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//==========================================================================
//
//      ./lib/current/src/scapi.c
//
//
//==========================================================================
//####ECOSGPLCOPYRIGHTBEGIN####
// -------------------------------------------
// This file is part of eCos, the Embedded Configurable Operating System.
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
//
// eCos 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 or (at your option) any later version.
//
// eCos 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 eCos; if not, write to the Free Software Foundation, Inc.,
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
//
// As a special exception, if other files instantiate templates or use macros
// or inline functions from this file, or you compile this file and link it
// with other works to produce a work based on this file, this file does not
// by itself cause the resulting work to be covered by the GNU General Public
// License. However the source code for this file must still be made available
// in accordance with section (3) of the GNU General Public License.
//
// This exception does not invalidate any other reasons why a work based on
// this file might be covered by the GNU General Public License.
//
// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
// at http://sources.redhat.com/ecos/ecos-license/
// -------------------------------------------
//####ECOSGPLCOPYRIGHTEND####
//####UCDSNMPCOPYRIGHTBEGIN####
//
// -------------------------------------------
//
// Portions of this software may have been derived from the UCD-SNMP
// project,  <http://ucd-snmp.ucdavis.edu/>  from the University of
// California at Davis, which was originally based on the Carnegie Mellon
// University SNMP implementation.  Portions of this software are therefore
// covered by the appropriate copyright disclaimers included herein.
//
// The release used was version 4.1.2 of May 2000.  "ucd-snmp-4.1.2"
// -------------------------------------------
//
//####UCDSNMPCOPYRIGHTEND####
//==========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):    hmt
// Contributors: hmt
// Date:         2000-05-30
// Purpose:      Port of UCD-SNMP distribution to eCos.
// Description:  
//              
//
//####DESCRIPTIONEND####
//
//==========================================================================
/********************************************************************
       Copyright 1989, 1991, 1992 by Carnegie Mellon University
 
			  Derivative Work -
Copyright 1996, 1998, 1999, 2000 The Regents of the University of California
 
			 All Rights Reserved
 
Permission to use, copy, modify and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appears in all copies and
that both that copyright notice and this permission notice appear in
supporting documentation, and that the name of CMU and The Regents of
the University of California not be used in advertising or publicity
pertaining to distribution of the software without specific written
permission.
 
CMU AND THE REGENTS OF THE UNIVERSITY OF CALIFORNIA DISCLAIM ALL
WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL CMU OR
THE REGENTS OF THE UNIVERSITY OF CALIFORNIA BE LIABLE FOR ANY SPECIAL,
INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
FROM THE LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*********************************************************************/
/*
 * scapi.c
 *
 */
 
#include <config.h>
 
#ifdef CYGPKG_SNMPAGENT_V3_SUPPORT
#include <sys/types.h>
#if HAVE_WINSOCK_H
#include <winsock.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#if HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif
#if TIME_WITH_SYS_TIME
# ifdef WIN32
#  include <sys/timeb.h>
# else
#  include <sys/time.h>
# endif
# include <time.h>
#else
# if HAVE_SYS_TIME_H
#  include <sys/time.h>
# else
#  include <time.h>
# endif
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
 
#ifdef USE_INTERNAL_MD5
#include "md5.h"
#endif
#include "asn1.h"
#include "tools.h"
#include "snmp_api.h"
#include "callback.h"
#include "snmpusm.h"
#include "keytools.h"
#include "snmp_debug.h"
#include "scapi.h"
#include "snmp_impl.h"
#include "system.h"
 
#include "transform_oids.h"
 
#ifdef USE_OPENSSL
#include <openssl/hmac.h>
#include <openssl/evp.h>
#include <openssl/rand.h>
#endif
 
#ifdef QUITFUN
#undef QUITFUN
#define QUITFUN(e, l)					\
	if (e != SNMPERR_SUCCESS) {			\
		rval = SNMPERR_SC_GENERAL_FAILURE;	\
		goto l ;				\
	}
#endif
 
 
/*
  sc_get_properlength(oid *hashtype, u_int hashtype_len):
 
  Given a hashing type ("hashtype" and its length hashtype_len), return
  the length of the hash result.
 
