console.log("[+] script started...") if (ObjC.available) { if (Process.isDebuggerAttached() === true) { console.log("[+] Debugger attached, in addition to Frida."); } var a = Process.arch.toString() testFunc() console.log("[+] Device chip: " + a); } else { console.log("[+] Objective-C Runtime not available!"); } console.log("[+] ...script completed") function testFunc(){ var someFunc = Module.findExportByName(null, "someSwiftFunc"); if (someFunc) { console.log("[+] Found someSwiftFunc: " + someFunc); Interceptor.attach(someFunc, { onEnter: hook, onLeave: function (retval) { console.log("=====================================") } }); } } function hook(args) { console.log("=================Hooked=================") // String is parsed by value let ptr1 = args[0]; let ptr2 = args[1]; let ptr1hex = '0x' + ptr1.toString(16); let ptr2hex = '0x' + ptr2.toString(16); let ptr1value = BigInt(ptr1hex); let ptr2value = BigInt(ptr2hex); let smallObject = ptr2value & 0xFFn; // the last byte // first, try parse smallstring if (isSmallString(smallObject)) { let smallStr = new SDSwiftSmallString(ptr1hex, ptr2hex); console.log(`${smallStr.desc()}`) return } // Large String let largeStr = new SDSwiftLargeString(ptr1value, ptr2value); console.log(`${largeStr.desc()}`) } function isSmallString(value) { let smth = (value >> 4n) & 0xFn; return (smth & 2n) > 0n; } class SDSwiftSmallString { strValue; count; isHex; constructor(h1, h2) { // max small string length is 15 bytes let h1Array = hexStrToUIntArray(h1).reverse(); let h2Array = hexStrToUIntArray(h2).reverse(); function isValidChar(element, index, array) { return (element > 0); } let dataArr = h1Array.concat(h2Array).slice(0, 15); let data = dataArr.filter(isValidChar); let str = String.fromCharCode.apply(null, data); if (isPrintableString(str)) { this.strValue = str; this.count = str.length; this.isHex = false; } else { this.strValue = uintArrayToHexStr(dataArr) this.count = dataArr.length; this.isHex = true; } } desc() { let hexTip = this.isHex ? "hex" : "str"; return ``; } } class SDSwiftLargeString { // https://github.com/TannerJin/Swift-MemoryLayout/blob/master/SwiftCore/String.swift _countAndFlagsBits; _object; isASCII; isNFC; isNativelyStored; isTailAllocated; count; strValue; constructor(inCountAndFlag, inObject) { this._countAndFlagsBits = inCountAndFlag; this._object = inObject; // 1. parse _countAndFlagsBits let abcd = inCountAndFlag >> 48n >> 12n & 0xFn; // 16bits, 2bytes this.isASCII = (abcd & 0x8n) > 0n; this.isNFC = (abcd & 0x4n) > 0n; this.isNativelyStored = (abcd & 0x2n) > 0n; this.isTailAllocated = (abcd & 0x1n) > 0n; this.count = inCountAndFlag & 0xFFFFFFFFFFFFn ; // 48bits,6bytes // 2. parse _object let objectFlag = inObject >> 56n & 0xFFn; let strAddress = '0x' + (inObject & 0xFFFFFFFFFFFFFFn).toString(16); // low 56 bits let strPtr = new NativePointer(strAddress); let cstrPtr = strPtr.add(32); this.strValue = cstrPtr.readCString() ?? ""; } desc() { return ``; } } function isPrintableChar(val) { // [A-Za-z0-9_$ ] //0-9 0x30-0x39 //A-Z 0x41-0x5a //a-z 97-122 //0x5f 0x24 0x20 let isNumber = (val >= 0x30 && val <= 0x39); let isUpper = (val >= 0x41 && val <= 0x5a); let isLower = (val >= 0x61 && val <= 0x7a); let isSpecial = (val == 0x5f) || (val == 0x24) || (val == 0x20); return isNumber || isUpper || isLower || isSpecial; } function isPrintableString(str) { for(var i = 0; i < str.length; i++) { let val = str.charCodeAt(i); if (!isPrintableChar(val)) { return false; } } return true; } function hexString(str) { var ret = "0x"; for(var i = 0; i < str.length; i++) { let val = str.charCodeAt(i); var valstr = val.toString(16); if (valstr.length == 1) { valstr = '0' + valstr; } ret = ret + valstr; } return ret; } function readUCharHexString(ptr, maxlen) { var idx = 0; var hexStr = ""; while (true) { let val = ptr.add(idx).readU8() if (val == 0) { break; } var valstr = val.toString(16); if (valstr.length == 1) { valstr = '0' + valstr; } hexStr += valstr; idx++; if (idx >= maxlen) { break; } } if (hexStr.length > 0) { hexStr = "0x" + hexStr; } return hexStr; } function swapInt16(val) { return ((val & 0xff) << 8) | ((val >> 8) & 0xff); } function swapInt32(val) { return ( ((val & 0xff) << 24) | ((val & 0xff00) << 8) | ((val & 0xff0000) >> 8) | ((val >> 24) & 0xff) ); } function hexStrToUIntArray(inputStr) { var str = inputStr if (str.startsWith('0x')) { str = str.substr(2); } var hex = str.toString(); var result = []; for (var n = 0; n < hex.length; n += 2) { result.push(parseInt(hex.substr(n, 2), 16)); } return result; } function uintArrayToHexStr(array) { var str = ""; for (var n = 0; n < array.length; n += 1) { let val = array[n]; var valstr = array[n].toString(16); if (valstr.length == 1) { valstr = '0' + valstr; } str += valstr; } if (str.length > 0) { str = "0x" + str; } return str; }

Project: SwiftString