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CRITICAL

Misuse of connection.serverAuthenticate may cause authorization bypass in golang.org/x/crypto

Published Dec 11, 2024

Description

Applications and libraries which misuse connection.serverAuthenticate (via callback field ServerConfig.PublicKeyCallback) may be susceptible to an authorization bypass. The documentation for ServerConfig.PublicKeyCallback says that "A call to this function does not guarantee that the key offered is in fact used to authenticate." Specifically, the SSH protocol allows clients to inquire about whether a public key is acceptable before proving control of the corresponding private key. PublicKeyCallback may be called with multiple keys, and the order in which the keys were provided cannot be used to infer which key the client successfully authenticated with, if any. Some applications, which store the key(s) passed to PublicKeyCallback (or derived information) and make security relevant determinations based on it once the connection is established, may make incorrect assumptions. For example, an attacker may send public keys A and B, and then authenticate with A. PublicKeyCallback would be called only twice, first with A and then with B. A vulnerable application may then make authorization decisions based on key B for which the attacker does not actually control the private key. Since this API is widely misused, as a partial mitigation golang.org/x/cry...@v0.31.0 enforces the property that, when successfully authenticating via public key, the last key passed to ServerConfig.PublicKeyCallback will be the key used to authenticate the connection. PublicKeyCallback will now be called multiple times with the same key, if necessary. Note that the client may still not control the last key passed to PublicKeyCallback if the connection is then authenticated with a different method, such as PasswordCallback, KeyboardInteractiveCallback, or NoClientAuth. Users should be using the Extensions field of the Permissions return value from the various authentication callbacks to record data associated with the authentication attempt instead of referencing external state. Once the connection is established the state corresponding to the successful authentication attempt can be retrieved via the ServerConn.Permissions field. Note that some third-party libraries misuse the Permissions type by sharing it across authentication attempts; users of third-party libraries should refer to the relevant projects for guidance.

Affected products

Remediation

Red Hat statement

This vulnerability is classified as important rather than critical because it does not directly enable unauthorized access but rather introduces a risk of authorization bypass if the application or library misuses the PublicKeyCallback API. The vulnerability relies on incorrect assumptions made by the application when handling the sequence or state of keys provided during SSH authentication. Properly implemented systems that use the Permissions field or avoid relying on external state remain unaffected. Additionally, the vulnerability does not allow direct exploitation to gain control over a system without the presence of insecure logic in the application's handling of authentication attempts. Red Hat Enterprise Linux(RHEL) 8 & 9 and Red Hat Openshift marked as not affected as it was determined that the problem function `ServerConfig.PublicKeyCallback`, as noted in the CVE-2024-45337 issue, is not called by Podman, Buildah, containers-common, or the gvisor-tap-vsock projects.

Weaknesses (1)

CWE-285

References (13)

Change history (0)

No recorded changes yet.

Sources

CVE.org / MITRE

Status PUBLISHED
Assigner Go
Published Dec 11, 2024
Updated Feb 18, 2025
Reserved Aug 27, 2024
Link CVE-2024-45337

CISA Vulnrichment

Updated Dec 12, 2024

NVD

Status Deferred
Modified Jun 17, 2026
Link CVE-2024-45337

Red Hat

Severity Important
Public date Dec 11, 2024
Bugzilla 2331720
Link CVE-2024-45337

ENISA EUVD

Assigner Go
Published Dec 11, 2024
Updated Feb 18, 2025
Link EUVD-2024-3508

GitHub

Link GHSA-V778-237X-GJRC