1 files changed, 47 insertions, 0 deletions
diff --git a/pyload/lib/SafeEval.py b/pyload/lib/SafeEval.py
new file mode 100644
index 000000000..8fc57f261
--- /dev/null
+++ b/pyload/lib/SafeEval.py
@@ -0,0 +1,47 @@
+## {{{ http://code.activestate.com/recipes/286134/ (r3) (modified)
+import dis
+
+_const_codes = map(dis.opmap.__getitem__, [
+    'POP_TOP','ROT_TWO','ROT_THREE','ROT_FOUR','DUP_TOP',
+    'BUILD_LIST','BUILD_MAP','BUILD_TUPLE',
+    'LOAD_CONST','RETURN_VALUE','STORE_SUBSCR'
+    ])
+
+
+_load_names = ['False', 'True', 'null', 'true', 'false']
+
+_locals = {'null': None, 'true': True, 'false': False}
+
+def _get_opcodes(codeobj):
+    i = 0
+    opcodes = []
+    s = codeobj.co_code
+    names = codeobj.co_names
+    while i < len(s):
+        code = ord(s[i])
+        opcodes.append(code)
+        if code >= dis.HAVE_ARGUMENT:
+            i += 3
+        else:
+            i += 1
+    return opcodes, names
+
+def test_expr(expr, allowed_codes):
+    try:
+        c = compile(expr, "", "eval")
+    except:
+        raise ValueError, "%s is not a valid expression" % expr
+    codes, names = _get_opcodes(c)
+    for code in codes:
+        if code not in allowed_codes:
+            for n in names:
+                if n not in _load_names:
+                    raise ValueError, "opcode %s not allowed" % dis.opname[code]
+    return c
+
+
+def const_eval(expr):
+    c = test_expr(expr, _const_codes)
+    return eval(c, None, _locals)
+
+## end of http://code.activestate.com/recipes/286134/ }}}