/*
 * libretroshare/src/gxs: gxssecurity.cc
 *
 *
 * Copyright 2008-2010 by Robert Fernie
 *           2011-2012 Christopher Evi-Parker
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License Version 2 as published by the Free Software Foundation.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA.
 *
 * Please report all bugs and problems to "retroshare@lunamutt.com".
 *
 */

#include "gxssecurity.h"
#include "pqi/authgpg.h"
#include "util/rsdir.h"
#include "util/rsmemory.h"
//#include "retroshare/rspeers.h"

/****
 * #define GXS_SECURITY_DEBUG 	1
 ***/

static const uint32_t MULTI_ENCRYPTION_FORMAT_v001_HEADER              = 0xFACE;
static const uint32_t MULTI_ENCRYPTION_FORMAT_v001_HEADER_SIZE         = 2 ;
static const uint32_t MULTI_ENCRYPTION_FORMAT_v001_NUMBER_OF_KEYS_SIZE = 2 ;
static const uint32_t MULTI_ENCRYPTION_FORMAT_v001_ENCRYPTED_KEY_SIZE  = 256 ;
        
static RsGxsId getRsaKeyFingerprint_old_insecure_method(RSA *pubkey)
{
#if OPENSSL_VERSION_NUMBER < 0x10100000L
        int lenn = BN_num_bytes(pubkey -> n);

        RsTemporaryMemory tmp(lenn) ;
        BN_bn2bin(pubkey -> n, tmp);
#else
        const BIGNUM *nn=NULL,*ee=NULL ;
        RSA_get0_key(pubkey,&nn,&ee,NULL) ;

        int lenn = BN_num_bytes(nn);

        RsTemporaryMemory tmp(lenn) ;
        BN_bn2bin(nn, tmp);
#endif

        // Copy first CERTSIGNLEN bytes from the hash of the public modulus and exponent
		// We should not be using strings here, but a real ID. To be done later.

		assert(lenn >= CERTSIGNLEN) ;

		return RsGxsId((unsigned char*)tmp) ;
}
static RsGxsId getRsaKeyFingerprint(RSA *pubkey)
{
#if OPENSSL_VERSION_NUMBER < 0x10100000L
        int lenn = BN_num_bytes(pubkey -> n);
        int lene = BN_num_bytes(pubkey -> e);

        RsTemporaryMemory tmp(lenn+lene) ;

        BN_bn2bin(pubkey -> n, tmp);
        BN_bn2bin(pubkey -> e, &tmp[lenn]);
#else
        const BIGNUM *nn=NULL,*ee=NULL ;
        RSA_get0_key(pubkey,&nn,&ee,NULL) ;

        int lenn = BN_num_bytes(nn);
        int lene = BN_num_bytes(ee);

        RsTemporaryMemory tmp(lenn+lene) ;

        BN_bn2bin(nn, tmp);
        BN_bn2bin(ee, &tmp[lenn]);
#endif

	Sha1CheckSum s = RsDirUtil::sha1sum(tmp,lenn+lene) ;

        // Copy first CERTSIGNLEN bytes from the hash of the public modulus and exponent
		  // We should not be using strings here, but a real ID. To be done later.

		  assert(Sha1CheckSum::SIZE_IN_BYTES >= CERTSIGNLEN) ;

        return RsGxsId(s.toStdString().substr(0,2*CERTSIGNLEN));
}

static RSA *extractPrivateKey(const RsTlvPrivateRSAKey& key)
{
    assert(key.keyFlags & RSTLV_KEY_TYPE_FULL) ;

        const unsigned char *keyptr = (const unsigned char *) key.keyData.bin_data;
        long keylen = key.keyData.bin_len;

        /* extract admin key */
        RSA *rsakey = d2i_RSAPrivateKey(NULL, &(keyptr), keylen);

        return rsakey;
}

static RSA *extractPublicKey(const RsTlvPublicRSAKey& key)
{
    assert(!(key.keyFlags & RSTLV_KEY_TYPE_FULL)) ;

        const unsigned char *keyptr = (const unsigned char *) key.keyData.bin_data;
        long keylen = key.keyData.bin_len;

        /* extract admin key */
        RSA *rsakey = d2i_RSAPublicKey(NULL, &(keyptr), keylen);

        return rsakey;
}
static void setRSAPublicKeyData(RsTlvPublicRSAKey& key, RSA *rsa_pub)
{
    assert(!(key.keyFlags & RSTLV_KEY_TYPE_FULL)) ;
        unsigned char *data = NULL ;	// this works for OpenSSL > 0.9.7
        int reqspace = i2d_RSAPublicKey(rsa_pub, &data);

        key.keyData.setBinData(data, reqspace);
        key.keyId = getRsaKeyFingerprint(rsa_pub);

	free(data) ;
}

static void setRSAPrivateKeyData(RsTlvPrivateRSAKey& key, RSA *rsa_priv)
{
    assert(key.keyFlags & RSTLV_KEY_TYPE_FULL) ;
    
        unsigned char *data = NULL ;	// this works for OpenSSL > 0.9.7
        int reqspace = i2d_RSAPrivateKey(rsa_priv, &data);

        key.keyData.setBinData(data, reqspace);
        key.keyId = getRsaKeyFingerprint(rsa_priv);

	free(data) ;
}
bool GxsSecurity::checkFingerprint(const RsTlvPublicRSAKey& key)
{
    RSA *rsa_pub = ::extractPublicKey(key) ;
    bool res = (key.keyId == getRsaKeyFingerprint(rsa_pub)) ;
    RSA_free(rsa_pub) ;
    return res ;
}

