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security: mitigate ReDoS in proxy view_request regex search #876

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security: mitigate ReDoS in proxy view_request regex search #876

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44 changes: 28 additions & 16 deletions strix/tools/proxy/tools.py
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Original file line number Diff line number Diff line change
Expand Up @@ -315,23 +315,35 @@ def _format_search_hits(content: str, pattern: str) -> dict[str, Any]:
except re.error as exc:
return {"success": False, "error": f"Invalid regex: {exc}"}

hits = []
for match in regex.finditer(content):
start, end = match.span()
before = content[max(0, start - 40) : start]
after = content[end : end + 40]
hits.append(
{
"match": match.group(0),
"position": start,
"before": before,
"after": after,
},
)
if len(hits) >= 20:
break
# Guard against catastrophic backtracking (ReDoS): truncate the
# haystack so even a worst-case pattern cannot consume unbounded CPU.
_MAX_SEARCH_LEN = 1_048_576 # 1 MiB
search_content = content[:_MAX_SEARCH_LEN]
truncated = len(content) > _MAX_SEARCH_LEN

Comment on lines +320 to 323

@greptile-apps greptile-apps Bot Jul 25, 2026

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P1 security Regex execution remains unbounded

When an agent searches an adversarial HTTP body with a catastrophic-backtracking expression such as (a+)+$, truncating the body to 1 MiB still permits exponential work on much shorter inputs, causing the synchronous search to block the event loop indefinitely; catching exceptions after finditer() returns does not enforce an execution bound.

How this was verified: view_request passes the agent-supplied pattern and decoded HTTP content directly to synchronous regex.finditer() without a regex timeout or interruptible execution boundary.

Knowledge Base Used: Tools Overview

Prompt To Fix With AI 
This is a comment left during a code review.
Path: strix/tools/proxy/tools.py
Line: 320-323

Comment:
**Regex execution remains unbounded**

When an agent searches an adversarial HTTP body with a catastrophic-backtracking expression such as `(a+)+$`, truncating the body to 1 MiB still permits exponential work on much shorter inputs, causing the synchronous search to block the event loop indefinitely; catching exceptions after `finditer()` returns does not enforce an execution bound.

**How this was verified:** `view_request` passes the agent-supplied pattern and decoded HTTP content directly to synchronous `regex.finditer()` without a regex timeout or interruptible execution boundary.

**Knowledge Base Used:** [Tools Overview](https://app.greptile.com/strix-org-3/-/custom-context/knowledge-base/usestrix/strix/-/docs/tools-overview.md)

How can I resolve this? If you propose a fix, please make it concise.

return {"success": True, "hits": hits, "total_hits": len(hits)}
hits = []
try:
for match in regex.finditer(search_content):
start, end = match.span()
before = search_content[max(0, start - 40) : start]
after = search_content[end : end + 40]
hits.append(
{
"match": match.group(0),
"position": start,
"before": before,
"after": after,
},
)
if len(hits) >= 20:
break
except (re.error, RecursionError) as exc:
return {"success": False, "error": f"Regex execution failed: {exc}"}

result: dict[str, Any] = {"success": True, "hits": hits, "total_hits": len(hits)}
if truncated:
result["warning"] = f"Content truncated to {_MAX_SEARCH_LEN} bytes for search"
return result


def _format_text_page(content: str, *, page: int, page_size: int) -> dict[str, Any]:
Expand Down