Microsoft KB Archive/165194

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INFO: CreateProcessAsUser Windowstations and Desktops

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Q165194

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The information in this article applies to:


 * Microsoft Win32 Application Programming Interface (API), used with:
 * Microsoft Windows NT Server versions 3.51, 4.0
 * Microsoft Windows NT Workstation versions 3.51, 4.0
 * the operating system: Microsoft Windows 2000

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SUMMARY
When a process is started by means of the CreateProcessAsUser function, the process will be launched into a windowstation and desktop combination based on the value of lpDesktop in the STARTUPINFO structure parameter. If a windowstation and desktop combination is specified in the lpDesktop member, the system will attempt to launch the process into that windowstation and desktop. If the lpDesktop member is initialized to NULL, the system will attempt to use the same windowstation and desktop as the calling process if the system is associated with the interactive windowstation. If the lpDesktop member is not initialized to NULL, the system will create a new invisible windowstation and desktop. If the system is initialized with the empty string, "", it will either create a new invisible windowstation and desktop, or if one has been created by means of a prior call by using the same access token, the existing windowstation and desktop will be used.

MORE INFORMATION
Sometimes the launched process may fail to start, and one of the following error messages may appear:

Initialization of the dynamic library \system32\user32.dll failed. The process is terminating abnormally.

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Initialization of the dynamic library \system32\kernel32.dll failed. The process is terminating abnormally.

The error message occurs when the process that is started causes the initialization code in either the User32.dll or the Kernel32.dll file to fail due to an API call from the launched process that does not have proper security access to either the targeted windowstation or desktop. For example, if the process that was started was attempting to create a window, the process would be required to have DESKTOP_CREATEWINDOW access to the desktop object. If the process has not been granted this access right, an error would occur in the User32.dll file, which would cause the system error box to appear and the process would fail to start.

The best method to resolve this error is to grant the user full access to both the targeted windowstation and desktop.

For example, if you want the process launched by the CreateProcessAsUser function to be interactive, the following windowstation and desktop combination should be specified:

"winsta0\default" The following sample code grants the user named franki access to the interactive windowstation and desktop, "winsta0\\default". Access is granted based on the logon security ID (SID) of the user franki.

For more information on windowstations and desktops, please refer to the Win32 SDK documentation.

Sample Code
The following sample code gives the user named "franki" full access to the interactive windowstation and desktop, "winsta0\\default". The access control entry (ACE) for each object is based on franki's logon SID. The code launches the Cmd.exe file.

NOTE: An application that launches many processes such as a scheduler service may want to remove the new ACE after the process has completed because the ACEs accumulate on the DACL of both the windowstation and desktop object.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

"Q185292 PRB: SetUserObjectSecurity Returns ERROR_NOT_ENOUGH_QUOTA"   #define RTN_OK     0 #define RTN_ERROR 13

#define WINSTA_ALL (WINSTA_ACCESSCLIPBOARD | WINSTA_ACCESSGLOBALATOMS |   WINSTA_CREATEDESKTOP    | WINSTA_ENUMDESKTOPS      |   WINSTA_ENUMERATE        | WINSTA_EXITWINDOWS       |   WINSTA_READATTRIBUTES   | WINSTA_READSCREEN        |   WINSTA_WRITEATTRIBUTES  | DELETE                   |   READ_CONTROL            | WRITE_DAC                |   WRITE_OWNER)

#define DESKTOP_ALL (DESKTOP_CREATEMENU     | DESKTOP_CREATEWINDOW  |   DESKTOP_ENUMERATE       | DESKTOP_HOOKCONTROL   |   DESKTOP_JOURNALPLAYBACK | DESKTOP_JOURNALRECORD |   DESKTOP_READOBJECTS     | DESKTOP_SWITCHDESKTOP |   DESKTOP_WRITEOBJECTS    | DELETE                |   READ_CONTROL            | WRITE_DAC             |   WRITE_OWNER)

