library/pem.c - security/mbedtls - Rivoreo Source Code Repositories

 /*
  *  Privacy Enhanced Mail (PEM) decoding
  *
  *  Copyright (C) 2006-2014, ARM Limited, All Rights Reserved
  *
  *  This file is part of mbed TLS (https://polarssl.org)
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
  *
  *  You should have received a copy of the GNU General Public License along
  *  with this program; if not, write to the Free Software Foundation, Inc.,
  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */

 #if !defined(POLARSSL_CONFIG_FILE)
 #include "polarssl/config.h"
 #else
 #include POLARSSL_CONFIG_FILE
 #endif

 #if defined(POLARSSL_PEM_PARSE_C) || defined(POLARSSL_PEM_WRITE_C)

 #include "polarssl/pem.h"
 #include "polarssl/base64.h"
 #include "polarssl/des.h"
 #include "polarssl/aes.h"
 #include "polarssl/md5.h"
 #include "polarssl/cipher.h"

 #include <string.h>

 #if defined(POLARSSL_PLATFORM_C)
 #include "polarssl/platform.h"
 #else
 #include <stdlib.h>
 #define polarssl_malloc     malloc
 #define polarssl_free       free
 #endif

 /* Implementation that should never be optimized out by the compiler */
 static void polarssl_zeroize( void *v, size_t n ) {
     volatile unsigned char *p = v; while( n-- ) *p++ = 0;
 }

 #if defined(POLARSSL_PEM_PARSE_C)
 void pem_init( pem_context *ctx )
 {
     memset( ctx, 0, sizeof( pem_context ) );
 }

 #if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) &&         \
     ( defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C) )
 /*
  * Read a 16-byte hex string and convert it to binary
  */
 static int pem_get_iv( const unsigned char *s, unsigned char *iv,
                        size_t iv_len )
 {
     size_t i, j, k;

     memset( iv, 0, iv_len );

     for( i = 0; i < iv_len * 2; i++, s++ )
     {
         if( *s >= '0' && *s <= '9' ) j = *s - '0'; else
         if( *s >= 'A' && *s <= 'F' ) j = *s - '7'; else
         if( *s >= 'a' && *s <= 'f' ) j = *s - 'W'; else
             return( POLARSSL_ERR_PEM_INVALID_ENC_IV );

         k = ( ( i & 1 ) != 0 ) ? j : j << 4;

         iv[i >> 1] = (unsigned char)( iv[i >> 1] | k );
     }

     return( 0 );
 }

 static void pem_pbkdf1( unsigned char *key, size_t keylen,
                         unsigned char *iv,
                         const unsigned char *pwd, size_t pwdlen )
 {
     md5_context md5_ctx;
     unsigned char md5sum[16];
     size_t use_len;

     md5_init( &md5_ctx );

     /*
      * key[ 0..15] = MD5(pwd || IV)
      */
     md5_starts( &md5_ctx );
     md5_update( &md5_ctx, pwd, pwdlen );
     md5_update( &md5_ctx, iv,  8 );
     md5_finish( &md5_ctx, md5sum );

     if( keylen <= 16 )
     {
         memcpy( key, md5sum, keylen );

         md5_free( &md5_ctx );
         polarssl_zeroize( md5sum, 16 );
         return;
     }

     memcpy( key, md5sum, 16 );

     /*
      * key[16..23] = MD5(key[ 0..15] || pwd || IV])
      */
     md5_starts( &md5_ctx );
     md5_update( &md5_ctx, md5sum,  16 );
     md5_update( &md5_ctx, pwd, pwdlen );
     md5_update( &md5_ctx, iv,  8 );
     md5_finish( &md5_ctx, md5sum );

     use_len = 16;
     if( keylen < 32 )
         use_len = keylen - 16;

     memcpy( key + 16, md5sum, use_len );

     md5_free( &md5_ctx );
     polarssl_zeroize( md5sum, 16 );
 }

 #if defined(POLARSSL_DES_C)
 /*
  * Decrypt with DES-CBC, using PBKDF1 for key derivation
  */
 static void pem_des_decrypt( unsigned char des_iv[8],
                                unsigned char *buf, size_t buflen,
                                const unsigned char *pwd, size_t pwdlen )
 {
     des_context des_ctx;
     unsigned char des_key[8];

