IIS deletes files after upload and returns status 550 after enabling FTPS

by jan.jonas   Last Updated September 11, 2019 16:00 PM - source

After enabling FTPS on our IIS webserver, I'm not able to upload files.

It does not seem to be a firewall or permission issue as I can login, list and delete files. I already double checked the port and IP settings in IIS and in the firewall. Also, from what I'm experiencing, it does not seem to be a network related issues as the client is able to transfer data to the server (see below).

Trying to upload a file shows the following log in FileZilla:

Command:  TYPE I
Response: 200 Type set to I.
Command:  PASV
Response: 227 Entering Passive Mode (XXX,XXX,XXX,XXX,234,224).
Command:  STOR [XXXXXX]
Response: 550
Error:    Critical file transfer error

If I set the IIS setting keepPartialUploads to true on the server side, the same error is still shown in the the client side, but I'm able to upload files.

To me it seems, that the clients sends something after the upload has finished, that the server does not understand or like and deletes the file that has just been uploaded.

Unfortunately, I have no idea how to further debug this issue.

Tags : iis ftp ftps

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