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