1/* 2 * eseqiv: Encrypted Sequence Number 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 * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au> 10 * 11 * This program is free software; you can redistribute it and/or modify it 12 * under the terms of the GNU General Public License as published by the Free 13 * Software Foundation; either version 2 of the License, or (at your option) 14 * any later version. 15 * 16 */ 17 18#include <crypto/internal/skcipher.h> 19#include <crypto/rng.h> 20#include <crypto/scatterwalk.h> 21#include <linux/err.h> 22#include <linux/init.h> 23#include <linux/kernel.h> 24#include <linux/mm.h> 25#include <linux/module.h> 26#include <linux/scatterlist.h> 27#include <linux/spinlock.h> 28#include <linux/string.h> 29 30struct eseqiv_request_ctx { 31 struct scatterlist src[2]; 32 struct scatterlist dst[2]; 33 char tail[]; 34}; 35 36struct eseqiv_ctx { 37 spinlock_t lock; 38 unsigned int reqoff; 39 char salt[]; 40}; 41 42static void eseqiv_complete2(struct skcipher_givcrypt_request *req) 43{ 44 struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req); 45 struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req); 46 47 memcpy(req->giv, PTR_ALIGN((u8 *)reqctx->tail, 48 crypto_ablkcipher_alignmask(geniv) + 1), 49 crypto_ablkcipher_ivsize(geniv)); 50} 51 52static void eseqiv_complete(struct crypto_async_request *base, int err) 53{ 54 struct skcipher_givcrypt_request *req = base->data; 55 56 if (err) 57 goto out; 58 59 eseqiv_complete2(req); 60 61out: 62 skcipher_givcrypt_complete(req, err); 63} 64 65static int eseqiv_givencrypt(struct skcipher_givcrypt_request *req) 66{ 67 struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req); 68 struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv); 69 struct eseqiv_request_ctx *reqctx = skcipher_givcrypt_reqctx(req); 70 struct ablkcipher_request *subreq; 71 crypto_completion_t compl; 72 void *data; 73 struct scatterlist *osrc, *odst; 74 struct scatterlist *dst; 75 struct page *srcp; 76 struct page *dstp; 77 u8 *giv; 78 u8 *vsrc; 79 u8 *vdst; 80 __be64 seq; 81 unsigned int ivsize; 82 unsigned int len; 83 int err; 84 85 subreq = (void *)(reqctx->tail + ctx->reqoff); 86 ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv)); 87 88 giv = req->giv; 89 compl = req->creq.base.complete; 90 data = req->creq.base.data; 91 92 osrc = req->creq.src; 93 odst = req->creq.dst; 94 srcp = sg_page(osrc); 95 dstp = sg_page(odst); 96 vsrc = PageHighMem(srcp) ? NULL : page_address(srcp) + osrc->offset; 97 vdst = PageHighMem(dstp) ? NULL : page_address(dstp) + odst->offset; 98 99 ivsize = crypto_ablkcipher_ivsize(geniv); 100 101 if (vsrc != giv + ivsize && vdst != giv + ivsize) { 102 giv = PTR_ALIGN((u8 *)reqctx->tail, 103 crypto_ablkcipher_alignmask(geniv) + 1); 104 compl = eseqiv_complete; 105 data = req; 106 } 107 108 ablkcipher_request_set_callback(subreq, req->creq.base.flags, compl, 109 data); 110 111 sg_init_table(reqctx->src, 2); 112 sg_set_buf(reqctx->src, giv, ivsize); 113 scatterwalk_crypto_chain(reqctx->src, osrc, vsrc == giv + ivsize, 2); 114 115 dst = reqctx->src; 116 if (osrc != odst) { 117 sg_init_table(reqctx->dst, 2); 118 sg_set_buf(reqctx->dst, giv, ivsize); 119 scatterwalk_crypto_chain(reqctx->dst, odst, vdst == giv + ivsize, 2); 120 121 dst = reqctx->dst; 122 } 123 124 ablkcipher_request_set_crypt(subreq, reqctx->src, dst, 125 req->creq.nbytes + ivsize, 126 req->creq.info); 127 128 memcpy(req->creq.info, ctx->salt, ivsize); 129 130 len = ivsize; 131 if (ivsize > sizeof(u64)) { 132 memset(req->giv, 0, ivsize - sizeof(u64)); 133 len = sizeof(u64); 134 } 135 seq = cpu_to_be64(req->seq); 136 memcpy(req->giv + ivsize - len, &seq, len); 137 138 err = crypto_ablkcipher_encrypt(subreq); 139 if (err) 140 goto out; 141 142 if (giv != req->giv) 143 eseqiv_complete2(req); 144 145out: 146 return err; 147} 148 149static int eseqiv_givencrypt_first(struct skcipher_givcrypt_request *req) 150{ 151 struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req); 152 struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv); 153 int err = 0; 154 155 spin_lock_bh(&ctx->lock); 156 if (crypto_ablkcipher_crt(geniv)->givencrypt != eseqiv_givencrypt_first) 157 goto unlock; 158 159 crypto_ablkcipher_crt(geniv)->givencrypt = eseqiv_givencrypt; 160 err = crypto_rng_get_bytes(crypto_default_rng, ctx->salt, 161 crypto_ablkcipher_ivsize(geniv)); 162 163unlock: 164 spin_unlock_bh(&ctx->lock); 165 166 if (err) 167 return err; 168 169 return eseqiv_givencrypt(req); 170} 171 172static int eseqiv_init(struct crypto_tfm *tfm) 173{ 174 struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm); 175 struct eseqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv); 176 unsigned long alignmask; 177 unsigned int reqsize; 178 179 spin_lock_init(&ctx->lock); 180 181 alignmask = crypto_tfm_ctx_alignment() - 1; 182 reqsize = sizeof(struct eseqiv_request_ctx); 183 184 if (alignmask & reqsize) { 185 alignmask &= reqsize; 186 alignmask--; 187 } 188 189 alignmask = ~alignmask; 190 alignmask &= crypto_ablkcipher_alignmask(geniv); 191 192 reqsize += alignmask; 193 reqsize += crypto_ablkcipher_ivsize(geniv); 194 reqsize = ALIGN(reqsize, crypto_tfm_ctx_alignment()); 195 196 ctx->reqoff = reqsize - sizeof(struct eseqiv_request_ctx); 197 198 tfm->crt_ablkcipher.reqsize = reqsize + 199 sizeof(struct ablkcipher_request); 200 201 return skcipher_geniv_init(tfm); 202} 203 204static struct crypto_template eseqiv_tmpl; 205 206static struct crypto_instance *eseqiv_alloc(struct rtattr **tb) 207{ 208 struct crypto_instance *inst; 209 int err; 210 211 err = crypto_get_default_rng(); 212 if (err) 213 return ERR_PTR(err); 214 215 inst = skcipher_geniv_alloc(&eseqiv_tmpl, tb, 0, 0); 216 if (IS_ERR(inst)) 217 goto put_rng; 218 219 err = -EINVAL; 220 if (inst->alg.cra_ablkcipher.ivsize != inst->alg.cra_blocksize) 221 goto free_inst; 222 223 inst->alg.cra_ablkcipher.givencrypt = eseqiv_givencrypt_first; 224 225 inst->alg.cra_init = eseqiv_init; 226 inst->alg.cra_exit = skcipher_geniv_exit; 227 228 inst->alg.cra_ctxsize = sizeof(struct eseqiv_ctx); 229 inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize; 230 231out: 232 return inst; 233 234free_inst: 235 skcipher_geniv_free(inst); 236 inst = ERR_PTR(err); 237put_rng: 238 crypto_put_default_rng(); 239 goto out; 240} 241 242static void eseqiv_free(struct crypto_instance *inst) 243{ 244 skcipher_geniv_free(inst); 245 crypto_put_default_rng(); 246} 247 248static struct crypto_template eseqiv_tmpl = { 249 .name = "eseqiv", 250 .alloc = eseqiv_alloc, 251 .free = eseqiv_free, 252 .module = THIS_MODULE, 253}; 254 255static int __init eseqiv_module_init(void) 256{ 257 return crypto_register_template(&eseqiv_tmpl); 258} 259 260static void __exit eseqiv_module_exit(void) 261{ 262 crypto_unregister_template(&eseqiv_tmpl); 263} 264 265module_init(eseqiv_module_init); 266module_exit(eseqiv_module_exit); 267 268MODULE_LICENSE("GPL"); 269MODULE_DESCRIPTION("Encrypted Sequence Number IV Generator"); 270MODULE_ALIAS_CRYPTO("eseqiv"); 271