frameassembly 1.0.1

A Domain-Specific Language (DSL) for writing deterministic network traffic to .pcap files.
Documentation 
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//! OPCUA industrial OT protocol wire builder.

use crate::ast::*;
use crate::builders::WireContext;
use alloc::vec::Vec;

/// Builds an OPC UA Binary Protocol packet payload.
pub fn build_opcua_payload(
    _ctx: &WireContext,
    spec: &OpcuaSpec,
    payload_bytes: &[u8],
) -> Vec<u8> {
    let msg_type_str = spec.msg_type.unwrap_or("HEL").to_ascii_uppercase();
    let msg_bytes = match msg_type_str.as_str() {
        "HEL" => *b"HEL",
        "ACK" => *b"ACK",
        "OPN" => *b"OPN",
        "CLO" => *b"CLO",
        "MSG" => *b"MSG",
        "ERR" => *b"ERR",
        _ => *b"HEL",
    };

    let chunk_type = spec.chunk_type.unwrap_or('F') as u8;

    let mut body = Vec::new();
    if msg_bytes == *b"HEL" {
        // Hello Message Body (24 bytes)
        body.extend_from_slice(&0u32.to_le_bytes()); // Version 0
        body.extend_from_slice(&65536u32.to_le_bytes()); // ReceiveBufferSize
        body.extend_from_slice(&65536u32.to_le_bytes()); // SendBufferSize
        body.extend_from_slice(&16777216u32.to_le_bytes()); // MaxMessageSize (16MB)
        body.extend_from_slice(&5000u32.to_le_bytes()); // MaxChunkCount
        body.extend_from_slice(&0u32.to_le_bytes()); // EndpointUrl length 0
    } else if msg_bytes == *b"ACK" {
        // Acknowledge Message Body (20 bytes)
        body.extend_from_slice(&0u32.to_le_bytes()); // Version 0
        body.extend_from_slice(&65536u32.to_le_bytes()); // ReceiveBufferSize
        body.extend_from_slice(&65536u32.to_le_bytes()); // SendBufferSize
        body.extend_from_slice(&16777216u32.to_le_bytes()); // MaxMessageSize
        body.extend_from_slice(&5000u32.to_le_bytes()); // MaxChunkCount
    } else {
        // Message / OpenSecureChannel Body
        body.extend_from_slice(&spec.secure_channel_id.unwrap_or(1).to_le_bytes());
        body.extend_from_slice(&spec.token_id.unwrap_or(1).to_le_bytes());
        body.extend_from_slice(&spec.seq_num.unwrap_or(1).to_le_bytes());
        body.extend_from_slice(&spec.req_id.unwrap_or(1).to_le_bytes());
    }

    if !payload_bytes.is_empty() {
        body.extend_from_slice(payload_bytes);
    }

    let total_size = (8 + body.len()) as u32;
    let mut pkt = Vec::with_capacity(total_size as usize);
    pkt.extend_from_slice(&msg_bytes);
    pkt.push(chunk_type);
    pkt.extend_from_slice(&total_size.to_le_bytes());
    pkt.extend_from_slice(&body);
    pkt
}