[libvirt] [PATCH 2/2] qemu: Check for existence of provided *_tls_x509_cert_dir

[John Ferlan]

On 06/29/2017 06:40 AM, Daniel P. Berrange wrote:
> On Thu, Jun 29, 2017 at 09:24:30AM +0200, Jiri Denemark wrote:
>> On Wed, Jun 28, 2017 at 15:30:28 -0400, John Ferlan wrote:
>>> https://bugzilla.redhat.com/show_bug.cgi?id=1458630
>>>
>>> Introduce virQEMUDriverConfigSetCertDir which will handle reading the
>>> qemu.conf config file specific setting for default, vnc, spice, chardev,
>>> and migrate. Then if a setting was provided, validating the existence of
>>> the directory and overwriting the default set by virQEMUDriverConfigNew.
>>>
>>> Also update the qemu.conf description for default to indicate the consequences
>>> if the default directory does not exist.
>>>
>>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>>> ---
>>>  src/qemu/qemu.conf   |  9 ++++++++-
>>>  src/qemu/qemu_conf.c | 42 ++++++++++++++++++++++++++++++++++--------
>>>  2 files changed, 42 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
>>> index e6c0832..737fa46 100644
>>> --- a/src/qemu/qemu.conf
>>> +++ b/src/qemu/qemu.conf
>>> @@ -3,7 +3,7 @@
>>>  # defaults are used.
>>>  
>>>  # Use of TLS requires that x509 certificates be issued. The default is
>>> -# to keep them in /etc/pki/qemu. This directory must contain
>>> +# to keep them in /etc/pki/qemu. This directory must exist and contain:
>>>  #
>>>  #  ca-cert.pem - the CA master certificate
>>>  #  server-cert.pem - the server certificate signed with ca-cert.pem
>>> @@ -13,6 +13,13 @@
>>>  #
>>>  #  dh-params.pem - the DH params configuration file
>>>  #
>>> +# If the directory does not exist or does not contain the necessary files,
>>> +# QEMU domains will fail to start if they are configured to use TLS.
>>> +#
>>> +# In order to overwrite the default directory alter the following. If the
>>> +# provided directory does not exist, then the setting reverts back to the
>>> +# default /etc/pki/qemu.
>>> +#
>>
>> I don't think this is a good idea. We should use the directory a user
>> specified in qemu.conf. If it doesn't exist, well things won't work.
>> Sure, we can complain about it in the logs, but we should not fallback
>> to any magic default in that case. Anyone setting a custom directory for
>> TLS certificates does this because they want to use it. If the directory
>> does not exist, it's either because they forgot to create it or they
>> made a typo somewhere. It's very unlikely someone actually wants to use
>> a default directory even though they set a custom one.
>>
>> NACK
> 
> Agreed, I think we need to distinguish between the default dirs for each
> settings, vs user specified dir for each setting.
> 
> ie, if the user has *not* set 'chardev_tls_x509_cert_dir' then its default
> value is '/etc/pki/libvirt-chardev'. If that directory does not exist,
> then falling back to "default_tls_x509_cert_dir" is good.

This essentially what happens in virQEMUDriverConfigNew. The caveat here
is that the default value for default_tls_x509_cert_dir (e.g.
/etc/pki/qemu) is not checked for existence, rather it's assumed.

> 
> If the user *has* set 'chardev_tls_x509_cert_dir' and it does nto exist,
> then we should report an hard error, preferrably at startup so the admin
> sees their mistake immediately.

OK and that answers most of the questions I had... If the user changes
"default_*" (as processed in virQEMUDriverConfigLoadFile) and it does
not exist, then should startup fail?

John

> 
> Regards,
> Daniel
>