How to handle digest mismatches caused by intentional changes to resources?

[mjordan]

Since Riprap compares digest from the current fixity check with the digest from the previous fixity check, an intentional modification to a resource will produce a failed comparison. This problem is not specific to Riprap but will happen in any service that takes this approach to fixity monitoring over time, e.g. hashdeep, Fixity, Tripwire.

Riprap can store "event detail" data but populating it with notifications that a resources has been intentionally changed (and that a change in the digest value is expected) is beyond the scope of Riprap itself.

[mjordan]

This might be a bit far flung but on mismatch, a postcheck plugin could query a remote API to see if the there was a corresponding updated date, etc. on the resource, and if so, add an event detail note. In terms of Islandora, we could check the media file's modified property.

[mjordan]

Maybe we can pass extra info like last modified date into the check_fixity command. Currently, we only pass the resource's URI, but we might be able to serialize additional info as JSON. That would avoid having to do another call back to Drupal as suggested in my previous comment.

[mjordan]

Work on this postponed until we explore #31. issue-31 branch created from this branch at 6acab00.

[mjordan]

This appears to be working as intended in the issue-31 branch. All fetchresourcelist plugins now return an array of objects with the properties 'resource_id' and 'last_modified_timestamp'. Will close this after some more testing and when issue-31 is merged into master.

[mjordan]

Resolved as part of #31.