PolarSSL v1.1.5
pem.c
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1 /*
2  * Privacy Enhanced Mail (PEM) decoding
3  *
4  * Copyright (C) 2006-2010, Brainspark B.V.
5  *
6  * This file is part of PolarSSL (http://www.polarssl.org)
7  * Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
8  *
9  * All rights reserved.
10  *
11  * This program is free software; you can redistribute it and/or modify
12  * it under the terms of the GNU General Public License as published by
13  * the Free Software Foundation; either version 2 of the License, or
14  * (at your option) any later version.
15  *
16  * This program is distributed in the hope that it will be useful,
17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19  * GNU General Public License for more details.
20  *
21  * You should have received a copy of the GNU General Public License along
22  * with this program; if not, write to the Free Software Foundation, Inc.,
23  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
24  */
25 
26 #include "polarssl/config.h"
27 
28 #if defined(POLARSSL_PEM_C)
29 
30 #include "polarssl/pem.h"
31 #include "polarssl/base64.h"
32 #include "polarssl/des.h"
33 #include "polarssl/aes.h"
34 #include "polarssl/md5.h"
35 #include "polarssl/cipher.h"
36 
37 #include <stdlib.h>
38 
39 void pem_init( pem_context *ctx )
40 {
41  memset( ctx, 0, sizeof( pem_context ) );
42 }
43 
44 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
45 /*
46  * Read a 16-byte hex string and convert it to binary
47  */
48 static int pem_get_iv( const unsigned char *s, unsigned char *iv, size_t iv_len )
49 {
50  size_t i, j, k;
51 
52  memset( iv, 0, iv_len );
53 
54  for( i = 0; i < iv_len * 2; i++, s++ )
55  {
56  if( *s >= '0' && *s <= '9' ) j = *s - '0'; else
57  if( *s >= 'A' && *s <= 'F' ) j = *s - '7'; else
58  if( *s >= 'a' && *s <= 'f' ) j = *s - 'W'; else
60 
61  k = ( ( i & 1 ) != 0 ) ? j : j << 4;
62 
63  iv[i >> 1] = (unsigned char)( iv[i >> 1] | k );
64  }
65 
66  return( 0 );
67 }
68 
69 static void pem_pbkdf1( unsigned char *key, size_t keylen,
70  unsigned char *iv,
71  const unsigned char *pwd, size_t pwdlen )
72 {
73  md5_context md5_ctx;
74  unsigned char md5sum[16];
75  size_t use_len;
76 
77  /*
78  * key[ 0..15] = MD5(pwd || IV)
79  */
80  md5_starts( &md5_ctx );
81  md5_update( &md5_ctx, pwd, pwdlen );
82  md5_update( &md5_ctx, iv, 8 );
83  md5_finish( &md5_ctx, md5sum );
84 
85  if( keylen <= 16 )
86  {
87  memcpy( key, md5sum, keylen );
88 
89  memset( &md5_ctx, 0, sizeof( md5_ctx ) );
90  memset( md5sum, 0, 16 );
91  return;
92  }
93 
94  memcpy( key, md5sum, 16 );
95 
96  /*
97  * key[16..23] = MD5(key[ 0..15] || pwd || IV])
98  */
99  md5_starts( &md5_ctx );
100  md5_update( &md5_ctx, md5sum, 16 );
101  md5_update( &md5_ctx, pwd, pwdlen );
102  md5_update( &md5_ctx, iv, 8 );
103  md5_finish( &md5_ctx, md5sum );
104 
105  use_len = 16;
106  if( keylen < 32 )
107  use_len = keylen - 16;
108 
109  memcpy( key + 16, md5sum, use_len );
110 
111  memset( &md5_ctx, 0, sizeof( md5_ctx ) );
112  memset( md5sum, 0, 16 );
113 }
114 
115 #if defined(POLARSSL_DES_C)
116 /*
117  * Decrypt with DES-CBC, using PBKDF1 for key derivation
118  */
119 static void pem_des_decrypt( unsigned char des_iv[8],
120  unsigned char *buf, size_t buflen,
121  const unsigned char *pwd, size_t pwdlen )
122 {
123  des_context des_ctx;
124  unsigned char des_key[8];
125 
126  pem_pbkdf1( des_key, 8, des_iv, pwd, pwdlen );
127 
128  des_setkey_dec( &des_ctx, des_key );
129  des_crypt_cbc( &des_ctx, DES_DECRYPT, buflen,
130  des_iv, buf, buf );
131 
132  memset( &des_ctx, 0, sizeof( des_ctx ) );
133  memset( des_key, 0, 8 );
134 }
135 
136 /*
137  * Decrypt with 3DES-CBC, using PBKDF1 for key derivation
138  */
139 static void pem_des3_decrypt( unsigned char des3_iv[8],
140  unsigned char *buf, size_t buflen,
141  const unsigned char *pwd, size_t pwdlen )
142 {
143  des3_context des3_ctx;
144  unsigned char des3_key[24];
145 
146  pem_pbkdf1( des3_key, 24, des3_iv, pwd, pwdlen );
147 
148  des3_set3key_dec( &des3_ctx, des3_key );
149  des3_crypt_cbc( &des3_ctx, DES_DECRYPT, buflen,
150  des3_iv, buf, buf );
151 
152  memset( &des3_ctx, 0, sizeof( des3_ctx ) );
153  memset( des3_key, 0, 24 );
154 }
155 #endif /* POLARSSL_DES_C */
156 
157 #if defined(POLARSSL_AES_C)
158 /*
159  * Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation
160  */
161 static void pem_aes_decrypt( unsigned char aes_iv[16], unsigned int keylen,
162  unsigned char *buf, size_t buflen,
163  const unsigned char *pwd, size_t pwdlen )
164 {
165  aes_context aes_ctx;
