PolarSSL v1.3.3
pem.c
Go to the documentation of this file.
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_PARSE_C) || defined(POLARSSL_PEM_WRITE_C)
29 #include "polarssl/pem.h"
30 #include "polarssl/base64.h"
31 #include "polarssl/des.h"
32 #include "polarssl/aes.h"
33 #include "polarssl/md5.h"
34 #include "polarssl/cipher.h"
35 
36 #if defined(POLARSSL_MEMORY_C)
37 #include "polarssl/memory.h"
38 #else
39 #define polarssl_malloc malloc
40 #define polarssl_free free
41 #endif
42 
43 #include <stdlib.h>
44 
45 #if defined(POLARSSL_PEM_PARSE_C)
46 void pem_init( pem_context *ctx )
47 {
48  memset( ctx, 0, sizeof( pem_context ) );
49 }
50 
51 #if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) && \
52  ( defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C) )
53 /*
54  * Read a 16-byte hex string and convert it to binary
55  */
56 static int pem_get_iv( const unsigned char *s, unsigned char *iv, size_t iv_len )
57 {
58  size_t i, j, k;
59 
60  memset( iv, 0, iv_len );
61 
62  for( i = 0; i < iv_len * 2; i++, s++ )
63  {
64  if( *s >= '0' && *s <= '9' ) j = *s - '0'; else
65  if( *s >= 'A' && *s <= 'F' ) j = *s - '7'; else
66  if( *s >= 'a' && *s <= 'f' ) j = *s - 'W'; else
68 
69  k = ( ( i & 1 ) != 0 ) ? j : j << 4;
70 
71  iv[i >> 1] = (unsigned char)( iv[i >> 1] | k );
72  }
73 
74  return( 0 );
75 }
76 
77 static void pem_pbkdf1( unsigned char *key, size_t keylen,
78  unsigned char *iv,
79  const unsigned char *pwd, size_t pwdlen )
80 {
81  md5_context md5_ctx;
82  unsigned char md5sum[16];
83  size_t use_len;
84 
85  /*
86  * key[ 0..15] = MD5(pwd || IV)
87  */
88  md5_starts( &md5_ctx );
89  md5_update( &md5_ctx, pwd, pwdlen );
90  md5_update( &md5_ctx, iv, 8 );
91  md5_finish( &md5_ctx, md5sum );
92 
93  if( keylen <= 16 )
94  {
95  memcpy( key, md5sum, keylen );
96 
97  memset( &md5_ctx, 0, sizeof( md5_ctx ) );
98  memset( md5sum, 0, 16 );
99  return;
100  }
101 
102  memcpy( key, md5sum, 16 );
103 
104  /*
105  * key[16..23] = MD5(key[ 0..15] || pwd || IV])
106  */
107  md5_starts( &md5_ctx );
108  md5_update( &md5_ctx, md5sum, 16 );
109  md5_update( &md5_ctx, pwd, pwdlen );
110  md5_update( &md5_ctx, iv, 8 );
111  md5_finish( &md5_ctx, md5sum );
112 
113  use_len = 16;
114  if( keylen < 32 )
115  use_len = keylen - 16;
116 
117  memcpy( key + 16, md5sum, use_len );
118 
119  memset( &md5_ctx, 0, sizeof( md5_ctx ) );
120  memset( md5sum, 0, 16 );
121 }
122 
123 #if defined(POLARSSL_DES_C)
124 /*
125  * Decrypt with DES-CBC, using PBKDF1 for key derivation
126  */
127 static void pem_des_decrypt( unsigned char des_iv[8],
128  unsigned char *buf, size_t buflen,
129  const unsigned char *pwd, size_t pwdlen )
130 {
131  des_context des_ctx;
132  unsigned char des_key[8];
133 
134  pem_pbkdf1( des_key, 8, des_iv, pwd, pwdlen );
135 
136  des_setkey_dec( &des_ctx, des_key );
137  des_crypt_cbc( &des_ctx, DES_DECRYPT, buflen,
138  des_iv, buf, buf );
139 
140  memset( &des_ctx, 0, sizeof( des_ctx ) );
141  memset( des_key, 0, 8 );
142 }
143 
144 /*
145  * Decrypt with 3DES-CBC, using PBKDF1 for key derivation
146  */
147 static void pem_des3_decrypt( unsigned char des3_iv[8],
148  unsigned char *buf, size_t buflen,
149  const unsigned char *pwd, size_t pwdlen )
150 {
151  des3_context des3_ctx;
152  unsigned char des3_key[24];
153 
154  pem_pbkdf1( des3_key, 24, des3_iv, pwd, pwdlen );
155 
156  des3_set3key_dec( &des3_ctx, des3_key );
157  des3_crypt_cbc( &des3_ctx, DES_DECRYPT, buflen,
158  des3_iv, buf, buf );
159 
160  memset( &des3_ctx, 0, sizeof( des3_ctx ) );
161  memset( des3_key, 0, 24 );
162 }
163 #endif /* POLARSSL_DES_C */
164 
165 #if defined(POLARSSL_AES_C)
166 /*
167  * Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation
168  */
169 static void pem_aes_decrypt( unsigned char aes_iv[16], unsigned int keylen,
170  unsigned char *buf, size_t buflen,
171  const unsigned char *pwd, size_t pwdlen )
172 {
173  aes_context aes_ctx;
174  unsigned char aes_key[32];
175 
176  pem_pbkdf1( aes_key, keylen, aes_iv, pwd, pwdlen );
177 
178  aes_setkey_dec( &aes_ctx, aes_key, keylen * 8 );
179  aes_crypt_cbc( &aes_ctx, AES_DECRYPT, buflen,
180  aes_iv, buf, buf );
181 
182  memset( &aes_ctx, 0, sizeof( aes_ctx ) );
183  memset( aes_key, 0, keylen );
184 }
185 #endif /* POLARSSL_AES_C */
186 
187 #endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
188  ( POLARSSL_AES_C || POLARSSL_DES_C ) */
189 
190 int pem_read_buffer( pem_context *ctx, const char *header, const char *footer,
191  const unsigned char *data, const unsigned char *pwd,
192  size_t pwdlen, size_t *use_len )
193 {
194  int ret, enc;
195  size_t len;
196  unsigned char *buf;
197  const unsigned char *s1, *s2, *end;
198 #if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) && \
199  ( defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C) )
200  unsigned char pem_iv[16];
202 #else
203  ((void) pwd);
204  ((void) pwdlen);
205 #endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
206  ( POLARSSL_AES_C || POLARSSL_DES_C ) */
207 
208  if( ctx == NULL )
210 
211  s1 = (unsigned char *) strstr( (const char *) data, header );
212 
213  if( s1 == NULL )
215 
216  s2 = (unsigned char *) strstr( (const char *) data, footer );
217 
218  if( s2 == NULL || s2 <= s1 )
220 
221  s1 += strlen( header );
222  if( *s1 == '\r' ) s1++;
223  if( *s1 == '\n' ) s1++;
225 
226  end = s2;
227  end += strlen( footer );
228  if( *end == '\r' ) end++;
229  if( *end == '\n' ) end++;
230  *use_len = end - data;
231 
232  enc = 0;
233 
234  if( memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 )
235  {
236 #if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) && \
237  ( defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C) )
238  enc++;
239 
240  s1 += 22;
241  if( *s1 == '\r' ) s1++;
242  if( *s1 == '\n' ) s1++;
243  else return( POLARSSL_ERR_PEM_INVALID_DATA );
244 
245 
246 #if defined(POLARSSL_DES_C)
247  if( memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 )
248  {
250 
251  s1 += 23;
252  if( pem_get_iv( s1, pem_iv, 8 ) != 0 )
254 
255  s1 += 16;
256  }
257  else if( memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 )
258  {
259  enc_alg = POLARSSL_CIPHER_DES_CBC;
260 
261  s1 += 18;
262  if( pem_get_iv( s1, pem_iv, 8) != 0 )
264 
265  s1 += 16;
266  }
267 #endif /* POLARSSL_DES_C */
268 
269 #if defined(POLARSSL_AES_C)
270  if( memcmp( s1, "DEK-Info: AES-", 14 ) == 0 )
271  {
272  if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 )
273  enc_alg = POLARSSL_CIPHER_AES_128_CBC;
274  else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 )
275  enc_alg = POLARSSL_CIPHER_AES_192_CBC;
276  else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 )
277  enc_alg = POLARSSL_CIPHER_AES_256_CBC;
278  else
280 
281  s1 += 22;
282  if( pem_get_iv( s1, pem_iv, 16 ) != 0 )
284 
285  s1 += 32;
286  }
287 #endif /* POLARSSL_AES_C */
288 
289  if( enc_alg == POLARSSL_CIPHER_NONE )
291 
292  if( *s1 == '\r' ) s1++;
293  if( *s1 == '\n' ) s1++;
294  else return( POLARSSL_ERR_PEM_INVALID_DATA );
295 #else
297 #endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
298  ( POLARSSL_AES_C || POLARSSL_DES_C ) */
299  }
300 
301  len = 0;
