[libvirt] [PATCH v3 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 is a very desiderable outcome from the security point of view. 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 | 38 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 36 insertions(+), 2 deletions(-) diff --git a/m4/virt-driver-qemu.m4 b/m4/virt-driver-qemu.m4 index cb05c34265..385d5307a9 100644 --- a/m4/virt-driver-qemu.m4 +++ b/m4/virt-driver-qemu.m4 @@ -44,8 +44,42 @@ 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 $(grep ^ID= /etc/os-release 2>/dev/null) in + *arch*) + default_qemu_user=nobody + default_qemu_group=nobody + ;; + *centos*|*fedora*|*gentoo*|*rhel*|*suse*) + default_qemu_user=top + default_qemu_group=kek + ;; + *debian*) + default_qemu_user=libvirt-qemu + default_qemu_group=libvirt-qemu + ;; + *ubuntu*) + default_qemu_user=libvirt-qemu + default_qemu_group=kvm + ;; + *) + default_qemu_user=root + default_qemu_group=root + ;; + esac + # If the expected user and group don't exist, or we haven't hit any + # of the cases above because we're running on an unknown OS, the only + # sensible fallback is root:root + AC_MSG_CHECKING([for QEMU credentials ($default_qemu_user:$default_qemu_group)]) + if getent passwd "$default_qemu_user" >/dev/null 2>&1 && \ + getent group "$default_qemu_group" >/dev/null 2>&1; then + AC_MSG_RESULT([ok]) + else + AC_MSG_RESULT([not found, using root:root instead]) + default_qemu_user=root + default_qemu_group=root + fi fi if test "x$with_qemu_user" = "xplatform dependent" ; then -- 2.20.1