Background
Error code 18452 occurs when a user tries to connect to an Azure SQL Database or SQL Server using Windows Authentication, but the login attempt fails because the user is not authenticated in a trusted domain or the connection is configured to use SQL Server Authentication instead of Windows Authentication.
This error is often encountered in scenarios where the user is trying to connect from a different domain that is not trusted by the server or when using Windows Authentication in environments where it is not supported (like Azure SQL Database).
Summary Table
| Aspect | Details |
|---|---|
| Error Code | 18452 |
| Error Message | Login failed. The login is from an untrusted domain and cannot be used with Windows authentication. |
| Background | Occurs when trying to use Windows Authentication in an environment where it is not supported. |
| Common Causes | 1. Windows Authentication in Azure SQL Database 2. Domain trust issues 3. Misconfigured connection string |
| Workarounds | 1. Use SQL Authentication 2. Use Azure AD Authentication 3. Enable Mixed Mode (for on-premises SQL Server) |
| Solutions | 1. Modify connection string to use SQL Authentication 2. Enable Azure AD Authentication 3. Verify domain trust relationships |
| Example SQL Authentication | Server=tcp:yourserver.database.windows.net,1433;Database=yourdb;User ID=youruser;Password=yourpassword;Encrypt=true; |
Error Explanation
The error message typically looks like this:
Error 18452: Login failed. The login is from an untrusted domain and cannot be used with Windows authentication.
This occurs when a client attempts to connect to the server using Windows Authentication, but the login cannot be authenticated because:
- The server does not recognize the domain of the user.
- Azure SQL Database does not support Windows Authentication by default (SQL Authentication is typically required).
- The user does not have appropriate domain permissions.
Common Causes
- Untrusted Domain: The user attempting to log in is from a domain that is not trusted by the SQL Server.
- Windows Authentication Attempt on Azure SQL: Azure SQL Database does not support Windows Authentication directly; it primarily supports SQL Authentication and Azure Active Directory (AAD) Authentication.
- Misconfigured Connection String: The connection string is set to use Windows Authentication (
Integrated Security=true), but the Azure SQL Database or SQL Server is not set up for it. - Kerberos or NTLM Authentication Issues: Issues with Kerberos or NTLM authentication protocols in on-premise SQL Server or hybrid cloud environments.
Steps to Troubleshoot and Resolve Error Code 18452
1. Check Authentication Mode in Azure SQL Database
Azure SQL Database does not support Windows Authentication like on-premises SQL Server does. Instead, it supports:
- SQL Authentication (username and password).
- Azure Active Directory (AAD) Authentication.
To resolve the issue, you should use SQL Authentication or configure Azure AD Authentication if your environment requires integration with your domain identities.
Example for SQL Authentication:
Server=tcp:yourserver.database.windows.net,1433;Database=yourdb;User ID=youruser;Password=yourpassword;Encrypt=true;
Make sure you are not using Windows Authentication (Integrated Security=true) in the connection string for Azure SQL Database, as that will not work.
2. Switch to SQL Authentication in Connection String
If your connection string is incorrectly set to use Windows Authentication, you need to modify it to use SQL Authentication. Here’s an example:
Incorrect Connection String (Windows Authentication):
Server=tcp:yourserver.database.windows.net,1433;Database=yourdb;Integrated Security=true;
Correct Connection String (SQL Authentication):
Server=tcp:yourserver.database.windows.net,1433;Database=yourdb;User ID=youruser;Password=yourpassword;Encrypt=true;
In the correct version, the Integrated Security=true part is removed and replaced with User ID and Password fields for SQL Authentication.
3. Enable Azure Active Directory (AAD) Authentication
If your environment requires domain-based authentication, configure Azure Active Directory (AAD) Authentication. AAD Authentication allows users to authenticate against Azure SQL Database using their organizational identities managed in Azure AD.
Steps to Enable Azure AD Authentication:
- Go to Azure Portal.
- Navigate to your SQL Server instance.
- Under Settings, select Active Directory admin.
