/*
 * Pound - the reverse-proxy load-balancer
 * Copyright (C) 2002-2006 Apsis GmbH
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * Additionaly compiling, linking, and/or using OpenSSL is expressly allowed.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA  02111-1307, USA.
 *
 * Contact information:
 * Apsis GmbH
 * P.O.Box
 * 8707 Uetikon am See
 * Switzerland
 * Tel: +41-44-920 4904
 * EMail: roseg@apsis.ch

 * ====================================================================

 * This module contributed by Pete Shew (pete@shew.org)
 * This will check authorisation and if necessary respond 
 * with a login page.

 * The first version simply asks for the answer to a question specified
 * in the service, but it should easily be possible to check user ID 
 * and passwords against a password file, with permitted users/groups 
 * specified for the servcie 

 */

#include    "pound.h"

static int    auth_send_logon_page(BIO * cl, LISTENER * lstn, char * OrigPage) ;
static int    auth_send_redirect(BIO * cl, LISTENER * lstn, char * OrigPage) ;
static void make_cookie(LISTENER * lstn) ;

void CalculateMD5(unsigned char *buffer, int length, unsigned char *checksum);

static    int            Once = 0 ;
static     regex_t        reCookie ;
static    regmatch_t    matches[5];

/*
  * Called from http.c to check authorisation
  *
  * Check if have received the response to a logon page, and 
  * if so, check the validity of the response. If valid send 
  * a redirect response to the original page with the 
  * cookie and return 0 ;
  * otherwise resend the logon page and return 0 ;
  *
  * If not a logon response, check to see if authentication needed 
  * If not return 1 ;
  *
  * If autherntication needed, check if a valid "pound" cookie
  * is present and if so return 1 or 2
  *
    * NOTE: two cookies are stored and the time of the first. If the first cookie
    * is older than ten minutes, both cookies are discarded. If the first cookie
    * is between five and ten minutes old, any second cookie is discarded, the first
    * becomes the second, and a new first is created and the time noted.
    *
    * Cookie matching is done on either the first or second cookie, and if on the
    * second, a note made to resend the set-cookie with the first one. (RC=2)_
  *
  * Otherwise send the login page and return 0.
*/

int
auth_check(
    BIO *       cl,
    LISTENER *  lstn,
    char **     headers)
{
    int         n ;
    int         GoodCookie = 0 ;
    int         RC = 1 ; /* default is carry on */
    char    *   HisCookie ;
    char    *   Ptr ;

    /* Do this once the first time in */
    if (Once == 0) {
        Once = 1 ;
        if (regcomp(&reCookie, "PoundAuth=([^;]+)", REG_NEWLINE | REG_EXTENDED))
        {
            logmsg(LOG_ERR, "bad PoundAuthCookie Regex - aborted");
            exit(1);
        }
    }

    /* Check for a login response */
    Ptr = strstr(headers[0], "/auth.pound?response=") ;
    if (Ptr) {
        char    Request[MAXBUF] ;
        char    *Response, *OrigReq ;
        char *    Ptr2 ;

        strcpy (Request, headers[0]) ;
        Response = Ptr + (Request-headers[0]) + 21 ;
        OrigReq = strchr(Response, '&') ;
        *(OrigReq++) = '\0' ;
        OrigReq = strchr(OrigReq, '=') + 1 ;
        Ptr = strchr(OrigReq, ' ') ;
        *Ptr = '\0' ;

