Herbert Xu | 0a27032 | 2007-11-30 21:38:37 +1100 | [diff] [blame] | 1 | /* |
| 2 | * seqiv: Sequence Number IV Generator |
| 3 | * |
| 4 | * This generator generates an IV based on a sequence number by xoring it |
| 5 | * with a salt. This algorithm is mainly useful for CTR and similar modes. |
| 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/kernel.h> |
| 20 | #include <linux/module.h> |
| 21 | #include <linux/random.h> |
| 22 | #include <linux/spinlock.h> |
| 23 | #include <linux/string.h> |
| 24 | |
| 25 | struct seqiv_ctx { |
| 26 | spinlock_t lock; |
| 27 | u8 salt[] __attribute__ ((aligned(__alignof__(u32)))); |
| 28 | }; |
| 29 | |
| 30 | static void seqiv_complete2(struct skcipher_givcrypt_request *req, int err) |
| 31 | { |
| 32 | struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req); |
| 33 | struct crypto_ablkcipher *geniv; |
| 34 | |
| 35 | if (err == -EINPROGRESS) |
| 36 | return; |
| 37 | |
| 38 | if (err) |
| 39 | goto out; |
| 40 | |
| 41 | geniv = skcipher_givcrypt_reqtfm(req); |
| 42 | memcpy(req->creq.info, subreq->info, crypto_ablkcipher_ivsize(geniv)); |
| 43 | |
| 44 | out: |
| 45 | kfree(subreq->info); |
| 46 | } |
| 47 | |
| 48 | static void seqiv_complete(struct crypto_async_request *base, int err) |
| 49 | { |
| 50 | struct skcipher_givcrypt_request *req = base->data; |
| 51 | |
| 52 | seqiv_complete2(req, err); |
| 53 | skcipher_givcrypt_complete(req, err); |
| 54 | } |
| 55 | |
| 56 | static int seqiv_givencrypt(struct skcipher_givcrypt_request *req) |
| 57 | { |
| 58 | struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req); |
| 59 | struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv); |
| 60 | struct ablkcipher_request *subreq = skcipher_givcrypt_reqctx(req); |
| 61 | crypto_completion_t complete; |
| 62 | void *data; |
| 63 | u8 *info; |
| 64 | __be64 seq; |
| 65 | unsigned int ivsize; |
| 66 | unsigned int len; |
| 67 | int err; |
| 68 | |
| 69 | ablkcipher_request_set_tfm(subreq, skcipher_geniv_cipher(geniv)); |
| 70 | |
| 71 | complete = req->creq.base.complete; |
| 72 | data = req->creq.base.data; |
| 73 | info = req->creq.info; |
| 74 | |
| 75 | ivsize = crypto_ablkcipher_ivsize(geniv); |
| 76 | |
| 77 | if (unlikely(!IS_ALIGNED((unsigned long)info, |
| 78 | crypto_ablkcipher_alignmask(geniv) + 1))) { |
| 79 | info = kmalloc(ivsize, req->creq.base.flags & |
| 80 | CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL: |
| 81 | GFP_ATOMIC); |
| 82 | if (!info) |
| 83 | return -ENOMEM; |
| 84 | |
| 85 | complete = seqiv_complete; |
| 86 | data = req; |
| 87 | } |
| 88 | |
| 89 | ablkcipher_request_set_callback(subreq, req->creq.base.flags, complete, |
| 90 | data); |
| 91 | ablkcipher_request_set_crypt(subreq, req->creq.src, req->creq.dst, |
| 92 | req->creq.nbytes, info); |
| 93 | |
| 94 | len = ivsize; |
| 95 | if (ivsize > sizeof(u64)) { |
| 96 | memset(info, 0, ivsize - sizeof(u64)); |
| 97 | len = sizeof(u64); |
