pgp-encode.c 9.47 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
/* pgp.c
 *
 * PGP related functions.
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2001, 2002 Niels Mller
 *  
 * The nettle library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * The nettle library 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 Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

26
#if HAVE_CONFIG_H
27
# include "config.h"
28 29 30 31 32 33
#endif

#include <assert.h>
#include <stdlib.h>
#include <string.h>

34 35 36 37 38 39
#include "pgp.h"

#include "base64.h"
#include "buffer.h"
#include "macros.h"

40 41 42 43 44
#if WITH_PUBLIC_KEY
# include "bignum.h"
# include "rsa.h"
#endif /* WITH_PUBLIC_KEY */

45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67
int
pgp_put_uint32(struct nettle_buffer *buffer, uint32_t i)
{
  uint8_t *p = nettle_buffer_space(buffer, 4);
  if (!p)
    return 0;
  
  WRITE_UINT32(p, i);
  return 1;
}

int
pgp_put_uint16(struct nettle_buffer *buffer, unsigned i)
{
  uint8_t *p = nettle_buffer_space(buffer, 2);
  if (!p)
    return 0;
  
  WRITE_UINT16(p, i);
  return 1;
}

int
68
pgp_put_mpi(struct nettle_buffer *buffer, const mpz_t x)
69 70 71 72 73 74 75 76 77 78 79 80 81 82 83
{
  unsigned bits = mpz_sizeinbase(x, 2);
  unsigned octets = (bits + 7) / 8;

  uint8_t *p;

  /* FIXME: What's the correct representation of zero? */
  if (!pgp_put_uint16(buffer, bits))
    return 0;
  
  p = nettle_buffer_space(buffer, octets);

  if (!p)
    return 0;
  
84
  nettle_mpz_get_str_256(x, octets, p);
85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209

  return 1;
}

int
pgp_put_string(struct nettle_buffer *buffer,
	       unsigned length,
	       const uint8_t *s)
{
  return nettle_buffer_write(buffer, length, s);
}

#if 0
static unsigned
length_field(unsigned length)
{
  if (length < PGP_LENGTH_TWO_OCTET)
    return 1;
  else if (length < PGP_LENGTH_FOUR_OCTETS)
    return 2;
  else return 4;
}
#endif

/*   bodyLen = ((1st_octet - 192) << 8) + (2nd_octet) + 192
 *   ==> bodyLen - 192 + 192 << 8 = (1st_octet << 8) + (2nd_octet) 
 */

#define LENGTH_TWO_OFFSET (192 * 255)

int
pgp_put_length(struct nettle_buffer *buffer,
	       unsigned length)
{
  if (length < PGP_LENGTH_TWO_OCTETS)
    return NETTLE_BUFFER_PUTC(buffer, length);

  else if (length < PGP_LENGTH_FOUR_OCTETS)
    return pgp_put_uint16(buffer, length + LENGTH_TWO_OFFSET);
  else
    return NETTLE_BUFFER_PUTC(buffer, 0xff) && pgp_put_uint32(buffer, length);
}

/* Uses the "new" packet format */
int
pgp_put_header(struct nettle_buffer *buffer,
	       unsigned tag, unsigned length)
{
  assert(tag < 0x40);

  return (NETTLE_BUFFER_PUTC(buffer, 0xC0 | tag)
	  && pgp_put_length(buffer, length));  
}

/* FIXME: Should we abort or return error if the length and the field
 * size don't match? */
void
pgp_put_header_length(struct nettle_buffer *buffer,
		      /* start of the header */
		      unsigned start,
		      unsigned field_size)
{
  unsigned length;
  switch (field_size)
    {
    case 1:
      length = buffer->size - (start + 2);
      assert(length < PGP_LENGTH_TWO_OCTETS);
      buffer->contents[start + 1] = length;
      break;
    case 2:
      length = buffer->size - (start + 3);
      assert(length < PGP_LENGTH_FOUR_OCTETS
	     && length >= PGP_LENGTH_TWO_OCTETS);
      WRITE_UINT16(buffer->contents + start + 1, length + LENGTH_TWO_OFFSET);
      break;
    case 4:
      length = buffer->size - (start + 5);
      WRITE_UINT32(buffer->contents + start + 2, length);
      break;
    default:
      abort();
    }
}