        /* Urldecode */
        for (Ptr2=Ptr=OrigReq; *Ptr; Ptr++, Ptr2++) {
            if (*Ptr == '+') {
                *Ptr2 = ' ' ;
            } else if (*Ptr == '%') {
                char c1 = *(++Ptr) - '0' ;
                if (c1 > 9) c1 -= 7 ;
                char c2 = *(++Ptr) - '0' ;
                if (c2 > 9) c2 -= 7 ;
                *Ptr2 = c1*16+c2 ;
            } else {
                *Ptr2 = *Ptr ;
            }
        }
        *Ptr2 = '\0' ;

        if (strcmp(Response, lstn->response)==0) {
            make_cookie(lstn) ;
            auth_send_redirect(cl, lstn, OrigReq) ;
            RC = 0 ;
        } else {
            auth_send_logon_page(cl, lstn, OrigReq) ;
            RC = 0 ;
        }
    /* Check if we need authentication */
    } else if ((lstn->question != NULL) && (lstn->response != NULL)) {
        /* Make up a cookie that should match his cookie */
        int len, outlen ;

        make_cookie(lstn) ;

        /* Now look for a cookie */
        for(n = 1; n < MAXHEADERS && headers[n]; n++) {
            if (strncasecmp(headers[n], "Cookie:", 7)==0)    {
                GoodCookie = 1 ; /* Maybe */
                break ;
            }
        }

        /* we found a cookie header */
        if (GoodCookie) {
            /* One time create the regex */
            /* Look for our cookie and extract it */
            if(!regexec(&reCookie, headers[n], 4, matches, 0)) {
                char    Work1[256] ;

                len = matches[1].rm_eo - matches[1].rm_so ;
                strncpy(Work1, &(headers[n][matches[1].rm_so]), len) ;
                Work1[len] = '\0' ;
                if ((lstn->cookie1) && (strcmp(lstn->cookie1, Work1)==0))    /* Check it's OK */
                    GoodCookie = 1 ;
                else  if ((lstn->cookie2) && (strcmp(lstn->cookie2, Work1)==0))    /* Check it's OK */
                    GoodCookie = 2 ;
                else
                    GoodCookie = 0 ;
            } else {
                GoodCookie = 0 ;
            }
        }

        /* Now, did we find a cookie that looked good to us? */
        /* if not we need to send the login screen */
        if (GoodCookie == 0) {
            auth_send_logon_page(cl, lstn, headers[0]) ;
        }
        RC = GoodCookie ;
    }
    return RC ; /* 0=stop processing, 1=carry on, 2= carry on and set cookie */
}

/* Generate and send the logon response */

int auth_send_logon_page(BIO * cl, LISTENER * lstn, char* OrigPage)
{
    BIO_printf(cl, "HTTP/1.1 200 OK\r\n");
    BIO_printf(cl, "Server:    Pound\r\n");
    BIO_printf(cl, "Date: Thu, 15th Feb 2007 11:32:22 GMT\r\n");
    BIO_printf(cl, "Connection: keepalive\r\n");
    BIO_printf(cl, "Content-Type: text/html;charset=ISO-8859-1\r\n");
    BIO_printf(cl, "Cache-Control: no-cache\r\n");
    BIO_printf(cl, "\r\n");
    BIO_printf(cl, "<html><head><title>Pound authorisation</title></head>\r\n");
    BIO_printf(cl, "<body>\r\n");
    BIO_printf(cl, "<div align='center'><h1>Secure logon</h1>\r\n<p>Please supply the answer to the following question</p>\r\n");
    BIO_printf(cl, "<form action='/auth.pound'>\r\n");
    BIO_printf(cl, "<h2>");
    BIO_printf(cl, lstn->question);
    BIO_printf(cl, "</h2>\r\n");
    BIO_printf(cl, "<input type='password' name='response' value=''><br>\r\n");
    BIO_printf(cl, "<input type='hidden' name='origpage' value='");
    BIO_printf(cl, OrigPage);
    BIO_printf(cl, "'>\r\n");
    BIO_printf(cl, "<input type='submit' value='Login'>\r\n");
    BIO_printf(cl, "</form>\r\n");
    BIO_printf(cl, "</div>\r\n");
    BIO_printf(cl, "</body></html>\r\n");
    BIO_flush(cl);
    return 1 ;
}

