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c9307018 | 1 | /* |
2 | * Copyright (c) 2003 Markus Friedl <markus@openbsd.org> | |
3 | * | |
4 | * Permission to use, copy, modify, and distribute this software for any | |
5 | * purpose with or without fee is hereby granted, provided that the above | |
6 | * copyright notice and this permission notice appear in all copies. | |
7 | * | |
8 | * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES | |
9 | * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF | |
10 | * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR | |
11 | * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES | |
12 | * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN | |
13 | * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF | |
14 | * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. | |
15 | */ | |
16 | #include "includes.h" | |
2ce0bfe4 | 17 | RCSID("$OpenBSD: cipher-ctr.c,v 1.6 2005/07/17 07:17:55 djm Exp $"); |
c9307018 | 18 | |
19 | #include <openssl/evp.h> | |
20 | ||
21 | #include "log.h" | |
22 | #include "xmalloc.h" | |
23 | ||
08822d99 | 24 | /* compatibility with old or broken OpenSSL versions */ |
25 | #include "openbsd-compat/openssl-compat.h" | |
ebcd87da | 26 | |
08822d99 | 27 | #ifdef USE_BUILTIN_RIJNDAEL |
c9307018 | 28 | #include "rijndael.h" |
29 | #define AES_KEY rijndael_ctx | |
30 | #define AES_BLOCK_SIZE 16 | |
31 | #define AES_encrypt(a, b, c) rijndael_encrypt(c, a, b) | |
32 | #define AES_set_encrypt_key(a, b, c) rijndael_set_key(c, (char *)a, b, 1) | |
33 | #else | |
34 | #include <openssl/aes.h> | |
35 | #endif | |
36 | ||
37 | const EVP_CIPHER *evp_aes_128_ctr(void); | |
38 | void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); | |
39 | ||
40 | struct ssh_aes_ctr_ctx | |
41 | { | |
42 | AES_KEY aes_ctx; | |
43 | u_char aes_counter[AES_BLOCK_SIZE]; | |
44 | }; | |
45 | ||
46 | /* | |
47 | * increment counter 'ctr', | |
48 | * the counter is of size 'len' bytes and stored in network-byte-order. | |
49 | * (LSB at ctr[len-1], MSB at ctr[0]) | |
50 | */ | |
51 | static void | |
52 | ssh_ctr_inc(u_char *ctr, u_int len) | |
53 | { | |
54 | int i; | |
55 | ||
56 | for (i = len - 1; i >= 0; i--) | |
57 | if (++ctr[i]) /* continue on overflow */ | |
58 | return; | |
59 | } | |
60 | ||
61 | static int | |
62 | ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src, | |
63 | u_int len) | |
64 | { | |
65 | struct ssh_aes_ctr_ctx *c; | |
66 | u_int n = 0; | |
67 | u_char buf[AES_BLOCK_SIZE]; | |
68 | ||
69 | if (len == 0) | |
70 | return (1); | |
71 | if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) | |
72 | return (0); | |
73 | ||
74 | while ((len--) > 0) { | |
75 | if (n == 0) { | |
76 | AES_encrypt(c->aes_counter, buf, &c->aes_ctx); | |
77 | ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE); | |
78 | } | |
79 | *(dest++) = *(src++) ^ buf[n]; | |
80 | n = (n + 1) % AES_BLOCK_SIZE; | |
81 | } | |
82 | return (1); | |
83 | } | |
84 | ||
85 | static int | |
86 | ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv, | |
87 | int enc) | |
88 | { | |
89 | struct ssh_aes_ctr_ctx *c; | |
90 | ||
91 | if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) { | |
92 | c = xmalloc(sizeof(*c)); | |
93 | EVP_CIPHER_CTX_set_app_data(ctx, c); | |
94 | } | |
95 | if (key != NULL) | |
540d72c3 | 96 | AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8, |
2ce0bfe4 | 97 | &c->aes_ctx); |
c9307018 | 98 | if (iv != NULL) |
99 | memcpy(c->aes_counter, iv, AES_BLOCK_SIZE); | |
100 | return (1); | |
101 | } | |
102 | ||
103 | static int | |
104 | ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx) | |
105 | { | |
106 | struct ssh_aes_ctr_ctx *c; | |
107 | ||
108 | if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) { | |
109 | memset(c, 0, sizeof(*c)); | |
110 | xfree(c); | |
111 | EVP_CIPHER_CTX_set_app_data(ctx, NULL); | |
112 | } | |
113 | return (1); | |
114 | } | |
115 | ||
116 | void | |
117 | ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len) | |
118 | { | |
119 | struct ssh_aes_ctr_ctx *c; | |
120 | ||
121 | if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL) | |
122 | fatal("ssh_aes_ctr_iv: no context"); | |
123 | if (doset) | |
124 | memcpy(c->aes_counter, iv, len); | |
125 | else | |
126 | memcpy(iv, c->aes_counter, len); | |
127 | } | |
128 | ||
129 | const EVP_CIPHER * | |
130 | evp_aes_128_ctr(void) | |
131 | { | |
132 | static EVP_CIPHER aes_ctr; | |
133 | ||
134 | memset(&aes_ctr, 0, sizeof(EVP_CIPHER)); | |
135 | aes_ctr.nid = NID_undef; | |
136 | aes_ctr.block_size = AES_BLOCK_SIZE; | |
137 | aes_ctr.iv_len = AES_BLOCK_SIZE; | |
138 | aes_ctr.key_len = 16; | |
139 | aes_ctr.init = ssh_aes_ctr_init; | |
140 | aes_ctr.cleanup = ssh_aes_ctr_cleanup; | |
141 | aes_ctr.do_cipher = ssh_aes_ctr; | |
ebcd87da | 142 | #ifndef SSH_OLD_EVP |
c9307018 | 143 | aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH | |
144 | EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV; | |
ebcd87da | 145 | #endif |
c9307018 | 146 | return (&aes_ctr); |
147 | } |