1/*
2 * Copyright (c) 2011 The FreeBSD Project. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 */
25
26/* Based on:
27 * SHA256-based Unix crypt implementation. Released into the Public Domain by
28 * Ulrich Drepper <drepper@redhat.com>. */
29
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD$");
32
33#include <sys/endian.h>
34#include <sys/param.h>
35
36#include <errno.h>
37#include <limits.h>
38#include <sha256.h>
39#include <stdbool.h>
40#include <stdint.h>
41#include <stdio.h>
42#include <stdlib.h>
43#include <string.h>
44
45#include "crypt.h"
46
47/* Define our magic string to mark salt for SHA256 "encryption" replacement. */
48static const char sha256_salt_prefix[] = "$5$";
49
50/* Prefix for optional rounds specification. */
51static const char sha256_rounds_prefix[] = "rounds=";
52
53/* Maximum salt string length. */
54#define SALT_LEN_MAX 16
55/* Default number of rounds if not explicitly specified. */
56#define ROUNDS_DEFAULT 5000
57/* Minimum number of rounds. */
58#define ROUNDS_MIN 1000
59/* Maximum number of rounds. */
60#define ROUNDS_MAX 999999999
61
62static char *
63crypt_sha256_r(const char *key, const char *salt, char *buffer, int buflen)
64{
65	u_long srounds;
66	int n;
67	uint8_t alt_result[32], temp_result[32];
68	SHA256_CTX ctx, alt_ctx;
69	size_t salt_len, key_len, cnt, rounds;
70	char *cp, *copied_key, *copied_salt, *p_bytes, *s_bytes, *endp;
71	const char *num;
72	bool rounds_custom;
73
74	copied_key = NULL;
75	copied_salt = NULL;
76
77	/* Default number of rounds. */
78	rounds = ROUNDS_DEFAULT;
79	rounds_custom = false;
80
81	/* Find beginning of salt string. The prefix should normally always
82	 * be present. Just in case it is not. */
83	if (strncmp(sha256_salt_prefix, salt, sizeof(sha256_salt_prefix) - 1) == 0)
84		/* Skip salt prefix. */
85		salt += sizeof(sha256_salt_prefix) - 1;
86
87	if (strncmp(salt, sha256_rounds_prefix, sizeof(sha256_rounds_prefix) - 1)
88	    == 0) {
89		num = salt + sizeof(sha256_rounds_prefix) - 1;
90		srounds = strtoul(num, &endp, 10);
91
92		if (*endp == '$') {
93			salt = endp + 1;
94			rounds = MAX(ROUNDS_MIN, MIN(srounds, ROUNDS_MAX));
95			rounds_custom = true;
96		}
97	}
98
99	salt_len = MIN(strcspn(salt, "$"), SALT_LEN_MAX);
100	key_len = strlen(key);
101
102	/* Prepare for the real work. */
103	SHA256_Init(&ctx);
104
105	/* Add the key string. */
106	SHA256_Update(&ctx, key, key_len);
107
108	/* The last part is the salt string. This must be at most 8
109	 * characters and it ends at the first `$' character (for
110	 * compatibility with existing implementations). */
111	SHA256_Update(&ctx, salt, salt_len);
112
113	/* Compute alternate SHA256 sum with input KEY, SALT, and KEY. The
114	 * final result will be added to the first context. */
115	SHA256_Init(&alt_ctx);
116
