/* $NetBSD: crypt-sha1.c,v 1.8.28.1 2021/10/31 14:47:04 martin Exp $ */
/*
* Copyright (c) 2004, Juniper Networks, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#if !defined(lint)
__RCSID("$NetBSD: crypt-sha1.c,v 1.8.28.1 2021/10/31 14:47:04 martin Exp $");
#endif /* not lint */
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <err.h>
#include "crypt.h"
/*
* The default iterations - should take >0s on a fast CPU
* but not be insane for a slow CPU.
*/
#ifndef CRYPT_SHA1_ITERATIONS
# define CRYPT_SHA1_ITERATIONS 24680
#endif
/*
* Support a reasonably? long salt.
*/
#ifndef CRYPT_SHA1_SALT_LENGTH
# define CRYPT_SHA1_SALT_LENGTH 64
#endif
/*
* This may be called from crypt_sha1 or gensalt.
*
* The value returned will be slightly less than <hint> which defaults
* to 24680. The goals are that the number of iterations should take
* non-zero amount of time on a fast cpu while not taking insanely
* long on a slow cpu. The current default will take about 5 seconds
* on a 100MHz sparc, and about 0.04 seconds on a 3GHz i386.
* The number is varied to frustrate those attempting to generate a
* dictionary of pre-computed hashes.
*/
unsigned int
__crypt_sha1_iterations (unsigned int hint)
{
/*
* We treat CRYPT_SHA1_ITERATIONS as a hint.
* Make it harder for someone to pre-compute hashes for a
* dictionary attack by not using the same iteration count for
* every entry.
*/
if (hint < 4)
hint = CRYPT_SHA1_ITERATIONS;
return hint - arc4random_uniform(hint / 4);
}
/*
* UNIX password using hmac_sha1
* This is PBKDF1 from RFC 2898, but using hmac_sha1.
*
* The format of the encrypted password is:
* $<tag>$<iterations>$<salt>$<digest>
*
* where:
* <tag> is "sha1"
* <iterations> is an unsigned int identifying how many rounds
* have been applied to <digest>. The number
* should vary slightly for each password to make
* it harder to generate a dictionary of
* pre-computed hashes. See crypt_sha1_iterations.
* <salt> up to 64 bytes of random data, 8 bytes is
* currently considered more than enough.
* <digest> the hashed password.
*
* NOTE:
* To be FIPS 140 compliant, the password which is used as a hmac key,
* should be between 10 and 20 characters to provide at least 80bits
* strength, and avoid the need to hash it before using as the
* hmac key.
*/
char *
__crypt_sha1 (const char *pw, const char *salt)
{
static const char *magic = SHA1_MAGIC;
static unsigned char hmac_buf[SHA1_SIZE];
static char passwd[(2 * sizeof(SHA1_MAGIC)) +
CRYPT_SHA1_SALT_LENGTH + SHA1_SIZE];
const char *sp;
char *ep;
unsigned long ul;
int sl;
int pl;
int dl;
unsigned int iterations;
unsigned int i;
/* XXX silence -Wpointer-sign (would be nice to fix this some other way) */
const unsigned char *pwu = (const unsigned char *)pw;
/*
* Salt format is
* $<tag>$<iterations>$salt[$]
* If it does not start with $ we use our default iterations.
*/
/* If it starts with the magic string, then skip that */
if (!strncmp(salt, magic, strlen(magic))) {
salt += strlen(magic);
/* and get the iteration count */
iterations = strtoul(salt, &ep, 10);
if (*ep != '$')
return NULL; /* invalid input */
salt = ep + 1; /* skip over the '$' */
} else {
iterations = __crypt_sha1_iterations(0);
}
/* It stops at the next '$', max CRYPT_SHA1_ITERATIONS chars */
for (sp = salt; *sp && *sp != '$' && sp < (salt + CRYPT_SHA1_ITERATIONS); sp++)
continue;
/* Get the length of the actual salt */
sl = sp - salt;
pl = strlen(pw);
/*
* Now get to work...
* Prime the pump with <salt><magic><iterations>
*/
dl = snprintf(passwd, sizeof (passwd), "%.*s%s%u",
sl, salt, magic, iterations);
/*
* Then hmac using <pw> as key, and repeat...
*/
__hmac_sha1((unsigned char *)passwd, dl, pwu, pl, hmac_buf);
for (i = 1; i < iterations; i++) {
__hmac_sha1(hmac_buf, SHA1_SIZE, pwu, pl, hmac_buf);
}
/* Now output... */
pl = snprintf(passwd, sizeof(passwd), "%s%u$%.*s$",
magic, iterations, sl, salt);
ep = passwd + pl;
/* Every 3 bytes of hash gives 24 bits which is 4 base64 chars */
for (i = 0; i < SHA1_SIZE - 3; i += 3) {
ul = (hmac_buf[i+0] << 16) |
(hmac_buf[i+1] << 8) |
hmac_buf[i+2];
__crypt_to64(ep, ul, 4); ep += 4;
}
/* Only 2 bytes left, so we pad with byte0 */
ul = (hmac_buf[SHA1_SIZE - 2] << 16) |
(hmac_buf[SHA1_SIZE - 1] << 8) |
hmac_buf[0];
__crypt_to64(ep, ul, 4); ep += 4;
*ep = '\0';
/* Don't leave anything around in vm they could use. */
explicit_memset(hmac_buf, 0, sizeof hmac_buf);
return passwd;
}