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// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/win/security_util.h"
#include <windows.h>
#include <winternl.h>
#include <optional>
#include "base/check.h"
#include "base/containers/to_vector.h"
#include "base/files/file_path.h"
#include "base/logging.h"
#include "base/threading/scoped_blocking_call.h"
#include "base/win/access_control_list.h"
#include "base/win/scoped_handle.h"
#include "base/win/security_descriptor.h"
namespace base {
namespace win {
namespace {
bool AddACEToPath(const FilePath& path,
const std::vector<Sid>& sids,
DWORD access_mask,
DWORD inheritance,
bool recursive,
SecurityAccessMode access_mode) {
DCHECK(!path.empty());
if (sids.empty()) {
return true;
}
base::ScopedBlockingCall scoped_blocking_call(FROM_HERE,
base::BlockingType::MAY_BLOCK);
std::optional<SecurityDescriptor> sd =
SecurityDescriptor::FromFile(path, DACL_SECURITY_INFORMATION);
if (!sd) {
return false;
}
std::vector<ExplicitAccessEntry> entries;
for (const Sid& sid : sids) {
entries.emplace_back(sid, access_mode, access_mask, inheritance);
}
if (!sd->SetDaclEntries(entries)) {
return false;
}
if (recursive) {
return sd->WriteToFile(path, DACL_SECURITY_INFORMATION);
}
ScopedHandle handle(::CreateFile(path.value().c_str(), WRITE_DAC, 0, nullptr,
OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS,
nullptr));
if (!handle.is_valid()) {
DPLOG(ERROR) << "Failed opening path \"" << path.value()
<< "\" to write DACL";
return false;
}
return sd->WriteToHandle(handle.get(), SecurityObjectType::kKernel,
DACL_SECURITY_INFORMATION);
}
} // namespace
bool GrantAccessToPath(const FilePath& path,
const std::vector<Sid>& sids,
DWORD access_mask,
DWORD inheritance,
bool recursive) {
return AddACEToPath(path, sids, access_mask, inheritance, recursive,
SecurityAccessMode::kGrant);
}
bool DenyAccessToPath(const FilePath& path,
const std::vector<Sid>& sids,
DWORD access_mask,
DWORD inheritance,
bool recursive) {
return AddACEToPath(path, sids, access_mask, inheritance, recursive,
SecurityAccessMode::kDeny);
}
bool HasAccessToPath(const FilePath& path,
const std::vector<Sid>& sids,
DWORD access_mask,
DWORD inheritance) {
DCHECK(!path.empty());
if (sids.empty()) {
return true;
}
base::ScopedBlockingCall scoped_blocking_call(FROM_HERE,
base::BlockingType::MAY_BLOCK);
std::optional<SecurityDescriptor> sd =
SecurityDescriptor::FromFile(path, DACL_SECURITY_INFORMATION);
if (!sd || !sd->dacl()) {
return false;
}
if (sd->dacl()->is_null()) {
// If the DACL is null, access is allowed.
return true;
}
PACL pacl = sd->dacl()->get();
// Verify that each SID has the specified access.
// Note that this does not check for the presence of a deny ACE.
for (const Sid& sid : sids) {
bool sid_found = false;
for (DWORD ace_index = 0; ace_index < pacl->AceCount; ++ace_index) {
PACCESS_ALLOWED_ACE ace = nullptr;
if (::GetAce(pacl, ace_index, reinterpret_cast<LPVOID*>(&ace)) &&
ace->Header.AceType == ACCESS_ALLOWED_ACE_TYPE &&
(ace->Header.AceFlags & inheritance) == inheritance &&
(ace->Mask & access_mask) == access_mask &&
sid.Equal(&ace->SidStart)) {
sid_found = true;
break;
}
}
if (!sid_found) {
return false;
}
}
return true;
}
std::vector<Sid> CloneSidVector(const std::vector<Sid>& sids) {
return base::ToVector(sids, &Sid::Clone);
}
void AppendSidVector(std::vector<Sid>& base_sids,
const std::vector<Sid>& append_sids) {
for (const Sid& sid : append_sids) {
base_sids.push_back(sid.Clone());
}
}
std::optional<ACCESS_MASK> GetGrantedAccess(HANDLE handle) {
PUBLIC_OBJECT_BASIC_INFORMATION basic_info = {};
if (!NT_SUCCESS(::NtQueryObject(handle, ObjectBasicInformation, &basic_info,
sizeof(basic_info), nullptr))) {
return std::nullopt;
}
return basic_info.GrantedAccess;
}
} // namespace win
} // namespace base
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