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(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 | int err; |
36 | |
37 | if (req->cryptlen < ivsize) |
38 | return -EINVAL; |
39 | |
40 | aead_request_set_tfm(req: subreq, tfm: 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(req: nreq, tfm: ctx->sknull); |
48 | skcipher_request_set_callback(req: nreq, flags: req->base.flags, |
49 | NULL, NULL); |
50 | skcipher_request_set_crypt(req: nreq, src: req->src, dst: req->dst, |
51 | cryptlen: req->assoclen + req->cryptlen, |
52 | NULL); |
53 | |
54 | err = crypto_skcipher_encrypt(req: nreq); |
55 | if (err) |
56 | return err; |
57 | } |
58 | |
59 | aead_request_set_callback(req: subreq, flags: req->base.flags, |
60 | compl: req->base.complete, data: req->base.data); |
61 | aead_request_set_crypt(req: subreq, src: req->dst, dst: req->dst, |
62 | cryptlen: req->cryptlen, iv: info); |
63 | aead_request_set_ad(req: subreq, assoclen: 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(buf: info, sg: req->dst, start: req->assoclen, nbytes: ivsize, out: 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(req: 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(tfm: 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(tfm: geniv); |
93 | |
94 | if (req->cryptlen < ivsize) |
95 | return -EINVAL; |
96 | |
97 | aead_request_set_tfm(req: subreq, tfm: ctx->child); |
98 | |
99 | compl = req->base.complete; |
100 | data = req->base.data; |
101 | |
102 | aead_request_set_callback(req: subreq, flags: req->base.flags, compl, data); |
103 | aead_request_set_crypt(req: subreq, src: req->src, dst: req->dst, |
104 | cryptlen: req->cryptlen - ivsize, iv: req->iv); |
105 | aead_request_set_ad(req: subreq, assoclen: req->assoclen + ivsize); |
106 | |
107 | scatterwalk_map_and_copy(buf: req->iv, sg: req->src, start: req->assoclen, nbytes: ivsize, out: 0); |
108 | |
109 | return crypto_aead_decrypt(req: 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); |
119 | |
120 | if (IS_ERR(ptr: inst)) |
121 | return PTR_ERR(ptr: 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(tmpl: &echainiv_tmpl); |
153 | } |
154 | |
155 | static void __exit echainiv_module_exit(void) |
156 | { |
157 | crypto_unregister_template(tmpl: &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" ); |
166 | |