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Further prevent ability to access memory on Windows #10618

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merged 1 commit into from
Apr 29, 2024
Merged

Further prevent ability to access memory on Windows #10618

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31 changes: 26 additions & 5 deletions src/core/Bootstrap.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,8 @@ namespace Bootstrap
DWORD cbBufferSize = 0;
PSID pLocalSystemSid = nullptr;
DWORD pLocalSystemSidSize = SECURITY_MAX_SID_SIZE;
PSID pOwnerRightsSid = nullptr;
DWORD pOwnerRightsSidSize = SECURITY_MAX_SID_SIZE;

// Access control list
PACL pACL = nullptr;
Expand Down Expand Up @@ -165,9 +167,20 @@ namespace Bootstrap
goto Cleanup;
}

// Retrieve CreaterOwnerRights SID
pOwnerRightsSid = static_cast<PSID>(HeapAlloc(GetProcessHeap(), 0, pOwnerRightsSidSize));
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if (pOwnerRightsSid == nullptr) {
goto Cleanup;
}

if (!CreateWellKnownSid(WinCreatorOwnerRightsSid, nullptr, pOwnerRightsSid, &pOwnerRightsSidSize)) {
auto error = GetLastError();
goto Cleanup;
}

// Calculate the amount of memory that must be allocated for the DACL
cbACL = sizeof(ACL) + sizeof(ACCESS_ALLOWED_ACE) + GetLengthSid(pTokenUser->User.Sid)
+ sizeof(ACCESS_ALLOWED_ACE) + GetLengthSid(pLocalSystemSid);
+ sizeof(ACCESS_ALLOWED_ACE) + GetLengthSid(pLocalSystemSid) + GetLengthSid(pOwnerRightsSid);

// Create and initialize an ACL
pACL = static_cast<PACL>(HeapAlloc(GetProcessHeap(), 0, cbACL));
Expand All @@ -189,6 +202,11 @@ namespace Bootstrap
goto Cleanup;
}

// Explicitly set "Process Owner" rights to Read Only. The default is Full Control.
if (!AddAccessAllowedAce(pACL, ACL_REVISION, READ_CONTROL, pOwnerRightsSid)) {
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goto Cleanup;
}

#ifdef WITH_XC_SSHAGENT
// OpenSSH for Windows ssh-agent service is running as LocalSystem
if (!AddAccessAllowedAce(pACL,
Expand All @@ -213,16 +231,19 @@ namespace Bootstrap

Cleanup:

if (pACL != nullptr) {
if (pACL) {
HeapFree(GetProcessHeap(), 0, pACL);
}
if (pLocalSystemSid != nullptr) {
if (pLocalSystemSid) {
HeapFree(GetProcessHeap(), 0, pLocalSystemSid);
}
if (pTokenUser != nullptr) {
if (pOwnerRightsSid) {
HeapFree(GetProcessHeap(), 0, pOwnerRightsSid);
}
if (pTokenUser) {
HeapFree(GetProcessHeap(), 0, pTokenUser);
}
if (hToken != nullptr) {
if (hToken) {
CloseHandle(hToken);
}
#endif
Expand Down