src/libstrongswan/asn1/pem.c

   1 /*
   2  * Copyright (C) 2001-2004 Andreas Steffen, Zuercher Hochschule Winterthur
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License as published by the
   6  * Free Software Foundation; either version 2 of the License, or (at your
   7  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  11  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * for more details.
  13  */
  14
  15 #include <stdio.h>
  16 #include <stdlib.h>
  17 #include <unistd.h>
  18 #include <errno.h>
  19 #include <string.h>
  20 #include <stddef.h>
  21 #include <sys/types.h>
  22
  23 #include "asn1.h"
  24 #include "pem.h"
  25 #include "ttodata.h"
  26
  27 #include <utils/lexparser.h>
  28 #include <utils/logger_manager.h>
  29 #include <crypto/hashers/hasher.h>
  30 #include <crypto/crypters/crypter.h>
  31
  32 static logger_t *logger = NULL;
  33
  34 /**
  35  * initializes the PEM logger
  36  */
  37 static void pem_init_logger(void)
  38 {
  39         if (logger == NULL)
  40                 logger = logger_manager->get_logger(logger_manager, ASN1);
  41 }
  42
  43 /**
  44  * check the presence of a pattern in a character string
  45  */
  46 static bool present(const char* pattern, chunk_t* ch)
  47 {
  48         u_int pattern_len = strlen(pattern);
  49
  50         if (ch->len >= pattern_len && strncmp(ch->ptr, pattern, pattern_len) == 0)
  51         {
  52                 ch->ptr += pattern_len;
  53                 ch->len -= pattern_len;
  54                 return TRUE;
  55         }
  56         return FALSE;
  57 }
  58
  59 /**
  60  * find a boundary of the form -----tag name-----
  61  */
  62 static bool find_boundary(const char* tag, chunk_t *line)
  63 {
  64         chunk_t name = CHUNK_INITIALIZER;
  65
  66         if (!present("-----", line))
  67                 return FALSE;
  68         if (!present(tag, line))
  69                 return FALSE;
  70         if (*line->ptr != ' ')
  71                 return FALSE;
  72         line->ptr++;  line->len--;
  73
  74         /* extract name */
  75         name.ptr = line->ptr;
  76         while (line->len > 0)
  77         {
  78                 if (present("-----", line))
  79                 {
  80                         logger->log(logger, CONTROL|LEVEL2,
  81                                 "  -----%s %.*s-----", tag, (int)name.len, name.ptr);
  82                         return TRUE;
  83                 }
  84                 line->ptr++;  line->len--;  name.len++;
  85         }
  86         return FALSE;
  87 }
  88
  89 /*
  90  * decrypts a DES-EDE-CBC encrypted data block
  91  */
  92 static err_t pem_decrypt(chunk_t *blob, chunk_t *iv, char *passphrase)
  93 {
  94         hasher_t *hasher;
  95         crypter_t *crypter;
  96         chunk_t hash;
  97         chunk_t decrypted;
  98         chunk_t pass = {(char*)passphrase, strlen(passphrase)};
  99         chunk_t key = {alloca(24), 24};
 100         u_int8_t padding, *last_padding_pos, *first_padding_pos;
 101
 102         /* build key from passphrase and IV */
 103         hasher = hasher_create(HASH_MD5);
 104         hash.len = hasher->get_hash_size(hasher);
 105         hash.ptr = alloca(hash.len);
 106         hasher->get_hash(hasher, pass, NULL);
 107         hasher->get_hash(hasher, *iv, hash.ptr);
 108
 109         memcpy(key.ptr, hash.ptr, hash.len);
 110
 111         hasher->get_hash(hasher, hash, NULL);
 112         hasher->get_hash(hasher, pass, NULL);
 113         hasher->get_hash(hasher, *iv, hash.ptr);
 114
 115         memcpy(key.ptr + hash.len, hash.ptr, key.len - hash.len);
 116
 117         hasher->destroy(hasher);
 118
 119         /* decrypt blob */
 120         crypter = crypter_create(ENCR_3DES, 0);
 121         crypter->set_key(crypter, key);
 122         crypter->decrypt(crypter, *blob, *iv, &decrypted);
 123         memcpy(blob->ptr, decrypted.ptr, blob->len);
 124         chunk_free(&decrypted);
 125
 126         /* determine amount of padding */
 127         last_padding_pos = blob->ptr + blob->len - 1;
 128         padding = *last_padding_pos;
 129         first_padding_pos = (padding > blob->len) ? blob->ptr : last_padding_pos - padding;
 130
 131         /* check the padding pattern */
 132         while (--last_padding_pos > first_padding_pos)
 133         {
 134                 if (*last_padding_pos != padding)
