crypto/echainiv.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * echainiv: Encrypted Chain IV Generator
   4  *
   5  * This generator generates an IV based on a sequence number by multiplying
   6  * it with a salt and then encrypting it with the same key as used to encrypt
   7  * the plain text.  This algorithm requires that the block size be equal
   8  * to the IV size.  It is mainly useful for CBC.
   9  *
  10  * This generator can only be used by algorithms where authentication
  11  * is performed after encryption (i.e., authenc).
  12  *
  13  * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
  14  */
  15
  16 #include <crypto/internal/geniv.h>
  17 #include <crypto/scatterwalk.h>
  18 #include <crypto/skcipher.h>
  19 #include <linux/err.h>
  20 #include <linux/init.h>
  21 #include <linux/kernel.h>
  22 #include <linux/module.h>
  23 #include <linux/slab.h>
  24 #include <linux/string.h>
  25
  26 static int echainiv_encrypt(struct aead_request *req)
  27 {
  28         struct crypto_aead *geniv = crypto_aead_reqtfm(req);
  29         struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
  30         struct aead_request *subreq = aead_request_ctx(req);
  31         __be64 nseqno;
  32         u64 seqno;
  33         u8 *info;
  34         unsigned int ivsize = crypto_aead_ivsize(geniv);
  35         int err;
  36
  37         if (req->cryptlen < ivsize)
  38                 return -EINVAL;
  39
  40         aead_request_set_tfm(subreq, ctx->child);
  41
  42         info = req->iv;
  43
  44         if (req->src != req->dst) {
  45                 SYNC_SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);
  46
  47                 skcipher_request_set_sync_tfm(nreq, ctx->sknull);
  48                 skcipher_request_set_callback(nreq, req->base.flags,
  49                                               NULL, NULL);
  50                 skcipher_request_set_crypt(nreq, req->src, req->dst,
  51                                            req->assoclen + req->cryptlen,
  52                                            NULL);
  53
  54                 err = crypto_skcipher_encrypt(nreq);
  55                 if (err)
  56                         return err;
  57         }
  58
  59         aead_request_set_callback(subreq, req->base.flags,
  60                                   req->base.complete, req->base.data);
  61         aead_request_set_crypt(subreq, req->dst, req->dst,
  62                                req->cryptlen, info);
  63         aead_request_set_ad(subreq, req->assoclen);
  64
  65         memcpy(&nseqno, info + ivsize - 8, 8);
  66         seqno = be64_to_cpu(nseqno);
  67         memset(info, 0, ivsize);
  68
  69         scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
  70
  71         do {
  72                 u64 a;
  73
  74                 memcpy(&a, ctx->salt + ivsize - 8, 8);
  75
  76                 a |= 1;
  77                 a *= seqno;
  78
  79                 memcpy(info + ivsize - 8, &a, 8);
  80         } while ((ivsize -= 8));
  81
  82         return crypto_aead_encrypt(subreq);
  83 }
  84
  85 static int echainiv_decrypt(struct aead_request *req)
  86 {
  87         struct crypto_aead *geniv = crypto_aead_reqtfm(req);
  88         struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
  89         struct aead_request *subreq = aead_request_ctx(req);
  90         crypto_completion_t compl;
  91         void *data;
  92         unsigned int ivsize = crypto_aead_ivsize(geniv);
  93
  94         if (req->cryptlen < ivsize)
  95                 return -EINVAL;
  96
  97         aead_request_set_tfm(subreq, ctx->child);
  98
  99         compl = req->base.complete;
 100         data = req->base.data;
 101
 102         aead_request_set_callback(subreq, req->base.flags, compl, data);
 103         aead_request_set_crypt(subreq, req->src, req->dst,
 104                                req->cryptlen - ivsize, req->iv);
 105         aead_request_set_ad(subreq, req->assoclen + ivsize);
 106
 107         scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
 108
 109         return crypto_aead_decrypt(subreq);
 110 }
 111
 112 static int echainiv_aead_create(struct crypto_template *tmpl,
 113                                 struct rtattr **tb)
 114 {
 115         struct aead_instance *inst;
 116         int err;
 117
 118         inst = aead_geniv_alloc(tmpl, tb, 0, 0);
 119
 120         if (IS_ERR(inst))
 121                 return PTR_ERR(inst);
 122
 123         err = -EINVAL;
 124         if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
 125                 goto free_inst;
 126
 127         inst->alg.encrypt = echainiv_encrypt;
 128         inst->alg.decrypt = echainiv_decrypt;
 129
 130         inst->alg.init = aead_init_geniv;
 131         inst->alg.exit = aead_exit_geniv;
 132
 133         inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
 134         inst->alg.base.cra_ctxsize += inst->alg.ivsize;
 135
 136         err = aead_register_instance(tmpl, inst);
 137         if (err) {
 138 free_inst:
 139                 inst->free(inst);
 140         }
 141         return err;
 142 }
 143
 144 static struct crypto_template echainiv_tmpl = {
 145         .name = "echainiv",
 146         .create = echainiv_aead_create,
 147         .module = THIS_MODULE,
 148 };
 149
 150 static int __init echainiv_module_init(void)
 151 {
 152         return crypto_register_template(&echainiv_tmpl);
 153 }
 154
 155 static void __exit echainiv_module_exit(void)
 156 {
 157         crypto_unregister_template(&echainiv_tmpl);
 158 }
 159
 160 subsys_initcall(echainiv_module_init);
 161 module_exit(echainiv_module_exit);
 162
 163 MODULE_LICENSE("GPL");
 164 MODULE_DESCRIPTION("Encrypted Chain IV Generator");
 165 MODULE_ALIAS_CRYPTO("echainiv");