/* Generate and send the redirect with the cookie */

int auth_send_redirect(BIO * cl, LISTENER * lstn, char * OrigReq)
{
    char    *    OrigPage ;
    char    *    Ptr ;

    OrigPage = OrigReq ;
    while (*OrigPage!=' ') OrigPage++ ;
    while (*OrigPage==' ') OrigPage++ ;
    Ptr = OrigPage + 1 ;
    while (*Ptr!=' ') Ptr++ ;
    *Ptr='\0' ;

    BIO_printf(cl, "HTTP/1.1 302 OK\r\n");
    BIO_printf(cl, "Server:    Pound\r\n");
    BIO_printf(cl, "Date: Thu, 15th Feb 2007 11:32:22 GMT\r\n");
    BIO_printf(cl, "Connection: keepalive\r\n");
    BIO_printf(cl, "location: %s\r\n", OrigPage);
    BIO_printf(cl, "Content-Type: text/html;charset=ISO-8859-1\r\n");
    BIO_printf(cl, "Cache-Control: no-cache\r\n");
    BIO_printf(cl, "Set-Cookie: PoundAuth=%s\r\n", lstn->cookie1) ;
    BIO_printf(cl, "\r\n");
    BIO_printf(cl, "<html><head><title>Pound authorisation</title></head>\r\n");
    BIO_printf(cl, "<body>\r\n");
    BIO_printf(cl, "<p>Authorisation accepted</p>\r\n");
    BIO_printf(cl, "</body></html>\r\n");
    BIO_flush(cl);
    return 1 ;
}

void make_cookie(LISTENER * lstn)
{
    time_t    Now = time(&Now) ;
    int        len, outlen ;
    if ((lstn->cookie1 == NULL) || (lstn->cookietime + 300 < Now)) {
        char    Work1[256] ;
        char    Work2[256] ;

        if (lstn->cookie2) {
            free (lstn->cookie2) ;
            lstn->cookie2 = NULL ;
        }

        if ((lstn->cookie1) && (lstn->cookietime + 600 < Now)) {
            free (lstn->cookie1) ;
            lstn->cookie1 = NULL ;
        } else {
            lstn->cookie2 = lstn->cookie1 ;
        }

        lstn->cookietime = Now ;
        strcpy(Work1, ctime(&lstn->cookietime)) ;
        strcat(Work1, lstn->question) ;
        strcat(Work1, "$%^$&%$^&$") ;  /* A bit of confusion */
        strcat(Work1, lstn->response) ;
        strcat(Work1, "$%^$&%$^&$") ;  /* A bit more of confusion */
        len = strlen(Work1) ;

        CalculateMD5((unsigned char*) Work1, len, (unsigned char*) Work2);

        if ((lstn->cookie1 = strdup(Work2))==NULL) {
            logmsg(LOG_ERR, "check_auth: out of memory - aborted");
            exit(1);
        }
    }
}

/*
 * I know there are other ways, but I didn't want to increase the
 * dependency for the sake of a little bit of code
 *
 * PETE SHEW
*/

/* Taken from ReHash (www.reichlsoft.de.vu) and released
 * under GPL/LGPL with permission from ReHash author
 * Dominik Reichl <dominik.reichl@t-online.de>, Germany
 */

/*
 **********************************************************************
 ** MD5.cpp                                                          **
 **                                                                  **
 ** - Style modified by Tony Ray, January 2001                       **
 **   Added support for randomizing initialization constants         **
 ** - Style modified by Dominik Reichl, April 2003                   **
 **   Optimized code                                                 **
 **                                                                  **
 ** MD5.c                                                            **
 ** RSA Data Security, Inc. MD5 Message Digest Algorithm             **
 ** Created: 2/17/90 RLR                                             **
 ** Revised: 1/91 SRD,AJ,BSK,JT Reference C Version                  **
 **********************************************************************
 */