302  ret = base64_decode( NULL, &len, s1, s2 - s1 );
303 
305  return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
306 
307  if( ( buf = (unsigned char *) polarssl_malloc( len ) ) == NULL )
309 
310  if( ( ret = base64_decode( buf, &len, s1, s2 - s1 ) ) != 0 )
311  {
312  polarssl_free( buf );
313  return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
314  }
315 
316  if( enc != 0 )
317  {
318 #if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) && \
319  ( defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C) )
320  if( pwd == NULL )
321  {
322  polarssl_free( buf );
324  }
325 
326 #if defined(POLARSSL_DES_C)
327  if( enc_alg == POLARSSL_CIPHER_DES_EDE3_CBC )
328  pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen );
329  else if( enc_alg == POLARSSL_CIPHER_DES_CBC )
330  pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen );
331 #endif /* POLARSSL_DES_C */
332 
333 #if defined(POLARSSL_AES_C)
334  if( enc_alg == POLARSSL_CIPHER_AES_128_CBC )
335  pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen );
336  else if( enc_alg == POLARSSL_CIPHER_AES_192_CBC )
337  pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen );
338  else if( enc_alg == POLARSSL_CIPHER_AES_256_CBC )
339  pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen );
340 #endif /* POLARSSL_AES_C */
341 
342  /*
343  * The result will be ASN.1 starting with a SEQUENCE tag, with 1 to 3
344  * length bytes (allow 4 to be sure) in all known use cases.
345  *
346  * Use that as heurisitic to try detecting password mismatchs.
347  */
348  if( len <= 2 || buf[0] != 0x30 || buf[1] > 0x83 )
349  {
350  polarssl_free( buf );
352  }
353 #else
354  polarssl_free( buf );
356 #endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
357  ( POLARSSL_AES_C || POLARSSL_DES_C ) */
358  }
359 
360  ctx->buf = buf;
361  ctx->buflen = len;
362 
363  return( 0 );
364 }
365 
366 void pem_free( pem_context *ctx )
367 {
368  if( ctx->buf )
369  polarssl_free( ctx->buf );
370 
371  if( ctx->info )
372  polarssl_free( ctx->info );
373 
374  memset( ctx, 0, sizeof( pem_context ) );
375 }
376 #endif /* POLARSSL_PEM_PARSE_C */
377 
378 #if defined(POLARSSL_PEM_WRITE_C)
379 int pem_write_buffer( const char *header, const char *footer,
380  const unsigned char *der_data, size_t der_len,
381  unsigned char *buf, size_t buf_len, size_t *olen )
382 {
383  int ret;
384  unsigned char *encode_buf, *c, *p = buf;
385  size_t len = 0, use_len = 0;
386  size_t add_len = strlen( header ) + strlen( footer ) + ( use_len / 64 ) + 1;
387 
388  base64_encode( NULL, &use_len, der_data, der_len );
389  if( use_len + add_len > buf_len )
390  {
391  *olen = use_len + add_len;
393  }
394 
395  if( ( encode_buf = polarssl_malloc( use_len ) ) == NULL )
397 
398  if( ( ret = base64_encode( encode_buf, &use_len, der_data,
399  der_len ) ) != 0 )
400  {
401  polarssl_free( encode_buf );
402  return( ret );
403  }
404 
405  memcpy( p, header, strlen( header ) );
406  p += strlen( header );
407  c = encode_buf;
408 
409  while( use_len )
410  {
411  len = ( use_len > 64 ) ? 64 : use_len;
412  memcpy( p, c, len );
413  use_len -= len;
414  p += len;
415  c += len;
416  *p++ = '\n';
417  }
418 
419  memcpy( p, footer, strlen( footer ) );
420  p += strlen( footer );
421 
422  *p++ = '\0';
423  *olen = p - buf;
424 
425  polarssl_free( encode_buf );
426  return( 0 );
427 }
428 #endif /* POLARSSL_PEM_WRITE_C */
429 #endif /* POLARSSL_PEM_PARSE_C || POLARSSL_PEM_WRITE_C */
int base64_decode(unsigned char *dst, size_t *dlen, const unsigned char *src, size_t slen)
Decode a base64-formatted buffer.
#define POLARSSL_ERR_PEM_FEATURE_UNAVAILABLE
Unavailable feature, e.g.
Definition: pem.h:45
Memory allocation layer.
void *(* polarssl_malloc)(size_t len)
#define POLARSSL_ERR_PEM_UNKNOWN_ENC_ALG
Unsupported key encryption algorithm.
Definition: pem.h:42
#define POLARSSL_ERR_PEM_MALLOC_FAILED
Failed to allocate memory.
Definition: pem.h:40
#define AES_DECRYPT
Definition: aes.h:43
AES context structure.
Definition: aes.h:64
Configuration options (set of defines)
int aes_setkey_dec(aes_context *ctx, const unsigned char *key, unsigned int keysize)
AES key schedule (decryption)
void md5_finish(md5_context *ctx, unsigned char output[16])
MD5 final digest.
DES context structure.
Definition: des.h:59
int des3_set3key_dec(des3_context *ctx, const unsigned char key[DES_KEY_SIZE *3])
Triple-DES key schedule (168-bit, decryption)
#define POLARSSL_ERR_PEM_PASSWORD_REQUIRED
Private key password can&#39;t be empty.
Definition: pem.h:43
Privacy Enhanced Mail (PEM) decoding.
#define POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL
Output buffer too small.
Definition: base64.h:32
Triple-DES context structure.
Definition: des.h:69
cipher_type_t
Definition: cipher.h:75
int aes_crypt_cbc(aes_context *ctx, int mode, size_t length, unsigned char iv[16], const unsigned char *input, unsigned char *output)
AES-CBC buffer encryption/decryption Length should be a multiple of the block size (16 bytes) ...
void(* polarssl_free)(void *ptr)
AES block cipher.
#define POLARSSL_ERR_PEM_PASSWORD_MISMATCH
Given private key password does not allow for correct decryption.
Definition: pem.h:44
void md5_starts(md5_context *ctx)
MD5 context setup.
#define POLARSSL_ERR_PEM_INVALID_ENC_IV
RSA IV is not in hex-format.
Definition: pem.h:41
MD5 context structure.
Definition: md5.h:54
Generic cipher wrapper.
#define POLARSSL_ERR_PEM_INVALID_DATA
PEM string is not as expected.
Definition: pem.h:39
int des_crypt_cbc(des_context *ctx, int mode, size_t length, unsigned char iv[8], const unsigned char *input, unsigned char *output)
DES-CBC buffer encryption/decryption.
DES block cipher.
RFC 1521 base64 encoding/decoding.
int des_setkey_dec(des_context *ctx, const unsigned char key[DES_KEY_SIZE])
DES key schedule (56-bit, decryption)
#define DES_DECRYPT
Definition: des.h:42
void md5_update(md5_context *ctx, const unsigned char *input, size_t ilen)
MD5 process buffer.
#define POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT
No PEM header or footer found.
Definition: pem.h:38
MD5 message digest algorithm (hash function)
#define POLARSSL_ERR_PEM_BAD_INPUT_DATA
Bad input parameters to function.
Definition: pem.h:46
#define POLARSSL_ERR_BASE64_INVALID_CHARACTER
Invalid character in input.
Definition: base64.h:33
int base64_encode(unsigned char *dst, size_t *dlen, const unsigned char *src, size_t slen)
Encode a buffer into base64 format.
int des3_crypt_cbc(des3_context *ctx, int mode, size_t length, unsigned char iv[8], const unsigned char *input, unsigned char *output)
3DES-CBC buffer encryption/decryption