credentials-fetcher is a Linux daemon that retrieves gMSA credentials from Active Directory over LDAP. It creates and refreshes kerberos tickets from gMSA credentials. Kerberos tickets can be used by containers to run apps/services that authenticate using Active Directory.

This daemon works in a similar way as ccg.exe and the gMSA plugin in Windows as described in - https://docs.microsoft.com/en-us/virtualization/windowscontainers/manage-containers/manage-serviceaccounts#gmsa-architecture-and-improvements

On Fedora 36 and similar distributions, the binary RPM can be installed as sudo dnf install credentials-fetcher. You can also use yum if dnf is not present. The daemon can be started using sudo systemctl start credentials-fetcher.

On Enterprise Linux 9 ( RHEL | CentOS | AlmaLinux ), the binary can be installed from EPEL. To add EPEL, see the EPEL Quickstart. Once EPEL is enabled, install credentials-fetcher with sudo dnf install credentials-fetcher.

For other linux distributions, the daemon binary needs to be built from source code.

• Active Directory server ( Windows Server )
• Linux instances or hosts that are domain-joined to Active Directory
  • EC2 Linux containers on Amazon ECS provides the option of domainless gMSA and joining each instance to a single domain
  • Linux containers on Fargate must use domainless gMSA
• gMSA account(s) in Active Directory - Follow instructions provided to create service accounts - https://docs.microsoft.com/en-us/virtualization/windowscontainers/manage-containers/manage-serviceaccounts
• Required packages as mentioned in RPM spec file.
• Create username ec2-user or modify the systemd unit file.

• Create a domain joined windows instance
• Install powershell module - "Install-Module CredentialSpec"
• New-CredentialSpec -AccountName WebApp01 // Replace 'WebApp01' with your own gMSA
• You will find the credentialspec in the directory 'C:\Program Data\Docker\Credentialspecs\WebApp01_CredSpec.json'

To start a local dev environment from scratch:

* Clone the Git repository.
* cd credentials-fetcher && mkdir build
* cd build && cmake ../ && make -j
* ./credentials-fetcher to start the program in non-daemon mode.

To communicate with the daemon over gRPC, install grpc-cli. For example sudo yum install grpc-cli

Note: APIs use unix domain socket

Invoke the AddkerberosLease API with the credentialsspec input as shown:
grpc_cli call {unix_domain_socket} AddKerberosLease "credspec_contents: '{credentialspec}'"

Sample:
grpc_cli call unix:/var/credentials-fetcher/socket/credentials_fetcher.sock
AddKerberosLease "credspec_contents: '{\"CmsPlugins\":[\"ActiveDirectory\"],\"DomainJoinConfig\":{\"Sid\":\"S-1-5-21-4217655605-3681839426-3493040985\",
\"MachineAccountName\":\"WebApp01\",\"Guid\":\"af602f85-d754-4eea-9fa8-fd76810485f1\",\"DnsTreeName\":\"contoso.com\",
\"DnsName\":\"contoso.com\",\"NetBiosName\":\"contoso\"},\"ActiveDirectoryConfig\":{\"GroupManagedServiceAccounts\":[{\"Name\":\"WebApp01\",\"Scope\":\"contoso.com\"}
,{\"Name\":\"WebApp01\",\"Scope\":\"contoso\"}]}}'"

* Response:
  lease_id - unique identifier associated to the request
  created_kerberos_file_paths - Paths associated to the Kerberos tickets created corresponding to the gMSA accounts

Invoke the Delete kerberosLease API with lease id input as shown:
grpc_cli call {unix_domain_socket} DeleteKerberosLease "lease_id: '{lease_id}'"

Sample:
grpc_cli call unix:/var/credentials-fetcher/socket/credentials_fetcher.sock DeleteKerberosLease "lease_id: '${response_lease_id_from_add_kerberos_lease}'"

* Response:
    lease_id - unique identifier associated to the request
    deleted_kerberos_file_paths - Paths associated to the Kerberos tickets deleted corresponding to the gMSA accounts

Logs about request/response to the daemon and any failures.

journalctl -u credentials-fetcher

Credentials-fetcher in domainless mode assuming gMSA account 'WebApp01' has been setup as per https://learn.microsoft.com/en-us/virtualization/windowscontainers/manage-containers/manage-serviceaccounts#use-case-for-creating-gmsa-account-for-domain-joined-container-hosts

• Either launch Amazon-Linux 2023 instance or build from source and run.

• Make sure the instance/server is domain-joined using the realm list command in Linux.

• Make sure Credentials-fetcher is running using:

   journalctl -u credentials-fetcher
  

• Install grpc for python as per https://grpc.io/docs/languages/python/quickstart/

• Create the grpc pb2 files using credentialsfetcher.proto:

  # python3 -m grpc_tools.protoc -I. --python_out=. --grpc_python_out=. credentialsfetcher.proto
  

• Copy this code (Create the credspec and add it to the script as below ) (Alternatively, configure using the managed services at AWS ECS mode and AWS Fargate mode )