/*
 **********************************************************************
 ** MD5.h -- Header file for implementation of MD5                   **
 ** RSA Data Security, Inc. MD5 Message Digest Algorithm             **
 ** Created: 2/17/90 RLR                                             **
 ** Revised: 12/27/90 SRD,AJ,BSK,JT Reference C version              **
 ** Revised (for MD5): RLR 4/27/91                                   **
 **   -- G modified to have y&~z instead of y&z                      **
 **   -- FF, GG, HH modified to add in last register done            **
 **   -- Access pattern: round 2 works mod 5, round 3 works mod 3    **
 **   -- distinct additive constant for each step                    **
 **   -- round 4 added, working mod 7                                **
 **********************************************************************
 */

/* Typedef a 32 bit type */
#ifndef UINT4
typedef unsigned long int UINT4;
#endif

/* Data structure for MD5 (Message Digest) computation */
typedef struct {
    UINT4           i[2];           /* Number of _bits_ handled mod 2^64    */
    UINT4           buf[4];         /* Scratch buffer                       */
    unsigned char   in[64];         /* Input buffer                         */
    unsigned char   digest[16];     /* Actual digest after MD5Final call    */
} MD5_CTX;

/* Padding */
static unsigned char MD5_PADDING[64] = {
    0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};

/* MD5_F, MD5_G and MD5_H are basic MD5 functions: selection, majority, parity */
#define MD5_F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define MD5_G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define MD5_H(x, y, z) ((x) ^ (y) ^ (z))
#define MD5_I(x, y, z) ((y) ^ ((x) | (~z)))

/* ROTATE_LEFT rotates x left n bits */
#ifndef ROTATE_LEFT
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))
#endif

/* MD5_FF, MD5_GG, MD5_HH, and MD5_II transformations for rounds 1, 2, 3, and 4 */
/* Rotation is separate from addition to prevent recomputation */
#define MD5_FF(a, b, c, d, x, s, ac) {(a) += MD5_F ((b), (c), (d)) + (x) + (UINT4)(ac); (a) = ROTATE_LEFT ((a), (s)); (a) += (b); }
#define MD5_GG(a, b, c, d, x, s, ac) {(a) += MD5_G ((b), (c), (d)) + (x) + (UINT4)(ac); (a) = ROTATE_LEFT ((a), (s)); (a) += (b); }
#define MD5_HH(a, b, c, d, x, s, ac) {(a) += MD5_H ((b), (c), (d)) + (x) + (UINT4)(ac); (a) = ROTATE_LEFT ((a), (s)); (a) += (b); }
#define MD5_II(a, b, c, d, x, s, ac) {(a) += MD5_I ((b), (c), (d)) + (x) + (UINT4)(ac); (a) = ROTATE_LEFT ((a), (s)); (a) += (b); }

/* Constants for transformation */
#define MD5_S11 7  /* Round 1 */
#define MD5_S12 12
#define MD5_S13 17
#define MD5_S14 22
#define MD5_S21 5  /* Round 2 */
#define MD5_S22 9
#define MD5_S23 14
#define MD5_S24 20
#define MD5_S31 4  /* Round 3 */
#define MD5_S32 11
#define MD5_S33 16
#define MD5_S34 23
#define MD5_S41 6  /* Round 4 */
#define MD5_S42 10
#define MD5_S43 15
#define MD5_S44 21

/* Basic MD5 step. MD5_Transform buf based on in */
static void MD5_Transform (UINT4 *buf, UINT4 *in)
{
    UINT4 a = buf[0], b = buf[1], c = buf[2], d = buf[3];