bool GxsSecurity::checkPrivateKey(const RsTlvPrivateRSAKey& key)
{
#ifdef GXS_SECURITY_DEBUG
    std::cerr << "Checking private key " << key.keyId << " ..." << std::endl;
#endif

    if( (key.keyFlags & RSTLV_KEY_TYPE_MASK) != RSTLV_KEY_TYPE_FULL)
    {
        std::cerr << "(WW) GxsSecurity::checkPrivateKey(): private key has wrong flags " << std::hex << (key.keyFlags & RSTLV_KEY_TYPE_MASK) << std::dec << ". This is unexpected." << std::endl;
        return false ;
    }
    RSA *rsa_prv = ::extractPrivateKey(key) ;

    if(rsa_prv == NULL)
    {
        std::cerr << "(WW) GxsSecurity::checkPrivateKey(): no private key can be extracted from key ID " << key.keyId << ". Key is corrupted?" << std::endl;
        return false ;
    }
    RSA *rsa_pub = RSAPublicKey_dup(rsa_prv);
    RSA_free(rsa_prv) ;

    if(rsa_pub == NULL)
    {
        std::cerr << "(WW) GxsSecurity::checkPrivateKey(): no public key can be extracted from key ID " << key.keyId << ". Key is corrupted?" << std::endl;
        return false ;
    }
    RsGxsId recomputed_key_id = getRsaKeyFingerprint(rsa_pub) ;

    if(recomputed_key_id != key.keyId)
    {
        if(key.keyId == getRsaKeyFingerprint_old_insecure_method(rsa_pub))
        {
#ifdef GXS_SECURITY_DEBUG
        	std::cerr << "(WW) fingerprint of key " << key.keyId << " was derived using old---insecure---format. It can be faked easily. You should get rid of this key!" << std::endl;
#endif
		RSA_free(rsa_pub) ;
        
		// The policy is to *accept* these private keys, but the public key that corresponds will be rejected anyway, as it can easily be faked.
		return true ;
        }
        else
	{
		std::cerr << "(WW) GxsSecurity::checkPrivateKey(): key " << key.keyId << " has wrong fingerprint " << recomputed_key_id << std::endl;

		RSA_free(rsa_pub) ;
		return false ;
	}
    }

    RSA_free(rsa_pub) ;
    return true ;
}

bool GxsSecurity::checkPublicKey(const RsTlvPublicRSAKey &key)
{
#ifdef GXS_SECURITY_DEBUG
    std::cerr << "Checking public key " << key.keyId << " ..." << std::endl;
#endif

    if( (key.keyFlags & RSTLV_KEY_TYPE_MASK) != RSTLV_KEY_TYPE_PUBLIC_ONLY)
    {
        std::cerr << "(WW) GxsSecurity::checkPublicKey(): public key has wrong flags " << std::hex << (key.keyFlags & RSTLV_KEY_TYPE_MASK) << std::dec << ". This is unexpected." << std::endl;
        return false ;
    }
    
    // try to extract private key
    const unsigned char *keyptr = (const unsigned char *) key.keyData.bin_data;
    long keylen = key.keyData.bin_len;
    RSA *rsa_prv = d2i_RSAPrivateKey(NULL, &(keyptr), keylen);
    
    if(rsa_prv != NULL)
    {
        std::cerr << "(SS) GxsSecurity::checkPublicKey(): public key with ID " << key.keyId << " actually is a Private key!!!" << std::endl;
	RSA_free(rsa_prv) ;
    	return false ;
    }
    
    RSA *rsa_pub = ::extractPublicKey(key) ;

    if(rsa_pub == NULL)
    {
        std::cerr << "(WW) GxsSecurity::checkPublicKey(): no public key can be extracted from key ID " << key.keyId << ". Key is corrupted?" << std::endl;
        return false ;
    }
    RsGxsId recomputed_key_id = getRsaKeyFingerprint(rsa_pub) ;

    if(recomputed_key_id != key.keyId)
    {
        if(key.keyId == getRsaKeyFingerprint_old_insecure_method(rsa_pub))
        {
#ifdef GXS_SECURITY_DEBUG
        	std::cerr << "(WW) fingerprint was derived using old---insecure---format. It can be faked easily." << std::endl;
#endif
	    RSA_free(rsa_pub) ;
        
	    // The policy is to accept these public keys, but warn the owner, since they might be fake keys. They will be soon rejected here, by replacing
            // the return value by false.
	    return true ;
        }
        else
		std::cerr << "(WW) GxsSecurity::checkPublicKey(): key " << key.keyId << " has wrong fingerprint " << recomputed_key_id << "! Key will be discarded." << std::endl;
            
	RSA_free(rsa_pub) ;
        return false ;
    }

    RSA_free(rsa_pub) ;
    return true ;
}

bool GxsSecurity::generateKeyPair(RsTlvPublicRSAKey& public_key,RsTlvPrivateRSAKey& private_key)
{
	// admin keys
	BIGNUM *ebn = BN_new();
	BN_set_word(ebn, 65537);
	RSA *rsa     = RSA_new();
	RSA_generate_key_ex(rsa, 2048, ebn, NULL);
    RSA *rsa_pub = RSAPublicKey_dup(rsa);
    
    public_key.keyFlags = RSTLV_KEY_TYPE_PUBLIC_ONLY ;
    private_key.keyFlags = RSTLV_KEY_TYPE_FULL ;

    setRSAPublicKeyData(public_key, rsa_pub);
    setRSAPrivateKeyData(private_key, rsa);

    public_key.startTS  = time(NULL);
    public_key.endTS    = public_key.startTS + 60 * 60 * 24 * 365 * 5; /* approx 5 years */

    private_key.startTS  = public_key.startTS;
    private_key.endTS    = 0; /* no end */

