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[CodeHealth] Use span of bytes to read arbitrary data
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This PR touches in different places of the code base where the use of
`reinterpret_cast` was necessary to allow data to be handled in
different format. Span is both safer and more ergonimic. It is
preferrable over `void*`, and particularly we should avoid any type of
casts involving byte values to numeric values, as those can cause
undefined behaviour.

This change additionally refactors `DeviceIdImpl::IsValidMacAddress` to
use `base::MakeFixedFlatSet` for the set of invalid mac addresses we
were searching for, as the search was sequential, and for successful
values it meant visiting every element in the array to check for
comparison. To make sure the binary search works as expected, a test has
been added.
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@cdesouza-chromium
cdesouza-chromium committed Oct 16, 2024
1 parent d67b8d0 commit d0160c0
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Showing 10 changed files with 412 additions and 189 deletions.
11 changes: 11 additions & 0 deletions browser/brave_ads/device_id/BUILD.gn
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Original file line number Diff line number Diff line change
Expand Up @@ -37,3 +37,14 @@ source_set("device_id") {
libs += [ "iphlpapi.lib" ]
}
}

source_set("unit_tests") {
testonly = true
sources = [ "device_id_impl_unittest.cc" ]

deps = [
":device_id",
"//base/test:test_support",
"//testing/gtest",
]
}
299 changes: 175 additions & 124 deletions browser/brave_ads/device_id/device_id_impl.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -5,14 +5,17 @@

#include "brave/browser/brave_ads/device_id/device_id_impl.h"

#include <algorithm>
#include <array>
#include <cstdint>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

#include "base/containers/fixed_flat_set.h"
#include "base/functional/bind.h"
#include "base/ranges/algorithm.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "content/public/browser/browser_thread.h"
Expand All @@ -22,6 +25,170 @@ namespace brave_ads {

namespace {

// A matcher for MAC addresses, to allows us to test against a mask of bytes.
class MacAddressInfoMatcher {
public:
template <typename... Args>
constexpr MacAddressInfoMatcher(Args... args) // NOLINT(runtime/explicit)
: address_{static_cast<uint8_t>(args)...}, size_(sizeof...(args)) {
base::ranges::fill(base::span(address_).split_at(size_).second, 0u);
static_assert(sizeof...(args) <= 6u, "Invalid MAC address size");
}

constexpr MacAddressInfoMatcher(const MacAddressInfoMatcher&) = default;
constexpr MacAddressInfoMatcher& operator=(
const MacAddressInfoMatcher& other) {
base::ranges::copy(other.address_, address_.begin());
size_ = other.size_;
return *this;
}

constexpr base::span<const uint8_t> mask() const {
return base::span(address_).first(size_);
}

private:
// The MAC address mask.
std::array<uint8_t, 6u> address_;

// The size of the partial mask.
size_t size_;
};

// A comparator for MAC addresses, so it can be used with a flat_set.
struct MacAddressInfoComparator {
using is_transparent = void;
constexpr bool operator()(const MacAddressInfoMatcher& a,
const MacAddressInfoMatcher& b) const {
return base::ranges::lexicographical_compare(a.mask(), b.mask());
}
constexpr bool operator()(const MacAddressInfoMatcher& matcher,
base::span<const uint8_t> address) const {
return base::ranges::lexicographical_compare(
matcher.mask(),
address.first(std::min(matcher.mask().size(), address.size())));
}
constexpr bool operator()(base::span<const uint8_t> address,
const MacAddressInfoMatcher& matcher) const {
return base::ranges::lexicographical_compare(
address.first(std::min(matcher.mask().size(), address.size())),
matcher.mask());
}
};

