1 /* $NetBSD: crypt-sha1.c,v 1.3 2006/10/27 18:22:56 drochner Exp $ */ 2 3 /* 4 * Copyright (c) 2004, Juniper Networks, Inc. 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. Neither the name of the copyright holders nor the names of its 16 * contributors may be used to endorse or promote products derived 17 * from this software without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 #if !defined(lint) 34 __RCSID("$NetBSD: crypt-sha1.c,v 1.3 2006/10/27 18:22:56 drochner Exp $"); 35 #endif /* not lint */ 36 37 #include <stdlib.h> 38 #include <unistd.h> 39 #include <stdio.h> 40 #include <string.h> 41 #include <time.h> 42 43 #include <err.h> 44 #include "crypt.h" 45 46 /* 47 * The default iterations - should take >0s on a fast CPU 48 * but not be insane for a slow CPU. 49 */ 50 #ifndef CRYPT_SHA1_ITERATIONS 51 # define CRYPT_SHA1_ITERATIONS 24680 52 #endif 53 /* 54 * Support a reasonably? long salt. 55 */ 56 #ifndef CRYPT_SHA1_SALT_LENGTH 57 # define CRYPT_SHA1_SALT_LENGTH 64 58 #endif 59 60 /* 61 * This may be called from crypt_sha1 or gensalt. 62 * 63 * The value returned will be slightly less than <hint> which defaults 64 * to 24680. The goals are that the number of iterations should take 65 * non-zero amount of time on a fast cpu while not taking insanely 66 * long on a slow cpu. The current default will take about 5 seconds 67 * on a 100MHz sparc, and about 0.04 seconds on a 3GHz i386. 68 * The number is varied to frustrate those attempting to generate a 69 * dictionary of pre-computed hashes. 70 */ 71 unsigned int 72 __crypt_sha1_iterations (unsigned int hint) 73 { 74 static int once = 1; 75 76 /* 77 * We treat CRYPT_SHA1_ITERATIONS as a hint. 78 * Make it harder for someone to pre-compute hashes for a 79 * dictionary attack by not using the same iteration count for 80 * every entry. 81 */ 82 83 if (once) { 84 int pid = getpid(); 85 86 srandom(time(NULL) ^ (pid * pid)); 87 once = 0; 88 } 89 if (hint == 0) 90 hint = CRYPT_SHA1_ITERATIONS; 91 return hint - (random() % (hint / 4)); 92 } 93 94 /* 95 * UNIX password using hmac_sha1 96 * This is PBKDF1 from RFC 2898, but using hmac_sha1. 97 * 98 * The format of the encrypted password is: 99 * $<tag>$<iterations>$<salt>$<digest> 100 * 101 * where: 102 * <tag> is "sha1" 103 * <iterations> is an unsigned int identifying how many rounds 104 * have been applied to <digest>. The number 105 * should vary slightly for each password to make 106 * it harder to generate a dictionary of 107 * pre-computed hashes. See crypt_sha1_iterations. 108 * <salt> up to 64 bytes of random data, 8 bytes is 109 * currently considered more than enough. 110 * <digest> the hashed password. 111 * 112 * NOTE: 113 * To be FIPS 140 compliant, the password which is used as a hmac key, 114 * should be between 10 and 20 characters to provide at least 80bits 115 * strength, and avoid the need to hash it before using as the 116 * hmac key. 117 */ 118 char * 119 __crypt_sha1 (const char *pw, const char *salt) 120 { 121 static const char *magic = SHA1_MAGIC; 122 static unsigned char hmac_buf[SHA1_SIZE]; 123 static char passwd[(2 * sizeof(SHA1_MAGIC)) + 124 CRYPT_SHA1_SALT_LENGTH + SHA1_SIZE]; 125 char *sp; 126 char *ep; 127 unsigned long ul; 128 int sl; 129 int pl; 130 int dl; 131 unsigned int iterations; 132 unsigned int i; 133 134 /* 135 * Salt format is 136 * $<tag>$<iterations>$salt[$] 137 * If it does not start with $ we use our default iterations. 138 */ 139 sp = __UNCONST(salt); 140 141 /* If it starts with the magic string, then skip that */ 142 if (!strncmp(sp, magic, strlen(magic))) { 143 sp += strlen(magic); 144 /* and get the iteration count */ 145 iterations = strtoul(sp, &ep, 10); 146 if (*ep != '$') 147 return NULL; /* invalid input */ 148 sp = ep + 1; /* skip over the '$' */ 149 } else { 150 iterations = __crypt_sha1_iterations(0); 151 } 152 153 /* It stops at the next '$', max CRYPT_SHA1_ITERATIONS chars */ 154 for (ep = sp; *ep && *ep != '$' && ep < (sp + CRYPT_SHA1_ITERATIONS); ep++) 155 continue; 156 157 /* Get the length of the actual salt */ 158 sl = ep - sp; 159 pl = strlen(pw); 160 161 /* 162 * Now get to work... 163 * Prime the pump with <salt><magic><iterations> 164 */ 165 dl = snprintf(passwd, sizeof (passwd), "%.*s%s%u", 166 sl, sp, magic, iterations); 167 /* 168 * Then hmac using <pw> as key, and repeat... 169 */ 170 ep = __UNCONST(pw); /* keep gcc happy */ 171 __hmac_sha1(passwd, dl, ep, pl, hmac_buf); 172 for (i = 1; i < iterations; i++) { 173 __hmac_sha1(hmac_buf, SHA1_SIZE, ep, pl, hmac_buf); 174 } 175 /* Now output... */ 176 pl = snprintf(passwd, sizeof(passwd), "%s%u$%.*s$", 177 magic, iterations, sl, sp); 178 ep = passwd + pl; 179 180 /* Every 3 bytes of hash gives 24 bits which is 4 base64 chars */ 181 for (i = 0; i < SHA1_SIZE - 3; i += 3) { 182 ul = (hmac_buf[i+0] << 16) | 183 (hmac_buf[i+1] << 8) | 184 hmac_buf[i+2]; 185 __crypt_to64(ep, ul, 4); ep += 4; 186 } 187 /* Only 2 bytes left, so we pad with byte0 */ 188 ul = (hmac_buf[SHA1_SIZE - 2] << 16) | 189 (hmac_buf[SHA1_SIZE - 1] << 8) | 190 hmac_buf[0]; 191 __crypt_to64(ep, ul, 4); ep += 4; 192 *ep = '\0'; 193 194 /* Don't leave anything around in vm they could use. */ 195 memset(hmac_buf, 0, sizeof hmac_buf); 196 197 return passwd; 198 } 199