/* Copyright (C) 2020 Open Information Security Foundation
 *
 * You can copy, redistribute or modify this Program under the terms of
 * the GNU General Public License version 2 as published by the Free
 * Software Foundation.
 *
 * 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
 * version 2 along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */
use crate::dcerpc::dcerpc::{
    BindCtxItem, DCERPCBind, DCERPCBindAck, DCERPCBindAckResult, DCERPCHdr, DCERPCRequest, Uuid,
};
use crate::dcerpc::dcerpc_udp::DCERPCHdrUdp;
use nom7::bytes::streaming::take;
use nom7::combinator::cond;
use nom7::number::complete::{le_u16, le_u32, le_u8, u16, u32};
use nom7::number::Endianness;
use nom7::multi::count;
use nom7::IResult;

fn uuid_to_vec(uuid: Uuid) -> Vec<u8> {
    let mut uuidtmp = uuid;
    let mut vect: Vec<u8> = Vec::new();
    vect.append(&mut uuidtmp.time_low);
    vect.append(&mut uuidtmp.time_mid);
    vect.append(&mut uuidtmp.time_hi_and_version);
    vect.push(uuidtmp.clock_seq_hi_and_reserved);
    vect.push(uuidtmp.clock_seq_low);
    vect.append(&mut uuidtmp.node);
    vect
}

fn assemble_uuid(uuid: Uuid) -> Vec<u8> {
    let mut uuidtmp = uuid;
    let mut vect: Vec<u8> = Vec::new();
    uuidtmp.time_low.reverse();
    uuidtmp.time_mid.reverse();
    uuidtmp.time_hi_and_version.reverse();
    vect.append(&mut uuidtmp.time_low);
    vect.append(&mut uuidtmp.time_mid);
    vect.append(&mut uuidtmp.time_hi_and_version);
    vect.push(uuidtmp.clock_seq_hi_and_reserved);
    vect.push(uuidtmp.clock_seq_low);
    vect.append(&mut uuidtmp.node);

    vect
}

fn parse_uuid(i: &[u8]) -> IResult<&[u8], Uuid> {
    let (i, time_low) = take(4_usize)(i)?;
    let (i, time_mid) = take(2_usize)(i)?;
    let (i, time_hi_and_version) = take(2_usize)(i)?;
    let (i, clock_seq_hi_and_reserved) = le_u8(i)?;
    let (i, clock_seq_low) = le_u8(i)?;
    let (i, node) = take(6_usize)(i)?;
    let uuid = Uuid {
        time_low: time_low.to_vec(),
        time_mid: time_mid.to_vec(),
        time_hi_and_version: time_hi_and_version.to_vec(),
        clock_seq_hi_and_reserved,
        clock_seq_low,
        node: node.to_vec(),
    };
    Ok((i, uuid))
}

pub(super) fn parse_dcerpc_udp_header(i: &[u8]) -> IResult<&[u8], DCERPCHdrUdp> {
    let (i, rpc_vers) = le_u8(i)?;
    let (i, pkt_type) = le_u8(i)?;
    let (i, flags1) = le_u8(i)?;
    let (i, flags2) = le_u8(i)?;
    let (i, drep) = take(3_usize)(i)?;
    let endianness = if drep[0] == 0 { Endianness::Big } else { Endianness::Little };
    let (i, serial_hi) = le_u8(i)?;
    let (i, objectuuid) = take(16_usize)(i)?;
    let (i, interfaceuuid) = take(16_usize)(i)?;
    let (i, activityuuid) = take(16_usize)(i)?;
    let (i, server_boot) = u32(endianness)(i)?;
    let (i, if_vers) = u32(endianness)(i)?;
    let (i, seqnum) = u32(endianness)(i)?;
    let (i, opnum) = u16(endianness)(i)?;
    let (i, ihint) = u16(endianness)(i)?;
    let (i, ahint) = u16(endianness)(i)?;
    let (i, fraglen) = u16(endianness)(i)?;
    let (i, fragnum) = u16(endianness)(i)?;
    let (i, auth_proto) = le_u8(i)?;
    let (i, serial_lo) = le_u8(i)?;
    let header = DCERPCHdrUdp {
        rpc_vers,
        pkt_type,
        flags1,
        flags2,
        drep: drep.to_vec(),
        serial_hi,
        objectuuid: match parse_uuid(objectuuid) {
            Ok((_, vect)) => assemble_uuid(vect),
            Err(_e) => {
                SCLogDebug!("{}", _e);
                vec![0]
            },
        },
        interfaceuuid: match parse_uuid(interfaceuuid) {
            Ok((_, vect)) => assemble_uuid(vect),
            Err(_e) => {
                SCLogDebug!("{}", _e);
                vec![0]
            },
        },
        activityuuid: match parse_uuid(activityuuid){
            Ok((_, vect)) => assemble_uuid(vect),
            Err(_e) => {
                SCLogDebug!("{}", _e);
                vec![0]
            },
        },
        server_boot,
        if_vers,
        seqnum,
        opnum,
        ihint,
        ahint,
        fraglen,
        fragnum,
        auth_proto,
        serial_lo,
    };
    Ok((i, header))
}

