1/*
2 * echainiv: Encrypted Chain IV Generator
3 *
4 * This generator generates an IV based on a sequence number by multiplying
5 * it 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/module.h>
28#include <linux/slab.h>
29#include <linux/string.h>
30
31static int echainiv_encrypt(struct aead_request *req)
32{
33 struct crypto_aead *geniv = crypto_aead_reqtfm(req);
34 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
35 struct aead_request *subreq = aead_request_ctx(req);
36 __be64 nseqno;
37 u64 seqno;
38 u8 *info;
39 unsigned int ivsize = crypto_aead_ivsize(geniv);
40 int err;
41
42 if (req->cryptlen < ivsize)
43 return -EINVAL;
44
45 aead_request_set_tfm(subreq, ctx->child);
46
47 info = req->iv;
48
49 if (req->src != req->dst) {
50 SYNC_SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);
51
52 skcipher_request_set_sync_tfm(nreq, ctx->sknull);
53 skcipher_request_set_callback(nreq, req->base.flags,
54 NULL, NULL);
55 skcipher_request_set_crypt(nreq, req->src, req->dst,
56 req->assoclen + req->cryptlen,
57 NULL);
58
59 err = crypto_skcipher_encrypt(nreq);
60 if (err)
61 return err;
62 }
63
64 aead_request_set_callback(subreq, req->base.flags,
65 req->base.complete, req->base.data);
66 aead_request_set_crypt(subreq, req->dst, req->dst,
67 req->cryptlen, info);
68 aead_request_set_ad(subreq, req->assoclen);
69
70 memcpy(&nseqno, info + ivsize - 8, 8);
71 seqno = be64_to_cpu(nseqno);
72 memset(info, 0, ivsize);
73
74 scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
75
76 do {
77 u64 a;
78
79 memcpy(&a, ctx->salt + ivsize - 8, 8);
80
81 a |= 1;
82 a *= seqno;
83
84 memcpy(info + ivsize - 8, &a, 8);
85 } while ((ivsize -= 8));
86
87 return crypto_aead_encrypt(subreq);
88}
89
90static int echainiv_decrypt(struct aead_request *req)
91{
92 struct crypto_aead *geniv = crypto_aead_reqtfm(req);
93 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
94 struct aead_request *subreq = aead_request_ctx(req);
95 crypto_completion_t compl;
96 void *data;
97 unsigned int ivsize = crypto_aead_ivsize(geniv);
98
99 if (req->cryptlen < ivsize)
100 return -EINVAL;
101
102 aead_request_set_tfm(subreq, ctx->child);
103
104 compl = req->base.complete;
105 data = req->base.data;
106
107 aead_request_set_callback(subreq, req->base.flags, compl, data);
108 aead_request_set_crypt(subreq, req->src, req->dst,
109 req->cryptlen - ivsize, req->iv);
110 aead_request_set_ad(subreq, req->assoclen + ivsize);
111
112 scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
113
114 return crypto_aead_decrypt(subreq);
115}
116
117static int echainiv_aead_create(struct crypto_template *tmpl,
118 struct rtattr **tb)
119{
120 struct aead_instance *inst;
121 int err;
122
123 inst = aead_geniv_alloc(tmpl, tb, 0, 0);
124
125 if (IS_ERR(inst))
126 return PTR_ERR(inst);
127
128 err = -EINVAL;
129 if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
130 goto free_inst;
131
132 inst->alg.encrypt = echainiv_encrypt;
133 inst->alg.decrypt = echainiv_decrypt;
134
135 inst->alg.init = aead_init_geniv;
136 inst->alg.exit = aead_exit_geniv;
137
138 inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
139 inst->alg.base.cra_ctxsize += inst->alg.ivsize;
140
141 inst->free = aead_geniv_free;
142
143 err = aead_register_instance(tmpl, inst);
144 if (err)
145 goto free_inst;
146
147out:
148 return err;
149
150free_inst:
151 aead_geniv_free(inst);
152 goto out;
153}
154
155static void echainiv_free(struct crypto_instance *inst)
156{
157 aead_geniv_free(aead_instance(inst));
158}
159
160static struct crypto_template echainiv_tmpl = {
161 .name = "echainiv",
162 .create = echainiv_aead_create,
163 .free = echainiv_free,
164 .module = THIS_MODULE,
165};
166
167static int __init echainiv_module_init(void)
168{
169 return crypto_register_template(&echainiv_tmpl);
170}
171
172static void __exit echainiv_module_exit(void)
173{
174 crypto_unregister_template(&echainiv_tmpl);
175}
176
177module_init(echainiv_module_init);
178module_exit(echainiv_module_exit);
179
180MODULE_LICENSE("GPL");
181MODULE_DESCRIPTION("Encrypted Chain IV Generator");
182MODULE_ALIAS_CRYPTO("echainiv");
183