aboutsummaryrefslogtreecommitdiff
path: root/crypt/sha256-crypt.c
blob: eb2585b52796c5b6f14b62ae7e859e4f6df6cbd8 (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
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
/* One way encryption based on SHA256 sum.
   Copyright (C) 2007, 2009 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@redhat.com>, 2007.

   The GNU C 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 GNU C 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 GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>

#include "sha256.h"


#ifdef USE_NSS
typedef int PRBool;
# include <hasht.h>
# include <nsslowhash.h>

# define sha256_init_ctx(ctxp, nss_ctxp) \
  do									      \
    {									      \
      if (((nss_ctxp = NSSLOWHASH_NewContext (nss_ictx, HASH_AlgSHA256))      \
	   == NULL))							      \
	{								      \
	  if (nss_ctx != NULL)						      \
	    NSSLOWHASH_Destroy (nss_ctx);				      \
	  if (nss_alt_ctx != NULL)					      \
	    NSSLOWHASH_Destroy (nss_alt_ctx);				      \
	  return NULL;							      \
	}								      \
      NSSLOWHASH_Begin (nss_ctxp);					      \
    }									      \
  while (0)

# define sha256_process_bytes(buf, len, ctxp, nss_ctxp) \
  NSSLOWHASH_Update (nss_ctxp, (const unsigned char *) buf, len)

# define sha256_finish_ctx(ctxp, nss_ctxp, result) \
  do									      \
    {									      \
      unsigned int ret;							      \
      NSSLOWHASH_End (nss_ctxp, result, &ret, sizeof (result));		      \
      assert (ret == sizeof (result));					      \
      NSSLOWHASH_Destroy (nss_ctxp);					      \
      nss_ctxp = NULL;							      \
    }									      \
  while (0)
#else
# define sha256_init_ctx(ctxp, nss_ctxp) \
  __sha256_init_ctx (ctxp)

# define sha256_process_bytes(buf, len, ctxp, nss_ctxp) \
  __sha256_process_bytes(buf, len, ctxp)

# define sha256_finish_ctx(ctxp, nss_ctxp, result) \
  __sha256_finish_ctx (ctxp, result)
#endif


/* Define our magic string to mark salt for SHA256 "encryption"
   replacement.  */
static const char sha256_salt_prefix[] = "$5$";

/* Prefix for optional rounds specification.  */
static const char sha256_rounds_prefix[] = "rounds=";

/* Maximum salt string length.  */
#define SALT_LEN_MAX 16
/* Default number of rounds if not explicitly specified.  */
#define ROUNDS_DEFAULT 5000
/* Minimum number of rounds.  */
#define ROUNDS_MIN 1000
/* Maximum number of rounds.  */
#define ROUNDS_MAX 999999999

/* Table with characters for base64 transformation.  */
static const char b64t[64] =
"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";


/* Prototypes for local functions.  */
extern char *__sha256_crypt_r (const char *key, const char *salt,
			       char *buffer, int buflen);
extern char *__sha256_crypt (const char *key, const char *salt);


char *
__sha256_crypt_r (key, salt, buffer, buflen)
     const char *key;
     const char *salt;
     char *buffer;
     int buflen;
{
  unsigned char alt_result[32]
    __attribute__ ((__aligned__ (__alignof__ (uint32_t))));
  unsigned char temp_result[32]
    __attribute__ ((__aligned__ (__alignof__ (uint32_t))));
  size_t salt_len;
  size_t key_len;
  size_t cnt;
  char *cp;
  char *copied_key = NULL;
  char *copied_salt = NULL;
  char *p_bytes;
  char *s_bytes;
  /* Default number of rounds.  */
  size_t rounds = ROUNDS_DEFAULT;
  bool rounds_custom = false;

  /* Find beginning of salt string.  The prefix should normally always
     be present.  Just in case it is not.  */
  if (strncmp (sha256_salt_prefix, salt, sizeof (sha256_salt_prefix) - 1) == 0)
    /* Skip salt prefix.  */
    salt += sizeof (sha256_salt_prefix) - 1;

  if (strncmp (salt, sha256_rounds_prefix, sizeof (sha256_rounds_prefix) - 1)
      == 0)
    {
      const char *num = salt + sizeof (sha256_rounds_prefix) - 1;
      char *endp;
      unsigned long int srounds = strtoul (num, &endp, 10);
      if (*endp == '$')
	{
	  salt = endp + 1;
	  rounds = MAX (ROUNDS_MIN, MIN (srounds, ROUNDS_MAX));
	  rounds_custom = true;
	}
    }

  salt_len = MIN (strcspn (salt, "$"), SALT_LEN_MAX);
  key_len = strlen (key);

  if ((key - (char *) 0) % __alignof__ (uint32_t) != 0)
    {
      char *tmp = (char *) alloca (key_len + __alignof__ (uint32_t));
      key = copied_key =
	memcpy (tmp + __alignof__ (uint32_t)
		- (tmp - (char *) 0) % __alignof__ (uint32_t),
		key, key_len);
      assert ((key - (char *) 0) % __alignof__ (uint32_t) == 0);
    }

  if ((salt - (char *) 0) % __alignof__ (uint32_t) != 0)
    {
      char *tmp = (char *) alloca (salt_len + __alignof__ (uint32_t));
      salt = copied_salt =
	memcpy (tmp + __alignof__ (uint32_t)
		- (tmp - (char *) 0) % __alignof__ (uint32_t),
		salt, salt_len);
      assert ((salt - (char *) 0) % __alignof__ (uint32_t) == 0);
    }

