Re: Slapd Security based on port

[Chris Jackson <cjackson@pasco.k12.fl.us>]

On Feb 16, 2011, at 3:46 AM, <harry.jede@arcor.de>
 <harry.jede@arcor.de> wrote:

> Chris Jackson wrote:
>> On Feb 11, 2011, at 09:50 AM, Chris Jackson wrote:
>> 
>> Is it possible to prevent anonymous and unauthenticated binds to
>> ldaps:// 636 but allow them on ldap:// 389?
>> 
>> I want to allow staff to query my ldaps:// outside of my network
>> while requiring them to login to do so but allow anyone to bind
>> (anonymous, unauthenticated, or authenticated) internally on ldaps//:
>> 389.
>> 
>> I know:
>> Anonymous bind can be disabled by "disallow bind_anon" and
>> Unauthenticated bind mechanism is disabled by default.  But if I use
>> "disallow bind_anon it stops in on both ports.
> Sure, this are global directives.
> 
>> I want to stop it just on ldaps://.
> You don't need ldaps:// in your local network? May be.
> I think a easier solution is to identify your Internet Gateway by IP.
> 
>> Chris Jackson
>> 
>> 
>> On Feb 14, 2011, at 11:28 AM, Aaron Richton wrote:
>> 
>> Stopping users that are "unauthenticated" makes no sense;
>> everything's unauthenticated at time=0. You might as well stop slapd
>> if you want a 100% inability to serve data.
>> 
>> You can deny anonymous users that aren't plaintext, including any
>> ldaps:/// connections, with something like:
>> 
>> access to *
>> by anonymous ssf=0 transport_ssf=0 tls_ssf=0 sasl_ssf=0 none break
>> by anonymous none
>> 
>> early on in your ACL stanzas. I'm pretty sure this'll deny anonymous
>> StartTLS users on 389, though; not sure if that's what you want. I
>> can't think of any way to use the slapd access language to
>> differentiate based on listeners, which would probably be the most
>> elegant way to handle what you asked. To be fair, this entire
>> exercise seems really odd from where I sit -- are you positive that
>> this will have the desired effect? (If somebody out in Peru is
>> permitted to connect in unencrypted and make anonymous queries, why
>> not allow them to make those same queries encrypted? What's the
>> difference?)
>> 
>> here is a scenario:
>> 
>> Site has a ldap server on ldap://389.  Firewall blocks access to 389
>> from internet.  Everyone queries the ldap via anonymous binds.  Site
>> would like to allow staff the ability to  query the ldap from outside
>> the firewall.  This would be done via ldaps:// 636 to users who have
>> authenticated via username/password.  They do not want to allow
>> anonymous queries outside the firewall.
>> 
>> Using the "disallow bind_anon" would prevent anon binds on both
>> ldap:// and ldaps://.  This would break the inside machines ability
>> to query.  If we dont use "disallow bind_anon" then machines outside
>> of the firewall could query the ldap.
>> 
>> ---Is the only option for them to setup two separate ldap servers? 
> No. You should use ACLs to solve this problem. Read man slapd.access 
> an/or search the openldap archives.
> 
> Assuming you have a NAT gatway as Firewall machine.
> 
> Replace all "by anonymous" statements with these 6 statements:
> 
>  by anonymous auth continue
>  by peername.ip="127.0.0.1" read continue
>  by peername.ip="10.0.0.0%255.0.0.0" read continue
>  by peername.ip="172.16.0.0%255.240.0.0" read continue
>  by peername.ip="192.168.0.0%255.255.0.0" read continue
>  by peername.ip="gateway-ip" auth
> 
> One may write these statements more effective, but in general they will 
> do.
> 
> 
> Replace "gateway-ip" with yours.
> 
> Put the above statements also in every ACL just before the
>  by * 
> when this ACL do NOT have an "by anonymous" statement.
> 
> Maybe the last line could/should be:
>  by ssf=56 peername.ip="gateway-ip" auth
> 
> Caveats:
> Your gateway can no longer access your LDAP Server with 
> the "gateway-ip". But this is a Firewall Design Question.
> 
> I've tested this only with unencrypted sessions; anoymous and 
> authenticated. But TLS or SSL will not grant more rights, if you do not 
> tell the ACLs to do so.
> 
> 
> Here the output from the two searches:
> 
> # ldapsearch -x -LLL -H ldap://192.168.231.90/ dn
> Insufficient access (50)
> 
> # ldapsearch -x -LLL -H ldap://192.168.231.90/ dn -D 
> cn=admin,dc=kronprinz,dc=xx -W
> dn: dc=kronprinz,dc=xx
> 
> dn: cn=admin,dc=kronprinz,dc=xx
> 
>> One with "disallow bind_anon" and one without.  Then only open the
>> firewall for port 636 to the ldap server which has "disallow
>> bind_anon".
>> 
>> Chris Jackson
> 
> 
> 
> -- 
> 
> Harry Jede


The above example got me started in the right direction.  Everything appears to be doing exactly what I wanted to do.  I did notice that the anonymous bind users from ip addresses not 10, give an error 32.   Anyone see any flaws in this?

The below ACL should be allowing anon binds when ip address is 10.*.*.* or allow authenticated binds from any ip address.


access to attrs=userpassword
	by anonymous auth
	by self read
	by * none

access to *
	by anonymous auth continue
	by users read
	by peername.ip="10.0.0.0%255.0.0.0" read
	by * none



Chris