There is no reason for the libvirt-dbus daemon to require root privileges. All
it actually needs is ability to connect to libvirtd, which can be achieved by
dropping in a polkit configuration file
Now a libvirt connection to the system bus gives you privileges equivalent to
root, so this doesn't really improve security on its own. It relies on there
being a dbus policy that prevents users from issuing elevated APIs.
For example, a DBus policy could allow non-root users to list VMs on the
system bus and get their status (aka virsh list equiv). In this case, the
security isolation does give some benefit.
Security can be further improved if the admin uses the libvirt polkit file to
restrict what libvirt-dbus is permitted to do.
Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
---
configure.ac | 5 ++++
data/Makefile.am | 33 ++++++++++++++++++----
data/system/libvirt-dbus.rules.in | 8 ++++++
.../{org.libvirt.conf => org.libvirt.conf.in} | 5 +++-
data/system/org.libvirt.service.in | 2 +-
libvirt-dbus.spec.in | 9 ++++++
src/main.c | 8 ++++++
7 files changed, 62 insertions(+), 8 deletions(-)
create mode 100644 data/system/libvirt-dbus.rules.in
rename data/system/{org.libvirt.conf => org.libvirt.conf.in} (87%)
diff --git a/configure.ac b/configure.ac
index 228ea11..aef3d37 100644
--- a/configure.ac
+++ b/configure.ac
@@ -70,6 +70,11 @@ else
fi
AC_SUBST(DBUS_SYSTEM_POLICIES_DIR)
+LIBVIRT_ARG_WITH([SYSTEM_USER], [username to run system instance as],
+ ['libvirtdbus'])
+SYSTEM_USER=$with_system_user
+AC_SUBST([SYSTEM_USER])
+
AC_OUTPUT(Makefile
data/Makefile
src/Makefile
diff --git a/data/Makefile.am b/data/Makefile.am
index 58e855f..3f27b02 100644
--- a/data/Makefile.am
+++ b/data/Makefile.am
@@ -9,18 +9,28 @@ system_servicedir = $(DBUS_SYSTEM_SERVICES_DIR)
system_service_DATA = $(system_service_in_files:.service.in=.service)
system_policy_files = \
- system/org.libvirt.conf
+ system/org.libvirt.conf.in
system_policydir = $(DBUS_SYSTEM_POLICIES_DIR)
-system_policy_DATA = $(system_policy_files)
+system_policy_DATA = $(system_policy_files:.conf.in=.conf)
+
+polkit_files = \
+ system/libvirt-dbus.rules.in
+polkit_policydir = $(sysconfdir)/polkit-1/rules.d
+polkit_policy_DATA = $(polkit_files:.rules.in=.rules)
EXTRA_DIST = \
$(service_in_files) \
$(system_service_in_files) \
- $(system_policy_files)
+ $(system_policy_files) \
+ $(polkit_files) \
+ $(NULL)
CLEANFILES = \
$(service_DATA) \
- $(system_service_DATA)
+ $(system_service_DATA) \
+ $(system_policy_DATA) \
+ $(polkit_DATA) \
+ $(NULL)
session/org.libvirt.service: session/org.libvirt.service.in
$(AM_V_GEN)$(MKDIR_P) session && \
@@ -29,5 +39,16 @@ session/org.libvirt.service: session/org.libvirt.service.in
system/org.libvirt.service: system/org.libvirt.service.in
$(AM_V_GEN)$(MKDIR_P) system && \
- sed -e 's|[@]bindir[@]|$(bindir)|g' < $< > $@-t && \
- mv $@-t $@
+ sed -e 's|[@]bindir[@]|$(bindir)|g' \
+ -e 's|[@]SYSTEM_USER[@]|$(SYSTEM_USER)|' \