  Returns either the length or SNMPERR_GENERR for an unknown hashing type.
*/
int
sc_get_properlength(oid *hashtype, u_int hashtype_len)
{
  DEBUGTRACE;
  /*
   * Determine transform type hash length.
   */
  if ( ISTRANSFORM(hashtype, HMACMD5Auth)) {
    return BYTESIZE(SNMP_TRANS_AUTHLEN_HMACMD5);
  }
  else if ( ISTRANSFORM(hashtype, HMACSHA1Auth) ) {
    return BYTESIZE(SNMP_TRANS_AUTHLEN_HMACSHA1);
  }
  return SNMPERR_GENERR;
}
 
 
/*******************************************************************-o-******
 * sc_init
 *
 * Returns:
 *	SNMPERR_SUCCESS			Success.
 */
int
sc_init(void)
{
  int		rval = SNMPERR_SUCCESS;
 
#ifndef USE_OPENSSL
#ifdef USE_INTERNAL_MD5
  struct timeval tv;
 
  DEBUGTRACE;
 
  gettimeofday(&tv,(struct timezone *)0);
 
  srandom(tv.tv_sec ^ tv.tv_usec);
#else
  rval = SNMPERR_SC_NOT_CONFIGURED;
#endif
  /* XXX ogud: The only reason to do anything here with openssl is to 
   * XXX ogud: seed random number generator 
   */
#endif  /* ifndef USE_OPENSSL */
	return rval;
}  /* end sc_init() */
 
/*******************************************************************-o-******
 * sc_random
 *
 * Parameters:
 *	*buf		Pre-allocated buffer.
 *	*buflen 	Size of buffer.
 *      
 * Returns:
 *	SNMPERR_SUCCESS			Success.
 */
int
sc_random(u_char *buf, size_t *buflen)
#if defined(USE_INTERNAL_MD5) || defined(USE_OPENSSL)
{
  int		rval = SNMPERR_SUCCESS;
#ifdef USE_INTERNAL_MD5
  int i;
  int rndval;
  u_char *ucp = buf;
#endif
 
  DEBUGTRACE;
 
#ifdef USE_OPENSSL
  RAND_bytes(buf, *buflen); /* will never fail */
#else	/* USE_INTERNAL_MD5 */
  /* fill the buffer with random integers.  Note that random()
     is defined in config.h and may not be truly the random()
     system call if something better existed */
  rval = *buflen - *buflen%sizeof(rndval);
  for(i = 0; i < rval; i += sizeof(rndval)) {
    rndval = random();
    memcpy(ucp, &rndval, sizeof(rndval));
    ucp += sizeof(rndval);
  }
 
  rndval = random();
  memcpy(ucp, &rndval, *buflen%sizeof(rndval));
 
  rval = SNMPERR_SUCCESS;
#endif  /* USE_OPENSSL */
  return rval;
 
}  /* end sc_random() */
 
#else
_SCAPI_NOT_CONFIGURED
#endif							/*  */
 
 
 
