PolarSSL v1.2.12
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 /* Implementation that should never be optimized out by the compiler */
40 static void polarssl_zeroize( void *v, size_t n ) {
41  volatile unsigned char *p = v; while( n-- ) *p++ = 0;
42 }
43 
44 void pem_init( pem_context *ctx )
45 {
46  memset( ctx, 0, sizeof( pem_context ) );
47 }
48 
49 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
50 /*
51  * Read a 16-byte hex string and convert it to binary
52  */
53 static int pem_get_iv( const unsigned char *s, unsigned char *iv, size_t iv_len )
54 {
55  size_t i, j, k;
56 
57  memset( iv, 0, iv_len );
58 
59  for( i = 0; i < iv_len * 2; i++, s++ )
60  {
61  if( *s >= '0' && *s <= '9' ) j = *s - '0'; else
62  if( *s >= 'A' && *s <= 'F' ) j = *s - '7'; else
63  if( *s >= 'a' && *s <= 'f' ) j = *s - 'W'; else
65 
66  k = ( ( i & 1 ) != 0 ) ? j : j << 4;
67 
68  iv[i >> 1] = (unsigned char)( iv[i >> 1] | k );
69  }
70 
71  return( 0 );
72 }
73 
74 static void pem_pbkdf1( unsigned char *key, size_t keylen,
75  unsigned char *iv,
76  const unsigned char *pwd, size_t pwdlen )
77 {
78  md5_context md5_ctx;
79  unsigned char md5sum[16];
80  size_t use_len;
81 
82  /*
83  * key[ 0..15] = MD5(pwd || IV)
84  */
85  md5_starts( &md5_ctx );
86  md5_update( &md5_ctx, pwd, pwdlen );
87  md5_update( &md5_ctx, iv, 8 );
88  md5_finish( &md5_ctx, md5sum );
89 
90  if( keylen <= 16 )
91  {
92  memcpy( key, md5sum, keylen );
93 
94  polarssl_zeroize( &md5_ctx, sizeof( md5_ctx ) );
95  polarssl_zeroize( md5sum, 16 );
96  return;
97  }
98 
99  memcpy( key, md5sum, 16 );
100 
101  /*
102  * key[16..23] = MD5(key[ 0..15] || pwd || IV])
103  */
104  md5_starts( &md5_ctx );
105  md5_update( &md5_ctx, md5sum, 16 );
106  md5_update( &md5_ctx, pwd, pwdlen );
107  md5_update( &md5_ctx, iv, 8 );
108  md5_finish( &md5_ctx, md5sum );
109 
110  use_len = 16;
111  if( keylen < 32 )
112  use_len = keylen - 16;
113 
114  memcpy( key + 16, md5sum, use_len );
115 
116  polarssl_zeroize( &md5_ctx, sizeof( md5_ctx ) );
117  polarssl_zeroize( md5sum, 16 );
118 }
119 
120 #if defined(POLARSSL_DES_C)
121 /*
122  * Decrypt with DES-CBC, using PBKDF1 for key derivation
123  */
124 static void pem_des_decrypt( unsigned char des_iv[8],
125  unsigned char *buf, size_t buflen,
126  const unsigned char *pwd, size_t pwdlen )
127 {
128  des_context des_ctx;
129  unsigned char des_key[8];
130 
131  pem_pbkdf1( des_key, 8, des_iv, pwd, pwdlen );
132 
133  des_setkey_dec( &des_ctx, des_key );
134  des_crypt_cbc( &des_ctx, DES_DECRYPT, buflen,
135  des_iv, buf, buf );
136 
137  polarssl_zeroize( &des_ctx, sizeof( des_ctx ) );
138  polarssl_zeroize( des_key, 8 );
139 }
140 
141 /*
142  * Decrypt with 3DES-CBC, using PBKDF1 for key derivation
143  */
144 static void pem_des3_decrypt( unsigned char des3_iv[8],
145  unsigned char *buf, size_t buflen,
146  const unsigned char *pwd, size_t pwdlen )
147 {
148  des3_context des3_ctx;
149  unsigned char des3_key[24];
150 
151  pem_pbkdf1( des3_key, 24, des3_iv, pwd, pwdlen );
152 
153  des3_set3key_dec( &des3_ctx, des3_key );
154  des3_crypt_cbc( &des3_ctx, DES_DECRYPT, buflen,
155  des3_iv, buf, buf );
156 
157  polarssl_zeroize( &des3_ctx, sizeof( des3_ctx ) );
158  polarssl_zeroize( des3_key, 24 );
159 }
160 #endif /* POLARSSL_DES_C */
161 
162 #if defined(POLARSSL_AES_C)
163 /*
164  * Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation
165  */
166 static void pem_aes_decrypt( unsigned char aes_iv[16], unsigned int keylen,
167  unsigned char *buf, size_t buflen,
168  const unsigned char *pwd, size_t pwdlen )
169 {
170  aes_context aes_ctx;
171  unsigned char aes_key[32];
172 
173  pem_pbkdf1( aes_key, keylen, aes_iv, pwd, pwdlen );
174 
175  aes_setkey_dec( &aes_ctx, aes_key, keylen * 8 );
176  aes_crypt_cbc( &aes_ctx, AES_DECRYPT, buflen,
177  aes_iv, buf, buf );
178 
179  polarssl_zeroize( &aes_ctx, sizeof( aes_ctx ) );
180  polarssl_zeroize( aes_key, keylen );
181 }
182 #endif /* POLARSSL_AES_C */
183 
184 #endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
185 
186 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 )
187 {
188  int ret, enc;
189  size_t len;
190  unsigned char *buf;
191  const unsigned char *s1, *s2, *end;
192 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
193  unsigned char pem_iv[16];
195 #else
196  ((void) pwd);
197  ((void) pwdlen);
198 #endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
199 
200  if( ctx == NULL )
202 
203  s1 = (unsigned char *) strstr( (const char *) data, header );
204 
205  if( s1 == NULL )
207 
208  s2 = (unsigned char *) strstr( (const char *) data, footer );
209 
210  if( s2 == NULL || s2 <= s1 )
212 
213  s1 += strlen( header );
214  if( *s1 == '\r' ) s1++;
215  if( *s1 == '\n' ) s1++;
217 
218  end = s2;
219  end += strlen( footer );
