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
26static 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(tfm: 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(tfm: geniv);
35
36 if (req->cryptlen < ivsize)
37 return -EINVAL;
38
39 aead_request_set_tfm(req: subreq, tfm: ctx->child);
40
41 info = req->iv;
42
43 if (req->src != req->dst)
44 memcpy_sglist(dst: req->dst, src: req->src,
45 nbytes: req->assoclen + req->cryptlen);
46
47 aead_request_set_callback(req: subreq, flags: req->base.flags,
48 compl: req->base.complete, data: req->base.data);
49 aead_request_set_crypt(req: subreq, src: req->dst, dst: req->dst,
50 cryptlen: req->cryptlen, iv: info);
51 aead_request_set_ad(req: subreq, assoclen: req->assoclen);
52
53 memcpy(to: &nseqno, from: info + ivsize - 8, len: 8);
54 seqno = be64_to_cpu(nseqno);
55 memset(s: info, c: 0, n: ivsize);
56
57 scatterwalk_map_and_copy(buf: info, sg: req->dst, start: req->assoclen, nbytes: ivsize, out: 1);
58
59 do {
60 u64 a;
61
62 memcpy(to: &a, from: ctx->salt + ivsize - 8, len: 8);
63
64 a |= 1;
65 a *= seqno;
66
67 memcpy(to: info + ivsize - 8, from: &a, len: 8);
68 } while ((ivsize -= 8));
69
70 return crypto_aead_encrypt(req: subreq);
71}
72
73static int echainiv_decrypt(struct aead_request *req)
74{
75 struct crypto_aead *geniv = crypto_aead_reqtfm(req);
76 struct aead_geniv_ctx *ctx = crypto_aead_ctx(tfm: geniv);
77 struct aead_request *subreq = aead_request_ctx(req);
78 crypto_completion_t compl;
79 void *data;
80 unsigned int ivsize = crypto_aead_ivsize(tfm: geniv);
81
82 if (req->cryptlen < ivsize)
83 return -EINVAL;
84
85 aead_request_set_tfm(req: subreq, tfm: ctx->child);
86
87 compl = req->base.complete;
88 data = req->base.data;
89
90 aead_request_set_callback(req: subreq, flags: req->base.flags, compl, data);
91 aead_request_set_crypt(req: subreq, src: req->src, dst: req->dst,
92 cryptlen: req->cryptlen - ivsize, iv: req->iv);
93 aead_request_set_ad(req: subreq, assoclen: req->assoclen + ivsize);
94
95 scatterwalk_map_and_copy(buf: req->iv, sg: req->src, start: req->assoclen, nbytes: ivsize, out: 0);
96
97 return crypto_aead_decrypt(req: subreq);
98}
99
100static int echainiv_aead_create(struct crypto_template *tmpl,
101 struct rtattr **tb)
102{
103 struct aead_instance *inst;
104 int err;
105
106 inst = aead_geniv_alloc(tmpl, tb);
107
108 if (IS_ERR(ptr: inst))
109 return PTR_ERR(ptr: inst);
110
111 err = -EINVAL;
112 if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
113 goto free_inst;
114
115 inst->alg.encrypt = echainiv_encrypt;
116 inst->alg.decrypt = echainiv_decrypt;
117
118 inst->alg.init = aead_init_geniv;
119 inst->alg.exit = aead_exit_geniv;
120
121 inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
122 inst->alg.base.cra_ctxsize += inst->alg.ivsize;
123
124 err = aead_register_instance(tmpl, inst);
125 if (err) {
126free_inst:
127 inst->free(inst);
128 }
129 return err;
130}
131
132static struct crypto_template echainiv_tmpl = {
133 .name = "echainiv",
134 .create = echainiv_aead_create,
135 .module = THIS_MODULE,
136};
137
138static int __init echainiv_module_init(void)
139{
140 return crypto_register_template(tmpl: &echainiv_tmpl);
141}
142
143static void __exit echainiv_module_exit(void)
144{
145 crypto_unregister_template(tmpl: &echainiv_tmpl);
146}
147
148module_init(echainiv_module_init);
149module_exit(echainiv_module_exit);
150
151MODULE_LICENSE("GPL");
152MODULE_DESCRIPTION("Encrypted Chain IV Generator");
153MODULE_ALIAS_CRYPTO("echainiv");
154