tools fetch with hex digest password fails with code 400

Hi,

I’ve created a Dynamic DNS wrapper for Linux Bind9 using CherryPy and Apache, to allow proper DNS updates from our Mikrotik routers.

I’m trying to get /tool fetch to work with hex digest passwords.

The lines

/tool fetch url="http://$webServer/dnsupdate/updateDNS?name=$leaseHostname&ip=$leaseActIP&ttl=$leaseTTL" mode=http keep-result=no user=robot password=$password

/tool fetch url="http://$webServer/dnsupdate/deleteDNS?name=$leaseHostname" mode=http keep-result=no user=robot password=$password

Both fail with 400 (Bad Request) if the password is enabled on the server.
If I disable the password, the fetch works.
If I enable the password and enter the URL into a web browser, the browser (Firefox and IE10) both ask for a password and correctly return the page.

I know a solution would be to use https and plain text passwords, but why should this not work?

Regards,
Jason