pgp-encode.c 9.57 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 26 27 28 29 30 31 32
/* pgp-encode.c

   PGP related functions.

   Copyright (C) 2001, 2002 Niels Möller

   This file is part of GNU Nettle.

   GNU Nettle is free software: you can redistribute it and/or
   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free
       Software Foundation; either version 3 of the License, or (at your
       option) any later version.

   or

     * 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.

   or both in parallel, as here.

   GNU Nettle 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 copies of the GNU General Public License and
   the GNU Lesser General Public License along with this program.  If
   not, see http://www.gnu.org/licenses/.
*/
33

34
#if HAVE_CONFIG_H
35
# include "config.h"
36 37 38 39 40 41
#endif

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

42
#include "pgp.h"
43 44 45 46

#include "base64.h"
#include "buffer.h"
#include "macros.h"
47
#include "rsa.h"
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71

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
72
pgp_put_mpi(struct nettle_buffer *buffer, const mpz_t x)
73 74 75 76 77 78 79 80 81 82 83 84 85 86 87
{
  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;
  
88
  nettle_mpz_get_str_256(octets, p, x);
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212

  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);
}

int
213 214
pgp_put_public_rsa_key(struct nettle_buffer *buffer,
		       const struct rsa_public_key *pub,
215 216 217 218 219 220 221 222
		       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
223 224
	  + nettle_mpz_sizeinbase_256_u(pub->n)
	  + nettle_mpz_sizeinbase_256_u(pub->e));
225

226
  if (!pgp_put_header(buffer, PGP_TAG_PUBLIC_KEY, length))
227 228 229 230 231 232 233
    return 0;

  start = buffer->size;
  
  if (! (pgp_put_header(buffer, PGP_TAG_PUBLIC_KEY,
			/* Assume that we need two octets */
			PGP_LENGTH_TWO_OCTETS)
234 235 236 237 238
	 && 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)) )
239 240 241 242 243 244 245 246 247
    return 0;

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

  return 1;
}

int
pgp_put_rsa_sha1_signature(struct nettle_buffer *buffer,
248
			   const struct rsa_private_key *key,
249 250 251 252 253 254
			   const uint8_t *keyid,
			   unsigned type,
			   struct sha1_ctx *hash)
{
  unsigned signature_start = buffer->size;
  unsigned hash_end;
255
  unsigned sub_packet_start;
256 257 258 259 260 261 262 263 264 265 266 267 268
  uint8_t trailer[6];
  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)
269
	 && pgp_put_uint16(buffer, 0)))  /* Hashed subpacket length */
270 271 272 273 274 275 276 277 278 279 280 281 282 283
    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);

  {
284 285
    struct sha1_ctx hcopy = *hash;
    uint8_t *p = nettle_buffer_space(buffer, 2);
286 287 288 289 290 291 292 293 294 295 296
    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;

297
  if (pgp_put_sub_packet(buffer, PGP_SUBPACKET_ISSUER_KEY_ID, 8, keyid))
298 299 300 301
    {
      pgp_sub_packet_end(buffer, sub_packet_start);
      return 0;
    }
302 303
    
  mpz_init(s);
304 305
  if (!(rsa_sha1_sign(key, hash, s)
	&& pgp_put_mpi(buffer, s)))
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
    {
      mpz_clear(s);
      return 0;
    }

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

  return 1;
}

#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;
}


342 343 344 345 346
static int
write_string (struct nettle_buffer *buffer, const char *s)
{
  return nettle_buffer_write(buffer, strlen((s)), (const uint8_t *) (s));
}
347

348 349 350
/* 15 base 64 groups data per line */
#define BINARY_PER_LINE 45
#define TEXT_PER_LINE BASE64_ENCODE_LENGTH(BINARY_PER_LINE)
351 352 353 354 355 356 357

int
pgp_armor(struct nettle_buffer *buffer,
	  const char *tag,
	  unsigned length,
	  const uint8_t *data)
{
358 359
  struct base64_encode_ctx ctx;
  
360
  unsigned crc = pgp_crc24(length, data);
361 362

  base64_encode_init(&ctx);
363
  
364 365 366
  if (! (write_string(buffer, "BEGIN PGP ")
	 && write_string(buffer, tag)
	 && write_string(buffer, "\nComment: Nettle\n\n")))
367 368 369 370 371 372
    return 0;

  for (;
       length >= BINARY_PER_LINE;
       length -= BINARY_PER_LINE, data += BINARY_PER_LINE)
    {
373
      unsigned done;
374 375 376 377 378 379
      uint8_t *p
	= nettle_buffer_space(buffer, TEXT_PER_LINE);
      
      if (!p)
	return 0;

380 381
      done = base64_encode_update(&ctx, p, BINARY_PER_LINE, data);
      assert(done <= TEXT_PER_LINE);
382

383 384 385
      /* FIXME: Create some official way to do this */
      buffer->size -= (TEXT_PER_LINE - done);
      
386 387 388 389 390 391
      if (!NETTLE_BUFFER_PUTC(buffer, '\n'))
	return 0;
    }

  if (length)
    {
392 393 394 395
      unsigned text_size = BASE64_ENCODE_LENGTH(length)
	+ BASE64_ENCODE_FINAL_LENGTH;
      unsigned done;
      
396 397 398 399 400
      uint8_t *p
	= nettle_buffer_space(buffer, text_size);
      if (!p)
	return 0;

401 402 403 404 405 406
      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);
      
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);
  }
  
421 422
  return (write_string(buffer, "\nBEGIN PGP ")
	  && write_string(buffer, tag)
423 424
	  && NETTLE_BUFFER_PUTC(buffer, '\n'));
}