    // clean up
    RSA_free(rsa);
    RSA_free(rsa_pub);

    if(!(private_key.checkKey() && public_key.checkKey()))
    {
        std::cerr << "(EE) ERROR while generating keys. Something inconsistent in flags. This is probably a bad sign!" << std::endl;
	return false ;
    }
                     
    return true ;
}

bool GxsSecurity::extractPublicKey(const RsTlvPrivateRSAKey &private_key, RsTlvPublicRSAKey &public_key)
{
    public_key.TlvClear() ;

    if(!(private_key.keyFlags & RSTLV_KEY_TYPE_FULL))
        return false ;

    RSA *rsaPrivKey = extractPrivateKey(private_key);

    if(!rsaPrivKey)
        return false ;

    RSA *rsaPubKey = RSAPublicKey_dup(rsaPrivKey);
    RSA_free(rsaPrivKey);

    if(!rsaPubKey)
        return false ;

    setRSAPublicKeyData(public_key, rsaPubKey);
    RSA_free(rsaPubKey);

    public_key.keyFlags  = private_key.keyFlags & (RSTLV_KEY_DISTRIB_MASK) ;	// keep the distrib flags
    public_key.keyFlags |= RSTLV_KEY_TYPE_PUBLIC_ONLY;
    public_key.startTS   = private_key.startTS ;
    public_key.endTS     = public_key.startTS + 60 * 60 * 24 * 365 * 5; /* approx 5 years */

    // This code fixes a problem of old RSA keys where the fingerprint wasn't computed using SHA1(n,e) but
    // using the first bytes of n (ouuuuch!). Still, these keys are valid and should produce a correct
    // fingerprint. So we replace the public key fingerprint (that is normally recomputed) with the FP of
    // the private key.

    if(public_key.keyId != private_key.keyId)
    {
        std::cerr << std::endl;
        std::cerr << "WARNING: GXS ID key pair " << private_key.keyId << " has inconsistent fingerprint. This is an old key " << std::endl;
        std::cerr << "         that is unsecure (can be faked easily). You should delete it!" << std::endl;
        std::cerr << std::endl;

        public_key.keyId = private_key.keyId ;
    }

    return true ;
}

bool GxsSecurity::getSignature(const char *data, uint32_t data_len, const RsTlvPrivateRSAKey &privKey, RsTlvKeySignature& sign)
{
	RSA* rsa_priv = extractPrivateKey(privKey);

	if(!rsa_priv)
	{
		std::cerr << "GxsSecurity::getSignature(): Cannot create signature. Keydata is incomplete." << std::endl;
		return false ;
	}
	EVP_PKEY *key_priv = EVP_PKEY_new();
	EVP_PKEY_assign_RSA(key_priv, rsa_priv);

	/* calc and check signature */
	EVP_MD_CTX *mdctx = EVP_MD_CTX_create();
	bool ok = EVP_SignInit(mdctx, EVP_sha1()) == 1;
	ok &= EVP_SignUpdate(mdctx, data, data_len) == 1;

	unsigned int siglen = EVP_PKEY_size(key_priv);
	unsigned char sigbuf[siglen];
	ok &= EVP_SignFinal(mdctx, sigbuf, &siglen, key_priv) == 1;

	// clean up
	EVP_MD_CTX_destroy(mdctx);
	EVP_PKEY_free(key_priv);

	sign.signData.setBinData(sigbuf, siglen);
	sign.keyId = RsGxsId(privKey.keyId);

	return ok;
}

bool GxsSecurity::validateSignature(const char *data, uint32_t data_len, const RsTlvPublicRSAKey &key, const RsTlvKeySignature& signature)
{
    assert(!(key.keyFlags & RSTLV_KEY_TYPE_FULL)) ;
        
	RSA *rsakey = ::extractPublicKey(key) ;

	if(!rsakey)
	{
		std::cerr << "GxsSecurity::validateSignature(): Cannot validate signature. Keydata is incomplete." << std::endl;
		key.print(std::cerr,0) ;
		return false ;
	}
	EVP_PKEY *signKey = EVP_PKEY_new();
	EVP_PKEY_assign_RSA(signKey, rsakey);

	/* calc and check signature */
	EVP_MD_CTX *mdctx = EVP_MD_CTX_create();

	EVP_VerifyInit(mdctx, EVP_sha1());
	EVP_VerifyUpdate(mdctx, data, data_len);

	int signOk = EVP_VerifyFinal(mdctx, (unsigned char*)signature.signData.bin_data, signature.signData.bin_len, signKey);

	/* clean up */
	EVP_PKEY_free(signKey);
	EVP_MD_CTX_destroy(mdctx);

	return signOk;
}

bool GxsSecurity::validateNxsMsg(const RsNxsMsg& msg, const RsTlvKeySignature& sign, const RsTlvPublicRSAKey& key)
{
    #ifdef GXS_SECURITY_DEBUG
            std::cerr << "GxsSecurity::validateNxsMsg()";
            std::cerr << std::endl;
            std::cerr << "RsNxsMsg :";
            std::cerr << std::endl;
            const_cast<RsNxsMsg*>(&msg)->print(std::cerr, 10);
            std::cerr << std::endl;
    #endif

            RsGxsMsgMetaData& msgMeta = *(msg.metaData);

    //        /********************* check signature *******************/

            /* check signature timeperiod */
            if ((msgMeta.mPublishTs < key.startTS) || (key.endTS != 0 && msgMeta.mPublishTs > key.endTS))
            {
    #ifdef GXS_SECURITY_DEBUG
                    std::cerr << " GxsSecurity::validateNxsMsg() TS out of range";
                    std::cerr << std::endl;
    #endif
                    return false;
            }

