MCP find_in_file: 'before'/'after' have no upper bound (mirrors excerpt)

[Widthdom]

Summary

The MCP find_in_file tool mirrors the unbounded before / after issue from excerpt: only the lower bound (< 0) is validated, leaving the upper bound open to arbitrary client values.

Evidence

src/CodeIndex/Mcp/McpToolHandlers.cs:1087-1095:

var beforeValue = args?["before"]?.GetValue<int>();
if (beforeValue.HasValue && beforeValue.Value < 0)
    return CreateToolErrorResponse(id, "before must be greater than or equal to 0");
var before = beforeValue ?? 0;

var afterValue = args?["after"]?.GetValue<int>();
if (afterValue.HasValue && afterValue.Value < 0)
    return CreateToolErrorResponse(id, "after must be greater than or equal to 0");
var after = afterValue ?? 0;

When find_in_file matches N lines, each match expands by before + after, so the raw cost is O(matches * (before + after)).

Impact

• Same DoS class as the excerpt issue but multiplied by match count: 100 matches in one file × before=1000, after=1000 = 200K context lines.
• Worst case can blow past the 1 MB McpServer.MaxLineLength.

Proposed direction

Share a ClampWindow helper with excerpt. Cap and signal truncation in the response.

Repro env

• Branch: main @ 2ee912d (release v1.21.0)

[Widthdom]

Work started on branch codex/fix-issue1413-1414-1593-1597-1930.