s3:tldap: simplify read_ldap_more() by using asn1_peek_full_tag()

An LDAP pdu is at least 7 bytes long, so we read at least 7 bytes,
then it's easy to use asn1_peek_full_tag() in order to find out the
whole length of the pdu on one go.

As a side effect it's now possible that wireshark can reassemble
the fragments in a socket_wrapper generated pcap file.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

diff --git a/source3/lib/tldap.c b/source3/lib/tldap.c
index ad3232bf581a40630a388b153d391f8618e6fade..6e82516c273028da0ca717b4e29487325e57aa36 100644 (file)
--- a/source3/lib/tldap.c
+++ b/source3/lib/tldap.c
@@ -298,7 +298,6 @@ void *tldap_context_getattr(struct tldap_context *ld, const char *name)
 
 struct read_ldap_state {
        uint8_t *buf;
-       bool done;
 };
 
 static ssize_t read_ldap_more(uint8_t *buf, size_t buflen, void *private_data);
@@ -315,9 +314,8 @@ static struct tevent_req *read_ldap_send(TALLOC_CTX *mem_ctx,
        if (req == NULL) {
                return NULL;
        }
-       state->done = false;
 
-       subreq = tstream_read_packet_send(state, ev, conn, 2, read_ldap_more,
+       subreq = tstream_read_packet_send(state, ev, conn, 7, read_ldap_more,
                                          state);
        if (tevent_req_nomem(subreq, req)) {
                return tevent_req_post(req, ev);
@@ -328,48 +326,30 @@ static struct tevent_req *read_ldap_send(TALLOC_CTX *mem_ctx,
 
 static ssize_t read_ldap_more(uint8_t *buf, size_t buflen, void *private_data)
 {
-       struct read_ldap_state *state = talloc_get_type_abort(
-               private_data, struct read_ldap_state);
-       size_t len;
-       int i, lensize;
-
-       if (state->done) {
-               /* We've been here, we're done */
-               return 0;
-       }
+       const DATA_BLOB blob = data_blob_const(buf, buflen);
+       size_t pdu_len = 0;
+       int ret;
 
-       /*
-        * From ldap.h: LDAP_TAG_MESSAGE is 0x30
-        */
-       if (buf[0] != 0x30) {
+       if (buflen < 7) {
+               /*
+                * We need at least 6 bytes to workout the length
+                * of the pdu.
+                *
+                * And we have asked for 7 because the that's
+                * the size of the smallest possible LDAP pdu.
+                */
                return -1;
        }
 
-       len = buf[1];
-       if ((len & 0x80) == 0) {
-               state->done = true;
-               return len;
-       }
-
-       lensize = (len & 0x7f);
-       len = 0;
-
-       if (buflen == 2) {
-               /* Please get us the full length */
-               return lensize;
-       }
-       if (buflen > 2 + lensize) {
-               state->done = true;
+       ret = asn1_peek_full_tag(blob, ASN1_SEQUENCE(0), &pdu_len);
+       if (ret == 0) {
                return 0;
        }
-       if (buflen != 2 + lensize) {
-               return -1;
+       if (ret == EAGAIN) {
+               return pdu_len - buflen;
        }
 
-       for (i=0; i<lensize; i++) {
-               len = (len << 8) | buf[2+i];
-       }
-       return len;
+       return -1;
 }
 
 static void read_ldap_done(struct tevent_req *subreq)