[PATCH 0/1] MR2446: mscoree/tests: Avoid temporary directory name collisions.

[Francois Gouget (＠fgouget)]

test_loadpaths_execute() was sometimes getting ERROR_ALREADY_EXISTS when
creating its temporary directoryi. That was probably because
GetTempFileNameW() only uses the low 16-bits of the 'random' LUID which
goes over a wider range, potentially leading to collisions in the lower
16-bits.
Avoid AllocateLocallyUniqueId() entirely and add a helper function to
create a guaranteed new directory.
Also try to use the current directory first as it is assumed to have
been configured to ward off anti-virus programs (specifically
Microsoft Defender) which is especially important when writing
executables to that location. Only switch to the system's temporary
directory if the current directory is not a writable location.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54560
---
There are a few other tests where I suspect occasional anti-virus
interference. It may make sense to reuse this function in those.

That said create_new_dir() uses entirely predictable sequenitial
numbers which would be bad if attempting to create a secure directory.
But the new directory does not even have special permissions and this
type of attack shouldn't be an issue for the tests. Still, don't reuse
this code in contexts where security matters.

[PATCH 1/1] mscoree/tests: Avoid temporary directory name collisions.

[Francois Gouget]

From: Francois Gouget

test_loadpaths_execute() was sometimes getting ERROR_ALREADY_EXISTS when
creating its temporary directoryi. That was probably because
GetTempFileNameW() only uses the low 16-bits of the 'random' LUID which
goes over a wider range, potentially leading to collisions in the lower
16-bits.
Avoid AllocateLocallyUniqueId() entirely and add a helper function to
create a guaranteed new directory.
Also try to use the current directory first as it is assumed to have
been configured to ward off anti-virus programs (specifically
Microsoft Defender) which is especially important when writing
executables to that location. Only switch to the system's temporary
directory if the current directory is not a writable location.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54560
---
There are a few other tests where I suspect occasional anti-virus
interference. It may make sense to reuse this function in those.

That said create_new_dir() uses entirely predictable sequenitial
numbers which would be bad if attempting to create a secure directory.
But the new directory does not even have special permissions and this
type of attack shouldn't be an issue for the tests. Still, don't reuse
this code in contexts where security matters.
---
 dlls/mscoree/tests/mscoree.c | 55 +++++++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 13 deletions(-)

diff --git a/dlls/mscoree/tests/mscoree.c b/dlls/mscoree/tests/mscoree.c
index e5065a41d88..adac72e5f4c 100644
--- a/dlls/mscoree/tests/mscoree.c
+++ b/dlls/mscoree/tests/mscoree.c
@@ -592,25 +592,55 @@ static BOOL compile_cs(const WCHAR *source, const WCHAR *target, const WCHAR *ty
     return ret;
 }

+static BOOL create_new_dir(WCHAR newdir[MAX_PATH], const WCHAR* parent,
+                           const WCHAR* prefix)
+{
+    WCHAR path[MAX_PATH];
+    BOOL try_tmpdir = TRUE;
+    static unsigned i = 0;
+
+    if (!parent)
+    {
+        GetCurrentDirectoryW(ARRAY_SIZE(path), path);
+        parent = path;
+    }
+    while (1)
+    {
+        swprintf(newdir, MAX_PATH, L"%s\%s%04d", path, prefix, i);
+        if (CreateDirectoryW(newdir, NULL))
+            return TRUE;
+        switch (GetLastError())
+        {
+        case ERROR_ACCESS_DENIED:
+            if (!try_tmpdir)
+                return FALSE;
+            try_tmpdir = FALSE;
+            GetTempPathW(ARRAY_SIZE(path), path);
+            path[wcslen(path) - 1] = 0; /* redundant trailing backslash */
+            parent = path;
+            break;
+        case ERROR_ALREADY_EXISTS:
+            i++;
+            break;
+        default:
+            return FALSE;
+        }
+    }
+}
+
 static void test_loadpaths_execute(const WCHAR *exe_name, const WCHAR *dll_name, const WCHAR *cfg_name,
                                    const WCHAR *dll_dest, BOOL expect_failure, BOOL todo)
 {
-    WCHAR tmp[MAX_PATH], tmpdir[MAX_PATH], tmpexe[MAX_PATH], tmpcfg[MAX_PATH], tmpdll[MAX_PATH];
+    WCHAR tmpdir[MAX_PATH], tmpexe[MAX_PATH], tmpcfg[MAX_PATH], tmpdll[MAX_PATH];
     PROCESS_INFORMATION pi;
     STARTUPINFOW si = { 0 };
     WCHAR *ptr, *end;
     DWORD exit_code = 0xdeadbeef;
-    LUID id;
     BOOL ret;

-    GetTempPathW(MAX_PATH, tmp);
-    ret = AllocateLocallyUniqueId(&id);
-    ok(ret, "AllocateLocallyUniqueId failed: %lu\n", GetLastError());
-    ret = GetTempFileNameW(tmp, L"loadpaths", id.LowPart, tmpdir);
-    ok(ret, "GetTempFileNameW failed: %lu\n", GetLastError());
-
-    ret = CreateDirectoryW(tmpdir, NULL);
-    ok(ret, "CreateDirectoryW(%s) failed: %lu\n", debugstr_w(tmpdir), GetLastError());
+    ok(create_new_dir(tmpdir, NULL, L"loadpaths"),
+       "failed to create a new dir %lu\n", GetLastError());
+    end = tmpdir + wcslen(tmpdir);

wcscpy(tmpexe, tmpdir);
     PathAppendW(tmpexe, exe_name);
@@ -673,9 +703,8 @@ static void test_loadpaths_execute(const WCHAR *exe_name, const WCHAR *dll_name,
     ret = DeleteFileW(tmpexe);
     ok(ret, "DeleteFileW(%s) failed: %lu\n", debugstr_w(tmpexe), GetLastError());

-    end = tmpdir + wcslen(tmp);
-    ptr = tmpdir + wcslen(tmpdir) - 1;
-    while (ptr > end && (ptr = wcsrchr(tmpdir, '\')))
+    ptr = end;
+    while (ptr >= end && (ptr = wcsrchr(tmpdir, '\')))
     {
         ret = RemoveDirectoryW(tmpdir);
         ok(ret, "RemoveDirectoryW(%s) failed: %lu\n", debugstr_w(tmpdir), GetLastError());

[PATCH 0/1] MR2446: mscoree/tests: Avoid temporary directory name collisions. - approved

[Esme Povirk (＠madewokherd)]

This merge request was approved by Esme Povirk.