            /* decode key */
            const unsigned char *keyptr = (const unsigned char *) key.keyData.bin_data;
            long keylen = key.keyData.bin_len;
            unsigned int siglen = sign.signData.bin_len;
            unsigned char *sigbuf = (unsigned char *) sign.signData.bin_data;

    #ifdef DISTRIB_DEBUG
            std::cerr << "GxsSecurity::validateNxsMsg() Decode Key";
            std::cerr << " keylen: " << keylen << " siglen: " << siglen;
            std::cerr << std::endl;
    #endif

            /* extract admin key */

            RSA *rsakey = (key.keyFlags & RSTLV_KEY_TYPE_FULL)?  (d2i_RSAPrivateKey(NULL, &(keyptr), keylen)) : (d2i_RSAPublicKey(NULL, &(keyptr), keylen));

            if (!rsakey)
            {
    #ifdef GXS_SECURITY_DEBUG
                    std::cerr << "GxsSecurity::validateNxsMsg()";
                    std::cerr << " Invalid RSA Key";
                    std::cerr << std::endl;

                    key.print(std::cerr, 10);
    #endif
            }


            RsTlvKeySignatureSet signSet = msgMeta.signSet;
            msgMeta.signSet.TlvClear();

            RsGxsMessageId msgId = msgMeta.mMsgId, origMsgId = msgMeta.mOrigMsgId;
            msgMeta.mOrigMsgId.clear();
            msgMeta.mMsgId.clear();
	    int signOk = 0 ;

	{
		EVP_PKEY *signKey = EVP_PKEY_new();
		EVP_PKEY_assign_RSA(signKey, rsakey);
		EVP_MD_CTX *mdctx = EVP_MD_CTX_create();

		uint32_t metaDataLen = msgMeta.serial_size();
		uint32_t allMsgDataLen = metaDataLen + msg.msg.bin_len;

		RsTemporaryMemory metaData(metaDataLen) ;
		RsTemporaryMemory allMsgData(allMsgDataLen) ;

		if(!metaData || !allMsgData)
			return false ;
		
		msgMeta.serialise(metaData, &metaDataLen);

		// copy msg data and meta in allmsgData buffer
		memcpy(allMsgData, msg.msg.bin_data, msg.msg.bin_len);
		memcpy(allMsgData+(msg.msg.bin_len), metaData, metaDataLen);

		/* calc and check signature */

		EVP_VerifyInit(mdctx, EVP_sha1());
		EVP_VerifyUpdate(mdctx, allMsgData, allMsgDataLen);

		signOk = EVP_VerifyFinal(mdctx, sigbuf, siglen, signKey);

		/* clean up */
		EVP_PKEY_free(signKey);
		EVP_MD_CTX_destroy(mdctx);
	}

            msgMeta.mOrigMsgId = origMsgId;
            msgMeta.mMsgId = msgId;
            msgMeta.signSet = signSet;

            if (signOk == 1)
            {
    #ifdef GXS_SECURITY_DEBUG
                    std::cerr << "GxsSecurity::validateNxsMsg() Signature OK";
                    std::cerr << std::endl;
    #endif
                    return true;
            }

    #ifdef GXS_SECURITY_DEBUG
            std::cerr << "GxsSecurity::validateNxsMsg() Signature invalid";
            std::cerr << std::endl;
    #endif

	return false;
}

bool GxsSecurity::encrypt(uint8_t *& out, uint32_t &outlen, const uint8_t *in, uint32_t inlen, const RsTlvPublicRSAKey& key)
{
#ifdef DISTRIB_DEBUG
	std::cerr << "GxsSecurity::encrypt() " << std::endl;
#endif
        // Encrypts (in,inlen) into (out,outlen) using the given RSA public key.
        // The format of the encrypted data is:
        //
        //   [--- Encrypted session key length ---|--- Encrypted session key ---|--- IV ---|---- Encrypted data ---]
        //

    	out = NULL ;
    
	RSA *tmpkey = ::extractPublicKey(key) ;
	RSA *rsa_publish_pub = RSAPublicKey_dup(tmpkey) ;
	RSA_free(tmpkey) ;

	EVP_PKEY *public_key = NULL;

	//RSA* rsa_publish = EVP_PKEY_get1_RSA(privateKey);
	//rsa_publish_pub = RSAPublicKey_dup(rsa_publish);


	if(rsa_publish_pub  != NULL)
	{
		public_key = EVP_PKEY_new();
		EVP_PKEY_assign_RSA(public_key, rsa_publish_pub);
	}
	else
	{
#ifdef DISTRIB_DEBUG
		std::cerr << "GxsSecurity(): Could not generate publish key " << grpId
		          << std::endl;
#endif
		return false;
	}

	EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
	int eklen, net_ekl;
	unsigned char *ek;
	unsigned char iv[EVP_MAX_IV_LENGTH];
	int out_currOffset = 0;
	int out_offset = 0;

	int max_evp_key_size = EVP_PKEY_size(public_key);
	ek = (unsigned char*)rs_malloc(max_evp_key_size);
    
    	if(ek == NULL)
            return false ;
        
	const EVP_CIPHER *cipher = EVP_aes_128_cbc();
	int cipher_block_size = EVP_CIPHER_block_size(cipher);
	int size_net_ekl = sizeof(net_ekl);

	int max_outlen = inlen + cipher_block_size + EVP_MAX_IV_LENGTH + max_evp_key_size + size_net_ekl;

	// intialize context and send store encrypted cipher in ek
	if(!EVP_SealInit(ctx, EVP_aes_128_cbc(), &ek, &eklen, iv, &public_key, 1)) return false;

