Herbert Xu | 7f47073 | 2007-11-27 23:17:23 +0800 | [diff] [blame^] | 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"); |