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DKER-EE-001830 - The userland proxy capability in the Docker Engine - Enterprise component of Docker Enterprise must be disabled.

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Information

The docker daemon starts a userland proxy service for port forwarding whenever a port is exposed. Where hairpin NAT is available, this service is generally superfluous to requirements and can be disabled. Docker engine provides two mechanisms for forwarding ports from the host to containers, hairpin NAT, and a userland proxy. In most circumstances, the hairpin NAT mode is preferred as it improves performance and makes use of native Linux iptables functionality instead of an additional component. Where hairpin NAT is available, the userland proxy should be disabled on startup to reduce the attack surface of the installation.

Docker Enterprise includes the following capabilities that are considered non-essential:

*NOTE: disabling these capabilities negatively affects the operation of Universal Control Plane (UCP) and Docker Trusted Registry (DTR) and should be disregarded when UCP and DTR are installed. The security capabilities provided by UCP and DTR offset any potential vulnerabilities associated with not disabling these essential capabilities the Engine provides.

(Docker Engine - Enterprise: Standalone) - The majority of these items were originally identified as part of the CIS Docker Benchmark, which as of the CIS Docker Benchmark v1.2.0, are still applicable to Docker Engine - Enterprise 18.09
- inter-container communication (icc)* (CIS Docker Benchmark Recommendation 2.1)
- insecure registry communication (CIS Docker Benchmark Recommendation 2.4)
- AUFS storage driver (applicable on Linux only) (CIS Docker Benchmark Recommendation 2.5)
- listening on the TCP Daemon socket
- userland proxy for loopback traffic* (CIS Docker Benchmark Recommendation 2.15)
- experimental features (CIS Docker Benchmark Recommendation 2.17)
- Swarm Mode (CIS Docker Benchmark Recommendation 7.1)

(Docker Engine - Enterprise: As part of a UCP cluster)
- insecure registry communication (CIS Docker Benchmark Recommendation 2.4)
- AUFS storage driver (applicable on Linux only) (CIS Docker Benchmark Recommendation 2.5)
- listening on the TCP Daemon socket
- experimental features (CIS Docker Benchmark Recommendation 2.17)

(UCP)
- Managed user database
- self-signed certificates
- periodic usage reporting and API tracking
- allow users and administrators to schedule containers on all nodes, including UCP managers and DTR nodes

(DTR)
- periodic data usage/analytics reporting
- create repository on push
- self-signed certificates

Solution

This fix only applies to the Docker Engine - Enterprise component of Docker Enterprise and only when it is not being operated as part of a UCP cluster.

via CLI:

Linux: As a trusted user on the underlying host operating system, edit the '/etc/docker/daemon.json' file and set the 'userland-proxy' property to a value of 'false'.

Restart the Docker daemon.

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Docker_Enterprise_2-x_Linux-UNIX_V2R1_STIG.zip

Item Details

References: CAT|II, CCI|CCI-000381, Rule-ID|SV-235791r627500_rule, STIG-ID|DKER-EE-001830, STIG-Legacy|SV-104753, STIG-Legacy|V-95615, Vuln-ID|V-235791

Plugin: Unix

Control ID: ae8ed04513a1954fdf1700842af36ac2cba503a76e6b650ca41bd30606cd42fc