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Dex 2.37.0 is discarding TLSconfig and always serves deprecated TLS 1.0/1.1 and insecure ciphers

High
sagikazarmark published GHSA-gr79-9v6v-gc9r Jan 25, 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 #2848 and implementing configurable TLS support, I noticed my changes did not have any effect in TLS config, so I started investigating.

dex/cmd/dex/serve.go

Line 425 in 70d7a2c

MinVersion: tls.VersionTLS12,
is seemingly setting TLS 1.2 as minimum version, but the whole tlsConfig is ignored after "TLS cert reloader" was introduced in #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.

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 v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVE ID

CVE-2024-23656

Weaknesses

Credits