sudo: introduce nm-sudo D-Bus service
NetworkManager runs as root and has lots of capabilities.
We want to reduce the attach surface by dropping capabilities,
but there is a genuine need to do certain things.
For example, we currently require dac_override capability, to open
the unix socket of ovsdb. Most users wouldn't use OVS, so we should
find a way to not require that dac_override capability. The solution
is to have a separate, D-Bus activate service (nm-sudo), which
has the capability to open and provide the file descriptor.
For authentication, we only rely on D-Bus. We watch the name owner
of NetworkManager, and only accept requests from that service. We trust
D-Bus to get it right a request from that name owner is really coming
from NetworkManager. If we couldn't trust that, how could PolicyKit
or any authentication via D-Bus work? For testing, the user can set
NM_SUDO_NO_AUTH_FOR_TESTING=1.
https://bugzilla.redhat.com/show_bug.cgi?id=1921826
2021-07-18 08:53:43 +02:00
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[Unit]
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2021-07-26 17:34:05 +02:00
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Description=NetworkManager Sudo Helper
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sudo: introduce nm-sudo D-Bus service
NetworkManager runs as root and has lots of capabilities.
We want to reduce the attach surface by dropping capabilities,
but there is a genuine need to do certain things.
For example, we currently require dac_override capability, to open
the unix socket of ovsdb. Most users wouldn't use OVS, so we should
find a way to not require that dac_override capability. The solution
is to have a separate, D-Bus activate service (nm-sudo), which
has the capability to open and provide the file descriptor.
For authentication, we only rely on D-Bus. We watch the name owner
of NetworkManager, and only accept requests from that service. We trust
D-Bus to get it right a request from that name owner is really coming
from NetworkManager. If we couldn't trust that, how could PolicyKit
or any authentication via D-Bus work? For testing, the user can set
NM_SUDO_NO_AUTH_FOR_TESTING=1.
https://bugzilla.redhat.com/show_bug.cgi?id=1921826
2021-07-18 08:53:43 +02:00
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#
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# nm-sudo exists for privilege separation. It allows to run NetworkManager
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# without certain capabilities, and ask nm-sudo for special operations
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# where more privileges are required.
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#
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# While nm-sudo has privileges that NetworkManager has not, it does not
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# mean that itself should run totally unconstrained. On the contrary, it
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# also should only have permissions it requires.
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#
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# nm-sudo rejects all requests that come from any other than the name
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# owner of "org.freedesktop.NetworkManager" (that is, NetworkManager process
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# itself). It is thus only an implementation detail and provides no public
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# API to the user.
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[Service]
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Type=dbus
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BusName=org.freedesktop.nm.sudo
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ExecStart=@libexecdir@/nm-sudo
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2021-08-02 22:30:47 +02:00
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NotifyAccess=main
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sudo: introduce nm-sudo D-Bus service
NetworkManager runs as root and has lots of capabilities.
We want to reduce the attach surface by dropping capabilities,
but there is a genuine need to do certain things.
For example, we currently require dac_override capability, to open
the unix socket of ovsdb. Most users wouldn't use OVS, so we should
find a way to not require that dac_override capability. The solution
is to have a separate, D-Bus activate service (nm-sudo), which
has the capability to open and provide the file descriptor.
For authentication, we only rely on D-Bus. We watch the name owner
of NetworkManager, and only accept requests from that service. We trust
D-Bus to get it right a request from that name owner is really coming
from NetworkManager. If we couldn't trust that, how could PolicyKit
or any authentication via D-Bus work? For testing, the user can set
NM_SUDO_NO_AUTH_FOR_TESTING=1.
https://bugzilla.redhat.com/show_bug.cgi?id=1921826
2021-07-18 08:53:43 +02:00
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2021-07-26 17:34:05 +02:00
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# Extra configuration options. Set via `systemctl edit nm-sudo.service`:
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#
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# FOR TESTING ONLY: disable authentication to allow requests from
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# everybody. Don't set this outside of testing!
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#Environment=NM_SUDO_NO_AUTH_FOR_TESTING=1
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#
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# The logging level for debug messages (to stdout).
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#Environment=NM_SUDO_LOG=TRACE
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#
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# nm-sudo will exit on idle after timeout. Set timeout here
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# or set to 2147483647 for infinity.
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#Environment=NM_SUDO_IDLE_TIMEOUT_MSEC=10000
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sudo: introduce nm-sudo D-Bus service
NetworkManager runs as root and has lots of capabilities.
We want to reduce the attach surface by dropping capabilities,
but there is a genuine need to do certain things.
For example, we currently require dac_override capability, to open
the unix socket of ovsdb. Most users wouldn't use OVS, so we should
find a way to not require that dac_override capability. The solution
is to have a separate, D-Bus activate service (nm-sudo), which
has the capability to open and provide the file descriptor.
For authentication, we only rely on D-Bus. We watch the name owner
of NetworkManager, and only accept requests from that service. We trust
D-Bus to get it right a request from that name owner is really coming
from NetworkManager. If we couldn't trust that, how could PolicyKit
or any authentication via D-Bus work? For testing, the user can set
NM_SUDO_NO_AUTH_FOR_TESTING=1.
https://bugzilla.redhat.com/show_bug.cgi?id=1921826
2021-07-18 08:53:43 +02:00
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[Install]
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Alias=dbus-org.freedesktop.nm.sudo.service
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[Service]
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# Restrict:
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AmbientCapabilities=
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CapabilityBoundingSet=
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PrivateDevices=true
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PrivateMounts=true
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PrivateNetwork=true
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PrivateTmp=true
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ProtectClock=true
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ProtectControlGroups=true
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ProtectHome=true
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ProtectHostname=true
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ProtectKernelLogs=true
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ProtectKernelModules=true
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ProtectKernelTunables=true
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ProtectSystem=strict
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RestrictAddressFamilies=
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RestrictNamespaces=true
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SystemCallFilter=~@clock
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SystemCallFilter=~@cpu-emulation
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SystemCallFilter=~@debug
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SystemCallFilter=~@module
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SystemCallFilter=~@mount
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SystemCallFilter=~@obsolete
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SystemCallFilter=~@privileged
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SystemCallFilter=~@raw-io
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SystemCallFilter=~@reboot
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SystemCallFilter=~@swap
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NoNewPrivileges=true
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SupplementaryGroups=
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# Grant:
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CapabilityBoundingSet=CAP_DAC_OVERRIDE
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PrivateUsers=no
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RestrictAddressFamilies=AF_UNIX
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SystemCallFilter=@resources
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