     des_init( &des_ctx );

     pem_pbkdf1( des_key, 8, des_iv, pwd, pwdlen );

     des_setkey_dec( &des_ctx, des_key );
     des_crypt_cbc( &des_ctx, DES_DECRYPT, buflen,
                      des_iv, buf, buf );

     des_free( &des_ctx );
     polarssl_zeroize( des_key, 8 );
 }

 /*
  * Decrypt with 3DES-CBC, using PBKDF1 for key derivation
  */
 static void pem_des3_decrypt( unsigned char des3_iv[8],
                                unsigned char *buf, size_t buflen,
                                const unsigned char *pwd, size_t pwdlen )
 {
     des3_context des3_ctx;
     unsigned char des3_key[24];

     des3_init( &des3_ctx );

     pem_pbkdf1( des3_key, 24, des3_iv, pwd, pwdlen );

     des3_set3key_dec( &des3_ctx, des3_key );
     des3_crypt_cbc( &des3_ctx, DES_DECRYPT, buflen,
                      des3_iv, buf, buf );

     des3_free( &des3_ctx );
     polarssl_zeroize( des3_key, 24 );
 }
 #endif /* POLARSSL_DES_C */

 #if defined(POLARSSL_AES_C)
 /*
  * Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation
  */
 static void pem_aes_decrypt( unsigned char aes_iv[16], unsigned int keylen,
                                unsigned char *buf, size_t buflen,
                                const unsigned char *pwd, size_t pwdlen )
 {
     aes_context aes_ctx;
     unsigned char aes_key[32];

     aes_init( &aes_ctx );

     pem_pbkdf1( aes_key, keylen, aes_iv, pwd, pwdlen );

     aes_setkey_dec( &aes_ctx, aes_key, keylen * 8 );
     aes_crypt_cbc( &aes_ctx, AES_DECRYPT, buflen,
                      aes_iv, buf, buf );

     aes_free( &aes_ctx );
     polarssl_zeroize( aes_key, keylen );
 }
 #endif /* POLARSSL_AES_C */

 #endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
           ( POLARSSL_AES_C || POLARSSL_DES_C ) */

 int pem_read_buffer( pem_context *ctx, const char *header, const char *footer,
                      const unsigned char *data, const unsigned char *pwd,
                      size_t pwdlen, size_t *use_len )
 {
     int ret, enc;
     size_t len;
     unsigned char *buf;
     const unsigned char *s1, *s2, *end;
 #if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) &&         \
     ( defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C) )
     unsigned char pem_iv[16];
     cipher_type_t enc_alg = POLARSSL_CIPHER_NONE;
 #else
     ((void) pwd);
     ((void) pwdlen);
 #endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
           ( POLARSSL_AES_C || POLARSSL_DES_C ) */

     if( ctx == NULL )
         return( POLARSSL_ERR_PEM_BAD_INPUT_DATA );

     s1 = (unsigned char *) strstr( (const char *) data, header );

     if( s1 == NULL )
         return( POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT );

     s2 = (unsigned char *) strstr( (const char *) data, footer );

     if( s2 == NULL || s2 <= s1 )
         return( POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT );

     s1 += strlen( header );
     if( *s1 == '\r' ) s1++;
     if( *s1 == '\n' ) s1++;
     else return( POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT );

     end = s2;
     end += strlen( footer );
     if( *end == '\r' ) end++;
     if( *end == '\n' ) end++;
     *use_len = end - data;

     enc = 0;

     if( memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 )
     {
 #if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) &&         \
     ( defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C) )
         enc++;

         s1 += 22;
         if( *s1 == '\r' ) s1++;
         if( *s1 == '\n' ) s1++;
         else return( POLARSSL_ERR_PEM_INVALID_DATA );


