futility: Support for signing RO+RW firmware

This adds the "rwsig" type, with initial support for RO+RW
firmware images that need to verify themselves instead of using
software sync. This uses our vb2 structs instead of raw binary
blobs. That will help us locate, identify, and verify the keys
and signatures in the signed firmware images.

TEST=make runtests

I also hacked up a test board with the EC-side signature
verification routines from a preliminary CL and tested this
signing scheme with that. It works.

Additional work is needed to make this seamless, but you can try
it out like so:

  futility create ./tests/testkeys/key_rsa2048.pem foo

  futility sign --type rwsig --prikey foo.vbprik2 --pubkey foo.vbpubk2 ec.bin

Change-Id: I876ab312a2b0b36411c5f739fe3252529728d034
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/305394
Reviewed-by: Randall Spangler <rspangler@chromium.org>
7 files changed