/*
 * Copyright (c) 1996
 *      Bill Paul <wpaul@ctr.columbia.edu>.  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Bill Paul.
 * 4. Neither the name of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY Bill Paul 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 Bill Paul 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.
 *
 * $FreeBSD: src/usr.sbin/keyserv/crypt_server.c,v 1.6.2.1 2001/07/19 04:21:20 kris Exp $
 */

#include <sys/types.h>
#include <sys/param.h>
#include <dirent.h>
#include <dlfcn.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <rpc/des_crypt.h>
#include <rpc/des.h>
#include "crypt.h"

/*
 * The U.S. government stupidly believes that a) it can keep strong
 * crypto code a secret and b) that doing so somehow protects national
 * interests. It's wrong on both counts, but until it listens to reason
 * we have to make certain compromises so it doesn't have an excuse to
 * throw us in federal prison.
 *
 * Consequently, the core OS ships without DES support, and keyserv
 * defaults to using ARCFOUR with only a 40 bit key, just like nutscrape.
 * This breaks compatibility with Secure RPC on other systems, but it
 * allows Secure RPC to work between FreeBSD systems that don't have the
 * DES package installed without throwing security totally out the window.
 *
 * In order to avoid having to supply two versions of keyserv (one with
 * DES and one without), we use dlopen() and friends to load libdes.so
 * into our address space at runtime. We check for the presence of
 * /usr/lib/libdes.so.3.0 at startup and load it if we find it. If we
 * can't find it, or the __des_crypt symbol doesn't exist, we fall back
 * to the ARCFOUR encryption code. The user can specify another path using
 * the -p flag.
 */

 /* arcfour.h */
typedef struct arcfour_key
{      
   unsigned char state[256];       
   unsigned char x;        
   unsigned char y;
} arcfour_key;

static void prepare_key(unsigned char *key_data_ptr,int key_data_len,
                 arcfour_key *key);
static void arcfour(unsigned char *buffer_ptr,int buffer_len,arcfour_key * key);
static void swap_byte(unsigned char *a, unsigned char *b);

static void
prepare_key(unsigned char *key_data_ptr, int key_data_len, arcfour_key *key)
{
   unsigned char index1;
   unsigned char index2;
   unsigned char* state;
   short counter;     

   state = &key->state[0];         
   for(counter = 0; counter < 256; counter++)              
       state[counter] = counter;
   key->x = 0;     
   key->y = 0;     
   index1 = 0;     
   index2 = 0;             
   for(counter = 0; counter < 256; counter++)      
   {               
      index2 = (key_data_ptr[index1] + state[counter] +
                index2) % 256;                
      swap_byte(&state[counter], &state[index2]);            
      
      index1 = (index1 + 1) % key_data_len;  
   }       
}

static void
arcfour(unsigned char *buffer_ptr, int buffer_len, arcfour_key *key)
{ 
   unsigned char x;
   unsigned char y;
   unsigned char* state;
   unsigned char xorIndex;
   short counter;              
   
   x = key->x;     
   y = key->y;     
   
   state = &key->state[0];         
   for(counter = 0; counter < buffer_len; counter ++)      
   {               
      x = (x + 1) % 256;                      
      y = (state[x] + y) % 256;               
      swap_byte(&state[x], &state[y]);                        
      
      xorIndex = (state[x] + state[y]) % 256;                 
      
      buffer_ptr[counter] ^= state[xorIndex];         
   }               
   key->x = x;     
   key->y = y;
}

static void
swap_byte(unsigned char *a, unsigned char *b)
{
   unsigned char swapByte; 
   
   swapByte = *a; 
   *a = *b;      
   *b = swapByte;
}

/* Dummy _des_crypt function that uses ARCFOUR with a 40 bit key */
int
_arcfour_crypt(char *buf, int len, struct desparams *desp)
{
        struct arcfour_key arcfourk;

        /*
         * U.S. government anti-crypto weasels take
         * note: although we are supplied with a 64 bit
         * key, we're only passing 40 bits to the ARCFOUR
         * encryption code. So there.
         */
        prepare_key(desp->des_key, 5, &arcfourk);
        arcfour(buf, len, &arcfourk);

        return(DESERR_NOHWDEVICE);
}

int (*_my_crypt)(char *, int, struct desparams *) = NULL;

static void *dlhandle;

