summaryrefslogtreecommitdiff
path: root/crypto/echainiv.c
blob: 45819e6015bf408c927f940024f22661bdbc7e06 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
/*
 * echainiv: Encrypted Chain IV Generator
 *
 * This generator generates an IV based on a sequence number by multiplying
 * it with a salt and then encrypting it with the same key as used to encrypt
 * the plain text.  This algorithm requires that the block size be equal
 * to the IV size.  It is mainly useful for CBC.
 *
 * This generator can only be used by algorithms where authentication
 * is performed after encryption (i.e., authenc).
 *
 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 */

#include <crypto/internal/geniv.h>
#include <crypto/scatterwalk.h>
#include <crypto/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>

static int echainiv_encrypt(struct aead_request *req)
{
	struct crypto_aead *geniv = crypto_aead_reqtfm(req);
	struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
	struct aead_request *subreq = aead_request_ctx(req);
	__be64 nseqno;
	u64 seqno;
	u8 *info;
	unsigned int ivsize = crypto_aead_ivsize(geniv);
	int err;

	if (req->cryptlen < ivsize)
		return -EINVAL;

	aead_request_set_tfm(subreq, ctx->child);

	info = req->iv;

	if (req->src != req->dst) {
		SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull);

		skcipher_request_set_tfm(nreq, ctx->sknull);
		skcipher_request_set_callback(nreq, req->base.flags,
					      NULL, NULL);
		skcipher_request_set_crypt(nreq, req->src, req->dst,
					   req->assoclen + req->cryptlen,
					   NULL);

		err = crypto_skcipher_encrypt(nreq);
		if (err)
			return err;
	}

	aead_request_set_callback(subreq, req->base.flags,
				  req->base.complete, req->base.data);
	aead_request_set_crypt(subreq, req->dst, req->dst,
			       req->cryptlen, info);
	aead_request_set_ad(subreq, req->assoclen);

	memcpy(&nseqno, info + ivsize - 8, 8);
	seqno = be64_to_cpu(nseqno);
	memset(info, 0, ivsize);

	scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);

	do {
		u64 a;

		memcpy(&a, ctx->salt + ivsize - 8, 8);

		a |= 1;
		a *= seqno;

		memcpy(info + ivsize - 8, &a, 8);
	} while ((ivsize -= 8));

	return crypto_aead_encrypt(subreq);
}

static int echainiv_decrypt(struct aead_request *req)
{
	struct crypto_aead *geniv = crypto_aead_reqtfm(req);
	struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
	struct aead_request *subreq = aead_request_ctx(req);
	crypto_completion_t compl;
	void *data;
	unsigned int ivsize = crypto_aead_ivsize(geniv);

	if (req->cryptlen < ivsize)
		return -EINVAL;

	aead_request_set_tfm(subreq, ctx->child);

	compl = req->base.complete;
	data = req->base.data;

	aead_request_set_callback(subreq, req->base.flags, compl, data);
	aead_request_set_crypt(subreq, req->src, req->dst,
			       req->cryptlen - ivsize, req->iv);
	aead_request_set_ad(subreq, req->assoclen + ivsize);

	scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);

	return crypto_aead_decrypt(subreq);
}

static int echainiv_aead_create(struct crypto_template *tmpl,
				struct rtattr **tb)
{
	struct aead_instance *inst;
	int err;

	inst = aead_geniv_alloc(tmpl, tb, 0, 0);

	if (IS_ERR(inst))
		return PTR_ERR(inst);

	err = -EINVAL;
	if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
		goto free_inst;

	inst->alg.encrypt = echainiv_encrypt;
	inst->alg.decrypt = echainiv_decrypt;

	inst->alg.init = aead_init_geniv;
	inst->alg.exit = aead_exit_geniv;

	inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
	inst->alg.base.cra_ctxsize += inst->alg.ivsize;

	inst->free = aead_geniv_free;

	err = aead_register_instance(tmpl, inst);
	if (err)
		goto free_inst;

out:
	return err;

free_inst:
	aead_geniv_free(inst);
	goto out;
}

static void echainiv_free(struct crypto_instance *inst)
{
	aead_geniv_free(aead_instance(inst));
}

static struct crypto_template echainiv_tmpl = {
	.name = "echainiv",
	.create = echainiv_aead_create,
	.free = echainiv_free,
	.module = THIS_MODULE,
};

static int __init echainiv_module_init(void)
{
	return crypto_register_template(&echainiv_tmpl);
}

static void __exit echainiv_module_exit(void)
{
	crypto_unregister_template(&echainiv_tmpl);
}

module_init(echainiv_module_init);
module_exit(echainiv_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Encrypted Chain IV Generator");
MODULE_ALIAS_CRYPTO("echainiv");