Partial key autonomy
Contents
Proposal 1
Maintain the firmware and dev-key status quo while permitting everything else to be modified.
Essentially, I propose to fork the firmware in a standard way for anyone who asks but to keep the resulting firmware update key private.
In more detail, for each party P who so requests,
- OLPC asks party P to generate and to supply the public portions of these keys:
- P_OS_key -- per Firmware security, guards the theft-deterrence code-path through the kernel and initramfs
- P_FS_key -- see the bottom of OFW's loaddropins.fth; opens the NAND reflash lock.
- P_LEASE_key -- per Firmware security, opens the activation lock
- P_OATS_key -- per Theft deterrence protocol and Mass olpc-update, verifies theft-deterrence messages.
- OLPC generates a new firmware update key specific to P's customization request named OLPC_P_FW_key, per Firmware security.
Then, throughout the future, OLPC may generate and sign firmware containing the public values of these keys. The keys
- OLPC_FW_key
- OLPC_DEVELOP_key
- and the OLPC_P_FW_key for each party P
should be escrowed for safe-keeping should OLPC cease to exist.
Finally, by installing an appropriate OLPC_FW_key-signed P-customized firmwares on a stock machine, each party P will be able to provide builds and activation leases and will be able to execute or modify the theft-deterrence protocol for that machine autonomously from all other parties Q, including OLPC. Party P may also further delegate these abilities, e.g. with version-2 lease signatures. OLPC will retain responsibility for providing developer keys and firmware updates.
Benefits
In addition to providing much-requested autonomy who people who want to control all the other locks on their laptops, this proposal preserves the status quo in three important ways:
- OLPC can generate developer keys itself
- Developer keys remain all-powerful for the laptops for which they are generated
- If v2 signature checking is implemented in the firmware, OLPC can delegate its ability to generate developer keys to others on a per-laptop basis
Risks
However, the implementation of the proposal would incur several risks:
- it somewhat complicates the task of making, testing, distributing, and deploying releases, in particular, of firmware.
- unless some care is taken, it poses a denial-of-service risk to innocent third-party users of locked machines.
- (people willing to unlock their machines with a devkey or to maintain their own customized firmware suffer little additional risk.)
Proposal 2
your proposal here...
