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![Herbert Xu](/assets/img/avatar_default.png)
The current implementation uses a global per-cpu array to store
data which are used to derive the next IV. This is insecure as
the attacker may change the stored data.
This patch removes all traces of chaining and replaces it with
multiplication of the salt and the sequence number.
Fixes: a10f554fa7
("crypto: echainiv - Add encrypted chain IV...")
Cc: stable@vger.kernel.org
Reported-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
187 lines
4.6 KiB
C
187 lines
4.6 KiB
C
/*
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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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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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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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SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);
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skcipher_request_set_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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struct crypto_aead_spawn *spawn;
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struct aead_alg *alg;
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int err;
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inst = aead_geniv_alloc(tmpl, tb, 0, 0);
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if (IS_ERR(inst))
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return PTR_ERR(inst);
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spawn = aead_instance_ctx(inst);
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alg = crypto_spawn_aead_alg(spawn);
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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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inst->free = aead_geniv_free;
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err = aead_register_instance(tmpl, inst);
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if (err)
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goto free_inst;
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out:
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return err;
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free_inst:
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aead_geniv_free(inst);
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goto out;
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}
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static void echainiv_free(struct crypto_instance *inst)
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{
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aead_geniv_free(aead_instance(inst));
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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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.free = echainiv_free,
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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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module_init(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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