Headline

GHSA-rrqh-93c8-j966: Ruby SAML DOS vulnerability with large SAML response

Summary

A denial-of-service vulnerability exists in ruby-saml even with the message_max_bytesize setting configured. The vulnerability occurs because the SAML response is validated for Base64 format prior to checking the message size, leading to potential resource exhaustion.

Details

ruby-saml includes a message_max_bytesize setting intended to prevent DOS attacks and decompression bombs. However, this protection is ineffective in some cases due to the order of operations in the code:

https://github.com/SAML-Toolkits/ruby-saml/blob/fbbedc978300deb9355a8e505849666974ef2e67/lib/onelogin/ruby-saml/saml_message.rb

      def decode_raw_saml(saml, settings = nil)
        return saml unless base64_encoded?(saml) # <--- Issue here. Should be moved after next code block.

        settings = OneLogin::RubySaml::Settings.new if settings.nil?
        if saml.bytesize > settings.message_max_bytesize
          raise ValidationError.new("Encoded SAML Message exceeds " + settings.message_max_bytesize.to_s + " bytes, so was rejected")
        end

        decoded = decode(saml)
        ...
      end

The vulnerability is in the execution order. Prior to checking bytesize the base64_encoded? function performs regex matching on the entire input string:

!!string.gsub(/[\r\n]|\\r|\\n|\s/, "").match(BASE64_FORMAT)

Impact

What kind of vulnerability is it? Who is impacted?

When successfully exploited, this vulnerability can lead to:

Excessive memory consumption
High CPU utilization
Application slowdown or unresponsiveness
Complete application crash in severe cases
Potential denial of service for legitimate users

All applications using ruby-saml with SAML configured and enabled are vulnerable.

Potential Solution

Reorder the validation steps to ensure max bytesize is checked first

def decode_raw_saml(saml, settings = nil)
  settings = OneLogin::RubySaml::Settings.new if settings.nil?

  if saml.bytesize > settings.message_max_bytesize
    raise ValidationError.new("Encoded SAML Message exceeds " + settings.message_max_bytesize.to_s + " bytes, so was rejected")
  end
  
  return saml unless base64_encoded?(saml)
  decoded = decode(saml)
  ...
end

23 hours ago

ghsa

Open in Source

#vulnerability #dos #git #ruby

Summary

Details

ruby-saml includes a message_max_bytesize setting intended to prevent DOS attacks and decompression bombs. However, this protection is ineffective in some cases due to the order of operations in the code:

https://github.com/SAML-Toolkits/ruby-saml/blob/fbbedc978300deb9355a8e505849666974ef2e67/lib/onelogin/ruby-saml/saml_message.rb

  def decode\_raw\_saml(saml, settings \= nil)
    return saml unless base64\_encoded?(saml) \# <--- Issue here. Should be moved after next code block.

    settings \= OneLogin::RubySaml::Settings.new if settings.nil?
    if saml.bytesize > settings.message\_max\_bytesize
      raise ValidationError.new("Encoded SAML Message exceeds " + settings.message\_max\_bytesize.to\_s + " bytes, so was rejected")
    end

    decoded \= decode(saml)
    ...
  end

The vulnerability is in the execution order. Prior to checking bytesize the base64_encoded? function performs regex matching on the entire input string:

!!string.gsub(/[\r\n]|\\r|\\n|\s/, “”).match(BASE64_FORMAT)

Impact

What kind of vulnerability is it? Who is impacted?

When successfully exploited, this vulnerability can lead to:

Excessive memory consumption
High CPU utilization
Application slowdown or unresponsiveness
Complete application crash in severe cases
Potential denial of service for legitimate users

All applications using ruby-saml with SAML configured and enabled are vulnerable.

Potential Solution

Reorder the validation steps to ensure max bytesize is checked first

def decode_raw_saml(saml, settings = nil) settings = OneLogin::RubySaml::Settings.new if settings.nil?

if saml.bytesize > settings.message_max_bytesize raise ValidationError.new(“Encoded SAML Message exceeds " + settings.message_max_bytesize.to_s + " bytes, so was rejected”) end

return saml unless base64_encoded?(saml) decoded = decode(saml) … end

References