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seccon 2017 online CTF writeup (Remote debugging of a micro computer)
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("----");
}
});
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