summaryrefslogtreecommitdiff
path: root/usr.bin/ssh/authfile.c
blob: bd7b88b8ebce097fc66a70efa6c784a4c6c11118 (plain)
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
75
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
332
333
334
335
/*

authfile.c

Author: Tatu Ylonen <ylo@cs.hut.fi>

Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
                   All rights reserved

Created: Mon Mar 27 03:52:05 1995 ylo

This file contains functions for reading and writing identity files, and
for reading the passphrase from the user.

*/

#include "includes.h"
RCSID("$Id: authfile.c,v 1.3 1999/09/28 04:45:35 provos Exp $");

#include <ssl/bn.h>
#include "xmalloc.h"
#include "buffer.h"
#include "bufaux.h"
#include "cipher.h"
#include "ssh.h"

/* Version identification string for identity files. */
#define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n"

/* Saves the authentication (private) key in a file, encrypting it with
   passphrase.  The identification of the file (lowest 64 bits of n)
   will precede the key to provide identification of the key without
   needing a passphrase. */

int
save_private_key(const char *filename, const char *passphrase,
		 RSA *key, const char *comment)
{
  Buffer buffer, encrypted;
  char buf[100], *cp;
  int f, i;
  CipherContext cipher;
  int cipher_type;
  u_int32_t rand;

  /* If the passphrase is empty, use SSH_CIPHER_NONE to ease converting to
     another cipher; otherwise use SSH_AUTHFILE_CIPHER. */
  if (strcmp(passphrase, "") == 0)
    cipher_type = SSH_CIPHER_NONE;
  else
    cipher_type = SSH_AUTHFILE_CIPHER;

  /* This buffer is used to built the secret part of the private key. */
  buffer_init(&buffer);
  
  /* Put checkbytes for checking passphrase validity. */
  rand = arc4random();
  buf[0] = rand & 0xff;
  buf[1] = (rand >> 8) & 0xff;
  buf[2] = buf[0];
  buf[3] = buf[1];
  buffer_append(&buffer, buf, 4);

  /* Store the private key (n and e will not be stored because they will
     be stored in plain text, and storing them also in encrypted format
     would just give known plaintext). */
  buffer_put_bignum(&buffer, key->d);
  buffer_put_bignum(&buffer, key->iqmp);
  buffer_put_bignum(&buffer, key->q); /* reverse from SSL p */
  buffer_put_bignum(&buffer, key->p); /* reverse from SSL q */

  /* Pad the part to be encrypted until its size is a multiple of 8. */
  while (buffer_len(&buffer) % 8 != 0)
    buffer_put_char(&buffer, 0);

  /* This buffer will be used to contain the data in the file. */
  buffer_init(&encrypted);

  /* First store keyfile id string. */
  cp = AUTHFILE_ID_STRING;
  for (i = 0; cp[i]; i++)
    buffer_put_char(&encrypted, cp[i]);
  buffer_put_char(&encrypted, 0);

  /* Store cipher type. */
  buffer_put_char(&encrypted, cipher_type);
  buffer_put_int(&encrypted, 0);  /* For future extension */

  /* Store public key.  This will be in plain text. */
  buffer_put_int(&encrypted, BN_num_bits(key->n));
  buffer_put_bignum(&encrypted, key->n);
  buffer_put_bignum(&encrypted, key->e);
  buffer_put_string(&encrypted, comment, strlen(comment));

  /* Allocate space for the private part of the key in the buffer. */
  buffer_append_space(&encrypted, &cp, buffer_len(&buffer));

  cipher_set_key_string(&cipher, cipher_type, passphrase, 1);
  cipher_encrypt(&cipher, (unsigned char *)cp, 
		 (unsigned char *)buffer_ptr(&buffer),
		 buffer_len(&buffer));
  memset(&cipher, 0, sizeof(cipher));

  /* Destroy temporary data. */
  memset(buf, 0, sizeof(buf));
  buffer_free(&buffer);

  /* Write to a file. */
  f = open(filename, O_WRONLY|O_CREAT|O_TRUNC, 0600);
  if (f < 0)
    return 0;

  if (write(f, buffer_ptr(&encrypted), buffer_len(&encrypted)) != 
      buffer_len(&encrypted))
    {
      debug("Write to key file %.200s failed: %.100s", filename,
	    strerror(errno));
      buffer_free(&encrypted);
      close(f);
      remove(filename);
      return 0;
    }
  close(f);
  buffer_free(&encrypted);
  return 1;
}

/* Loads the public part of the key file.  Returns 0 if an error
   was encountered (the file does not exist or is not readable), and
   non-zero otherwise. */

int
load_public_key(const char *filename, RSA *pub, 
		char **comment_return)
{
  int f, i;
  unsigned long len;
  Buffer buffer;
  char *cp;

  /* Read data from the file into the buffer. */
  f = open(filename, O_RDONLY);
  if (f < 0)
    return 0;

  len = lseek(f, (off_t)0L, 2);
  lseek(f, (off_t)0L, 0);
  
  buffer_init(&buffer);
  buffer_append_space(&buffer, &cp, len);

  if (read(f, cp, len) != len)
    {
      debug("Read from key file %.200s failed: %.100s", filename, 
	    strerror(errno));
      buffer_free(&buffer);
      close(f);
      return 0;
    }
  close(f);

  /* Check that it is at least big enought to contain the ID string. */
  if (len < strlen(AUTHFILE_ID_STRING) + 1)
    {
      debug("Bad key file %.200s.", filename);
      buffer_free(&buffer);
      return 0;
    }

