Re: back-ldap assertion failure, LDAP proxy to Windows AD

You should probably file an ITS...

p.

We encountered a back-ldap assertion failure with the back-ldap as a proxy to a remote Active Directory on Windows 2003 R2. The assertion failure occurred when the slapd server was checking ACLs via the rwm overlay. Snippet of the stack trace:

Thread 1 (Thread 32267): .... #2 0x0000003c354296e6 in __assert_fail () from /lib64/libc.so.6 #3 0x00002ac57daaf6c1 in ldap_back_dobind_int (lcp=0x42f70170, op=0x42f702f0, rs=0x42f700a0, sendok=LDAP_BACK_GETCONN, retries=0, dolock=1) at /home/build/sol-2.4.23.101221/sol24x/ldap24/servers/slapd/back-ldap/bind.c:1389 #4 0x00002ac57daafda0 in ldap_back_dobind (lcp=0x42f70170, op=0x42f702f0, rs=0x42f700a0, sendok=LDAP_BACK_DONTSEND) at /home/build/sol-2.4.23.101221/sol24x/ldap24/servers/slapd/back-ldap/bind.c:1572 #5 0x00002ac57daac7a7 in ldap_back_entry_get (op=0x42f702f0, ndn=0x42f701d0, oc=0x0, at=0x135ad370, rw=0, ent=0x42f70a58)

Analysis of the assertion failure:

The ldap_back_entry_get() function, back-ldap/search.c, is called for ACL entries, via rwm overlay. The function sets op->o_do_not_cache to 1 before calling into ldap_back_dobind():

    /* Tell getconn this is a privileged op */
    do_not_cache = op->o_do_not_cache;
    tag = op->o_tag;
    /* do not cache */
    op->o_do_not_cache = 1;
    /* ldap_back_entry_get() is an entry lookup, so it does not need
     * to know what the entry is being looked up for */
    op->o_tag = LDAP_REQ_SEARCH;
    rc = ldap_back_dobind( &lc, op, &rs, LDAP_BACK_DONTSEND );

The ldap_back_dobind() function calls ldap_back_dobind_int() for bind, back-ldap/bind.c. The following ldap_back_dobind_int() code is destined for assertion failure, if op->o_do_not_cache flag is set and there is no valid binddn and bindcred returned by ldap_back_getconn(). Setting an invalid LDAP URI for the remote AD Windows box is such a case.

ldap_back_dobind_int(…) { ... if (sendok & LDAP_BACK_GETCONN) { … lc = ldap_back_getconn(op, rs, sendoff, &binddn, &bindcred); ... }

if ( LDAP_BACK_CONN_ISIDASSERT( lc ) ) {
	if ( BER_BVISEMPTY( &binddn ) && BER_BVISEMPTY( &bindcred ) ) {
		/* if we got here, it shouldn't return result */
		rc = ldap_back_is_proxy_authz( op, rs,
				LDAP_BACK_DONTSEND, &binddn, &bindcred );

		/* ldap_back_is_proxy_authz always returns 0 when op->o_do_not_cache

is set, see below */ assert( rc == 1 );------> assertion failure } rc = ldap_back_proxy_authz_bind( lc, op, rs, sendok, &binddn, &bindcred ); … } }

When the op->o_do_not_cache flag is set, the ldap_back_is_proxy_authz() function always returns 0.

ldap_back_is_proxy_authz( ... ) { ... int dobind = 0;

if ( op->o_conn == NULL || op->o_do_not_cache ) {
	goto done;
}
...

done:; return dobind; <--- always returns 0 }

Ted C. Cheng Symas Corporation