117	/* Add key. */
118	SHA256_Update(&alt_ctx, key, key_len);
119
120	/* Add salt. */
121	SHA256_Update(&alt_ctx, salt, salt_len);
122
123	/* Add key again. */
124	SHA256_Update(&alt_ctx, key, key_len);
125
126	/* Now get result of this (32 bytes) and add it to the other context. */
127	SHA256_Final(alt_result, &alt_ctx);
128
129	/* Add for any character in the key one byte of the alternate sum. */
130	for (cnt = key_len; cnt > 32; cnt -= 32)
131		SHA256_Update(&ctx, alt_result, 32);
132	SHA256_Update(&ctx, alt_result, cnt);
133
134	/* Take the binary representation of the length of the key and for
135	 * every 1 add the alternate sum, for every 0 the key. */
136	for (cnt = key_len; cnt > 0; cnt >>= 1)
137		if ((cnt & 1) != 0)
138			SHA256_Update(&ctx, alt_result, 32);
139		else
140			SHA256_Update(&ctx, key, key_len);
141
142	/* Create intermediate result. */
143	SHA256_Final(alt_result, &ctx);
144
145	/* Start computation of P byte sequence. */
146	SHA256_Init(&alt_ctx);
147
148	/* For every character in the password add the entire password. */
149	for (cnt = 0; cnt < key_len; ++cnt)
150		SHA256_Update(&alt_ctx, key, key_len);
151
152	/* Finish the digest. */
153	SHA256_Final(temp_result, &alt_ctx);
154
155	/* Create byte sequence P. */
156	cp = p_bytes = alloca(key_len);
157	for (cnt = key_len; cnt >= 32; cnt -= 32) {
158		memcpy(cp, temp_result, 32);
159		cp += 32;
160	}
161	memcpy(cp, temp_result, cnt);
162
163	/* Start computation of S byte sequence. */
164	SHA256_Init(&alt_ctx);
165
166	/* For every character in the password add the entire password. */
167	for (cnt = 0; cnt < 16 + alt_result[0]; ++cnt)
168		SHA256_Update(&alt_ctx, salt, salt_len);
169
170	/* Finish the digest. */
171	SHA256_Final(temp_result, &alt_ctx);
172
173	/* Create byte sequence S. */
174	cp = s_bytes = alloca(salt_len);
175	for (cnt = salt_len; cnt >= 32; cnt -= 32) {
176		memcpy(cp, temp_result, 32);
177		cp += 32;
178	}
179	memcpy(cp, temp_result, cnt);
180
181	/* Repeatedly run the collected hash value through SHA256 to burn CPU
182	 * cycles. */
183	for (cnt = 0; cnt < rounds; ++cnt) {
184		/* New context. */
185		SHA256_Init(&ctx);
186
187		/* Add key or last result. */
188		if ((cnt & 1) != 0)
189			SHA256_Update(&ctx, p_bytes, key_len);
190		else
191			SHA256_Update(&ctx, alt_result, 32);
192
193		/* Add salt for numbers not divisible by 3. */
194		if (cnt % 3 != 0)
195			SHA256_Update(&ctx, s_bytes, salt_len);
196
197		/* Add key for numbers not divisible by 7. */
198		if (cnt % 7 != 0)
199			SHA256_Update(&ctx, p_bytes, key_len);
200
201		/* Add key or last result. */
202		if ((cnt & 1) != 0)
203			SHA256_Update(&ctx, alt_result, 32);
204		else
205			SHA256_Update(&ctx, p_bytes, key_len);
206
207		/* Create intermediate result. */
208		SHA256_Final(alt_result, &ctx);
209	}
