Linuxfoundation: Security Vulnerabilities
In EVE OS, the “measured boot” mechanism prevents a compromised device from accessing
the encrypted data located in the vault.
As per the “measured boot” design, the PCR values calculated at different stages of the boot
process will change if any of their respective parts are changed.
This includes, among other things, the configuration of the bios, grub, the kernel cmdline,
initrd, and more.
However, this mechanism does not validate the entire rootfs, so an attacker can edit the
filesystem and gain control over the system.
As the default filesystem used by EVE OS is squashfs, this is somewhat harder than an ext4,
which is easily changeable.
This will not stop an attacker, as an attacker can repackage the squashfs with their changes
in it and replace the partition altogether.
This can also be done directly on the device, as the “003-storage-init” container contains the
“mksquashfs” and “unsquashfs” binaries (with the corresponding libs).
An attacker can gain full control over the device without changing the PCR values, thus not
triggering the “measured boot” mechanism, and having full access to the vault.
Note:
This issue was partially fixed in these commits (after disclosure to Zededa), where the config
partition measurement was added to PCR13:
• aa3501d6c57206ced222c33aea15a9169d629141
• 5fef4d92e75838cc78010edaed5247dfbdae1889.
This issue was made viable in version 9.0.0 when the calculation was moved to PCR14 but it was not included in the measured boot.
CVSS Score
8.8
EPSS Score
0.0
Published
2023-09-20
PCR14 is not in the list of PCRs that seal/unseal the “vault” key, but
due to the change that was implemented in commit
“7638364bc0acf8b5c481b5ce5fea11ad44ad7fd4”, fixing this issue alone would not solve the
problem of the config partition not being measured correctly.
Also, the “vault” key is sealed/unsealed with SHA1 PCRs instead of
SHA256.
This issue was somewhat mitigated due to all of the PCR extend functions
updating both the values of SHA256 and SHA1 for a given PCR ID.
However, due to the change that was implemented in commit
“7638364bc0acf8b5c481b5ce5fea11ad44ad7fd4”, this is no longer the case for PCR14, as
the code in “measurefs.go” explicitly updates only the SHA256 instance of PCR14, which
means that even if PCR14 were to be added to the list of PCRs sealing/unsealing the “vault”
key, changes to the config partition would still not be measured.
An attacker could modify the config partition without triggering the measured boot, this could
result in the attacker gaining full control over the device with full access to the contents of the
encrypted “vault”
CVSS Score
8.8
EPSS Score
0.0
Published
2023-09-20
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.
CVSS Score
8.8
EPSS Score
0.0
Published
2023-09-20
NATS nats-server 2.2.0 through 2.7.4 allows directory traversal because of an unintended path to a management action from a management account.
CVSS Score
9.8
EPSS Score
0.002
Published
2023-09-19
In bluetooth driver, there is a possible out of bounds read due to improper input validation. This could lead to local information leak with System execution privileges needed. User interaction is not needed for exploitation. Patch ID: ALPS07867212; Issue ID: ALPS07867212.
CVSS Score
4.4
EPSS Score
0.0
Published
2023-09-04
In connectivity system driver, there is a possible out of bounds write due to improper input validation. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation. Patch ID: ALPS07929848; Issue ID: ALPS07929848.
CVSS Score
6.7
EPSS Score
0.0
Published
2023-09-04
In gnss service, there is a possible out of bounds write due to improper input validation. This could lead to local esclation of privileges with System execution privileges needed. User interaction is not needed for exploitation. Patch ID: ALPS08017365; Issue ID: ALPS08017365.
CVSS Score
6.7
EPSS Score
0.0
Published
2023-09-04
In gnss service, there is a possible out of bounds write due to improper input validation. This could lead to local information disclosure with System execution privileges needed. User interaction is not needed for exploitation. Patch ID: ALPS08017370; Issue ID: ALPS08017370.
CVSS Score
4.4
EPSS Score
0.0
Published
2023-09-04
In gnss service, there is a possible out of bounds read due to improper input validation. This could lead to local information disclosure with System execution privileges needed. User interaction is not needed for exploitation. Patch ID: ALPS08037801; Issue ID: ALPS08037801.
CVSS Score
4.4
EPSS Score
0.0
Published
2023-09-04
In imgsys_cmdq, there is a possible out of bounds write due to a missing valid range checking. This could lead to local escalation of privilege with System execution privileges needed. User interaction is needed for exploitation. Patch ID: ALPS07340433; Issue ID: ALPS07340381.
CVSS Score
6.5
EPSS Score
0.0
Published
2023-09-04