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25b66522 | 1 | /* |
2 | * Copyright (c) 2003 Markus Friedl. All rights reserved. | |
3 | * | |
4 | * Redistribution and use in source and binary forms, with or without | |
5 | * modification, are permitted provided that the following conditions | |
6 | * are met: | |
7 | * 1. Redistributions of source code must retain the above copyright | |
8 | * notice, this list of conditions and the following disclaimer. | |
9 | * 2. Redistributions in binary form must reproduce the above copyright | |
10 | * notice, this list of conditions and the following disclaimer in the | |
11 | * documentation and/or other materials provided with the distribution. | |
12 | * | |
13 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
14 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
15 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
16 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
17 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
18 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
19 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
20 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
21 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
22 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
23 | */ | |
24 | #include "includes.h" | |
25 | RCSID("$OpenBSD: cipher-ctr.c,v 1.1 2003/05/17 04:27:52 markus Exp $"); | |
26 | ||
27 | #include <openssl/evp.h> | |
28 | ||
29 | #include "log.h" | |
30 | #include "xmalloc.h" | |
31 | ||
32 | #if OPENSSL_VERSION_NUMBER < 0x00907000L | |
33 | #include "rijndael.h" | |
34 | #define AES_KEY rijndael_ctx | |
35 | #define AES_BLOCK_SIZE 16 | |
36 | #define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b) | |
37 | #define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1) | |
38 | #else | |
39 | #include <openssl/aes.h> | |
40 | #endif | |
41 | ||
42 | const EVP_CIPHER *evp_aes_128_ctr(void); | |
43 | void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); | |
44 | ||
45 | struct ssh_aes_ctr_ctx | |
46 | { | |
47 | AES_KEY aes_ctx; | |
48 | u_char aes_counter[AES_BLOCK_SIZE]; | |
49 | }; | |
50 | ||
51 | /* | |
52 | * increment counter 'ctr', | |
53 | * the counter is of size 'len' bytes and stored in network-byte-order. | |
54 | * (LSB at ctr[len-1], MSB at ctr[0]) | |
55 | */ | |
56 | static void | |
57 | ssh_ctr_inc(u_char *ctr, u_int len) | |
58 | { | |
59 | int i; | |
60 | ||
61 | for (i = len - 1; i >= 0; i--) | |
62 | if (++ctr[i]) /* continue on overflow */ | |
63 | return; | |
64 | } | |
65 | ||
66 | static int | |
67 | ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src, | |
68 | u_int len) | |
69 | { | |
70 | struct ssh_aes_ctr_ctx *c; | |
71 | u_int n = 0; | |
72 | u_char buf[AES_BLOCK_SIZE]; | |
73 | ||
74 | if (len == 0) | |
75 | return (1); | |
76 | if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) | |
77 | return (0); | |
78 | ||
79 | while ((len--) > 0) { | |
80 | if (n == 0) { | |
81 | AES_encrypt(c->aes_counter, buf, &c->aes_ctx); | |
82 | ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE); | |
83 | } | |
84 | *(dest++) = *(src++) ^ buf[n]; | |
85 | n = (n + 1) % AES_BLOCK_SIZE; | |
86 | } | |
87 | return (1); | |
88 | } | |
89 | ||
90 | static int | |
91 | ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv, | |
92 | int enc) | |
93 | { | |
94 | struct ssh_aes_ctr_ctx *c; | |
95 | ||
96 | if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) { | |
97 | c = xmalloc(sizeof(*c)); | |
98 | EVP_CIPHER_CTX_set_app_data(ctx, c); | |
99 | } | |
100 | if (key != NULL) | |
101 | AES_set_encrypt_key(key, ctx->key_len * 8, &c->aes_ctx); | |
102 | if (iv != NULL) | |
103 | memcpy(c->aes_counter, iv, AES_BLOCK_SIZE); | |
104 | return (1); | |
105 | } | |
106 | ||
107 | static int | |
108 | ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx) | |
109 | { | |
110 | struct ssh_aes_ctr_ctx *c; | |
111 | ||
112 | if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) { | |
113 | memset(c, 0, sizeof(*c)); | |
114 | xfree(c); | |
115 | EVP_CIPHER_CTX_set_app_data(ctx, NULL); | |
116 | } | |
117 | return (1); | |
118 | } | |
119 | ||
120 | void | |
121 | ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len) | |
122 | { | |
123 | struct ssh_aes_ctr_ctx *c; | |
124 | ||
125 | if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL) | |
126 | fatal("ssh_aes_ctr_iv: no context"); | |
127 | if (doset) | |
128 | memcpy(c->aes_counter, iv, len); | |
129 | else | |
130 | memcpy(iv, c->aes_counter, len); | |
131 | } | |
132 | ||
133 | const EVP_CIPHER * | |
134 | evp_aes_128_ctr(void) | |
135 | { | |
136 | static EVP_CIPHER aes_ctr; | |
137 | ||
138 | memset(&aes_ctr, 0, sizeof(EVP_CIPHER)); | |
139 | aes_ctr.nid = NID_undef; | |
140 | aes_ctr.block_size = AES_BLOCK_SIZE; | |
141 | aes_ctr.iv_len = AES_BLOCK_SIZE; | |
142 | aes_ctr.key_len = 16; | |
143 | aes_ctr.init = ssh_aes_ctr_init; | |
144 | aes_ctr.cleanup = ssh_aes_ctr_cleanup; | |
145 | aes_ctr.do_cipher = ssh_aes_ctr; | |
146 | aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH | | |
147 | EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV; | |
148 | return (&aes_ctr); | |
149 | } |