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
  31 static 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
  90 static 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
 117 static int echainiv_aead_create(struct crypto_template *tmpl,
 118                                 struct rtattr **tb)
 119 {
 120         struct aead_instance *inst;
 121         struct crypto_aead_spawn *spawn;
 122         struct aead_alg *alg;
 123         int err;
 124
 125         inst = aead_geniv_alloc(tmpl, tb, 0, 0);
 126
 127         if (IS_ERR(inst))
 128                 return PTR_ERR(inst);
 129
 130         spawn = aead_instance_ctx(inst);
 131         alg = crypto_spawn_aead_alg(spawn);
 132
 133         err = -EINVAL;
 134         if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
 135                 goto free_inst;
 136
 137         inst->alg.encrypt = echainiv_encrypt;
 138         inst->alg.decrypt = echainiv_decrypt;
 139
 140         inst->alg.init = aead_init_geniv;
 141         inst->alg.exit = aead_exit_geniv;
 142
 143         inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
 144         inst->alg.base.cra_ctxsize += inst->alg.ivsize;
 145
 146         inst->free = aead_geniv_free;
 147
 148         err = aead_register_instance(tmpl, inst);
 149         if (err)
 150                 goto free_inst;
 151
 152 out:
 153         return err;
 154
 155 free_inst:
 156         aead_geniv_free(inst);
 157         goto out;
 158 }
 159
 160 static void echainiv_free(struct crypto_instance *inst)
 161 {
 162         aead_geniv_free(aead_instance(inst));
 163 }
 164
 165 static struct crypto_template echainiv_tmpl = {
 166         .name = "echainiv",
 167         .create = echainiv_aead_create,
 168         .free = echainiv_free,
 169         .module = THIS_MODULE,
 170 };
 171
 172 static int __init echainiv_module_init(void)
 173 {
 174         return crypto_register_template(&echainiv_tmpl);
 175 }
 176
 177 static void __exit echainiv_module_exit(void)
 178 {
 179         crypto_unregister_template(&echainiv_tmpl);
 180 }
 181
 182 module_init(echainiv_module_init);
 183 module_exit(echainiv_module_exit);
 184
 185 MODULE_LICENSE("GPL");
 186 MODULE_DESCRIPTION("Encrypted Chain IV Generator");
 187 MODULE_ALIAS_CRYPTO("echainiv");