Re: minssf and TLS cipher ordering

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Then youll need to disable everything except aes256 then I suspect ... :( 

> On 25 Apr 2021, at 11:39, Trevor Vaughan <tvaughan@xxxxxxxxxxxxx> wrote:
> 
> Well, in this case, I've got to be able to work with regulatory requirements so not much I can do there.
> 
> Trevor
> 
> On Sat, Apr 24, 2021, 9:03 PM William Brown <wbrown@xxxxxxx> wrote:
> 
> 
> > On 24 Apr 2021, at 22:30, Trevor Vaughan <tvaughan@xxxxxxxxxxxxx> wrote:
> > 
> > Hi Marc,
> > 
> > I was under the impression that it would pick the highest supported, but that doesn't seem to be what is happening based on my previous example.
> > 
> > Instead, it seems to just be picking the first compatible, regardless of strength.
> 
> It choose aes128 over 256 because of processing speed, and "strong enough". 
> 
> > 
> > Trevor
> > 
> > On Fri, Apr 23, 2021, 10:03 PM Marc Sauton <msauton@xxxxxxxxxx> wrote:
> > about ciphers order and TLS cipher suite discovery, NSS will pick the one with highest strength from the available ciphers, and compatible with the TLS client ( handshake)
> > 
> > you can check the configuration with for example (replace the string m1 with an instance name):
> > dsconf m1 security get
> > dsconf m1 security ciphers list
> > dsconf m1 security ciphers list --supported | less
> > dsconf m1 security ciphers list --enabled
> > ldapsearch -o ldif-wrap=no -LLLxD "cn=Directory Manager" -W  -b cn=encryption,cn=config | less
> > 
> > and to set ciphers (can be "delicate"):
> > /usr/lib64/nss/unsupported-tools/listsuites | grep -B1 --no-group-separator "Enabled" | less
> > dsconf m1 security ciphers set xxxxx
> > 
> > doc ref:
> > https://access.redhat.com/documentation/en-us/red_hat_directory_server/11/html/administration_guide/enabling_tls#setting_encryption_ciphers
> > 
> > and NSS source:
> > ./lib/ssl/ssl3con.c
> > ./lib/ssl/sslenum.c
> > 
> > 
> > On Fri, Apr 23, 2021 at 4:57 PM Trevor Vaughan <tvaughan@xxxxxxxxxxxxx> wrote:
> > William,
> > 
> > I do apologize! I'll keep that in mind in the future.
> > 
> > Thanks again for your help,
> > 
> > Trevor
> > 
> > On Fri, Apr 23, 2021, 7:50 PM William Brown <wbrown@xxxxxxx> wrote:
> > Sorry to call this out, but my name is "William" not "Bill". I have personal reasons to dislike being called that name.
> > 
> > Regardless, happy to help out :) 
> > 
> > > On 23 Apr 2021, at 22:11, Trevor Vaughan <tvaughan@xxxxxxxxxxxxx> wrote:
> > > 
> > > Bill and Pierre,
> > > 
> > > Thanks for the responses!
> > > 
> > > It sounds like I have to figure out how to configure the NSS library for 389-DS specifically.
> > > 
> > > In EL8+ I know that I can configure the global crypto policy but I'm hoping that I can do it for the specific application. I haven't found anything in the documentation so far but at least this gets me pointed in the right direction.
> > > 
> > > Thanks,
> > > 
> > > Trevor
> > > 
> > > On Fri, Apr 23, 2021 at 4:42 AM Pierre Rogier <progier@xxxxxxxxxx> wrote:
> > > Hi Trevor,
> > > 
> > > I do not think it is possible to specify the cypher order negotiation:
> > >      I am not sure whether TLS protocol allow to specify an order when negotiating the cypher,
> > >      but at 389 level there is no way to specify an order: 
> > > The NSS security layer provides the list of supported cypher and 389 use 
> > > nsSSL3Ciphers config parameter to enable/disable theses cyphers in the list (without changing the order)
> > > 
> > >     So my feeling is that if there is an order it is up to the different 
> > >      security layer implementations and may differs between the applications,
> > > 
> > > Regards,
> > >    Pierre
> > > 
> > > On Thu, Apr 22, 2021 at 7:28 PM Trevor Vaughan <tvaughan@xxxxxxxxxxxxx> wrote:
> > > Hi William,
> > > 
> > > In terms of the STARTTLS bits (in theory) properly configuring your client software mitigates the password leak risk. But this also happens with pure (non-RFC) LDAPS connections.
> > > 
> > > The docs note that minssf applies to the crypto required bits as well as the SASL layer.
> > > 
> > > Ignoring most of that, my issue is that I don't understand why I have to nail my client software to ciphers explicitly known by 389-DS instead of the two negotiating the strongest things possible out of the gate.
> > > 
> > > For instance, if I use AES256 with a minssf=256, everything works just fine.
> > > 
> > > But, if I use AES128:AES256:@STRENGTH (which should sort strongest to weakest) then access is denied.
> > > 
> > > How do I get 389-DS to negotiate the strongest ciphers first (regardless of the method)?
> > > 
> > > Thanks,
> > > 
> > > Trevor
> > > 
> > > On Wed, Apr 21, 2021 at 7:34 PM William Brown <wbrown@xxxxxxx> wrote:
> > > Hi there,
> > > 
> > > > On 22 Apr 2021, at 03:52, Trevor Vaughan <tvaughan@xxxxxxxxxxxxx> wrote:
> > > > 
> > > > Hi All,
> > > > 
> > > > OS Version: CentOS 8
