seccon 2017 online CTF writeup (Remote debugging of a micro computer)

trace.js

var fs = require('fs');

var regNames = {
        0: "PC",
        1: "SP",
};
var prevRegs = [
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
];

fs.readFile(process.argv[2], 'utf8', function (err, text) {
        var splitted = text.split("\n").join("").split("+");
        var filtered = splitted
                .filter((s) => {return !s.startsWith("$g");})
                .filter((s) => {return !s.startsWith("$T");})
                .filter((s) => {return !s.startsWith("$s");})
                .filter((s) => {return !s.startsWith("$OK");})
                .filter((s) => {return s.length;});
        for(var s of filtered){
                var currentRegs = [];
                var bytes = s
                        .substr(1)
                        .match(/.{1,2}/g)
                        .slice(0, 64)
                        .map((e) => {return parseInt(e, 16);});
                for(var i = 0; i < 16; i++){
                        var val = 
                                bytes[i * 4] + 
                                (bytes[i * 4 + 1] << 8) + 
                                (bytes[i * 4 + 2] << 16) +
                                (bytes[i * 4 + 3] << 24) ;
                        var name = "R" + i;
                        if(regNames[i]) name = regNames[i];
                        currentRegs.push(val);
                        if(i == 0){
                                console.log(name + ": 0x" + val.toString(16))
                        } else if(prevRegs[i] != val){
                        console.log("\t" + name + 
                                ": 0x" + prevRegs[i].toString(16) + 
                                " -> 0x" + val.toString(16));
                        }
                }
                prevRegs = currentRegs;
                console.log("----");
        }
});