#ifdef USE_NSS
  /* Initialize libfreebl3.  */
  NSSLOWInitContext *nss_ictx = NSSLOW_Init ();
  if (nss_ictx == NULL)
    return NULL;
  NSSLOWHASHContext *nss_ctx = NULL;
  NSSLOWHASHContext *nss_alt_ctx = NULL;
#else
  struct sha256_ctx ctx;
  struct sha256_ctx alt_ctx;
#endif

  /* Prepare for the real work.  */
  sha256_init_ctx (&ctx, nss_ctx);

  /* Add the key string.  */
  sha256_process_bytes (key, key_len, &ctx, nss_ctx);

  /* The last part is the salt string.  This must be at most 16
     characters and it ends at the first `$' character.  */
  sha256_process_bytes (salt, salt_len, &ctx, nss_ctx);


  /* Compute alternate SHA256 sum with input KEY, SALT, and KEY.  The
     final result will be added to the first context.  */
  sha256_init_ctx (&alt_ctx, nss_alt_ctx);

  /* Add key.  */
  sha256_process_bytes (key, key_len, &alt_ctx, nss_alt_ctx);

  /* Add salt.  */
  sha256_process_bytes (salt, salt_len, &alt_ctx, nss_alt_ctx);

  /* Add key again.  */
  sha256_process_bytes (key, key_len, &alt_ctx, nss_alt_ctx);

  /* Now get result of this (32 bytes) and add it to the other
     context.  */
  sha256_finish_ctx (&alt_ctx, nss_alt_ctx, alt_result);

  /* Add for any character in the key one byte of the alternate sum.  */
  for (cnt = key_len; cnt > 32; cnt -= 32)
    sha256_process_bytes (alt_result, 32, &ctx, nss_ctx);
  sha256_process_bytes (alt_result, cnt, &ctx, nss_ctx);

  /* Take the binary representation of the length of the key and for every
     1 add the alternate sum, for every 0 the key.  */
  for (cnt = key_len; cnt > 0; cnt >>= 1)
    if ((cnt & 1) != 0)
      sha256_process_bytes (alt_result, 32, &ctx, nss_ctx);
    else
      sha256_process_bytes (key, key_len, &ctx, nss_ctx);

  /* Create intermediate result.  */
  sha256_finish_ctx (&ctx, nss_ctx, alt_result);

  /* Start computation of P byte sequence.  */
  sha256_init_ctx (&alt_ctx, nss_alt_ctx);

  /* For every character in the password add the entire password.  */
  for (cnt = 0; cnt < key_len; ++cnt)
    sha256_process_bytes (key, key_len, &alt_ctx, nss_alt_ctx);

  /* Finish the digest.  */
  sha256_finish_ctx (&alt_ctx, nss_alt_ctx, temp_result);

  /* Create byte sequence P.  */
  cp = p_bytes = alloca (key_len);
  for (cnt = key_len; cnt >= 32; cnt -= 32)
    cp = mempcpy (cp, temp_result, 32);
  memcpy (cp, temp_result, cnt);

  /* Start computation of S byte sequence.  */
  sha256_init_ctx (&alt_ctx, nss_alt_ctx);

  /* For every character in the password add the entire password.  */
  for (cnt = 0; cnt < 16 + alt_result[0]; ++cnt)
    sha256_process_bytes (salt, salt_len, &alt_ctx, nss_alt_ctx);

  /* Finish the digest.  */
  sha256_finish_ctx (&alt_ctx, nss_alt_ctx, temp_result);

  /* Create byte sequence S.  */
  cp = s_bytes = alloca (salt_len);
  for (cnt = salt_len; cnt >= 32; cnt -= 32)
    cp = mempcpy (cp, temp_result, 32);
  memcpy (cp, temp_result, cnt);

  /* Repeatedly run the collected hash value through SHA256 to burn
     CPU cycles.  */
  for (cnt = 0; cnt < rounds; ++cnt)
    {
      /* New context.  */
      sha256_init_ctx (&ctx, nss_ctx);

      /* Add key or last result.  */
      if ((cnt & 1) != 0)
	sha256_process_bytes (p_bytes, key_len, &ctx, nss_ctx);
      else
	sha256_process_bytes (alt_result, 32, &ctx, nss_ctx);