	// now assign memory to out accounting for data, and cipher block size, key length, and key length val
	out = (uint8_t*)rs_malloc(inlen + cipher_block_size + size_net_ekl + eklen + EVP_MAX_IV_LENGTH) ;

	if (out == NULL)
		return false;

	net_ekl = htonl(eklen);
	memcpy((unsigned char*)out + out_offset, &net_ekl, size_net_ekl);
	out_offset += size_net_ekl;

	memcpy((unsigned char*)out + out_offset, ek, eklen);
	out_offset += eklen;

	memcpy((unsigned char*)out + out_offset, iv, EVP_MAX_IV_LENGTH);
	out_offset += EVP_MAX_IV_LENGTH;

	// now encrypt actual data
	if(!EVP_SealUpdate(ctx, (unsigned char*) out + out_offset, &out_currOffset, (unsigned char*) in, inlen))
	{
		free(out) ;
		out = NULL ;
		return false;
	}

	// move along to partial block space
	out_offset += out_currOffset;

	// add padding
	if(!EVP_SealFinal(ctx, (unsigned char*) out + out_offset, &out_currOffset))
	{
		free(out) ;
		out = NULL ;
		return false;
	}

	// move to end
	out_offset += out_currOffset;
    
	// make sure offset has not gone passed valid memory bounds
	if(out_offset > max_outlen) 
	{
		free(out) ;
		out = NULL ;
		return false;
	}

	// free encrypted key data
	free(ek);

	EVP_CIPHER_CTX_free(ctx);
    
	outlen = out_offset;
	return true;
}

bool GxsSecurity::encrypt(uint8_t *& out, uint32_t &outlen, const uint8_t *in, uint32_t inlen, const std::vector<RsTlvPublicRSAKey> &keys)
{
#ifdef DISTRIB_DEBUG
	std::cerr << "GxsSecurity::encrypt() " << std::endl;
#endif
	// Encrypts (in,inlen) into (out,outlen) using the given RSA public key.
	// The format of the encrypted data is:
	//
	//   [--- ID ---|--- number of encrypted keys---|  n * (--- Encrypted session keys ---)    |---      IV     ---|---- Encrypted data ---]
	//      2 bytes              2 byte = n                            256 bytes                  EVP_MAX_IV_LENGTH       Rest of packet
	//

	out = NULL ;
	EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
	std::vector<EVP_PKEY *> public_keys(keys.size(),NULL);

	try
	{
		for(uint32_t i=0;i<keys.size();++i)
		{
			RSA *tmpkey = ::extractPublicKey(keys[i]) ;
			RSA *rsa_publish_pub = RSAPublicKey_dup(tmpkey) ;
			RSA_free(tmpkey) ;

			if(rsa_publish_pub  != NULL)
			{
				public_keys[i] = EVP_PKEY_new();
				EVP_PKEY_assign_RSA(public_keys[i], rsa_publish_pub);
			}
			else
			{
				std::cerr << "GxsSecurity(): Could not generate public key for key id " << keys[i].keyId << std::endl;
				throw std::runtime_error("Cannot extract public key") ;
			}
		}

		unsigned char iv[EVP_MAX_IV_LENGTH];

		std::vector<unsigned char *> ek(keys.size(),NULL) ;
		std::vector<int> eklen(keys.size(),0) ;

		for(uint32_t i=0;i<keys.size();++i)
		{
			int max_evp_key_size = EVP_PKEY_size(public_keys[i]);

			if(max_evp_key_size != MULTI_ENCRYPTION_FORMAT_v001_ENCRYPTED_KEY_SIZE)
				throw std::runtime_error("EVP_PKEY_size should be equal to 256. It's not!") ;

			ek[i] = (unsigned char*)rs_malloc(max_evp_key_size);
			if(ek[i] == NULL)
				throw std::runtime_error("malloc error on encrypted keys") ;
		}

		const EVP_CIPHER *cipher = EVP_aes_128_cbc();
		int cipher_block_size = EVP_CIPHER_block_size(cipher);

		// intialize context and send store encrypted cipher in ek
		if(!EVP_SealInit(ctx, EVP_aes_128_cbc(), ek.data(), eklen.data(), iv, public_keys.data(), keys.size()))
			return false;

		// now we can release the encryption keys
		for(uint32_t i=0;i<public_keys.size();++i)
			EVP_PKEY_free(public_keys[i]) ;
		public_keys.clear() ;

		int total_ek_size = MULTI_ENCRYPTION_FORMAT_v001_ENCRYPTED_KEY_SIZE * keys.size() ;

		int max_outlen = MULTI_ENCRYPTION_FORMAT_v001_HEADER_SIZE + MULTI_ENCRYPTION_FORMAT_v001_NUMBER_OF_KEYS_SIZE + total_ek_size + EVP_MAX_IV_LENGTH + (inlen + cipher_block_size) ;

		// now assign memory to out accounting for data, and cipher block size, key length, and key length val
		out = (uint8_t*)rs_malloc(max_outlen);

		if(out == NULL)
			return false ;

		int out_offset = 0;

		// header

		out[out_offset++] =  MULTI_ENCRYPTION_FORMAT_v001_HEADER       & 0xff ;
		out[out_offset++] = (MULTI_ENCRYPTION_FORMAT_v001_HEADER >> 8) & 0xff ;

		// number of keys

		out[out_offset++] =   keys.size()       & 0xff ;
		out[out_offset++] =  (keys.size() >> 8) & 0xff ;