     # cat credentials_fetcher_client.py
     import grpc
     import credentialsfetcher_pb2
     import credentialsfetcher_pb2_grpc
  
     def run():
     with grpc.insecure_channel('unix:///var/credentials-fetcher/socket/credentials_fetcher.sock') as channel:
         stub = credentialsfetcher_pb2_grpc.CredentialsFetcherServiceStub(channel)
         credspec_contents="{\"CmsPlugins\":[\"ActiveDirectory\"],\"DomainJoinConfig\":{\"Sid\":\"S-1-5-21-2725122404-4129967127-2630707939\",\"MachineAccountName\":\"WebApp01\",\"Guid\":\"e96e0e09-9305-462f-9e44-8a8179722897\",\"DnsTreeName\":\"contoso.com\",\"DnsName\":\"contoso.com\",\"NetBiosName\":\"contoso\"},\"ActiveDirectoryConfig\":{\"GroupManagedServiceAccounts\":[{\"Name\":\"WebApp01\",\"Scope\":\"contoso.com\"},{\"Name\":\"WebApp01\",\"Scope\":\"contoso\"}]}}"
         contents = []
         contents  = [credspec_contents]
         response = stub.AddKerberosLease(credentialsfetcher_pb2.CreateKerberosLeaseRequest(credspec_contents = contents))
         print(f"Server response: {response}")
  
     if __name__ == '__main__':
         run()
  

• Configure Credentials-fetcher to create tickets for the 'WebApp01' gMSA account.

  # python3 credentials_fetcher_client.py
      Server response: lease_id: "94efba947d75728bbf70"
      created_kerberos_file_paths: "/var/credentials-fetcher/krbdir/94efba947d75728bbf70/WebApp01"
  

• Here is the resulting kerberos ticket that can be shared

    # klist  /var/credentials-fetcher/krbdir/94efba947d75728bbf70/WebApp01/krb5cc
        Ticket cache: FILE:/var/credentials-fetcher/krbdir/94efba947d75728bbf70/WebApp01/krb5cc
        Default principal: [email protected]
  
  Valid starting     Expires            Service principal
  07/17/24 22:42:42  07/18/24 08:42:42  krbtgt/[email protected]
    renew until 07/24/24 22:42:42
  

Credentials-fetcher in domainless mode assuming gMSA account 'WebApp01' has been setup as per https://learn.microsoft.com/en-us/virtualization/windowscontainers/manage-containers/manage-serviceaccounts#use-case-for-creating-gmsa-account-for-non-domain-joined-container-hosts ( Please substitute username, secret and password as needed)

• Run credentials-fetcher as follows:

    # credentials-fetcherd --aws_sm_secret_name aws/directoryservices/d-xxxxxx/gmsa // Substitute your secret name in AWS secrets manager
  

• Install grpc for python as per https://grpc.io/docs/languages/python/quickstart/

• Create the grpc pb2 files using credentialsfetcher.proto:

   # python3 -m grpc_tools.protoc -I. --python_out=. --grpc_python_out=. credentialsfetcher.proto
  

• Copy this code (Create the credspec and add it to the script as below ) (Alternatively, configure using the managed services at AWS ECS mode and AWS Fargate mode )

#  cat credentials_fetcher_client.py

    import grpc
    import credentialsfetcher_pb2
    import credentialsfetcher_pb2_grpc

    def run():
        with grpc.insecure_channel('unix:///var/credentials-fetcher/socket/credentials_fetcher.sock') as channel:
            stub = credentialsfetcher_pb2_grpc.CredentialsFetcherServiceStub(channel)
            credspec_contents="{\"CmsPlugins\":[\"ActiveDirectory\"],\"DomainJoinConfig\":{\"Sid\":\"S-1-5-21-2725122404-4129967127-2630707939\",\"MachineAccountName\":\"WebApp01\",\"Guid\":\"e96e0e09-9305-462f-9e44-8a8179722897\",\"DnsTreeName\":\"contoso.com\",\"DnsName\":\"contoso.com\",\"NetBiosName\":\"contoso\"},\"ActiveDirectoryConfig\":{\"GroupManagedServiceAccounts\":[{\"Name\":\"WebApp01\",\"Scope\":\"contoso.com\"},{\"Name\":\"WebApp01\",\"Scope\":\"contoso\"}]}}"
            contents = []
            contents  = [credspec_contents]
            response = stub.AddNonDomainJoinedKerberosLease(credentialsfetcher_pb2.CreateNonDomainJoinedKerberosLeaseRequest(credspec_contents = contents, username="admin", password="mypassword", domain="contoso.com"))
            print(f"Server response: {response}")

    if __name__ == '__main__':
        run()

• Configure Credentials-fetcher (in opensource mode) to create tickets for the 'WebApp01' gMSA account ( Alternatively, configure using the managed services at AWS ECS mode and AWS Fargate mode)

  # python3 credentials_fetcher_client.py
  
      Server response: lease_id: "34e2b89e3fd8a9bcb297"
      created_kerberos_file_paths: "/var/credentials-fetcher/krbdir/34e2b89e3fd8a9bcb297/WebApp01"
  

• Here is the resulting kerberos ticket that can be shared

  # klist  /var/credentials-fetcher/krbdir/34e2b89e3fd8a9bcb297/WebApp01/krb5cc
  
      Ticket cache: FILE:/var/credentials-fetcher/krbdir/34e2b89e3fd8a9bcb297/WebApp01/krb5cc
      Default principal: [email protected]
  
      Valid starting     Expires            Service principal
      07/17/24 22:10:29  07/18/24 08:10:29  krbtgt/[email protected]
          renew until 07/18/24 22:10:29
  

Running the Credentials-fetcher outside of Linux distributions is not supported.

Contributions and feedback are welcome! Proposals and pull requests will be considered and responded to. For more information, see the CONTRIBUTING.md file. If you have a bug/and issue around the behavior of the credentials-fetcher, please open it here.

Amazon Web Services does not currently provide support for modified copies of this software.

If you think you’ve found a potential security issue, please do not post it in the Issues. Instead, please follow the instructions here or email AWS security directly.

The Credentials Fetcher is licensed under the Apache 2.0 License. See LICENSE and NOTICE for more information.