 135                         return "invalid passphrase";
 136         }
 137         /* remove padding */
 138         blob->len -= padding;
 139         return NULL;
 140 }
 141
 142 /*  Converts a PEM encoded file into its binary form
 143  *
 144  *  RFC 1421 Privacy Enhancement for Electronic Mail, February 1993
 145  *  RFC 934 Message Encapsulation, January 1985
 146  */
 147 err_t pem_to_bin(chunk_t *blob, char *passphrase, bool *pgp)
 148 {
 149         typedef enum {
 150                 PEM_PRE    = 0,
 151                 PEM_MSG    = 1,
 152                 PEM_HEADER = 2,
 153                 PEM_BODY   = 3,
 154                 PEM_POST   = 4,
 155                 PEM_ABORT  = 5
 156         } state_t;
 157
 158         bool encrypted = FALSE;
 159
 160         state_t state  = PEM_PRE;
 161
 162         chunk_t src    = *blob;
 163         chunk_t dst    = *blob;
 164         chunk_t line   = CHUNK_INITIALIZER;
 165         chunk_t iv     = CHUNK_INITIALIZER;
 166
 167         u_char iv_buf[16]; /* MD5 digest size */
 168
 169         /* zero size of converted blob */
 170         dst.len = 0;
 171
 172         /* zero size of IV */
 173         iv.ptr = iv_buf;
 174         iv.len = 0;
 175
 176         pem_init_logger();
 177
 178         while (fetchline(&src, &line))
 179         {
 180                 if (state == PEM_PRE)
 181                 {
 182                         if (find_boundary("BEGIN", &line))
 183                         {
 184                                 state = PEM_MSG;
 185                         }
 186                         continue;
 187                 }
 188                 else
 189                 {
 190                         if (find_boundary("END", &line))
 191                         {
 192                                 state = PEM_POST;
 193                                 break;
 194                         }
 195                         if (state == PEM_MSG)
 196                         {
 197                                 state = (memchr(line.ptr, ':', line.len) == NULL) ? PEM_BODY : PEM_HEADER;
 198                         }
 199                         if (state == PEM_HEADER)
 200                         {
 201                                 chunk_t name  = CHUNK_INITIALIZER;
 202                                 chunk_t value = CHUNK_INITIALIZER;
 203
 204                                 /* an empty line separates HEADER and BODY */
 205                                 if (line.len == 0)
 206                                 {
 207                                         state = PEM_BODY;
 208                                         continue;
 209                                 }
 210
 211                                 /* we are looking for a parameter: value pair */
 212                                 logger->log(logger, CONTROL|LEVEL2, "  %.*s", (int)line.len, line.ptr);
 213                                 if (!extract_parameter_value(&name, &value, &line))
 214                                         continue;
 215
 216                                 if (match("Proc-Type", &name) && *value.ptr == '4')
 217                                         encrypted = TRUE;
 218                                 else if (match("DEK-Info", &name))
 219                                 {
 220                                         const char *ugh = NULL;
 221                                         size_t len = 0;
 222                                         chunk_t dek;
 223
 224                                         if (!extract_token(&dek, ',', &value))
 225                                                 dek = value;
 226
 227                                         /* we support DES-EDE3-CBC encrypted files, only */
 228                                         if (!match("DES-EDE3-CBC", &dek))
 229                                                 return "encryption algorithm not supported";
 230
 231                                         eat_whitespace(&value);
 232                                         ugh = ttodata(value.ptr, value.len, 16, iv.ptr, 16, &len);
 233                                         if (ugh)
 234                                                 return "error in IV";
 235
 236                                         iv.len = len;
 237                                 }
 238                         }
 239                         else /* state is PEM_BODY */
 240                         {