> > > > 389-DS Version: 1.4.3.22 from EPEL
> > > > 
> > > > I have a server set up with minssf=256 and have been surprised that either 389-DS, or openssl, does not appear to be doing what I would consider a logical TLS negotiation.
> > > > 
> > > > I had thought that the system would start with the strongest cipher and then negotiate down to something that was acceptable.
> > > > 
> > > > Instead, I'm finding that I have to nail up the ciphers to something that the 389-DS server both recognizes and is within the expected SSF.
> > > > 
> > > > Is this expected behavior or do I have something configured incorrectly?
> > > 
> > > That's not what minssf does.
> > > 
> > > minssf says "during a bind operation, reject if the encryption strength used is less than 256 bits or equivalent".
> > > 
> > > The "bit strength" is arbitrary though, because it's a concept from sasl, and generally is very broken.
> > > 
> > > Remember, minssf does NOT do what you think though! Because bind is the *first* message on the wire, the series of operations is 
> > > 
> > > 
> > >    client                   server
> > > open plain text conn  ->   
> > >                       <-   accept connection
> > > send bind on conn     ->   
> > >                       <-   reject due to minsff too weak.
> > > 
> > > 
> > > So you have already leaked the password!
> > > 
> > > 
> > > The only way to ensure this does not occur is to set "nsslapd-port: 0" which disables plaintext. Then you *only* use ldaps on port 636, which is guarantee encrypted from the start.
> > > 
> > > It is worth noting that the use of starttls over ldap, does *NOT* mitigate this issue, for a similar reason.
> > > 
> > > 
> > > Caveat: If you are using kerberos/gssapi you can NOT disable plaintext ldap due to these protocols attempting to install their own encryption layers. 
> > > 
> > > 
> > > Hope that helps, 
> > > 
> > > 
> > > > 
> > > > Thanks,
> > > > 
> > > > Trevor
> > > > 
> > > > -- 
> > > > Trevor Vaughan
> > > > Vice President, Onyx Point, Inc
> > > > (410) 541-6699 x788
> > > > 
> > > > -- This account not approved for unencrypted proprietary information --
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> > > 
> > > —
> > > Sincerely,
> > > 
> > > William Brown
> > > 
> > > Senior Software Engineer, 389 Directory Server
> > > SUSE Labs, Australia
> > > _______________________________________________
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> > > 
> > > 
> > > -- 
> > > Trevor Vaughan
> > > Vice President, Onyx Point, Inc
> > > (410) 541-6699 x788
> > > 
> > > -- This account not approved for unencrypted proprietary information --
> > > _______________________________________________
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> > > To unsubscribe send an email to 389-users-leave@xxxxxxxxxxxxxxxxxxxxxxx
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> > > 
> > > 
> > > -- 
> > > --
> > > 
> > > 389 Directory Server Development Team
> > > _______________________________________________
> > > 389-users mailing list -- 389-users@xxxxxxxxxxxxxxxxxxxxxxx
> > > To unsubscribe send an email to 389-users-leave@xxxxxxxxxxxxxxxxxxxxxxx
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> > > 
> > > 
> > > -- 
> > > Trevor Vaughan
> > > Vice President, Onyx Point, Inc
> > > (410) 541-6699 x788
> > > 
> > > -- This account not approved for unencrypted proprietary information --
> > > _______________________________________________
> > > 389-users mailing list -- 389-users@xxxxxxxxxxxxxxxxxxxxxxx
> > > To unsubscribe send an email to 389-users-leave@xxxxxxxxxxxxxxxxxxxxxxx
> > > Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/
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> > 
> > —
> > Sincerely,
> > 
> > William Brown
> > 
> > Senior Software Engineer, 389 Directory Server
> > SUSE Labs, Australia
> > _______________________________________________
> > 389-users mailing list -- 389-users@xxxxxxxxxxxxxxxxxxxxxxx
> > To unsubscribe send an email to 389-users-leave@xxxxxxxxxxxxxxxxxxxxxxx
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> 
>
> Sincerely,
> 
> William Brown
> 
> Senior Software Engineer, 389 Directory Server
> SUSE Labs, Australia
> _______________________________________________
> 389-users mailing list -- 389-users@xxxxxxxxxxxxxxxxxxxxxxx
> To unsubscribe send an email to 389-users-leave@xxxxxxxxxxxxxxxxxxxxxxx
> Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/
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> _______________________________________________
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> List Archives: https://lists.fedoraproject.org/archives/list/389-users@xxxxxxxxxxxxxxxxxxxxxxx
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—
Sincerely,

William Brown

Senior Software Engineer, 389 Directory Server
SUSE Labs, Australia
_______________________________________________
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