		// encrypted keys, each preceeded with its length

		for(uint32_t i=0;i<keys.size();++i)
		{
			if(eklen[i] != MULTI_ENCRYPTION_FORMAT_v001_ENCRYPTED_KEY_SIZE)
			{
				std::cerr << "(EE) eklen[i]=" << eklen[i] << " in " << __PRETTY_FUNCTION__ << " for key id " << keys[i].keyId << ". This is unexpected. Cannot encrypt." << std::endl;
				throw std::runtime_error("Encryption error") ;
			}

			memcpy((unsigned char*)out + out_offset, ek[i],eklen[i]) ;
			out_offset += eklen[i] ;
		}

		memcpy((unsigned char*)out + out_offset, iv, EVP_MAX_IV_LENGTH);
		out_offset += EVP_MAX_IV_LENGTH;

		int out_currOffset = 0;

		// now encrypt actual data
		if(!EVP_SealUpdate(ctx, (unsigned char*) out + out_offset, &out_currOffset, (unsigned char*) in, inlen))
			throw std::runtime_error("Encryption error in SealUpdate()") ;

		// move along to partial block space
		out_offset += out_currOffset;

		// add padding
		if(!EVP_SealFinal(ctx, (unsigned char*) out + out_offset, &out_currOffset))
			throw std::runtime_error("Encryption error in SealFinal()") ;

		// move to end
		out_offset += out_currOffset;

		// make sure offset has not gone passed valid memory bounds

		if(out_offset > max_outlen)
			throw std::runtime_error("Memory used by encryption exceeds allocated memory block") ;

		// free encrypted key data

		for(uint32_t i=0;i<keys.size();++i)
			if(ek[i]) free(ek[i]);

		outlen = out_offset;

		EVP_CIPHER_CTX_free(ctx);
		return true;
	}
	catch(std::exception& e)
	{
		std::cerr << "(EE) Exception caught while encrypting: " << e.what() << std::endl;

		EVP_CIPHER_CTX_free(ctx);

		if(out) free(out) ;
		out = NULL ;

		for(uint32_t i=0;i<public_keys.size();++i)
			EVP_PKEY_free(public_keys[i]) ;
		public_keys.clear() ;

		return false ;
	}
}

bool GxsSecurity::decrypt(uint8_t *& out, uint32_t & outlen, const uint8_t *in, uint32_t inlen, const RsTlvPrivateRSAKey &key)
{
	// Decrypts (in,inlen) into (out,outlen) using the given RSA public key.
	// The format of the encrypted data (in) is:
	//
	//   [--- Encrypted session key length ---|--- Encrypted session key ---|--- IV ---|---- Encrypted data ---]
	//
        // This method can be used to decrypt multi-encrypted data, if passing he correct encrypted key block (corresponding to the given key)

    out = NULL ;
#ifdef GXS_SECURITY_DEBUG
	std::cerr << "GxsSecurity::decrypt() " << std::endl;
#endif
	RSA *rsa_publish = extractPrivateKey(key) ;
	EVP_PKEY *privateKey = NULL;

	//RSA* rsa_publish = EVP_PKEY_get1_RSA(privateKey);
	//rsa_publish_pub = RSAPublicKey_dup(rsa_publish);

	if(rsa_publish != NULL)
	{
		privateKey = EVP_PKEY_new();
		EVP_PKEY_assign_RSA(privateKey, rsa_publish);
	}
	else
	{
#ifdef GXS_SECURITY_DEBUG
		std::cerr << "GxsSecurity(): Could not generate RSA private key " << key.keyId << std::endl;
#endif
		return false;
	}


    EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
    int eklen = 0, net_ekl = 0;
	unsigned char *ek = (unsigned char*)rs_malloc(EVP_PKEY_size(privateKey));
    
    if(ek == NULL)
        return false ;
    
    unsigned char iv[EVP_MAX_IV_LENGTH];

    int in_offset = 0, out_currOffset = 0;
    int size_net_ekl = sizeof(net_ekl);

    memcpy(&net_ekl, (unsigned char*)in, size_net_ekl);
    eklen = ntohl(net_ekl);
    in_offset += size_net_ekl;

	// Conservative limits to detect weird errors due to corrupted encoding.
	if(eklen < 0 || eklen > 512 || eklen+in_offset > (int)inlen)
	{
		std::cerr << "Error while deserialising encryption key length: eklen = " << std::dec << eklen << ". Giving up decryption." << std::endl;
		free(ek);
		return false;
	}

    memcpy(ek, (unsigned char*)in + in_offset, eklen);
    in_offset += eklen;

    memcpy(iv, (unsigned char*)in + in_offset, EVP_MAX_IV_LENGTH);
    in_offset += EVP_MAX_IV_LENGTH;

    const EVP_CIPHER* cipher = EVP_aes_128_cbc();

    if(!EVP_OpenInit(ctx, cipher, ek, eklen, iv, privateKey))
    {
        std::cerr << "(EE) Cannot decrypt data. Most likely reason: private GXS key is missing." << std::endl;
        return false;
    }

	 if(inlen < (uint32_t)in_offset)
	 {
		 std::cerr << "Severe error in " << __PRETTY_FUNCTION__ << ": cannot encrypt. " << std::endl;
		 return false ;
	 }
    out = (uint8_t*)rs_malloc(inlen - in_offset);

    if(out == NULL)
         return false;

    if(!EVP_OpenUpdate(ctx, (unsigned char*) out, &out_currOffset, (unsigned char*)in + in_offset, inlen - in_offset))
	 {
         free(out) ;
		 out = NULL ;
		 return false;
	 }

    outlen = out_currOffset;

    if(!EVP_OpenFinal(ctx, (unsigned char*)out + out_currOffset, &out_currOffset))
	 {
         free(out) ;
		 out = NULL ;
		 return false;
	 }

    outlen += out_currOffset;
    free(ek);

