Don't allow the same private key to be used by more than one configured log

[robstradling]

Each log/shard is expected to use a unique keypair. This is stated explicitly in RFC9162, and although not clearly stated in RFC6962 (AFAICT) it is strongly implied. If two logs share the same private key, then cryptographically speaking they should be considered as split views of the same log.

This PR ensures that no two logs in the CTFE configuration use the same private key.

h/t to @AlCutter for suggesting this check.

Checklist

• I have updated the CHANGELOG.
  • Adjust the draft version number according to semantic versioning rules.
• I have updated documentation accordingly.

[roger2hk]

/gcbrun

[robstradling]

The CI build failure is expected, because the logs configured in ct_integration_test.cfg and ct_lifecycle_test.cfg all share the same keypair. ;-)

[robstradling]

The CI build failure is expected, because the logs configured in ct_integration_test.cfg and ct_lifecycle_test.cfg all share the same keypair. ;-)

Please post another /gcbrun comment. I've generated unique key pairs for each of the integration test logs, so the CI build should now succeed. Thanks.

[AlCutter]

/gcbrun

[AlCutter]

/gcbrun

[robstradling]

Another CI build failure:
Step #6 - "etcd_with_coverage": /workspace/trillian/integration/ct_functions.sh: line 118: ./createtree: Text file busy
Any idea how to resolve this?

[AlCutter]

Another CI build failure: Step #6 - "etcd_with_coverage": /workspace/trillian/integration/ct_functions.sh: line 118: ./createtree: Text file busy Any idea how to resolve this?

Ah, that's a flake - just need to kick it again, hang on...

[robstradling]

Different error this time:
Step #7 - "etcd_with_race": /workspace/trillian/integration/ct_functions.sh: line 118: ./createtree: No such file or directory
Another kick needed?

[AlCutter]

Hmm, that's unexpected...

[robstradling]

Successful!