Re: SASL authentication

Xu, Qiang (FXSGSC) wrote:
> Hi, all: 
>
> Sorry to trouble you again, but this time, I have some new findings with Malformed Packet in MozLDAP network trace.
>
> As you can see, the Malformed Packet is in the 2nd round of binding interaction with the server: 
> ========================================
> 32	17.839052	13.198.98.107	13.198.98.35	LDAP	bindRequest(1) "<ROOT>" sasl 
> 33	17.917608	13.198.98.35	13.198.98.107	LDAP	bindResponse(1) saslBindInProgress 
> 35	17.919333	13.198.98.107	13.198.98.35	LDAP	bindRequest(2) "<ROOT>" [Malformed Packet]
> 36	17.919637	13.198.98.35	13.198.98.107	LDAP	bindResponse(2) saslBindInProgress 
> 37	17.920316	13.198.98.107	13.198.98.35	LDAP	bindRequest(3) "<ROOT>" sasl 
> 38	17.920691	13.198.98.35	13.198.98.107	LDAP	bindResponse(3) success 
> ========================================
> I am not sure if packet 35 is normal or not? After all, it says the packet is malformed.
>
> In contrast, a trace captured with OpenLDAP ldapsearch utility does not have this malformat packet: 
> ========================================
> 22	24.805633	13.198.98.35	13.198.98.190	LDAP	bindResponse(1) saslBindInProgress 
> 28	26.616093	13.198.98.190	13.198.98.35	LDAP	bindRequest(2) "<ROOT>" sasl 
> 29	26.616459	13.198.98.35	13.198.98.190	LDAP	bindResponse(2) saslBindInProgress 
> 31	26.616705	13.198.98.190	13.198.98.35	LDAP	bindRequest(3) "<ROOT>" sasl 
> 32	26.633134	13.198.98.35	13.198.98.190	LDAP	bindResponse(3) success 
> ========================================
> As you know, SASL connection relies on SASL library like libsasl2.so, which depends on OpenLDAP libraries such as libldap-2.3.so and liblber-2.3.so (this can be verfified by "ldd libsasl2.so"). And I am not sure whether there is some conflict between MozLDAP and OpenLDAP when MozLDAP calls SASL interfaces in libsasl2.so to do SASL binding.
>
> This aside, when I compare the content of packet 35 in MozLDAP trace and packet 29 in OpenLDAP trace, it is noted that the MozLDAP packet has extra bytes "04 00" after "mechanism: GSSAPI". These extra bytes are interpreted as "<MISSING> credentials" by WireShark. In contrast, although the OpenLDAP packet doesn't have any credential information as well, it doesn't have these extra bytes. That's why packet 35 in MozLDAP trace is marked as Malformed Packet, while packet 29 in OpenLDAP trace is not.
>   
It looks as though MozLDAP is sending a zero length string for the 
credentials (4 is the BER tag for Octet String, the next byte is the 
length which is zero).  I would have to read the specs to see what it 
says about that, but it appears at least that Wireshark does not like 
it, and OpenLDAP does not do it, it just omits the credentials field 
entirely.  So I would say this is likely a bug in MozLDAP.
> Anyone can look into this matter? If you try some sasl connection and capture a network trace while doing sasl binding, you'll easily find the problem. 
>
> I myself have captured the traces, but it is understood that mailist doesn't welcome attachments. So if anybody wants to have a look at my trace, just let me know, and I'll send you in separate mail.
>   
I don't know if it is necessary, but you could use a pastebin to paste 
your traces, then just email a link to the traces.  Mozilla has a 
pastebin at http://pastebin.mozilla.org/
> Thanks, 
> Xu Qiang