To secure access to my router I wanted to use SSL encryption to access LuCi, so I obtained a certificate issued by a well-known CA. The server certificate was not issued directly off the CA, but there was a certificate chain in between.

Using a certificate chain with OpenWrt’s uhttpd is really easy, although as of today this is not yet even documented to be possible on the OpenWrt web site.

I’m using uhttpd_2015-11-08 from a trunk build (r48648) of “Designated Driver”, and certificate chains can be used here without problems.

I didn’t even have to convert from PEM to DER, I just concatenated the server cert and intermediate certs into a single file:

cat /root/server.crt /root/1_root_bundle_1.crt /root/1_root_bundle_2.crt >uhttpd.crt

Hope this helps. If it does please leave a message, thank you.