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 <crypto/skcipher.h>
  24 #include <linux/err.h>
  25 #include <linux/init.h>
  26 #include <linux/kernel.h>
  27 #include <linux/mm.h>
  28 #include <linux/module.h>
  29 #include <linux/percpu.h>
  30 #include <linux/spinlock.h>
  31 #include <linux/string.h>
  32
  33 #define MAX_IV_SIZE 16
  34
  35 static DEFINE_PER_CPU(u32 [MAX_IV_SIZE / sizeof(u32)], echainiv_iv);
  36
  37 /* We don't care if we get preempted and read/write IVs from the next CPU. */
  38 static void echainiv_read_iv(u8 *dst, unsigned size)
  39 {
  40         u32 *a = (u32 *)dst;
  41         u32 __percpu *b = echainiv_iv;
  42
  43         for (; size >= 4; size -= 4) {
  44                 *a++ = this_cpu_read(*b);
  45                 b++;
  46         }
  47 }
  48
  49 static void echainiv_write_iv(const u8 *src, unsigned size)
  50 {
  51         const u32 *a = (const u32 *)src;
  52         u32 __percpu *b = echainiv_iv;
  53
  54         for (; size >= 4; size -= 4) {
  55                 this_cpu_write(*b, *a);
  56                 a++;
  57                 b++;
  58         }
  59 }
  60
  61 static void echainiv_encrypt_complete2(struct aead_request *req, int err)
  62 {
  63         struct aead_request *subreq = aead_request_ctx(req);
  64         struct crypto_aead *geniv;
  65         unsigned int ivsize;
  66
  67         if (err == -EINPROGRESS)
  68                 return;
  69
  70         if (err)
  71                 goto out;
  72
  73         geniv = crypto_aead_reqtfm(req);
  74         ivsize = crypto_aead_ivsize(geniv);
  75
  76         echainiv_write_iv(subreq->iv, ivsize);
  77
  78         if (req->iv != subreq->iv)
  79                 memcpy(req->iv, subreq->iv, ivsize);
  80
  81 out:
  82         if (req->iv != subreq->iv)
  83                 kzfree(subreq->iv);
  84 }
  85
  86 static void echainiv_encrypt_complete(struct crypto_async_request *base,
  87                                          int err)
  88 {
  89         struct aead_request *req = base->data;
  90
  91         echainiv_encrypt_complete2(req, err);
  92         aead_request_complete(req, err);
  93 }
  94
  95 static int echainiv_encrypt(struct aead_request *req)
  96 {
  97         struct crypto_aead *geniv = crypto_aead_reqtfm(req);
  98         struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
  99         struct aead_request *subreq = aead_request_ctx(req);
 100         crypto_completion_t compl;
 101         void *data;
 102         u8 *info;
 103         unsigned int ivsize = crypto_aead_ivsize(geniv);
 104         int err;
 105
 106         if (req->cryptlen < ivsize)
 107                 return -EINVAL;
 108
 109         aead_request_set_tfm(subreq, ctx->child);
 110
 111         compl = echainiv_encrypt_complete;
 112         data = req;
 113         info = req->iv;
 114
 115         if (req->src != req->dst) {
 116                 SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);
 117
 118                 skcipher_request_set_tfm(nreq, ctx->sknull);
 119                 skcipher_request_set_callback(nreq, req->base.flags,
 120                                               NULL, NULL);
 121                 skcipher_request_set_crypt(nreq, req->src, req->dst,
 122                                            req->assoclen + req->cryptlen,
 123                                            NULL);
 124
 125                 err = crypto_skcipher_encrypt(nreq);
 126                 if (err)
 127                         return err;
 128         }
 129
 130         if (unlikely(!IS_ALIGNED((unsigned long)info,
 131                                  crypto_aead_alignmask(geniv) + 1))) {
 132                 info = kmalloc(ivsize, req->base.flags &
 133                                        CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL:
 134                                                                   GFP_ATOMIC);
 135                 if (!info)