#define GENERIC_ACCESS (GENERIC_READ   | GENERIC_WRITE |   GENERIC_EXECUTE | GENERIC_ALL)

#include   #include 

BOOL ObtainSid(

HANDLE hToken,          // Handle to an process access token. PSID  *psid             // ptr to the buffer of the logon sid );

void RemoveSid(       PSID *psid               // ptr to the buffer of the logon sid        );

BOOL AddTheAceWindowStation(

HWINSTA hwinsta,        // handle to a windowstation PSID   psid             // logon sid of the process );

BOOL AddTheAceDesktop(

HDESK hdesk,            // handle to a desktop PSID psid               // logon sid of the process );

int main(void) {       HANDLE              hToken; HDESK              hdesk; HWINSTA            hwinsta; PROCESS_INFORMATION pi; PSID               psid; STARTUPINFO        si;

//        // obtain an access token for the user fester //        if (!LogonUser( "franki", NULL, "franki", LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, &hToken ))            return RTN_ERROR;

//        // obtain a handle to the interactive windowstation //        hwinsta = OpenWindowStation(             "winsta0",             FALSE,             READ_CONTROL | WRITE_DAC             ); if (hwinsta == NULL) return RTN_ERROR;

HWINSTA hwinstaold = GetProcessWindowStation;

//        // set the windowstation to winsta0 so that you obtain the // correct default desktop //        if (!SetProcessWindowStation(hwinsta)) return RTN_ERROR;

//        // obtain a handle to the "default" desktop //        hdesk = OpenDesktop(             "default",             0,             FALSE,             READ_CONTROL | WRITE_DAC |             DESKTOP_WRITEOBJECTS | DESKTOP_READOBJECTS             ); if (hdesk == NULL) return RTN_ERROR;

//        // obtain the logon sid of the user fester //        if (!ObtainSid(hToken, &psid)) return RTN_ERROR;

//        // add the user to interactive windowstation //        if (!AddTheAceWindowStation(hwinsta, psid)) return RTN_ERROR;

//        // add user to "default" desktop //        if (!AddTheAceDesktop(hdesk, psid)) return RTN_ERROR;

//        // free the buffer for the logon sid //        RemoveSid(&psid);

//        // close the handles to the interactive windowstation and desktop //        CloseWindowStation(hwinsta);

CloseDesktop(hdesk);

//        // initialize STARTUPINFO structure //        ZeroMemory(&si, sizeof(STARTUPINFO)); si.cb       = sizeof(STARTUPINFO); si.lpDesktop = "winsta0\\default";

//        // launch the process //        if (!CreateProcessAsUser( hToken, NULL, "cmd.exe", NULL, NULL, FALSE, NORMAL_PRIORITY_CLASS | CREATE_NEW_CONSOLE, NULL, NULL, &si, &pi ))            return RTN_ERROR;

SetProcessWindowStation(hwinstaold); //set it back

//        // close the handles //        CloseHandle(pi.hProcess);

CloseHandle(pi.hThread);

return RTN_OK; }

BOOL ObtainSid(HANDLE hToken, PSID *psid)

{       BOOL                    bSuccess = FALSE; // assume function will // fail DWORD                  dwIndex; DWORD                  dwLength = 0; TOKEN_INFORMATION_CLASS tic     = TokenGroups; PTOKEN_GROUPS          ptg      = NULL;

__try {            //              // determine the size of the buffer //             if (!GetTokenInformation( hToken, tic, (LPVOID)ptg, 0,            &dwLength ))                 {                  if (GetLastError == ERROR_INSUFFICIENT_BUFFER) {                      ptg = (PTOKEN_GROUPS)HeapAlloc(                            GetProcessHeap,                  HEAP_ZERO_MEMORY,                  dwLength                  ); if (ptg == NULL) __leave; }                  else __leave; }

//             // obtain the groups the access token belongs to             // if (!GetTokenInformation( hToken, tic, (LPVOID)ptg, dwLength, &dwLength ))                 __leave;

//             // determine which group is the logon sid //             for (dwIndex = 0; dwIndex < ptg->GroupCount; dwIndex++) {            if ((ptg->Groups[dwIndex].Attributes & SE_GROUP_LOGON_ID)                  ==  SE_GROUP_LOGON_ID) {                      //                        // determine the length of the sid //                       dwLength = GetLengthSid(ptg->Groups[dwIndex].Sid);

//                       // allocate a buffer for the logon sid //                       *psid = (PSID)HeapAlloc(                            GetProcessHeap,                  HEAP_ZERO_MEMORY,                  dwLength                  ); if (*psid == NULL) __leave;

//                  // obtain a copy of the logon sid //                  if (!CopySid(dwLength, *psid, ptg->Groups[dwIndex].Sid)) __leave;

//                  // break out of the loop since the logon sid has been // found //                  break; }            }

//             // indicate success //             bSuccess = TRUE; }       __finally {            //         // free the buffer for the token group //             if (ptg != NULL) HeapFree(GetProcessHeap, 0, (LPVOID)ptg); }

return bSuccess;

}

void RemoveSid(PSID *psid) {       HeapFree(GetProcessHeap, 0, (LPVOID)*psid); }

BOOL AddTheAceWindowStation(HWINSTA hwinsta, PSID psid) {

ACCESS_ALLOWED_ACE  *pace; ACL_SIZE_INFORMATION aclSizeInfo; BOOL                bDaclExist; BOOL                bDaclPresent; BOOL                bSuccess  = FALSE; // assume function will //fail DWORD               dwNewAclSize; DWORD               dwSidSize = 0; DWORD               dwSdSizeNeeded; PACL                pacl; PACL                pNewAcl; PSECURITY_DESCRIPTOR psd      = NULL; PSECURITY_DESCRIPTOR psdNew   = NULL; PVOID               pTempAce; SECURITY_INFORMATION si       = DACL_SECURITY_INFORMATION; unsigned int        i;

__try {            //              // obtain the dacl for the windowstation //             if (!GetUserObjectSecurity( hwinsta, &si, psd, dwSidSize, &dwSdSizeNeeded ))            if (GetLastError == ERROR_INSUFFICIENT_BUFFER) {                 psd = (PSECURITY_DESCRIPTOR)HeapAlloc(                       GetProcessHeap,                       HEAP_ZERO_MEMORY,                       dwSdSizeNeeded             ); if (psd == NULL) __leave;

psdNew = (PSECURITY_DESCRIPTOR)HeapAlloc(                      GetProcessHeap,                       HEAP_ZERO_MEMORY,                       dwSdSizeNeeded                       ); if (psdNew == NULL) __leave;

dwSidSize = dwSdSizeNeeded;

if (!GetUserObjectSecurity( hwinsta, &si, psd, dwSidSize, &dwSdSizeNeeded ))                      __leave; }            else __leave;

//             // create a new dacl //             if (!InitializeSecurityDescriptor( psdNew, SECURITY_DESCRIPTOR_REVISION ))                 __leave;

//        // get dacl from the security descriptor //             if (!GetSecurityDescriptorDacl( psd, &bDaclPresent, &pacl, &bDaclExist ))                 __leave;

//             // initialize //             ZeroMemory(&aclSizeInfo, sizeof(ACL_SIZE_INFORMATION)); aclSizeInfo.AclBytesInUse = sizeof(ACL);

//             // call only if the dacl is not NULL //             if (pacl != NULL) {                 // get the file ACL size info if (!GetAclInformation( pacl, (LPVOID)&aclSizeInfo, sizeof(ACL_SIZE_INFORMATION), AclSizeInformation ))                      __leave; }

//             // compute the size of the new acl //             dwNewAclSize = aclSizeInfo.AclBytesInUse + (2 *             sizeof(ACCESS_ALLOWED_ACE)) + (2 * GetLengthSid(psid)) - (2 *             sizeof(DWORD));

//             // allocate memory for the new acl //             pNewAcl = (PACL)HeapAlloc(                  GetProcessHeap,                  HEAP_ZERO_MEMORY,                  dwNewAclSize                  ); if (pNewAcl == NULL) __leave;

//             // initialize the new dacl //             if (!InitializeAcl(pNewAcl, dwNewAclSize, ACL_REVISION)) __leave;

//             // if DACL is present, copy it to a new DACL //             if (bDaclPresent) // only copy if DACL was present {                 // copy the ACEs to our new ACL if (aclSizeInfo.AceCount) {                      for (i=0; i < aclSizeInfo.AceCount; i++) {                           // get an ACE if (!GetAce(pacl, i, &pTempAce)) __leave;

// add the ACE to the new ACL if (!AddAce( pNewAcl, ACL_REVISION, MAXDWORD, pTempAce, ((PACE_HEADER)pTempAce)->AceSize ))                                __leave; }                       }                  }

//             // add the first ACE to the windowstation //             pace = (ACCESS_ALLOWED_ACE *)HeapAlloc(                  GetProcessHeap,                  HEAP_ZERO_MEMORY,             sizeof(ACCESS_ALLOWED_ACE) + GetLengthSid(psid) -                  sizeof(DWORD ));            if (pace == NULL) __leave;

pace->Header.AceType = ACCESS_ALLOWED_ACE_TYPE; pace->Header.AceFlags = CONTAINER_INHERIT_ACE | INHERIT_ONLY_ACE     |

OBJECT_INHERIT_ACE; pace->Header.AceSize = sizeof(ACCESS_ALLOWED_ACE) +

GetLengthSid(psid) - sizeof(DWORD); pace->Mask           = GENERIC_ACCESS;

if (!CopySid(GetLengthSid(psid), &pace->SidStart, psid)) __leave;

if (!AddAce( pNewAcl, ACL_REVISION, MAXDWORD, (LPVOID)pace, pace->Header.AceSize ))                 __leave;

//             // add the second ACE to the windowstation //             pace->Header.AceFlags = NO_PROPAGATE_INHERIT_ACE; pace->Mask           = WINSTA_ALL;

if (!AddAce( pNewAcl, ACL_REVISION, MAXDWORD, (LPVOID)pace, pace->Header.AceSize ))                 __leave;

//                  // set new dacl for the security descriptor //                  if (!SetSecurityDescriptorDacl( psdNew, TRUE, pNewAcl, FALSE ))                      __leave;

//         // set the new security descriptor for the windowstation //         if (!SetUserObjectSecurity(hwinsta, &si, psdNew)) __leave;

//         // indicate success //         bSuccess = TRUE; }       __finally {            //              // free the allocated buffers //             if (pace != NULL) HeapFree(GetProcessHeap, 0, (LPVOID)pace);

if (pNewAcl != NULL) HeapFree(GetProcessHeap, 0, (LPVOID)pNewAcl);

if (psd != NULL) HeapFree(GetProcessHeap, 0, (LPVOID)psd);

if (psdNew != NULL) HeapFree(GetProcessHeap, 0, (LPVOID)psdNew); }

return bSuccess;

}

BOOL AddTheAceDesktop(HDESK hdesk, PSID psid) {

ACL_SIZE_INFORMATION aclSizeInfo; BOOL                bDaclExist; BOOL                bDaclPresent; BOOL                bSuccess  = FALSE; // assume function will // fail DWORD               dwNewAclSize; DWORD               dwSidSize = 0; DWORD               dwSdSizeNeeded; PACL                pacl; PACL                pNewAcl; PSECURITY_DESCRIPTOR psd      = NULL; PSECURITY_DESCRIPTOR psdNew   = NULL; PVOID               pTempAce; SECURITY_INFORMATION si       = DACL_SECURITY_INFORMATION; unsigned int        i;

__try {            //              // obtain the security descriptor for the desktop object //             if (!GetUserObjectSecurity( hdesk, &si, psd, dwSidSize, &dwSdSizeNeeded ))                 {                  if (GetLastError == ERROR_INSUFFICIENT_BUFFER) {                      psd = (PSECURITY_DESCRIPTOR)HeapAlloc(                            GetProcessHeap,                            HEAP_ZERO_MEMORY,             dwSdSizeNeeded             ); if (psd == NULL) __leave;

psdNew = (PSECURITY_DESCRIPTOR)HeapAlloc(                           GetProcessHeap,                            HEAP_ZERO_MEMORY,                            dwSdSizeNeeded             ); if (psdNew == NULL) __leave;

dwSidSize = dwSdSizeNeeded;

if (!GetUserObjectSecurity( hdesk, &si, psd, dwSidSize, &dwSdSizeNeeded ))                           __leave; }                 else __leave; }

//             // create a new security descriptor //             if (!InitializeSecurityDescriptor( psdNew, SECURITY_DESCRIPTOR_REVISION ))              _   _leave;

//             // obtain the dacl from the security descriptor //             if (!GetSecurityDescriptorDacl( psd, &bDaclPresent, &pacl, &bDaclExist ))                 __leave;

//             // initialize //             ZeroMemory(&aclSizeInfo, sizeof(ACL_SIZE_INFORMATION)); aclSizeInfo.AclBytesInUse = sizeof(ACL);

//             // call only if NULL dacl //             if (pacl != NULL) {                 //                   // determine the size of the ACL info //                  if (!GetAclInformation( pacl, (LPVOID)&aclSizeInfo, sizeof(ACL_SIZE_INFORMATION), AclSizeInformation ))                      __leave; }

//             // compute the size of the new acl //        dwNewAclSize = aclSizeInfo.AclBytesInUse + sizeof(ACCESS_ALLOWED_ACE) + GetLengthSid(psid) - sizeof(DWORD);

//             // allocate buffer for the new acl //             pNewAcl = (PACL)HeapAlloc(                  GetProcessHeap,                  HEAP_ZERO_MEMORY,                  dwNewAclSize                  ); if (pNewAcl == NULL) __leave;

//             // initialize the new acl //             if (!InitializeAcl(pNewAcl, dwNewAclSize, ACL_REVISION)) __leave;

//             // if DACL is present, copy it to a new DACL //             if (bDaclPresent) // only copy if DACL was present {                 // copy the ACEs to our new ACL if (aclSizeInfo.AceCount) {                      for (i=0; i < aclSizeInfo.AceCount; i++) {                           // get an ACE if (!GetAce(pacl, i, &pTempAce)) __leave;

// add the ACE to the new ACL if (!AddAce( pNewAcl, ACL_REVISION, MAXDWORD, pTempAce, ((PACE_HEADER)pTempAce)->AceSize ))                                __leave; }                       }                  }

//             // add ace to the dacl //             if (!AddAccessAllowedAce( pNewAcl, ACL_REVISION, DESKTOP_ALL, psid ))                 __leave;

//             // set new dacl to the new security descriptor //             if (!SetSecurityDescriptorDacl( psdNew, TRUE, pNewAcl, FALSE ))                 __leave;

//             // set the new security descriptor for the desktop object //             if (!SetUserObjectSecurity(hdesk, &si, psdNew)) __leave;

//             // indicate success //             bSuccess = TRUE; }       __finally {           //             // free buffers //            if (pNewAcl != NULL) HeapFree(GetProcessHeap, 0, (LPVOID)pNewAcl);

if (psd != NULL) HeapFree(GetProcessHeap, 0, (LPVOID)psd);

if (psdNew != NULL) HeapFree(GetProcessHeap, 0, (LPVOID)psdNew); }

return bSuccess; } Additional query words:

Keywords : _IK kberrmsg kbAPI kbKernBase kbOSWin2000 kbSecurity kbThread kbFAQ kbDSupport kbGrpDSKernBase

Issue type : kbinfo

Technology : kbAudDeveloper kbWin32sSearch kbWin32API