Security hardening: erase LDevID root keys before ROM→FMC handoff

[Copilot]

LDevID private keys (ECC and MLDSA) were left in the Key Vault when ROM handed control to FMC, exposing them to ROM glitch attacks where an attacker causes ROM to skip verification and jump to FMC with root keys still accessible.

Changes

• rom/dev/src/main.rs — In launch_fmc(), erase KEY_ID_LDEVID_ECDSA_PRIV_KEY (KeyId5) and KEY_ID_LDEVID_MLDSA_KEYPAIR_SEED (KeyId4) from the Key Vault immediately before transferring control to FMC. Any erasure failure triggers a fatal error.

// Erase LDevID private keys before launching FMC.
// These root keys must not be accessible to FMC or later firmware stages,
// protecting against ROM glitch attacks.
if let Err(e) = env.key_vault.erase_key(KEY_ID_LDEVID_ECDSA_PRIV_KEY) {
    handle_fatal_error(e.into());
}
if let Err(e) = env.key_vault.erase_key(KEY_ID_LDEVID_MLDSA_KEYPAIR_SEED) {
    handle_fatal_error(e.into());
}

Notes

• Erasure runs on all reset types (cold/warm/update). After the first cold boot the slots are already empty on subsequent boots, so the call is idempotent.
• FMC→RT transition (FMC CDI KeyId6, ECC KeyId7, MLDSA KeyId8): the existing set_key_use_lock() approach is preserved. Erasing these keys before RT runs would break firmware update reset—FMC must re-sign the RT alias certificate on each update reset using the same cold-boot-derived keys, which are restored when the hardware clears USE_LOCK on reset. A proper erasure-based solution here requires ROM to re-derive FMC keys on update reset and is a separate effort.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/benjamindoron/byteorder/commits/struct_aware-1.4.3
  • Triggering command: /home/REDACTED/.rustup/toolchains/1.85-x86_64-REDACTED-linux-gnu/bin/cargo /home/REDACTED/.rustup/toolchains/1.85-x86_64-REDACTED-linux-gnu/bin/cargo metadata --format-version 1 --all-features --manifest-path /home/REDACTED/work/caliptra-sw/caliptra-sw/image/verify/fuzz/Cargo.toml --filter-platform x86_64-REDACTED-linux-gnu --lockfile-path /tmp/rust-analyzerdd3e-6/Cargo.lock -Zunstable-options n/ru�� tests-085d826a63debuginfo=2 tests-085d826a63--cfg /debug/build/calfeature="arbitrary" /debug/build/calgit /debug/build/calrev-parse /debug/build/calHEAD /debug/build/calfeature="default" (http block)
  • Triggering command: /home/REDACTED/.rustup/toolchains/1.85-x86_64-REDACTED-linux-gnu/bin/cargo /home/REDACTED/.rustup/toolchains/1.85-x86_64-REDACTED-linux-gnu/bin/cargo check --quiet --workspace --message-format=json --manifest-path /home/REDACTED/work/caliptra-sw/caliptra-sw/image/verify/fuzz/Cargo.toml --target-dir /tmp/codeql-scratch-dcfb536374eacc37/dbs/rust/working/target --lockfile-path /tmp/rust-analyzerdd3e-8/Cargo.lock --all-features --keep-going -Zunstable-options /debug/deps/caliptra_fmc-6889d70/home/REDACTED/work/caliptra-sw/caliptra-sw/target/debug/deps/rom_- own-linux-gnu/bin/rustc /debug/deps/caligit /debug/deps/calirev-parse /debug/deps/caliHEAD own-linux-gnu/bin/rustc (http block)
  • Triggering command: /home/REDACTED/.rustup/toolchains/1.85-x86_64-REDACTED-linux-gnu/bin/cargo /home/REDACTED/.rustup/toolchains/1.85-x86_64-REDACTED-linux-gnu/bin/cargo metadata --format-version 1 --all-features --manifest-path /home/REDACTED/work/caliptra-sw/caliptra-sw/drivers/fuzz/Cargo.toml --filter-platform x86_64-REDACTED-linux-gnu --lockfile-path /tmp/rust-analyzerdd3e-2f/Cargo.lock -Zunstable-options rev-�� HEAD git ndor/bin/git HEAD inux-gnu /usr/bin/git git (http block)
• https://api.github.com/repos/benjamindoron/zerocopy/commits/struct_aware-v0.6.3
  • Triggering command: REDACTED, pid is -1 (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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