But this only works on files with a file:// URI.
There's no way to open remote files directly (I doubt that most OSes support it anyway...)
What mechanism should I pick to allow me to save a remote HTTP/S stream to an nsILocalFile, and do I need to save to a temp file first to open with the default MIME handler or if there a mechanism that'll achieve this for me?
You do need to save to a temp file. I would suggest using nsIDownloader for that purpose.
smime.p7s
Description: S/MIME Cryptographic Signature