210
211	/* Now we can construct the result string. It consists of three
212	 * parts. */
213	cp = stpncpy(buffer, sha256_salt_prefix, MAX(0, buflen));
214	buflen -= sizeof(sha256_salt_prefix) - 1;
215
216	if (rounds_custom) {
217		n = snprintf(cp, MAX(0, buflen), "%s%zu$",
218			 sha256_rounds_prefix, rounds);
219
220		cp += n;
221		buflen -= n;
222	}
223
224	cp = stpncpy(cp, salt, MIN((size_t)MAX(0, buflen), salt_len));
225	buflen -= MIN((size_t)MAX(0, buflen), salt_len);
226
227	if (buflen > 0) {
228		*cp++ = '$';
229		--buflen;
230	}
231
232	b64_from_24bit(alt_result[0], alt_result[10], alt_result[20], 4, &buflen, &cp);
233	b64_from_24bit(alt_result[21], alt_result[1], alt_result[11], 4, &buflen, &cp);
234	b64_from_24bit(alt_result[12], alt_result[22], alt_result[2], 4, &buflen, &cp);
235	b64_from_24bit(alt_result[3], alt_result[13], alt_result[23], 4, &buflen, &cp);
236	b64_from_24bit(alt_result[24], alt_result[4], alt_result[14], 4, &buflen, &cp);
237	b64_from_24bit(alt_result[15], alt_result[25], alt_result[5], 4, &buflen, &cp);
238	b64_from_24bit(alt_result[6], alt_result[16], alt_result[26], 4, &buflen, &cp);
239	b64_from_24bit(alt_result[27], alt_result[7], alt_result[17], 4, &buflen, &cp);
240	b64_from_24bit(alt_result[18], alt_result[28], alt_result[8], 4, &buflen, &cp);
241	b64_from_24bit(alt_result[9], alt_result[19], alt_result[29], 4, &buflen, &cp);
242	b64_from_24bit(0, alt_result[31], alt_result[30], 3, &buflen, &cp);
243	if (buflen <= 0) {
244		errno = ERANGE;
245		buffer = NULL;
246	}
247	else
248		*cp = '\0';	/* Terminate the string. */
249
250	/* Clear the buffer for the intermediate result so that people
251	 * attaching to processes or reading core dumps cannot get any
252	 * information. We do it in this way to clear correct_words[] inside
253	 * the SHA256 implementation as well. */
254	SHA256_Init(&ctx);
255	SHA256_Final(alt_result, &ctx);
256	memset(temp_result, '\0', sizeof(temp_result));
257	memset(p_bytes, '\0', key_len);
258	memset(s_bytes, '\0', salt_len);
259	memset(&ctx, '\0', sizeof(ctx));
260	memset(&alt_ctx, '\0', sizeof(alt_ctx));
261	if (copied_key != NULL)
262		memset(copied_key, '\0', key_len);
263	if (copied_salt != NULL)
264		memset(copied_salt, '\0', salt_len);
265
266	return buffer;
267}
268
269/* This entry point is equivalent to crypt(3). */
270char *
271crypt_sha256(const char *key, const char *salt)
272{
273	/* We don't want to have an arbitrary limit in the size of the
274	 * password. We can compute an upper bound for the size of the
275	 * result in advance and so we can prepare the buffer we pass to
276	 * `crypt_sha256_r'. */
277	static char *buffer;
278	static int buflen;
279	int needed;
280	char *new_buffer;
281
282	needed = (sizeof(sha256_salt_prefix) - 1
283	      + sizeof(sha256_rounds_prefix) + 9 + 1
