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md5crypt.c

/*
 * ----------------------------------------------------------------------------
 * "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
 * ----------------------------------------------------------------------------
 */

/*
 * Ported from FreeBSD to Linux, only minimal changes.  --marekm
 */

#include "config.h"
#include "md5.h"
#include "md5crypt.h"
#include "s_log.h"

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

static unsigned char itoa64[] =           /* 0 ... 63 => ascii - 64 */
      "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

static void
to64(char *s, unsigned long v, int n)
{
      while (--n >= 0) {
            *s++ = itoa64[v&0x3f];
            v >>= 6;
      }
}

/*
 * UNIX password
 *
 * Use MD5 for what it is best at...
 */

/* We need to pull this out for the challenge-response thingy -- asuffield */
char *
get_salt(const char *pw)
{
  static char magic[] = "$1$";
  static char salt[9];
  const char* sp;
  const char* ep;
  int sl;

  /* Refine the Salt first */
  sp = pw;

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

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

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

  /* and format up to return the salt */
  strncpy(salt, sp, sl);
  salt[sl] = '\0';

  return salt;
}

char *
libshadow_md5_crypt(const char *pw, const char *salt)
{
      static char magic[] = "$1$";  /*
                                     * This string is magic for
                                     * this algorithm.  Having
                                     * it this way, we can get
                                     * get better later on
                                     */
      static char     passwd[120], *p;
      static const char *sp,*ep;
      unsigned char     final[16];
      int sl,pl,i,j;
      MD5_CTX     ctx,ctx1;
      unsigned long l;

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

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

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

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

      MD5Init(&ctx);

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

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

      /* Then the raw salt */
      MD5Update(&ctx,(const unsigned char*)sp,sl);

      /* Then just as many characters of the MD5(pw,salt,pw) */
      MD5Init(&ctx1);
      MD5Update(&ctx1,(const unsigned char*)pw,strlen(pw));
      MD5Update(&ctx1,(const unsigned char*)sp,sl);
      MD5Update(&ctx1,(const unsigned char*)pw,strlen(pw));
      MD5Final(final,&ctx1);
      for(pl = strlen(pw); pl > 0; pl -= 16)
            MD5Update(&ctx,final,pl>16 ? 16 : pl);

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

      /* Then something really weird... */
      for (j=0,i = strlen(pw); i ; i >>= 1)
            if(i&1)
                MD5Update(&ctx, final+j, 1);
            else
                MD5Update(&ctx, (const unsigned char*)pw+j, 1);

      /* Now make the output string */
      strcpy(passwd,magic);
      strncat(passwd,sp,sl);
      strcat(passwd,"$");

      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 unsigned char*)pw,strlen(pw));
            else
                  MD5Update(&ctx1,final,16);

            if(i % 3)
                  MD5Update(&ctx1,(const unsigned char*)sp,sl);

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

            if(i & 1)
                  MD5Update(&ctx1,final,16);
            else
                  MD5Update(&ctx1,(const unsigned char*)pw,strlen(pw));
            MD5Final(final,&ctx1);
      }

      p = passwd + strlen(passwd);

      l = (final[ 0]<<16) | (final[ 6]<<8) | final[12]; to64(p,l,4); p += 4;
      l = (final[ 1]<<16) | (final[ 7]<<8) | final[13]; to64(p,l,4); p += 4;
      l = (final[ 2]<<16) | (final[ 8]<<8) | final[14]; to64(p,l,4); p += 4;
      l = (final[ 3]<<16) | (final[ 9]<<8) | final[15]; to64(p,l,4); p += 4;
      l = (final[ 4]<<16) | (final[10]<<8) | final[ 5]; to64(p,l,4); p += 4;
      l =                    final[11]                ; to64(p,l,2); p += 2;
      *p = '\0';

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

      return passwd;
}


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