This PR is a security hardning change and will break some setups.
The hardning is done to ensure the datafolder is not compromised and particularly that it is not maliciously seeded.
The changes now **requires** that the datafolder is locked down with exact permissions, or Duplicati will refuse to use it. This is a change to prior functionality where the folder would simply be locked down if it was not already locked.
Previously, a file named `insecure-permissions.txt` could be placed in the folder to instruct Duplicati not to set permissions. With this change that file is no longer supported.
The only way to opt-out of the permission check is to supply `--allow-insecure-datafolder` or the environment variable `DUPLICATI__ALLOW_INSECURE_DATAFOLDER`. Once either of those are set, Duplicati will no longer check permissions and accept folders with other permissions.
The setting can be applied to `preload.json`, but the file needs to be in a trusted location, which is either the directory with the binaries or the file pointed to by `DUPLICATI_PRELOAD_SETTINGS`. The setting cannot be placed in a `preload.json` file that is in an insecure folder as the folder is not read if the permissions are not correct.
The previous paths `/usr/local/share/Duplicati/preload.json` and `C:\ProgramData\Duplicati\preload.json` are no longer supported as they cannot be guaranteed to be locked down.
A `preload.json` in the datafolder is still supported, provided the folder passes the permission check (or the `--allow-insecure-datafolder` is passed to the executable).
For most users, this should not cause any problems as Duplicati has been locking down the folders, so they should be correctly locked down already.
The configuretool has been updated with a `secure-datafolder` command that can be used to force the correct permissions on a folder, in case the folder did not have the correct permissions.
For some Docker setups it may not be possible to set the permissions and the check will fail. These setup will need to apply `DUPLICATI__ALLOW_INSECURE_DATAFOLDER=true` in the image to run without the protections.
Kenneth Skovhede
a7ef8e42f2