CWE-1304: Improperly Preserved Integrity of Hardware Configuration State During a Power Save/Restore Operation

How it's found

Improperly Preserved Integrity of Hardware Configuration State During a Power Save/Restore Operation is typically found by tracing untrusted input from where it enters the system to the point where it is used without the check or neutralization this weakness describes, combining manual code review with dynamic testing.

Before powering down, the Intellectual Property (IP) saves current state (S) to persistent storage such as flash or always-on memory in order to optimize the restore operation. During this process, an attacker with access to the persistent storage may alter (S) to a configuration that could potentially modify privileges, disable protections, and/or cause damage to the hardware. If the IP does not validate the configuration state stored in persistent memory, upon regaining power or becoming operational again, the IP could be compromised through the activation of an unwanted/harmful configuration.

Vulnerable vs. safe

void* cfg;cfg = get_config_state();save_config_state(cfg);go_to_sleep();

void* cfg;cfg = get_config_file();load_config_file(cfg);void save_config_state(){}void restore_config_state(){}

void* cfg;void* sha;cfg = get_config_state();save_config_state(cfg);// save hash(cfg) to trusted locationsha = get_hash_of_config_state(cfg);save_hash(sha);go_to_sleep();

assert_error_and_halt();void* cfg;void* sha_1, sha_2;cfg = get_config_file();// restore hash of config from trusted memorysha_1 = get_persisted_sha_value();sha_2 = get_hash_of_config_state(cfg);if (sha_1 != sha_2)load_config_file(cfg);void save_config_state(){}void restore_config_state(){}

Consequences

• DoS: Instability, DoS: Crash, Exit, or Restart, DoS: Resource Consumption (Other), Gain Privileges or Assume Identity, Bypass Protection Mechanism, Alter Execution Logic, Quality Degradation, Unexpected State, Reduce Maintainability, Reduce Performance, Reduce Reliability

Mitigations

• Architecture and Design: Inside the IP, incorporate integrity checking on the configuration state via a cryptographic hash. The hash can be protected inside the IP such as by storing it in internal registers which never lose power. Before powering down, the IP performs a hash of the configuration and saves it in these persistent registers. Upon restore, the IP performs a hash of the saved configuration and compares it with the saved hash. If they do not match, then the IP should not trust the configuration.
• Integration: Outside the IP, incorporate integrity checking of the configuration state via a trusted agent. Before powering down, the trusted agent performs a hash of the configuration and saves the hash in persistent storage. Upon restore, the IP requests the trusted agent validate its current configuration. If the configuration hash is invalid, then the IP should not trust the configuration.
• Integration: Outside the IP, incorporate a protected environment that prevents undetected modification of the configuration state by untrusted agents. Before powering down, a trusted agent saves the IP's configuration state in this protected location that only it is privileged to. Upon restore, the trusted agent loads the saved state into the IP.

Where this fits in a TurboPentest engagement

This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.

Frequently asked questions

Related CWEs

• Pillar weakness
  CWE-284: Improper Access Control
• Class weakness
  CWE-345: Insufficient Verification of Data Authenticity
• Base weakness
  CWE-1271: Uninitialized Value on Reset for Registers Holding Security Settings