xref: /openbsd/lib/libc/crypt/bcrypt.c (revision 404b540a)
1 /*	$OpenBSD: bcrypt.c,v 1.24 2008/04/02 19:54:05 millert Exp $	*/
2 
3 /*
4  * Copyright 1997 Niels Provos <provos@physnet.uni-hamburg.de>
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *      This product includes software developed by Niels Provos.
18  * 4. The name of the author may not be used to endorse or promote products
19  *    derived from this software without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31  */
32 
33 /* This password hashing algorithm was designed by David Mazieres
34  * <dm@lcs.mit.edu> and works as follows:
35  *
36  * 1. state := InitState ()
37  * 2. state := ExpandKey (state, salt, password) 3.
38  * REPEAT rounds:
39  *	state := ExpandKey (state, 0, salt)
40  *      state := ExpandKey(state, 0, password)
41  * 4. ctext := "OrpheanBeholderScryDoubt"
42  * 5. REPEAT 64:
43  * 	ctext := Encrypt_ECB (state, ctext);
44  * 6. RETURN Concatenate (salt, ctext);
45  *
46  */
47 
48 #include <stdio.h>
49 #include <stdlib.h>
50 #include <sys/types.h>
51 #include <string.h>
52 #include <pwd.h>
53 #include <blf.h>
54 
55 /* This implementation is adaptable to current computing power.
56  * You can have up to 2^31 rounds which should be enough for some
57  * time to come.
58  */
59 
60 #define BCRYPT_VERSION '2'
61 #define BCRYPT_MAXSALT 16	/* Precomputation is just so nice */
62 #define BCRYPT_BLOCKS 6		/* Ciphertext blocks */
63 #define BCRYPT_MINROUNDS 16	/* we have log2(rounds) in salt */
64 
65 char   *bcrypt_gensalt(u_int8_t);
66 
67 static void encode_salt(char *, u_int8_t *, u_int16_t, u_int8_t);
68 static void encode_base64(u_int8_t *, u_int8_t *, u_int16_t);
69 static void decode_base64(u_int8_t *, u_int16_t, u_int8_t *);
70 
71 static char    encrypted[_PASSWORD_LEN];
72 static char    gsalt[7 + (BCRYPT_MAXSALT * 4 + 2) / 3 + 1];
73 static char    error[] = ":";
74 
75 const static u_int8_t Base64Code[] =
76 "./ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
77 
78 const static u_int8_t index_64[128] = {
79 	255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
80 	255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
81 	255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
82 	255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
83 	255, 255, 255, 255, 255, 255, 0, 1, 54, 55,
84 	56, 57, 58, 59, 60, 61, 62, 63, 255, 255,
85 	255, 255, 255, 255, 255, 2, 3, 4, 5, 6,
86 	7, 8, 9, 10, 11, 12, 13, 14, 15, 16,
87 	17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,
88 	255, 255, 255, 255, 255, 255, 28, 29, 30,
89 	31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
90 	41, 42, 43, 44, 45, 46, 47, 48, 49, 50,
91 	51, 52, 53, 255, 255, 255, 255, 255
92 };
93 #define CHAR64(c)  ( (c) > 127 ? 255 : index_64[(c)])
94 
95 static void
96 decode_base64(u_int8_t *buffer, u_int16_t len, u_int8_t *data)
97 {
98 	u_int8_t *bp = buffer;
99 	u_int8_t *p = data;
100 	u_int8_t c1, c2, c3, c4;
101 	while (bp < buffer + len) {
102 		c1 = CHAR64(*p);
103 		c2 = CHAR64(*(p + 1));
104 
105 		/* Invalid data */
106 		if (c1 == 255 || c2 == 255)
107 			break;
108 
109 		*bp++ = (c1 << 2) | ((c2 & 0x30) >> 4);
110 		if (bp >= buffer + len)
111 			break;
112 
113 		c3 = CHAR64(*(p + 2));
114 		if (c3 == 255)
115 			break;
116 
117 		*bp++ = ((c2 & 0x0f) << 4) | ((c3 & 0x3c) >> 2);
118 		if (bp >= buffer + len)
119 			break;
120 
121 		c4 = CHAR64(*(p + 3));
122 		if (c4 == 255)
123 			break;
124 		*bp++ = ((c3 & 0x03) << 6) | c4;
125 
126 		p += 4;
127 	}
128 }
129 
130 static void
131 encode_salt(char *salt, u_int8_t *csalt, u_int16_t clen, u_int8_t logr)
132 {
133 	salt[0] = '$';
134 	salt[1] = BCRYPT_VERSION;
135 	salt[2] = 'a';
136 	salt[3] = '$';
137 
138 	snprintf(salt + 4, 4, "%2.2u$", logr);
139 
140 	encode_base64((u_int8_t *) salt + 7, csalt, clen);
141 }
142 /* Generates a salt for this version of crypt.
