/* Portions of this file are subject to the following copyright(s).  See
 * the Net-SNMP's COPYING file for more details and other copyrights
 * that may apply:
 */
/*
 * Portions of this file are copyrighted by:
 * Copyright © 2003 Sun Microsystems, Inc. All rights reserved.
 * Use is subject to license terms specified in the COPYING file
 * distributed with the Net-SNMP package.
 */

/*
 * keytools.c
 */

#include <net-snmp/net-snmp-config.h>

#include <stdio.h>
#include <sys/types.h>
#if HAVE_WINSOCK_H
#include <winsock.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#if HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif

#if HAVE_DMALLOC_H
#include <dmalloc.h>
#endif

#include <net-snmp/types.h>
#include <net-snmp/output_api.h>
#include <net-snmp/utilities.h>

#include <net-snmp/library/snmp_api.h>
#ifdef USE_OPENSSL
#	include <openssl/hmac.h>
#else
#ifdef USE_INTERNAL_MD5
#include <net-snmp/library/md5.h>
#endif
#endif

#ifdef USE_PKCS
#include <security/cryptoki.h>
#endif

#include <net-snmp/library/scapi.h>
#include <net-snmp/library/keytools.h>

#include <net-snmp/library/transform_oids.h>

/*******************************************************************-o-******
 * generate_Ku
 *
 * Parameters:
 *	*hashtype	MIB OID for the transform type for hashing.
 *	 hashtype_len	Length of OID value.
 *	*P		Pre-allocated bytes of passpharase.
 *	 pplen		Length of passphrase.
 *	*Ku		Buffer to contain Ku.
 *	*kulen		Length of Ku buffer.
 *      
 * Returns:
 *	SNMPERR_SUCCESS			Success.
 *	SNMPERR_GENERR			All errors.
 *
 *
 * Convert a passphrase into a master user key, Ku, according to the
 * algorithm given in RFC 2274 concerning the SNMPv3 User Security Model (USM)
 * as follows:
 *
 * Expand the passphrase to fill the passphrase buffer space, if necessary,
 * concatenation as many duplicates as possible of P to itself.  If P is
 * larger than the buffer space, truncate it to fit.
 *
 * Then hash the result with the given hashtype transform.  Return
 * the result as Ku.
 *
 * If successful, kulen contains the size of the hash written to Ku.
 *
 * NOTE  Passphrases less than USM_LENGTH_P_MIN characters in length
 *	 cause an error to be returned.
 *	 (Punt this check to the cmdline apps?  XXX)
 */
int
generate_Ku(const oid * hashtype, u_int hashtype_len,
            u_char * P, size_t pplen, u_char * Ku, size_t * kulen)
#if defined(USE_INTERNAL_MD5) || defined(USE_OPENSSL)
{
    int             rval = SNMPERR_SUCCESS,
        nbytes = USM_LENGTH_EXPANDED_PASSPHRASE;

    u_int           i, pindex = 0;

    u_char          buf[USM_LENGTH_KU_HASHBLOCK], *bufp;

#ifdef USE_OPENSSL
    EVP_MD_CTX     *ctx = malloc(sizeof(EVP_MD_CTX));
#else
    MDstruct        MD;
#endif
    /*
     * Sanity check.
     */
    if (!hashtype || !P || !Ku || !kulen || (*kulen <= 0)
        || (hashtype_len != USM_LENGTH_OID_TRANSFORM)) {
        QUITFUN(SNMPERR_GENERR, generate_Ku_quit);
    }

    if (pplen < USM_LENGTH_P_MIN) {
        snmp_log(LOG_ERR, "Error: passphrase chosen is below the length "
                 "requirements of the USM (min=%d).\n",USM_LENGTH_P_MIN);
        snmp_set_detail("The supplied password length is too short.");
        QUITFUN(SNMPERR_GENERR, generate_Ku_quit);
    }