constexpr auto kInvalidMacAddresses =
base::MakeFixedFlatSet<MacAddressInfoMatcher>(
{
// Empty address
{0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
// VMware
{0x00, 0x50, 0x56},
{0x00, 0x05, 0x69},
{0x00, 0x0c, 0x29},
{0x00, 0x1c, 0x14},
// VirtualBox
{0x08, 0x00, 0x27},
// PdaNet
{0x00, 0x26, 0x37, 0xbd, 0x39, 0x42},
// Cisco AnyConnect VPN
{0x00, 0x05, 0x9a, 0x3c, 0x7a, 0x00},
// Marvell sometimes uses this as a dummy address
{0x00, 0x11, 0x22, 0x33, 0x44, 0x55},
// Apple uses this across machines for Bluetooth ethernet adapters.
{0x65, 0x90, 0x07, 0x42, 0xf1},
// Juniper uses this for their Virtual Adapter, the other 4 bytes
// are
// reassigned at every boot. 00-ff-xx is not assigned to anyone.
{0x00, 0xff},
// Generic Bluetooth device
{0x00, 0x15, 0x83, 0x3d, 0x0a, 0x57},
// RAS Async Adapter
{0x20, 0x41, 0x53, 0x59, 0x4e, 0xff},
// T-Mobile Wireless Ethernet
// Qualcomm USB ethernet adapter
{0x00, 0xa0, 0xc6, 0x00, 0x00, 0x00},
// Windows VPN
{0x00, 0x53, 0x45, 0x00, 0x00, 0x00},
// Bluetooth
{0x00, 0x1f, 0x81, 0x00, 0x08, 0x30},
{0x00, 0x1b, 0x10, 0x00, 0x2a, 0xec},
{0x00, 0x15, 0x83, 0x15, 0xa3, 0x10},
{0x00, 0x15, 0x83, 0x07, 0xC6, 0x5A},
{0x00, 0x1f, 0x81, 0x00, 0x02, 0x00},
{0x00, 0x1f, 0x81, 0x00, 0x02, 0xdd},
// Ceton TV tuner
{0x00, 0x22, 0x2c, 0xff, 0xff, 0xff},
// Check Point VPN
{0x54, 0x55, 0x43, 0x44, 0x52, 0x09},
{0x54, 0xEF, 0x14, 0x71, 0xE4, 0x0E},
{0x54, 0xBA, 0xC6, 0xFF, 0x74, 0x10},
// Cisco VPN
{0x00, 0x05, 0x9a, 0x3c, 0x78, 0x00},
// Intel USB cell modem
{0x00, 0x1e, 0x10, 0x1f, 0x00, 0x01},
// Microsoft tethering
{0x80, 0x00, 0x60, 0x0f, 0xe8, 0x00},
// Nortel VPN
{0x44, 0x45, 0x53, 0x54, 0x42, 0x00},
// AEP VPN
{0x00, 0x30, 0x70, 0x00, 0x00, 0x01},
// Positive VPN
{0x00, 0x02, 0x03, 0x04, 0x05, 0x06},
// Bluetooth
{0x00, 0x15, 0x83, 0x0B, 0x13, 0xC0},
// Kerio Virtual Network Adapter
{0x44, 0x45, 0x53, 0x54, 0x4f, 0x53},
// Sierra Wireless cell modems.
{0x00, 0xA0, 0xD5},
// FRITZ!web DSL
{0x00, 0x04, 0x0E, 0xFF, 0xFF, 0xFF},
// VirtualPC
{0x00, 0x00, 0x00, 0x00, 0x00, 0x01},
// Bluetooth
{0x00, 0x1F, 0x81, 0x00, 0x01, 0x00},
{0x00, 0x30, 0x91, 0x10, 0x00, 0x26},
{0x00, 0x25, 0x00, 0x5A, 0xC3, 0xD0},
{0x00, 0x15, 0x83, 0x0C, 0xBF, 0xEB},
// Huawei cell modem
{0x58, 0x2C, 0x80, 0x13, 0x92, 0x63},
// Fortinet VPN
{0x00, 0x09, 0x0F},
// Realtek
{0x00, 0x00, 0x00, 0x00, 0x00, 0x30},
// Other rare dupes.
{0x00, 0x11, 0xf5, 0x0d, 0x8a, 0xe8}, // Atheros
{0x00, 0x20, 0x07, 0x01, 0x16, 0x06}, // Atheros
{0x0d, 0x0b, 0x00, 0x00, 0xe0, 0x00}, // Atheros
{0x90, 0x4c, 0xe5, 0x0b, 0xc8, 0x8e}, // Atheros
{0x00, 0x1c, 0x23, 0x38, 0x49, 0xa4}, // Broadcom
{0x00, 0x12, 0x3f, 0x82, 0x7c, 0x32}, // Broadcom
{0x00, 0x11, 0x11, 0x32, 0xc3, 0x77}, // Broadcom
{0x00, 0x24, 0xd6, 0xae, 0x3e, 0x39}, // Microsoft
{0x00, 0x0f, 0xb0, 0x3a, 0xb4, 0x80}, // Realtek
{0x08, 0x10, 0x74, 0xa1, 0xda, 0x1b}, // Realtek
{0x00, 0x21, 0x9b, 0x2a, 0x0a, 0x9c}, // Realtek
},
MacAddressInfoComparator());

