INFO: CreateProcessAsUser, Windowstations and DesktopsLast reviewed: July 3, 1997Article ID: Q165194 |
The information in this article applies to:
SUMMARYWhen a process is launched via the CreateProcessAsUser API, 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 it is initialized with the empty string, "", the system will either create a new invisible windowstation and desktop or if one has been created via a prior call using the same access token, the existing windowstation and desktop will be used.
MORE INFORMATIONSometimes the launched process may fail to start and one of the following error messages appears:
Initialization of the dynamic library <system>\system32\user32.dll failed. The process is terminating abnormally.- or –
Initialization of the dynamic library <system>\system32\kernel32.dll failed. The process is terminating abnormally.This error message occurs when the launched process causes the initialization code in either User32.dll or Kernel32.dll to fail due to an API call from the launched process which does not have proper security access to either the targeted windowstation or desktop. For example, if the launched process 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 User32.dll 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 CreateProcessAsUser() to be interactive, the following windowstation and desktop combination should be specified:
winsta0\defaultThe following sample code below 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 CodeThe 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 cmd.exe. Note, an application which launched many processes such as a scheduler service may want to remove the new ACE after the process has completed since the ACEs would accumulate on the DACL of both the windowstation and desktop object.
#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 <windows.h>
#include <stdio.h>
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;
//
// 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);
//
// initilize 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;
//
// 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;
}
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Keywords : BseProcThrd BseSecurity kbprg
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