 #if defined(POLARSSL_DES_C)
         if( memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 )
         {
             enc_alg = POLARSSL_CIPHER_DES_EDE3_CBC;

             s1 += 23;
             if( pem_get_iv( s1, pem_iv, 8 ) != 0 )
                 return( POLARSSL_ERR_PEM_INVALID_ENC_IV );

             s1 += 16;
         }
         else if( memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 )
         {
             enc_alg = POLARSSL_CIPHER_DES_CBC;

             s1 += 18;
             if( pem_get_iv( s1, pem_iv, 8) != 0 )
                 return( POLARSSL_ERR_PEM_INVALID_ENC_IV );

             s1 += 16;
         }
 #endif /* POLARSSL_DES_C */

 #if defined(POLARSSL_AES_C)
         if( memcmp( s1, "DEK-Info: AES-", 14 ) == 0 )
         {
             if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 )
                 enc_alg = POLARSSL_CIPHER_AES_128_CBC;
             else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 )
                 enc_alg = POLARSSL_CIPHER_AES_192_CBC;
             else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 )
                 enc_alg = POLARSSL_CIPHER_AES_256_CBC;
             else
                 return( POLARSSL_ERR_PEM_UNKNOWN_ENC_ALG );

             s1 += 22;
             if( pem_get_iv( s1, pem_iv, 16 ) != 0 )
                 return( POLARSSL_ERR_PEM_INVALID_ENC_IV );

             s1 += 32;
         }
 #endif /* POLARSSL_AES_C */

         if( enc_alg == POLARSSL_CIPHER_NONE )
             return( POLARSSL_ERR_PEM_UNKNOWN_ENC_ALG );

         if( *s1 == '\r' ) s1++;
         if( *s1 == '\n' ) s1++;
         else return( POLARSSL_ERR_PEM_INVALID_DATA );
 #else
         return( POLARSSL_ERR_PEM_FEATURE_UNAVAILABLE );
 #endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
           ( POLARSSL_AES_C || POLARSSL_DES_C ) */
     }

     len = 0;
     ret = base64_decode( NULL, &len, s1, s2 - s1 );

     if( ret == POLARSSL_ERR_BASE64_INVALID_CHARACTER )
         return( POLARSSL_ERR_PEM_INVALID_DATA + ret );

     if( ( buf = (unsigned char *) polarssl_malloc( len ) ) == NULL )
         return( POLARSSL_ERR_PEM_MALLOC_FAILED );

     if( ( ret = base64_decode( buf, &len, s1, s2 - s1 ) ) != 0 )
     {
         polarssl_free( buf );
         return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
     }

     if( enc != 0 )
     {
 #if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) &&         \
     ( defined(POLARSSL_DES_C) || defined(POLARSSL_AES_C) )
         if( pwd == NULL )
         {
             polarssl_free( buf );
             return( POLARSSL_ERR_PEM_PASSWORD_REQUIRED );
         }

 #if defined(POLARSSL_DES_C)
         if( enc_alg == POLARSSL_CIPHER_DES_EDE3_CBC )
             pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen );
         else if( enc_alg == POLARSSL_CIPHER_DES_CBC )
             pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen );
 #endif /* POLARSSL_DES_C */

 #if defined(POLARSSL_AES_C)
         if( enc_alg == POLARSSL_CIPHER_AES_128_CBC )
             pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen );
         else if( enc_alg == POLARSSL_CIPHER_AES_192_CBC )
             pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen );
         else if( enc_alg == POLARSSL_CIPHER_AES_256_CBC )
             pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen );
 #endif /* POLARSSL_AES_C */

         /*
          * The result will be ASN.1 starting with a SEQUENCE tag, with 1 to 3
          * length bytes (allow 4 to be sure) in all known use cases.
          *
          * Use that as heurisitic to try detecting password mismatchs.
          */
         if( len <= 2 || buf[0] != 0x30 || buf[1] > 0x83 )
         {
             polarssl_free( buf );
             return( POLARSSL_ERR_PEM_PASSWORD_MISMATCH );
         }
 #else
         polarssl_free( buf );
         return( POLARSSL_ERR_PEM_FEATURE_UNAVAILABLE );
 #endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
           ( POLARSSL_AES_C || POLARSSL_DES_C ) */
     }

     ctx->buf = buf;
     ctx->buflen = len;

     return( 0 );
 }

 void pem_free( pem_context *ctx )
 {
     polarssl_free( ctx->buf );
     polarssl_free( ctx->info );

     polarssl_zeroize( ctx, sizeof( pem_context ) );
 }
 #endif /* POLARSSL_PEM_PARSE_C */