 241                                 const char *ugh = NULL;
 242                                 size_t len = 0;
 243                                 chunk_t data;
 244
 245                                 /* remove any trailing whitespace */
 246                                 if (!extract_token(&data ,' ', &line))
 247                                 {
 248                                         data = line;
 249                                 }
 250
 251                                 /* check for PGP armor checksum */
 252                                 if (*data.ptr == '=')
 253                                 {
 254                                         *pgp = TRUE;
 255                                         data.ptr++;
 256                                         data.len--;
 257                                         logger->log(logger, CONTROL|LEVEL2, "  Armor checksum: %.*s",
 258                                                                 (int)data.len, data.ptr);
 259                                 continue;
 260                                 }
 261
 262                                 ugh = ttodata(data.ptr, data.len, 64, dst.ptr, blob->len - dst.len, &len);
 263                                 if (ugh)
 264                                 {
 265                                         state = PEM_ABORT;
 266                                         break;
 267                                 }
 268                                 else
 269                                 {
 270                                         dst.ptr += len;
 271                                         dst.len += len;
 272                                 }
 273                         }
 274                 }
 275         }
 276         /* set length to size of binary blob */
 277         blob->len = dst.len;
 278
 279         if (state != PEM_POST)
 280                 return "file coded in unknown format, discarded";
 281
 282         return (encrypted)? pem_decrypt(blob, &iv, passphrase) : NULL;
 283 }
 284
 285 /* load a coded key or certificate file with autodetection
 286  * of binary DER or base64 PEM ASN.1 formats and armored PGP format
 287  */
 288 bool pem_asn1_load_file(const char *filename, char *passphrase,
 289                                                 const char *type, chunk_t *blob, bool *pgp)
 290 {
 291         err_t ugh = NULL;
 292
 293         FILE *fd = fopen(filename, "r");
 294
 295         pem_init_logger();
 296
 297         if (fd)
 298         {
 299                 int bytes;
 300                 fseek(fd, 0, SEEK_END );
 301                 blob->len = ftell(fd);
 302                 rewind(fd);
 303                 blob->ptr = malloc(blob->len);
 304                 bytes = fread(blob->ptr, 1, blob->len, fd);
 305                 fclose(fd);
 306                 logger->log(logger, CONTROL, "  loaded %s file '%s' (%d bytes)", type, filename, bytes);
 307
 308                 *pgp = FALSE;
 309
 310                 /* try DER format */
 311                 if (is_asn1(*blob))
 312                 {
 313                         logger->log(logger, CONTROL|LEVEL1, "  file coded in DER format");
 314                         return TRUE;
 315                 }
 316
 317                 /* try PEM format */
 318                 ugh = pem_to_bin(blob, passphrase, pgp);
 319
 320                 if (ugh == NULL)
 321                 {
 322                         if (*pgp)
 323                         {
 324                                 logger->log(logger, CONTROL|LEVEL1, "  file coded in armored PGP format");
 325                                 return TRUE;
 326                         }
 327                         if (is_asn1(*blob))
 328                         {
 329                                 logger->log(logger, CONTROL|LEVEL1, "  file coded in PEM format");
 330                                 return TRUE;
 331                         }
 332                         ugh = "file coded in unknown format, discarded";
 333                 }
 334
 335                 /* a conversion error has occured */
 336                 logger->log(logger, ERROR, "  %s", ugh);
 337                 chunk_free(blob);
 338         }
 339         else
 340         {
 341                 logger->log(logger, ERROR, "  could not open %s file '%s'", type, filename);
 342         }
 343         return FALSE;
 344 }