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/* 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 <windows.h>
#include <wtsapi32.h>
#include "uachelper.h"
#include "updatecommon.h"
// See the MSDN documentation with title: Privilege Constants
// At the time of this writing, this documentation is located at:
// http://msdn.microsoft.com/en-us/library/windows/desktop/bb530716%28v=vs.85%29.aspx
LPCTSTR UACHelper::PrivsToDisable[] = {
SE_ASSIGNPRIMARYTOKEN_NAME, SE_AUDIT_NAME, SE_BACKUP_NAME,
// CreateProcess will succeed but the app will fail to launch on some WinXP
// machines if SE_CHANGE_NOTIFY_NAME is disabled. In particular this
// happens for limited user accounts on those machines. The define is kept
// here as a reminder that it should never be re-added. This permission is
// for directory watching but also from MSDN: "This privilege also causes
// the system to skip all traversal access checks." SE_CHANGE_NOTIFY_NAME,
SE_CREATE_GLOBAL_NAME, SE_CREATE_PAGEFILE_NAME, SE_CREATE_PERMANENT_NAME,
SE_CREATE_SYMBOLIC_LINK_NAME, SE_CREATE_TOKEN_NAME, SE_DEBUG_NAME,
SE_ENABLE_DELEGATION_NAME, SE_IMPERSONATE_NAME, SE_INC_BASE_PRIORITY_NAME,
SE_INCREASE_QUOTA_NAME, SE_INC_WORKING_SET_NAME, SE_LOAD_DRIVER_NAME,
SE_LOCK_MEMORY_NAME, SE_MACHINE_ACCOUNT_NAME, SE_MANAGE_VOLUME_NAME,
SE_PROF_SINGLE_PROCESS_NAME, SE_RELABEL_NAME, SE_REMOTE_SHUTDOWN_NAME,
SE_RESTORE_NAME, SE_SECURITY_NAME, SE_SHUTDOWN_NAME, SE_SYNC_AGENT_NAME,
SE_SYSTEM_ENVIRONMENT_NAME, SE_SYSTEM_PROFILE_NAME, SE_SYSTEMTIME_NAME,
SE_TAKE_OWNERSHIP_NAME, SE_TCB_NAME, SE_TIME_ZONE_NAME,
SE_TRUSTED_CREDMAN_ACCESS_NAME, SE_UNDOCK_NAME, SE_UNSOLICITED_INPUT_NAME};
/**
* Opens a user token for the given session ID
*
* @param sessionID The session ID for the token to obtain
* @return A handle to the token to obtain which will be primary if enough
* permissions exist. Caller should close the handle.
*/
HANDLE
UACHelper::OpenUserToken(DWORD sessionID) {
HMODULE module = LoadLibraryW(L"wtsapi32.dll");
HANDLE token = nullptr;
decltype(WTSQueryUserToken)* wtsQueryUserToken =
(decltype(WTSQueryUserToken)*)GetProcAddress(module, "WTSQueryUserToken");
if (wtsQueryUserToken) {
wtsQueryUserToken(sessionID, &token);
}
FreeLibrary(module);
return token;
}
/**
* Opens a linked token for the specified token.
*
* @param token The token to get the linked token from
* @return A linked token or nullptr if one does not exist.
* Caller should close the handle.
*/
HANDLE
UACHelper::OpenLinkedToken(HANDLE token) {
// Magic below...
// UAC creates 2 tokens. One is the restricted token which we have.
// the other is the UAC elevated one. Since we are running as a service
// as the system account we have access to both.
TOKEN_LINKED_TOKEN tlt;
HANDLE hNewLinkedToken = nullptr;
DWORD len;
if (GetTokenInformation(token, (TOKEN_INFORMATION_CLASS)TokenLinkedToken,
&tlt, sizeof(TOKEN_LINKED_TOKEN), &len)) {
token = tlt.LinkedToken;
hNewLinkedToken = token;
}
return hNewLinkedToken;
}
/**
* Enables or disables a privilege for the specified token.
*
* @param token The token to adjust the privilege on.
* @param priv The privilege to adjust.
* @param enable Whether to enable or disable it
* @return TRUE if the token was adjusted to the specified value.
*/
BOOL UACHelper::SetPrivilege(HANDLE token, LPCTSTR priv, BOOL enable) {
LUID luidOfPriv;
if (!LookupPrivilegeValue(nullptr, priv, &luidOfPriv)) {
return FALSE;
}
TOKEN_PRIVILEGES tokenPriv;
tokenPriv.PrivilegeCount = 1;
tokenPriv.Privileges[0].Luid = luidOfPriv;
tokenPriv.Privileges[0].Attributes = enable ? SE_PRIVILEGE_ENABLED : 0;
SetLastError(ERROR_SUCCESS);
if (!AdjustTokenPrivileges(token, false, &tokenPriv, sizeof(tokenPriv),
nullptr, nullptr)) {
return FALSE;
}
return GetLastError() == ERROR_SUCCESS;
}
/**
* For each privilege that is specified, an attempt will be made to
* drop the privilege.
*
* @param token The token to adjust the privilege on.
* Pass nullptr for current token.
* @param unneededPrivs An array of unneeded privileges.
* @param count The size of the array
* @return TRUE if there were no errors
*/
BOOL UACHelper::DisableUnneededPrivileges(HANDLE token, LPCTSTR* unneededPrivs,
size_t count) {
HANDLE obtainedToken = nullptr;
if (!token) {
// Note: This handle is a pseudo-handle and need not be closed
HANDLE process = GetCurrentProcess();
if (!OpenProcessToken(process, TOKEN_ALL_ACCESS_P, &obtainedToken)) {
LOG_WARN(
("Could not obtain token for current process, no "
"privileges changed. (%lu)",
GetLastError()));
return FALSE;
}
token = obtainedToken;
}
BOOL result = TRUE;
for (size_t i = 0; i < count; i++) {
if (SetPrivilege(token, unneededPrivs[i], FALSE)) {
LOG(("Disabled unneeded token privilege: %s.", unneededPrivs[i]));
} else {
LOG(("Could not disable token privilege value: %s. (%lu)",
unneededPrivs[i], GetLastError()));
result = FALSE;
}
}
if (obtainedToken) {
CloseHandle(obtainedToken);
}
return result;
}
/**
* Disables privileges for the specified token.
* The privileges to disable are in PrivsToDisable.
* In the future there could be new privs and we are not sure if we should
* explicitly disable these or not.
*
* @param token The token to drop the privilege on.
* Pass nullptr for current token.
* @return TRUE if there were no errors
*/
BOOL UACHelper::DisablePrivileges(HANDLE token) {
static const size_t PrivsToDisableSize =
sizeof(UACHelper::PrivsToDisable) / sizeof(UACHelper::PrivsToDisable[0]);
return DisableUnneededPrivileges(token, UACHelper::PrivsToDisable,
PrivsToDisableSize);
}
/**
* Check if the current user can elevate.
*
* @return true if the user can elevate.
* false otherwise.
*/
bool UACHelper::CanUserElevate() {
HANDLE token;
if (!OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &token)) {
return false;
}
TOKEN_ELEVATION_TYPE elevationType;
DWORD len;
bool canElevate =
GetTokenInformation(token, TokenElevationType, &elevationType,
sizeof(elevationType), &len) &&
(elevationType == TokenElevationTypeLimited);
CloseHandle(token);
return canElevate;
}
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