    /* Round 1 */
    MD5_FF ( a, b, c, d, in[ 0], MD5_S11, (UINT4) 3614090360u); /* 1 */
    MD5_FF ( d, a, b, c, in[ 1], MD5_S12, (UINT4) 3905402710u); /* 2 */
    MD5_FF ( c, d, a, b, in[ 2], MD5_S13, (UINT4)  606105819u); /* 3 */
    MD5_FF ( b, c, d, a, in[ 3], MD5_S14, (UINT4) 3250441966u); /* 4 */
    MD5_FF ( a, b, c, d, in[ 4], MD5_S11, (UINT4) 4118548399u); /* 5 */
    MD5_FF ( d, a, b, c, in[ 5], MD5_S12, (UINT4) 1200080426u); /* 6 */
    MD5_FF ( c, d, a, b, in[ 6], MD5_S13, (UINT4) 2821735955u); /* 7 */
    MD5_FF ( b, c, d, a, in[ 7], MD5_S14, (UINT4) 4249261313u); /* 8 */
    MD5_FF ( a, b, c, d, in[ 8], MD5_S11, (UINT4) 1770035416u); /* 9 */
    MD5_FF ( d, a, b, c, in[ 9], MD5_S12, (UINT4) 2336552879u); /* 10 */
    MD5_FF ( c, d, a, b, in[10], MD5_S13, (UINT4) 4294925233u); /* 11 */
    MD5_FF ( b, c, d, a, in[11], MD5_S14, (UINT4) 2304563134u); /* 12 */
    MD5_FF ( a, b, c, d, in[12], MD5_S11, (UINT4) 1804603682u); /* 13 */
    MD5_FF ( d, a, b, c, in[13], MD5_S12, (UINT4) 4254626195u); /* 14 */
    MD5_FF ( c, d, a, b, in[14], MD5_S13, (UINT4) 2792965006u); /* 15 */
    MD5_FF ( b, c, d, a, in[15], MD5_S14, (UINT4) 1236535329u); /* 16 */

    /* Round 2 */
    MD5_GG ( a, b, c, d, in[ 1], MD5_S21, (UINT4) 4129170786u); /* 17 */
    MD5_GG ( d, a, b, c, in[ 6], MD5_S22, (UINT4) 3225465664u); /* 18 */
    MD5_GG ( c, d, a, b, in[11], MD5_S23, (UINT4)  643717713u); /* 19 */
    MD5_GG ( b, c, d, a, in[ 0], MD5_S24, (UINT4) 3921069994u); /* 20 */
    MD5_GG ( a, b, c, d, in[ 5], MD5_S21, (UINT4) 3593408605u); /* 21 */
    MD5_GG ( d, a, b, c, in[10], MD5_S22, (UINT4)   38016083u); /* 22 */
    MD5_GG ( c, d, a, b, in[15], MD5_S23, (UINT4) 3634488961u); /* 23 */
    MD5_GG ( b, c, d, a, in[ 4], MD5_S24, (UINT4) 3889429448u); /* 24 */
    MD5_GG ( a, b, c, d, in[ 9], MD5_S21, (UINT4)  568446438u); /* 25 */
    MD5_GG ( d, a, b, c, in[14], MD5_S22, (UINT4) 3275163606u); /* 26 */
    MD5_GG ( c, d, a, b, in[ 3], MD5_S23, (UINT4) 4107603335u); /* 27 */
    MD5_GG ( b, c, d, a, in[ 8], MD5_S24, (UINT4) 1163531501u); /* 28 */
    MD5_GG ( a, b, c, d, in[13], MD5_S21, (UINT4) 2850285829u); /* 29 */
    MD5_GG ( d, a, b, c, in[ 2], MD5_S22, (UINT4) 4243563512u); /* 30 */
    MD5_GG ( c, d, a, b, in[ 7], MD5_S23, (UINT4) 1735328473u); /* 31 */
    MD5_GG ( b, c, d, a, in[12], MD5_S24, (UINT4) 2368359562u); /* 32 */

