Securing Aurora PostgreSQL data with SSL/TLS

Security with Amazon Aurora PostgreSQL

For a general overview of Aurora security, see Security in Amazon Aurora. You can manage security for Amazon Aurora PostgreSQL at a few different levels:

To control who can perform Amazon RDS management actions on Aurora PostgreSQL DB clusters and DB instances, use AWS Identity and Access Management (IAM). IAM handles the authentication of user identity before the user can access the service. It also handles authorization, that is, whether the user is allowed to do what they're trying to do. IAM database authentication is an additional authentication method that you can choose when you create your Aurora PostgreSQL DB cluster. For more information, see Identity and access management for Amazon Aurora.

If you do use IAM with your Aurora PostgreSQL DB cluster, sign in to the AWS Management Console with your IAM credentials first, before opening the Amazon RDS console at https://console.aws.amazon.com/rds/.
Make sure to create Aurora DB clusters in a virtual public cloud (VPC) based on the Amazon VPC service. To control which devices and Amazon EC2 instances can open connections to the endpoint and port of the DB instance for Aurora DB clusters in a VPC, use a VPC security group. You can make these endpoint and port connections by using Secure Sockets Layer (SSL). In addition, firewall rules at your company can control whether devices running at your company can open connections to a DB instance. For more information on VPCs, see Amazon VPC VPCs and Amazon Aurora.

The supported VPC tenancy depends on the DB instance class used by your Aurora PostgreSQL DB clusters. With default VPC tenancy, the VPC runs on shared hardware. With dedicated VPC tenancy, the VPC runs on a dedicated hardware instance. The burstable performance DB instance classes support default VPC tenancy only. The burstable performance DB instance classes include the db.t3 and db.t4g DB instance classes. All other Aurora PostgreSQL DB instance classes support both default and dedicated VPC tenancy.

For more information about instance classes, see Aurora DB instance classes. For more information about default and dedicated VPC tenancy, see Dedicated instances in the Amazon Elastic Compute Cloud User Guide.
To grant permissions to the PostgreSQL databases running on your Amazon Aurora DB cluster, you can take the same general approach as with stand-alone instances of PostgreSQL. Commands such as CREATE ROLE, ALTER ROLE, GRANT, and REVOKE work just as they do in on-premises databases, as does directly modifying databases, schemas, and tables.

PostgreSQL manages privileges by using roles. The rds_superuser role is the most privileged role on an Aurora PostgreSQL DB cluster. This role is created automatically, and it's granted to the user that creates the DB cluster (the master user account, postgres by default). To learn more, see Understanding PostgreSQL roles and permissions.

Aurora PostgreSQL 14.3 and higher releases support the Salted Challenge Response Authentication Mechanism (SCRAM) for passwords as an alternative to message digest (MD5). We recommend that you use SCRAM because it's more secure than MD5. For more information, including how to migrate database user passwords from MD5 to SCRAM, see Using SCRAM for PostgreSQL password encryption.

Securing Aurora PostgreSQL data with SSL/TLS

Amazon RDS supports Secure Socket Layer (SSL) and Transport Layer Security (TLS) encryption for Aurora PostgreSQL DB clusters. Using SSL/TLS, you can encrypt a connection between your applications and your Aurora PostgreSQL DB clusters. You can also force all connections to your Aurora PostgreSQL DB cluster to use SSL/TLS. Amazon Aurora PostgreSQL supports Transport Layer Security (TLS) versions 1.1 and 1.2. We recommend using TLS 1.2 for encrypted connections.

For general information about SSL/TLS support and PostgreSQL databases, see SSL support in the PostgreSQL documentation. For information about using an SSL/TLS connection over JDBC, see Configuring the client in the PostgreSQL documentation.

Topics

Requiring an SSL/TLS connection to an Aurora PostgreSQL DB cluster
Determining the SSL/TLS connection status
Configuring cipher suites for connections to Aurora PostgreSQL DB clusters

SSL/TLS support is available in all AWS Regions for Aurora PostgreSQL. Amazon RDS creates an SSL/TLS certificate for your Aurora PostgreSQL DB cluster when the DB cluster is created. If you enable SSL/TLS certificate verification, then the SSL/TLS certificate includes the DB cluster endpoint as the Common Name (CN) for the SSL/TLS certificate to guard against spoofing attacks.

To connect to an Aurora PostgreSQL DB cluster over SSL/TLS

Download the certificate.

For information about downloading certificates, see Using SSL/TLS to encrypt a connection to a DB cluster.
Import the certificate into your operating system.
Connect to your Aurora PostgreSQL DB cluster over SSL/TLS.

When you connect using SSL/TLS, your client can choose to verify the certificate chain or not. If your connection parameters specify sslmode=verify-ca or sslmode=verify-full, then your client requires the RDS CA certificates to be in their trust store or referenced in the connection URL. This requirement is to verify the certificate chain that signs your database certificate.

When a client, such as psql or JDBC, is configured with SSL/TLS support, the client first tries to connect to the database with SSL/TLS by default. If the client can't connect with SSL/TLS, it reverts to connecting without SSL/TLS. The default sslmode mode used is different between libpq-based clients (such as psql) and JDBC. The libpq-based clients default to prefer, where JDBC clients default to verify-full.

Use the sslrootcert parameter to reference the certificate, for example sslrootcert=rds-ssl-ca-cert.pem.

The following is an example of using psql to connect to an Aurora PostgreSQL DB cluster.