// Ensure that invalid MAC addresses are not submasked. This is important as the
// binary search for the elements could fall past the bunch, if we had
// submasking groups, and then it wouldn't find the actual mask.
constexpr bool HasNoSubmaskingOnInvalidAddresses() {
if constexpr (kInvalidMacAddresses.size() < 2u) {
return true;
}
for (auto it = std::cbegin(kInvalidMacAddresses);
it != std::cend(kInvalidMacAddresses) - 1; ++it) {
auto next = std::next(it)->mask();
if (it->mask() == next.first(std::min(it->mask().size(), next.size()))) {
return false;
}
}
return true;
}
static_assert(HasNoSubmaskingOnInvalidAddresses(),
"Invalid MAC addresses must not be submasked");

std::optional<std::string> ComputeHmacSha256(std::string_view key,
std::string_view text) {
crypto::HMAC hmac(crypto::HMAC::SHA256);
Expand All @@ -46,128 +213,6 @@ void GetRawDeviceIdCallback(DeviceIdCallback callback,
ComputeHmacSha256(raw_device_id, "FOOBAR").value_or(std::string()));
}

bool IsValidMacAddressImpl(const void* bytes, size_t size) {
constexpr size_t kMacLength = 6;

struct MacAddressInfo {
size_t count;
unsigned char address[kMacLength];
};

constexpr size_t kOuiLength = 3;