int
pgp_put_userid(struct nettle_buffer *buffer,
	       unsigned length,
	       const uint8_t *name)
{
  return (pgp_put_header(buffer, PGP_TAG_USERID, length)
	  && pgp_put_string(buffer, length, name));
}

unsigned
pgp_sub_packet_start(struct nettle_buffer *buffer)
{
  return nettle_buffer_space(buffer, 2) ? buffer->size : 0;
}

int
pgp_put_sub_packet(struct nettle_buffer *buffer,
		   unsigned type,
		   unsigned length,
		   const uint8_t *data)
{
  return (pgp_put_length(buffer, length + 1)
	  && NETTLE_BUFFER_PUTC(buffer, type)
	  && pgp_put_string(buffer, length, data));
}

void
pgp_sub_packet_end(struct nettle_buffer *buffer, unsigned start)
{
  unsigned length;
  
  assert(start >= 2);
  assert(start <= buffer->size);

  length = buffer->size - start;
  WRITE_UINT32(buffer->contents + start - 2, length);
}

#if WITH_PUBLIC_KEY
int
210 211
pgp_put_public_rsa_key(struct nettle_buffer *buffer,
		       const struct rsa_public_key *pub,
212 213 214 215 216 217 218 219
		       time_t timestamp)
{
  /* Public key packet, version 4 */
  unsigned start;
  unsigned length;

  /* Size of packet is 16 + the size of e and n */
  length = (4 * 4
220 221
	  + nettle_mpz_sizeinbase_256_u(pub->n)
	  + nettle_mpz_sizeinbase_256_u(pub->e));
222

223
  if (!pgp_put_header(buffer, PGP_TAG_PUBLIC_KEY, length))
224 225 226 227 228 229 230
    return 0;

  start = buffer->size;
  
  if (! (pgp_put_header(buffer, PGP_TAG_PUBLIC_KEY,
			/* Assume that we need two octets */
			PGP_LENGTH_TWO_OCTETS)
231 232 233 234 235
	 && pgp_put_uint32(buffer, 4)        /* Version */  
	 && pgp_put_uint32(buffer, timestamp)/* Time stamp */
	 && pgp_put_uint32(buffer, PGP_RSA)  /* Algorithm */
	 && pgp_put_mpi(buffer, pub->n)
	 && pgp_put_mpi(buffer, pub->e)) )
236 237 238 239 240 241 242 243 244
    return 0;

  assert(buffer->size == start + length);

  return 1;
}

int
pgp_put_rsa_sha1_signature(struct nettle_buffer *buffer,
245
			   const struct rsa_private_key *key,
246 247 248 249 250 251
			   const uint8_t *keyid,
			   unsigned type,
			   struct sha1_ctx *hash)
{
  unsigned signature_start = buffer->size;
  unsigned hash_end;
252
  unsigned sub_packet_start;
253 254 255 256 257 258 259 260 261 262 263 264 265 266
  uint8_t trailer[6];
  uint8_t digest16[2];
  mpz_t s;
  
  /* Signature packet. The packet could reasonably be both smaller and
   * larger than 192, so for simplicity we use the 4 octet header
   * form. */

  if (! (pgp_put_header(buffer, PGP_TAG_SIGNATURE, PGP_LENGTH_FOUR_OCTETS)
	 && NETTLE_BUFFER_PUTC(buffer, 4)  /* Version */
	 && NETTLE_BUFFER_PUTC(buffer, type)
	 /* Could also be PGP_RSA_SIGN */
	 && NETTLE_BUFFER_PUTC(buffer, PGP_RSA)
	 && NETTLE_BUFFER_PUTC(buffer, PGP_SHA1)
267
	 && pgp_put_uint16(buffer, 0)))  /* Hashed subpacket length */
268 269 270 271 272 273 274 275 276 277 278 279 280 281
    return 0;

  hash_end = buffer->size;

  sha1_update(hash,
	      hash_end - signature_start,
	      buffer->contents + signature_start);

  trailer[0] = 4; trailer[1] = 0xff;
  WRITE_UINT32(trailer + 2, buffer->size - signature_start);

  sha1_update(hash, sizeof(trailer), trailer);

