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Diffstat (limited to 'crypto/echainiv.c')
| -rw-r--r-- | crypto/echainiv.c | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/crypto/echainiv.c b/crypto/echainiv.c new file mode 100644 index 000000000..696866686 --- /dev/null +++ b/crypto/echainiv.c @@ -0,0 +1,165 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * echainiv: Encrypted Chain IV Generator + * + * This generator generates an IV based on a sequence number by multiplying + * it with a salt and then encrypting it with the same key as used to encrypt + * the plain text. This algorithm requires that the block size be equal + * to the IV size. It is mainly useful for CBC. + * + * This generator can only be used by algorithms where authentication + * is performed after encryption (i.e., authenc). + * + * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> + */ + +#include <crypto/internal/geniv.h> +#include <crypto/scatterwalk.h> +#include <crypto/skcipher.h> +#include <linux/err.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/string.h> + +static int echainiv_encrypt(struct aead_request *req) +{ + struct crypto_aead *geniv = crypto_aead_reqtfm(req); + struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); + struct aead_request *subreq = aead_request_ctx(req); + __be64 nseqno; + u64 seqno; + u8 *info; + unsigned int ivsize = crypto_aead_ivsize(geniv); + int err; + + if (req->cryptlen < ivsize) + return -EINVAL; + + aead_request_set_tfm(subreq, ctx->child); + + info = req->iv; + + if (req->src != req->dst) { + SYNC_SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull); + + skcipher_request_set_sync_tfm(nreq, ctx->sknull); + skcipher_request_set_callback(nreq, req->base.flags, + NULL, NULL); + skcipher_request_set_crypt(nreq, req->src, req->dst, + req->assoclen + req->cryptlen, + NULL); + + err = crypto_skcipher_encrypt(nreq); + if (err) + return err; + } + + aead_request_set_callback(subreq, req->base.flags, + req->base.complete, req->base.data); + aead_request_set_crypt(subreq, req->dst, req->dst, + req->cryptlen, info); + aead_request_set_ad(subreq, req->assoclen); + + memcpy(&nseqno, info + ivsize - 8, 8); + seqno = be64_to_cpu(nseqno); + memset(info, 0, ivsize); + + scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); + + do { + u64 a; + + memcpy(&a, ctx->salt + ivsize - 8, 8); + + a |= 1; + a *= seqno; + + memcpy(info + ivsize - 8, &a, 8); + } while ((ivsize -= 8)); + + return crypto_aead_encrypt(subreq); +} + +static int echainiv_decrypt(struct aead_request *req) +{ + struct crypto_aead *geniv = crypto_aead_reqtfm(req); + struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); + struct aead_request *subreq = aead_request_ctx(req); + crypto_completion_t compl; + void *data; + unsigned int ivsize = crypto_aead_ivsize(geniv); + + if (req->cryptlen < ivsize) + return -EINVAL; + + aead_request_set_tfm(subreq, ctx->child); + + compl = req->base.complete; + data = req->base.data; + + aead_request_set_callback(subreq, req->base.flags, compl, data); + aead_request_set_crypt(subreq, req->src, req->dst, + req->cryptlen - ivsize, req->iv); + aead_request_set_ad(subreq, req->assoclen + ivsize); + + scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); + + return crypto_aead_decrypt(subreq); +} + +static int echainiv_aead_create(struct crypto_template *tmpl, + struct rtattr **tb) +{ + struct aead_instance *inst; + int err; + + inst = aead_geniv_alloc(tmpl, tb); + + if (IS_ERR(inst)) + return PTR_ERR(inst); + + err = -EINVAL; + if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize) + goto free_inst; + + inst->alg.encrypt = echainiv_encrypt; + inst->alg.decrypt = echainiv_decrypt; + + inst->alg.init = aead_init_geniv; + inst->alg.exit = aead_exit_geniv; + + inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx); + inst->alg.base.cra_ctxsize += inst->alg.ivsize; + + err = aead_register_instance(tmpl, inst); + if (err) { +free_inst: + inst->free(inst); + } + return err; +} + +static struct crypto_template echainiv_tmpl = { + .name = "echainiv", + .create = echainiv_aead_create, + .module = THIS_MODULE, +}; + +static int __init echainiv_module_init(void) +{ + return crypto_register_template(&echainiv_tmpl); +} + +static void __exit echainiv_module_exit(void) +{ + crypto_unregister_template(&echainiv_tmpl); +} + +subsys_initcall(echainiv_module_init); +module_exit(echainiv_module_exit); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Encrypted Chain IV Generator"); +MODULE_ALIAS_CRYPTO("echainiv"); |