Folder Sync certificate errors are not detected,

[jesjimher]

Describe the bug
My organization uses a transparent proxy, which doesn't require any configuration in applications, but that re-signs HTTP traffic with a custom certificate. Some applications that don't recognize this proxy certificate as valid, fail with an error.

In the case of Filen, two things happen in this scenario:

1. Mounting a network drive doesn't work, an error appears about a self-signed certificate detected. That's fine, good security here detecting an unknown certificate and complaining about it.
2. Folder sync doesn't work, at all. But in this case there's no error message, it just doesn't do anything, and Sync status says everything is ok and updated (when it isn't).

This latter case is worrying, because Filen doesn't seem to be aware that sync isn't working or that there's a problem with connection. Setting NODE_TLS_REJECT_UNAUTHORIZED environment variable (telling Filen to don't try validating HTTPS certificates) to 0 makes sync work OK.

This behavior, while pretty harmless when setting up a new sync folder, may lead to data loss in some scenarios. For example, if a sync folder is already set up and some HTTPS configuration changes, Filen may stop syncing without users acknowledging it.

To Reproduce
Steps to reproduce the behavior:

1. Use a corporate proxy that re-signs HTTPS traffic with some certificate
2. Create a sync folder in Filen
3. No files are synced, but Filen says everything is up-to-date. No events or problems are shown, no message in log files. No file is synced.
4. Exit Filen, set NODE_TLS_REJECT_UNAUTHORIZED=0 and start Filen again
5. Filen syncs folder correctly

Expected behavior
Filen should complain about certificate problems either in user interface, Sync folders "Problems" tab, or logs.

**OS

• OS: Windows 11
• Hardware configuration: Intel i7-12700, 32 GB RAM, 512 GB SSD
• Filesystem and Disk type used: SSD, NTFS

Additional context
Using Filen 3.0.47