ntpsec-rs-d-0.3.48 is not a library.

ntpsec-rs-d — ntpd-rs

Full NTP daemon binary — a drop-in replacement for ntpd from NTPsec.

Part of the ntpsec-rs workspace — a forensic Rust reconstruction of NTPsec. Version 0.3.48.

Overview

ntpd-rs is a complete Network Time Protocol daemon that synchronizes the system clock to remote NTP servers and/or reference clocks. It is designed as a drop-in replacement for the ntpd daemon from NTPsec, with compatible command line flags, configuration file format, drift file format, and statistics files.

Architecture

┌────────────────────────────────────────────────────────────────┐
│                      ntpd-rs Event Loop                         │
│                                                                 │
│  ┌──────────┐   ┌──────────┐   ┌──────────┐   ┌──────────────┐ │
│  │ Peer     │   │ Network  │   │ Clock    │   │ State        │ │
│  │ Manager  │──▶│ I/O      │──▶│Discipline│──▶│ Store        │ │
│  │          │   │ (epoll)  │   │ (PLL/FLL)│   │ (drift file) │ │
│  └──────────┘   └──────────┘   └──────────┘   └──────────────┘ │
│       │              │               │                          │
│       ▼              ▼               ▼                          │
│  ┌──────────┐   ┌──────────┐   ┌──────────────┐                │
│  │ DNS      │   │ Kernel   │   │ Privilege    │                │
│  │ Resolver │   │Timestamps│   │ + Seccomp    │                │
│  └──────────┘   └──────────┘   └──────────────┘                │
└────────────────────────────────────────────────────────────────┘

Peer Management

The daemon manages a set of configured peers (from ntp.conf). Each peer is polled at an adaptive interval, and incoming server responses are processed through:

Authentication verification — If the peer is configured with a key ID, the response's MAC is verified using MD5, SHA-1, SHA-256/384/512, or AES-CMAC.
NTS validation — If NTS is negotiated, extension fields are validated and cookies are processed.
Clock filter — The most recent offset/delay samples are stored in a shift-register filter. The peer's offset is the sample with minimum delay.
Selection algorithm — Intersection and clustering algorithms identify falsetickers and select the best clock source.
Combining — The offsets of selected peers are combined into a weighted average.

Clock Discipline

The daemon's clock discipline uses a hybrid PLL/FLL (Phase-Locked Loop / Frequency-Locked Loop):

Initial synchronization — Large offsets (>128 ms) trigger a step correction using settimeofday.
Ongoing tracking — Small offsets are corrected by slewing the clock via adjtimex (Linux) or ntp_adjtime (BSD).
Frequency drift — The frequency offset (PPM) is tracked and periodically saved to the drift file for recovery across daemon restarts.

Event Loop

The main event loop uses epoll (Linux) to multiplex:

NTP client/server packet reception
NTS-KE connection events
Timer expirations (peer poll intervals, system polls)
Signal handling (SIGINT, SIGTERM, SIGHUP, SIGUSR1)
Mode 6 control queries from ntpq-rs, ntpmon-rs, and ntptrace-rs

Command-Line Flags

ntpd-rs supports flags compatible with NTPsec's ntpd:

Flag	Description
`-c <file>`	Specify configuration file (default: `/etc/ntp.conf`)
`-n`	No fork — run in the foreground
`-I <addr>`	Bind to specific interface address
`-4`	IPv4 only
`-6`	IPv6 only
`-u <user>`	Drop privileges to this user after startup
`-p <pidfile>`	Write PID to this file
`-l <logfile>`	Log output to this file
`-i <jaildir>`	chroot jail directory
`-k <keyfile>`	Specify authentication key file
`--trustedkey <id>`	Mark a key as trusted
`--driftfile <file>`	Drift file path
`--slew`	Always slew, never step
`--panicgate`	Force initial step (ignore panic threshold)
`--wait-sync`	Wait for initial synchronization before exiting
`--nice <level>`	Set nice priority level
`--trace`	Enable protocol trace
`--seccomp`	Enable seccomp BPF sandboxing

Usage Examples

Start the daemon in the background with default settings:

ntpd-rs

Run in the foreground with a custom config:

ntpd-rs -n -c /etc/ntp/my-ntp.conf

Force IPv4 and log to a file:

ntpd-rs -4 -l /var/log/ntp.log

Drop privileges and use seccomp:

ntpd-rs -u ntp --seccomp

Privilege Dropping

On Linux, the daemon drops privileges after binding sockets and opening required files, using the following sequence:

