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
tuminoid Reporter
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, modifyconfig.dev.yamlto run on https, using generated certs.Run dex
bin/dex serve config.dev.yaml.Install
sslyze, easy to use SSL connection analyzer: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.
In Dex 2.36.0, TLS 1.0 and TLS 1.1 are disabled as expected.
Impact
TLS 1.0 and TLS 1.1 connections can be decrypted by the attacker, and hence decrypt the traffic to Dex.
References