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 <linux/err.h>
  24 #include <linux/init.h>
  25 #include <linux/kernel.h>
  26 #include <linux/module.h>
  27 #include <linux/slab.h>
  28 #include <linux/string.h>
  29
  30 static int echainiv_encrypt(struct aead_request *req)
  31 {
  32         struct crypto_aead *geniv = crypto_aead_reqtfm(req);
  33         struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
  34         struct aead_request *subreq = aead_request_ctx(req);
  35         __be64 nseqno;
  36         u64 seqno;
  37         u8 *info;
  38         unsigned int ivsize = crypto_aead_ivsize(geniv);
  39         int err;
  40
  41         if (req->cryptlen < ivsize)
  42                 return -EINVAL;
  43
  44         aead_request_set_tfm(subreq, ctx->child);
  45
  46         info = req->iv;
  47
  48         if (req->src != req->dst) {
  49                 struct blkcipher_desc desc = {
  50                         .tfm = ctx->null,
  51                 };
  52
  53                 err = crypto_blkcipher_encrypt(
  54                         &desc, req->dst, req->src,
  55                         req->assoclen + req->cryptlen);
  56                 if (err)
  57                         return err;
  58         }
  59
  60         aead_request_set_callback(subreq, req->base.flags,
  61                                   req->base.complete, req->base.data);
  62         aead_request_set_crypt(subreq, req->dst, req->dst,
  63                                req->cryptlen, info);
  64         aead_request_set_ad(subreq, req->assoclen);
  65
  66         memcpy(&nseqno, info + ivsize - 8, 8);
  67         seqno = be64_to_cpu(nseqno);
  68         memset(info, 0, ivsize);
  69
  70         scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
  71
  72         do {
  73                 u64 a;
  74
  75                 memcpy(&a, ctx->salt + ivsize - 8, 8);
  76
  77                 a |= 1;
  78                 a *= seqno;
  79
  80                 memcpy(info + ivsize - 8, &a, 8);
  81         } while ((ivsize -= 8));
  82
  83         return crypto_aead_encrypt(subreq);
  84 }
  85
  86 static int echainiv_decrypt(struct aead_request *req)
  87 {
  88         struct crypto_aead *geniv = crypto_aead_reqtfm(req);
  89         struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
  90         struct aead_request *subreq = aead_request_ctx(req);
  91         crypto_completion_t compl;
  92         void *data;
  93         unsigned int ivsize = crypto_aead_ivsize(geniv);
  94
  95         if (req->cryptlen < ivsize)
  96                 return -EINVAL;
  97
  98         aead_request_set_tfm(subreq, ctx->child);
  99
 100         compl = req->base.complete;
 101         data = req->base.data;
 102
 103         aead_request_set_callback(subreq, req->base.flags, compl, data);
 104         aead_request_set_crypt(subreq, req->src, req->dst,
 105                                req->cryptlen - ivsize, req->iv);
 106         aead_request_set_ad(subreq, req->assoclen + ivsize);
 107
 108         scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
 109
 110         return crypto_aead_decrypt(subreq);
 111 }
 112
 113 static int echainiv_aead_create(struct crypto_template *tmpl,
 114                                 struct rtattr **tb)
 115 {
 116         struct aead_instance *inst;
 117         struct crypto_aead_spawn *spawn;
 118         struct aead_alg *alg;
 119         int err;
 120
 121         inst = aead_geniv_alloc(tmpl, tb, 0, 0);
 122
 123         if (IS_ERR(inst))
 124                 return PTR_ERR(inst);
 125
 126         spawn = aead_instance_ctx(inst);
 127         alg = crypto_spawn_aead_alg(spawn);
 128
 129         err = -EINVAL;
 130         if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
 131                 goto free_inst;
 132
 133         inst->alg.encrypt = echainiv_encrypt;
 134         inst->alg.decrypt = echainiv_decrypt;
 135
 136         inst->alg.init = aead_init_geniv;
 137         inst->alg.exit = aead_exit_geniv;
 138
 139         inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
 140         inst->alg.base.cra_ctxsize += inst->alg.ivsize;
 141
 142         inst->free = aead_geniv_free;
 143
 144         err = aead_register_instance(tmpl, inst);
 145         if (err)
 146                 goto free_inst;
 147
 148 out:
 149         return err;
 150
 151 free_inst:
 152         aead_geniv_free(inst);
 153         goto out;
 154 }
 155
 156 static void echainiv_free(struct crypto_instance *inst)
 157 {
 158         aead_geniv_free(aead_instance(inst));
 159 }
 160
 161 static struct crypto_template echainiv_tmpl = {
 162         .name = "echainiv",
 163         .create = echainiv_aead_create,
 164         .free = echainiv_free,
 165         .module = THIS_MODULE,
 166 };
 167
 168 static int __init echainiv_module_init(void)
 169 {
 170         return crypto_register_template(&echainiv_tmpl);
 171 }
 172
 173 static void __exit echainiv_module_exit(void)
 174 {
 175         crypto_unregister_template(&echainiv_tmpl);
 176 }
 177
 178 module_init(echainiv_module_init);
 179 module_exit(echainiv_module_exit);
 180
 181 MODULE_LICENSE("GPL");
 182 MODULE_DESCRIPTION("Encrypted Chain IV Generator");
 183 MODULE_ALIAS_CRYPTO("echainiv");