	EVP_CIPHER_CTX_free(ctx);
	 return true;
}

bool GxsSecurity::decrypt(uint8_t *& out, uint32_t & outlen, const uint8_t *in, uint32_t inlen, const std::vector<RsTlvPrivateRSAKey> &keys)
{
        // Decrypts (in,inlen) into (out,outlen) using one of the given RSA public keys, trying them all in a row.
        // The format of the encrypted data is:
        //
        //   [--- ID ---|--- number of encrypted keys---|  n * (--- Encrypted session keys ---)    |---      IV     ---|---- Encrypted data ---]
    	//      2 bytes              2 byte = n                            256 bytes                  EVP_MAX_IV_LENGTH       Rest of packet
        //
        // This method can be used to decrypt multi-encrypted data, if passing he correct encrypted key block (corresponding to the given key)

#ifdef DISTRIB_DEBUG
	std::cerr << "GxsSecurity::decrypt() " << std::endl;
#endif
	EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
    
    try
    {
		out = NULL ;
        
	    // check that the input block has a valid format.

	    uint32_t offset = 0 ;
	    uint16_t format_id = in[offset] + (in[offset+1] << 8) ;

	    if(format_id != MULTI_ENCRYPTION_FORMAT_v001_HEADER)
	    {
		    std::cerr << "Unrecognised format in encrypted block. Header id = " << std::hex << format_id << std::dec << std::endl;
		    throw std::runtime_error("Unrecognised format in encrypted block.") ; 
	    }
	    offset += MULTI_ENCRYPTION_FORMAT_v001_HEADER_SIZE;

	    // read number of encrypted keys

	    uint32_t number_of_keys = in[offset] + (in[offset+1] << 8) ;
	    offset += MULTI_ENCRYPTION_FORMAT_v001_NUMBER_OF_KEYS_SIZE;

	    // reach the actual data offset

	    uint32_t encrypted_keys_offset  = offset ;
	    uint32_t encrypted_block_size   = 0 ;

	    uint32_t IV_offset =  offset + number_of_keys * MULTI_ENCRYPTION_FORMAT_v001_ENCRYPTED_KEY_SIZE ;
	    uint32_t encrypted_block_offset =  IV_offset + EVP_MAX_IV_LENGTH ;

	    // read IV offset

	    if(encrypted_block_offset >= inlen)
		    throw std::runtime_error("Offset error") ;
                
	    encrypted_block_size = inlen - encrypted_block_offset ;
#ifdef GXS_SECURITY_DEBUG
	    std::cerr << "  number of keys in envelop: " << number_of_keys << std::endl;
	    std::cerr << "  IV offset                : " << IV_offset << std::endl;
	    std::cerr << "  encrypted block offset   : " << encrypted_block_offset << std::endl;
	    std::cerr << "  encrypted block size     : " << encrypted_block_size << std::endl;
#endif

	    // decrypt

	    bool succeed = false;

	    for(uint32_t j=0;j<keys.size() && !succeed;++j)
	    {
		    RSA *rsa_private = extractPrivateKey(keys[j]) ;
		    EVP_PKEY *privateKey = NULL;

#ifdef GXS_SECURITY_DEBUG
		    std::cerr << "  trying key " << keys[j].keyId << std::endl;
#endif

		    if(rsa_private != NULL)
		    {
			    privateKey = EVP_PKEY_new();
			    EVP_PKEY_assign_RSA(privateKey, rsa_private);
		    }
		    else
		    {
			    RSA_free(rsa_private) ;
			    std::cerr << "(EE) Cannot extract private key from key Id " << keys[j].keyId << ". This is a bug. Non owned key?"  << std::endl;
			    continue ;
		    }

		    for(uint32_t i=0;i<number_of_keys && !succeed;++i)
		    {
			    succeed = EVP_OpenInit(ctx, EVP_aes_128_cbc(),in + encrypted_keys_offset + i*MULTI_ENCRYPTION_FORMAT_v001_ENCRYPTED_KEY_SIZE , MULTI_ENCRYPTION_FORMAT_v001_ENCRYPTED_KEY_SIZE, in+IV_offset, privateKey);

			if(!succeed)
					EVP_CIPHER_CTX_reset(ctx);
                            
#ifdef GXS_SECURITY_DEBUG
			    std::cerr << "    encrypted key at offset " << encrypted_keys_offset + i*MULTI_ENCRYPTION_FORMAT_v001_ENCRYPTED_KEY_SIZE << ": " << succeed << std::endl;
#endif
		    }

		    EVP_PKEY_free(privateKey) ;
	    }

	    if(!succeed)
		    throw std::runtime_error("No matching key available.") ;

#ifdef GXS_SECURITY_DEBUG
	    std::cerr << "  now decrypting with the matching key." << std::endl;
#endif

	    out = (uint8_t*)rs_malloc(encrypted_block_size) ;

	    if(out == NULL)
		    throw std::runtime_error("Memory allocation error") ;

	    int out_currOffset = 0 ;

	    if(!EVP_OpenUpdate(ctx, (unsigned char*) out, &out_currOffset, (unsigned char*)in + encrypted_block_offset, encrypted_block_size))
		    throw std::runtime_error("Decryption error in EVP_OpenUpdate") ;

	    outlen = out_currOffset;

	    if(!EVP_OpenFinal(ctx, (unsigned char*)out + out_currOffset, &out_currOffset))
		    throw std::runtime_error("Decryption error in EVP_OpenFinal") ;

	    outlen += out_currOffset;
        
#ifdef GXS_SECURITY_DEBUG
        	std::cerr << "  successfully decrypted block of size " << outlen << std::endl;
#endif
	    EVP_CIPHER_CTX_free(ctx);
	    return true;
    }
    catch(std::exception& e)
    {
        // cleanup and return false
        
