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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * echainiv: Encrypted Chain IV Generator4 *5 * This generator generates an IV based on a sequence number by multiplying6 * it with a salt and then encrypting it with the same key as used to encrypt7 * the plain text. This algorithm requires that the block size be equal8 * to the IV size. It is mainly useful for CBC.9 *10 * This generator can only be used by algorithms where authentication11 * is performed after encryption (i.e., authenc).12 *13 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>14 */15 16#include <crypto/internal/geniv.h>17#include <crypto/scatterwalk.h>18#include <crypto/skcipher.h>19#include <linux/err.h>20#include <linux/init.h>21#include <linux/kernel.h>22#include <linux/module.h>23#include <linux/slab.h>24#include <linux/string.h>25 26static int echainiv_encrypt(struct aead_request *req)27{28 struct crypto_aead *geniv = crypto_aead_reqtfm(req);29 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);30 struct aead_request *subreq = aead_request_ctx(req);31 __be64 nseqno;32 u64 seqno;33 u8 *info;34 unsigned int ivsize = crypto_aead_ivsize(geniv);35 int err;36 37 if (req->cryptlen < ivsize)38 return -EINVAL;39 40 aead_request_set_tfm(subreq, ctx->child);41 42 info = req->iv;43 44 if (req->src != req->dst) {45 SYNC_SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);46 47 skcipher_request_set_sync_tfm(nreq, ctx->sknull);48 skcipher_request_set_callback(nreq, req->base.flags,49 NULL, NULL);50 skcipher_request_set_crypt(nreq, req->src, req->dst,51 req->assoclen + req->cryptlen,52 NULL);53 54 err = crypto_skcipher_encrypt(nreq);55 if (err)56 return err;57 }58 59 aead_request_set_callback(subreq, req->base.flags,60 req->base.complete, req->base.data);61 aead_request_set_crypt(subreq, req->dst, req->dst,62 req->cryptlen, info);63 aead_request_set_ad(subreq, req->assoclen);64 65 memcpy(&nseqno, info + ivsize - 8, 8);66 seqno = be64_to_cpu(nseqno);67 memset(info, 0, ivsize);68 69 scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);70 71 do {72 u64 a;73 74 memcpy(&a, ctx->salt + ivsize - 8, 8);75 76 a |= 1;77 a *= seqno;78 79 memcpy(info + ivsize - 8, &a, 8);80 } while ((ivsize -= 8));81 82 return crypto_aead_encrypt(subreq);83}84 85static int echainiv_decrypt(struct aead_request *req)86{87 struct crypto_aead *geniv = crypto_aead_reqtfm(req);88 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);89 struct aead_request *subreq = aead_request_ctx(req);90 crypto_completion_t compl;91 void *data;92 unsigned int ivsize = crypto_aead_ivsize(geniv);93 94 if (req->cryptlen < ivsize)95 return -EINVAL;96 97 aead_request_set_tfm(subreq, ctx->child);98 99 compl = req->base.complete;100 data = req->base.data;101 102 aead_request_set_callback(subreq, req->base.flags, compl, data);103 aead_request_set_crypt(subreq, req->src, req->dst,104 req->cryptlen - ivsize, req->iv);105 aead_request_set_ad(subreq, req->assoclen + ivsize);106 107 scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);108 109 return crypto_aead_decrypt(subreq);110}111 112static int echainiv_aead_create(struct crypto_template *tmpl,113 struct rtattr **tb)114{115 struct aead_instance *inst;116 int err;117 118 inst = aead_geniv_alloc(tmpl, tb);119 120 if (IS_ERR(inst))121 return PTR_ERR(inst);122 123 err = -EINVAL;124 if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)125 goto free_inst;126 127 inst->alg.encrypt = echainiv_encrypt;128 inst->alg.decrypt = echainiv_decrypt;129 130 inst->alg.init = aead_init_geniv;131 inst->alg.exit = aead_exit_geniv;132 133 inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);134 inst->alg.base.cra_ctxsize += inst->alg.ivsize;135 136 err = aead_register_instance(tmpl, inst);137 if (err) {138free_inst:139 inst->free(inst);140 }141 return err;142}143 144static struct crypto_template echainiv_tmpl = {145 .name = "echainiv",146 .create = echainiv_aead_create,147 .module = THIS_MODULE,148};149 150static int __init echainiv_module_init(void)151{152 return crypto_register_template(&echainiv_tmpl);153}154 155static void __exit echainiv_module_exit(void)156{157 crypto_unregister_template(&echainiv_tmpl);158}159 160subsys_initcall(echainiv_module_init);161module_exit(echainiv_module_exit);162 163MODULE_LICENSE("GPL");164MODULE_DESCRIPTION("Encrypted Chain IV Generator");165MODULE_ALIAS_CRYPTO("echainiv");166