minio-restic-policy.json

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "s3:*"
      ],
      "Resource": [
        "arn:aws:s3:::restic/locks",
        "arn:aws:s3:::restic/locks/*"
      ]
    },
    {
      "Effect": "Allow",
      "Action": [
        "s3:ListBucket",
        "s3:GetObject",
        "s3:PutObject"
      ],
      "Resource": [
        "arn:aws:s3:::restic/*"
      ]
    }
  ]
}

The policy outline above allows restic to perform a backup and read-only operations. Per design forget and prune commands are NOT permitted. This is especially useful when running scheduled backup tasks on remote machines. To increase security create a dedicated user (here someuser) per machine.

The bucket name is here restic, if your bucket differs please change the policy above accordingly.

$ mc admin user add myminio someuser
$ mc admin policy add myminio backup minio-restic-policy.json
$ mc admin policy set myminio backup user=someuser
$ mc admin user policy myminio someuser

Tested with restic v0.12.0 and minio RELEASE.2021-06-17T00-10-46Z