$ psql -h testpg.cdhmuqifdpib.us-east-1.rds.amazonaws.com -p 5432 \
    "dbname=testpg user=testuser sslrootcert=rds-ca-2015-root.pem sslmode=verify-full"

Requiring an SSL/TLS connection to an Aurora PostgreSQL DB cluster

You can require that connections to your Aurora PostgreSQL DB cluster use SSL/TLS by using the rds.force_ssl parameter. By default, the rds.force_ssl parameter is set to 0 (off). You can set the rds.force_ssl parameter to 1 (on) to require SSL/TLS for connections to your DB cluster. Updating the rds.force_ssl parameter also sets the PostgreSQL ssl parameter to 1 (on) and modifies your DB cluster's pg_hba.conf file to support the new SSL/TLS configuration.

You can set the rds.force_ssl parameter value by updating the DB cluster parameter group for your DB cluster. If the DB cluster parameter group isn't the default one, and the ssl parameter is already set to 1 when you set rds.force_ssl to 1, you don't need to reboot your DB cluster. Otherwise, you must reboot your DB cluster for the change to take effect. For more information on parameter groups, see Working with parameter groups.

When the rds.force_ssl parameter is set to 1 for a DB cluster, you see output similar to the following when you connect, indicating that SSL/TLS is now required:



$ psql postgres -h SOMEHOST.amazonaws.com -p 8192 -U someuser
psql (9.3.12, server 9.4.4)
WARNING: psql major version 9.3, server major version 9.4.
Some psql features might not work.
SSL connection (cipher: DHE-RSA-AES256-SHA, bits: 256)
Type "help" for help.

postgres=>

Determining the SSL/TLS connection status

The encrypted status of your connection is shown in the logon banner when you connect to the DB cluster.


Password for user master: 
psql (9.3.12) 
SSL connection (cipher: DHE-RSA-AES256-SHA, bits: 256) 
Type "help" for help.   

postgres=>

You can also load the sslinfo extension and then call the ssl_is_used() function to determine if SSL/TLS is being used. The function returns t if the connection is using SSL/TLS, otherwise it returns f.



postgres=> create extension sslinfo;
CREATE EXTENSION

postgres=> select ssl_is_used();
 ssl_is_used
---------
t
(1 row)

You can use the select ssl_cipher() command to determine the SSL/TLS cipher:



postgres=> select ssl_cipher();
ssl_cipher
--------------------
DHE-RSA-AES256-SHA
(1 row)

If you enable set rds.force_ssl and restart your DB cluster, non-SSL connections are refused with the following message:



$ export PGSSLMODE=disable
$ psql postgres -h SOMEHOST.amazonaws.com -p 8192 -U someuser
psql: FATAL: no pg_hba.conf entry for host "host.ip", user "someuser", database "postgres", SSL off
$

For information about the sslmode option, see Database connection control functions in the PostgreSQL documentation.

Configuring cipher suites for connections to Aurora PostgreSQL DB clusters

By using configurable cipher suites, you can have more control over the security of your database connections. You can specify a list of cipher suites that you want to allow to secure client SSL/TLS connections to your database. With configurable cipher suites, you can control the connection encryption that your database server accepts. Doing this helps prevent the use of insecure or deprecated ciphers.

Configurable cipher suites is supported in Aurora PostgreSQL versions 11.8 and higher.

To specify the list of permissible ciphers for encrypting connections, modify the ssl_ciphers cluster parameter. Set the ssl_ciphers parameter in a cluster parameter group using the AWS Management Console, the AWS CLI, or the RDS API. To set cluster parameters, see Modifying parameters in a DB cluster parameter group.

Set the ssl_ciphers parameter to a string of comma-separated cipher values. The valid ciphers include the following:

ECDHE-RSA-AES128-SHA
ECDHE-RSA-AES128-SHA256
ECDHE-RSA-AES128-GCM-SHA256
ECDHE-RSA-AES256-SHA
ECDHE-RSA-AES256-GCM-SHA384

You can also use the describe-engine-default-cluster-parameters CLI command to determine which cipher suites are currently supported for a specific parameter group family. The following example shows how to get the allowed values for the ssl_cipher cluster parameter for Aurora PostgreSQL 11.


aws rds describe-engine-default-cluster-parameters --db-parameter-group-family aurora-postgresql11
                
    ...some output truncated...
	{
		"ParameterName": "ssl_ciphers",
		"Description": "Sets the list of allowed TLS ciphers to be used on secure connections.",
		"Source": "engine-default",
		"ApplyType": "dynamic",
		"DataType": "list",
		"AllowedValues": "ECDHE-RSA-AES256-GCM-SHA384,ECDHE-RSA-AES256-SHA384,AES256-SHA,AES128-SHA,DES-CBC3-SHA,ADH-DES-CBC3-SHA,EDH-RSA-DES-CBC3-SHA,EDH-DSS-DES-CBC3-SHA,ADH-AES256-SHA,DHE-RSA-AES256-SHA,DHE-DSS-AES256-SHA,ADH-AES128-SHA,DHE-RSA-AES128-SHA,DHE-DSS-AES128-SHA,HIGH",
		"IsModifiable": true,
		"MinimumEngineVersion": "11.8",
		"SupportedEngineModes": [
			"provisioned"
		]
	},
    ...some output truncated...

The ssl_ciphers parameter has no default string of cipher suites. For more information about ciphers, see the ssl_ciphers variable in the PostgreSQL documentation. For more information about cipher suite formats, see the openssl-ciphers list format and openssl-ciphers string format documentation on the OpenSSL website.

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Document Conventions

Working with Aurora PostgreSQL

Understanding PostgreSQL roles and permissions