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GHSA-h929-fvvp-882c
No affected components available
Duplicate Advisory
This advisory has been withdrawn because it is a duplicate of GHSA-wc42-fcjp-v8vq. This link is maintained to preserve external references.
Original Description
Vault Key Sealed With SHA1 PCRs
The measured boot solution implemented in EVE OS leans on a PCR locking mechanism.
Different parts of the system update different PCR values in the TPM, resulting in a unique value for each PCR entry.
These PCRs are then used in order to seal/unseal a key from the TPM which is used to encrypt/decrypt the “vault” directory.
This “vault” directory is the most sensitive point in the system and as such, its content should be protected.
This mechanism is noted in Zededa’s documentation as the “measured boot” mechanism, designed to protect said “vault”.
The code that’s responsible for generating and fetching the key from the TPM assumes that SHA256 PCRs are used in order to seal/unseal the key, and as such their presence is being checked.
The issue here is that the key is not sealed using SHA256 PCRs, but using SHA1 PCRs. This leads to several issues:
• Machines that have their SHA256 PCRs enabled but SHA1 PCRs disabled, as well as not sealing their keys at all, meaning the “vault” is not protected from an attacker.
• SHA1 is considered insecure and reduces the complexity level required to unseal the key in machines which have their SHA1 PCRs enabled.
An attacker can very easily retrieve the contents of the “vault”, which will effectively render the “measured boot” mechanism meaningless.
The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
Probability that this vulnerability will be exploited in the wild within the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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