1 files changed, 209 insertions, 0 deletions
diff --git a/dom/media/gmp/rlz/GMPDeviceBinding.cpp b/dom/media/gmp/rlz/GMPDeviceBinding.cpp
new file mode 100644
index 000000000..c8aee2bcd
--- /dev/null
+++ b/dom/media/gmp/rlz/GMPDeviceBinding.cpp
@@ -0,0 +1,209 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+* License, v. 2.0. If a copy of the MPL was not distributed with this file,
+* You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "GMPDeviceBinding.h"
+#include "mozilla/Attributes.h"
+#include "prenv.h"
+
+#include <string>
+
+#ifdef XP_WIN
+#include "windows.h"
+#ifdef MOZ_SANDBOX
+#include <intrin.h>
+#include <assert.h>
+#endif
+#endif
+
+#if defined(HASH_NODE_ID_WITH_DEVICE_ID)
+
+// In order to provide EME plugins with a "device binding" capability,
+// in the parent we generate and store some random bytes as salt for every
+// (origin, urlBarOrigin) pair that uses EME. We store these bytes so
+// that every time we revisit the same origin we get the same salt.
+// We send this salt to the child on startup. The child collects some
+// device specific data and munges that with the salt to create the
+// "node id" that we expose to EME plugins. It then overwrites the device
+// specific data, and activates the sandbox.
+
+#include "rlz/lib/machine_id.h"
+#include "rlz/lib/string_utils.h"
+#include "sha256.h"
+
+#ifdef XP_WIN
+#include "windows.h"
+#ifdef MOZ_SANDBOX
+#include <intrin.h>
+#include <assert.h>
+#endif
+#endif
+
+#ifdef XP_MACOSX
+#include <assert.h>
+#ifdef HASH_NODE_ID_WITH_DEVICE_ID
+#include <unistd.h>
+#include <mach/mach.h>
+#include <mach/mach_vm.h>
+#endif
+#endif
+
+#endif // HASH_NODE_ID_WITH_DEVICE_ID
+
+namespace mozilla {
+namespace gmp {
+
+#if defined(XP_WIN) && defined(HASH_NODE_ID_WITH_DEVICE_ID)
+MOZ_NEVER_INLINE
+static bool
+GetStackAfterCurrentFrame(uint8_t** aOutTop, uint8_t** aOutBottom)
+{
+  // "Top" of the free space on the stack is directly after the memory
+  // holding our return address.
+  uint8_t* top = (uint8_t*)_AddressOfReturnAddress();
+
+  // Look down the stack until we find the guard page...
+  MEMORY_BASIC_INFORMATION memInfo = {0};
+  uint8_t* bottom = top;
+  while (1) {
+    if (!VirtualQuery(bottom, &memInfo, sizeof(memInfo))) {
+      return false;
+    }
+    if ((memInfo.Protect & PAGE_GUARD) == PAGE_GUARD) {
+      bottom = (uint8_t*)memInfo.BaseAddress + memInfo.RegionSize;
+#ifdef DEBUG
+      if (!VirtualQuery(bottom, &memInfo, sizeof(memInfo))) {
+        return false;
+      }
+      assert(!(memInfo.Protect & PAGE_GUARD)); // Should have found boundary.
+#endif
+      break;
+    } else if (memInfo.State != MEM_COMMIT ||
+               (memInfo.AllocationProtect & PAGE_READWRITE) != PAGE_READWRITE) {
+      return false;
+    }
+    bottom = (uint8_t*)memInfo.BaseAddress - 1;
+  }
+  *aOutTop = top;
+  *aOutBottom = bottom;
+  return true;
+}
+#endif
+
+#if defined(XP_MACOSX) && defined(HASH_NODE_ID_WITH_DEVICE_ID)
+static mach_vm_address_t
+RegionContainingAddress(mach_vm_address_t aAddress)
+{
+  mach_port_t task;
+  kern_return_t kr = task_for_pid(mach_task_self(), getpid(), &task);
+  if (kr != KERN_SUCCESS) {
+    return 0;
+  }
+
+  mach_vm_address_t address = aAddress;
+  mach_vm_size_t size;
+  vm_region_basic_info_data_64_t info;
+  mach_msg_type_number_t count = VM_REGION_BASIC_INFO_COUNT_64;
+  mach_port_t object_name;
+  kr = mach_vm_region(task, &address, &size, VM_REGION_BASIC_INFO_64,
+                      reinterpret_cast<vm_region_info_t>(&info), &count,
+                      &object_name);
+  if (kr != KERN_SUCCESS || size == 0
+      || address > aAddress || address + size <= aAddress) {
+    // mach_vm_region failed, or couldn't find region at given address.
