Hi, all:
As you know, although my SASL binding is successful, it still has some defect.
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]
Lightweight-Directory-Access-Protocol
LDAPMessage bindRequest(2) "<ROOT>"
messageID: 2
protocolOp: bindRequest (0)
bindRequest
version: 3
name:
authentication: sasl (3)
sasl
mechanism: GSSAPI
credentials: <MISSING>
[Malformed Packet: LDAP]
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. Luckily, it will not affect the result of SASL binding.
In contrast, a trace captured with OpenLDAP ldapsearch utility does not have
this malformat packet:
========================================
20 24.622555 13.198.98.190 13.198.98.35 LDAP bindRequest(1)
"<ROOT>" sasl
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
Lightweight-Directory-Access-Protocol
LDAPMessage bindRequest(2) "<ROOT>"
messageID: 2
protocolOp: bindRequest (0)
bindRequest
version: 3
name:
authentication: sasl (3)
sasl
mechanism: GSSAPI
[Response In: 29]
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
========================================
When I compare the content of packet 35 in MozLDAP trace and packet 28 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 28 in OpenLDAP trace is not.
Looking into the code of MozLDAP, I found the following is suspicous:
========================================
int
LDAP_CALL
ldap_sasl_bind(
LDAP *ld,
const char *dn,
const char *mechanism,
const struct berval *cred,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
int *msgidp
)
{
...
if ( cred == NULL ) {
rc = ber_printf( ber, "{it{ist{s}}", msgid,
LDAP_REQ_BIND, ldapversion, dn, LDAP_AUTH_SASL,
mechanism );
} else {
rc = ber_printf( ber, "{it{ist{so}}", msgid,
LDAP_REQ_BIND, ldapversion, dn, LDAP_AUTH_SASL,
mechanism, cred->bv_val,
cred->bv_len );
}
...
}
========================================
At the first look, it seem innocent. But...
Let's have a look at OpenLDAP's code as well:
========================================
int
ldap_sasl_bind(
LDAP *ld,
LDAP_CONST char *dn,
LDAP_CONST char *mechanism,
struct berval *cred,
LDAPControl **sctrls,
LDAPControl **cctrls,
int *msgidp )
{
...
if( mechanism == LDAP_SASL_SIMPLE ) {
/* simple bind */
rc = ber_printf( ber, "{it{istON}" /*}*/,
id, LDAP_REQ_BIND,
ld->ld_version, dn, LDAP_AUTH_SIMPLE,
cred );
} else if ( cred == NULL || cred->bv_val == NULL ) {
/* SASL bind w/o credentials */
rc = ber_printf( ber, "{it{ist{sN}N}" /*}*/,
id, LDAP_REQ_BIND,
ld->ld_version, dn, LDAP_AUTH_SASL,
mechanism );
} else {
/* SASL bind w/ credentials */
rc = ber_printf( ber, "{it{ist{sON}N}" /*}*/,
id, LDAP_REQ_BIND,
ld->ld_version, dn, LDAP_AUTH_SASL,
mechanism, cred );
}
...
}
========================================
Comparing both snippets of MozLDAP and OpenLDAP, I am wondering whether MozLDAP
should add the condition "|| cred->bv_val == NULL" to the already existing one
"if ( cred == NULL )" to decide whether to do SASL binding without explicit
credential.
I feel this is why there is Malformed Packet in MozLDAP SASL trace, but hope
someone in the list more familiar with the code can confirm.
Thanks,
Xu Qiang
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