/*******************************************************************-o-******
 * sc_generate_keyed_hash
 *
 * Parameters:
 *	 authtype	Type of authentication transform.
 *	 authtypelen
 *	*key		Pointer to key (Kul) to use in keyed hash.
 *	 keylen		Length of key in bytes.
 *	*message	Pointer to the message to hash.
 *	 msglen		Length of the message.
 *	*MAC		Will be returned with allocated bytes containg hash.
 *	*maclen		Length of the hash buffer in bytes; also indicates
 *				whether the MAC should be truncated.
 *      
 * Returns:
 *	SNMPERR_SUCCESS			Success.
 *	SNMPERR_GENERR			All errs
 *
 *
 * A hash of the first msglen bytes of message using a keyed hash defined
 * by authtype is created and stored in MAC.  MAC is ASSUMED to be a buffer
 * of at least maclen bytes.  If the length of the hash is greater than
 * maclen, it is truncated to fit the buffer.  If the length of the hash is
 * less than maclen, maclen set to the number of hash bytes generated.
 *
 * ASSUMED that the number of hash bits is a multiple of 8.
 */
int
sc_generate_keyed_hash(	oid	*authtype,	size_t authtypelen,
			u_char	*key,		u_int  keylen,
			u_char	*message,	u_int  msglen,
			u_char	*MAC,		size_t *maclen)
#if  defined(USE_INTERNAL_MD5) || defined(USE_OPENSSL)
{
  int		 rval	 = SNMPERR_SUCCESS;
  int		 properlength;
 
  u_char	 buf[SNMP_MAXBUF_SMALL];
#if  defined(USE_OPENSSL)
  int		 buf_len = sizeof(buf);
  u_char	*bufp = buf;
#endif
 
  DEBUGTRACE;
 
#ifdef SNMP_TESTING_CODE
{
  int i;
  DEBUGMSG(("sc_generate_keyed_hash", "sc_generate_keyed_hash(): key=0x"));
  for(i=0; i< keylen; i++)
    DEBUGMSG(("sc_generate_keyed_hash", "%02x", key[i] & 0xff));
  DEBUGMSG(("sc_generate_keyed_hash"," (%d)\n", keylen));
}
#endif /* SNMP_TESTING_CODE */
 
/*
 * Sanity check.
 */
 if ( !authtype || !key || !message || !MAC || !maclen
      || (keylen<=0) || (msglen<=0) || (*maclen<=0)
      || (authtypelen != USM_LENGTH_OID_TRANSFORM) )
   {
     QUITFUN(SNMPERR_GENERR, sc_generate_keyed_hash_quit);
   }
 
 properlength = sc_get_properlength(authtype, authtypelen);
 if (properlength == SNMPERR_GENERR)
   return properlength;
 
 if ( ((int)keylen < properlength) ) {
   QUITFUN(SNMPERR_GENERR, sc_generate_keyed_hash_quit);
 }
 
 
#ifdef USE_OPENSSL
 /*
  * Determine transform type.
  */
   if (ISTRANSFORM(authtype, HMACMD5Auth))
     HMAC(EVP_md5(), key, keylen, message, msglen,  
	  buf, &buf_len);
   else if (ISTRANSFORM(authtype, HMACSHA1Auth)) 
     HMAC(EVP_sha1(), key, keylen, message, msglen,  
	  buf, &buf_len);
   else {
     QUITFUN(SNMPERR_GENERR, sc_generate_keyed_hash_quit);
   }
   if (buf_len != properlength) {
     QUITFUN(rval, sc_generate_keyed_hash_quit);
   }
   if (*maclen > buf_len) 
     *maclen = buf_len;
   memcpy(MAC, buf, *maclen);
#else 
 if ((int)*maclen > properlength)
   *maclen = properlength;
 if (MDsign(message, msglen, MAC, *maclen, key, keylen)) {
   rval = SNMPERR_GENERR;
   goto sc_generate_keyed_hash_quit;
 }
#endif /* USE_OPENSSL */
 
#ifdef SNMP_TESTING_CODE
 {
   char    *s;
   int      len = binary_to_hex(MAC, *maclen, &s);
 
   DEBUGMSGTL(("scapi","Full v3 message hash: %s\n", s));
   SNMP_ZERO(s, len);
   SNMP_FREE(s);
 }
#endif
 
 sc_generate_keyed_hash_quit:
 SNMP_ZERO(buf, SNMP_MAXBUF_SMALL);
 return rval;
}  /* end sc_generate_keyed_hash() */
 
#else
_SCAPI_NOT_CONFIGURED
#endif							/* */
 
 
/* sc_hash(): a generic wrapper around whatever hashing package we are using.
 