pub(super) fn parse_dcerpc_bindack_result(i: &[u8]) -> IResult<&[u8], DCERPCBindAckResult> {
    let (i, ack_result) = le_u16(i)?;
    let (i,  ack_reason) = le_u16(i)?;
    let (i,  transfer_syntax) = take(16_usize)(i)?;
    let (i,  syntax_version) = le_u32(i)?;
    let result = DCERPCBindAckResult {
        ack_result,
        ack_reason,
        transfer_syntax: transfer_syntax.to_vec(),
        syntax_version,
    };
    Ok((i, result))
}

pub(super) fn parse_dcerpc_bindack(i: &[u8]) -> IResult<&[u8], DCERPCBindAck> {
    let (i, _max_xmit_frag) = le_u16(i)?;
    let (i, _max_recv_frag) = le_u16(i)?;
    let (i, _assoc_group) = take(4_usize)(i)?;
    let (i, sec_addr_len) = le_u16(i)?;
    let (i, _) = take(sec_addr_len)(i)?;
    let (i, _) = cond((sec_addr_len.wrapping_add(2)) % 4 != 0, |b| take(4 - (sec_addr_len.wrapping_add(2)) % 4)(b))(i)?;
    let (i, numctxitems) = le_u8(i)?;
    let (i, _) = take(3_usize)(i)?; // Padding
    let (i, ctxitems) = count(parse_dcerpc_bindack_result, numctxitems as usize)(i)?;
    let result = DCERPCBindAck {
        accepted_uuid_list: Vec::new(),
        sec_addr_len,
        numctxitems,
        ctxitems,
    };
    Ok((i, result))
}

pub(super) fn parse_bindctx_item(i: &[u8], endianness: Endianness) -> IResult<&[u8], BindCtxItem> {
    let (i, ctxid) = u16(endianness)(i)?;
    let (i, _num_trans_items) = le_u8(i)?;
    let (i, _) = take(1_usize)(i)?; // Reserved bit
    let (i, uuid) = take(16_usize)(i)?;
    let (i, version) = u16(endianness)(i)?;
    let (i, versionminor) = u16(endianness)(i)?;
    let (i, _) = take(20_usize)(i)?;
    let result = BindCtxItem {
        ctxid,
        // UUID parsing for TCP seems to change as per endianness
        uuid: match parse_uuid(uuid) {
            Ok((_, vect)) => match endianness {
                Endianness::Little => assemble_uuid(vect),
                _ => uuid_to_vec(vect),
            },
            // Shouldn't happen
            Err(_e) => {vec![0]},
        },
        version,
        versionminor,
    };
    Ok((i, result))
}

pub(super) fn parse_dcerpc_bind(i: &[u8]) -> IResult<&[u8], DCERPCBind> {
    let (i, _max_xmit_frag) = le_u16(i)?;
    let (i, _max_recv_frag) = le_u16(i)?;
    let (i, _assoc_group_id) = le_u32(i)?;
    let (i, numctxitems) = le_u8(i)?;
    let (i, _) = take(3_usize)(i)?;
    let result = DCERPCBind {
        numctxitems,
        uuid_list: Vec::new(),
    };
    Ok((i, result))
}

pub(super) fn parse_dcerpc_header(i: &[u8]) -> IResult<&[u8], DCERPCHdr> {
    let (i, rpc_vers) = le_u8(i)?;
    let (i, rpc_vers_minor) = le_u8(i)?;
    let (i, hdrtype) = le_u8(i)?;
    let (i, pfc_flags) = le_u8(i)?;
    let (i, packed_drep) = take(4_usize)(i)?;
    let endianness = if packed_drep[0] & 0x10 == 0 { Endianness::Big } else { Endianness::Little };
    let (i, frag_length) = u16(endianness)(i)?;
    let (i, auth_length) = u16(endianness)(i)?;
    let (i, call_id) = u32(endianness)(i)?;
    let header = DCERPCHdr {
        rpc_vers,
        rpc_vers_minor,
        hdrtype,
        pfc_flags,
        packed_drep: packed_drep.to_vec(),
        frag_length,
        auth_length,
        call_id,
    };
    Ok((i, header))
}

pub(super) fn parse_dcerpc_request(i: &[u8], endianness: Endianness) -> IResult<&[u8], DCERPCRequest> {
    let (i, _pad) = take(4_usize)(i)?;
    let (i, ctxid) = u16(endianness)(i)?;
    let (i, opnum) = u16(endianness)(i)?;
    let req = DCERPCRequest {
        ctxid,
        opnum,
        first_request_seen: 1,
    };
    Ok((i, req))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_parse_uuid() {
        let uuid: &[u8] = &[
            0xb8, 0x4a, 0x9f, 0x4d, 0x1c, 0x7d, 0xcf, 0x11, 0x86, 0x1e, 0x00, 0x20, 0xaf, 0x6e,
            0x7c, 0x57,
        ];
        let expected_uuid = Uuid {
            time_low: vec![0xb8, 0x4a, 0x9f, 0x4d],
            time_mid: vec![0x1c, 0x7d],
            time_hi_and_version: vec![0xcf, 0x11],
            clock_seq_hi_and_reserved: 0x86,
            clock_seq_low: 0x1e,
            node: vec![0x00, 0x20, 0xaf, 0x6e, 0x7c, 0x57],
        };
        let (_remainder, parsed_uuid) = parse_uuid(uuid).unwrap();
        assert_eq!(expected_uuid, parsed_uuid);
    }

