Lack of data validation - Header x-amzn-RequestId
Need
Implementation of secure data validation for the x-amzn-RequestId Header
Context
• Usage of Ruby 2.0+ for developing Ruby applications
• Usage of ActionPack for handling web requests and generating responses in a Ruby on Rails application
• Usage of ActionController for handling actions and routing in a web application
Description
1. Non compliant code
class ApplicationController < ActionController::Base
before_action :set_request_id
private
def set_request_id
@request_id = request.headers['x-amzn-RequestId']
end...The above code demonstrates the vulnerability in question. It's a Ruby on Rails controller where we are extracting the 'x-amzn-RequestId' from the request headers and assigning it to an instance variable `@request_id`. Here, the application does not validate the 'x-amzn-RequestId' header value that it receives from the client. This means that an attacker could potentially send a harmful string in the 'x-amzn-RequestId' header, which could lead to various security issues such as SQL Injection, Cross-Site Scripting (XSS), or Remote Code Execution depending on how the `@request_id` is used in the application. The lack of input validation and sanitization is a common security issue. This is particularly dangerous when the input is used in a context that allows for command or query execution.
2. Steps
• Implement server-side validation for the x-amzn-RequestId header
• Define a whitelist of allowed characters for the x-amzn-RequestId header
• Validate the x-amzn-RequestId header against the whitelist of allowed characters
• Reject or sanitize any input that contains potentially dangerous characters
• Consider using a regular expression or a validation library to perform the validation
• Ensure that the validation is performed before using the value of the x-amzn-RequestId header
3. Secure code example
class ApplicationController < ActionController::Base
before_action :set_request_id
private
def set_request_id
request_id = request.headers['x-amzn-RequestId']
@request_id = request_id...The updated code includes a new method `valid_request_id?` that validates the `x-amzn-RequestId` header against a whitelist of allowed characters. The whitelist is defined as a regular expression, which in this example allows alphanumeric characters, hyphens, and underscores. If the `x-amzn-RequestId` header contains any characters not in the whitelist, the `valid_request_id?` method will return `false`, and the `set_request_id` method will not set the `@request_id` instance variable. This validation is performed before the value of the `x-amzn-RequestId` header is used, preventing potentially dangerous character strings from being entered. If the `x-amzn-RequestId` header is invalid, the `set_request_id` method handles it according to your application's error handling strategy. For example, you might want to log an error, raise an exception, or return a 400 response. This approach ensures that the application controls server-side permission to modify the `x-amzn-RequestId` header, mitigating the risk of injection attacks.