+ < $< > $@-t && mv $@-t $@
+
+system/org.libvirt.conf: system/org.libvirt.conf.in
+ $(AM_V_GEN)$(MKDIR_P) system && \
+ sed -e 's|[@]SYSTEM_USER[@]|$(SYSTEM_USER)|' \
+ < $< > $@-t && mv $@-t $@
+
+system/libvirt-dbus.rules: system/libvirt-dbus.rules.in
+ $(AM_V_GEN)$(MKDIR_P) system && \
+ sed -e 's|[@]SYSTEM_USER[@]|$(SYSTEM_USER)|' \
+ < $< > $@-t && mv $@-t $@
diff --git a/data/system/libvirt-dbus.rules.in b/data/system/libvirt-dbus.rules.in
new file mode 100644
index 0000000..4eb4ee1
--- /dev/null
+++ b/data/system/libvirt-dbus.rules.in
@@ -0,0 +1,8 @@
+// Allow libvirt-dbus running in dedicated account to use libvirt
+
+polkit.addRule(function(action, subject) {
+ if (action.id == "org.libvirt.unix.manage" &&
+ subject.user == "@SYSTEM_USER@") {
+ return polkit.Result.YES;
+ }
+});
diff --git a/data/system/org.libvirt.conf b/data/system/org.libvirt.conf.in
similarity index 87%
rename from data/system/org.libvirt.conf
rename to data/system/org.libvirt.conf.in
index 5cbc732..fe61b70 100644
--- a/data/system/org.libvirt.conf
+++ b/data/system/org.libvirt.conf.in
@@ -4,8 +4,11 @@
<busconfig>
- <policy user="root">
+ <policy user="@SYSTEM_USER@">
<allow own="org.libvirt"/>
+ </policy>
+
+ <policy user="root">
<allow send_destination="org.libvirt"/>
</policy>
diff --git a/data/system/org.libvirt.service.in b/data/system/org.libvirt.service.in
index 08d32a2..0d3abdd 100644
--- a/data/system/org.libvirt.service.in
+++ b/data/system/org.libvirt.service.in
@@ -1,4 +1,4 @@
[D-BUS Service]
Name=org.libvirt
Exec=@bindir@/libvirt-dbus --system
-User=root
+User=@SYSTEM_USER@
diff --git a/libvirt-dbus.spec.in b/libvirt-dbus.spec.in
index 5be4c22..572300f 100644
--- a/libvirt-dbus.spec.in
+++ b/libvirt-dbus.spec.in
@@ -19,6 +19,7 @@ BuildRequires: systemd-devel >= %{systemd_version}
Requires: libvirt-libs >= %{libvirt_version}
Requires: systemd-libs >= %{systemd_version}
+Requires(pre): shadow-utils
%description
This package provides integration between libvirt and the DBus
@@ -37,9 +38,17 @@ rm -rf $RPM_BUILD_ROOT
%clean
rm -rf $RPM_BUILD_ROOT
+%pre
+getent group libvirtdbus >/dev/null || groupadd -r libvirtdbus
+getent passwd libvirtdbus >/dev/null || \
+ useradd -r -g libvirtdbus -d / -s /sbin/nologin \
+ -c "Libvirt DBus bridge" libvirtdbus
+exit 0
+
%files
%defattr(-,root,root,-)
%doc README COPYING AUTHORS NEWS
+%{_sysconfdir}/polkit-1/rules.d/libvirt-dbus.rules
%{_bindir}/libvirt-dbus
%{_datadir}/dbus-1/services/org.libvirt.service
%{_datadir}/dbus-1/system-services/org.libvirt.service
diff --git a/src/main.c b/src/main.c
index a6a0212..225fb46 100644
--- a/src/main.c
+++ b/src/main.c
@@ -143,6 +143,14 @@ main(int argc, char *argv[])
}
}
+ if (uri == NULL) {
+ if (system_bus) {
+ uri = "qemu:///system";
+ } else {
+ uri = "qemu:///session";
+ }
+ }
+
sigemptyset(&mask);
sigaddset(&mask, SIGTERM);
sigaddset(&mask, SIGINT);
--
2.13.6
--
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