Security Related
Published: 2023-06-07 07:56:19

The code snippet you provided appears to be part of an authentication process in a C# application. It retrieves a user's record from a repository based on the provided username, compares the provided password with the stored password, and raises exceptions if the username or password is invalid. However, there are some security concerns that need to be addressed to ensure the security of the authentication process.

Here's a breakdown of the code snippet and some security considerations:

```csharp
var user = await this.userRepository.GetByLogin(username);
if (user == null)
{
    throw new HttpResponseException(StatusCodes.Status400BadRequest, "Invalid username!");
}
else if (user.Password != password)
{
    throw new HttpResponseException(StatusCodes.Status400BadRequest, "Invalid password!");
}
```

In this code:

1. `userRepository.GetByLogin(username)`: This method retrieves a user's record from a repository based on the provided username.

2. `user == null`: If the user is not found (i.e., `null`), an exception is thrown indicating an invalid username.

3. `user.Password != password`: If the stored password does not match the provided password, an exception is thrown indicating an invalid password.

However, there are some security considerations to address:

1. **Timing Attack:** The code performs a direct string comparison between the stored password and the provided password. To mitigate potential timing attacks, you should use a secure string comparison method that takes a constant amount of time, regardless of whether the password comparison succeeds or fails. For example, you can use `SecureString.Equals` or cryptographic libraries that provide secure comparison methods.

2. **Password Hashing:** It's important to note that storing plain text passwords in the database is a security risk. Passwords should be securely hashed using a strong cryptographic hashing algorithm (e.g., bcrypt, Argon2) with a unique salt for each user. The stored hash should be compared against the hashed input password, not the plain text password.

3. **Exception Messages:** Avoid disclosing sensitive information in your exception messages. Instead of revealing whether the username or password is invalid, provide a generic error message to prevent attackers from gaining information about valid usernames.

4. **Preventing Brute Force Attacks:** Implement mechanisms to prevent brute force attacks, such as account lockouts or rate limiting, to deter attackers from repeatedly trying different passwords.

5. **HTTPS:** Ensure that this authentication process occurs over a secure HTTPS connection to encrypt data transmitted between the client and the server.

By addressing these considerations and following secure authentication practices, you can enhance the security of your application's authentication process and protect user credentials from potential vulnerabilities.



WinVerifyTrust Signature Validation Vulnerability CVE-2013-3900 Security Vulnerability


Why is Microsoft republishing a CVE from 2013?

We are republishing CVE-2013-3900 in the Security Update Guide to update the Security Updates table and to inform customers that the EnableCertPaddingCheck is available in all currently supported versions of Windows 10 and Windows 11. While the format is different from the original CVE published in 2013, the information herein remains unchanged from the original text published on December 10, 2013.

Microsoft does not plan to enforce the stricter verification behavior as a default functionality on supported releases of Microsoft Windows. This behavior remains available as an opt-in feature via reg key setting, and is available on supported editions of Windows released since December 10, 2013. This includes all currently supported versions of Windows 10 and Windows 11. The supporting code for this reg key was incorporated at the time of release for Windows 10 and Windows 11, so no security update is required; however, the reg key must be set. See the Security Updates table for the list of affected software.

Vulnerability Description

```

A remote code execution vulnerability exists in the way that the WinVerifyTrust function handles Windows Authenticode signature verification for portable executable (PE) files.

```


```
An anonymous attacker could exploit the vulnerability by modifying an existing signed executable file to leverage 

unverified portions of the file in such a way as to add malicious code to the file without invalidating the signature
```


A certificate that is used to associate verifiable statements with an image. A number of different verifiable statements can be associated with a file; one of the most useful ones is a statement by a software manufacturer that indicates what the message digest of the image is expected to be. 

```
A message digest is similar to a checksum except that it is extremely difficult to forge. Therefore, it is very difficult to modify a file to have the same message digest as the original file. The statement can be verified as being made by the manufacturer by using public or private key cryptography schemes.
```
 This document describes details about attribute certificates other than to allow for their insertion into image files.


An attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

```
Exploitation of this vulnerability requires that a user or application run or install a specially crafted, signed PE file. An attacker could modify an existing signed file to include malicious code without invalidating the signature. This code would execute in the context of the privilege in which the signed PE file was launched.
```

In an email attack scenario, an attacker could exploit this vulnerability by sending a user an email message containing the specially crafted PE file and convincing the user to open the file.

In a web-based attack scenario, an attacker would have to host a website that contains a specially crafted PE file. In addition, compromised websites and websites that accept or host user-provided content could contain specially crafted content that could be used to exploit this vulnerability. An attacker would have no way to force users to visit a website that is hosting the specially crafted PE file. Instead, an attacker would have to convince users to visit the website, typically by getting them to click a link in an email message or Instant Messenger message that directs them to the attacker's website.

Update History

On December 10, 2013, Microsoft released an update for all supported releases of Microsoft Windows that changes how signatures are verified for binaries signed with the Windows Authenticode signature format. This change can be enabled on an opt-in basis. 

```
When enabled, the new behavior for Windows Authenticode signature verification will no longer allow extraneous information in the WIN_CERTIFICATE structure, and Windows will no longer recognize non-compliant binaries as signed. On July 29, 2014 Microsoft announced that it no longer plans to enforce the stricter verification behavior as a default functionality on supported releases of Microsoft Windows. To this date, it remains available as an opt-in feature in all currently supported releases of Microsoft Windows.
```

Recommendation. Microsoft recommends that executables authors consider conforming all signed binaries to the new verification standard by ensuring that they contain no extraneous information in the WIN_CERTIFICATE structure. Microsoft also recommends that customers appropriately test this change to evaluate how it will behave in their environments. Please see the Suggested Actions section for more information.


## Key things to note

`The moral of the story is the importance of proper padding in cryptographic hash functions to prevent vulnerabilities and exploit attempts. By not including padding in the hash-generated encrypted security digest, a vulnerability was created that allowed an attacker to add an extension to the hash and mimic a trusted certificate, thereby exploiting the system.

Realizing this vulnerability, the system has now implemented a command to add padding to the hash as part of the cryptography process. This addition aims to enhance the security of the system by preventing the exploitation that was possible due to the absence of proper padding in the hash function.

By incorporating padding into the hash, the system ensures that the resulting digest is more resistant to tampering and malicious manipulations. Padding adds additional bits or characters to the input data before generating the hash, making it harder for attackers to modify the hash without detection. This helps to maintain the integrity and trustworthiness of the cryptographic system and prevents unauthorized access or fraudulent activities.`




SQL Injection



https://www.youtube.com/watch?v=rRTCfOMOPMk




```SQL
SELECT * FROM items
WHERE owner = 'wiley'
AND itemname = 'name' OR 'a'='a';
```




 var user = await this.userRepository.GetByLogin(username);
            if (user == null)
            {
                throw new HttpResponseException(StatusCodes.Status400BadRequest, "Invalid username!");
            }
            else if (user.Password != password)
            {
                throw new HttpResponseException(StatusCodes.Status400BadRequest, "Invalid password!");
            }