   IN:
     hashtype    - oid pointer to a hash type
     hashtypelen - length of oid pointer
     buf         - u_char buffer to be hashed
     buf_len     - integer length of buf data
     MAC_len     - length of the passed MAC buffer size.
 
   OUT:    
     MAC         - pre-malloced space to store hash output.
     MAC_len     - length of MAC output to the MAC buffer.
 
   Returns:
     SNMPERR_SUCCESS		Success.
     SNMP_SC_GENERAL_FAILURE	Any error.
*/
 
int
sc_hash(oid *hashtype, size_t hashtypelen, u_char *buf, size_t buf_len,
        u_char *MAC, size_t *MAC_len)
#if defined(USE_INTERNAL_MD5) || defined(USE_OPENSSL)
{
  int   rval       = SNMPERR_SUCCESS;
 
#ifdef USE_OPENSSL 
  EVP_MD *hash(void);
  HMAC_CTX *c = NULL; 
#endif
 
  DEBUGTRACE;
 
  if (hashtype == NULL || hashtypelen < 0 || buf == NULL ||
      buf_len < 0 || MAC == NULL ||  MAC_len == NULL ||
      (int)(*MAC_len) < sc_get_properlength(hashtype, hashtypelen))
    return (SNMPERR_GENERR);
 
#ifdef USE_OPENSSL 
  /*
   * Determine transform type.
   */
  c = malloc(sizeof(HMAC_CTX));
  if (c == NULL)
    return (SNMPERR_GENERR);
 
  if (ISTRANSFORM(hashtype, HMACMD5Auth)) {
    EVP_DigestInit(&c->md_ctx, (const EVP_MD *) EVP_md5());
  }
  else if (ISTRANSFORM(hashtype, HMACSHA1Auth)) {
    EVP_DigestInit(&c->md_ctx, (const EVP_MD *) EVP_sha1());
  }
  else {
    return(SNMPERR_GENERR);
  }
  EVP_DigestUpdate(&c->md_ctx, buf, buf_len);
  EVP_DigestFinal(&(c->md_ctx), MAC, MAC_len);
  free(c);
  return (rval);
#else /* USE_INTERNAL_MD5 */
 
  if (MDchecksum(buf, buf_len, MAC, *MAC_len)) {
    return SNMPERR_GENERR;
  }
  if (*MAC_len > 16)
    *MAC_len = 16;
  return (rval);
 
#endif /* USE_OPENSSL */
}
#else /* !defined(USE_OPENSSL) && !defined(USE_INTERNAL_MD5) */
_SCAPI_NOT_CONFIGURED
#endif /* !defined(USE_OPENSSL) && !defined(USE_INTERNAL_MD5) */
 
 
 
/*******************************************************************-o-******
 * sc_check_keyed_hash
 *
 * Parameters:
 *	 authtype	Transform type of authentication hash.
 *	*key		Key bits in a string of bytes.
 *	 keylen		Length of key in bytes.
 *	*message	Message for which to check the hash.
 *	 msglen		Length of message.
 *	*MAC		Given hash.
 *	 maclen		Length of given hash; indicates truncation if it is
 *				shorter than the normal size of output for
 *				given hash transform.
 * Returns:
 *	SNMPERR_SUCCESS		Success.
 *	SNMP_SC_GENERAL_FAILURE	Any error
 *
 *
 * Check the hash given in MAC against the hash of message.  If the length
 * of MAC is less than the length of the transform hash output, only maclen
 * bytes are compared.  The length of MAC cannot be greater than the
 * length of the hash transform output.
 */
int
sc_check_keyed_hash(	oid	*authtype,	size_t authtypelen,
			u_char	*key,		u_int keylen,
			u_char	*message,	u_int msglen,
			u_char	*MAC,		u_int maclen)
#if defined(USE_INTERNAL_MD5) || defined(USE_OPENSSL)
{
	int		 rval	 = SNMPERR_SUCCESS;
	size_t		 buf_len = SNMP_MAXBUF_SMALL;
 
	u_char		 buf[SNMP_MAXBUF_SMALL];
 
