/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2003 Poul-Henning Kamp
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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/types.h>

#include <err.h>
#include <md5.h>
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>

#include "crypt.h"

/*
 * UNIX password
 */

int
crypt_md5(const char *pw, const char *salt, char *buffer)
{
        MD5_CTX ctx,ctx1;
        unsigned long l;
        int sl, pl;
        u_int i;
        u_char final[MD5_SIZE];
        const char *ep;
        static const char *magic = "$1$";

        /* If the salt starts with the magic string, skip that. */
        if (!strncmp(salt, magic, strlen(magic)))
                salt += strlen(magic);

        /* It stops at the first '$', max 8 chars */
        for (ep = salt; *ep && *ep != '$' && ep < salt + 8; ep++)
                continue;

        /* get the length of the true salt */
        sl = ep - salt;

        MD5Init(&ctx);

        /* The password first, since that is what is most unknown */
        MD5Update(&ctx, (const u_char *)pw, strlen(pw));

        /* Then our magic string */
        MD5Update(&ctx, (const u_char *)magic, strlen(magic));

        /* Then the raw salt */
        MD5Update(&ctx, (const u_char *)salt, (u_int)sl);

        /* Then just as many characters of the MD5(pw,salt,pw) */
        MD5Init(&ctx1);
        MD5Update(&ctx1, (const u_char *)pw, strlen(pw));
        MD5Update(&ctx1, (const u_char *)salt, (u_int)sl);
        MD5Update(&ctx1, (const u_char *)pw, strlen(pw));
        MD5Final(final, &ctx1);
        for(pl = (int)strlen(pw); pl > 0; pl -= MD5_SIZE)
                MD5Update(&ctx, (const u_char *)final,
                    (u_int)(pl > MD5_SIZE ? MD5_SIZE : pl));

        /* Don't leave anything around in vm they could use. */
        explicit_bzero(final, sizeof(final));

        /* Then something really weird... */
        for (i = strlen(pw); i; i >>= 1)
                if(i & 1)
                    MD5Update(&ctx, (const u_char *)final, 1);
                else
                    MD5Update(&ctx, (const u_char *)pw, 1);

        /* Now make the output string */
        buffer = stpcpy(buffer, magic);
        buffer = stpncpy(buffer, salt, (u_int)sl);
        *buffer++ = '$';

        MD5Final(final, &ctx);

        /*
         * and now, just to make sure things don't run too fast
         * On a 60 Mhz Pentium this takes 34 msec, so you would
         * need 30 seconds to build a 1000 entry dictionary...
         */
        for(i = 0; i < 1000; i++) {
                MD5Init(&ctx1);
                if(i & 1)
                        MD5Update(&ctx1, (const u_char *)pw, strlen(pw));
                else
                        MD5Update(&ctx1, (const u_char *)final, MD5_SIZE);

                if(i % 3)
                        MD5Update(&ctx1, (const u_char *)salt, (u_int)sl);

                if(i % 7)
                        MD5Update(&ctx1, (const u_char *)pw, strlen(pw));

                if(i & 1)
                        MD5Update(&ctx1, (const u_char *)final, MD5_SIZE);
                else
                        MD5Update(&ctx1, (const u_char *)pw, strlen(pw));
                MD5Final(final, &ctx1);
        }

        l = (final[ 0]<<16) | (final[ 6]<<8) | final[12];
        _crypt_to64(buffer, l, 4); buffer += 4;
        l = (final[ 1]<<16) | (final[ 7]<<8) | final[13];
        _crypt_to64(buffer, l, 4); buffer += 4;
        l = (final[ 2]<<16) | (final[ 8]<<8) | final[14];
        _crypt_to64(buffer, l, 4); buffer += 4;
        l = (final[ 3]<<16) | (final[ 9]<<8) | final[15];
        _crypt_to64(buffer, l, 4); buffer += 4;
        l = (final[ 4]<<16) | (final[10]<<8) | final[ 5];
        _crypt_to64(buffer, l, 4); buffer += 4;
        l = final[11];
        _crypt_to64(buffer, l, 2); buffer += 2;
        *buffer = '\0';

        /* Don't leave anything around in vm they could use. */
        explicit_bzero(final, sizeof(final));

        return (0);
}