284	      + strlen(salt) + 1 + 43 + 1);
285
286	if (buflen < needed) {
287		new_buffer = (char *)realloc(buffer, needed);
288
289		if (new_buffer == NULL)
290			return NULL;
291
292		buffer = new_buffer;
293		buflen = needed;
294	}
295
296	return crypt_sha256_r(key, salt, buffer, buflen);
297}
298
299#ifdef TEST
300
301static const struct {
302	const char *input;
303	const char result[32];
304} tests[] =
305{
306	/* Test vectors from FIPS 180-2: appendix B.1. */
307	{
308		"abc",
309		"\xba\x78\x16\xbf\x8f\x01\xcf\xea\x41\x41\x40\xde\x5d\xae\x22\x23"
310		"\xb0\x03\x61\xa3\x96\x17\x7a\x9c\xb4\x10\xff\x61\xf2\x00\x15\xad"
311	},
312	/* Test vectors from FIPS 180-2: appendix B.2. */
313	{
314		"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
315		"\x24\x8d\x6a\x61\xd2\x06\x38\xb8\xe5\xc0\x26\x93\x0c\x3e\x60\x39"
316		"\xa3\x3c\xe4\x59\x64\xff\x21\x67\xf6\xec\xed\xd4\x19\xdb\x06\xc1"
317	},
318	/* Test vectors from the NESSIE project. */
319	{
320		"",
321		"\xe3\xb0\xc4\x42\x98\xfc\x1c\x14\x9a\xfb\xf4\xc8\x99\x6f\xb9\x24"
322		"\x27\xae\x41\xe4\x64\x9b\x93\x4c\xa4\x95\x99\x1b\x78\x52\xb8\x55"
323	},
324	{
325		"a",
326		"\xca\x97\x81\x12\xca\x1b\xbd\xca\xfa\xc2\x31\xb3\x9a\x23\xdc\x4d"
327		"\xa7\x86\xef\xf8\x14\x7c\x4e\x72\xb9\x80\x77\x85\xaf\xee\x48\xbb"
328	},
329	{
330		"message digest",
331		"\xf7\x84\x6f\x55\xcf\x23\xe1\x4e\xeb\xea\xb5\xb4\xe1\x55\x0c\xad"
332		"\x5b\x50\x9e\x33\x48\xfb\xc4\xef\xa3\xa1\x41\x3d\x39\x3c\xb6\x50"
333	},
334	{
335		"abcdefghijklmnopqrstuvwxyz",
336		"\x71\xc4\x80\xdf\x93\xd6\xae\x2f\x1e\xfa\xd1\x44\x7c\x66\xc9\x52"
337		"\x5e\x31\x62\x18\xcf\x51\xfc\x8d\x9e\xd8\x32\xf2\xda\xf1\x8b\x73"
338	},
339	{
340		"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
341		"\x24\x8d\x6a\x61\xd2\x06\x38\xb8\xe5\xc0\x26\x93\x0c\x3e\x60\x39"
342		"\xa3\x3c\xe4\x59\x64\xff\x21\x67\xf6\xec\xed\xd4\x19\xdb\x06\xc1"
343	},
344	{
345		"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789",
346		"\xdb\x4b\xfc\xbd\x4d\xa0\xcd\x85\xa6\x0c\x3c\x37\xd3\xfb\xd8\x80"
347		"\x5c\x77\xf1\x5f\xc6\xb1\xfd\xfe\x61\x4e\xe0\xa7\xc8\xfd\xb4\xc0"
348	},
349	{
350		"123456789012345678901234567890123456789012345678901234567890"
351		"12345678901234567890",
352		"\xf3\x71\xbc\x4a\x31\x1f\x2b\x00\x9e\xef\x95\x2d\xd8\x3c\xa8\x0e"
353		"\x2b\x60\x02\x6c\x8e\x93\x55\x92\xd0\xf9\xc3\x08\x45\x3c\x81\x3e"
354	}
355};
356
357#define ntests (sizeof (tests) / sizeof (tests[0]))
358
359static const struct {
360	const char *salt;
361	const char *input;
362	const char *expected;
363} tests2[] =
364{
365	{
366		"$5$saltstring", "Hello world!",
367		"$5$saltstring$5B8vYYiY.CVt1RlTTf8KbXBH3hsxY/GNooZaBBGWEc5"
368	},
369	{
370		"$5$rounds=10000$saltstringsaltstring", "Hello world!",
371		"$5$rounds=10000$saltstringsaltst$3xv.VbSHBb41AL9AvLeujZkZRBAwqFMz2."