        DEBUGTRACE;
 
#ifdef SNMP_TESTING_CODE
{
 int i;
 DEBUGMSG(("scapi", "sc_check_keyed_hash():    key=0x"));
 for(i=0; i< keylen; i++)
   DEBUGMSG(("scapi", "%02x", key[i] & 0xff));
 DEBUGMSG(("scapi"," (%d)\n", keylen));
}
#endif /* SNMP_TESTING_CODE */
 
	/*
	 * Sanity check.
	 */
	if ( !authtype || !key || !message || !MAC 
		|| (keylen<=0) || (msglen<=0) || (maclen<=0)
		|| (authtypelen != USM_LENGTH_OID_TRANSFORM) )
	{
		QUITFUN(SNMPERR_GENERR, sc_check_keyed_hash_quit);
	}
 
 
	/* 
	 * Generate a full hash of the message, then compare
	 * the result with the given MAC which may shorter than
	 * the full hash length.
	 */
	rval = sc_generate_keyed_hash(	authtype, authtypelen,
					key, keylen,
					message, msglen,
					buf, &buf_len);
	QUITFUN(rval, sc_check_keyed_hash_quit);
 
	if (maclen > msglen) {
		QUITFUN(SNMPERR_GENERR, sc_check_keyed_hash_quit);
 
	} else if ( memcmp(buf, MAC, maclen) != 0 ) {
		QUITFUN(SNMPERR_GENERR, sc_check_keyed_hash_quit);
	}
 
 
sc_check_keyed_hash_quit:
	SNMP_ZERO(buf, SNMP_MAXBUF_SMALL);
 
	return rval;
 
}  /* end sc_check_keyed_hash() */
 
#else
_SCAPI_NOT_CONFIGURED
#endif	/* USE_INTERNAL_MD5 */
 
 
 
/*******************************************************************-o-******
 * sc_encrypt
 *
 * Parameters:
 *	 privtype	Type of privacy cryptographic transform.
 *	*key		Key bits for crypting.
 *	 keylen		Length of key (buffer) in bytes.
 *	*iv		IV bits for crypting.
 *	 ivlen		Length of iv (buffer) in bytes.
 *	*plaintext	Plaintext to crypt.
 *	 ptlen		Length of plaintext.
 *	*ciphertext	Ciphertext to crypt.
 *	*ctlen		Length of ciphertext.
 *      
 * Returns:
 *	SNMPERR_SUCCESS			Success.
 *	SNMPERR_SC_NOT_CONFIGURED	Encryption is not supported.
 *	SNMPERR_SC_GENERAL_FAILURE	Any other error
 *
 *
 * Encrypt plaintext into ciphertext using key and iv.
 *
 * ctlen contains actual number of crypted bytes in ciphertext upon
 * successful return.
 */
int
sc_encrypt(	oid    *privtype,	size_t privtypelen,
		u_char *key,		u_int  keylen,
		u_char *iv,		u_int  ivlen,
		u_char *plaintext,	u_int  ptlen,
		u_char *ciphertext,	size_t *ctlen)
#if defined(USE_OPENSSL) 
{
	int		rval	= SNMPERR_SUCCESS;
	u_int		transform,
			properlength,
			properlength_iv;
	u_char		pad_block[32];  /* bigger than anything I need */
	u_char          my_iv[32];      /* ditto */
	int		pad, plast, pad_size;
	des_key_schedule key_sch;
	des_cblock      key_struct;
 
        DEBUGTRACE;
 
