// See the file "COPYING" in the main distribution directory for copyright.

#include "zeek/analyzer/protocol/smb/SMB.h"

namespace zeek::analyzer::smb {

// This was 1<<17 originally but was changed due to larger messages
// being seen.
#define SMB_MAX_LEN (1 << 18)

SMB_Analyzer::SMB_Analyzer(Connection* conn) : analyzer::tcp::TCP_ApplicationAnalyzer("SMB", conn) {
    chunks = 0;
    interp = new binpac::SMB::SMB_Conn(this);
    need_sync = true;
}

SMB_Analyzer::~SMB_Analyzer() { delete interp; }

void SMB_Analyzer::Done() {
    TCP_ApplicationAnalyzer::Done();

    interp->FlowEOF(true);
    interp->FlowEOF(false);
}

void SMB_Analyzer::EndpointEOF(bool is_orig) {
    TCP_ApplicationAnalyzer::EndpointEOF(is_orig);

    interp->FlowEOF(is_orig);
}

void SMB_Analyzer::Undelivered(uint64_t seq, int len, bool orig) {
    TCP_ApplicationAnalyzer::Undelivered(seq, len, orig);

    NeedResync();
}

bool SMB_Analyzer::HasSMBHeader(int len, const u_char* data) {
    if ( len < 8 )
        return false;

    return (strncmp(reinterpret_cast<const char*>(data) + 4, "\xffSMB", 4) == 0 ||
            strncmp(reinterpret_cast<const char*>(data) + 4, "\xfeSMB", 4) == 0);
}

void SMB_Analyzer::NeedResync() {
    interp->upflow()->flow_buffer()->DiscardData();
    interp->downflow()->flow_buffer()->DiscardData();
    need_sync = true;
}

void SMB_Analyzer::DeliverStream(int len, const u_char* data, bool orig) {
    TCP_ApplicationAnalyzer::DeliverStream(len, data, orig);

    // It we need to resync and we don't have an SMB header, bail!
    if ( need_sync && ! HasSMBHeader(len, data) )
        return;
    else
        need_sync = false;

    try {
        // If we get here, it means we have an SMB header in the message.
        interp->NewData(orig, data, data + len);

        // Let's assume that if there are no binpac exceptions after
        // 3 data chunks that this is probably actually SMB.
        if ( ++chunks == 3 )
            AnalyzerConfirmation();
    } catch ( const binpac::Exception& e ) {
        AnalyzerViolation(util::fmt("Binpac exception: %s", e.what()));
        NeedResync();
    }
}

} // namespace zeek::analyzer::smb
