/*      $NetBSD: md5crypt.c,v 1.16 2024/07/23 22:37:11 riastradh Exp $  */

/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <phk@login.dknet.dk> wrote this file.  As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
 * ----------------------------------------------------------------------------
 *
 * from FreeBSD: crypt.c,v 1.5 1996/10/14 08:34:02 phk Exp
 * via OpenBSD: md5crypt.c,v 1.9 1997/07/23 20:58:27 kstailey Exp
 *
 */

#include <sys/cdefs.h>
#if !defined(lint)
__RCSID("$NetBSD: md5crypt.c,v 1.16 2024/07/23 22:37:11 riastradh Exp $");
#endif /* not lint */

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

#include "crypt.h"

#define MD5_MAGIC       "$1$"
#define MD5_MAGIC_LEN   3

#define INIT(x)                 MD5Init((x))
#define UPDATE(x, b, l)         MD5Update((x), (b), (l))
#define FINAL(v, x)             MD5Final((v), (x))


/*
 * MD5 password encryption.
 */
crypt_private char *
__md5crypt(const char *pw, const char *salt)
{
        static char passwd[120], *p;
        const char *sp, *ep;
        unsigned char final[16];
        unsigned int i, sl, pwl;
        MD5_CTX ctx, ctx1;
        u_int32_t l;
        int pl;

        pwl = strlen(pw);

        /* Refine the salt first */
        sp = salt;

        /* If it starts with the magic string, then skip that */
        if (strncmp(sp, MD5_MAGIC, MD5_MAGIC_LEN) == 0)
                sp += MD5_MAGIC_LEN;

        /* It stops at the first '$', max 8 chars */
        for (ep = sp; *ep != '\0' && *ep != '$' && ep < (sp + 8); ep++)
                continue;

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

        INIT(&ctx);

        /* The password first, since that is what is most unknown */
        UPDATE(&ctx, (const unsigned char *)pw, pwl);

        /* Then our magic string */
        UPDATE(&ctx, (const unsigned char *)MD5_MAGIC, MD5_MAGIC_LEN);

        /* Then the raw salt */
        UPDATE(&ctx, (const unsigned char *)sp, sl);

        /* Then just as many characters of the MD5(pw,salt,pw) */
        INIT(&ctx1);
        UPDATE(&ctx1, (const unsigned char *)pw, pwl);
        UPDATE(&ctx1, (const unsigned char *)sp, sl);
        UPDATE(&ctx1, (const unsigned char *)pw, pwl);
        FINAL(final, &ctx1);

        for (pl = pwl; pl > 0; pl -= 16)
                UPDATE(&ctx, final, (unsigned int)(pl > 16 ? 16 : pl));

        /* Don't leave anything around in vm they could use. */
        memset(final, 0, sizeof(final));

        /* Then something really weird... */
        for (i = pwl; i != 0; i >>= 1)
                if ((i & 1) != 0)
                    UPDATE(&ctx, final, 1);
                else
                    UPDATE(&ctx, (const unsigned char *)pw, 1);

        /* Now make the output string */
        memcpy(passwd, MD5_MAGIC, MD5_MAGIC_LEN);
        strlcpy(passwd + MD5_MAGIC_LEN, sp, sl + 1);
        strlcat(passwd, "$", sizeof(passwd));

        FINAL(final, &ctx);

        /* memset(&ctx, 0, sizeof(ctx)); done by MD5Final() */

        /*
         * 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++) {
                INIT(&ctx1);

                if ((i & 1) != 0)
                        UPDATE(&ctx1, (const unsigned char *)pw, pwl);
                else
                        UPDATE(&ctx1, final, 16);

                if ((i % 3) != 0)
                        UPDATE(&ctx1, (const unsigned char *)sp, sl);

                if ((i % 7) != 0)
                        UPDATE(&ctx1, (const unsigned char *)pw, pwl);

                if ((i & 1) != 0)
                        UPDATE(&ctx1, final, 16);
                else
                        UPDATE(&ctx1, (const unsigned char *)pw, pwl);

                FINAL(final, &ctx1);
        }

        /* memset(&ctx1, 0, sizeof(ctx1)); done by MD5Final() */

        p = passwd + sl + MD5_MAGIC_LEN + 1;

        l = (final[ 0]<<16) | (final[ 6]<<8) | final[12]; __crypt_to64(p,l,4); p += 4;
        l = (final[ 1]<<16) | (final[ 7]<<8) | final[13]; __crypt_to64(p,l,4); p += 4;
        l = (final[ 2]<<16) | (final[ 8]<<8) | final[14]; __crypt_to64(p,l,4); p += 4;
        l = (final[ 3]<<16) | (final[ 9]<<8) | final[15]; __crypt_to64(p,l,4); p += 4;
        l = (final[ 4]<<16) | (final[10]<<8) | final[ 5]; __crypt_to64(p,l,4); p += 4;
        l =                    final[11]                ; __crypt_to64(p,l,2); p += 2;
        *p = '\0';

        /* Don't leave anything around in vm they could use. */
        explicit_memset(final, 0, sizeof(final));
        return (passwd);
}