#ifndef _PATH_USRLIB
#define _PATH_USRLIB "/usr/lib"
#endif

#ifndef LIBCRYPTO
#define LIBCRYPTO "libcrypto.so.1"
#endif

void
load_des(int warn, char *libpath)
{
        char dlpath[MAXPATHLEN];

        if (libpath == NULL) {
                snprintf(dlpath, sizeof(dlpath), "%s/%s", _PATH_USRLIB, LIBCRYPTO);
        } else
                snprintf(dlpath, sizeof(dlpath), "%s", libpath);

        if (dlpath[0] != '\0' && (dlhandle = dlopen(dlpath, 0444)) != NULL)
                _my_crypt = (int (*)())dlsym(dlhandle, "_des_crypt");

        if (_my_crypt == NULL) {
                if (dlhandle != NULL)
                        dlclose(dlhandle);
                _my_crypt = &_arcfour_crypt;
                if (warn) {
                        printf ("DES support disabled -- using ARCFOUR instead.\n");
                        printf ("Warning: ARCFOUR cipher is not compatible with ");
                        printf ("other Secure RPC implementations.\nInstall ");
                        printf ("the FreeBSD 'des' distribution to enable");
                        printf (" DES encryption.\n");
                }
        } else {
                if (warn) {
                        printf ("DES support enabled\n");
                        printf ("Using %s shared object.\n", dlpath);
                }
        }

        return;
}

desresp *
des_crypt_1_svc(desargs *argp, struct svc_req *rqstp)
{
        static desresp  result;
        struct desparams dparm;

        if (argp->desbuf.desbuf_len > DES_MAXDATA) {
                result.stat = DESERR_BADPARAM;
                return(&result);
        }


        bcopy(argp->des_key, dparm.des_key, 8);
        bcopy(argp->des_ivec, dparm.des_ivec, 8);
        dparm.des_mode = argp->des_mode;
        dparm.des_dir = argp->des_dir;
#ifdef BROKEN_DES
        dparm.UDES.UDES_buf = argp->desbuf.desbuf_val;
#endif

        /*
         * XXX This compensates for a bug in the libdes Secure RPC
         * compat interface. (Actually, there are a couple.) The
         * des_ecb_encrypt() routine in libdes only encrypts 8 bytes
         * (64 bits) at a time. However, the Sun Secure RPC ecb_crypt()
         * routine is supposed to be able to handle buffers up to 8Kbytes.
         * The rpc_enc module in libdes ignores this fact and just drops
         * the length parameter on the floor, encrypting only the
         * first 64 bits of whatever buffer you feed it. We deal with
         * this here: if we're using DES encryption, and we're using
         * ECB mode, then we make a pass over the entire buffer
         * ourselves. Note: the rpc_enc module incorrectly transposes
         * the mode flags, so when you ask for CBC mode, you're really
         * getting ECB mode.
         */
#ifdef BROKEN_DES
        if (_my_crypt != &_arcfour_crypt && argp->des_mode == (des_mode)CBC) {
#else
        if (_my_crypt != &_arcfour_crypt && argp->des_mode == ECB) {
#endif
                int                     i;
                char                    *dptr;

                for (i = 0; i < argp->desbuf.desbuf_len / 8; i++) {
                        dptr = argp->desbuf.desbuf_val;
                        dptr += (i * 8);
#ifdef BROKEN_DES
                        dparm.UDES.UDES_buf = dptr;
#endif
                        result.stat = _my_crypt(dptr, 8, &dparm);
                }
        } else {
                result.stat = _my_crypt(argp->desbuf.desbuf_val,
                                        argp->desbuf.desbuf_len,
                                        &dparm);
        }

        if (result.stat == DESERR_NONE || result.stat == DESERR_NOHWDEVICE) {
                bcopy(dparm.des_ivec, result.des_ivec, 8);
                result.desbuf.desbuf_len = argp->desbuf.desbuf_len;
                result.desbuf.desbuf_val = argp->desbuf.desbuf_val;
        }

        return (&result);
}