	/*
	 * Sanity check.
	 */
#if	!defined(SCAPI_AUTHPRIV)
		return SNMPERR_SC_NOT_CONFIGURED;
#endif
 
	if ( !privtype || !key || !iv || !plaintext || !ciphertext || !ctlen
		|| (keylen<=0) || (ivlen<=0) || (ptlen<=0) || (*ctlen<=0)
		|| (privtypelen != USM_LENGTH_OID_TRANSFORM) )
	{
		QUITFUN(SNMPERR_GENERR, sc_encrypt_quit);
	}
	else if ( ptlen >= *ctlen) { 
		QUITFUN(SNMPERR_GENERR, sc_encrypt_quit);
	}
 
 
#ifdef SNMP_TESTING_CODE
{
        char buf[SNMP_MAXBUF];
 
	sprint_hexstring(buf, iv, ivlen);
        DEBUGMSGTL(("scapi", "encrypt: IV: %s/ ", buf));
	sprint_hexstring(buf, key, keylen);
        DEBUGMSG(("scapi","%s\n", buf));
 
	sprint_hexstring(buf, plaintext, 16);
        DEBUGMSGTL(("scapi","encrypt: string: %s\n", buf));
}
#endif /* SNMP_TESTING_CODE */
 
 
	/*
	 * Determine privacy transform.
	 */
	if ( ISTRANSFORM(privtype, DESPriv) ) {
		properlength	= BYTESIZE(SNMP_TRANS_PRIVLEN_1DES);
		properlength_iv	= BYTESIZE(SNMP_TRANS_PRIVLEN_1DES_IV);
		pad_size = properlength;
	} else {
		QUITFUN(SNMPERR_GENERR, sc_encrypt_quit);
	}
 
	if ( (keylen<properlength) || (ivlen<properlength_iv) ) {
		QUITFUN(SNMPERR_GENERR, sc_encrypt_quit);
	}
 
	else if ( (keylen<properlength) || (ivlen<properlength_iv) ) {
		QUITFUN(SNMPERR_GENERR, sc_encrypt_quit);
	}
 
/* now calculate the padding needed */
	pad = pad_size - (ptlen % pad_size);
	if (ptlen + pad > *ctlen) { 
		QUITFUN(SNMPERR_GENERR, sc_encrypt_quit); /* not enough space */
	}
	memset(pad_block, 0, sizeof(pad_block));
	plast = (int) ptlen - (pad_size - pad);
	if (pad > 0)  /* copy data into pad block if needed */
		memcpy( pad_block, plaintext + plast, pad_size - pad);
	memset(&pad_block[pad_size-pad], pad, pad); /* filling in padblock */
 
	memset(my_iv, 0, sizeof(my_iv));
 
	if ( ISTRANSFORM(privtype, DESPriv) ) {
                memcpy(key_struct, key, sizeof(key_struct));
		(void) des_key_sched(&key_struct, key_sch);
 
		memcpy(my_iv, iv, ivlen);
		/* encrypt the data */
		des_ncbc_encrypt(plaintext, ciphertext, plast, key_sch, 
				 (des_cblock *) &my_iv, DES_ENCRYPT);
		/* then encrypt the pad block */
		des_ncbc_encrypt(pad_block, ciphertext+plast, pad_size, 
				 key_sch, (des_cblock *)&my_iv, DES_ENCRYPT);
		*ctlen = plast + pad_size;
	}
sc_encrypt_quit:
	/* clear memory just in case */
	memset(my_iv, 0, sizeof(my_iv));
	memset(pad_block, 0, sizeof(pad_block));
	memset(key_struct, 0, sizeof(key_struct));
	memset(key_sch, 0, sizeof(key_sch));
	return rval;
 
}  /* end sc_encrypt() */
 
#else
{
#	if USE_INTERNAL_MD5
	{
		DEBUGMSGTL(("scapi","Encrypt function not defined.\n"));
		return SNMPERR_SC_GENERAL_FAILURE;
	}
 
#	else
		_SCAPI_NOT_CONFIGURED
 
#	endif /* USE_INTERNAL_MD5 */
			}
#endif							/* */
 
 
 
