Variable key length crypters use default key length if zero given
[strongswan.git] / src / libstrongswan / plugins / openssl / openssl_crypter.c
1 /*
2 * Copyright (C) 2008 Tobias Brunner
3 * Hochschule fuer Technik Rapperswil
4 *
5 * This program is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License as published by the
7 * Free Software Foundation; either version 2 of the License, or (at your
8 * option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
12 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * for more details.
14 */
15
16 #include "openssl_crypter.h"
17
18 #include <openssl/evp.h>
19
20 typedef struct private_openssl_crypter_t private_openssl_crypter_t;
21
22 /**
23 * Private data of openssl_crypter_t
24 */
25 struct private_openssl_crypter_t {
26
27 /**
28 * Public part of this class.
29 */
30 openssl_crypter_t public;
31
32 /*
33 * the key
34 */
35 chunk_t key;
36
37 /*
38 * the cipher to use
39 */
40 const EVP_CIPHER *cipher;
41 };
42
43 /**
44 * Look up an OpenSSL algorithm name and validate its key size
45 */
46 static char* lookup_algorithm(u_int16_t ikev2_algo, size_t *key_size)
47 {
48 struct {
49 /* identifier specified in IKEv2 */
50 int ikev2_id;
51 /* name of the algorithm, as used in OpenSSL */
52 char *name;
53 /* default key size in bytes */
54 size_t key_def;
55 /* minimum key size */
56 size_t key_min;
57 /* maximum key size */
58 size_t key_max;
59 } mappings[] = {
60 {ENCR_DES, "des", 8, 8, 8},
61 {ENCR_3DES, "des3", 24, 24, 24},
62 {ENCR_RC5, "rc5", 16, 5, 255},
63 {ENCR_IDEA, "idea", 16, 16, 16},
64 {ENCR_CAST, "cast", 16, 5, 16},
65 {ENCR_BLOWFISH, "blowfish", 16, 5, 56},
66 };
67 int i;
68
69 for (i = 0; i < countof(mappings); i++)
70 {
71 if (ikev2_algo == mappings[i].ikev2_id)
72 {
73 /* set the key size if it is not set */
74 if (*key_size == 0)
75 {
76 *key_size = mappings[i].key_def;
77 }
78 /* validate key size */
79 if (*key_size < mappings[i].key_min ||
80 *key_size > mappings[i].key_max)
81 {
82 return NULL;
83 }
84 return mappings[i].name;
85 }
86 }
87 return NULL;
88 }
89
90 /**
91 * Do the actual en/decryption in an EVP context
92 */
93 static void crypt(private_openssl_crypter_t *this, chunk_t data, chunk_t iv,
94 chunk_t *dst, int enc)
95 {
96 int len;
97 u_char *out;
98
99 out = data.ptr;
100 if (dst)
101 {
102 *dst = chunk_alloc(data.len);
103 out = dst->ptr;
104 }
105 EVP_CIPHER_CTX ctx;
106 EVP_CIPHER_CTX_init(&ctx);
107 EVP_CipherInit_ex(&ctx, this->cipher, NULL, NULL, NULL, enc);
108 EVP_CIPHER_CTX_set_padding(&ctx, 0); /* disable padding */
109 EVP_CIPHER_CTX_set_key_length(&ctx, this->key.len);
110 EVP_CipherInit_ex(&ctx, NULL, NULL, this->key.ptr, iv.ptr, enc);
111 EVP_CipherUpdate(&ctx, out, &len, data.ptr, data.len);
112 EVP_CipherFinal_ex(&ctx, out + len, &len); /* since padding is disabled this does nothing */
113 EVP_CIPHER_CTX_cleanup(&ctx);
114 }
115
116 METHOD(crypter_t, decrypt, void,
117 private_openssl_crypter_t *this, chunk_t data, chunk_t iv, chunk_t *dst)
118 {
119 crypt(this, data, iv, dst, 0);
120 }
121
122 METHOD(crypter_t, encrypt, void,
123 private_openssl_crypter_t *this, chunk_t data, chunk_t iv, chunk_t *dst)
124 {
125 crypt(this, data, iv, dst, 1);
126 }
127
128 METHOD(crypter_t, get_block_size, size_t,
129 private_openssl_crypter_t *this)
130 {
131 return this->cipher->block_size;
132 }
133
134 METHOD(crypter_t, get_iv_size, size_t,
135 private_openssl_crypter_t *this)
136 {
137 return this->cipher->block_size;
138 }
139
140 METHOD(crypter_t, get_key_size, size_t,
141 private_openssl_crypter_t *this)
142 {
143 return this->key.len;
144 }
145
146 METHOD(crypter_t, set_key, void,
147 private_openssl_crypter_t *this, chunk_t key)
148 {
149 memcpy(this->key.ptr, key.ptr, min(key.len, this->key.len));
150 }
151
152 METHOD(crypter_t, destroy, void,
153 private_openssl_crypter_t *this)
154 {
155 free(this->key.ptr);
156 free(this);
157 }
158
159 /*
160 * Described in header
161 */
162 openssl_crypter_t *openssl_crypter_create(encryption_algorithm_t algo,
163 size_t key_size)
164 {
165 private_openssl_crypter_t *this;
166
167 INIT(this,
168 .public.crypter = {
169 .encrypt = _encrypt,
170 .decrypt = _decrypt,
171 .get_block_size = _get_block_size,
172 .get_iv_size = _get_iv_size,
173 .get_key_size = _get_key_size,
174 .set_key = _set_key,
175 .destroy = _destroy,
176 },
177 );
178
179 switch (algo)
180 {
181 case ENCR_NULL:
182 this->cipher = EVP_enc_null();
183 key_size = 0;
184 break;
185 case ENCR_AES_CBC:
186 switch (key_size)
187 {
188 case 0:
189 key_size = 16;
190 /* FALL */
191 case 16: /* AES 128 */
192 this->cipher = EVP_get_cipherbyname("aes128");
193 break;
194 case 24: /* AES-192 */
195 this->cipher = EVP_get_cipherbyname("aes192");
196 break;
197 case 32: /* AES-256 */
198 this->cipher = EVP_get_cipherbyname("aes256");
199 break;
200 default:
201 free(this);
202 return NULL;
203 }
204 break;
205 case ENCR_CAMELLIA_CBC:
206 switch (key_size)
207 {
208 case 0:
209 key_size = 16;
210 /* FALL */
211 case 16: /* CAMELLIA 128 */
212 this->cipher = EVP_get_cipherbyname("camellia128");
213 break;
214 case 24: /* CAMELLIA 192 */
215 this->cipher = EVP_get_cipherbyname("camellia192");
216 break;
217 case 32: /* CAMELLIA 256 */
218 this->cipher = EVP_get_cipherbyname("camellia256");
219 break;
220 default:
221 free(this);
222 return NULL;
223 }
224 break;
225 case ENCR_DES_ECB:
226 key_size = 8;
227 this->cipher = EVP_des_ecb();
228 break;
229 default:
230 {
231 char* name;
232
233 name = lookup_algorithm(algo, &key_size);
234 if (!name)
235 {
236 /* algo unavailable or key_size invalid */
237 free(this);
238 return NULL;
239 }
240 this->cipher = EVP_get_cipherbyname(name);
241 break;
242 }
243 }
244
245 if (!this->cipher)
246 {
247 /* OpenSSL does not support the requested algo */
248 free(this);
249 return NULL;
250 }
251
252 this->key = chunk_alloc(key_size);
253
254 return &this->public;
255 }