/*
 * Copyright (C) 2001-2012 Jacek Sieka, arnetheduck on gmail point com
 *
 * 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.
 *
 * 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, see <https://www.gnu.org/licenses/>.
 */

#include "stdinc.h"
#include "SSLSocket.h"

#include "format.h"
#include "CryptoManager.h"
#include "LogManager.h"
#include "SettingsManager.h"

#include <openssl/err.h>

namespace dcpp {

#if OPENSSL_VERSION_NUMBER >= 0x10002000L
static const unsigned char alpn_protos_nmdc[] = {
	4, 'n', 'm', 'd', 'c',
};
static const unsigned char alpn_protos_adc[] = {
	3, 'a', 'd', 'c',
};
#endif

SSLSocket::SSLSocket(SSL_CTX* context, Socket::Protocol proto) : ctx(context), ssl(0), nextProto(proto) {

}

void SSLSocket::connect(const string& aIp, const string& aPort) {
    Socket::connect(aIp, aPort);

    waitConnected(0);
}

#if OPENSSL_VERSION_NUMBER < 0x10002000L
static inline int SSL_is_server(SSL *s)
{
    return s->server;
}
#endif

bool SSLSocket::waitConnected(uint32_t millis) {
    if(!ssl) {
        if(!Socket::waitConnected(millis)) {
            return false;
        }
        ssl.reset(SSL_new(ctx));
        if(!ssl)
            checkSSL(-1);

        checkSSL(SSL_set_fd(ssl, sock));
    }

#if OPENSSL_VERSION_NUMBER >= 0x10002000L
    if (nextProto == Socket::PROTO_NMDC) {
        SSL_set_alpn_protos(ssl, alpn_protos_nmdc, sizeof(alpn_protos_nmdc));
    } else if (nextProto == Socket::PROTO_ADC) {
        SSL_set_alpn_protos(ssl, alpn_protos_adc, sizeof(alpn_protos_adc));
    }
#endif

    if(SSL_is_init_finished(ssl)) {
        return true;
    }

    while(true) {
        int ret = SSL_is_server(ssl)?SSL_accept(ssl):SSL_connect(ssl);
        if(ret == 1) {
            dcdebug("Connected to SSL server using %s as %s\n",
                    SSL_get_cipher(ssl), SSL_is_server(ssl) ? "server" : "client");

#if OPENSSL_VERSION_NUMBER >= 0x10002000L
            if (SSL_is_server(ssl)) return true;

            const unsigned char* protocol = 0;
            unsigned int len = 0;
            SSL_get0_alpn_selected(ssl, &protocol, &len);
            if (len != 0)
            {
                if (len == 3 && !memcmp(protocol, "adc", len))
                    proto = PROTO_ADC;
                else if (len == 4 && !memcmp(protocol, "nmdc", len))
                    proto = PROTO_NMDC;
                dcdebug("ALPN negotiated %.*s (%d)\n", len, protocol, proto);
            }
#endif
            return true;
        }
        if(!waitWant(ret, millis)) {
            return false;
        }
    }
}

void SSLSocket::accept(const Socket& listeningSocket) {
    Socket::accept(listeningSocket);

    waitAccepted(0);
}

bool SSLSocket::waitAccepted(uint32_t millis) {
    if(!ssl) {
        if(!Socket::waitAccepted(millis)) {
            return false;
        }
        ssl.reset(SSL_new(ctx));
        if(!ssl)
            checkSSL(-1);

        checkSSL(SSL_set_fd(ssl, sock));
    }

    if(SSL_is_init_finished(ssl)) {
        return true;
    }

    while(true) {
        int ret = SSL_accept(ssl);
        if(ret == 1) {
            dcdebug("Connected to SSL client using %s\n", SSL_get_cipher(ssl));
            return true;
        }
        if(!waitWant(ret, millis)) {
            return false;
        }
    }
}

bool SSLSocket::waitWant(int ret, uint32_t millis) {
    int err = SSL_get_error(ssl, ret);
    switch(err) {
    case SSL_ERROR_WANT_READ:
        return wait(millis, Socket::WAIT_READ) == WAIT_READ;
    case SSL_ERROR_WANT_WRITE:
        return wait(millis, Socket::WAIT_WRITE) == WAIT_WRITE;
        // Check if this is a fatal error...
    default: checkSSL(ret);
    }
    dcdebug("SSL: Unexpected fallthrough");
    // There was no error?
    return true;
}

int SSLSocket::read(void* aBuffer, int aBufLen) {
    if(!ssl) {
        return -1;
    }
    int len = checkSSL(SSL_read(ssl, aBuffer, aBufLen));

    if(len > 0) {
        stats.totalDown += len;
        //dcdebug("In(s): %.*s\n", len, (char*)aBuffer);
    }
    return len;
}

int SSLSocket::write(const void* aBuffer, int aLen) {
    if(!ssl) {
        return -1;
    }
    int ret = checkSSL(SSL_write(ssl, aBuffer, aLen));
    if(ret > 0) {
        stats.totalUp += ret;
        //dcdebug("Out(s): %.*s\n", ret, (char*)aBuffer);
    }
    return ret;
}

int SSLSocket::checkSSL(int ret) {
    if(!ssl) {
        return -1;
    }
    if(ret <= 0) {
        /* inspired by boost.asio (asio/ssl/detail/impl/engine.ipp, function engine::perform) and
           the SSL_get_error doc at <https://www.openssl.org/docs/ssl/SSL_get_error.html>. */
        auto err = SSL_get_error(ssl, ret);
        switch(err) {
        case SSL_ERROR_NONE:        // Fallthrough - YaSSL doesn't for example return an openssl compatible error on recv fail
        case SSL_ERROR_WANT_READ:   // Fallthrough
        case SSL_ERROR_WANT_WRITE:
            return -1;
        case SSL_ERROR_ZERO_RETURN:
            throw SocketException(_("Connection closed"));
        default:
        {
            ssl.reset();
            // @todo replace 80 with MAX_ERROR_SZ or whatever's appropriate for yaSSL in some nice way...
            char errbuf[80];
            throw SSLSocketException(str(F_("SSL Error: %1% (%2%, %3%)") % ERR_error_string(err, errbuf) % ret % err));
        }
        }
    }
    return ret;
}

int SSLSocket::wait(uint32_t millis, int waitFor) {
    if(ssl && (waitFor & Socket::WAIT_READ)) {
        /** @todo Take writing into account as well if reading is possible? */
        char c;
        if(SSL_peek(ssl, &c, 1) > 0)
            return WAIT_READ;
    }
    return Socket::wait(millis, waitFor);
}

bool SSLSocket::isTrusted() const noexcept {
    if(!ssl) {
        return false;
    }

    if(SSL_get_verify_result(ssl) != X509_V_OK) {
        return false;
    }

    X509* cert = SSL_get_peer_certificate(ssl);
    if(!cert) {
        return false;
    }
    X509_free(cert);
    return true;
}

std::string SSLSocket::getCipherName() const noexcept {
    if(!ssl)
        return Util::emptyString;

    return SSL_get_cipher_name(ssl);
}

ByteVector SSLSocket::getKeyprint() const noexcept {
    if(!ssl)
        return ByteVector();
    X509* x509 = SSL_get_peer_certificate(ssl);
    if(!x509)
        return ByteVector();

    return ssl::X509_digest(x509, EVP_sha256());
}

void SSLSocket::shutdown() noexcept {
    if(ssl)
        SSL_shutdown(ssl);
}

void SSLSocket::close() noexcept {
    if(ssl) {
        ssl.reset();
    }
    Socket::shutdown();
    Socket::close();
}

} // namespace dcpp