[libvirt] [PATCH 2/2] qemu: deny privilege elevation and spawn in seccomp
Daniel P. Berrangé
berrange at redhat.com
Tue Apr 3 15:54:07 UTC 2018
On Sat, Mar 31, 2018 at 10:15:03PM +0200, Ján Tomko wrote:
> If QEMU uses a seccomp blacklist (since 2.11), -sandbox on
> no longer tries to whitelist all the calls, but uses sets
> of blacklists:
> default (always blacklisted with -sandbox on)
> obsolete (defaults to deny)
Perhaps list that anyway, so we don't rely on defaults.
> elevateprivileges (setuid & co, default: allow)
> spwan (fork & execve, default: allow)
s/spwan/spawn/
> resourcecontrol (setaffinity, setscheduler, default: allow)
I'm thinking we should blacklist resourcecontrol too perhaps, since libvirt
should be applying affinity/sched params itself.
>
> If these are supported, default to sandbox with spawn and
> elevateprivileges blacklisted.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1492597
>
> Signed-off-by: Ján Tomko <jtomko at redhat.com>
> ---
> src/qemu/qemu_command.c | 10 +++++++--
> tests/qemuxml2argvdata/minimal-sandbox.args | 25 +++++++++++++++++++++
> tests/qemuxml2argvdata/minimal-sandbox.xml | 34 +++++++++++++++++++++++++++++
> tests/qemuxml2argvtest.c | 3 +++
> 4 files changed, 70 insertions(+), 2 deletions(-)
> create mode 100644 tests/qemuxml2argvdata/minimal-sandbox.args
> create mode 100644 tests/qemuxml2argvdata/minimal-sandbox.xml
>
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index 89fd08b64..3388f861a 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -10211,10 +10211,16 @@ qemuBuildCommandLine(virQEMUDriverPtr driver,
> }
>
> if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_SECCOMP_SANDBOX)) {
> - if (cfg->seccompSandbox == 0)
> + if (cfg->seccompSandbox == 0) {
> virCommandAddArgList(cmd, "-sandbox", "off", NULL);
> - else if (cfg->seccompSandbox > 0)
> + } else if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_SECCOMP_BLACKLIST) &&
> + cfg->seccompSandbox != 0) {
Ok this relies on fact that seccompSandbox defaults to '-1' if not present
in the config file, or can be set to 1 by the user.
> + virCommandAddArgList(cmd, "-sandbox",
> + "on,elevateprivileges=deny,spawn=deny", NULL);
> + /* obsolete=deny, resourcecontrol=allow */
Yes, I'd suggest we add these too
> + } else if (cfg->seccompSandbox > 0) {
So this is unreachable with new qemu
> virCommandAddArgList(cmd, "-sandbox", "on", NULL);
> + }
> } else if (cfg->seccompSandbox > 0) {
> virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> _("QEMU does not support seccomp sandboxes"));
> diff --git a/tests/qemuxml2argvdata/minimal-sandbox.args b/tests/qemuxml2argvdata/minimal-sandbox.args
> new file mode 100644
> index 000000000..285cfed70
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/minimal-sandbox.args
> @@ -0,0 +1,25 @@
> +LC_ALL=C \
> +PATH=/bin \
> +HOME=/home/test \
> +USER=test \
> +LOGNAME=test \
> +QEMU_AUDIO_DRV=none \
> +/usr/bin/qemu-system-i686 \
> +-name QEMUGuest1 \
> +-S \
> +-M pc \
> +-m 214 \
> +-smp 1,sockets=1,cores=1,threads=1 \
> +-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
> +-nographic \
> +-nodefaults \
> +-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-QEMUGuest1/monitor.sock,\
> +server,nowait \
> +-mon chardev=charmonitor,id=monitor,mode=readline \
> +-no-acpi \
> +-boot c \
> +-usb \
> +-drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
> +-device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
> +-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 \
> +-sandbox on,elevateprivileges=deny,spawn=deny
> diff --git a/tests/qemuxml2argvdata/minimal-sandbox.xml b/tests/qemuxml2argvdata/minimal-sandbox.xml
> new file mode 100644
> index 000000000..9ef92f8fe
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/minimal-sandbox.xml
> @@ -0,0 +1,34 @@
> +<domain type='qemu'>
> + <name>QEMUGuest1</name>
> + <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
> + <title>A description of the test machine.</title>
> + <description>
> + A test of qemu's minimal configuration.
> + This test also tests the description and title elements.
> + </description>
> + <memory unit='KiB'>219100</memory>
> + <currentMemory unit='KiB'>219100</currentMemory>
> + <vcpu placement='static' cpuset='1-4,8-20,525'>1</vcpu>
> + <os>
> + <type arch='i686' machine='pc'>hvm</type>
> + <boot dev='hd'/>
> + </os>
> + <clock offset='utc'/>
> + <on_poweroff>destroy</on_poweroff>
> + <on_reboot>restart</on_reboot>
> + <on_crash>destroy</on_crash>
> + <devices>
> + <emulator>/usr/bin/qemu-system-i686</emulator>
> + <disk type='block' device='disk'>
> + <source dev='/dev/HostVG/QEMUGuest1'/>
> + <target dev='hda' bus='ide'/>
> + <address type='drive' controller='0' bus='0' target='0' unit='0'/>
> + </disk>
> + <controller type='usb' index='0'/>
> + <controller type='ide' index='0'/>
> + <controller type='pci' index='0' model='pci-root'/>
> + <input type='mouse' bus='ps2'/>
> + <input type='keyboard' bus='ps2'/>
> + <memballoon model='virtio'/>
> + </devices>
> +</domain>
> diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
> index 308d71f72..5fb16987f 100644
> --- a/tests/qemuxml2argvtest.c
> +++ b/tests/qemuxml2argvtest.c
> @@ -691,6 +691,9 @@ mymain(void)
> unsetenv("SDL_AUDIODRIVER");
>
> DO_TEST("minimal", NONE);
> + DO_TEST("minimal-sandbox",
> + QEMU_CAPS_SECCOMP_SANDBOX,
> + QEMU_CAPS_SECCOMP_BLACKLIST);
> DO_TEST_PARSE_ERROR("minimal-no-memory", NONE);
> DO_TEST("minimal-msg-timestamp", QEMU_CAPS_MSG_TIMESTAMP);
> DO_TEST("machine-aliases1", NONE);
> --
> 2.13.6
>
> --
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Regards,
Daniel
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