    /*
     * Setup for the transform type.
     */
#ifdef USE_OPENSSL

    if (ISTRANSFORM(hashtype, HMACMD5Auth))
        EVP_DigestInit(ctx, EVP_md5());
    else if (ISTRANSFORM(hashtype, HMACSHA1Auth))
        EVP_DigestInit(ctx, EVP_sha1());
    else {
        free(ctx);
        return (SNMPERR_GENERR);
    }
#else
    MDbegin(&MD);
#endif                          /* USE_OPENSSL */

    while (nbytes > 0) {
        bufp = buf;
        for (i = 0; i < USM_LENGTH_KU_HASHBLOCK; i++) {
            *bufp++ = P[pindex++ % pplen];
        }
#ifdef USE_OPENSSL
        EVP_DigestUpdate(ctx, buf, USM_LENGTH_KU_HASHBLOCK);
#else
        if (MDupdate(&MD, buf, USM_LENGTH_KU_HASHBLOCK * 8)) {
            rval = SNMPERR_USM_ENCRYPTIONERROR;
            goto md5_fin;
        }
#endif                          /* USE_OPENSSL */

        nbytes -= USM_LENGTH_KU_HASHBLOCK;
    }

#ifdef USE_OPENSSL
    EVP_DigestFinal(ctx, (unsigned char *) Ku, (unsigned int *) kulen);
    /*
     * what about free() 
     */
#else
    if (MDupdate(&MD, buf, 0)) {
        rval = SNMPERR_USM_ENCRYPTIONERROR;
        goto md5_fin;
    }
    *kulen = sc_get_properlength(hashtype, hashtype_len);
    MDget(&MD, Ku, *kulen);
  md5_fin:
    memset(&MD, 0, sizeof(MD));
#endif                          /* USE_OPENSSL */


#ifdef SNMP_TESTING_CODE
    DEBUGMSGTL(("generate_Ku", "generating Ku (from %s): ", P));
    for (i = 0; i < *kulen; i++)
        DEBUGMSG(("generate_Ku", "%02x", Ku[i]));
    DEBUGMSG(("generate_Ku", "\n"));
#endif                          /* SNMP_TESTING_CODE */


  generate_Ku_quit:
    memset(buf, 0, sizeof(buf));
#ifdef USE_OPENSSL
    free(ctx);
#endif
    return rval;

}                               /* end generate_Ku() */
#elif USE_PKCS
{
    int             rval = SNMPERR_SUCCESS;

    /*
     * Sanity check.
     */
    if (!hashtype || !P || !Ku || !kulen || (*kulen <= 0)
        || (hashtype_len != USM_LENGTH_OID_TRANSFORM)) {
        QUITFUN(SNMPERR_GENERR, generate_Ku_quit);
    }

    if (pplen < USM_LENGTH_P_MIN) {
        snmp_log(LOG_ERR, "Error: passphrase chosen is below the length "
                 "requirements of the USM (min=%d).\n",USM_LENGTH_P_MIN);
        snmp_set_detail("The supplied password length is too short.");
        QUITFUN(SNMPERR_GENERR, generate_Ku_quit);
    }

    /*
     * Setup for the transform type.
     */

    if (ISTRANSFORM(hashtype, HMACMD5Auth))
        return pkcs_generate_Ku(CKM_MD5, P, pplen, Ku, kulen);
    else if (ISTRANSFORM(hashtype, HMACSHA1Auth))
        return pkcs_generate_Ku(CKM_SHA_1, P, pplen, Ku, kulen);
    else {
        return (SNMPERR_GENERR);
    }

  generate_Ku_quit:

    return rval;
}                               /* end generate_Ku() */
#else
_KEYTOOLS_NOT_AVAILABLE
#endif                          /* internal or openssl */
/*******************************************************************-o-******
 * generate_kul
 *
 * Parameters:
 *	*hashtype
 *	 hashtype_len
 *	*engineID
 *	 engineID_len
 *	*Ku		Master key for a given user.
 *	 ku_len		Length of Ku in bytes.
 *	*Kul		Localized key for a given user at engineID.
 *	*kul_len	Length of Kul buffer (IN); Length of Kul key (OUT).
 *      
 * Returns:
 *	SNMPERR_SUCCESS			Success.
 *	SNMPERR_GENERR			All errors.
 *
 *
 * Ku MUST be the proper length (currently fixed) for the given hashtype.
 *
 * Upon successful return, Kul contains the localized form of Ku at
 * engineID, and the length of the key is stored in kul_len.
 *
 * The localized key method is defined in RFC2274, Sections 2.6 and A.2, and
 * originally documented in:
 *  	U. Blumenthal, N. C. Hien, B. Wijnen,
 *     	"Key Derivation for Network Management Applications",
 *	IEEE Network Magazine, April/May issue, 1997.
 *
 *
 * ASSUMES  SNMP_MAXBUF >= sizeof(Ku + engineID + Ku).
 *
 * NOTE  Localized keys for privacy transforms are generated via
 *	 the authentication transform held by the same usmUser.
 *
 * XXX	An engineID of any length is accepted, even if larger than
 *	what is spec'ed for the textual convention.
 */
int
generate_kul(const oid * hashtype, u_int hashtype_len,
             u_char * engineID, size_t engineID_len,
             u_char * Ku, size_t ku_len,
             u_char * Kul, size_t * kul_len)
#if defined(USE_OPENSSL) || defined(USE_INTERNAL_MD5) || defined(USE_PKCS)
{
    int             rval = SNMPERR_SUCCESS;
    u_int           nbytes = 0;
    size_t          properlength;

    u_char          buf[SNMP_MAXBUF];
#ifdef SNMP_TESTING_CODE
    int             i;
#endif


    /*
     * Sanity check.
     */
    if (!hashtype || !engineID || !Ku || !Kul || !kul_len
        || (engineID_len <= 0) || (ku_len <= 0) || (*kul_len <= 0)
        || (hashtype_len != USM_LENGTH_OID_TRANSFORM)) {
        QUITFUN(SNMPERR_GENERR, generate_kul_quit);
    }


    properlength = sc_get_properlength(hashtype, hashtype_len);
    if (properlength == SNMPERR_GENERR)
        QUITFUN(SNMPERR_GENERR, generate_kul_quit);


    if (((int) *kul_len < properlength) || ((int) ku_len < properlength)) {
        QUITFUN(SNMPERR_GENERR, generate_kul_quit);
    }

    /*
     * Concatenate Ku and engineID properly, then hash the result.
     * Store it in Kul.
     */
    nbytes = 0;
    memcpy(buf, Ku, properlength);
    nbytes += properlength;
    memcpy(buf + nbytes, engineID, engineID_len);
    nbytes += engineID_len;
    memcpy(buf + nbytes, Ku, properlength);
    nbytes += properlength;

    rval = sc_hash(hashtype, hashtype_len, buf, nbytes, Kul, kul_len);

#ifdef SNMP_TESTING_CODE
    DEBUGMSGTL(("generate_kul", "generating Kul (from Ku): "));
    for (i = 0; i < *kul_len; i++)
        DEBUGMSG(("generate_kul", "%02x", Kul[i]));
    DEBUGMSG(("generate_kul", "keytools\n"));
#endif                          /* SNMP_TESTING_CODE */

    QUITFUN(rval, generate_kul_quit);


  generate_kul_quit:
    return rval;