372		"opqey6IcA"
373	},
374	{
375		"$5$rounds=5000$toolongsaltstring", "This is just a test",
376		"$5$rounds=5000$toolongsaltstrin$Un/5jzAHMgOGZ5.mWJpuVolil07guHPvOW8"
377		"mGRcvxa5"
378	},
379	{
380		"$5$rounds=1400$anotherlongsaltstring",
381		"a very much longer text to encrypt.  This one even stretches over more"
382		"than one line.",
383		"$5$rounds=1400$anotherlongsalts$Rx.j8H.h8HjEDGomFU8bDkXm3XIUnzyxf12"
384		"oP84Bnq1"
385	},
386	{
387		"$5$rounds=77777$short",
388		"we have a short salt string but not a short password",
389		"$5$rounds=77777$short$JiO1O3ZpDAxGJeaDIuqCoEFysAe1mZNJRs3pw0KQRd/"
390	},
391	{
392		"$5$rounds=123456$asaltof16chars..", "a short string",
393		"$5$rounds=123456$asaltof16chars..$gP3VQ/6X7UUEW3HkBn2w1/Ptq2jxPyzV/"
394		"cZKmF/wJvD"
395	},
396	{
397		"$5$rounds=10$roundstoolow", "the minimum number is still observed",
398		"$5$rounds=1000$roundstoolow$yfvwcWrQ8l/K0DAWyuPMDNHpIVlTQebY9l/gL97"
399		"2bIC"
400	},
401};
402
403#define ntests2 (sizeof (tests2) / sizeof (tests2[0]))
404
405int
406main(void)
407{
408	SHA256_CTX ctx;
409	uint8_t sum[32];
410	int result = 0;
411	int i, cnt;
412
413	for (cnt = 0; cnt < (int)ntests; ++cnt) {
414		SHA256_Init(&ctx);
415		SHA256_Update(&ctx, tests[cnt].input, strlen(tests[cnt].input));
416		SHA256_Final(sum, &ctx);
417		if (memcmp(tests[cnt].result, sum, 32) != 0) {
418			for (i = 0; i < 32; i++)
419				printf("%02X", tests[cnt].result[i]);
420			printf("\n");
421			for (i = 0; i < 32; i++)
422				printf("%02X", sum[i]);
423			printf("\n");
424			printf("test %d run %d failed\n", cnt, 1);
425			result = 1;
426		}
427
428		SHA256_Init(&ctx);
429		for (i = 0; tests[cnt].input[i] != '\0'; ++i)
430			SHA256_Update(&ctx, &tests[cnt].input[i], 1);
431		SHA256_Final(sum, &ctx);
432		if (memcmp(tests[cnt].result, sum, 32) != 0) {
433			for (i = 0; i < 32; i++)
434				printf("%02X", tests[cnt].result[i]);
435			printf("\n");
436			for (i = 0; i < 32; i++)
437				printf("%02X", sum[i]);
438			printf("\n");
439			printf("test %d run %d failed\n", cnt, 2);
440			result = 1;
441		}
442	}
443
444	/* Test vector from FIPS 180-2: appendix B.3. */
445	char buf[1000];
446
447	memset(buf, 'a', sizeof(buf));
448	SHA256_Init(&ctx);
449	for (i = 0; i < 1000; ++i)
450		SHA256_Update(&ctx, buf, sizeof(buf));
451	SHA256_Final(sum, &ctx);
452	static const char expected[32] =
453	"\xcd\xc7\x6e\x5c\x99\x14\xfb\x92\x81\xa1\xc7\xe2\x84\xd7\x3e\x67"
454	"\xf1\x80\x9a\x48\xa4\x97\x20\x0e\x04\x6d\x39\xcc\xc7\x11\x2c\xd0";
455
456	if (memcmp(expected, sum, 32) != 0) {
457		printf("test %d failed\n", cnt);
458		result = 1;
459	}
460
461	for (cnt = 0; cnt < ntests2; ++cnt) {
462		char *cp = crypt_sha256(tests2[cnt].input, tests2[cnt].salt);
463
464		if (strcmp(cp, tests2[cnt].expected) != 0) {
465			printf("test %d: expected \"%s\", got \"%s\"\n",
466			       cnt, tests2[cnt].expected, cp);
467			result = 1;
468		}
469	}
470
471	if (result == 0)
472		puts("all tests OK");
473
474	return result;
475}
476
477#endif /* TEST */
478