Merge pull request #14725 from RasmusWL/re-modeling

Python: Add taint-flow modeling for `re` module

python/ql/test/library-tests/frameworks/stdlib/test_re.py

@@ -0,0 +1,82 @@
+import re
+
+ts = TAINTED_STRING
+
+pat = ... # some pattern
+compiled_pat = re.compile(pat)
+
+# see https://docs.python.org/3/library/re.html#functions
+ensure_not_tainted(
+    # returns Match object, which is tested properly below. (note: with the flow summary
+    # modeling, objects containing tainted values are not themselves tainted).
+    re.search(pat, ts),
+    re.match(pat, ts),
+    re.fullmatch(pat, ts),
+
+    compiled_pat.search(ts),
+    compiled_pat.match(ts),
+    compiled_pat.fullmatch(ts),
+)
+
+# Match object
+tainted_match = re.match(pat, ts)
+safe_match = re.match(pat, "safe")
+ensure_tainted(
+    tainted_match.expand("Hello \1"), # $ tainted
+    safe_match.expand(ts), # $ tainted
+    tainted_match.group(), # $ tainted
+    tainted_match.group(1, 2), # $ tainted
+    tainted_match.group(1, 2)[0], # $ tainted
+    tainted_match[0], # $ tainted
+    tainted_match["key"], # $ tainted
+
+    tainted_match.groups()[0], # $ tainted
+    tainted_match.groupdict()["key"], # $ tainted
+
+    re.match(pat, ts).string, # $ tainted
+    re.match(ts, "safe").re.pattern, # $ tainted
+
+    compiled_pat.match(ts).string, # $ tainted
+    re.compile(ts).match("safe").re.pattern, # $ tainted
+)
+ensure_not_tainted(
+    safe_match.expand("Hello \1"),
+    safe_match.group(),
+
+    re.match(pat, "safe").re,
+    re.match(pat, "safe").string,
+)
+
+ensure_tainted(
+    # other functions not returning Match objects
+    re.split(pat, ts), # $ tainted
+    re.split(pat, ts)[0], # $ tainted
+
+    re.findall(pat, ts), # $ tainted
+    re.findall(pat, ts)[0], # $ tainted
+
+    re.finditer(pat, ts), # $ tainted
+    [x for x in re.finditer(pat, ts)], # $ tainted
+
+    re.sub(pat, repl="safe", string=ts), # $ tainted
+    re.sub(pat, repl=lambda m: ..., string=ts), # $ tainted
+    re.sub(pat, repl=ts, string="safe"), # $ tainted
+    re.sub(pat, repl=lambda m: ts, string="safe"), # $ tainted
+
+    # same for compiled patterns
+    compiled_pat.split(ts), # $ tainted
+    compiled_pat.split(ts)[0], # $ tainted
+    # ...
+
+    # user-controlled compiled pattern
+    re.compile(ts), # $ tainted
+    re.compile(ts).pattern, # $ tainted
+)
+
+ensure_not_tainted(
+    re.subn(pat, repl="safe", string=ts),
+    re.subn(pat, repl="safe", string=ts)[1], # // the number of substitutions made
+)
+ensure_tainted(
+    re.subn(pat, repl="safe", string=ts)[0], # $ tainted // the string
+)