  /* Make sure it begins with the id string.  Consume the id string from
     the buffer. */
  for (i = 0; i < (unsigned int)strlen(AUTHFILE_ID_STRING) + 1; i++)
    if (buffer_get_char(&buffer) != (unsigned char)AUTHFILE_ID_STRING[i])
      {
	debug("Bad key file %.200s.", filename);
	buffer_free(&buffer);
	return 0;
      }

  /* Skip cipher type and reserved data. */
  (void)buffer_get_char(&buffer); /* cipher type */
  (void)buffer_get_int(&buffer); /* reserved */

  /* Read the public key from the buffer. */
  buffer_get_int(&buffer);
  pub->n = BN_new();
  buffer_get_bignum(&buffer, pub->n);
  pub->e = BN_new();
  buffer_get_bignum(&buffer, pub->e);
  if (comment_return)
    *comment_return = buffer_get_string(&buffer, NULL);
  /* The encrypted private part is not parsed by this function. */

  buffer_free(&buffer);
  
  return 1;
}

/* Loads the private key from the file.  Returns 0 if an error is encountered
   (file does not exist or is not readable, or passphrase is bad).
   This initializes the private key. */

int
load_private_key(const char *filename, const char *passphrase,
		 RSA *prv, char **comment_return)
{
  int f, i, check1, check2, cipher_type;
  unsigned long len;
  Buffer buffer, decrypted;
  char *cp;
  CipherContext cipher;
  BN_CTX *ctx;
  BIGNUM *aux;

  /* Read the file into the buffer. */
  f = open(filename, O_RDONLY);
  if (f < 0)
    return 0;

  len = lseek(f, (off_t)0L, 2);
  lseek(f, (off_t)0L, 0);
  
  buffer_init(&buffer);
  buffer_append_space(&buffer, &cp, len);

  if (read(f, cp, len) != len)
    {
      debug("Read from key file %.200s failed: %.100s", filename,
	    strerror(errno));
      buffer_free(&buffer);
      close(f);
      return 0;
    }
  close(f);

  /* Check that it is at least big enought to contain the ID string. */
  if (len < strlen(AUTHFILE_ID_STRING) + 1)
    {
      debug("Bad key file %.200s.", filename);
      buffer_free(&buffer);
      return 0;
    }

  /* Make sure it begins with the id string.  Consume the id string from
     the buffer. */
  for (i = 0; i < (unsigned int)strlen(AUTHFILE_ID_STRING) + 1; i++)
    if (buffer_get_char(&buffer) != (unsigned char)AUTHFILE_ID_STRING[i])
      {
	debug("Bad key file %.200s.", filename);
	buffer_free(&buffer);
	return 0;
      }

  /* Read cipher type. */
  cipher_type = buffer_get_char(&buffer);
  (void)buffer_get_int(&buffer);  /* Reserved data. */

  /* Read the public key from the buffer. */
  buffer_get_int(&buffer);
  prv->n = BN_new();
  buffer_get_bignum(&buffer, prv->n);
  prv->e = BN_new();
  buffer_get_bignum(&buffer, prv->e);
  if (comment_return)
    *comment_return = buffer_get_string(&buffer, NULL);
  else
    xfree(buffer_get_string(&buffer, NULL));

  /* Check that it is a supported cipher. */
  if ((cipher_mask() & (1 << cipher_type)) == 0)
    {
      debug("Unsupported cipher %.100s used in key file %.200s.",
	    cipher_name(cipher_type), filename);
      buffer_free(&buffer);
      goto fail;
    }

  /* Initialize space for decrypted data. */
  buffer_init(&decrypted);
  buffer_append_space(&decrypted, &cp, buffer_len(&buffer));
      
  /* Rest of the buffer is encrypted.  Decrypt it using the passphrase. */
  cipher_set_key_string(&cipher, cipher_type, passphrase, 0);
  cipher_decrypt(&cipher, (unsigned char *)cp,
		 (unsigned char *)buffer_ptr(&buffer),
		 buffer_len(&buffer));

  buffer_free(&buffer);

  check1 = buffer_get_char(&decrypted);
  check2 = buffer_get_char(&decrypted);
  if (check1 != buffer_get_char(&decrypted) ||
      check2 != buffer_get_char(&decrypted))
    {
      if (strcmp(passphrase, "") != 0)
	debug("Bad passphrase supplied for key file %.200s.", filename);
      /* Bad passphrase. */
      buffer_free(&decrypted);
    fail:
      BN_clear_free(prv->n);
      BN_clear_free(prv->e);
      if (comment_return)
	xfree(*comment_return);
      return 0;
    }

  /* Read the rest of the private key. */
  prv->d = BN_new();
  buffer_get_bignum(&decrypted, prv->d);
  prv->iqmp = BN_new();
  buffer_get_bignum(&decrypted, prv->iqmp); /* u */
  /* in SSL and SSH p and q are exchanged */
  prv->q = BN_new();
  buffer_get_bignum(&decrypted, prv->q); /* p */
  prv->p = BN_new();
  buffer_get_bignum(&decrypted, prv->p); /* q */

  ctx = BN_CTX_new();
  aux = BN_new();

  BN_sub(aux, prv->q, BN_value_one());
  prv->dmq1 = BN_new();
  BN_mod(prv->dmq1, prv->d, aux, ctx);

  BN_sub(aux, prv->p, BN_value_one());
  prv->dmp1 = BN_new();
  BN_mod(prv->dmp1, prv->d, aux, ctx);

  BN_clear_free(aux);
  BN_CTX_free(ctx);
  
  buffer_free(&decrypted);

  return 1;
}