CVE-2023-38201: Keylime: challenge-response protocol bypass during agent registration
First published: Thu Jul 13 2023(Updated: )
### Impact A security issue was found in the Keylime `registrar` code which allows an attacker to effectively bypass the challenge-response protocol used to verify that an `agent` has indeed access to an AIK which in indeed related to the EK. When an `agent` starts up, it will contact a `registrar` and provide a public EK and public AIK, in addition to the EK Certificate. This `registrar` will then challenge the `agent` to decrypt a challenge encrypted with the EK. When receiving the wrong "auth_tag" back from the `agent` during activation, the `registrar` answers with an error message that contains the expected correct "auth_tag" (an HMAC which is calculated within the `registrar` for checking). An attacker could simply record the correct expected "auth_tag" from the HTTP error message and perform the activate call again with the correct expected "auth_tag" for the `agent`. The security issue allows an attacker to pass the challenge-response protocol during registration with (almost) arbitrary registration data. In particular, the attacker can provide a valid EK Certificate and EK, which passes verification by the `tenant` (or `registrar`), while using a compromised AIK, which is stored unprotected outside the TPM and is unrelated to former two. The attacker then deliberately fails the initial activation call to get to know the correct "auth_tag" and then provides it in a subsequent activation call. This results in an `agent` which is (incorrectly) registered with a valid EK Certificate, but with a compromised/unrelated AIK. ### Patches Users should upgrade to release 7.5.0
Credit: secalert@redhat.com secalert@redhat.com secalert@redhat.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| pip/keylime | <7.5.0 | 7.5.0 |
| Keylime Keylime | <7.5.0 | |
| Redhat Enterprise Linux | =9.0 | |
| Redhat Enterprise Linux Eus | =9.2 | |
| Redhat Enterprise Linux For Ibm Z Systems | =9.0_s390x | |
| Redhat Enterprise Linux For Ibm Z Systems Eus | =9.2_s390x | |
| Redhat Enterprise Linux For Power Little Endian | =9.0_ppc64le | |
| Redhat Enterprise Linux For Power Little Endian Eus | =9.2_ppc64le | |
| Redhat Enterprise Linux Server Aus | =9.2 | |
| Fedoraproject Fedora | =38 | |
| redhat/keylime | <7.5.0 | 7.5.0 |
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Reference Links
- https://github.com/keylime/keylime/security/advisories/GHSA-f4r5-q63f-gcww
- https://nvd.nist.gov/vuln/detail/CVE-2023-38201
- https://github.com/keylime/keylime/commit/9e5ac9f25cd400b16d5969f531cee28290543f2a
- https://access.redhat.com/security/cve/CVE-2023-38201
- https://bugzilla.redhat.com/show_bug.cgi?id=2222693
- https://github.com/pypa/advisory-database/tree/main/vulns/keylime/PYSEC-2023-160.yaml
- https://access.redhat.com/errata/RHSA-2023:5080
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZIZZB5NHNCS5D2AEH3ZAO6OQC72IK7WS/
- https://github.com/advisories/GHSA-f4r5-q63f-gcww (Advisory)
- https://github.com/keylime/keylime/releases/tag/v7.5.0
Frequently Asked Questions
What is CVE-2023-38201?
CVE-2023-38201 is a vulnerability found in the Keylime registrar code that allows an attacker to bypass the challenge-response protocol used to verify an agent's access to an AIK.
How does CVE-2023-38201 impact Keylime?
CVE-2023-38201 impacts Keylime by allowing an attacker to effectively bypass the challenge-response protocol used for verifying an agent's access to an AIK.
What is the severity of CVE-2023-38201?
The severity of CVE-2023-38201 is medium, with a severity value of 6.5.
What software versions are affected by CVE-2023-38201?
Keylime versions up to and excluding 7.5.0, as well as Redhat Enterprise Linux 9.0, are affected by CVE-2023-38201.
How can I fix CVE-2023-38201?
To fix CVE-2023-38201, update Keylime to version 7.5.0 or newer.
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