LXR linux/crypto/echainiv.c

   1/*
   2 * echainiv: Encrypted Chain IV Generator
   3 *
   4 * This generator generates an IV based on a sequence number by multiplying
   5 * it 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 * This generator can only be used by algorithms where authentication
  10 * is performed after encryption (i.e., authenc).
  11 *
  12 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
  13 *
  14 * This program is free software; you can redistribute it and/or modify it
  15 * under the terms of the GNU General Public License as published by the Free
  16 * Software Foundation; either version 2 of the License, or (at your option)
  17 * any later version.
  18 *
  19 */
  20
  21#include <crypto/internal/geniv.h>
  22#include <crypto/scatterwalk.h>
  23#include <crypto/skcipher.h>
  24#include <linux/err.h>
  25#include <linux/init.h>
  26#include <linux/kernel.h>
  27#include <linux/module.h>
  28#include <linux/slab.h>
  29#include <linux/string.h>
  30
  31static int echainiv_encrypt(struct aead_request *req)
  32{
  33        struct crypto_aead *geniv = crypto_aead_reqtfm(req);
  34        struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
  35        struct aead_request *subreq = aead_request_ctx(req);
  36        __be64 nseqno;
  37        u64 seqno;
  38        u8 *info;
  39        unsigned int ivsize = crypto_aead_ivsize(geniv);
  40        int err;
  41
  42        if (req->cryptlen < ivsize)
  43                return -EINVAL;
  44
  45        aead_request_set_tfm(subreq, ctx->child);
  46
  47        info = req->iv;
  48
  49        if (req->src != req->dst) {
  50                SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);
  51
  52                skcipher_request_set_tfm(nreq, ctx->sknull);
  53                skcipher_request_set_callback(nreq, req->base.flags,
  54                                              NULL, NULL);
  55                skcipher_request_set_crypt(nreq, req->src, req->dst,
  56                                           req->assoclen + req->cryptlen,
  57                                           NULL);
  58
  59                err = crypto_skcipher_encrypt(nreq);
  60                if (err)
  61                        return err;
  62        }
  63
  64        aead_request_set_callback(subreq, req->base.flags,
  65                                  req->base.complete, req->base.data);
  66        aead_request_set_crypt(subreq, req->dst, req->dst,
  67                               req->cryptlen, info);
  68        aead_request_set_ad(subreq, req->assoclen);
  69
  70        memcpy(&nseqno, info + ivsize - 8, 8);
  71        seqno = be64_to_cpu(nseqno);
  72        memset(info, 0, ivsize);
  73
  74        scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
  75
  76        do {
  77                u64 a;
  78
  79                memcpy(&a, ctx->salt + ivsize - 8, 8);
  80
  81                a |= 1;
  82                a *= seqno;
  83
  84                memcpy(info + ivsize - 8, &a, 8);
  85        } while ((ivsize -= 8));
  86
  87        return crypto_aead_encrypt(subreq);
  88}
  89
  90static int echainiv_decrypt(struct aead_request *req)
  91{
  92        struct crypto_aead *geniv = crypto_aead_reqtfm(req);
  93        struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
  94        struct aead_request *subreq = aead_request_ctx(req);
  95        crypto_completion_t compl;
  96        void *data;
  97        unsigned int ivsize = crypto_aead_ivsize(geniv);
  98
  99        if (req->cryptlen < ivsize)
 100                return -EINVAL;
 101
 102        aead_request_set_tfm(subreq, ctx->child);
 103
 104        compl = req->base.complete;
 105        data = req->base.data;
 106
 107        aead_request_set_callback(subreq, req->base.flags, compl, data);
 108        aead_request_set_crypt(subreq, req->src, req->dst,
 109                               req->cryptlen - ivsize, req->iv);
 110        aead_request_set_ad(subreq, req->assoclen + ivsize);
 111
 112        scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
 113
 114        return crypto_aead_decrypt(subreq);
 115}
 116
 117static int echainiv_aead_create(struct crypto_template *tmpl,
 118                                struct rtattr **tb)
 119{
 120        struct aead_instance *inst;
 121        int err;
 122
 123        inst = aead_geniv_alloc(tmpl, tb, 0, 0);
 124
 125        if (IS_ERR(inst))
 126                return PTR_ERR(inst);
 127
 128        err = -EINVAL;
 129        if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
 130                goto free_inst;
 131
 132        inst->alg.encrypt = echainiv_encrypt;
 133        inst->alg.decrypt = echainiv_decrypt;
 134
 135        inst->alg.init = aead_init_geniv;
 136        inst->alg.exit = aead_exit_geniv;
 137
 138        inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
 139        inst->alg.base.cra_ctxsize += inst->alg.ivsize;
 140
 141        inst->free = aead_geniv_free;
 142
 143        err = aead_register_instance(tmpl, inst);
 144        if (err)
 145                goto free_inst;
 146
 147out:
 148        return err;
 149
 150free_inst:
 151        aead_geniv_free(inst);
 152        goto out;
 153}
 154
 155static void echainiv_free(struct crypto_instance *inst)
 156{
 157        aead_geniv_free(aead_instance(inst));
 158}
 159
 160static struct crypto_template echainiv_tmpl = {
 161        .name = "echainiv",
 162        .create = echainiv_aead_create,
 163        .free = echainiv_free,
 164        .module = THIS_MODULE,
 165};
 166
 167static int __init echainiv_module_init(void)
 168{
 169        return crypto_register_template(&echainiv_tmpl);
 170}
 171
 172static void __exit echainiv_module_exit(void)
 173{
 174        crypto_unregister_template(&echainiv_tmpl);
 175}
 176
 177module_init(echainiv_module_init);
 178module_exit(echainiv_module_exit);
 179
 180MODULE_LICENSE("GPL");
 181MODULE_DESCRIPTION("Encrypted Chain IV Generator");
 182MODULE_ALIAS_CRYPTO("echainiv");
 183