}                               /* end generate_kul() */

#else
_KEYTOOLS_NOT_AVAILABLE
#endif                          /* internal or openssl */
/*******************************************************************-o-******
 * encode_keychange
 *
 * Parameters:
 *	*hashtype	MIB OID for the hash transform type.
 *	 hashtype_len	Length of the MIB OID hash transform type.
 *	*oldkey		Old key that is used to encodes the new key.
 *	 oldkey_len	Length of oldkey in bytes.
 *	*newkey		New key that is encoded using the old key.
 *	 newkey_len	Length of new key in bytes.
 *	*kcstring	Buffer to contain the KeyChange TC string.
 *	*kcstring_len	Length of kcstring buffer.
 *      
 * Returns:
 *	SNMPERR_SUCCESS			Success.
 *	SNMPERR_GENERR			All errors.
 *
 *
 * Uses oldkey and acquired random bytes to encode newkey into kcstring
 * according to the rules of the KeyChange TC described in RFC 2274, Section 5.
 *
 * Upon successful return, *kcstring_len contains the length of the
 * encoded string.
 *
 * ASSUMES	Old and new key are always equal to each other, although
 *		this may be less than the transform type hash output
 * 		output length (eg, using KeyChange for a DESPriv key when
 *		the user also uses SHA1Auth).  This also implies that the
 *		hash placed in the second 1/2 of the key change string
 *		will be truncated before the XOR'ing when the hash output is 
 *		larger than that 1/2 of the key change string.
 *
 *		*kcstring_len will be returned as exactly twice that same
 *		length though the input buffer may be larger.
 *
 * XXX FIX:     Does not handle varibable length keys.
 * XXX FIX:     Does not handle keys larger than the hash algorithm used.
 */
int
encode_keychange(const oid * hashtype, u_int hashtype_len,
                 u_char * oldkey, size_t oldkey_len,
                 u_char * newkey, size_t newkey_len,
                 u_char * kcstring, size_t * kcstring_len)
#if defined(USE_OPENSSL) || defined(USE_INTERNAL_MD5) || defined(USE_PKCS)
{
    int             rval = SNMPERR_SUCCESS;
    size_t          properlength;
    size_t          nbytes = 0;

    u_char         *tmpbuf = NULL;


    /*
     * Sanity check.
     */
    if (!hashtype || !oldkey || !newkey || !kcstring || !kcstring_len
        || (oldkey_len <= 0) || (newkey_len <= 0) || (*kcstring_len <= 0)
        || (hashtype_len != USM_LENGTH_OID_TRANSFORM)) {
        QUITFUN(SNMPERR_GENERR, encode_keychange_quit);
    }

    /*
     * Setup for the transform type.
     */
    properlength = sc_get_properlength(hashtype, hashtype_len);
    if (properlength == SNMPERR_GENERR)
        QUITFUN(SNMPERR_GENERR, encode_keychange_quit);

    if ((oldkey_len != newkey_len) || (*kcstring_len < (2 * oldkey_len))) {
        QUITFUN(SNMPERR_GENERR, encode_keychange_quit);
    }

    properlength = SNMP_MIN((int) oldkey_len, properlength);

    /*
     * Use the old key and some random bytes to encode the new key
     * in the KeyChange TC format:
     *      . Get random bytes (store in first half of kcstring),
     *      . Hash (oldkey | random_bytes) (into second half of kcstring),
     *      . XOR hash and newkey (into second half of kcstring).
     *
     * Getting the wrong number of random bytes is considered an error.
     */
    nbytes = properlength;

#if defined(SNMP_TESTING_CODE) && defined(RANDOMZEROS)
    memset(kcstring, 0, nbytes);
    DEBUGMSG(("encode_keychange",
              "** Using all zero bits for \"random\" delta of )"
              "the keychange string! **\n"));
#else                           /* !SNMP_TESTING_CODE */
    rval = sc_random(kcstring, &nbytes);
    QUITFUN(rval, encode_keychange_quit);
    if ((int) nbytes != properlength) {
        QUITFUN(SNMPERR_GENERR, encode_keychange_quit);
    }
#endif                          /* !SNMP_TESTING_CODE */

    tmpbuf = (u_char *) malloc(properlength * 2);
    if (tmpbuf) {
        memcpy(tmpbuf, oldkey, properlength);
        memcpy(tmpbuf + properlength, kcstring, properlength);

        *kcstring_len -= properlength;
        rval = sc_hash(hashtype, hashtype_len, tmpbuf, properlength * 2,
                       kcstring + properlength, kcstring_len);

        QUITFUN(rval, encode_keychange_quit);

        *kcstring_len = (properlength * 2);

        kcstring += properlength;
        nbytes = 0;
        while ((int) (nbytes++) < properlength) {
            *kcstring++ ^= *newkey++;
        }
    }

  encode_keychange_quit:
    if (rval != SNMPERR_SUCCESS)
        memset(kcstring, 0, *kcstring_len);
    SNMP_FREE(tmpbuf);

    return rval;

