| commit | 00d080ff45b6d42ff9e7694548b8c6dc2ed306d0 | [log] [tgz] |
|---|---|---|
| author | Sam Elliott <selliott@lowrisc.org> | Tue Aug 04 17:26:43 2020 +0100 |
| committer | Sam Elliott <sam@lenary.co.uk> | Thu Aug 06 10:56:51 2020 +0100 |
| tree | 5b444737b88e680866a7a4f184f3160ea2b04524 | |
| parent | 6dd4e4a91fc52438ab9b07d01ce08a27bc64a49a [diff] |
[mask rom] Describe Mask ROM Interface Structures This PR describes the two main Mask ROM structures, which are also used as interfaces with other parts of the Secure Boot process. These structures are the Boot Policy structure, and the ROM_EXT manifest structure. This change settles some open questions: - How do we protect the Boot Policy structure: We'll use a checksum. - Can the Boot Policy choose different actions upon failing to parse a ROM_EXT manifest vs upon failing to authenticate the signature? No, the boot policy chooses the same action in both eventualities. These actions are coarse: either try the next ROM_EXT, or fail to boot. What these actions require the code to do may change depending on which step failed. - How do we end up versioning the ROM_EXT manifest: The versioning only changes how the BL0 area is parsed, the rest of the manifest has to be static as it is accessed by the Mask ROM (which cannot be updated). The BL0 area is still signed, but the OT Mask ROM makes no requirements on what information it includes. The ROM_EXT manifest version is outside the BL0 area as it is one of the software binding properties. This change introduces two new Open Questions: - Do we allow ROM_EXT manifests to choose their own entry point, or is the entry-point a hard-coded offset within the image? - Do we allow ROM_EXT manifests to set their own PMP region extents, or are these extents hard-coded too? Signed-off-by: Sam Elliott <selliott@lowrisc.org>
OpenTitan is an open source silicon Root of Trust (RoT) project. OpenTitan will make the silicon RoT design and implementation more transparent, trustworthy, and secure for enterprises, platform providers, and chip manufacturers. OpenTitan is administered by lowRISC CIC as a collaborative project to produce high quality, open IP for instantiation as a full-featured product. See the OpenTitan site and OpenTitan docs for more information about the project.
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