src/libstrongswan/plugins/pem/pem_encoder.c

   1 /*
   2  * Copyright (C) 2010 Andreas Steffen
   3  * Hochschule fuer Technik Rapperswil
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License as published by the
   7  * Free Software Foundation; either version 2 of the License, or (at your
   8  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  12  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * for more details.
  14  */
  15
  16 #include "pem_encoder.h"
  17
  18 #define BYTES_PER_LINE  48
  19
  20 /**
  21  * See header.
  22  */
  23 bool pem_encoder_encode(key_encoding_type_t type, chunk_t *encoding,
  24                                                 va_list args)
  25 {
  26         chunk_t asn1;
  27         char *label;
  28         u_char *pos;
  29         size_t len, written, pem_chars, pem_lines;
  30
  31         switch (type)
  32         {
  33                 case KEY_PUB_PEM:
  34                         if (key_encoding_args(args, KEY_PART_RSA_PUB_ASN1_DER,
  35                                                                    &asn1, KEY_PART_END) ||
  36                                 key_encoding_args(args, KEY_PART_ECDSA_PUB_ASN1_DER,
  37                                                                    &asn1, KEY_PART_END))
  38                         {
  39                                 label ="PUBLIC KEY";
  40                                 break;
  41                         }
  42                         return FALSE;
  43                 case KEY_PRIV_PEM:
  44                         if (key_encoding_args(args, KEY_PART_RSA_PRIV_ASN1_DER,
  45                                                                    &asn1, KEY_PART_END))
  46                         {
  47                                 label ="RSA PRIVATE KEY";
  48                                 break;
  49                         }
  50                         if (key_encoding_args(args, KEY_PART_ECDSA_PRIV_ASN1_DER,
  51                                                                    &asn1, KEY_PART_END))
  52                         {
  53                                 label ="EC PRIVATE KEY";
  54                                 break;
  55                         }
  56                         return FALSE;
  57                 default:
  58                         return FALSE;
  59         }
  60
  61         /* compute and allocate maximum size of PEM object */
  62         pem_chars = 4*(asn1.len + 2)/3;
  63         pem_lines = (asn1.len + BYTES_PER_LINE - 1) / BYTES_PER_LINE;
  64         *encoding = chunk_alloc(5 + 2*(6 + strlen(label) + 6) + 3 + pem_chars + pem_lines);
  65         pos = encoding->ptr;
  66         len = encoding->len;
  67
  68         /* write PEM header */
  69         written = snprintf(pos, len, "-----BEGIN %s-----\n", label);
  70         pos += written;
  71         len -= written;
  72
  73         /* write PEM body */
  74         while (pem_lines--)
  75         {
  76                 chunk_t asn1_line, pem_line;
  77
  78                 asn1_line = chunk_create(asn1.ptr, min(asn1.len, BYTES_PER_LINE));
  79                 asn1.ptr += asn1_line.len;
  80                 asn1.len -= asn1_line.len;
  81                 pem_line =  chunk_to_base64(asn1_line, pos);
  82                 pos += pem_line.len;
  83                 len -= pem_line.len;
  84                 *pos = '\n';
  85                 pos++;
  86                 len--;
  87         }
  88
  89         /* write PEM trailer */
  90         written = snprintf(pos, len, "-----END %s-----", label);
  91         pos += written;
  92         len -= written;
  93
  94         /* replace termination null character with newline */
  95         *pos = '\n';
  96         pos++;
  97         len--;
  98
  99         /* compute effective length of PEM object */
 100         encoding->len = pos - encoding->ptr;
 101         return TRUE;
 102 }
 103