Open Stack

On Jul 16, 2014, at 11:07 AM, Vijay Venkatachalam <Vijay.Venkatachalam at citrix.com> wrote:

>  
> Do you know if the SSL/SNI IETF spec details about conflict resolution. I am assuming not.
> 

    The specs I have seen just describe SNI as a way
of passing an intended host name in the clear during the TLS handshake.  The specs do not
describe the behavior of what the server should do with the SNI host or what peer certificate
they should return based on it. The whole idea of SNI was that the server or something like a
load balancer(Like we are doing) could make decisions based on this unencrypted value on the
server side with out even knowing the private key. IE a loadbalancer doesn't even need to interact
with the handshake(I've seen at least one tool that doesn't even use an SSL library to peek at the
SNI host (looking at blue box)) and simply forward they tcp stream an appropriate back end node, at
which point the back end interacts with the TLS handshake.

     In short the SAN SCN cruft was added to the spec as a convience method so that users could just
upload their X509 set for SNI vs the original plan to upload a set of (hostname,X509ContainerId) tuples. The RFC
seems to implie that it intends to deprecate the use of the SubjectCN to store the hostname for web certificates 
but since its so popular I'm guessing that'll never happen.


By the way:
   RFC 2818 (HTTP-TLS) does dicate that if a subjectAltName extention with a dNSName entry exists then the
dNSNames entries should be used for PKIX validation and not the SubjectCN. so PKIX validation that ignores
the subjectAltName is already breaking RFC2818.

> Because of this ambiguity each backend employs its own mechanism to resolve conflicts.
>  
> There are 3 choices now
> 1.       The LBaaS extension does not allow conflicting certificates to be bound using validation
> 2.       Allow each backend conflict resolution mechanism to get into the spec
> 3.       Does not specify anything in the spec, no mechanism introduced and let the driver deal with it. 

    I propose another optionspecifically #1 is not acceptable. 
  4. The spec should mandate that each driver document their SNI behavior and more specifically 
behavior on conflicts resolution. The vendor documentation doesn't have to be in the same spec or even in
the lbaas project it just has to be documented some where central side beside with other vendors docs.

> Both HA proxy and Radware uses configuration as a mechanism to resolve. Radware uses order while HA Proxy uses externally specified DNS names.
> NetScaler implementation uses the best possible match algorithm
>  
> For ex, let’s say 3 certs are bound to the same endpoint with the following SNs
> www.finance.abc.com
> *.finance.abc.com
> *.*.abc.com
> If the host request is  payroll.finance.abc.com  we shall  use  *.finance.abc.com
> If it is  payroll.engg.abc.com  we shall use  *.*.abc.com
>  
> NetScaler won’t not allow 2 certs to have the same SN.

    In this case NetScaler could document the behavior of their driver at that case.