166  unsigned char aes_key[32];
167 
168  pem_pbkdf1( aes_key, keylen, aes_iv, pwd, pwdlen );
169 
170  aes_setkey_dec( &aes_ctx, aes_key, keylen * 8 );
171  aes_crypt_cbc( &aes_ctx, AES_DECRYPT, buflen,
172  aes_iv, buf, buf );
173 
174  memset( &aes_ctx, 0, sizeof( aes_ctx ) );
175  memset( aes_key, 0, keylen );
176 }
177 #endif /* POLARSSL_AES_C */
178 
179 #endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
180 
181 int pem_read_buffer( pem_context *ctx, char *header, char *footer, const unsigned char *data, const unsigned char *pwd, size_t pwdlen, size_t *use_len )
182 {
183  int ret, enc;
184  size_t len;
185  unsigned char *buf;
186  unsigned char *s1, *s2;
187 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
188  unsigned char pem_iv[16];
190 #else
191  ((void) pwd);
192  ((void) pwdlen);
193 #endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
194 
195  if( ctx == NULL )
197 
198  s1 = (unsigned char *) strstr( (char *) data, header );
199 
200  if( s1 == NULL )
202 
203  s2 = (unsigned char *) strstr( (char *) data, footer );
204 
205  if( s2 == NULL || s2 <= s1 )
207 
208  s1 += strlen( header );
209  if( *s1 == '\r' ) s1++;
210  if( *s1 == '\n' ) s1++;
211  else return( POLARSSL_ERR_PEM_INVALID_DATA );
212 
213  enc = 0;
214 
215  if( memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 )
216  {
217 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
218  enc++;
219 
220  s1 += 22;
221  if( *s1 == '\r' ) s1++;
222  if( *s1 == '\n' ) s1++;
223  else return( POLARSSL_ERR_PEM_INVALID_DATA );
224 
225 
226 #if defined(POLARSSL_DES_C)
227  if( memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 )
228  {
230 
231  s1 += 23;
232  if( pem_get_iv( s1, pem_iv, 8 ) != 0 )
234 
235  s1 += 16;
236  }
237  else if( memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 )
238  {
239  enc_alg = POLARSSL_CIPHER_DES_CBC;
240 
241  s1 += 18;
242  if( pem_get_iv( s1, pem_iv, 8) != 0 )
244 
245  s1 += 16;
246  }
247 #endif /* POLARSSL_DES_C */
248 
249 #if defined(POLARSSL_AES_C)
250  if( memcmp( s1, "DEK-Info: AES-", 14 ) == 0 )
251  {
252  if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 )
253  enc_alg = POLARSSL_CIPHER_AES_128_CBC;
254  else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 )
255  enc_alg = POLARSSL_CIPHER_AES_192_CBC;
256  else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 )
257  enc_alg = POLARSSL_CIPHER_AES_256_CBC;
258  else
260 
261  s1 += 22;
262  if( pem_get_iv( s1, pem_iv, 16 ) != 0 )
264 
265  s1 += 32;
266  }
267 #endif /* POLARSSL_AES_C */
268 
269  if( enc_alg == POLARSSL_CIPHER_NONE )
271 
272  if( *s1 == '\r' ) s1++;
273  if( *s1 == '\n' ) s1++;
274  else return( POLARSSL_ERR_PEM_INVALID_DATA );
275 #else
277 #endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
278  }
279 
280  len = 0;
281  ret = base64_decode( NULL, &len, s1, s2 - s1 );
282 
284  return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
285 
286  if( ( buf = (unsigned char *) malloc( len ) ) == NULL )
288 
289  if( ( ret = base64_decode( buf, &len, s1, s2 - s1 ) ) != 0 )
290  {
291  free( buf );
292  return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
293  }
294 
295  if( enc != 0 )
296  {
297 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
298  if( pwd == NULL )
299  {
300  free( buf );
302  }
303 
304 #if defined(POLARSSL_DES_C)
305  if( enc_alg == POLARSSL_CIPHER_DES_EDE3_CBC )
306  pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen );
307  else if( enc_alg == POLARSSL_CIPHER_DES_CBC )
308  pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen );
309 #endif /* POLARSSL_DES_C */
310 
311 #if defined(POLARSSL_AES_C)
312  if( enc_alg == POLARSSL_CIPHER_AES_128_CBC )
313  pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen );
314  else if( enc_alg == POLARSSL_CIPHER_AES_192_CBC )
315  pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen );
316  else if( enc_alg == POLARSSL_CIPHER_AES_256_CBC )
317  pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen );
318 #endif /* POLARSSL_AES_C */
319 
320  if( buf[0] != 0x30 || buf[1] != 0x82 ||
321  buf[4] != 0x02 || buf[5] != 0x01 )
322  {
323  free( buf );
325  }
326 #else
328 #endif
329  }
330 
331  ctx->buf = buf;
332  ctx->buflen = len;
333  s2 += strlen( footer );
334  if( *s2 == '\r' ) s2++;
335  if( *s2 == '\n' ) s2++;
336  *use_len = s2 - data;
337 
338  return( 0 );
339 }
340 
341 void pem_free( pem_context *ctx )
342 {
343  if( ctx->buf )
344  free( ctx->buf );
345 
346  if( ctx->info )
347  free( ctx->info );
348 
349  memset( ctx, 0, sizeof( pem_context ) );
350 }
351 
352 #endif