#ifdef GXS_SECURITY_DEBUG
        std::cerr << "  (EE) error caught: " << e.what() << std::endl;
#endif
        if(out)
        {
            free(out) ;
            out = NULL ;
        }
        
	EVP_CIPHER_CTX_free(ctx);
        return false;
    }
}
bool GxsSecurity::validateNxsGrp(const RsNxsGrp& grp, const RsTlvKeySignature& sign, const RsTlvPublicRSAKey &key)
{
#ifdef GXS_SECURITY_DEBUG
	std::cerr << "GxsSecurity::validateNxsGrp()";
	std::cerr << std::endl;
	std::cerr << "RsNxsGrp :";
	std::cerr << std::endl;
	const_cast<RsNxsGrp*>(&grp)->print(std::cerr, 10);
	std::cerr << std::endl;
#endif

	RsGxsGrpMetaData& grpMeta = *(grp.metaData);

	/********************* check signature *******************/

	/* check signature timeperiod */
	if ((grpMeta.mPublishTs < key.startTS) || (key.endTS != 0 && grpMeta.mPublishTs > key.endTS))
	{
#ifdef GXS_SECURITY_DEBUG
		std::cerr << " GxsSecurity::validateNxsMsg() TS out of range";
		std::cerr << std::endl;
#endif
		return false;
	}

	/* decode key */
	const unsigned char *keyptr = (const unsigned char *) key.keyData.bin_data;
	long keylen = key.keyData.bin_len;
	unsigned int siglen = sign.signData.bin_len;
	unsigned char *sigbuf = (unsigned char *) sign.signData.bin_data;

#ifdef DISTRIB_DEBUG
	std::cerr << "GxsSecurity::validateNxsMsg() Decode Key";
	std::cerr << " keylen: " << keylen << " siglen: " << siglen;
	std::cerr << std::endl;
#endif

	/* extract admin key */
	RSA *rsakey = d2i_RSAPublicKey(NULL, &(keyptr), keylen);

	if (!rsakey)
	{
#ifdef GXS_SECURITY_DEBUG
		std::cerr << "GxsSecurity::validateNxsGrp()";
		std::cerr << " Invalid RSA Key";
		std::cerr << std::endl;

		key.print(std::cerr, 10);
#endif
	}

	std::vector<uint32_t> api_versions_to_check ;
	api_versions_to_check.push_back(RS_GXS_GRP_META_DATA_VERSION_ID_0002) ;	// put newest first, for debug info purpose
	api_versions_to_check.push_back(RS_GXS_GRP_META_DATA_VERSION_ID_0001) ;

	RsTlvKeySignatureSet signSet = grpMeta.signSet;
	grpMeta.signSet.TlvClear();
    
	int signOk =0;
	EVP_PKEY *signKey = EVP_PKEY_new();
	EVP_PKEY_assign_RSA(signKey, rsakey);


	for(uint32_t i=0;i<api_versions_to_check.size() && 0==signOk;++i)
	{
		uint32_t metaDataLen = grpMeta.serial_size(api_versions_to_check[i]);
		uint32_t allGrpDataLen = metaDataLen + grp.grp.bin_len;

		RsTemporaryMemory metaData(metaDataLen) ;
		RsTemporaryMemory allGrpData(allGrpDataLen) ;// msgData + metaData

		grpMeta.serialise(metaData, metaDataLen,api_versions_to_check[i]);

		// copy msg data and meta in allmsgData buffer
		memcpy(allGrpData, grp.grp.bin_data, grp.grp.bin_len);
		memcpy(allGrpData+(grp.grp.bin_len), metaData, metaDataLen);

		/* calc and check signature */
		EVP_MD_CTX *mdctx = EVP_MD_CTX_create();

		EVP_VerifyInit(mdctx, EVP_sha1());
		EVP_VerifyUpdate(mdctx, allGrpData, allGrpDataLen);
		signOk = EVP_VerifyFinal(mdctx, sigbuf, siglen, signKey);
		EVP_MD_CTX_destroy(mdctx);

                if(i>0)
		std::cerr << "(WW) Checking group signature with old api version " << i+1 << " : tag " << std::hex << api_versions_to_check[i] << std::dec << " result: " << signOk << std::endl;
	}

	/* clean up */
	EVP_PKEY_free(signKey);

	// restore data

	grpMeta.signSet = signSet;

	if (signOk == 1)
	{
#ifdef GXS_SECURITY_DEBUG
		std::cerr << "GxsSecurity::validateNxsGrp() Signature OK";
		std::cerr << std::endl;
#endif
		return true;
	}

#ifdef GXS_SECURITY_DEBUG
	std::cerr << "GxsSecurity::validateNxsGrp() Signature invalid";
	std::cerr << std::endl;
#endif

	return false;
}

void GxsSecurity::createPublicKeysFromPrivateKeys(RsTlvSecurityKeySet& keyset)
{
    for( std::map<RsGxsId, RsTlvPrivateRSAKey>::const_iterator it = keyset.private_keys.begin(); it != keyset.private_keys.end() ; ++it)
        if(keyset.public_keys.find(it->second.keyId) == keyset.public_keys.end())
        {
            RsTlvPublicRSAKey pub_key ;
            
            if(!extractPublicKey(it->second,pub_key))
            {
                std::cerr << "(EE) ERROR when trying to generate public key from private key for ID " << it->second.keyId << ". This is probably a bug with security implications." << std::endl;
                continue ;
            }
            
            keyset.public_keys[it->second.keyId] = pub_key ;
            
            std::cerr << "(II) Generated missing public key for ID " << it->second.keyId << " from private key." << std::endl;
        }
}