 #if defined(POLARSSL_PEM_WRITE_C)
 int pem_write_buffer( const char *header, const char *footer,
                       const unsigned char *der_data, size_t der_len,
                       unsigned char *buf, size_t buf_len, size_t *olen )
 {
     int ret;
     unsigned char *encode_buf, *c, *p = buf;
     size_t len = 0, use_len = 0, add_len = 0;

     base64_encode( NULL, &use_len, der_data, der_len );
     add_len = strlen( header ) + strlen( footer ) + ( use_len / 64 ) + 1;

     if( use_len + add_len > buf_len )
     {
         *olen = use_len + add_len;
         return( POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL );
     }

     if( ( encode_buf = polarssl_malloc( use_len ) ) == NULL )
         return( POLARSSL_ERR_PEM_MALLOC_FAILED );

     if( ( ret = base64_encode( encode_buf, &use_len, der_data,
                                der_len ) ) != 0 )
     {
         polarssl_free( encode_buf );
         return( ret );
     }

     memcpy( p, header, strlen( header ) );
     p += strlen( header );
     c = encode_buf;

     while( use_len )
     {
         len = ( use_len > 64 ) ? 64 : use_len;
         memcpy( p, c, len );
         use_len -= len;
         p += len;
         c += len;
         *p++ = '\n';
     }

     memcpy( p, footer, strlen( footer ) );
     p += strlen( footer );

     *p++ = '\0';
     *olen = p - buf;

     polarssl_free( encode_buf );
     return( 0 );
 }
 #endif /* POLARSSL_PEM_WRITE_C */
 #endif /* POLARSSL_PEM_PARSE_C || POLARSSL_PEM_WRITE_C */
	/*
	* Privacy Enhanced Mail (PEM) decoding
	*
	* Copyright (C) 2006-2014, ARM Limited, All Rights Reserved
	*
	* This file is part of mbed TLS (https://polarssl.org)
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License along
	* with this program; if not, write to the Free Software Foundation, Inc.,
	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
	*/

	#if !defined(POLARSSL_CONFIG_FILE)
	#include "polarssl/config.h"
	#else
	#include POLARSSL_CONFIG_FILE
	#endif

	#if defined(POLARSSL_PEM_PARSE_C) \|\| defined(POLARSSL_PEM_WRITE_C)

	#include "polarssl/pem.h"
	#include "polarssl/base64.h"
	#include "polarssl/des.h"
	#include "polarssl/aes.h"
	#include "polarssl/md5.h"
	#include "polarssl/cipher.h"

	#include <string.h>

	#if defined(POLARSSL_PLATFORM_C)
	#include "polarssl/platform.h"
	#else
	#include <stdlib.h>
	#define polarssl_malloc malloc
	#define polarssl_free free
	#endif

	/* Implementation that should never be optimized out by the compiler */
	static void polarssl_zeroize( void *v, size_t n ) {
	volatile unsigned char p = v; while( n-- ) p++ = 0;
	}

	#if defined(POLARSSL_PEM_PARSE_C)
	void pem_init( pem_context *ctx )
	{
	memset( ctx, 0, sizeof( pem_context ) );
	}

	#if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) && \
	( defined(POLARSSL_DES_C) \|\| defined(POLARSSL_AES_C) )
	/*
	* Read a 16-byte hex string and convert it to binary
	*/
	static int pem_get_iv( const unsigned char s, unsigned char iv,
	size_t iv_len )
	{
	size_t i, j, k;

	memset( iv, 0, iv_len );

	for( i = 0; i < iv_len * 2; i++, s++ )
	{
	if( s >= '0' && s <= '9' ) j = *s - '0'; else
	if( s >= 'A' && s <= 'F' ) j = *s - '7'; else
	if( s >= 'a' && s <= 'f' ) j = *s - 'W'; else
	return( POLARSSL_ERR_PEM_INVALID_ENC_IV );

	k = ( ( i & 1 ) != 0 ) ? j : j << 4;

	iv[i >> 1] = (unsigned char)( iv[i >> 1] \| k );
	}

	return( 0 );
	}

	static void pem_pbkdf1( unsigned char *key, size_t keylen,
	unsigned char *iv,
	const unsigned char *pwd, size_t pwdlen )
	{
	md5_context md5_ctx;
	unsigned char md5sum[16];
	size_t use_len;

	md5_init( &md5_ctx );