220  if( *end == '\r' ) end++;
221  if( *end == '\n' ) end++;
222  *use_len = end - data;
223 
224  enc = 0;
225 
226  if( memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 )
227  {
228 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
229  enc++;
230 
231  s1 += 22;
232  if( *s1 == '\r' ) s1++;
233  if( *s1 == '\n' ) s1++;
234  else return( POLARSSL_ERR_PEM_INVALID_DATA );
235 
236 
237 #if defined(POLARSSL_DES_C)
238  if( memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 )
239  {
241 
242  s1 += 23;
243  if( pem_get_iv( s1, pem_iv, 8 ) != 0 )
245 
246  s1 += 16;
247  }
248  else if( memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 )
249  {
250  enc_alg = POLARSSL_CIPHER_DES_CBC;
251 
252  s1 += 18;
253  if( pem_get_iv( s1, pem_iv, 8) != 0 )
255 
256  s1 += 16;
257  }
258 #endif /* POLARSSL_DES_C */
259 
260 #if defined(POLARSSL_AES_C)
261  if( memcmp( s1, "DEK-Info: AES-", 14 ) == 0 )
262  {
263  if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 )
264  enc_alg = POLARSSL_CIPHER_AES_128_CBC;
265  else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 )
266  enc_alg = POLARSSL_CIPHER_AES_192_CBC;
267  else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 )
268  enc_alg = POLARSSL_CIPHER_AES_256_CBC;
269  else
271 
272  s1 += 22;
273  if( pem_get_iv( s1, pem_iv, 16 ) != 0 )
275 
276  s1 += 32;
277  }
278 #endif /* POLARSSL_AES_C */
279 
280  if( enc_alg == POLARSSL_CIPHER_NONE )
282 
283  if( *s1 == '\r' ) s1++;
284  if( *s1 == '\n' ) s1++;
285  else return( POLARSSL_ERR_PEM_INVALID_DATA );
286 #else
288 #endif /* POLARSSL_MD5_C && (POLARSSL_AES_C || POLARSSL_DES_C) */
289  }
290 
291  len = 0;
292  ret = base64_decode( NULL, &len, s1, s2 - s1 );
293 
295  return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
296 
297  if( ( buf = (unsigned char *) malloc( len ) ) == NULL )
299 
300  if( ( ret = base64_decode( buf, &len, s1, s2 - s1 ) ) != 0 )
301  {
302  free( buf );
303  return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
304  }
305 
306  if( enc != 0 )
307  {
308 #if defined(POLARSSL_MD5_C) && (defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C))
309  if( pwd == NULL )
310  {
311  free( buf );
313  }
314 
315 #if defined(POLARSSL_DES_C)
316  if( enc_alg == POLARSSL_CIPHER_DES_EDE3_CBC )
317  pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen );
318  else if( enc_alg == POLARSSL_CIPHER_DES_CBC )
319  pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen );
320 #endif /* POLARSSL_DES_C */
321 
322 #if defined(POLARSSL_AES_C)
323  if( enc_alg == POLARSSL_CIPHER_AES_128_CBC )
324  pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen );
325  else if( enc_alg == POLARSSL_CIPHER_AES_192_CBC )
326  pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen );
327  else if( enc_alg == POLARSSL_CIPHER_AES_256_CBC )
328  pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen );
329 #endif /* POLARSSL_AES_C */
330 
331  if( buf[0] != 0x30 || buf[1] != 0x82 ||
332  buf[4] != 0x02 || buf[5] != 0x01 )
333  {
334  free( buf );
336  }
337 #else
338  free( buf );
340 #endif
341  }
342 
343  ctx->buf = buf;
344  ctx->buflen = len;
345 
346  return( 0 );
347 }
348 
349 void pem_free( pem_context *ctx )
350 {
351  if( ctx->buf )
352  free( ctx->buf );
353 
354  if( ctx->info )
355  free( ctx->info );
356 
357  polarssl_zeroize( ctx, sizeof( pem_context ) );
358 }
359 
360 #endif
unsigned char * info
Definition: pem.h:56
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
#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:42
AES context structure.
Definition: aes.h:54
Configuration options (set of defines)
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)
Read a buffer for PEM information and store the resulting data into the specified context buffers...
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:55
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't be empty.
Definition: pem.h:43
void pem_init(pem_context *ctx)
PEM context setup.
Privacy Enhanced Mail (PEM) decoding.
Triple-DES context structure.
Definition: des.h:65
cipher_type_t
Definition: cipher.h:59
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) ...
AES block cipher.
#define POLARSSL_ERR_PEM_PASSWORD_MISMATCH
Given private key password does not allow for correct decryption.
Definition: pem.h:44
void pem_free(pem_context *ctx)
PEM context memory freeing.
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:50
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.
PEM context structure.
Definition: pem.h:52
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
unsigned char * buf
Definition: pem.h:54
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
size_t buflen
Definition: pem.h:55
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 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