- Click Set admin, and select a user or group from Azure AD to act as the Azure AD admin.
- Save the changes.
Now, users can authenticate to the database using their Azure AD credentials.
Example Connection String for Azure AD Authentication:
Server=tcp:yourserver.database.windows.net,1433;Database=yourdb;Authentication=Active Directory Integrated;
Or for Azure AD Password Authentication:
Server=tcp:yourserver.database.windows.net,1433;Database=yourdb;Authentication=Active Directory Password;UID=youruser@yourdomain.com;PWD=yourpassword;
4. Check Domain Trust Relationships (For On-premises SQL Server)
If you’re encountering this error in an on-premises SQL Server environment, check if the domain where the user resides is trusted by the SQL Server’s domain. You can verify this with your system administrator or through Active Directory configurations.
In case of a missing or broken trust between domains:
- Ensure a two-way trust relationship exists between the domains.
- If the user is from a different domain, either add a trust between the domains or use SQL Authentication.
5. Check SQL Server Authentication Mode (For On-premises SQL Server)
SQL Server has two authentication modes:
- Windows Authentication Mode: Only Windows Authentication is allowed.
- Mixed Mode: Both Windows and SQL Server Authentication are allowed.
If you’re using on-premises SQL Server and SQL Authentication is not enabled, switch to Mixed Mode to allow SQL Server logins.
Steps to Change SQL Server Authentication Mode:
- Open SQL Server Management Studio (SSMS).
- Right-click on the SQL Server instance and select Properties.
- In the Security tab, under Server authentication, select SQL Server and Windows Authentication mode (Mixed Mode).
- Click OK and restart the SQL Server service.
6. Check Kerberos and NTLM Authentication Issues (For On-premises SQL Server)
In on-premises SQL Server environments, authentication failures may also be caused by problems with Kerberos or NTLM. If Kerberos authentication is not configured correctly, it might fall back to NTLM, which could result in this error.
Check the SPN (Service Principal Name) settings to ensure that Kerberos authentication is properly configured.
Workarounds
- Use SQL Authentication: If Windows Authentication is not required, switch to SQL Authentication, which is supported by Azure SQL Database.
- Use Azure AD Authentication: If you need domain-based authentication, configure Azure Active Directory Authentication for Azure SQL Database.
- Enable Mixed Mode: For on-premises SQL Server, switch to Mixed Mode to allow both Windows and SQL Authentication.
Solutions
- Use SQL Authentication: Modify the connection string to use SQL Authentication instead of Windows Authentication in Azure SQL Database.
- Enable Azure AD Authentication: Configure Azure Active Directory Authentication if domain-based authentication is required.
- Verify Domain Trust: Ensure that there is a trust relationship between the user’s domain and the SQL Server’s domain (for on-premises SQL Server).
- Switch to Mixed Mode: Enable SQL Server and Windows Authentication Mode (Mixed Mode) if SQL Authentication is required in an on-premises environment.
- Check SPN and Kerberos Configuration: Ensure that Kerberos is configured correctly for Windows Authentication in an on-premises environment.
Example Scenario
Suppose you’re using an Azure SQL Database and trying to connect using the following connection string:
Server=tcp:yourserver.database.windows.net,1433;Database=yourdb;Integrated Security=true;
You receive the following error:
Error 18452: Login failed. The login is from an untrusted domain and cannot be used with Windows authentication.
Step 1: You realize that Azure SQL Database does not support Windows Authentication by default. So, you switch to SQL Authentication by modifying the connection string to:
Server=tcp:yourserver.database.windows.net,1433;Database=yourdb;User ID=youruser;Password=yourpassword;Encrypt=true;
Step 2: If your organization requires domain-based authentication, you configure Azure AD Authentication by setting the Active Directory admin in the Azure Portal.
Step 3: After updating the connection string to use SQL Authentication or Azure AD Authentication, the connection succeeds.
By following these steps, you can resolve Error 18452 when connecting to an Azure SQL Database or SQL Server, ensuring that the correct authentication method is used.