      /* Add salt for numbers not divisible by 3.  */
      if (cnt % 3 != 0)
	sha256_process_bytes (s_bytes, salt_len, &ctx, nss_ctx);

      /* Add key for numbers not divisible by 7.  */
      if (cnt % 7 != 0)
	sha256_process_bytes (p_bytes, key_len, &ctx, nss_ctx);

      /* Add key or last result.  */
      if ((cnt & 1) != 0)
	sha256_process_bytes (alt_result, 32, &ctx, nss_ctx);
      else
	sha256_process_bytes (p_bytes, key_len, &ctx, nss_ctx);

      /* Create intermediate result.  */
      sha256_finish_ctx (&ctx, nss_ctx, alt_result);
    }

#ifdef USE_NSS
  /* Free libfreebl3 resources. */
  NSSLOW_Shutdown (nss_ictx);
#endif

  /* Now we can construct the result string.  It consists of three
     parts.  */
  cp = __stpncpy (buffer, sha256_salt_prefix, MAX (0, buflen));
  buflen -= sizeof (sha256_salt_prefix) - 1;

  if (rounds_custom)
    {
      int n = snprintf (cp, MAX (0, buflen), "%s%zu$",
			sha256_rounds_prefix, rounds);
      cp += n;
      buflen -= n;
    }

  cp = __stpncpy (cp, salt, MIN ((size_t) MAX (0, buflen), salt_len));
  buflen -= MIN ((size_t) MAX (0, buflen), salt_len);

  if (buflen > 0)
    {
      *cp++ = '$';
      --buflen;
    }

  void b64_from_24bit (unsigned int b2, unsigned int b1, unsigned int b0,
		       int n)
  {
    unsigned int w = (b2 << 16) | (b1 << 8) | b0;
    while (n-- > 0 && buflen > 0)
      {
	*cp++ = b64t[w & 0x3f];
	--buflen;
	w >>= 6;
      }
  }

  b64_from_24bit (alt_result[0], alt_result[10], alt_result[20], 4);
  b64_from_24bit (alt_result[21], alt_result[1], alt_result[11], 4);
  b64_from_24bit (alt_result[12], alt_result[22], alt_result[2], 4);
  b64_from_24bit (alt_result[3], alt_result[13], alt_result[23], 4);
  b64_from_24bit (alt_result[24], alt_result[4], alt_result[14], 4);
  b64_from_24bit (alt_result[15], alt_result[25], alt_result[5], 4);
  b64_from_24bit (alt_result[6], alt_result[16], alt_result[26], 4);
  b64_from_24bit (alt_result[27], alt_result[7], alt_result[17], 4);
  b64_from_24bit (alt_result[18], alt_result[28], alt_result[8], 4);
  b64_from_24bit (alt_result[9], alt_result[19], alt_result[29], 4);
  b64_from_24bit (0, alt_result[31], alt_result[30], 3);
  if (buflen <= 0)
    {
      __set_errno (ERANGE);
      buffer = NULL;
    }
  else
    *cp = '\0';		/* Terminate the string.  */

  /* Clear the buffer for the intermediate result so that people
     attaching to processes or reading core dumps cannot get any
     information.  We do it in this way to clear correct_words[]
     inside the SHA256 implementation as well.  */
#ifndef USE_NSS
  __sha256_init_ctx (&ctx);
  __sha256_finish_ctx (&ctx, alt_result);
  memset (&ctx, '\0', sizeof (ctx));
  memset (&alt_ctx, '\0', sizeof (alt_ctx));
#endif
  memset (temp_result, '\0', sizeof (temp_result));
  memset (p_bytes, '\0', key_len);
  memset (s_bytes, '\0', salt_len);
  if (copied_key != NULL)
    memset (copied_key, '\0', key_len);
  if (copied_salt != NULL)
    memset (copied_salt, '\0', salt_len);

  return buffer;
}

#ifndef _LIBC
# define libc_freeres_ptr(decl) decl
#endif
libc_freeres_ptr (static char *buffer);

/* This entry point is equivalent to the `crypt' function in Unix
   libcs.  */
char *
__sha256_crypt (const char *key, const char *salt)
{
  /* We don't want to have an arbitrary limit in the size of the
     password.  We can compute an upper bound for the size of the
     result in advance and so we can prepare the buffer we pass to
     `sha256_crypt_r'.  */
  static int buflen;
  int needed = (sizeof (sha256_salt_prefix) - 1
		+ sizeof (sha256_rounds_prefix) + 9 + 1
		+ strlen (salt) + 1 + 43 + 1);

  if (buflen < needed)
    {
      char *new_buffer = (char *) realloc (buffer, needed);
      if (new_buffer == NULL)
	return NULL;

      buffer = new_buffer;
      buflen = needed;
    }

  return __sha256_crypt_r (key, salt, buffer, buflen);
}

#ifndef _LIBC
static void
__attribute__ ((__destructor__))
free_mem (void)
{
  free (buffer);
}
#endif