programs: don't follow symbolic links and junctions in -r on Windows

programs/util.c

@@ -490,6 +490,17 @@ int UTIL_isBlockDevStat(const stat_t* statbuf)
     return 0;
 }
 
+#if defined(_WIN32)
+/* Symbolic links and junctions are "name surrogate" reparse points.
+ * Other reparse points (OneDrive placeholders, deduplicated files, ...)
+ * are regular files and directories : they must not be treated as links. */
+static int UTIL_isNameSurrogate(DWORD attributes, DWORD reparseTag)
+{
+    return (attributes & FILE_ATTRIBUTE_REPARSE_POINT)
+        && IsReparseTagNameSurrogate(reparseTag);
+}
+#endif
+
 int UTIL_isLink(const char* infilename)
 {
     UTIL_TRACE_CALL("UTIL_isLink(%s)", infilename);
@@ -503,6 +514,24 @@ int UTIL_isLink(const char* infilename)
             return 1;
         }
     }
+#elif defined(_WIN32)
+    {
+        DWORD const attributes = GetFileAttributesA(infilename);
+        if ( attributes != INVALID_FILE_ATTRIBUTES
+          && (attributes & FILE_ATTRIBUTE_REPARSE_POINT) ) {
+            /* GetFileAttributes() does not report the reparse tag, FindFirstFile() does */
+            WIN32_FIND_DATAA findData;
+            HANDLE const hFind = FindFirstFileA(infilename, &findData);
+            if (hFind != INVALID_HANDLE_VALUE) {
+                int const isLink = UTIL_isNameSurrogate(findData.dwFileAttributes, findData.dwReserved0);
+                FindClose(hFind);
+                if (isLink) {
+                    UTIL_TRACE_RET(1);
+                    return 1;
+                }
+            }
+        }
+    }
 #endif
     (void)infilename;
     UTIL_TRACE_RET(0);
@@ -942,6 +971,11 @@ static int UTIL_prepareFileList(const char* dirName,
         memcpy(path+dirLength+1, cFile.cFileName, fnameLength);
         pathLength = dirLength+1+fnameLength;
         path[pathLength] = 0;
+        if (!followLinks && UTIL_isNameSurrogate(cFile.dwFileAttributes, cFile.dwReserved0)) {
+            UTIL_DISPLAYLEVEL(2, "Warning : %s is a symbolic link, ignoring\n", path);
+            free(path);
+            continue;
+        }
         if (cFile.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) {
             if ( strcmp (cFile.cFileName, "..") == 0
               || strcmp (cFile.cFileName, ".") == 0 )

tests/playTests.sh

@@ -443,6 +443,34 @@ mkdir -p tmpEmptyDir
 zstd -r tmpEmptyDir
 rm -rf tmpEmptyDir
 
+println "test : directory links are not followed by -r"
+# remove leftovers of a previous failed run
+if [ "$isWindows" = true ]; then cmd //c "rmdir tmpLinkDir\tmpLink" 2> /dev/null || :; fi
+rm -rf tmpLinkDir tmpOutside tmpStdErr
+mkdir -p tmpLinkDir tmpOutside
+echo "inner" > tmpLinkDir/tmpInner
+echo "victim" > tmpOutside/tmpVictim
+if [ "$isWindows" = true ]; then
+  # junctions don't require the privileges that symlinks do
+  (cd tmpLinkDir && cmd //c "mklink /J tmpLink ..\tmpOutside")
+else
+  ln -s ../tmpOutside tmpLinkDir/tmpLink
+fi
+zstd -r --rm tmpLinkDir 2> tmpStdErr
+# remove the link before asserting, so a failing test never leaves a live
+# link behind for the later "rm -rf tmp*" cleanups to encounter
+if [ "$isWindows" = true ]; then
+  cmd //c "rmdir tmpLinkDir\tmpLink"
+else
+  rm -f tmpLinkDir/tmpLink
+fi
+$GREP "symbolic link" tmpStdErr
+test -f tmpLinkDir/tmpInner.zst # file inside the tree was compressed
+test ! -f tmpLinkDir/tmpInner # ... and removed (--rm)
+test -f tmpOutside/tmpVictim # file outside the tree was left untouched
+test ! -f tmpOutside/tmpVictim.zst # ... not compressed through the link
+rm -rf tmpLinkDir tmpOutside tmpStdErr
+
 
 println "\n===>  file removal"
 zstd -f --rm tmp