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6d9ef22acd
Monitor the sysctl set by networkd for writes, if a sysctl is overwritten with a different value than the one we set, emit a warning. Writes are detected with an eBPF program attached as BPF_CGROUP_SYSCTL which reports the sysctl writes only in net/. The eBPF program only reports sysctl writes from a different cgroup than networkd. To do this, it uses the `bpf_current_task_under_cgroup_proto()` helper, which will be available allowed in BPF_CGROUP_SYSCTL from kernel 6.12[1]. Loading a BPF_CGROUP_SYSCTL program requires the CAP_SYS_ADMIN capability, so drop it just after the program load, whether it loads successfully or not. Writes are logged but permitted, in future the functionality can be extended to also deny writes to managed sysctls. [1] https://lore.kernel.org/bpf/20240819162805.78235-3-technoboy85@gmail.com/
70 lines
2.5 KiB
SYSTEMD
70 lines
2.5 KiB
SYSTEMD
# SPDX-License-Identifier: LGPL-2.1-or-later
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#
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# This file is part of systemd.
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#
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# systemd is free software; you can redistribute it and/or modify it
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# under the terms of the GNU Lesser General Public License as published by
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# the Free Software Foundation; either version 2.1 of the License, or
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# (at your option) any later version.
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[Unit]
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Description=Network Configuration
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Documentation=man:systemd-networkd.service(8)
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Documentation=man:org.freedesktop.network1(5)
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ConditionCapability=CAP_NET_ADMIN
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DefaultDependencies=no
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# systemd-udevd.service can be dropped once tuntap is moved to netlink
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After=systemd-networkd.socket systemd-udevd.service network-pre.target systemd-sysusers.service systemd-sysctl.service
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Before=network.target multi-user.target shutdown.target initrd-switch-root.target
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Conflicts=shutdown.target initrd-switch-root.target
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Wants=systemd-networkd.socket network.target systemd-networkd-persistent-storage.service
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[Service]
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AmbientCapabilities=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_NET_BROADCAST CAP_NET_RAW CAP_BPF CAP_SYS_ADMIN
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BusName=org.freedesktop.network1
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CapabilityBoundingSet=CAP_NET_ADMIN CAP_NET_BIND_SERVICE CAP_NET_BROADCAST CAP_NET_RAW CAP_BPF CAP_SYS_ADMIN
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DeviceAllow=char-* rw
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ExecStart=!!{{LIBEXECDIR}}/systemd-networkd
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FileDescriptorStoreMax=512
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ImportCredential=network.wireguard.*
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LockPersonality=yes
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MemoryDenyWriteExecute=yes
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NoNewPrivileges=yes
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ProtectProc=invisible
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ProtectClock=yes
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ProtectControlGroups=yes
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ProtectHome=yes
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ProtectKernelLogs=yes
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ProtectKernelModules=yes
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ProtectSystem=strict
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Restart=on-failure
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RestartKillSignal=SIGUSR2
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RestartSec=0
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RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6 AF_PACKET
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RestrictNamespaces=yes
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RestrictRealtime=yes
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RestrictSUIDSGID=yes
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RuntimeDirectory=systemd/netif
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RuntimeDirectoryPreserve=yes
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SystemCallArchitectures=native
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SystemCallErrorNumber=EPERM
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SystemCallFilter=@system-service bpf
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Type=notify-reload
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User=systemd-network
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{{SERVICE_WATCHDOG}}
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[Install]
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WantedBy=multi-user.target
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Also=systemd-networkd.socket
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Alias=dbus-org.freedesktop.network1.service
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# The output from this generator is used by udevd and networkd. Enable it by
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# default when enabling systemd-networkd.service.
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Also=systemd-network-generator.service
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# We want to enable systemd-networkd-wait-online.service whenever this service
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# is enabled. systemd-networkd-wait-online.service has
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# WantedBy=network-online.target, so enabling it only has an effect if
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# network-online.target itself is enabled or pulled in by some other unit.
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Also=systemd-networkd-wait-online.service
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