+    return 0;
+  }
+
+  return address;
+}
+
+MOZ_NEVER_INLINE
+static bool
+GetStackAfterCurrentFrame(uint8_t** aOutTop, uint8_t** aOutBottom)
+{
+  mach_vm_address_t stackFrame =
+    reinterpret_cast<mach_vm_address_t>(__builtin_frame_address(0));
+  *aOutTop = reinterpret_cast<uint8_t*>(stackFrame);
+  // Kernel code shows that stack is always a single region.
+  *aOutBottom = reinterpret_cast<uint8_t*>(RegionContainingAddress(stackFrame));
+  return *aOutBottom && (*aOutBottom < *aOutTop);
+}
+#endif
+
+#ifdef HASH_NODE_ID_WITH_DEVICE_ID
+static void SecureMemset(void* start, uint8_t value, size_t size)
+{
+  // Inline instructions equivalent to RtlSecureZeroMemory().
+  for (size_t i = 0; i < size; ++i) {
+    volatile uint8_t* p = static_cast<volatile uint8_t*>(start) + i;
+    *p = value;
+  }
+}
+#endif
+
+bool
+CalculateGMPDeviceId(char* aOriginSalt,
+                     uint32_t aOriginSaltLen,
+                     std::string& aOutNodeId)
+{
+#ifdef HASH_NODE_ID_WITH_DEVICE_ID
+  if (aOriginSaltLen > 0) {
+    std::vector<uint8_t> deviceId;
+    int volumeId;
+    if (!rlz_lib::GetRawMachineId(&deviceId, &volumeId)) {
+      return false;
+    }
+
+    SHA256Context ctx;
+    SHA256_Begin(&ctx);
+    SHA256_Update(&ctx, (const uint8_t*)aOriginSalt, aOriginSaltLen);
+    SHA256_Update(&ctx, deviceId.data(), deviceId.size());
+    SHA256_Update(&ctx, (const uint8_t*)&volumeId, sizeof(int));
+    uint8_t digest[SHA256_LENGTH] = {0};
+    unsigned int digestLen = 0;
+    SHA256_End(&ctx, digest, &digestLen, SHA256_LENGTH);
+
+    // Overwrite all data involved in calculation as it could potentially
+    // identify the user, so there's no chance a GMP can read it and use
+    // it for identity tracking.
+    SecureMemset(&ctx, 0, sizeof(ctx));
+    SecureMemset(aOriginSalt, 0, aOriginSaltLen);
+    SecureMemset(&volumeId, 0, sizeof(volumeId));
+    SecureMemset(deviceId.data(), '*', deviceId.size());
+    deviceId.clear();
+
+    if (!rlz_lib::BytesToString(digest, SHA256_LENGTH, &aOutNodeId)) {
+      return false;
+    }
+
+    if (!PR_GetEnv("MOZ_GMP_DISABLE_NODE_ID_CLEANUP")) {
+      // We've successfully bound the origin salt to node id.
+      // rlz_lib::GetRawMachineId and/or the system functions it
+      // called could have left user identifiable data on the stack,
+      // so carefully zero the stack down to the guard page.
+      uint8_t* top;
+      uint8_t* bottom;
+      if (!GetStackAfterCurrentFrame(&top, &bottom)) {
+        return false;
+      }
+      assert(top >= bottom);
+      // Inline instructions equivalent to RtlSecureZeroMemory().
+      // We can't just use RtlSecureZeroMemory here directly, as in debug
+      // builds, RtlSecureZeroMemory() can't be inlined, and the stack
+      // memory it uses would get wiped by itself running, causing crashes.
+      for (volatile uint8_t* p = (volatile uint8_t*)bottom; p < top; p++) {
+        *p = 0;
+      }
+    }
+  } else
+#endif
+  {
+    aOutNodeId = std::string(aOriginSalt, aOriginSalt + aOriginSaltLen);
+  }
+  return true;
+}
+
+} // namespace gmp
+} // namespace mozilla