* fix(security): prevent ReDoS in LLM-output tool/think parsers
The regexes that parse untrusted model output in text_helpers.py and
tool_parsing.py are delimiter-bounded with a lazy [\s\S]*? (or an
ambiguous (\s+[^>]*)?). Applied with re.sub/re.finditer over a whole
response, they degrade to O(n^2) when the closing delimiter is absent:
the engine rescans to end-of-string from every opener. Model output is
untrusted, so a prompt-injected or malicious model can stall the agent
loop with many unclosed openers (measured ~25s on a 60KB <thought flood).
- text_helpers.py: replace ambiguous <thought(\s+[^>]*)?> with
<thought([^>]*)> (identical capture, no \s+/[^>]* overlap); skip the
Gemma <|channel>...<channel|> subs when no <channel|> closer is present.
- tool_parsing.py: gate _TOOL_CALL_RE, _XML_TOOL_CALL_RE and _TOOL_CODE_RE
(in parse_tool_blocks and strip_tool_blocks) on a cheap presence check
for their closing delimiter. With no closer the regex cannot match, so
skipping is equivalent; only the wasted O(n^2) rescan is removed.
Resolves CodeQL py/polynomial-redos #230, #231, #232, #233, #235, #236,
#524. The _XML_OPEN_TOOL_CALL_RE alerts (#234, #477) are false positives
(its greedy [\s\S]*\Z is linear) and left untouched.
* fix(security): close ReDoS gaps in tool/think parsers from review
Addresses two review findings on the closer-guard approach:
- Whole-string "closer exists?" checks were bypassable: a stale closer
before an opener flood, or a closer with no reachable inner `}`, kept
the guard true while every opener still rescanned to end-of-string
(O(n^2)). Replace the substring guards with `_iter_delimited`, a
forward-only scan that pairs each opener with a *later* closer and
stops once none is reachable (O(n)). `parse_tool_blocks` and
`strip_tool_blocks` (via `_strip_delimited`) both use it for the
[TOOL_CALL], <tool_call>/<function_call>, and <tool_code> formats.
Verified equivalent to the original regexes on well-formed inputs.
- `<thought([^>]*)>` dropped the tag-name boundary and corrupted
unrelated tags (`<thoughtful>` -> `<thinkful>`). Use `<thought(\s[^>]*)?>`:
the single fixed `\s` keeps the pattern linear (no `\s+`/`[^>]*`
overlap) while restoring the boundary; capture is byte-for-byte
identical for real `<thought ...>` openers.
Adds regressions for stale-closer-before-opener, closer-present-without-
inner-brace, and the <thoughtful>/<thoughts> passthrough.
* fix(security): close Gemma channel ReDoS guard flagged in review
vdmkenny noted the same bypassable whole-string guard remained in
text_helpers.py: `if "<channel|>" in out.lower()` gating the Gemma
thought/response channel subs. A stale `<channel|>` before a
`<|channel>thought` opener flood keeps the guard true while every opener
still rescans to end-of-string (measured ~7.3s at 4k openers).
Replace it with `_sub_delimited`, the same forward-only scan used for the
tool-call parsers: pair each opener with a later closer, stop when none is
reachable (O(n)). Verified output-equivalent to the original capture regexes
on well-formed multi-channel inputs; the stale-closer case now runs in <2ms.
Adds a regression for stale-closer-before-opener on the Gemma path.
* fix(security): harden strip_think() think-tag ReDoS flagged in review
The earlier fixes hardened normalize_thinking_markup and the delimiter
scanners, but the production entrypoint strip_think() still ran
_THINK_CLOSED_RE / _THINK_ATTR_RE / _THINK_OPEN_RE (and the stray-tag
_THINK_TAG_RE) over untrusted model output. Those kept the same ReDoS
shapes: the lazy `<open>[\s\S]*?</close>` rescanned to end-of-string from
every opener, and `(?:\s+[^>]*)?` / `[^>]*` attribute scans ran to
end-of-string from every opener on a "many openers, no closer" flood. On
the prior head, malformed `<think` / `<thinking` / `<thought` floods took
6-14s through strip_think(). The shipped `<thought>` normalization had the
same residual: the single-opener case was linear but an opener flood was
still O(n^2) (~4.4s).
- Replace the lazy multi-pass _THINK_CLOSED_RE loop with the existing
forward-only _sub_delimited scan (pair each opener with the first
reachable closer, stop when none is reachable). One pass collapses
sequential and nested blocks as before.
- Bound every opener/stray-tag attribute scan at `<` (`[^<>]` not `[^>]`)
so a no-`>` opener flood can't drive a single match attempt to
end-of-string. Identical capture for well-formed think/thought tags.
- email_helpers._strip_think: compute had_think from the single linear
_THINK_TAG_RE instead of the lazy closed/open `.search()` calls, which
had the same O(n^2) on the email reply/summary/extraction paths.
All flood variants now finish in <10ms (were 6-14s). Output verified
byte-for-byte identical to the prior implementation over a 34-case corpus
(nested, mismatched, attr, uppercase, Gemma, prose, prompt-echo). Adds
strip_think() timing regressions for malformed openers, opener floods
(all three tag names), the closed-opener flood, and the malformed-closer
flood.
* docs: trim verbose comments in think-tag ReDoS fix
`strip_think` removes a dangling (unclosed) `<think>` block via
`_THINK_OPEN_RE`, but that pattern was anchored to the start of the string
(`^\s*<think>`). An unclosed `<think>` (or `<thinking>`) opener that
appears *after* any leading output was therefore only half-handled: the
stray tag itself was removed by `_THINK_TAG_RE`, but the reasoning content
following it leaked straight to the user.
strip_think("Hello! <think> I am thinking.") # -> "Hello! I am thinking." (leak)
strip_think("Sure.\n<think>\nLet me reconsider...") # -> leaks the reasoning
`strip_think` feeds user-facing output across research, email replies,
notes, and scheduled tasks, so this leaks chain-of-thought to end users.
Un-anchor `_THINK_OPEN_RE` so a dangling opener anywhere strips from the
opener to end of string, consistent with the existing start-of-string
behavior. Content before the opener, closed `<think>...</think>` blocks,
and tag-free text are all preserved.
tests/test_strip_think.py covers the mid-text leak (fails before this
change), start-anchored unclosed, closed blocks, no-tag passthrough,
content-before-opener, and mixed closed+unclosed. Full existing think
suite still passes.
nopoz