rack-libinjection

rack-libinjection is a small native Ruby binding plus Rack middleware for libinjection.

It adds a tokenizer/fingerprint-based SQLi/XSS signal layer to Rack and Rails applications. It is report-only by default.

This is not a full WAF. The middleware scans only the configured Rack surfaces. The default is:

• parsed Rack params (scan: [:params])

Optional surfaces are available for raw query strings, path, headers, and cookies:

• scan: [:query] for a fast raw query-string signal that avoids Rack nested params parsing
• scan: [:params, :path, :headers, :cookies] for semantic params plus other Rack surfaces

The middleware can scan both SQLi and XSS signals by default, or only one class through threats: [:sqli] / threats: [:xss]. Path and raw-query values are decoded up to path_decode_depth times for detection inside the native extension, avoiding Ruby gsub/regex allocation on this hot path. Query/path/header-only configurations are scanned directly from the Rack env without constructing Rack::Request; params and cookies still use Rack parsers. Header scanning skips common low-signal protocol/browser headers by default through ignore_headers. Cookie values are scanned when :cookies is enabled; cookie names are skipped unless scan_cookie_names: true is configured. In mode: :block, native/Rack parser errors fail closed by default through parser_errors: :auto, and values skipped by max_value_bytes / max_depth fail closed by default through skipped_inputs: :auto.

Raw JSON body scanning is not part of the current middleware. JSON bodies, large request bodies, multipart file contents, and application-specific decoding need separate design. See GET_STARTED.md before deploying.

All installation, middleware configuration, low-level API examples, vendoring, system-library mode, GVL notes, threat model, and operational guidance live in GET_STARTED.md.

• A native binding to vendored libinjection v4.0.0.
• A Rack/Rails middleware that emits attack signals for configured request surfaces.
• A diagnostic API for SQLi fingerprints, parser contexts, SQL tokens, XSS contexts, and HTML5 tokens.
• A small signal layer that can feed logs, notifications, or Rack::Attack-style scoring.

• Not a full WAF.
• Not a replacement for Rails escaping, bind params, CSP, authorization, or upstream WAF/rate-limit protections.
• Not a promise to catch every SQLi/XSS payload.
• Not enabled in blocking mode by default.
• Not a JSON-body scanner yet.

The default build uses pinned, vendored libinjection sources. Source checkouts can regenerate or verify the vendored tree through script/vendor_libs.rb; see GET_STARTED.md for commands and system-library mode.

Report suspected vulnerabilities privately. See SECURITY.md.

The Ruby gem is MIT-licensed. The vendored upstream libinjection sources are BSD-3-Clause licensed and included as LICENSE-libinjection.txt.