  {
282 283
    struct sha1_ctx hcopy = *hash;
    uint8_t *p = nettle_buffer_space(buffer, 2);
284 285 286 287 288 289 290 291 292 293 294
    if (!p)
      return 0;
    
    sha1_digest(&hcopy, 2, p);
  }

  /* One "sub-packet" field with the issuer keyid */
  sub_packet_start = pgp_sub_packet_start(buffer);
  if (!sub_packet_start)
    return 0;

295 296 297 298 299
  if (pgp_put_sub_packet(buffer, PGP_SUBPACKET_ISSUER, 8, keyid))
    {
      pgp_sub_packet_end(buffer, sub_packet_start);
      return 0;
    }
300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343
    
  mpz_init(s);
  rsa_sha1_sign(key, hash, s);

  if (!pgp_put_mpi(buffer, s))
    {
      mpz_clear(s);
      return 0;
    }

  mpz_clear(s);
  pgp_put_header_length(buffer, signature_start, 4);

  return 1;
}
#endif /* WITH_PUBLIC_KEY */

#define CRC24_INIT 0x0b704ceL
#define CRC24_POLY 0x1864cfbL

uint32_t
pgp_crc24(unsigned length, const uint8_t *data)
{
  uint32_t crc = CRC24_INIT;

  unsigned i;
  for (i = 0; i<length; i++)
    {
      unsigned j;
      crc ^= ((unsigned) (data[i]) << 16);
      for (j = 0; j<8; j++)
	{
	  crc <<= 1;
	  if (crc & 0x1000000)
	    crc ^= CRC24_POLY;
	}
    }
  assert(crc < 0x1000000);
  return crc;
}


#define WRITE(buffer, s) (nettle_buffer_write(buffer, strlen((s)), (s)))

344 345 346
/* 15 base 64 groups data per line */
#define BINARY_PER_LINE 45
#define TEXT_PER_LINE BASE64_ENCODE_LENGTH(BINARY_PER_LINE)
347 348 349 350 351 352 353

int
pgp_armor(struct nettle_buffer *buffer,
	  const char *tag,
	  unsigned length,
	  const uint8_t *data)
{
354 355
  struct base64_encode_ctx ctx;
  
356
  unsigned crc = pgp_crc24(length, data);
357 358

  base64_encode_init(&ctx);
359 360 361 362 363 364 365 366 367 368
  
  if (! (WRITE(buffer, "BEGIN PGP ")
	 && WRITE(buffer, tag)
	 && WRITE(buffer, "\nComment: Nettle\n\n")))
    return 0;

  for (;
       length >= BINARY_PER_LINE;
       length -= BINARY_PER_LINE, data += BINARY_PER_LINE)
    {
369
      unsigned done;
370 371 372 373 374 375
      uint8_t *p
	= nettle_buffer_space(buffer, TEXT_PER_LINE);
      
      if (!p)
	return 0;

376 377
      done = base64_encode_update(&ctx, p, BINARY_PER_LINE, data);
      assert(done <= TEXT_PER_LINE);
378

379 380 381
      /* FIXME: Create some official way to do this */
      buffer->size -= (TEXT_PER_LINE - done);
      
382 383 384 385 386 387
      if (!NETTLE_BUFFER_PUTC(buffer, '\n'))
	return 0;
    }

  if (length)
    {
388 389 390 391
      unsigned text_size = BASE64_ENCODE_LENGTH(length)
	+ BASE64_ENCODE_FINAL_LENGTH;
      unsigned done;
      
392 393 394 395 396
      uint8_t *p
	= nettle_buffer_space(buffer, text_size);
      if (!p)
	return 0;

397 398 399 400 401 402
      done = base64_encode_update(&ctx, p, length, data);
      done += base64_encode_final(&ctx, p + done);

      /* FIXME: Create some official way to do this */
      buffer->size -= (text_size - done);
      
403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420
      if (!NETTLE_BUFFER_PUTC(buffer, '\n'))
	return 0;
    }
  /* Checksum */
  if (!NETTLE_BUFFER_PUTC(buffer, '='))
    return 0;

  {
    uint8_t *p = nettle_buffer_space(buffer, 4);
    if (!p)
      return 0;
    base64_encode_group(p, crc);
  }
  
  return (WRITE(buffer, "\nBEGIN PGP ")
	  && WRITE(buffer, tag)
	  && NETTLE_BUFFER_PUTC(buffer, '\n'));
}