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1 | /* $OpenBSD: cipher-ctr.c,v 1.10 2006/08/03 03:34:42 deraadt Exp $ */ | |
2 | /* | |
3 | * Copyright (c) 2003 Markus Friedl <markus@openbsd.org> | |
4 | * | |
5 | * Permission to use, copy, modify, and distribute this software for any | |
6 | * purpose with or without fee is hereby granted, provided that the above | |
7 | * copyright notice and this permission notice appear in all copies. | |
8 | * | |
9 | * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES | |
10 | * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF | |
11 | * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR | |
12 | * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES | |
13 | * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN | |
14 | * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF | |
15 | * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. | |
16 | */ | |
17 | #include "includes.h" | |
18 | ||
19 | #include <sys/types.h> | |
20 | ||
21 | #include <stdarg.h> | |
22 | #include <string.h> | |
23 | ||
24 | #include <openssl/evp.h> | |
25 | ||
26 | #include "xmalloc.h" | |
27 | #include "log.h" | |
28 | ||
29 | /* compatibility with old or broken OpenSSL versions */ | |
30 | #include "openbsd-compat/openssl-compat.h" | |
31 | ||
32 | #ifndef USE_BUILTIN_RIJNDAEL | |
33 | #include <openssl/aes.h> | |
34 | #endif | |
35 | ||
36 | const EVP_CIPHER *evp_aes_128_ctr(void); | |
37 | void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int); | |
38 | ||
39 | struct ssh_aes_ctr_ctx | |
40 | { | |
41 | AES_KEY aes_ctx; | |
42 | u_char aes_counter[AES_BLOCK_SIZE]; | |
43 | }; | |
44 | ||
45 | /* | |
46 | * increment counter 'ctr', | |
47 | * the counter is of size 'len' bytes and stored in network-byte-order. | |
48 | * (LSB at ctr[len-1], MSB at ctr[0]) | |
49 | */ | |
50 | static void | |
51 | ssh_ctr_inc(u_char *ctr, u_int len) | |
52 | { | |
53 | int i; | |
54 | ||
55 | for (i = len - 1; i >= 0; i--) | |
56 | if (++ctr[i]) /* continue on overflow */ | |
57 | return; | |
58 | } | |
59 | ||
60 | static int | |
61 | ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src, | |
62 | u_int len) | |
63 | { | |
64 | struct ssh_aes_ctr_ctx *c; | |
65 | u_int n = 0; | |
66 | u_char buf[AES_BLOCK_SIZE]; | |
67 | ||
68 | if (len == 0) | |
69 | return (1); | |
70 | if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) | |
71 | return (0); | |
72 | ||
73 | while ((len--) > 0) { | |
74 | if (n == 0) { | |
75 | AES_encrypt(c->aes_counter, buf, &c->aes_ctx); | |
76 | ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE); | |
77 | } | |
78 | *(dest++) = *(src++) ^ buf[n]; | |
79 | n = (n + 1) % AES_BLOCK_SIZE; | |
80 | } | |
81 | return (1); | |
82 | } | |
83 | ||
84 | static int | |
85 | ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv, | |
86 | int enc) | |
87 | { | |
88 | struct ssh_aes_ctr_ctx *c; | |
89 | ||
90 | if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) { | |
91 | c = xmalloc(sizeof(*c)); | |
92 | EVP_CIPHER_CTX_set_app_data(ctx, c); | |
93 | } | |
94 | if (key != NULL) | |
95 | AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8, | |
96 | &c->aes_ctx); | |
97 | if (iv != NULL) | |
98 | memcpy(c->aes_counter, iv, AES_BLOCK_SIZE); | |
99 | return (1); | |
100 | } | |
101 | ||
102 | static int | |
103 | ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx) | |
104 | { | |
105 | struct ssh_aes_ctr_ctx *c; | |
106 | ||
107 | if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) { | |
108 | memset(c, 0, sizeof(*c)); | |
109 | xfree(c); | |
110 | EVP_CIPHER_CTX_set_app_data(ctx, NULL); | |
111 | } | |
112 | return (1); | |
113 | } | |
114 | ||
115 | void | |
116 | ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len) | |
117 | { | |
118 | struct ssh_aes_ctr_ctx *c; | |
119 | ||
120 | if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL) | |
121 | fatal("ssh_aes_ctr_iv: no context"); | |
122 | if (doset) | |
123 | memcpy(c->aes_counter, iv, len); | |
124 | else | |
125 | memcpy(iv, c->aes_counter, len); | |
126 | } | |
127 | ||
128 | const EVP_CIPHER * | |
129 | evp_aes_128_ctr(void) | |
130 | { | |
131 | static EVP_CIPHER aes_ctr; | |
132 | ||
133 | memset(&aes_ctr, 0, sizeof(EVP_CIPHER)); | |
134 | aes_ctr.nid = NID_undef; | |
135 | aes_ctr.block_size = AES_BLOCK_SIZE; | |
136 | aes_ctr.iv_len = AES_BLOCK_SIZE; | |
137 | aes_ctr.key_len = 16; | |
138 | aes_ctr.init = ssh_aes_ctr_init; | |
139 | aes_ctr.cleanup = ssh_aes_ctr_cleanup; | |
140 | aes_ctr.do_cipher = ssh_aes_ctr; | |
141 | #ifndef SSH_OLD_EVP | |
142 | aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH | | |
143 | EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV; | |
144 | #endif | |
145 | return (&aes_ctr); | |
146 | } |