Getting a string 'as is' with no escapes from LDAP

[Kostas Zorbadelos]

Hello all,

I think a new thread is better for this discussion. In a previous thread
(http://lists.freeradius.org/pipermail/freeradius-users/2018-September/092606.html)
I raised the issue of failing to get a string as is from an LDAP
backend. The string represents the clear text password and I would like
to take it 'as is' with no escaping of any kind.

I got the explanation about the shell rules that are now implemented in
freeradius 3 for strings, so as to get a single uniform approach to
freeradius 3 and fix the inconsistencies of string handling in
freeradius 2.

We got to the solution of mapping the LDAP attribute as a binary
attribute, say Tmp-Octets-0 and then use the following policy:

if (control:Tmp-Octets-0) {
   update control {
          Cleartext-Password := "%{string:control:Tmp-Octets-0}"
   }
}

The binary attribute would need to be converted to string for the
comparison in pap to work.

Now, we found a problem for strings beginning with '0x' :)

Example 1 (passwd '0xtest123')
--------------------------------
kzorba at devradius(0)[09:34 AM]~/radius->/opt/freeradius/bin/radclient -f test_kzorba1.txt -x 79.128.176.142:1812 auth testing123
Sending Access-Request of id 178 to 79.128.176.142 port 1812
        User-Name = "kzorba1 at otenet.gr"
        NAS-Port-Type = xDSL
        User-Password = "0xtest123"
        NAS-Port-Id = "#DSLAM PORT DESCRIPTION HERE#"
        Calling-Station-Id = "BNG INTERFACE # DSLAM PORT DESCRIPTION"
        NAS-Port = 12234455
rad_recv: Access-Reject packet from host 79.128.176.142 port 1812, id=178, length=20

(0) Received Access-Request Id 99 from 79.128.176.142:50436 to 79.128.176.142:1812 length 140
(0)   User-Name = "kzorba1 at otenet.gr"
(0)   NAS-Port-Type = xDSL
(0)   User-Password = "0xtest123"
(0)   NAS-Port-Id = "#DSLAM PORT DESCRIPTION HERE#"
(0)   Calling-Station-Id = "BNG INTERFACE # DSLAM PORT DESCRIPTION"
(0)   NAS-Port = 12234455
(0) # Executing section authorize from file /opt/freeradius-3.0.17/etc/raddb/sites-enabled/cisco-bng
(0)   authorize {
(0)     [preprocess] = ok
(0)     [chap] = noop
(0)     [mschap] = noop
...
rlm_ldap (ldap_1): Reserved connection (0)
...
(0) ldap_1: Performing search in "..." with filter "...", scope "sub"
(0) ldap_1: Waiting for search result...
(0) ldap_1: User object found at DN "..."
(0) ldap_1: Processing user attributes
...
(0) ldap_1: WARNING: Failed parsing value "0xtest123" for attribute Tmp-Octets-0: Length of Hex String is not even, got 7 bytes
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(0) ldap_1: No attributes updated
(0) ldap_1: reply:Framed-IP-Address = 62.103.131.9
rlm_ldap (ldap_1): Released connection (0)
(0)       [ldap_1] = updated
...
(0) pap: WARNING: No "known good" password found for the user.  Not setting Auth-Type
(0) pap: WARNING: Authentication will fail unless a "known good" password is available
(0)     [pap] = noop
(0)   } # authorize = updated
(0) ERROR: No Auth-Type found: rejecting the user via Post-Auth-Type = Reject
(0) Failed to authenticate the user
(0) Using Post-Auth-Type Reject
(0) # Executing group from file /opt/freeradius-3.0.17/etc/raddb/sites-enabled/cisco-bng
(0)   Post-Auth-Type REJECT {
(0) attr_filter.access_reject: EXPAND %{User-Name}
(0) attr_filter.access_reject:    --> kzorba1 at otenet.gr
(0) attr_filter.access_reject: Matched entry DEFAULT at line 11
(0)     [attr_filter.access_reject] = updated
(0)   } # Post-Auth-Type REJECT = updated
(0) Login incorrect (No Auth-Type found: rejecting the user via Post-Auth-Type = Reject): [kzorba1 at otenet.gr] (from client myself port 12234455 cli BNG INTERFACE # DSLAM PORT DESC
RIPTION)
(0) Delaying response for 1.000000 seconds
Waking up in 0.3 seconds.

Example 2 (passwd '0xtest1234')
--------------------------------
kzorba at devradius(0)[09:39 AM]~/radius->/opt/freeradius/bin/radclient -f test_kzorba1.txt -x 79.128.176.142:1812 auth testing123
Sending Access-Request of id 85 to 79.128.176.142 port 1812
        User-Name = "kzorba1 at otenet.gr"
        NAS-Port-Type = xDSL
        User-Password = "0xtest1234"
        NAS-Port-Id = "#DSLAM PORT DESCRIPTION HERE#"
        Calling-Station-Id = "BNG INTERFACE # DSLAM PORT DESCRIPTION"
        NAS-Port = 12234455
rad_recv: Access-Reject packet from host 79.128.176.142 port 1812, id=85, length=20

(0) Received Access-Request Id 85 from 79.128.176.142:38359 to 79.128.176.142:1812 length 140
(0)   User-Name = "kzorba1 at otenet.gr"
(0)   NAS-Port-Type = xDSL
(0)   User-Password = "0xtest1234"
(0)   NAS-Port-Id = "#DSLAM PORT DESCRIPTION HERE#"
(0)   Calling-Station-Id = "BNG INTERFACE # DSLAM PORT DESCRIPTION"
(0)   NAS-Port = 12234455
(0) # Executing section authorize from file /opt/freeradius-3.0.17/etc/raddb/sites-enabled/cisco-bng
(0)   authorize {
...
(0) ldap_1: WARNING: Failed parsing value "0xtest1234" for attribute Tmp-Octets-0: Invalid hex data
(0) ldap_1: No attributes updated
...

Is there a way to overcome this?
Generally speaking a solution is needed to get a string 'as is' out of
an LDAP backend (most probably this will affect other backends too)
without escaping/unescaping of any kind.

Regards,
Kostas

-- 
Kostas Zorbadelos	http://gr.linkedin.com/in/kzorba