PolarSSL v1.2.8
pem.c
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1 /*
2  * Privacy Enhanced Mail (PEM) decoding
3  *
4  * Copyright (C) 2006-2013, 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  const unsigned char *s1, *s2, *end;
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( (const char *) data, header );
199 
200  if( s1 == NULL )
202 
203  s2 = (unsigned char *) strstr( (const 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++;
212 
213  end = s2;
214  end += strlen( footer );
215  if( *end == '\r' ) end++;
216  if( *end == '\n' ) end++;
217  *use_len = end - data;
218 
219  enc = 0;
220 
221  if( memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 )
222  {
223 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
224  enc++;
225 
226  s1 += 22;
227  if( *s1 == '\r' ) s1++;
228  if( *s1 == '\n' ) s1++;
229  else return( POLARSSL_ERR_PEM_INVALID_DATA );
230 
231 
232 #if defined(POLARSSL_DES_C)
233  if( memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 )
234  {
236 
237  s1 += 23;
238  if( pem_get_iv( s1, pem_iv, 8 ) != 0 )
240 
241  s1 += 16;
242  }
243  else if( memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 )
244  {
245  enc_alg = POLARSSL_CIPHER_DES_CBC;
246 
247  s1 += 18;
248  if( pem_get_iv( s1, pem_iv, 8) != 0 )
250 
251  s1 += 16;
252  }
253 #endif /* POLARSSL_DES_C */
254 
255 #if defined(POLARSSL_AES_C)
256  if( memcmp( s1, "DEK-Info: AES-", 14 ) == 0 )
257  {
258  if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 )
259  enc_alg = POLARSSL_CIPHER_AES_128_CBC;
260  else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 )
261  enc_alg = POLARSSL_CIPHER_AES_192_CBC;
262  else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 )
263  enc_alg = POLARSSL_CIPHER_AES_256_CBC;
264  else
266 
267  s1 += 22;
268  if( pem_get_iv( s1, pem_iv, 16 ) != 0 )
270 
271  s1 += 32;
272  }
273 #endif /* POLARSSL_AES_C */
274 
275  if( enc_alg == POLARSSL_CIPHER_NONE )
277 
278  if( *s1 == '\r' ) s1++;
279  if( *s1 == '\n' ) s1++;
280  else return( POLARSSL_ERR_PEM_INVALID_DATA );
281 #else
283 #endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
284  }
285 
286  len = 0;
287  ret = base64_decode( NULL, &len, s1, s2 - s1 );
288 
290  return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
291 
292  if( ( buf = (unsigned char *) malloc( len ) ) == NULL )
294 
295  if( ( ret = base64_decode( buf, &len, s1, s2 - s1 ) ) != 0 )
296  {
297  free( buf );
298  return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
299  }
300 
301  if( enc != 0 )
302  {
303 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
304  if( pwd == NULL )
305  {
306  free( buf );
308  }
309 
310 #if defined(POLARSSL_DES_C)
311  if( enc_alg == POLARSSL_CIPHER_DES_EDE3_CBC )
312  pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen );
313  else if( enc_alg == POLARSSL_CIPHER_DES_CBC )
314  pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen );
315 #endif /* POLARSSL_DES_C */
316 
317 #if defined(POLARSSL_AES_C)
318  if( enc_alg == POLARSSL_CIPHER_AES_128_CBC )
319  pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen );
320  else if( enc_alg == POLARSSL_CIPHER_AES_192_CBC )
321  pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen );
322  else if( enc_alg == POLARSSL_CIPHER_AES_256_CBC )
323  pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen );
324 #endif /* POLARSSL_AES_C */
325 
326  if( buf[0] != 0x30 || buf[1] != 0x82 ||
327  buf[4] != 0x02 || buf[5] != 0x01 )
328  {
329  free( buf );
331  }
332 #else
333  free( buf );
335 #endif
336  }
337 
338  ctx->buf = buf;
339  ctx->buflen = len;
340 
341  return( 0 );
342 }
343 
344 void pem_free( pem_context *ctx )
345 {
346  if( ctx->buf )
347  free( ctx->buf );
348 
349  if( ctx->info )
350  free( ctx->info );
351 
352  memset( ctx, 0, sizeof( pem_context ) );
353 }
354 
355 #endif