crypto/echainiv.c

   1 /*
   2  * echainiv: Encrypted Chain IV Generator
   3  *
   4  * This generator generates an IV based on a sequence number by xoring it
   5  * 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/mm.h>
  27 #include <linux/module.h>
  28 #include <linux/percpu.h>
  29 #include <linux/spinlock.h>
  30 #include <linux/string.h>
  31
  32 #define MAX_IV_SIZE 16
  33
  34 static DEFINE_PER_CPU(u32 [MAX_IV_SIZE / sizeof(u32)], echainiv_iv);
  35
  36 /* We don't care if we get preempted and read/write IVs from the next CPU. */
  37 static void echainiv_read_iv(u8 *dst, unsigned size)
  38 {
  39         u32 *a = (u32 *)dst;
  40         u32 __percpu *b = echainiv_iv;
  41
  42         for (; size >= 4; size -= 4) {
  43                 *a++ = this_cpu_read(*b);
  44                 b++;
  45         }
  46 }
  47
  48 static void echainiv_write_iv(const u8 *src, unsigned size)
  49 {
  50         const u32 *a = (const u32 *)src;
  51         u32 __percpu *b = echainiv_iv;
  52
  53         for (; size >= 4; size -= 4) {
  54                 this_cpu_write(*b, *a);
  55                 a++;
  56                 b++;
  57         }
  58 }
  59
  60 static void echainiv_encrypt_complete2(struct aead_request *req, int err)
  61 {
  62         struct aead_request *subreq = aead_request_ctx(req);
  63         struct crypto_aead *geniv;
  64         unsigned int ivsize;
  65
  66         if (err == -EINPROGRESS)
  67                 return;
  68
  69         if (err)
  70                 goto out;
  71
  72         geniv = crypto_aead_reqtfm(req);
  73         ivsize = crypto_aead_ivsize(geniv);
  74
  75         echainiv_write_iv(subreq->iv, ivsize);
  76
  77         if (req->iv != subreq->iv)
  78                 memcpy(req->iv, subreq->iv, ivsize);
  79
  80 out:
  81         if (req->iv != subreq->iv)
  82                 kzfree(subreq->iv);
  83 }
  84
  85 static void echainiv_encrypt_complete(struct crypto_async_request *base,
  86                                          int err)
  87 {
  88         struct aead_request *req = base->data;
  89
  90         echainiv_encrypt_complete2(req, err);
  91         aead_request_complete(req, err);
  92 }
  93
  94 static int echainiv_encrypt(struct aead_request *req)
  95 {
  96         struct crypto_aead *geniv = crypto_aead_reqtfm(req);
  97         struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
  98         struct aead_request *subreq = aead_request_ctx(req);
  99         crypto_completion_t compl;
 100         void *data;
 101         u8 *info;
 102         unsigned int ivsize = crypto_aead_ivsize(geniv);
 103         int err;
 104
 105         if (req->cryptlen < ivsize)
 106                 return -EINVAL;
 107
 108         aead_request_set_tfm(subreq, ctx->child);
 109
 110         compl = echainiv_encrypt_complete;
 111         data = req;
 112         info = req->iv;
 113
 114         if (req->src != req->dst) {
 115                 struct blkcipher_desc desc = {
 116                         .tfm = ctx->null,
 117                 };
 118
 119                 err = crypto_blkcipher_encrypt(
 120                         &desc, req->dst, req->src,
 121                         req->assoclen + req->cryptlen);
 122                 if (err)
 123                         return err;
 124         }
 125
 126         if (unlikely(!IS_ALIGNED((unsigned long)info,
 127                                  crypto_aead_alignmask(geniv) + 1))) {
 128                 info = kmalloc(ivsize, req->base.flags &
 129                                        CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL:
 130                                                                   GFP_ATOMIC);
 131                 if (!info)
 132                         return -ENOMEM;
 133
 134                 memcpy(info, req->iv, ivsize);
