security(mcp): harden validate_roots() and truncate_instructions()#2458
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security(mcp): harden validate_roots() and truncate_instructions()#2458
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Closes #2455: apply std::fs::canonicalize() in validate_roots() so that path traversal payloads (file:///etc/../secret) are resolved and rejected. Non-existent paths fall through with a warning to preserve compatibility with remote MCP servers. Closes #2456: apply sanitize_string() to server instructions in truncate_instructions() before length truncation, matching the sanitization already applied to tool descriptions.
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Summary
std::fs::canonicalize()invalidate_roots()to reject path traversal payloads (file:///etc/../secret). Non-existent paths fall through with aWARNlog to preserve compatibility with remote MCP servers.sanitize_string()to server instructions intruncate_instructions()before length truncation, matching the sanitization already applied to tool descriptions. Addedserver_id: &strparameter passed from both call sites.Test plan
validate_roots_file_uri_traversal_is_canonicalized— traversal URI is canonicalizedvalidate_roots_file_uri_is_kept— normal file:// URI passes throughtruncate_instructions_sanitizes_injection— injection patterns in server instructions are replaced with[sanitized]zeph-mcplib tests passCloses #2455
Closes #2456