	/*
	* key[ 0..15] = MD5(pwd \|\| IV)
	*/
	md5_starts( &md5_ctx );
	md5_update( &md5_ctx, pwd, pwdlen );
	md5_update( &md5_ctx, iv, 8 );
	md5_finish( &md5_ctx, md5sum );

	if( keylen <= 16 )
	{
	memcpy( key, md5sum, keylen );

	md5_free( &md5_ctx );
	polarssl_zeroize( md5sum, 16 );
	return;
	}

	memcpy( key, md5sum, 16 );

	/*
	* key[16..23] = MD5(key[ 0..15] \|\| pwd \|\| IV])
	*/
	md5_starts( &md5_ctx );
	md5_update( &md5_ctx, md5sum, 16 );
	md5_update( &md5_ctx, pwd, pwdlen );
	md5_update( &md5_ctx, iv, 8 );
	md5_finish( &md5_ctx, md5sum );

	use_len = 16;
	if( keylen < 32 )
	use_len = keylen - 16;

	memcpy( key + 16, md5sum, use_len );

	md5_free( &md5_ctx );
	polarssl_zeroize( md5sum, 16 );
	}

	#if defined(POLARSSL_DES_C)
	/*
	* Decrypt with DES-CBC, using PBKDF1 for key derivation
	*/
	static void pem_des_decrypt( unsigned char des_iv[8],
	unsigned char *buf, size_t buflen,
	const unsigned char *pwd, size_t pwdlen )
	{
	des_context des_ctx;
	unsigned char des_key[8];

	des_init( &des_ctx );

	pem_pbkdf1( des_key, 8, des_iv, pwd, pwdlen );

	des_setkey_dec( &des_ctx, des_key );
	des_crypt_cbc( &des_ctx, DES_DECRYPT, buflen,
	des_iv, buf, buf );

	des_free( &des_ctx );
	polarssl_zeroize( des_key, 8 );
	}

	/*
	* Decrypt with 3DES-CBC, using PBKDF1 for key derivation
	*/
	static void pem_des3_decrypt( unsigned char des3_iv[8],
	unsigned char *buf, size_t buflen,
	const unsigned char *pwd, size_t pwdlen )
	{
	des3_context des3_ctx;
	unsigned char des3_key[24];

	des3_init( &des3_ctx );

	pem_pbkdf1( des3_key, 24, des3_iv, pwd, pwdlen );

	des3_set3key_dec( &des3_ctx, des3_key );
	des3_crypt_cbc( &des3_ctx, DES_DECRYPT, buflen,
	des3_iv, buf, buf );

	des3_free( &des3_ctx );
	polarssl_zeroize( des3_key, 24 );
	}
	#endif /* POLARSSL_DES_C */

	#if defined(POLARSSL_AES_C)
	/*
	* Decrypt with AES-XXX-CBC, using PBKDF1 for key derivation
	*/
	static void pem_aes_decrypt( unsigned char aes_iv[16], unsigned int keylen,
	unsigned char *buf, size_t buflen,
	const unsigned char *pwd, size_t pwdlen )
	{
	aes_context aes_ctx;
	unsigned char aes_key[32];

	aes_init( &aes_ctx );

	pem_pbkdf1( aes_key, keylen, aes_iv, pwd, pwdlen );

	aes_setkey_dec( &aes_ctx, aes_key, keylen * 8 );
	aes_crypt_cbc( &aes_ctx, AES_DECRYPT, buflen,
	aes_iv, buf, buf );

	aes_free( &aes_ctx );
	polarssl_zeroize( aes_key, keylen );
	}
	#endif /* POLARSSL_AES_C */

	#endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
	( POLARSSL_AES_C \|\| POLARSSL_DES_C ) */

	int pem_read_buffer( pem_context ctx, const char header, const char *footer,
	const unsigned char data, const unsigned char pwd,
	size_t pwdlen, size_t *use_len )
	{
	int ret, enc;
	size_t len;
	unsigned char *buf;
	const unsigned char s1, s2, *end;
	#if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) && \
	( defined(POLARSSL_DES_C) \|\| defined(POLARSSL_AES_C) )
	unsigned char pem_iv[16];
	cipher_type_t enc_alg = POLARSSL_CIPHER_NONE;
	#else
	((void) pwd);
	((void) pwdlen);
	#endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
	( POLARSSL_AES_C \|\| POLARSSL_DES_C ) */