}                               /* end encode_keychange() */

#else
_KEYTOOLS_NOT_AVAILABLE
#endif                          /* internal or openssl */
/*******************************************************************-o-******
 * decode_keychange
 *
 * Parameters:
 *	*hashtype	MIB OID of the hash transform to use.
 *	 hashtype_len	Length of the hash transform MIB OID.
 *	*oldkey		Old key that is used to encode the new key.
 *	 oldkey_len	Length of oldkey in bytes.
 *	*kcstring	Encoded KeyString buffer containing the new key.
 *	 kcstring_len	Length of kcstring in bytes.
 *	*newkey		Buffer to hold the extracted new key.
 *	*newkey_len	Length of newkey in bytes.
 *      
 * Returns:
 *	SNMPERR_SUCCESS			Success.
 *	SNMPERR_GENERR			All errors.
 *
 *
 * Decodes a string of bits encoded according to the KeyChange TC described
 * in RFC 2274, Section 5.  The new key is extracted from *kcstring with
 * the aid of the old key.
 *
 * Upon successful return, *newkey_len contains the length of the new key.
 *
 *
 * ASSUMES	Old key is exactly 1/2 the length of the KeyChange buffer,
 *		although this length may be less than the hash transform
 *		output.  Thus the new key length will be equal to the old
 *		key length.
 */
/*
 * XXX:  if the newkey is not long enough, it should be freed and remalloced 
 */
int
decode_keychange(const oid * hashtype, u_int hashtype_len,
                 u_char * oldkey, size_t oldkey_len,
                 u_char * kcstring, size_t kcstring_len,
                 u_char * newkey, size_t * newkey_len)
#if defined(USE_OPENSSL) || defined(USE_INTERNAL_MD5) || defined(USE_PKCS)
{
    int             rval = SNMPERR_SUCCESS;
    size_t          properlength = 0;
    u_int           nbytes = 0;

    u_char         *bufp, tmp_buf[SNMP_MAXBUF];
    size_t          tmp_buf_len = SNMP_MAXBUF;
    u_char         *tmpbuf = NULL;



    /*
     * Sanity check.
     */
    if (!hashtype || !oldkey || !kcstring || !newkey || !newkey_len
        || (oldkey_len <= 0) || (kcstring_len <= 0) || (*newkey_len <= 0)
        || (hashtype_len != USM_LENGTH_OID_TRANSFORM)) {
        QUITFUN(SNMPERR_GENERR, decode_keychange_quit);
    }


    /*
     * Setup for the transform type.
     */
    properlength = sc_get_properlength(hashtype, hashtype_len);
    if (properlength == SNMPERR_GENERR)
        QUITFUN(SNMPERR_GENERR, decode_keychange_quit);


    if (((oldkey_len * 2) != kcstring_len) || (*newkey_len < oldkey_len)) {
        QUITFUN(SNMPERR_GENERR, decode_keychange_quit);
    }

    properlength = oldkey_len;
    *newkey_len = properlength;

    /*
     * Use the old key and the given KeyChange TC string to recover
     * the new key:
     *      . Hash (oldkey | random_bytes) (into newkey),
     *      . XOR hash and encoded (second) half of kcstring (into newkey).
     */
    tmpbuf = (u_char *) malloc(properlength * 2);
    if (tmpbuf) {
        memcpy(tmpbuf, oldkey, properlength);
        memcpy(tmpbuf + properlength, kcstring, properlength);

        rval = sc_hash(hashtype, hashtype_len, tmpbuf, properlength * 2,
                       tmp_buf, &tmp_buf_len);
        QUITFUN(rval, decode_keychange_quit);

        memcpy(newkey, tmp_buf, properlength);
        bufp = kcstring + properlength;
        nbytes = 0;
        while ((int) (nbytes++) < properlength) {
            *newkey++ ^= *bufp++;
        }
    }

  decode_keychange_quit:
    if (rval != SNMPERR_SUCCESS) {
        memset(newkey, 0, properlength);
    }
    memset(tmp_buf, 0, SNMP_MAXBUF);
    if (tmpbuf != NULL)
        SNMP_FREE(tmpbuf);

    return rval;

}                               /* end decode_keychange() */

#else
_KEYTOOLS_NOT_AVAILABLE
#endif                          /* internal or openssl */
