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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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"
#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"
#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
#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
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