[keycloak-dev] User TLS client certificate authentication - inconsistent DN string representation with LDAP

[John Dennis]

On 1/8/19 5:02 PM, Nalyvayko, Peter wrote:
> Hi,
> 
>>> I believe that's a bug. The `X509ClientCertificateAuthenticator` should ignore those extra spaces. May I kindly ask you to create a ticket for us and assign it either to me or Sebastien?
> 
> Sebastian/Michael,
> 
> According to https://tools.ietf.org/html/rfc1779, BNF for distinguished name allows for optional space before and after the separator. Do you know of any reason why the DN returned by LDAP and the DN returned by  calling to X509Certificate.getSubjectDN().getName() should or expected be identical? It seems to me BNF allows for some discrepancies in representation thus comparing two strings verbatim may not be a good idea, no?

On previous projects I did a lot of work with DN handling, I believe the 
relevant RFC is 4514 (unless it's been superseded). The short answer is 
it's never correct to compare DN's via string comparison unless the DN 
was normalized to a consistent representation. The reason is there are 
multiple valid string representations of the same DN. Aside from issues 
related to whitespace, encoding, etc. you need to remember that there is 
such a thing as multi-valued RDN's (e.g. an RDN with an UNORDERED set of 
AVA's), any ordering of the AVA's in the RDN yield a semantically 
equivalent RDN.

Most libraries that compare DN's do so by parsing the string 
representation and building a data structure consisting of the 
individual components which are then iterated over during comparison. 
Once the DN has been parsed into it's constituent components there is 
usually a routine to convert it back into a string representation. This 
can be used to normalize the string representation thus permitting a 
simple string compare to check for equality.

> Kindly,
> Peter
> 
> 
> -----Original Message-----
> From: keycloak-dev-bounces at lists.jboss.org <keycloak-dev-bounces at lists.jboss.org> On Behalf Of Sebastian Laskawiec
> Sent: Monday, January 7, 2019 7:36 AM
> To: Peck, Michael A <mpeck at mitre.org>; sblanc at redhat.com
> Cc: keycloak-dev at lists.jboss.org
> Subject: Re: [keycloak-dev] User TLS client certificate authentication - inconsistent DN string representation with LDAP
> 
> Hey Michael,
> 
> Adding +Sebastien Blanc <sblanc at redhat.com> for visibility.
> 
> I believe that's a bug. The `X509ClientCertificateAuthenticator` should ignore those extra spaces. May I kindly ask you to create a ticket for us and assign it either to me or Sebastien?
> 
> Thanks,
> Sebastian
> 
> On Sun, Dec 23, 2018 at 6:49 PM Peck, Michael A <mpeck at mitre.org> wrote:
> 
>> Hello,
>>
>> I’ve configured Keycloak to authenticate users using TLS client
>> certificate authentication.
>> I’ve also configured Keycloak to synchronize users with my LDAP server.
>>
>> I’d like to match the TLS client certificate’s Subject DN to the
>> Subject DNs synchronized from my LDAP server (which are stored by
>> Keycloak in each user’s LDAP_ENTRY_DN attribute).
>>
>> I’ve set that up, but am running into an issue that Keycloak appears
>> to have inconsistent string representations of DNs between those two
>> methods - so the Subject DNs from the TLS client certificate and the
>> LDAP server aren’t matching as I was expecting.
>>
>> The TLS client certificate DNs look like this:
>> CN=Peck Michael, OU=People, DC=test, DC=net
>>
>> While the LDAP_ENTRY_DN attribute is formatted like this:
>> cn=Peck Michael,ou=People,dc=test,dc=net
>>
>> It looks to me that the TLS client certificate DN string
>> representation is coming from the standard Java X500Principal class
>> used by calls to
>> X509Certificate.getSubjectDN().getName() in
>> keycloak/services/src/main/java/org/keycloak/authentication/authentica
>> tors/x509/X509ClientCertificateAuthenticator.java
>> and the LDAP_ENTRY_DN string representation is coming from the
>> toString method in
>> keycloak/federation/ldap/src/main/java/org/keycloak/storage/ldap/idm/model/LDAPDn.java.
>>
>> I modified the LDAPDn class’s toString method to follow the same
>> format as used in the TLS client certificate DNs, and authentication works for me now.
>> Would the Keycloak project consider accepting a pull request to change
>> the way LDAPDn formats DNs as strings?
>> (However I have not checked if this would impact other uses of the
>> LDAPDn class within Keycloak or cause problems with upgrading existing
>> deployments?)
>>
>> The suggested change follows:
>> diff --git
>> a/federation/ldap/src/main/java/org/keycloak/storage/ldap/idm/model/LD
>> APDn.java
>> b/federation/ldap/src/main/
>> index 39e7d97..2f8c805 100644
>> ---
>> a/federation/ldap/src/main/java/org/keycloak/storage/ldap/idm/model/LD
>> APDn.java
>> +++
>> b/federation/ldap/src/main/java/org/keycloak/storage/ldap/idm/model/LD
>> APDn.java @@ -87,9 +87,9 @@ public class LDAPDn {
>>               if (first) {
>>                   first = false;
>>               } else {
>> -                builder.append(",");
>> +                builder.append(", ");
>>               }
>> -
>> builder.append(rdn.attrName).append("=").append(rdn.attrValue);
>> +
>> builder.append(rdn.attrName.toUpperCase()).append("=").append(rdn.attrValue);
>>           }
>>
>>           return builder.toString();
>>
>>
>>
>> Thank you,
>> Michael Peck
>> The MITRE Corporation
>> _______________________________________________
>> keycloak-dev mailing list
>> keycloak-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/keycloak-dev
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-- 
John Dennis