// VPN, virtualization, tethering, bluetooth, etc.
static constexpr MacAddressInfo kInvalidMacAddresses[] = {
// Empty address
{kMacLength, {0, 0, 0, 0, 0, 0}},
// VMware
{kOuiLength, {0x00, 0x50, 0x56}},
{kOuiLength, {0x00, 0x05, 0x69}},
{kOuiLength, {0x00, 0x0c, 0x29}},
{kOuiLength, {0x00, 0x1c, 0x14}},
// VirtualBox
{kOuiLength, {0x08, 0x00, 0x27}},
// PdaNet
{kMacLength, {0x00, 0x26, 0x37, 0xbd, 0x39, 0x42}},
// Cisco AnyConnect VPN
{kMacLength, {0x00, 0x05, 0x9a, 0x3c, 0x7a, 0x00}},
// Marvell sometimes uses this as a dummy address
{kMacLength, {0x00, 0x11, 0x22, 0x33, 0x44, 0x55}},
// Apple uses this across machines for Bluetooth ethernet adapters.
{kMacLength - 1, {0x65, 0x90, 0x07, 0x42, 0xf1}},
// Juniper uses this for their Virtual Adapter, the other 4 bytes are
// reassigned at every boot. 00-ff-xx is not assigned to anyone.
{2, {0x00, 0xff}},
// T-Mobile Wireless Ethernet
{kMacLength, {0x00, 0xa0, 0xc6, 0x00, 0x00, 0x00}},
// Generic Bluetooth device
{kMacLength, {0x00, 0x15, 0x83, 0x3d, 0x0a, 0x57}},
// RAS Async Adapter
{kMacLength, {0x20, 0x41, 0x53, 0x59, 0x4e, 0xff}},
// Qualcomm USB ethernet adapter
{kMacLength, {0x00, 0xa0, 0xc6, 0x00, 0x00, 0x00}},
// Windows VPN
{kMacLength, {0x00, 0x53, 0x45, 0x00, 0x00, 0x00}},
// Bluetooth
{kMacLength, {0x00, 0x1f, 0x81, 0x00, 0x08, 0x30}},
{kMacLength, {0x00, 0x1b, 0x10, 0x00, 0x2a, 0xec}},
{kMacLength, {0x00, 0x15, 0x83, 0x15, 0xa3, 0x10}},
{kMacLength, {0x00, 0x15, 0x83, 0x07, 0xC6, 0x5A}},
{kMacLength, {0x00, 0x1f, 0x81, 0x00, 0x02, 0x00}},
{kMacLength, {0x00, 0x1f, 0x81, 0x00, 0x02, 0xdd}},
// Ceton TV tuner
{kMacLength, {0x00, 0x22, 0x2c, 0xff, 0xff, 0xff}},
// Check Point VPN
{kMacLength, {0x54, 0x55, 0x43, 0x44, 0x52, 0x09}},
{kMacLength, {0x54, 0xEF, 0x14, 0x71, 0xE4, 0x0E}},
{kMacLength, {0x54, 0xBA, 0xC6, 0xFF, 0x74, 0x10}},
// Cisco VPN
{kMacLength, {0x00, 0x05, 0x9a, 0x3c, 0x7a, 0x00}},
// Cisco VPN
{kMacLength, {0x00, 0x05, 0x9a, 0x3c, 0x78, 0x00}},
// Intel USB cell modem
{kMacLength, {0x00, 0x1e, 0x10, 0x1f, 0x00, 0x01}},
// Microsoft tethering
{kMacLength, {0x80, 0x00, 0x60, 0x0f, 0xe8, 0x00}},
// Nortel VPN
{kMacLength, {0x44, 0x45, 0x53, 0x54, 0x42, 0x00}},
// AEP VPN
{kMacLength, {0x00, 0x30, 0x70, 0x00, 0x00, 0x01}},
// Positive VPN
{kMacLength, {0x00, 0x02, 0x03, 0x04, 0x05, 0x06}},
// Bluetooth
{kMacLength, {0x00, 0x15, 0x83, 0x0B, 0x13, 0xC0}},
// Kerio Virtual Network Adapter
{kMacLength, {0x44, 0x45, 0x53, 0x54, 0x4f, 0x53}},
// Sierra Wireless cell modems.
{kOuiLength, {0x00, 0xA0, 0xD5}},
// FRITZ!web DSL
{kMacLength, {0x00, 0x04, 0x0E, 0xFF, 0xFF, 0xFF}},
// VirtualPC
{kMacLength, {0x00, 0x00, 0x00, 0x00, 0x00, 0x01}},
// Bluetooth
{kMacLength, {0x00, 0x1F, 0x81, 0x00, 0x01, 0x00}},
{kMacLength, {0x00, 0x30, 0x91, 0x10, 0x00, 0x26}},
{kMacLength, {0x00, 0x25, 0x00, 0x5A, 0xC3, 0xD0}},
{kMacLength, {0x00, 0x15, 0x83, 0x0C, 0xBF, 0xEB}},
// Huawei cell modem
{kMacLength, {0x58, 0x2C, 0x80, 0x13, 0x92, 0x63}},
// Fortinet VPN
{kOuiLength, {0x00, 0x09, 0x0F}},
// Realtek
{kMacLength, {0x00, 0x00, 0x00, 0x00, 0x00, 0x30}},
// Other rare dupes.
{kMacLength, {0x00, 0x11, 0xf5, 0x0d, 0x8a, 0xe8}}, // Atheros
{kMacLength, {0x00, 0x20, 0x07, 0x01, 0x16, 0x06}}, // Atheros
{kMacLength, {0x0d, 0x0b, 0x00, 0x00, 0xe0, 0x00}}, // Atheros
{kMacLength, {0x90, 0x4c, 0xe5, 0x0b, 0xc8, 0x8e}}, // Atheros
{kMacLength, {0x00, 0x1c, 0x23, 0x38, 0x49, 0xa4}}, // Broadcom
{kMacLength, {0x00, 0x12, 0x3f, 0x82, 0x7c, 0x32}}, // Broadcom
{kMacLength, {0x00, 0x11, 0x11, 0x32, 0xc3, 0x77}}, // Broadcom
{kMacLength, {0x00, 0x24, 0xd6, 0xae, 0x3e, 0x39}}, // Microsoft
{kMacLength, {0x00, 0x0f, 0xb0, 0x3a, 0xb4, 0x80}}, // Realtek
{kMacLength, {0x08, 0x10, 0x74, 0xa1, 0xda, 0x1b}}, // Realtek
{kMacLength, {0x00, 0x21, 0x9b, 0x2a, 0x0a, 0x9c}}, // Realtek
};