	if( ctx == NULL )
	return( POLARSSL_ERR_PEM_BAD_INPUT_DATA );

	s1 = (unsigned char ) strstr( (const char ) data, header );

	if( s1 == NULL )
	return( POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT );

	s2 = (unsigned char ) strstr( (const char ) data, footer );

	if( s2 == NULL \|\| s2 <= s1 )
	return( POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT );

	s1 += strlen( header );
	if( *s1 == '\r' ) s1++;
	if( *s1 == '\n' ) s1++;
	else return( POLARSSL_ERR_PEM_NO_HEADER_FOOTER_PRESENT );

	end = s2;
	end += strlen( footer );
	if( *end == '\r' ) end++;
	if( *end == '\n' ) end++;
	*use_len = end - data;

	enc = 0;

	if( memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 )
	{
	#if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) && \
	( defined(POLARSSL_DES_C) \|\| defined(POLARSSL_AES_C) )
	enc++;

	s1 += 22;
	if( *s1 == '\r' ) s1++;
	if( *s1 == '\n' ) s1++;
	else return( POLARSSL_ERR_PEM_INVALID_DATA );


	#if defined(POLARSSL_DES_C)
	if( memcmp( s1, "DEK-Info: DES-EDE3-CBC,", 23 ) == 0 )
	{
	enc_alg = POLARSSL_CIPHER_DES_EDE3_CBC;

	s1 += 23;
	if( pem_get_iv( s1, pem_iv, 8 ) != 0 )
	return( POLARSSL_ERR_PEM_INVALID_ENC_IV );

	s1 += 16;
	}
	else if( memcmp( s1, "DEK-Info: DES-CBC,", 18 ) == 0 )
	{
	enc_alg = POLARSSL_CIPHER_DES_CBC;

	s1 += 18;
	if( pem_get_iv( s1, pem_iv, 8) != 0 )
	return( POLARSSL_ERR_PEM_INVALID_ENC_IV );

	s1 += 16;
	}
	#endif /* POLARSSL_DES_C */

	#if defined(POLARSSL_AES_C)
	if( memcmp( s1, "DEK-Info: AES-", 14 ) == 0 )
	{
	if( memcmp( s1, "DEK-Info: AES-128-CBC,", 22 ) == 0 )
	enc_alg = POLARSSL_CIPHER_AES_128_CBC;
	else if( memcmp( s1, "DEK-Info: AES-192-CBC,", 22 ) == 0 )
	enc_alg = POLARSSL_CIPHER_AES_192_CBC;
	else if( memcmp( s1, "DEK-Info: AES-256-CBC,", 22 ) == 0 )
	enc_alg = POLARSSL_CIPHER_AES_256_CBC;
	else
	return( POLARSSL_ERR_PEM_UNKNOWN_ENC_ALG );

	s1 += 22;
	if( pem_get_iv( s1, pem_iv, 16 ) != 0 )
	return( POLARSSL_ERR_PEM_INVALID_ENC_IV );

	s1 += 32;
	}
	#endif /* POLARSSL_AES_C */

	if( enc_alg == POLARSSL_CIPHER_NONE )
	return( POLARSSL_ERR_PEM_UNKNOWN_ENC_ALG );

	if( *s1 == '\r' ) s1++;
	if( *s1 == '\n' ) s1++;
	else return( POLARSSL_ERR_PEM_INVALID_DATA );
	#else
	return( POLARSSL_ERR_PEM_FEATURE_UNAVAILABLE );
	#endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
	( POLARSSL_AES_C \|\| POLARSSL_DES_C ) */
	}

	len = 0;
	ret = base64_decode( NULL, &len, s1, s2 - s1 );

	if( ret == POLARSSL_ERR_BASE64_INVALID_CHARACTER )
	return( POLARSSL_ERR_PEM_INVALID_DATA + ret );

	if( ( buf = (unsigned char *) polarssl_malloc( len ) ) == NULL )
	return( POLARSSL_ERR_PEM_MALLOC_FAILED );

	if( ( ret = base64_decode( buf, &len, s1, s2 - s1 ) ) != 0 )
	{
	polarssl_free( buf );
	return( POLARSSL_ERR_PEM_INVALID_DATA + ret );
	}

	if( enc != 0 )
	{
	#if defined(POLARSSL_MD5_C) && defined(POLARSSL_CIPHER_MODE_CBC) && \
	( defined(POLARSSL_DES_C) \|\| defined(POLARSSL_AES_C) )
	if( pwd == NULL )
	{
	polarssl_free( buf );
	return( POLARSSL_ERR_PEM_PASSWORD_REQUIRED );
	}

