 254 if (alg->base.cra_aead.encrypt) 255 goto done; 256 257 err = -EINVAL; 258 if (inst->alg.ivsize & (sizeof(u32) - 1) || 259 inst->alg.ivsize > MAX_IV_SIZE) 260 goto free_inst; 261 262 inst->alg.encrypt = echainiv_encrypt; 263 inst->alg.decrypt = echainiv_decrypt; 264 265 inst->alg.base.cra_init = echainiv_init; 266 inst->alg.base.cra_exit = echainiv_exit; 267 268 inst->alg.base.cra_alignmask |= __alignof__(u32) - 1; 269 inst->alg.base.cra_ctxsize = sizeof(struct echainiv_ctx); 270 inst->alg.base.cra_ctxsize += inst->alg.ivsize; 271 272 done: 273 err = aead_register_instance(tmpl, inst); 274 if (err) 275 goto free_inst; 276 277 out: 278 return err; 279 280 free_inst: 281 aead_geniv_free(inst); 282 goto out; 283 } 284 285 static void echainiv_free(struct crypto_instance *inst) 286 { 287 aead_geniv_free(aead_instance(inst)); 288 } 289 290 static struct crypto_template echainiv_tmpl = { 291 .name = "echainiv", 292 .create = echainiv_aead_create, 293 .free = echainiv_free, 294 .module = THIS_MODULE, 295 }; 296 297 static int __init echainiv_module_init(void) 298 { 299 return crypto_register_template(&echainiv_tmpl); 300 } 301 302 static void __exit echainiv_module_exit(void) 303 { 304 crypto_unregister_template(&echainiv_tmpl); 305 } 306 307 module_init(echainiv_module_init); 308 module_exit(echainiv_module_exit); 309 310 MODULE_LICENSE("GPL"); 311 MODULE_DESCRIPTION("Encrypted Chain IV Generator"); 312 MODULE_ALIAS_CRYPTO("echainiv"); 313