    /* Round 3 */
    MD5_HH ( a, b, c, d, in[ 5], MD5_S31, (UINT4) 4294588738u); /* 33 */
    MD5_HH ( d, a, b, c, in[ 8], MD5_S32, (UINT4) 2272392833u); /* 34 */
    MD5_HH ( c, d, a, b, in[11], MD5_S33, (UINT4) 1839030562u); /* 35 */
    MD5_HH ( b, c, d, a, in[14], MD5_S34, (UINT4) 4259657740u); /* 36 */
    MD5_HH ( a, b, c, d, in[ 1], MD5_S31, (UINT4) 2763975236u); /* 37 */
    MD5_HH ( d, a, b, c, in[ 4], MD5_S32, (UINT4) 1272893353u); /* 38 */
    MD5_HH ( c, d, a, b, in[ 7], MD5_S33, (UINT4) 4139469664u); /* 39 */
    MD5_HH ( b, c, d, a, in[10], MD5_S34, (UINT4) 3200236656u); /* 40 */
    MD5_HH ( a, b, c, d, in[13], MD5_S31, (UINT4)  681279174u); /* 41 */
    MD5_HH ( d, a, b, c, in[ 0], MD5_S32, (UINT4) 3936430074u); /* 42 */
    MD5_HH ( c, d, a, b, in[ 3], MD5_S33, (UINT4) 3572445317u); /* 43 */
    MD5_HH ( b, c, d, a, in[ 6], MD5_S34, (UINT4)   76029189u); /* 44 */
    MD5_HH ( a, b, c, d, in[ 9], MD5_S31, (UINT4) 3654602809u); /* 45 */
    MD5_HH ( d, a, b, c, in[12], MD5_S32, (UINT4) 3873151461u); /* 46 */
    MD5_HH ( c, d, a, b, in[15], MD5_S33, (UINT4)  530742520u); /* 47 */
    MD5_HH ( b, c, d, a, in[ 2], MD5_S34, (UINT4) 3299628645u); /* 48 */

    /* Round 4 */
    MD5_II ( a, b, c, d, in[ 0], MD5_S41, (UINT4) 4096336452u); /* 49 */
    MD5_II ( d, a, b, c, in[ 7], MD5_S42, (UINT4) 1126891415u); /* 50 */
    MD5_II ( c, d, a, b, in[14], MD5_S43, (UINT4) 2878612391u); /* 51 */
    MD5_II ( b, c, d, a, in[ 5], MD5_S44, (UINT4) 4237533241u); /* 52 */
    MD5_II ( a, b, c, d, in[12], MD5_S41, (UINT4) 1700485571u); /* 53 */
    MD5_II ( d, a, b, c, in[ 3], MD5_S42, (UINT4) 2399980690u); /* 54 */
    MD5_II ( c, d, a, b, in[10], MD5_S43, (UINT4) 4293915773u); /* 55 */
    MD5_II ( b, c, d, a, in[ 1], MD5_S44, (UINT4) 2240044497u); /* 56 */
    MD5_II ( a, b, c, d, in[ 8], MD5_S41, (UINT4) 1873313359u); /* 57 */
    MD5_II ( d, a, b, c, in[15], MD5_S42, (UINT4) 4264355552u); /* 58 */
    MD5_II ( c, d, a, b, in[ 6], MD5_S43, (UINT4) 2734768916u); /* 59 */
    MD5_II ( b, c, d, a, in[13], MD5_S44, (UINT4) 1309151649u); /* 60 */
    MD5_II ( a, b, c, d, in[ 4], MD5_S41, (UINT4) 4149444226u); /* 61 */
    MD5_II ( d, a, b, c, in[11], MD5_S42, (UINT4) 3174756917u); /* 62 */
    MD5_II ( c, d, a, b, in[ 2], MD5_S43, (UINT4)  718787259u); /* 63 */
    MD5_II ( b, c, d, a, in[ 9], MD5_S44, (UINT4) 3951481745u); /* 64 */

    buf[0] += a;
    buf[1] += b;
    buf[2] += c;
    buf[3] += d;
}

// Set pseudoRandomNumber to zero for RFC MD5 implementation
void MD5Init (MD5_CTX *mdContext, unsigned long pseudoRandomNumber)
{
    mdContext->i[0] = mdContext->i[1] = (UINT4)0;

