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Lack of data validation - URL

Need​

Implementation of robust data validation for URL parameters

Context​

  • Usage of C# for building robust and scalable applications
  • Usage of _context for managing state and data in a specific context
  • Usage of IActionResult for handling and returning HTTP responses in a structured manner
  • Usage of the "where" package for filtering data based on specific conditions
  • Usage of ToList for converting data into a list format
  • Usage of the Ok library for handling HTTP responses

Description​

Non compliant code​

[HttpGet]
public IActionResult GetDocuments(string date)
{
    var documents = _context.Documents.Where(d => d.Date == date).ToList();
    return Ok(documents);
}

In the above code, we have an HTTP GET endpoint GetDocuments that accepts a date as a parameter. It fetches all the documents from the database that were sent on the provided date.

The vulnerability lies in the fact that there's no validation or authentication on who can access this endpoint. Any user who knows the URL can simply pass in a date as a parameter and get all the documents sent on that day. This is a serious security flaw as it can lead to data leakage.

Furthermore, there's also no validation on the date parameter. This means a user can potentially input harmful or malicious data, leading to potential SQL injection attacks.

In summary, the lack of data validation and absence of user authentication makes this piece of code vulnerable to data leakage and potential SQL injection attacks.

Steps​

  • Implement input validation to ensure that the 'date' parameter is in the expected format and within a valid range.
  • Use parameterized queries or stored procedures to prevent SQL injection attacks.
  • Limit the amount of sensitive information returned in the response, such as excluding personally identifiable information (PII) from the 'documents' object.
  • Consider implementing authentication and authorization mechanisms to restrict access to the 'GetDocuments' endpoint.
  • Regularly update and patch the ASP.NET Core framework and dependencies to address any security vulnerabilities.

Compliant code​

[HttpGet]
[Authorize]
public IActionResult GetDocuments(string date)
{
    DateTime parsedDate;
    if (!DateTime.TryParse(date, out parsedDate))
    {
        return BadRequest("Invalid date format");
    }

    var documents = _context.Documents
                            .Where(d => d.Date == parsedDate)
                            .Select(d => new { d.Id, d.Date, d.Title }) // Exclude sensitive data
                            .ToList();

    return Ok(documents);
}

The updated code includes several changes to address the identified vulnerability:

  1. Input Validation: The DateTime.TryParse method is used to validate that the 'date' parameter is in the correct format. If the date is not valid, a BadRequest response is returned.

  2. Authentication and Authorization: The [Authorize] attribute is added to the GetDocuments method. This ensures that only authenticated users can access this endpoint.

  3. Limiting Sensitive Data: The Select method is used to exclude sensitive data from the response. In this case, only the document's Id, Date, and Title are returned. Any other properties, such as those containing personally identifiable information (PII), are excluded.

  4. Parameterized Queries: The Entity Framework Core, which is used in this code, already uses parameterized queries to prevent SQL injection attacks.

  5. Regular Updates and Patches: Although not shown in the code, it's important to regularly update and patch the ASP.NET Core framework and any dependencies to address any security vulnerabilities. This can be done through regular maintenance and updates of the application's environment.

References​

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