Bind UDP sockets on port 123 (requires CAP_NET_BIND_SERVICE).
Open drift file, log file, and PID file.
Call prctl(PR_SET_KEEPCAPS, 1) to retain capabilities.
Set the user/group to the specified unprivileged user (e.g., ntp).
Apply cap_set_proc to reduce the capability set to only what's needed:
- CAP_SYS_TIME — For clock adjustment (adjtimex, settimeofday)
- CAP_NET_BIND_SERVICE — Already used, dropped after bind
- CAP_SYS_RESOURCE — For setpriority/nice
- CAP_SYS_CHROOT — For --jaildir support

Seccomp BPF Sandbox

When --seccomp is enabled, the daemon installs a BPF seccomp filter after initialization that restricts allowed system calls to a minimal whitelist:

Allowed Syscall Group	Purpose
`read`, `write`, `recvmsg`, `sendto`	Network I/O
`clock_gettime`, `adjtimex`, `gettimeofday`	Clock operations
`epoll_wait`, `epoll_ctl`	Event loop
`nanosleep`	Timer waits
`sigaction`, `sigreturn`, `rt_sigprocmask`	Signal handling
`mmap`, `munmap`, `brk`, `mprotect`	Memory management
`exit_group`, `exit`	Process termination

Any unexpected syscall causes immediate process termination with SIGSYS, providing strong protection against kernel-level exploits.

Daemon Binary Court

ntpd-rs operates on the court principle: every mutation of daemon state is tracked and can be reproduced for verification. The daemon binary spawns the actual ntpsec-rs engine (DaemonEngine from ntpsec-rs-core) and communicates with it through a well-defined interface. Mode 6 queries to the daemon are validated against known-answer tests from the court system.

See the court documentation for traceability evidence.

systemd Service Integration

An example systemd service unit:

[Unit]
Description=Network Time Service (ntpsec-rs)
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
ExecStart=/usr/sbin/ntpd-rs -n -u ntp
ExecReload=/bin/kill -HUP $MAINPID
Restart=on-failure
RestartSec=5
User=ntp
AmbientCapabilities=CAP_SYS_TIME CAP_NET_BIND_SERVICE
NoNewPrivileges=yes
PrivateDevices=yes
ProtectHome=yes
ProtectSystem=strict
ReadWritePaths=/var/lib/ntp /var/log/ntp

[Install]
WantedBy=multi-user.target

Drift File and Statistics Compatibility

ntpd-rs maintains NTPsec-compatible files:

Drift file (/var/lib/ntp/ntp.drift):

freq 3.1415

The frequency offset (in PPM) is saved every 15 minutes and on daemon shutdown, enabling recovery across restarts.

Statistics files (/var/log/ntp/):

loopstats — Clock discipline statistics (MJD, time, offset, drift, jitter)
peerstats — Per-peer statistics (MJD, time, src-addr, dst-addr, offset, delay, jitter)
clockstats — Reference clock driver statistics

These are plain-text, space-delimited files compatible with ntpviz-rs and the original NTPsec analysis tools.

Related Crates

All crates in the ntpsec-rs workspace on crates.io:

Crate	Description	crates.io
ntpsec-rs-core	Deterministic engine, wire codec, Mode 6, auth, refclocks, NTS
ntpsec-rs-io	Real I/O layer (system clock, network, state store)
ntpsec-rs	Umbrella facade crate
ntpsec-rs-d	ntpd-rs — NTP daemon binary
ntpsec-rs-query	ntpq-rs — Mode 6 query client
ntpsec-rs-dig	ntpdig-rs — NTP query tool
ntpsec-rs-keygen	NTP key generation
ntpsec-rs-leapfetch	Leap second file fetcher
ntpsec-rs-mon	Real-time NTP monitoring tool
ntpsec-rs-trace	NTP path trace tool
ntpsec-rs-wait	Wait until NTP server reachable
ntpsec-rs-viz	NTP data visualization
ntpsec-rs-frob	NTP configuration manipulator
ntpsec-rs-snmpd	SNMP monitoring daemon
ntpsec-rs-time	Single-shot time query tool
ntpsec-rs-sweep	Sweep through servers collecting stats
ntpsec-rs-loggps	GPS reference clock logging
ntpsec-rs-logtemp	System temperature logging