| 98 | } |
| 99 | seq = cpu_to_be64(req->seq); |
| 100 | memcpy(info + ivsize - len, &seq, len); |
| 101 | crypto_xor(info, ctx->salt, ivsize); |
| 102 | |
| 103 | memcpy(req->giv, info, ivsize); |
| 104 | |
| 105 | err = crypto_ablkcipher_encrypt(subreq); |
| 106 | if (unlikely(info != req->creq.info)) |
| 107 | seqiv_complete2(req, err); |
| 108 | return err; |
| 109 | } |
| 110 | |
| 111 | static int seqiv_givencrypt_first(struct skcipher_givcrypt_request *req) |
| 112 | { |
| 113 | struct crypto_ablkcipher *geniv = skcipher_givcrypt_reqtfm(req); |
| 114 | struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv); |
| 115 | |
| 116 | spin_lock_bh(&ctx->lock); |
| 117 | if (crypto_ablkcipher_crt(geniv)->givencrypt != seqiv_givencrypt_first) |
| 118 | goto unlock; |
| 119 | |
| 120 | crypto_ablkcipher_crt(geniv)->givencrypt = seqiv_givencrypt; |
| 121 | get_random_bytes(ctx->salt, crypto_ablkcipher_ivsize(geniv)); |
| 122 | |
| 123 | unlock: |
| 124 | spin_unlock_bh(&ctx->lock); |
| 125 | |
| 126 | return seqiv_givencrypt(req); |
| 127 | } |
| 128 | |
| 129 | static int seqiv_init(struct crypto_tfm *tfm) |
| 130 | { |
| 131 | struct crypto_ablkcipher *geniv = __crypto_ablkcipher_cast(tfm); |
| 132 | struct seqiv_ctx *ctx = crypto_ablkcipher_ctx(geniv); |
| 133 | |
| 134 | spin_lock_init(&ctx->lock); |
| 135 | |
| 136 | tfm->crt_ablkcipher.reqsize = sizeof(struct ablkcipher_request); |
| 137 | |
| 138 | return skcipher_geniv_init(tfm); |
| 139 | } |
| 140 | |
| 141 | static struct crypto_template seqiv_tmpl; |
| 142 | |
| 143 | static struct crypto_instance *seqiv_alloc(struct rtattr **tb) |
| 144 | { |
| 145 | struct crypto_instance *inst; |
| 146 | |
| 147 | inst = skcipher_geniv_alloc(&seqiv_tmpl, tb, 0, 0); |
| 148 | if (IS_ERR(inst)) |
| 149 | goto out; |
| 150 | |
| 151 | inst->alg.cra_ablkcipher.givencrypt = seqiv_givencrypt_first; |
| 152 | |
| 153 | inst->alg.cra_init = seqiv_init; |
| 154 | inst->alg.cra_exit = skcipher_geniv_exit; |
| 155 | |
| 156 | inst->alg.cra_alignmask |= __alignof__(u32) - 1; |
| 157 | |
| 158 | inst->alg.cra_ctxsize = sizeof(struct seqiv_ctx); |
| 159 | inst->alg.cra_ctxsize += inst->alg.cra_ablkcipher.ivsize; |
| 160 | |
| 161 | out: |
| 162 | return inst; |
| 163 | } |
| 164 | |
| 165 | static struct crypto_template seqiv_tmpl = { |
| 166 | .name = "seqiv", |
| 167 | .alloc = seqiv_alloc, |
| 168 | .free = skcipher_geniv_free, |
| 169 | .module = THIS_MODULE, |
| 170 | }; |
| 171 | |
| 172 | static int __init seqiv_module_init(void) |
| 173 | { |
| 174 | return crypto_register_template(&seqiv_tmpl); |
| 175 | } |
| 176 | |
| 177 | static void __exit seqiv_module_exit(void) |
| 178 | { |
| 179 | crypto_unregister_template(&seqiv_tmpl); |
| 180 | } |
| 181 | |
| 182 | module_init(seqiv_module_init); |
| 183 | module_exit(seqiv_module_exit); |
| 184 | |
| 185 | MODULE_LICENSE("GPL"); |
| 186 | MODULE_DESCRIPTION("Sequence Number IV Generator"); |