Dev image ships with `debug-tweaks` (empty root password, SSH root access)

[pbeza]

The dev image recipe in meta-dstack/recipes-core/images/dstack-rootfs-dev.inc includes Yocto's debug-tweaks feature, which sets an empty root password and enables SSH root access, creating a remotely exploitable backdoor if the dev image is deployed to production.

Root Cause

The dev image recipe includes Yocto's debug-tweaks feature:

# dstack-rootfs-dev.inc:3-4
IMAGE_INSTALL += "packagegroup-core-ssh-openssh strace tcpdump gdb gdbserver vim"
EXTRA_IMAGE_FEATURES += "debug-tweaks tools-profile"

debug-tweaks enables:

• Empty root password (allows passwordless root login)
• SSH root access without key authentication
• Post-install script execution

The production image correctly uses nologin and does not include debug-tweaks.

Attack Path

1. Operator accidentally deploys the dev image instead of the production image in a production environment
2. The CVM has an empty root password and SSH access
3. Any process or network-connected attacker can log in as root without credentials
4. Root access gives full control over all CVM contents including keyshares and private keys
5. Note: TDX attestation would detect the wrong image (different measurements), but only if the verifier checks the image measurements

Impact

If the dev image is accidentally deployed in production, the CVM has no authentication boundary. The risk is operational — it depends on deploying the correct image. The production image is correctly hardened.

Suggested Fix

1. Add a build-time safety check that prevents dev images from being pushed to production registries
2. Add a runtime check in the node that verifies it's running on a production image (e.g., check for the absence of debug-tweaks indicators)
3. Consider using distinct image names that make accidental substitution obvious (e.g., dstack-rootfs-dev-DO-NOT-DEPLOY-TO-PROD)

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Note: This issue was created automatically. The vulnerability report was generated by Claude and has not been verified by a human.

[kvinwang]

This has already been addressed. SSH password authentication is disabled for all images (including dev) via an openssh bbappend that installs sshd_config.d/disable-password-auth.conf:

PasswordAuthentication no
PermitEmptyPasswords no
KbdInteractiveAuthentication no
PermitRootLogin prohibit-password

See commit c195dc6. Even though debug-tweaks sets an empty root password, SSH only accepts public key authentication. Local console login with an empty password is acceptable for a dev image — that's its intended use case.