if (size != kMacLength) {
return false;
}

if (static_cast<const unsigned char*>(bytes)[0] & 0x02) {
// Locally administered.
return false;
}

for (const auto& mac_address : kInvalidMacAddresses) {
if (memcmp(mac_address.address, bytes, mac_address.count) == 0) {
return false;
}
}

return true;
}

} // namespace

void DeviceIdImpl::GetDeviceId(DeviceIdCallback callback) {
Expand All @@ -179,8 +224,14 @@ void DeviceIdImpl::GetDeviceId(DeviceIdCallback callback) {
}

// static
bool DeviceIdImpl::IsValidMacAddress(const void* bytes, size_t size) {
return IsValidMacAddressImpl(bytes, size);
bool DeviceIdImpl::IsValidMacAddress(base::span<const uint8_t> bytes) {
constexpr size_t kMacLength = 6;
if (bytes.size() != kMacLength || bytes.front() & 0x02) {
// Locally administered.
return false;
}

return kInvalidMacAddresses.find(bytes) == kInvalidMacAddresses.end();
}

} // namespace brave_ads
11 changes: 6 additions & 5 deletions browser/brave_ads/device_id/device_id_impl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
#ifndef BRAVE_BROWSER_BRAVE_ADS_DEVICE_ID_DEVICE_ID_IMPL_H_
#define BRAVE_BROWSER_BRAVE_ADS_DEVICE_ID_DEVICE_ID_IMPL_H_

#include "base/containers/span.h"
#include "brave/components/brave_ads/browser/device_id/device_id.h"

namespace brave_ads {
Expand All @@ -14,15 +15,15 @@ class DeviceIdImpl : public DeviceId {
public:
void GetDeviceId(DeviceIdCallback callback) override;

private:
// Platform specific implementation of "raw" device id retrieval.
static void GetRawDeviceId(DeviceIdCallback callback);

// On some platforms, part of the machine ID is the MAC address. This function
// is shared across platforms to filter out MAC addresses that have been
// identified as invalid, i.e. not unique. For example, some VM hosts assign a
// new MAC address at each reboot.
static bool IsValidMacAddress(const void* bytes, size_t size);
static bool IsValidMacAddress(base::span<const uint8_t> bytes);

private:
// Platform specific implementation of "raw" device id retrieval.
static void GetRawDeviceId(DeviceIdCallback callback);
};

} // namespace brave_ads
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