the name of the "x-forwarded-proto" header  may be defined by the property

er.extensions.appserver.ERXRequest.xForwardedProtoHeaderKeyForSsl

E.g. the combo "IHS" (= IBM Apache Clone) and "WebSphere" uses the the header key "$wssc" instead of "x-forwarded-proto"...
Merge pull request #619 from renebock/x_forwarded_proto_for_ssl

Alternate Header for  "x-forwarded-proto"