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Dex discarding TLSconfig and always serves deprecated TLS 1.0/1.1 and insecure ciphers

High severity GitHub Reviewed Published Jan 25, 2024 in dexidp/dex • Updated Aug 7, 2024

Package

gomod github.com/dexidp/dex (Go)

Affected versions

= 2.37.0

Patched versions

2.38.0

Description

Summary

Dex 2.37.0 is serving HTTPS with insecure TLS 1.0 and TLS 1.1.

Details

While working on dexidp/dex#2848 and implementing configurable TLS support, I noticed my changes did not have any effect in TLS config, so I started investigating.

https://github.com/dexidp/dex/blob/70d7a2c7c1bb2646b1a540e49616cbc39622fb83/cmd/dex/serve.go#L425 is seemingly setting TLS 1.2 as minimum version, but the whole tlsConfig is ignored after "TLS cert reloader" was introduced in dexidp/dex#2964. Configured cipher suites are not respected either, as seen on the output.

PoC

Build Dex, generate certs with gencert.sh, modify config.dev.yaml to run on https, using generated certs.

issuer: http://127.0.0.1:5556/dex

storage:
  type: sqlite3
  config:
    file: dex.db

web:
  https: 127.0.0.1:5556
  tlsCert: examples/k8s/ssl/cert.pem
  tlsKey: examples/k8s/ssl/key.pem

<rest as default>

Run dex bin/dex serve config.dev.yaml.

Install sslyze, easy to use SSL connection analyzer:

pip3 install sslyze
sslyze 127.0.0.1:5556

In Dex 2.37.0, TLS 1.0 and TLS 1.1 are enabled in addition to expected TLS 1.2 and TLS 1.3.

 * TLS 1.0 Cipher Suites:
     Attempted to connect using 80 cipher suites.

     The server accepted the following 6 cipher suites:
        TLS_RSA_WITH_AES_256_CBC_SHA                      256                      
        TLS_RSA_WITH_AES_128_CBC_SHA                      128                      
        TLS_RSA_WITH_3DES_EDE_CBC_SHA                     168                      
        TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA                256       ECDH: prime256v1 (256 bits)
        TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA                128       ECDH: prime256v1 (256 bits)
        TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA               168       ECDH: prime256v1 (256 bits)

     The group of cipher suites supported by the server has the following properties:
       Forward Secrecy                    OK - Supported
       Legacy RC4 Algorithm               OK - Not Supported


 * TLS 1.1 Cipher Suites:
     Attempted to connect using 80 cipher suites.

     The server accepted the following 6 cipher suites:
        TLS_RSA_WITH_AES_256_CBC_SHA                      256                      
        TLS_RSA_WITH_AES_128_CBC_SHA                      128                      
        TLS_RSA_WITH_3DES_EDE_CBC_SHA                     168                      
        TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA                256       ECDH: prime256v1 (256 bits)
        TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA                128       ECDH: prime256v1 (256 bits)
        TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA               168       ECDH: prime256v1 (256 bits)

     The group of cipher suites supported by the server has the following properties:
       Forward Secrecy                    OK - Supported
       Legacy RC4 Algorithm               OK - Not Supported


 * TLS 1.2 Cipher Suites:
     Attempted to connect using 156 cipher suites.

     The server accepted the following 11 cipher suites:
        TLS_RSA_WITH_AES_256_GCM_SHA384                   256                      
        TLS_RSA_WITH_AES_256_CBC_SHA                      256                      
        TLS_RSA_WITH_AES_128_GCM_SHA256                   128                      
        TLS_RSA_WITH_AES_128_CBC_SHA                      128                      
        TLS_RSA_WITH_3DES_EDE_CBC_SHA                     168                      
        TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256       256       ECDH: X25519 (253 bits)
        TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384             256       ECDH: prime256v1 (256 bits)
        TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA                256       ECDH: prime256v1 (256 bits)
        TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256             128       ECDH: prime256v1 (256 bits)
        TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA                128       ECDH: prime256v1 (256 bits)
        TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA               168       ECDH: prime256v1 (256 bits)

     The group of cipher suites supported by the server has the following properties:
       Forward Secrecy                    OK - Supported
       Legacy RC4 Algorithm               OK - Not Supported


 * TLS 1.3 Cipher Suites:
     Attempted to connect using 5 cipher suites.

     The server accepted the following 3 cipher suites:
        TLS_CHACHA20_POLY1305_SHA256                      256       ECDH: X25519 (253 bits)
        TLS_AES_256_GCM_SHA384                            256       ECDH: X25519 (253 bits)
        TLS_AES_128_GCM_SHA256                            128       ECDH: X25519 (253 bits)

In Dex 2.36.0, TLS 1.0 and TLS 1.1 are disabled as expected.

 * TLS 1.0 Cipher Suites:
     Attempted to connect using 80 cipher suites; the server rejected all cipher suites.

 * TLS 1.1 Cipher Suites:
     Attempted to connect using 80 cipher suites; the server rejected all cipher suites.

 * TLS 1.2 Cipher Suites:
     Attempted to connect using 156 cipher suites.

     The server accepted the following 5 cipher suites:
        TLS_RSA_WITH_AES_256_GCM_SHA384                   256                      
        TLS_RSA_WITH_AES_128_GCM_SHA256                   128                      
        TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256       256       ECDH: X25519 (253 bits)
        TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384             256       ECDH: prime256v1 (256 bits)
        TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256             128       ECDH: prime256v1 (256 bits)

     The group of cipher suites supported by the server has the following properties:
       Forward Secrecy                    OK - Supported
       Legacy RC4 Algorithm               OK - Not Supported


 * TLS 1.3 Cipher Suites:
     Attempted to connect using 5 cipher suites.

     The server accepted the following 3 cipher suites:
        TLS_CHACHA20_POLY1305_SHA256                      256       ECDH: X25519 (253 bits)
        TLS_AES_256_GCM_SHA384                            256       ECDH: X25519 (253 bits)

Impact

TLS 1.0 and TLS 1.1 connections can be decrypted by the attacker, and hence decrypt the traffic to Dex.

References

@sagikazarmark sagikazarmark published to dexidp/dex Jan 25, 2024
Published by the National Vulnerability Database Jan 25, 2024
Published to the GitHub Advisory Database Jan 26, 2024
Reviewed Jan 26, 2024
Last updated Aug 7, 2024

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

0.067%
(31st percentile)

Weaknesses

CVE ID

CVE-2024-23656

GHSA ID

GHSA-gr79-9v6v-gc9r

Source code

Credits

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