Friday, June 26, 2015

Using AWS KMS with Apache CXF to secure passwords

The previous tutorial showed how the AWS Key Management Service (KMS) can be used to generate symmetric encryption keys that can be used with WS-Security to encrypt and decrypt a service request using Apache CXF. It is also possible to use the KMS to secure keystore passwords for asymmetric encryption and signature, that are typically stored in properties files when using WS-Security with Apache CXF.

1) Encrypting passwords in a Crypto properties file

Apache CXF uses the WSS4J Crypto interface to get keys and certificates for asymmetric encryption/decryption and for signature creation/verification. Merlin is the standard implementation, based around two JDK keystores for key/cert retrieval, and trust verification. Typically, a Crypto implementation is loaded and configured via a Crypto properties file. For example:

However one issue with this style of configuration is that the keystore password is stored in plaintext in the file. Apache WSS4J 2.0.0 introduced the ability to store encrypted passwords in the crypto properties file instead. A PasswordEncryptor interface was defined to allow for the encryption/decryption of passwords, and a default implementation based on Jasypt was made available in the release. In this case, the master password used to decrypt the encrypted keystore password was retrieved from a CallbackHandler implementation.

2) Using KMS to encrypt keystore passwords

Instead of using the Jasypt PasswordEncryptor implementation provided by default in Apache WSS4J, it is possible to use instead the AWS KMS to decrypt encrypted keystore passwords stored in crypto properties files. I've updated the test-case introduced in the previous tutorial with an asymmetric encryption test-case, where a SOAP service invocation is encrypted using a WS-SecurityPolicy AsymmetricBinding policy.

The first step in running the test-case is to follow the previous tutorial in terms of registering for AWS, creating a user "alice" and a corresponding customer master key. One you have this, then run the "testEncryptedPasswords" test available here, which outputs the encrypted passwords for the client and service keystores ("cspass" and "sspass"). Copy the output + paste them into the and in the "ENC()" tags. For example:

The client and service configure a custom PasswordEncryptor implementation designed to decrypt the encrypted keystore password using KMS. The KMSPasswordEncryptor is spring-loaded in the client and service configuration, and must be updated with the access key id, secret key, master key id, etc. as defined earlier. Of course this means that the secret key is in plaintext in a spring configuration file in this example. However, it could be obtained via a system property or some other means, and is more secure than storing a plaintext keystore password in a properties file. Once the KMSPasswordEncryptor is properly configured, then the AsymmetricTest can be run, and you will see the secured service request and response in the console window.

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