 135         }
 136
 137         aead_request_set_callback(subreq, req->base.flags, compl, data);
 138         aead_request_set_crypt(subreq, req->dst, req->dst,
 139                                req->cryptlen, info);
 140         aead_request_set_ad(subreq, req->assoclen);
 141
 142         crypto_xor(info, ctx->salt, ivsize);
 143         scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
 144         echainiv_read_iv(info, ivsize);
 145
 146         err = crypto_aead_encrypt(subreq);
 147         echainiv_encrypt_complete2(req, err);
 148         return err;
 149 }
 150
 151 static int echainiv_decrypt(struct aead_request *req)
 152 {
 153         struct crypto_aead *geniv = crypto_aead_reqtfm(req);
 154         struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
 155         struct aead_request *subreq = aead_request_ctx(req);
 156         crypto_completion_t compl;
 157         void *data;
 158         unsigned int ivsize = crypto_aead_ivsize(geniv);
 159
 160         if (req->cryptlen < ivsize)
 161                 return -EINVAL;
 162
 163         aead_request_set_tfm(subreq, ctx->child);
 164
 165         compl = req->base.complete;
 166         data = req->base.data;
 167
 168         aead_request_set_callback(subreq, req->base.flags, compl, data);
 169         aead_request_set_crypt(subreq, req->src, req->dst,
 170                                req->cryptlen - ivsize, req->iv);
 171         aead_request_set_ad(subreq, req->assoclen + ivsize);
 172
 173         scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
 174
 175         return crypto_aead_decrypt(subreq);
 176 }
 177
 178 static int echainiv_aead_create(struct crypto_template *tmpl,
 179                                 struct rtattr **tb)
 180 {
 181         struct aead_instance *inst;
 182         struct crypto_aead_spawn *spawn;
 183         struct aead_alg *alg;
 184         int err;
 185
 186         inst = aead_geniv_alloc(tmpl, tb, 0, 0);
 187
 188         if (IS_ERR(inst))
 189                 return PTR_ERR(inst);
 190
 191         spawn = aead_instance_ctx(inst);
 192         alg = crypto_spawn_aead_alg(spawn);
 193
 194         err = -EINVAL;
 195         if (inst->alg.ivsize & (sizeof(u32) - 1) ||
 196             inst->alg.ivsize > MAX_IV_SIZE)
 197                 goto free_inst;
 198
 199         inst->alg.encrypt = echainiv_encrypt;
 200         inst->alg.decrypt = echainiv_decrypt;
 201
 202         inst->alg.init = aead_init_geniv;
 203         inst->alg.exit = aead_exit_geniv;
 204
 205         inst->alg.base.cra_alignmask |= __alignof__(u32) - 1;
 206         inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
 207         inst->alg.base.cra_ctxsize += inst->alg.ivsize;
 208
 209         inst->free = aead_geniv_free;
 210
 211         err = aead_register_instance(tmpl, inst);
 212         if (err)
 213                 goto free_inst;
 214
 215 out:
 216         return err;
 217
 218 free_inst:
 219         aead_geniv_free(inst);
 220         goto out;
 221 }
 222
 223 static void echainiv_free(struct crypto_instance *inst)
 224 {
 225         aead_geniv_free(aead_instance(inst));
 226 }
 227
 228 static struct crypto_template echainiv_tmpl = {
 229         .name = "echainiv",
 230         .create = echainiv_aead_create,
 231         .free = echainiv_free,
 232         .module = THIS_MODULE,
 233 };
 234
 235 static int __init echainiv_module_init(void)
 236 {
 237         return crypto_register_template(&echainiv_tmpl);
 238 }
 239
 240 static void __exit echainiv_module_exit(void)
 241 {
 242         crypto_unregister_template(&echainiv_tmpl);
 243 }
 244
 245 module_init(echainiv_module_init);
 246 module_exit(echainiv_module_exit);
 247
 248 MODULE_LICENSE("GPL");
 249 MODULE_DESCRIPTION("Encrypted Chain IV Generator");
 250 MODULE_ALIAS_CRYPTO("echainiv");