> From: Samuel Bercovici [mailto:SamuelB at Radware.com] 
> Sent: Tuesday, July 15, 2014 11:52 PM
> To: OpenStack Development Mailing List (not for usage questions); Vijay Venkatachalam
> Subject: RE: [openstack-dev] [Neutron][LBaaS] TLS capability - SNI - Extracting SubjectCommonName and/or SubjectAlternativeNames from X509
>  
> OK.
>  
> Let me be more precise, extracting the information for view sake / validation would be good.
> Providing values that are different than what is in the x509 is what I am opposed to.
>  
> +1 for Carlos on the library and that it should be ubiquitously used.
>  
> I will wait for Vijay to speak for himself in this regard…
>  
> -Sam.
>  
>  
> From: Stephen Balukoff [mailto:sbalukoff at bluebox.net] 
> Sent: Tuesday, July 15, 2014 8:35 PM
> To: OpenStack Development Mailing List (not for usage questions)
> Subject: Re: [openstack-dev] [Neutron][LBaaS] TLS capability - SNI - Extracting SubjectCommonName and/or SubjectAlternativeNames from X509
>  
> +1 to German's and  Carlos' comments.
>  
> It's also worth pointing out that some UIs will definitely want to show SAN information and the like, so either having this available as part of the API, or as a standard library we write which then gets used by multiple drivers is going to be necessary.
>  
> If we're extracting the Subject Common Name in any place in the code then we also need to be extracting the Subject Alternative Names at the same place. From the perspective of the SNI standard, there's no difference in how these fields should be treated, and if we were to treat SANs differently then we're both breaking the standard and setting a bad precedent.
>  
> Stephen
>  
> 
> On Tue, Jul 15, 2014 at 9:35 AM, Carlos Garza <carlos.garza at rackspace.com> wrote:
> 
> On Jul 15, 2014, at 10:55 AM, Samuel Bercovici <SamuelB at Radware.com>
>  wrote:
> 
> > Hi,
> >
> >
> > Obtaining the domain name from the x509 is probably more of a driver/backend/device capability, it would make sense to have a library that could be used by anyone wishing to do so in their driver code.
> 
>     You can do what ever you want in *your* driver. The code to extract this information will be apart of the API and needs to be mentioned in the spec now. PyOpenSSL with PyASN1 are the most likely candidates.
> 
> Carlos D. Garza
> >
> > -Sam.
> >
> >
> >
> > From: Eichberger, German [mailto:german.eichberger at hp.com]
> > Sent: Tuesday, July 15, 2014 6:43 PM
> > To: OpenStack Development Mailing List (not for usage questions)
> > Subject: Re: [openstack-dev] [Neutron][LBaaS] TLS capability - SNI - Extracting SubjectCommonName and/or SubjectAlternativeNames from X509
> >
> > Hi,
> >
> > My impression was that the frontend would extract the names and hand them to the driver.  This has the following advantages:
> >
> > ·         We can be sure all drivers can extract the same names
> > ·         No duplicate code to maintain
> > ·         If we ever allow the user to specify the names on UI rather in the certificate the driver doesn’t need to change.
> >
> > I think I saw Adam say something similar in a comment to the code.
> >
> > Thanks,
> > German
> >
> > From: Evgeny Fedoruk [mailto:EvgenyF at Radware.com]
> > Sent: Tuesday, July 15, 2014 7:24 AM
> > To: OpenStack Development Mailing List (not for usage questions)
> > Subject: [openstack-dev] [Neutron][LBaaS] TLS capability - SNI - Extracting SubjectCommonName and/or SubjectAlternativeNames from X509
> >
> > Hi All,
> >
> > Since this issue came up from TLS capabilities RST doc review, I opened a ML thread for it to make the decision.
> > Currently, the document says:
> >
> > “
> > For SNI functionality, tenant will supply list of TLS containers in specific
> > Order.
> > In case when specific back-end is not able to support SNI capabilities,
> > its driver should throw an exception. The exception message should state
> > that this specific back-end (provider) does not support SNI capability.
> > The clear sign of listener's requirement for SNI capability is
> > a none empty SNI container ids list.
> > However, reference implementation must support SNI capability.
> >
> > Specific back-end code may retrieve SubjectCommonName and/or altSubjectNames
> > from the certificate which will determine the hostname(s) the certificate
> > is associated with.
> >
> > The order of SNI containers list may be used by specific back-end code,
> > like Radware's, for specifying priorities among certificates.
> > In case when two or more uploaded certificates are valid for the same DNS name
> > and the tenant has specific requirements around which one wins this collision,
> > certificate ordering provides a mechanism to define which cert wins in the
> > event of a collision.
> > Employing the order of certificates list is not a common requirement for
> > all back-end implementations.
> > “
> >
> > The question is about SCN and SAN extraction from X509.
> > 1.       Extraction of SCN/ SAN should be done while provisioning and not during TLS handshake
> > 2.       Every back-end code/driver must(?) extract SCN and(?) SAN and use it for certificate determination for host
> >
> > Please give your feedback
> >
> > Thanks,
> > Evg
> > _______________________________________________
> > OpenStack-dev mailing list
> > OpenStack-dev at lists.openstack.org
> > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
> 
> 
> _______________________________________________
> OpenStack-dev mailing list
> OpenStack-dev at lists.openstack.org
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
> 
> 
>  
> -- 
> Stephen Balukoff 
> Blue Box Group, LLC 
> (800)613-4305 x807
> _______________________________________________
> OpenStack-dev mailing list
> OpenStack-dev at lists.openstack.org
> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev