关于获取进程完整性级别的问题

Namespace? 2018-07-28 09:37:12

最近在学windows安全，仔细看了大佬关于获取进程完整性级别方法，尽管查遍了MSDN可是仍有几处不解，代码如下：
BOOL GetProcessIntegrityLevel(HANDLE hProcess, PDWORD pIntegrityLevel,
PDWORD pPolicy, PDWORD pResourceIntegrityLevel, PDWORD pResourcePolicy) {

HANDLE hToken = NULL;
if (!OpenProcessToken(hProcess, TOKEN_READ, &hToken)) {
return(FALSE);
}

BOOL bReturn = FALSE;

// First, compute the size of the buffer to get the Integrity level
DWORD dwNeededSize = 0;
if (!GetTokenInformation(
hToken, TokenIntegrityLevel, NULL, 0, &dwNeededSize)) {

PTOKEN_MANDATORY_LABEL pTokenInfo = NULL;
if (GetLastError() == ERROR_INSUpFFICIENT_BUFFER) {
// Second, allocate a memory block with the the required size
pTokenInfo = (PTOKEN_MANDATORY_LABEL)LocalAlloc(0, dwNeededSize);
if (pTokenInfo != NULL) {
// And finally, ask for the integrity level
if (GetTokenInformation(hToken, TokenIntegrityLevel, pTokenInfo,
dwNeededSize, &dwNeededSize)) {

*pIntegrityLevel =
*GetSidSubAuthority(
pTokenInfo->Label.Sid,
(*GetSidSubAuthorityCount(pTokenInfo->Label.Sid)-1)
);
bReturn = TRUE;
}

// Don't forget to free the memory
LocalFree(pTokenInfo);
}
}
}

// Try to get the policy if the integrity level was available
if (bReturn) {
*pPolicy = TOKEN_MANDATORY_POLICY_OFF;
dwNeededSize = sizeof(DWORD);
GetTokenInformation(hToken, TokenMandatoryPolicy, pPolicy,
dwNeededSize, &dwNeededSize);
}

// Look for the resource policy
*pResourceIntegrityLevel = 0; // 0 means none explicitely set
*pResourcePolicy = 0;

PACL pSACL = NULL;
PSECURITY_DESCRIPTOR pSD = NULL;
DWORD dwResult = ERROR_SUCCESS;

// Look for the no-read-up/no-write-up policy in the SACL
if (hToken != NULL) {
dwResult =
GetSecurityInfo(
hProcess, SE_KERNEL_OBJECT,
LABEL_SECURITY_INFORMATION,
NULL, NULL, NULL,
&pSACL, &pSD
);
if (dwResult == ERROR_SUCCESS) {
if (pSACL != NULL) {
SYSTEM_MANDATORY_LABEL_ACE* pACE = NULL;
if ((pSACL->AceCount > 0) && (GetAce(pSACL, 0, (PVOID*)&pACE))) {
if (pACE != NULL) {
SID* pSID = (SID*)(&pACE->SidStart);
*pResourceIntegrityLevel = pSID->SubAuthority[0];
*pResourcePolicy = pACE->Mask;
}
}
}
}

// Cleanup memory allocated on our behalf
if (pSD != NULL) LocalFree(pSD);
}

// Don't forget to close the token handle.
CloseHandle(hToken);

return(bReturn);
}
我的疑问是
1.为什么获取完整性级别要在SID结构中的SubAuthority数组中取其最后一个数组值（绿色高光处），它前面的数组里都装了什么？
2.为什么获取资源完整性时又是在SID结构中的SubAuthority数组中取其第一个数组值（红色高光处）？
求大佬帮忙

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