Credential and profile resolution - AWS SDK for .NET

Credential and profile resolution

The AWS SDK for .NET searches for credentials in a certain order and uses the first available set for the current application.

Credential search order
  1. Credentials that are explicitly set on the AWS service client, as described in Accessing credentials and profiles in an application.


    That topic is in the Special considerations section because it isn't the preferred method for specifying credentials.

  2. A credentials profile with the name specified by a value in AWSConfigs.AWSProfileName.

  3. A credentials profile with the name specified by the AWS_PROFILE environment variable.

  4. The [default] credentials profile.

  5. SessionAWSCredentials that are created from the AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_SESSION_TOKEN environment variables, if they're all non-empty.

  6. BasicAWSCredentials that are created from the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables, if they're both non-empty.

  7. IAM Roles for Tasks for Amazon ECS tasks.

  8. Amazon EC2 instance metadata.

If your application is running on an Amazon EC2 instance, such as in a production environment, use an IAM role as described in Granting access by using an IAM role. Otherwise, such as in prerelease testing, store your credentials in a file that uses the AWS credentials file format that your web application has access to on the server.

Profile resolution

With two different storage mechanisms for credentials, it's important to understand how to configure the AWS SDK for .NET to use them. The AWSConfigs.AWSProfilesLocation property controls how the AWS SDK for .NET finds credential profiles.

AWSProfilesLocation Profile resolution behavior

null (not set) or empty

Search the SDK Store if the platform supports it, and then search the shared AWS credentials file in the default location. If the profile isn't in either of those locations, search ~/.aws/config (Linux or macOS) or %USERPROFILE%\.aws\config (Windows).

The path to a file in the AWS credentials file format

Search only the specified file for a profile with the specified name.

Using federated user account credentials

Applications that use the AWS SDK for .NET (AWSSDK.Core version and later) can use federated user accounts through Active Directory Federation Services (AD FS) to access AWS services by using Security Assertion Markup Language (SAML).

Federated access support means users can authenticate using your Active Directory. Temporary credentials are granted to the user automatically. These temporary credentials, which are valid for one hour, are used when your application invokes AWS services. The SDK handles management of the temporary credentials. For domain-joined user accounts, if your application makes a call but the credentials have expired, the user is reauthenticated automatically and fresh credentials are granted. (For non-domain-joined accounts, the user is prompted to enter credentials before reauthentication.)

To use this support in your .NET application, you must first set up the role profile by using a PowerShell cmdlet. To learn how, see the AWS Tools for Windows PowerShell documentation.

After you set up the role profile, reference the profile in your application. There are a number of ways to do this, one of which is by using the AWSConfigs.AWSProfileName property in the same way you would with other credential profiles.

The AWS Security Token Service assembly (AWSSDK.SecurityToken) provides the SAML support to obtain AWS credentials. To use federated user account credentials, be sure this assembly is available to your application.

Specifying roles or temporary credentials

For applications that run on Amazon EC2 instances, the most secure way to manage credentials is to use IAM roles, as described in Granting access by using an IAM role.

For application scenarios in which the software executable is available to users outside your organization, we recommend that you design the software to use temporary security credentials. In addition to providing restricted access to AWS resources, these credentials have the benefit of expiring after a specified period of time. For more information about temporary security credentials, see the following:

Using proxy credentials

If your software communicates with AWS through a proxy, you can specify credentials for the proxy by using the ProxyCredentials property of the Config class of a service. The Config class of a service is typically part of the primary namespace for the service. Examples include the following: AmazonCloudDirectoryConfig in the Amazon.CloudDirectory namespace and AmazonGameLiftConfig in the Amazon.GameLift namespace.

For Amazon S3, for example, you could use code similar to the following, where SecurelyStoredUserName and SecurelyStoredPassword are the proxy user name and password specified in a NetworkCredential object.

AmazonS3Config config = new AmazonS3Config(); config.ProxyCredentials = new NetworkCredential(SecurelyStoredUserName, SecurelyStoredPassword);

Earlier versions of the SDK used ProxyUsername and ProxyPassword, but these properties are deprecated.