    #[test]
    fn test_assemble_uuid() {
        let uuid = Uuid {
            time_low: vec![0xb8, 0x4a, 0x9f, 0x4d],
            time_mid: vec![0x1c, 0x7d],
            time_hi_and_version: vec![0xcf, 0x11],
            clock_seq_hi_and_reserved: 0x86,
            clock_seq_low: 0x1e,
            node: vec![0x00, 0x20, 0xaf, 0x6e, 0x7c, 0x57],
        };
        let expected_val = vec![
            0x4d, 0x9f, 0x4a, 0xb8, 0x7d, 0x1c, 0x11, 0xcf, 0x86, 0x1e, 0x00, 0x20, 0xaf, 0x6e,
            0x7c, 0x57,
        ];
        assert_eq!(expected_val, assemble_uuid(uuid));
    }

    #[test]
    fn test_parse_dcerpc_udp_header() {
        let dcerpcheader: &[u8] = &[
            0x04, 0x00, 0x08, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xb8, 0x4a, 0x9f, 0x4d,
            0x1c, 0x7d, 0xcf, 0x11, 0x86, 0x1e, 0x00, 0x20, 0xaf, 0x6e, 0x7c, 0x57, 0x86, 0xc2,
            0x37, 0x67, 0xf7, 0x1e, 0xd1, 0x11, 0xbc, 0xd9, 0x00, 0x60, 0x97, 0x92, 0xd2, 0x6c,
            0x79, 0xbe, 0x01, 0x34, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0xff, 0xff, 0xff, 0xff, 0x68, 0x00, 0x00, 0x00, 0x0a, 0x00,
        ];
        let (_remainder, header) = parse_dcerpc_udp_header(dcerpcheader).unwrap();
        let expected_activityuuid = vec![
            0x67, 0x37, 0xc2, 0x86, 0x1e, 0xf7, 0x11, 0xd1, 0xbc, 0xd9, 0x00, 0x60, 0x97, 0x92,
            0xd2, 0x6c,
        ];
        assert_eq!(0x04, header.rpc_vers);
        assert_eq!(0x00, header.pkt_type);
        assert_eq!(0x08, header.flags1);
        assert_eq!(0x00, header.flags2);
        assert_eq!(vec!(0x10, 0x00, 0x00), header.drep);
        assert_eq!(0x00, header.serial_hi);
        assert_eq!(expected_activityuuid, header.activityuuid);
        assert_eq!(0x3401be79, header.server_boot);
        assert_eq!(0x00000000, header.seqnum);
        assert_eq!(0xffff, header.ihint);
        assert_eq!(0x0068, header.fraglen);
        assert_eq!(0x0a, header.auth_proto);
    }

    #[test]
    fn test_parse_dcerpc_header() {
        let dcerpcheader: &[u8] = &[
            0x05, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00,
        ];
        let (_remainder, header) = parse_dcerpc_header(dcerpcheader).unwrap();
        assert_eq!(5, header.rpc_vers);
        assert_eq!(0, header.rpc_vers_minor);
        assert_eq!(0, header.hdrtype);
        assert_eq!(1024, header.frag_length);
    }

    #[test]
    fn test_parse_dcerpc_bind() {
        let dcerpcbind: &[u8] = &[
            0xd0, 0x16, 0xd0, 0x16, 0x00, 0x00, 0x00, 0x00, 0x18, 0x00, 0x00, 0x00,
        ];
        let (_remainder, bind) = parse_dcerpc_bind(dcerpcbind).unwrap();
        assert_eq!(24, bind.numctxitems);
    }

    #[test]
    fn test_parse_bindctx_item() {
        let dcerpcbind: &[u8] = &[
            0x00, 0x00, 0x01, 0x00, 0x2c, 0xd0, 0x28, 0xda, 0x76, 0x91, 0xf6, 0x6e, 0xcb, 0x0f,
            0xbf, 0x85, 0xcd, 0x9b, 0xf6, 0x39, 0x01, 0x00, 0x03, 0x00, 0x04, 0x5d, 0x88, 0x8a,
            0xeb, 0x1c, 0xc9, 0x11, 0x9f, 0xe8, 0x08, 0x00, 0x2b, 0x10, 0x48, 0x60, 0x02, 0x00,
            0x00, 0x00,
        ];
        let (_remainder, ctxitem) = parse_bindctx_item(dcerpcbind, Endianness::Little).unwrap();
        assert_eq!(0, ctxitem.ctxid);
        assert_eq!(1, ctxitem.version);
        assert_eq!(3, ctxitem.versionminor);
    }
}
