chrony-fips

packaged by Chainguard

Chainguard Container for chrony-fips

Minimalist Wolfi-based FIPS image for chrony, an NTP client and server (chronyd and chronyc) with OpenSSL FIPS CMAC authentication.

Chainguard Containers are regularly-updated, secure-by-default container images.

Download this Container Image

For those with access, this container image is available on cgr.dev:

docker pull cgr.dev/ORGANIZATION/chrony-fips:latest

Be sure to replace the ORGANIZATION placeholder with the name used for your organization's private repository within the Chainguard Registry.

Compatibility Notes

This image provides a FIPS build of chrony, an implementation of the Network Time Protocol (NTP) written in C and licensed under the GNU General Public License v2.0. It tracks upstream chrony 4.9 and ships both chronyd (the daemon) and chronyc (the command-line control client).

The entrypoint is /usr/bin/chronyd with the default argument -d, which keeps the daemon in the foreground and logs to standard error. The default configuration file is /etc/chrony/chrony.conf.

The container starts as root because chronyd needs privileges to adjust the system clock and bind to port 123. After initialization, chronyd drops privileges to the chrony user (UID 65532). The state directory /var/lib/chrony is owned by that user; any volume mounted there must be writable by UID 65532.

FIPS Support

This build of chrony performs symmetric-key NTP authentication with AES-CMAC through the OpenSSL FIPS provider, and the image ships openssl-config-fipshardened. chronyd -v reports +OPENSSL_FIPS. Only AES128 and AES256 (CMAC) keys are accepted; legacy hash-based keys such as MD5 or SHA256 are rejected, and chronyc keygen produces AES-CMAC keys by default. NTS is not available in this image (-NTS -SECHASH), because chrony's NTS implementation relies on GnuTLS and SIV algorithms that the FIPS provider does not supply. No other crypto library (GnuTLS, Nettle, NSS, LibTomCrypt) is linked.

Getting Started

To run chronyd as an NTP client that disciplines the host clock, grant the SYS_TIME capability:

docker run -d --name chronyd \
  --cap-add SYS_TIME \
  cgr.dev/ORGANIZATION/chrony-fips:latest

To use your own configuration, mount it over the default and pass any arguments you need. Passing arguments replaces the default -d, so include it:

cat > chrony.conf <<'EOF'
pool pool.ntp.org iburst
driftfile /var/lib/chrony/drift
makestep 1.0 3
EOF

docker run -d --name chronyd \
  --cap-add SYS_TIME \
  -v "$PWD/chrony.conf:/etc/chrony/chrony.conf:ro" \
  cgr.dev/ORGANIZATION/chrony-fips:latest -d -f /etc/chrony/chrony.conf

To authenticate a server with a FIPS-approved AES-CMAC key, reference a key file with keyfile and add key <id> to the server directive. Keys use the form <id> AES128 HEX:<32 hex digits>.

To run without modifying the system clock (for example, to serve time only or for testing), add -x:

docker run -d --name chronyd cgr.dev/ORGANIZATION/chrony-fips:latest -d -x

To query the running daemon with chronyc:

docker exec chronyd chronyc tracking
docker exec chronyd chronyc sources -v

Configuration

Exposed ports

• 123/udp: NTP, when serving time to clients (requires an allow directive)
• 323/udp: chronyc command port on localhost

Volumes

• /var/lib/chrony: drift file and other persistent state. It must be writable by the chrony user (UID 65532).

Documentation and Resources

• chrony documentation
• chrony.conf reference
• chrony source

What are Chainguard Containers?

Chainguard's free tier of Starter container images are built with Wolfi, our minimal Linux undistro.

All other Chainguard Containers are built with Chainguard OS, Chainguard's minimal Linux operating system designed to produce container images that meet the requirements of a more secure software supply chain.

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• Minimal design, without unnecessary software bloat
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