/*******************************************************************-o-******
 * sc_decrypt
 *
 * Parameters:
 *	 privtype
 *	*key
 *	 keylen
 *	*iv
 *	 ivlen
 *	*ciphertext
 *	 ctlen
 *	*plaintext
 *	*ptlen
 *      
 * Returns:
 *	SNMPERR_SUCCESS			Success.
 *	SNMPERR_SC_NOT_CONFIGURED	Encryption is not supported.
 *      SNMPERR_SC_GENERAL_FAILURE      Any other error
 *
 *
 * Decrypt ciphertext into plaintext using key and iv.
 *
 * ptlen contains actual number of plaintext bytes in plaintext upon
 * successful return.
 */
int
sc_decrypt(	oid    *privtype,	size_t privtypelen,
		u_char *key,		u_int  keylen,
		u_char *iv,		u_int  ivlen,
		u_char *ciphertext,	u_int  ctlen,
		u_char *plaintext,	size_t *ptlen)
#ifdef USE_OPENSSL
{
 
	int rval = SNMPERR_SUCCESS;
	int i, j; 
	u_char *my_iv[32];
	des_key_schedule key_sch;
	des_cblock  key_struct;
	u_int		properlength,
			properlength_iv;
 
        DEBUGTRACE;
 
	if ( !privtype || !key || !iv || !plaintext || !ciphertext || !ptlen
		|| (ctlen<=0) || (*ptlen<=0) || (*ptlen < ctlen)
		|| (privtypelen != USM_LENGTH_OID_TRANSFORM) )
	{
		QUITFUN(SNMPERR_GENERR, sc_decrypt_quit);
	}
 
 
#ifdef SNMP_TESTING_CODE
{
        char buf[SNMP_MAXBUF];
 
	sprint_hexstring(buf, iv, ivlen);
        DEBUGMSGTL(("scapi", "decrypt: IV: %s/ ", buf));
	sprint_hexstring(buf, key, keylen);
        DEBUGMSG(("scapi","%s\n", buf));
}
#endif /* SNMP_TESTING_CODE */
 
	/*
	 * Determine privacy transform.
	 */
	if ( ISTRANSFORM(privtype, DESPriv) ) {
		properlength	= BYTESIZE(SNMP_TRANS_PRIVLEN_1DES);
		properlength_iv	= BYTESIZE(SNMP_TRANS_PRIVLEN_1DES_IV);
 
	} else {
		QUITFUN(SNMPERR_GENERR, sc_decrypt_quit);
	}
 
	if ( (keylen<properlength) || (ivlen<properlength_iv) ) {
		QUITFUN(SNMPERR_GENERR, sc_decrypt_quit);
	}
 
	memset(my_iv, 0, sizeof(my_iv));
	if (ISTRANSFORM(privtype, DESPriv)) {
                memcpy(key_struct, key, sizeof(key_struct));
		(void) des_key_sched(&key_struct, key_sch);
 
		memcpy(my_iv, iv, ivlen);
		des_cbc_encrypt(ciphertext, plaintext, ctlen, key_sch, 
				(des_cblock *) &my_iv, DES_DECRYPT);
	}
 
/* exit cond */
sc_decrypt_quit:
	memset(key_sch, 0, sizeof(key_sch));
	memset(key_struct, 0, sizeof(key_struct));
	memset(my_iv, 0, sizeof(my_iv));
	return rval;
}  
#else   /* USE OPEN_SSL */
{
#if	!defined(SCAPI_AUTHPRIV)
		return SNMPERR_SC_NOT_CONFIGURED;
#else
#	if USE_INTERNAL_MD5
	{
		DEBUGMSGTL(("scapi","Decryption function not defined.\n"));
		return SNMPERR_SC_GENERAL_FAILURE;
	}
 
#	else
		_SCAPI_NOT_CONFIGURED
 
#	endif /* USE_INTERNAL_MD5 */
#endif							/*  */
			}
#endif /* USE_OPENSSL */
 
#endif /* CYGPKG_SNMPAGENT_V3_SUPPORT */