143    Since versions may change. Keeping this here
144    seems sensible.
145  */
146 
147 char *
148 bcrypt_gensalt(u_int8_t log_rounds)
149 {
150 	u_int8_t csalt[BCRYPT_MAXSALT];
151 	u_int16_t i;
152 	u_int32_t seed = 0;
153 
154 	for (i = 0; i < BCRYPT_MAXSALT; i++) {
155 		if (i % 4 == 0)
156 			seed = arc4random();
157 		csalt[i] = seed & 0xff;
158 		seed = seed >> 8;
159 	}
160 
161 	if (log_rounds < 4)
162 		log_rounds = 4;
163 	else if (log_rounds > 31)
164 		log_rounds = 31;
165 
166 	encode_salt(gsalt, csalt, BCRYPT_MAXSALT, log_rounds);
167 	return gsalt;
168 }
169 /* We handle $Vers$log2(NumRounds)$salt+passwd$
170    i.e. $2$04$iwouldntknowwhattosayetKdJ6iFtacBqJdKe6aW7ou */
171 
172 char   *
173 bcrypt(const char *key, const char *salt)
174 {
175 	blf_ctx state;
176 	u_int32_t rounds, i, k;
177 	u_int16_t j;
178 	u_int8_t key_len, salt_len, logr, minor;
179 	u_int8_t ciphertext[4 * BCRYPT_BLOCKS] = "OrpheanBeholderScryDoubt";
180 	u_int8_t csalt[BCRYPT_MAXSALT];
181 	u_int32_t cdata[BCRYPT_BLOCKS];
182 	int n;
183 
184 	/* Discard "$" identifier */
185 	salt++;
186 
187 	if (*salt > BCRYPT_VERSION) {
188 		/* How do I handle errors ? Return ':' */
189 		return error;
190 	}
191 
192 	/* Check for minor versions */
193 	if (salt[1] != '$') {
194 		 switch (salt[1]) {
195 		 case 'a':
196 			 /* 'ab' should not yield the same as 'abab' */
197 			 minor = salt[1];
198 			 salt++;
199 			 break;
200 		 default:
201 			 return error;
202 		 }
203 	} else
204 		 minor = 0;
205 
206 	/* Discard version + "$" identifier */
207 	salt += 2;
208 
209 	if (salt[2] != '$')
210 		/* Out of sync with passwd entry */
211 		return error;
212 
213 	/* Computer power doesn't increase linear, 2^x should be fine */
214 	n = atoi(salt);
215 	if (n > 31 || n < 0)
216 		return error;
217 	logr = (u_int8_t)n;
218 	if ((rounds = (u_int32_t) 1 << logr) < BCRYPT_MINROUNDS)
219 		return error;
220 
221 	/* Discard num rounds + "$" identifier */
222 	salt += 3;
223 
224 	if (strlen(salt) * 3 / 4 < BCRYPT_MAXSALT)
225 		return error;
226 
227 	/* We dont want the base64 salt but the raw data */
228 	decode_base64(csalt, BCRYPT_MAXSALT, (u_int8_t *) salt);
229 	salt_len = BCRYPT_MAXSALT;
230 	key_len = strlen(key) + (minor >= 'a' ? 1 : 0);
231 
232 	/* Setting up S-Boxes and Subkeys */
233 	Blowfish_initstate(&state);
234 	Blowfish_expandstate(&state, csalt, salt_len,
235 	    (u_int8_t *) key, key_len);
236 	for (k = 0; k < rounds; k++) {
237 		Blowfish_expand0state(&state, (u_int8_t *) key, key_len);
238 		Blowfish_expand0state(&state, csalt, salt_len);
239 	}
240 
