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gh-114096: Restore privileges in _winapi.CreateJunction #114089

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Jan 16, 2024
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Process privileges that are activated for creating directory junctions are
now restored afterwards, avoiding behaviour changes in other parts of the
program.
28 changes: 21 additions & 7 deletions Modules/_winapi.c
Original file line number Diff line number Diff line change
Expand Up @@ -532,7 +532,12 @@ _winapi_CreateJunction_impl(PyObject *module, LPCWSTR src_path,
{
/* Privilege adjustment */
HANDLE token = NULL;
TOKEN_PRIVILEGES tp;
struct {
TOKEN_PRIVILEGES base;
/* overallocate by a few array elements */
LUID_AND_ATTRIBUTES privs[4];
} tp, previousTp;
int previousTpSize = 0;

/* Reparse data buffer */
const USHORT prefix_len = 4;
Expand All @@ -556,17 +561,21 @@ _winapi_CreateJunction_impl(PyObject *module, LPCWSTR src_path,

/* Adjust privileges to allow rewriting directory entry as a
junction point. */
if (!OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES, &token))
if (!OpenProcessToken(GetCurrentProcess(),
TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &token)) {
goto cleanup;
}

if (!LookupPrivilegeValue(NULL, SE_RESTORE_NAME, &tp.Privileges[0].Luid))
if (!LookupPrivilegeValue(NULL, SE_RESTORE_NAME, &tp.base.Privileges[0].Luid)) {
goto cleanup;
}

tp.PrivilegeCount = 1;
tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
if (!AdjustTokenPrivileges(token, FALSE, &tp, sizeof(TOKEN_PRIVILEGES),
NULL, NULL))
tp.base.PrivilegeCount = 1;
tp.base.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
if (!AdjustTokenPrivileges(token, FALSE, &tp.base, sizeof(previousTp),
&previousTp.base, &previousTpSize)) {
goto cleanup;
}

if (GetFileAttributesW(src_path) == INVALID_FILE_ATTRIBUTES)
goto cleanup;
Expand Down Expand Up @@ -647,6 +656,11 @@ _winapi_CreateJunction_impl(PyObject *module, LPCWSTR src_path,
cleanup:
ret = GetLastError();

if (previousTpSize) {
AdjustTokenPrivileges(token, FALSE, &previousTp.base, previousTpSize,
NULL, NULL);
}

if (token != NULL)
CloseHandle(token);
if (junction != NULL)
Expand Down