ElastiCache Redis Notes

This is a tiny app I created to play around with Redis. To run, just docker-compose up

Use Cases

Caching, queuing, locking, throttling, pub/sub

Redis Security

Designed to be on localhost or a closed network. Vanilla redis can only be access by 127.0.0.1 by default (no network access)

Later they added an AUTH command. It is basic password authentication. There is no encryption or password hashing algorithms involved. Redis is designed to servers requests at very high throughput thus the password is vulnerable to brute force by default.

Redis can support TLS but as always, there is some overhead with TLS.

https://redis.io/topics/encryption

By default, redis uses mtls

In AWS you may have some additional options

https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/redis-security.html

The general security architecture

AUTH command in AWS supports the ROTATE command after 5.0.5

Do not use EC2-classic deployments

Note: it is not possible to access elasticache directly through the public internet. All elasticache clusters are given only private ip addresses. This cannot be changed.

Credential Rotation

It is possible to rotate credentials using AWS Secrets Managers. While this is not supported out of the box, I was able to do a basic proof of concept rotating the credentials with Lambda. The basic concept is incredibly simple. Once a new credential is applied, the previous credential is still valid. Up to two credentials can be valid at once. The oldest credential is removed on rotation.

The following is a working Lambda code snippet that can modify Lambda ElastiCache cluster secrets. In practice, you may want to consider race condition or edge case scenarios.

const aws = require('aws-sdk')

const redis = new aws.ElastiCache()

exports.handler = async (event) => {
    try {
        return redis.modifyReplicationGroup({
          ReplicationGroupId: 'test',
          AuthToken: '91JAyZYTgekYj8COfGLU2',
          AuthTokenUpdateStrategy: 'Rotate',
          ApplyImmediately: true
        }).promise()
    } catch (err) {
        return err.message
    }
};

CA Authority

It looks like mutual TLS isn't a thing with AWS ElastiCache, but I was curious to see what the certificates looked like.

Certificate chain
0 s:/CN=*.test.7ybrx5.use1.cache.amazonaws.com
i:/C=US/O=Amazon/OU=Server CA 1B/CN=Amazon
-----BEGIN CERTIFICATE-----
MIIEgDCCA2igAwIBAgIQC2A3KU2x6YdprW6WplRuWjANBgkqhkiG9w0BAQsFADBG
MQswCQYDVQQGEwJVUzEPMA0GA1UEChMGQW1hem9uMRUwEwYDVQQLEwxTZXJ2ZXIg
Q0EgMUIxDzANBgNVBAMTBkFtYXpvbjAeFw0yMTAzMDEwMDAwMDBaFw0yMjAzMzAy
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8uKls1e6kmOuLUpSdZf31G/rxrTxFQlDu9oIYHvvTbxZC/b896QfGfX/Id1tEPof
FYWmvg==
-----END CERTIFICATE-----
1 s:/C=US/O=Amazon/OU=Server CA 1B/CN=Amazon
i:/C=US/O=Amazon/CN=Amazon Root CA 1
-----BEGIN CERTIFICATE-----
MIIESTCCAzGgAwIBAgITBn+UV4WH6Kx33rJTMlu8mYtWDTANBgkqhkiG9w0BAQsF
ADA5MQswCQYDVQQGEwJVUzEPMA0GA1UEChMGQW1hem9uMRkwFwYDVQQDExBBbWF6
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-----END CERTIFICATE-----
2 s:/C=US/O=Amazon/CN=Amazon Root CA 1
i:/C=US/ST=Arizona/L=Scottsdale/O=Starfield Technologies, Inc./CN=Starfield S
ervices Root Certificate Authority - G2
-----BEGIN CERTIFICATE-----
MIIEkjCCA3qgAwIBAgITBn+USionzfP6wq4rAfkI7rnExjANBgkqhkiG9w0BAQsF
ADCBmDELMAkGA1UEBhMCVVMxEDAOBgNVBAgTB0FyaXpvbmExEzARBgNVBAcTClNj
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-----END CERTIFICATE-----
3 s:/C=US/ST=Arizona/L=Scottsdale/O=Starfield Technologies, Inc./CN=Starfield S
ervices Root Certificate Authority - G2
i:/C=US/O=Starfield Technologies, Inc./OU=Starfield Class 2 Certification Aut
hority
-----BEGIN CERTIFICATE-----
MIIEdTCCA12gAwIBAgIJAKcOSkw0grd/MA0GCSqGSIb3DQEBCwUAMGgxCzAJBgNV
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-----END CERTIFICATE-----

briansimoni/elasticache-redis-notes

ElastiCache Redis Notes

Use Cases

Redis Security

Credential Rotation

CA Authority