I still completely disagree. It’s on me to understand IAM. It should not be on me to understand the way that restic uses S3 such that I can determine whether I can credibly restore from an S3 bucket after a compromised client gets permission to create objects that didn’t previously exist. Or to create new corrupt versions of existing objects.

For that matter, suppose an attacker modifies an object and replaces it with corrupt or malicious contents, and I detect it, and the previous version still exists. Can the restic client, as written, actually manage the process of restoring it? I do not want to need to patch the client as part of my recovery plan.

(Compare to Tarsnap. By all accounts, if you backup up, your data is there. But there are more than enough reports of people who are unable to usefully recover the data because the client is unbelievably slow. The restore tool needs to do what the user needs it to do in order for the backup to be genuinely useful.)