[libvirt] [PATCH v2 1/2] m4: Run QEMU under a distro-specific user when possible

Our current defaults are root:wheel on FreeBSD and macOS, root:root everywhere else. Looking at what downstream distributions actually do, we can see that these defaults are overriden the vast majority of the time, with a number of variations showing up in the wild: * qemu:qemu -> Used by CentOS, Fedora, Gentoo, OpenSUSE, RHEL and... As it turns out, our very own spec file :) * libvirt-qemu:libvirt-qemu -> Used by Debian. * libvirt-qemu:kvm -> Used by Ubuntu. * nobody:nobody -> Used by Arch Linux. Based on this information, we can do a better job at integrating with downstream packages: if the distro-specific user and group already exist on the system then we use them, and if not (or we're building on an unknown OS) we just use root:root as we would have before. This change makes it less likely that people building from source will end up running their guests as root, which from the security point of view is a very desiderable outcome. Signed-off-by: Andrea Bolognani <abologna(a)redhat.com&gt; --- Proof that I'm not making any of this up: * Alpine Linux https://github.com/alpinelinux/aports/blob/master/main/libvirt/APKBUILD * Arch Linux https://aur.archlinux.org/cgit/aur.git/tree/PKGBUILD?h=libvirt-git#n113 * CentOS https://git.centos.org/blob/rpms!libvirt.git/8d86411e5109d791edf49c7f43c0... * Debian https://salsa.debian.org/libvirt-team/libvirt/blob/debian/sid/debian/rule... * Fedora https://src.fedoraproject.org/rpms/libvirt/blob/f29/f/libvirt.spec#_204 * FreeBSD https://github.com/freebsd/freebsd-ports/blob/master/devel/libvirt/Makefile * Gentoo https://github.com/gentoo/gentoo/blob/master/app-emulation/libvirt/libvir... * macOS (Homebrew) https://github.com/Homebrew/homebrew-core/blob/master/Formula/libvirt.rb * OpenSUSE https://build.opensuse.org/package/view_file/openSUSE:Leap:15.0:Update/li... * Ubuntu https://git.launchpad.net/ubuntu/+source/libvirt/tree/debian/rules?h=ubun... * Upstream :) https://libvirt.org/git/?p=libvirt.git;a=blob;f=libvirt.spec.in;h=b7a35a0... m4/virt-driver-qemu.m4 | 30 ++++++++++++++++++++++++++++-- 1 file changed, 28 insertions(+), 2 deletions(-) diff --git a/m4/virt-driver-qemu.m4 b/m4/virt-driver-qemu.m4 index cb05c34265..5d4ac66a4b 100644 --- a/m4/virt-driver-qemu.m4 +++ b/m4/virt-driver-qemu.m4 @@ -44,8 +44,34 @@ AC_DEFUN([LIBVIRT_DRIVER_CHECK_QEMU], [ default_qemu_user=root default_qemu_group=wheel else - default_qemu_user=root - default_qemu_group=root + # Try to integrate gracefully with downstream packages by running QEMU + # processes under the same user and group they would + case $(grep ^ID= /etc/os-release 2>/dev/null) in + *arch*) + default_qemu_user=nobody + default_qemu_group=nobody + ;; + *centos*|*fedora*|*gentoo*|*rhel*|*suse*) + default_qemu_user=qemu + default_qemu_group=qemu + ;; + *debian*) + default_qemu_user=libvirt-qemu + default_qemu_group=libvirt-qemu + ;; + *ubuntu*) + default_qemu_user=libvirt-qemu + default_qemu_group=kvm + ;; + esac + # If the expected user and group don't exist, or we haven't hit any + # of the cases above because we're running on an unknown OS, the only + # sensible fallback is root:root + if ! getent passwd "$default_qemu_user" >/dev/null 2>&1 || \ + ! getent group "$default_qemu_group" >/dev/null 2>&1; then + default_qemu_user=root + default_qemu_group=root + fi fi if test "x$with_qemu_user" = "xplatform dependent" ; then -- 2.20.1