	#if defined(POLARSSL_DES_C)
	if( enc_alg == POLARSSL_CIPHER_DES_EDE3_CBC )
	pem_des3_decrypt( pem_iv, buf, len, pwd, pwdlen );
	else if( enc_alg == POLARSSL_CIPHER_DES_CBC )
	pem_des_decrypt( pem_iv, buf, len, pwd, pwdlen );
	#endif /* POLARSSL_DES_C */

	#if defined(POLARSSL_AES_C)
	if( enc_alg == POLARSSL_CIPHER_AES_128_CBC )
	pem_aes_decrypt( pem_iv, 16, buf, len, pwd, pwdlen );
	else if( enc_alg == POLARSSL_CIPHER_AES_192_CBC )
	pem_aes_decrypt( pem_iv, 24, buf, len, pwd, pwdlen );
	else if( enc_alg == POLARSSL_CIPHER_AES_256_CBC )
	pem_aes_decrypt( pem_iv, 32, buf, len, pwd, pwdlen );
	#endif /* POLARSSL_AES_C */

	/*
	* The result will be ASN.1 starting with a SEQUENCE tag, with 1 to 3
	* length bytes (allow 4 to be sure) in all known use cases.
	*
	* Use that as heurisitic to try detecting password mismatchs.
	*/
	if( len <= 2 \|\| buf[0] != 0x30 \|\| buf[1] > 0x83 )
	{
	polarssl_free( buf );
	return( POLARSSL_ERR_PEM_PASSWORD_MISMATCH );
	}
	#else
	polarssl_free( buf );
	return( POLARSSL_ERR_PEM_FEATURE_UNAVAILABLE );
	#endif /* POLARSSL_MD5_C && POLARSSL_CIPHER_MODE_CBC &&
	( POLARSSL_AES_C \|\| POLARSSL_DES_C ) */
	}

	ctx->buf = buf;
	ctx->buflen = len;

	return( 0 );
	}

	void pem_free( pem_context *ctx )
	{
	polarssl_free( ctx->buf );
	polarssl_free( ctx->info );

	polarssl_zeroize( ctx, sizeof( pem_context ) );
	}
	#endif /* POLARSSL_PEM_PARSE_C */

	#if defined(POLARSSL_PEM_WRITE_C)
	int pem_write_buffer( const char header, const char footer,
	const unsigned char *der_data, size_t der_len,
	unsigned char buf, size_t buf_len, size_t olen )
	{
	int ret;
	unsigned char encode_buf, c, *p = buf;
	size_t len = 0, use_len = 0, add_len = 0;

	base64_encode( NULL, &use_len, der_data, der_len );
	add_len = strlen( header ) + strlen( footer ) + ( use_len / 64 ) + 1;

	if( use_len + add_len > buf_len )
	{
	*olen = use_len + add_len;
	return( POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL );
	}

	if( ( encode_buf = polarssl_malloc( use_len ) ) == NULL )
	return( POLARSSL_ERR_PEM_MALLOC_FAILED );

	if( ( ret = base64_encode( encode_buf, &use_len, der_data,
	der_len ) ) != 0 )
	{
	polarssl_free( encode_buf );
	return( ret );
	}

	memcpy( p, header, strlen( header ) );
	p += strlen( header );
	c = encode_buf;

	while( use_len )
	{
	len = ( use_len > 64 ) ? 64 : use_len;
	memcpy( p, c, len );
	use_len -= len;
	p += len;
	c += len;
	*p++ = '\n';
	}

	memcpy( p, footer, strlen( footer ) );
	p += strlen( footer );

	*p++ = '\0';
	*olen = p - buf;

	polarssl_free( encode_buf );
	return( 0 );
	}
	#endif /* POLARSSL_PEM_WRITE_C */
	#endif /* POLARSSL_PEM_PARSE_C \|\| POLARSSL_PEM_WRITE_C */