crypto/chainiv.c

   1 /*
   2  * chainiv: Chain IV Generator
   3  *
   4  * Generate IVs simply be using the last block of the previous encryption.
   5  * This is mainly useful for CBC with a synchronous algorithm.
   6  *
   7  * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
   8  *
   9  * This program is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU General Public License as published by the Free
  11  * Software Foundation; either version 2 of the License, or (at your option)
  12  * any later version.
  13  *
  14  */
  15
  16 #include <crypto/internal/skcipher.h>
  17 #include <linux/err.h>
  18 #include <linux/init.h>
  19 #include <linux/module.h>
  20 #include <linux/random.h>
  21 #include <linux/spinlock.h>
  22 #include <linux/string.h>
  23
  24 struct chainiv_ctx {
  25         spinlock_t lock;
  26         char iv[];
  27 };
  28
  29 static int chainiv_givencrypt(struct skcipher_givcrypt_request *req)
  30 {
  31         struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  32         struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  33         struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req);
  34         unsigned int ivsize;
  35         int err;
  36
  37         ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv));
  38         ablkcipher_request_set_callback(subreq, req->creq.base.flags &
  39                                                 ~CRYPTO_TFM_REQ_MAY_SLEEP,
  40                                         req->creq.base.complete,
  41                                         req->creq.base.data);
  42         ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst,
  43                                      req->creq.nbytes, req->creq.info);
  44
  45         spin_lock_bh(&ctx->lock);
  46
  47         ivsize = crypto_ablkcipher_ivsize(geniv);
  48
  49         memcpy(req->giv, ctx->iv, ivsize);
  50         memcpy(subreq->info, ctx->iv, ivsize);
  51
  52         err = crypto_ablkcipher_encrypt(subreq);
  53         if (err)
  54                 goto unlock;
  55
  56         memcpy(ctx->iv, subreq->info, ivsize);
  57
  58 unlock:
  59         spin_unlock_bh(&ctx->lock);
  60
  61         return err;
  62 }
  63
  64 static int chainiv_givencrypt_first(struct skcipher_givcrypt_request *req)
  65 {
  66         struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req);
  67         struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  68
  69         spin_lock_bh(&ctx->lock);
  70         if (crypto_ablkcipher_crt(geniv)->givencrypt !=
  71             chainiv_givencrypt_first)
  72                 goto unlock;
  73
  74         crypto_ablkcipher_crt(geniv)->givencrypt = chainiv_givencrypt;
  75         get_random_bytes(ctx->iv, crypto_ablkcipher_ivsize(geniv));
  76
  77 unlock:
  78         spin_unlock_bh(&ctx->lock);
  79
  80         return chainiv_givencrypt(req);
  81 }
  82
  83 static int chainiv_init(struct crypto_tfm *tfm)
  84 {
  85         struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm);
  86         struct chainiv_ctx *ctx = crypto_ablkcipher_ctx(geniv);
  87
  88         spin_lock_init(&ctx->lock);
  89
  90         tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request);
  91
  92         return skcipher_geniv_init(tfm);
  93 }
  94
  95 static struct crypto_template chainiv_tmpl;
  96
  97 static struct crypto_instance *chainiv_alloc(struct rtattr **tb)
  98 {
  99         struct crypto_instance *inst;
 100
 101         inst = skcipher_geniv_alloc(&chainiv_tmpl, tb, 0,
 102                                     CRYPTO_ALG_ASYNC);
 103         if (IS_ERR(inst))
 104                 goto out;
 105
 106         inst->alg.cra_ablkcipher.givencrypt = chainiv_givencrypt_first;
 107
 108         inst->alg.cra_init = chainiv_init;
 109         inst->alg.cra_exit = skcipher_geniv_exit;
 110
 111         inst->alg.cra_ctxsize = sizeof(struct chainiv_ctx) +
 112                                 inst->alg.cra_ablkcipher.ivsize;
 113
 114 out:
 115         return inst;
 116 }
 117
 118 static struct crypto_template chainiv_tmpl = {
 119         .name = "chainiv",
 120         .alloc = chainiv_alloc,
 121         .free = skcipher_geniv_free,
 122         .module = THIS_MODULE,
 123 };
 124
 125 static int __init chainiv_module_init(void)
 126 {
 127         return crypto_register_template(&chainiv_tmpl);
 128 }
 129
 130 static void __exit chainiv_module_exit(void)
 131 {
 132         crypto_unregister_template(&chainiv_tmpl);
 133 }
 134
 135 module_init(chainiv_module_init);
 136 module_exit(chainiv_module_exit);
 137
 138 MODULE_LICENSE("GPL");
 139 MODULE_DESCRIPTION("Chain IV Generator");