Summary

An error occurs on validating the GPG key of DataStax as of 1st of August 2020
The following signatures were invalid: EXPKEYSIG 350200F2B999A372 Riptano Package Repository <paul@riptano.com>

Applies to

• DataStax Debian Repository key
• Linux Debian and Ubuntu

Symptoms

Following error may appear when running sudo apt update on Debian or Ubuntu

- Error on Ubuntu 18.04

Hit:25 https://debian.datastax.com/enterprise stable InRelease                                          
Err:25 https://debian.datastax.com/enterprise stable InRelease
  The following signatures were invalid: EXPKEYSIG 350200F2B999A372 Riptano Package Repository <paul@riptano.com>
...
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://debian.datastax.com/enterprise stable InRelease: The following signatures were invalid: EXPKEYSIG 350200F2B999A372 Riptano Package Repository <paul@riptano.com>
W: Failed to fetch https://debian.datastax.com/enterprise/dists/stable/InRelease  The following signatures were invalid: EXPKEYSIG 350200F2B999A372 Riptano Package Repository <paul@riptano.com>
W: Some index files failed to download. They have been ignored, or old ones used instead.

- Error on Ubuntu 16.04

  W: An error occurred during the signature verification. The repository is not
  updated and the previous index files will be used. GPG error: https://debian.datastax.com/enterprise
  stable InRelease: The following signatures were invalid: KEYEXPIRED 1596313119
  KEYEXPIRED 1596313119 KEYEXPIRED 1596313119

  W: Failed to fetch https://debian.datastax.com/enterprise/dists/stable/InRelease
  The following signatures were invalid: KEYEXPIRED 1596313119 KEYEXPIRED 1596313119
  KEYEXPIRED 1596313119

Cause

Looking in sudo apt-key list, the original key for DataStax has expired as of 1st of August 2020

pub   rsa2048 2010-08-12 [SC] [expired: 2020-08-01]
      7E41 C00F 85BF C170 6C4F  FFB3 3502 00F2 B999 A372
uid           [ expired] Riptano Package Repository <paul@riptano.com>

Solution

As per the Debian install guide, please add the updated key:
curl -L https://debian.datastax.com/debian/repo_key | sudo apt-key add -

This should reflect in the sudo apt-key list with a key valid until 2024, and subsequent sudo apt update will not show the error anymore