166 lines
4.1 KiB
C
166 lines
4.1 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* echainiv: Encrypted Chain IV Generator
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*
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* This generator generates an IV based on a sequence number by multiplying
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* it with a salt and then encrypting it with the same key as used to encrypt
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* the plain text. This algorithm requires that the block size be equal
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* to the IV size. It is mainly useful for CBC.
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*
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* This generator can only be used by algorithms where authentication
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* is performed after encryption (i.e., authenc).
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*
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* Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
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*/
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#include <crypto/internal/geniv.h>
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#include <crypto/scatterwalk.h>
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#include <crypto/skcipher.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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static int echainiv_encrypt(struct aead_request *req)
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{
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struct crypto_aead *geniv = crypto_aead_reqtfm(req);
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struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
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struct aead_request *subreq = aead_request_ctx(req);
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__be64 nseqno;
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u64 seqno;
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u8 *info;
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unsigned int ivsize = crypto_aead_ivsize(geniv);
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int err;
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if (req->cryptlen < ivsize)
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return -EINVAL;
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aead_request_set_tfm(subreq, ctx->child);
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info = req->iv;
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if (req->src != req->dst) {
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SYNC_SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);
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skcipher_request_set_sync_tfm(nreq, ctx->sknull);
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skcipher_request_set_callback(nreq, req->base.flags,
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NULL, NULL);
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skcipher_request_set_crypt(nreq, req->src, req->dst,
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req->assoclen + req->cryptlen,
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NULL);
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err = crypto_skcipher_encrypt(nreq);
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if (err)
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return err;
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}
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aead_request_set_callback(subreq, req->base.flags,
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req->base.complete, req->base.data);
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aead_request_set_crypt(subreq, req->dst, req->dst,
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req->cryptlen, info);
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aead_request_set_ad(subreq, req->assoclen);
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memcpy(&nseqno, info + ivsize - 8, 8);
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seqno = be64_to_cpu(nseqno);
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memset(info, 0, ivsize);
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scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
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do {
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u64 a;
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memcpy(&a, ctx->salt + ivsize - 8, 8);
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a |= 1;
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a *= seqno;
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memcpy(info + ivsize - 8, &a, 8);
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} while ((ivsize -= 8));
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return crypto_aead_encrypt(subreq);
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}
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static int echainiv_decrypt(struct aead_request *req)
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{
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struct crypto_aead *geniv = crypto_aead_reqtfm(req);
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struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
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struct aead_request *subreq = aead_request_ctx(req);
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crypto_completion_t compl;
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void *data;
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unsigned int ivsize = crypto_aead_ivsize(geniv);
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if (req->cryptlen < ivsize)
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return -EINVAL;
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aead_request_set_tfm(subreq, ctx->child);
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compl = req->base.complete;
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data = req->base.data;
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aead_request_set_callback(subreq, req->base.flags, compl, data);
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aead_request_set_crypt(subreq, req->src, req->dst,
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req->cryptlen - ivsize, req->iv);
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aead_request_set_ad(subreq, req->assoclen + ivsize);
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scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
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return crypto_aead_decrypt(subreq);
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}
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static int echainiv_aead_create(struct crypto_template *tmpl,
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struct rtattr **tb)
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{
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struct aead_instance *inst;
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int err;
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inst = aead_geniv_alloc(tmpl, tb);
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if (IS_ERR(inst))
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return PTR_ERR(inst);
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err = -EINVAL;
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if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
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goto free_inst;
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inst->alg.encrypt = echainiv_encrypt;
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inst->alg.decrypt = echainiv_decrypt;
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inst->alg.init = aead_init_geniv;
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inst->alg.exit = aead_exit_geniv;
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inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
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inst->alg.base.cra_ctxsize += inst->alg.ivsize;
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err = aead_register_instance(tmpl, inst);
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if (err) {
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free_inst:
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inst->free(inst);
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}
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return err;
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}
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static struct crypto_template echainiv_tmpl = {
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.name = "echainiv",
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.create = echainiv_aead_create,
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.module = THIS_MODULE,
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};
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static int __init echainiv_module_init(void)
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{
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return crypto_register_template(&echainiv_tmpl);
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}
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static void __exit echainiv_module_exit(void)
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{
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crypto_unregister_template(&echainiv_tmpl);
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}
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subsys_initcall(echainiv_module_init);
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module_exit(echainiv_module_exit);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("Encrypted Chain IV Generator");
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MODULE_ALIAS_CRYPTO("echainiv");
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