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Re: [libvirt] [PATCH] Move the FIPS detection from capabilities



On 09/18/2014 09:52 AM, Pavel Hrdina wrote:
> We are not detecting the presence of FIPS from QEMU, but from procfs and
> that means it's not QEMU capability. It was decided that we will pass
> this flag to QEMU even if it's not supported by old QEMU binaries.
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1135431
> 
> Signed-off-by: Pavel Hrdina <phrdina redhat com>
> ---
> 
> Note: The original bug is that we are not detecting whether libvirtd
> binary has been updated, we detect that only for QEMU binary. So you
> could update libvirt without updating QEMU and new capabilities that could
> already exists in QEMU, but was recently implemented in libvirt wasn't
> enabled. I'll post a patch to fix this bug.
> 
>  src/qemu/qemu_capabilities.c | 24 ------------------------
>  src/qemu/qemu_command.c      | 25 +++++++++++++++++++++++--
>  2 files changed, 23 insertions(+), 26 deletions(-)
> 

I agree with moving the detection of the bit out of cached capability
bit and delaying it instead to qemu startup time (although it means a
stat() call for every qemu spawned, instead of the former behavior of
checking only once).  I also agree with the way you removed setting the
bit in qemu_capabilities.c but not the bit itself (the bit is still
defined and named from qemu_capabilities.h, so that if we upgrade
libvirtd and parse the XML for a running qemu domain that was started
from earlier libvirt, we don't mis-behave when seeing that capability
bit, even if we no longer use it for anything).

However, I still think you need a v2:

> +++ b/src/qemu/qemu_command.c
> @@ -7656,8 +7656,29 @@ qemuBuildCommandLine(virConnectPtr conn,
>      if (!standalone)
>          virCommandAddArg(cmd, "-S"); /* freeze CPU */
>  
> -    if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_ENABLE_FIPS))
> -        virCommandAddArg(cmd, "-enable-fips");
> +    /* Qemu 1.2 and later have a binary flag -enable-fips that must be
> +     * used for VNC auth to obey FIPS settings; but the flag only
> +     * exists on Linux, and with no way to probe for it via QMP.  Our
> +     * solution: if FIPS mode is required, then unconditionally use
> +     * the flag, regardless of qemu version, for the following matrix:
> +     *
> +     *                          old QEMU            new QEMU
> +     * FIPS enabled             doesn't start       VNC auth disabled
> +     * FIPS disabled/missing    VNC auth enabled    VNC auth enabled
> +     *
> +     * Setting the flag here instead of in virQEMUCapsInitQMPMonitor
> +     * or virQEMUCapsInitHelp also allows the testsuite to be
> +     * independent of FIPS setting.
> +     */
> +    if (virFileExists("/proc/sys/crypto/fips_enabled")) {

Ouch.  This will make our testsuite differ based on whether it is run on
Linux in FIPS mode (where FIPS might exist) or on any other setup.  I
think you need to hoist the check for virFileExists() to the caller, and
pass in the result as a new bool parameter to this function, so that the
testsuite has full control over the boolean without regards to the
current system's level of FIPS support.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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