pgp-encode.c 9.25 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
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
/* 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.
 */

#include "pgp.h"

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

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

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
pgp_put_mpi(struct nettle_buffer *buffer, mpz_t x)
{
  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;
  
75
  nettle_mpz_set_str_256_u(x, octets, p);
76
77
78
79
80
81
82
83
84
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
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
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

  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
pgp_put_public_rsa_key(struct nettle_buffer *,
		       struct rsa_public_key *key,
		       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
	  + nettle_mpz_sizeinbase_256(pub->n)
	  + nettle_mpz_sizeinbase_256(pub->e));

  if (!pgp_put_header(buffer, PGP_TAG_PUBLIC_KEY, size))
    return 0;

  start = buffer->size;
  
  if (! (pgp_put_header(buffer, PGP_TAG_PUBLIC_KEY,
			/* Assume that we need two octets */
			PGP_LENGTH_TWO_OCTETS)
	  && pgp_put_uint32(buffer, 4)        /* Version */  
	  && pgp_put_uint32(buffer, now)      /* Time stamp */
	  && pgp_put_uint32(buffer, PGP_RSA)  /* Algorithm */
	  && pgp_put_mpi(buffer, pub->n)
	  && pgp_put_mpi(buffer, pub->e)) )
    return 0;

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

  return 1;
}

int
pgp_put_rsa_sha1_signature(struct nettle_buffer *buffer,
			   struct rsa_private_key *key,
			   const uint8_t *keyid,
			   unsigned type,
			   struct sha1_ctx *hash)
{
  unsigned signature_start = buffer->size;
  unsigned hash_end;
  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)
	 && pgp_put_uint16(0)))  /* Hashed subpacket length */
    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);

  {
    sha1_ctx hcopy = *hash;
    uint8_t *p = nettle_buffer_space(2);
    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;

  if (pgp_put_sub_packet(buffer, PGP_SUBPACKET_ISSUER, 8, keyid)
      && pgp_sub_packet_end(buffer, sub_packet_start))
    return 0;
    
  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)))

332
333
334
/* 15 base 64 groups data per line */
#define BINARY_PER_LINE 45
#define TEXT_PER_LINE BASE64_ENCODE_LENGTH(BINARY_PER_LINE)
335
336
337
338
339
340
341

int
pgp_armor(struct nettle_buffer *buffer,
	  const char *tag,
	  unsigned length,
	  const uint8_t *data)
{
342
343
  struct base64_encode_ctx ctx;
  
344
  unsigned crc = pgp_crc24(length, data);
345
346

  base64_encode_init(&ctx);
347
348
349
350
351
352
353
354
355
356
  
  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)
    {
357
      unsigned done;
358
359
360
361
362
363
      uint8_t *p
	= nettle_buffer_space(buffer, TEXT_PER_LINE);
      
      if (!p)
	return 0;

364
365
      done = base64_encode_update(&ctx, p, BINARY_PER_LINE, data);
      assert(done <= TEXT_PER_LINE);
366

367
368
369
      /* FIXME: Create some official way to do this */
      buffer->size -= (TEXT_PER_LINE - done);
      
370
371
372
373
374
375
      if (!NETTLE_BUFFER_PUTC(buffer, '\n'))
	return 0;
    }

  if (length)
    {
376
377
378
379
      unsigned text_size = BASE64_ENCODE_LENGTH(length)
	+ BASE64_ENCODE_FINAL_LENGTH;
      unsigned done;
      
380
381
382
383
384
      uint8_t *p
	= nettle_buffer_space(buffer, text_size);
      if (!p)
	return 0;

385
386
387
388
389
390
      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);
      
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
      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'));
}