 136                         return -ENOMEM;
 137
 138                 memcpy(info, req->iv, ivsize);
 139         }
 140
 141         aead_request_set_callback(subreq, req->base.flags, compl, data);
 142         aead_request_set_crypt(subreq, req->dst, req->dst,
 143                                req->cryptlen, info);
 144         aead_request_set_ad(subreq, req->assoclen);
 145
 146         crypto_xor(info, ctx->salt, ivsize);
 147         scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
 148         echainiv_read_iv(info, ivsize);
 149
 150         err = crypto_aead_encrypt(subreq);
 151         echainiv_encrypt_complete2(req, err);
 152         return err;
 153 }
 154
 155 static int echainiv_decrypt(struct aead_request *req)
 156 {
 157         struct crypto_aead *geniv = crypto_aead_reqtfm(req);
 158         struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
 159         struct aead_request *subreq = aead_request_ctx(req);
 160         crypto_completion_t compl;
 161         void *data;
 162         unsigned int ivsize = crypto_aead_ivsize(geniv);
 163
 164         if (req->cryptlen < ivsize)
 165                 return -EINVAL;
 166
 167         aead_request_set_tfm(subreq, ctx->child);
 168
 169         compl = req->base.complete;
 170         data = req->base.data;
 171
 172         aead_request_set_callback(subreq, req->base.flags, compl, data);
 173         aead_request_set_crypt(subreq, req->src, req->dst,
 174                                req->cryptlen - ivsize, req->iv);
 175         aead_request_set_ad(subreq, req->assoclen + ivsize);
 176
 177         scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
 178
 179         return crypto_aead_decrypt(subreq);
 180 }
 181
 182 static int echainiv_aead_create(struct crypto_template *tmpl,
 183                                 struct rtattr **tb)
 184 {
 185         struct aead_instance *inst;
 186         struct crypto_aead_spawn *spawn;
 187         struct aead_alg *alg;
 188         int err;
 189
 190         inst = aead_geniv_alloc(tmpl, tb, 0, 0);
 191
 192         if (IS_ERR(inst))
 193                 return PTR_ERR(inst);
 194
 195         spawn = aead_instance_ctx(inst);
 196         alg = crypto_spawn_aead_alg(spawn);
 197
 198         err = -EINVAL;
 199         if (inst->alg.ivsize & (sizeof(u32) - 1) ||
 200             inst->alg.ivsize > MAX_IV_SIZE)
 201                 goto free_inst;
 202
 203         inst->alg.encrypt = echainiv_encrypt;
 204         inst->alg.decrypt = echainiv_decrypt;
 205
 206         inst->alg.init = aead_init_geniv;
 207         inst->alg.exit = aead_exit_geniv;
 208
 209         inst->alg.base.cra_alignmask |= __alignof__(u32) - 1;
 210         inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
 211         inst->alg.base.cra_ctxsize += inst->alg.ivsize;
 212
 213         inst->free = aead_geniv_free;
 214
 215         err = aead_register_instance(tmpl, inst);
 216         if (err)
 217                 goto free_inst;
 218
 219 out:
 220         return err;
 221
 222 free_inst:
 223         aead_geniv_free(inst);
 224         goto out;
 225 }
 226
 227 static void echainiv_free(struct crypto_instance *inst)
 228 {
 229         aead_geniv_free(aead_instance(inst));
 230 }
 231
 232 static struct crypto_template echainiv_tmpl = {
 233         .name = "echainiv",
 234         .create = echainiv_aead_create,
 235         .free = echainiv_free,
 236         .module = THIS_MODULE,
 237 };
 238
 239 static int __init echainiv_module_init(void)
 240 {
 241         return crypto_register_template(&echainiv_tmpl);
 242 }
 243
 244 static void __exit echainiv_module_exit(void)
 245 {
 246         crypto_unregister_template(&echainiv_tmpl);
 247 }
 248
 249 module_init(echainiv_module_init);
 250 module_exit(echainiv_module_exit);
 251
 252 MODULE_LICENSE("GPL");
 253 MODULE_DESCRIPTION("Encrypted Chain IV Generator");
 254 MODULE_ALIAS_CRYPTO("echainiv");