241 	/* This can be precomputed later */
242 	j = 0;
243 	for (i = 0; i < BCRYPT_BLOCKS; i++)
244 		cdata[i] = Blowfish_stream2word(ciphertext, 4 * BCRYPT_BLOCKS, &j);
245 
246 	/* Now do the encryption */
247 	for (k = 0; k < 64; k++)
248 		blf_enc(&state, cdata, BCRYPT_BLOCKS / 2);
249 
250 	for (i = 0; i < BCRYPT_BLOCKS; i++) {
251 		ciphertext[4 * i + 3] = cdata[i] & 0xff;
252 		cdata[i] = cdata[i] >> 8;
253 		ciphertext[4 * i + 2] = cdata[i] & 0xff;
254 		cdata[i] = cdata[i] >> 8;
255 		ciphertext[4 * i + 1] = cdata[i] & 0xff;
256 		cdata[i] = cdata[i] >> 8;
257 		ciphertext[4 * i + 0] = cdata[i] & 0xff;
258 	}
259 
260 
261 	i = 0;
262 	encrypted[i++] = '$';
263 	encrypted[i++] = BCRYPT_VERSION;
264 	if (minor)
265 		encrypted[i++] = minor;
266 	encrypted[i++] = '$';
267 
268 	snprintf(encrypted + i, 4, "%2.2u$", logr);
269 
270 	encode_base64((u_int8_t *) encrypted + i + 3, csalt, BCRYPT_MAXSALT);
271 	encode_base64((u_int8_t *) encrypted + strlen(encrypted), ciphertext,
272 	    4 * BCRYPT_BLOCKS - 1);
273 	memset(&state, 0, sizeof(state));
274 	memset(ciphertext, 0, sizeof(ciphertext));
275 	memset(csalt, 0, sizeof(csalt));
276 	memset(cdata, 0, sizeof(cdata));
277 	return encrypted;
278 }
279 
280 static void
281 encode_base64(u_int8_t *buffer, u_int8_t *data, u_int16_t len)
282 {
283 	u_int8_t *bp = buffer;
284 	u_int8_t *p = data;
285 	u_int8_t c1, c2;
286 	while (p < data + len) {
287 		c1 = *p++;
288 		*bp++ = Base64Code[(c1 >> 2)];
289 		c1 = (c1 & 0x03) << 4;
290 		if (p >= data + len) {
291 			*bp++ = Base64Code[c1];
292 			break;
293 		}
294 		c2 = *p++;
295 		c1 |= (c2 >> 4) & 0x0f;
296 		*bp++ = Base64Code[c1];
297 		c1 = (c2 & 0x0f) << 2;
298 		if (p >= data + len) {
299 			*bp++ = Base64Code[c1];
300 			break;
301 		}
302 		c2 = *p++;
303 		c1 |= (c2 >> 6) & 0x03;
304 		*bp++ = Base64Code[c1];
305 		*bp++ = Base64Code[c2 & 0x3f];
306 	}
307 	*bp = '\0';
308 }
309 #if 0
310 void
311 main()
312 {
313 	char    blubber[73];
314 	char    salt[100];
315 	char   *p;
316 	salt[0] = '$';
317 	salt[1] = BCRYPT_VERSION;
318 	salt[2] = '$';
319 
320 	snprintf(salt + 3, 4, "%2.2u$", 5);
321 
322 	printf("24 bytes of salt: ");
323 	fgets(salt + 6, sizeof(salt) - 6, stdin);
324 	salt[99] = 0;
325 	printf("72 bytes of password: ");
326 	fpurge(stdin);
327 	fgets(blubber, sizeof(blubber), stdin);
328 	blubber[72] = 0;
329 
330 	p = crypt(blubber, salt);
331 	printf("Passwd entry: %s\n\n", p);
332 
333 	p = bcrypt_gensalt(5);
334 	printf("Generated salt: %s\n", p);
335 	p = crypt(blubber, p);
336 	printf("Passwd entry: %s\n", p);
337 }
338 #endif
339