    /* Load magic initialization constants */
    mdContext->buf[0] = (UINT4)0x67452301 + (pseudoRandomNumber * 11);
    mdContext->buf[1] = (UINT4)0xefcdab89 + (pseudoRandomNumber * 71);
    mdContext->buf[2] = (UINT4)0x98badcfe + (pseudoRandomNumber * 37);
    mdContext->buf[3] = (UINT4)0x10325476 + (pseudoRandomNumber * 97);
}

void MD5Update (MD5_CTX *mdContext, unsigned char *inBuf, unsigned int inLen)
{
    UINT4           in[16];
    int             mdi = 0;
    unsigned int    i = 0, ii = 0;

    /* Compute number of bytes mod 64 */
    mdi = (int)((mdContext->i[0] >> 3) & 0x3F);

    /* Update number of bits */
    if ((mdContext->i[0] + ((UINT4)inLen << 3)) < mdContext->i[0]) mdContext->i[1]++;
    mdContext->i[0] += ((UINT4)inLen << 3);
    mdContext->i[1] += ((UINT4)inLen >> 29);

    while (inLen--) {
        /* Add new character to buffer, increment mdi */
        mdContext->in[mdi++] = *inBuf++;

        /* Transform if necessary */
        if (mdi == 0x40) {
            for (i = 0, ii = 0; i < 16; i++, ii += 4)
                in[i] = (((UINT4)mdContext->in[ii+3]) << 24) |
                        (((UINT4)mdContext->in[ii+2]) << 16) |
                        (((UINT4)mdContext->in[ii+1]) << 8) |
                        ((UINT4)mdContext->in[ii]);

            MD5_Transform (mdContext->buf, in);
            mdi = 0;
        }
    }
}

void MD5Final (MD5_CTX *mdContext)
{
    UINT4           in[16];
    int             mdi = 0;
    unsigned int    i = 0, ii = 0, padLen = 0;

    /* Save number of bits */
    in[14] = mdContext->i[0];
    in[15] = mdContext->i[1];

    /* Compute number of bytes mod 64 */
    mdi = (int)((mdContext->i[0] >> 3) & 0x3F);

    /* Pad out to 56 mod 64 */
    padLen = (mdi < 56) ? (56 - mdi) : (120 - mdi);
    MD5Update (mdContext, MD5_PADDING, padLen);

    /* Append length in bits and transform */
    for (i = 0, ii = 0; i < 14; i++, ii += 4)
        in[i] = (((UINT4)mdContext->in[ii+3]) << 24) |
                (((UINT4)mdContext->in[ii+2]) << 16) |
                (((UINT4)mdContext->in[ii+1]) <<  8) |
                ((UINT4)mdContext->in[ii]);
    MD5_Transform (mdContext->buf, in);

    /* Store buffer in digest */
    for (i = 0, ii = 0; i < 4; i++, ii += 4) {
        mdContext->digest[ii]   = (unsigned char)( mdContext->buf[i]        & 0xFF);
        mdContext->digest[ii+1] = (unsigned char)((mdContext->buf[i] >>  8) & 0xFF);
        mdContext->digest[ii+2] = (unsigned char)((mdContext->buf[i] >> 16) & 0xFF);
        mdContext->digest[ii+3] = (unsigned char)((mdContext->buf[i] >> 24) & 0xFF);
    }
}

void CalculateMD5(unsigned char *buffer, int length, unsigned char *checksum)
{
    int             i;
    MD5_CTX         m_md5;

    MD5Init(&m_md5, 0);
    MD5Update(&m_md5, buffer, length);
    MD5Final(&m_md5);

    for (i = 0; i < 16; i++) sprintf((char*) checksum+i*2,"%02X", m_md5.digest[i]);
}