r17197: This patch moves the encryption of bulk data on SASL negotiated security

contexts from the application layer into the socket layer.

This improves a number of correctness aspects, as we now allow LDAP
packets to cross multiple SASL packets.  It should also make it much
easier to write async LDAP tests from windows clients, as they use SASL
by default.  It is also vital to allowing OpenLDAP clients to use GSSAPI
against Samba4, as it negotiates a rather small SASL buffer size.

This patch mirrors the earlier work done to move TLS into the socket
layer.

Unusual in this pstch is the extra read callback argument I take.  As
SASL is a layer on top of a socket, it is entirely possible for the
SASL layer to drain a socket dry, but for the caller not to have read
all the decrypted data.  This would leave the system without an event
to restart the read (as the socket is dry).

As such, I re-invoke the read handler from a timed callback, which
should trigger on the next running of the event loop.  I believe that
the TLS code does require a similar callback.

In trying to understand why this is required, imagine a SASL-encrypted
LDAP packet in the following formation:

+-----------------+---------------------+
| SASL  Packet #1 | SASL Packet #2      |
----------------------------------------+
| LDAP Packet #1       | LDAP Packet #2 |
----------------------------------------+

In the old code, this was illegal, but it is perfectly standard
SASL-encrypted LDAP.  Without the callback, we would read and process
the first LDAP packet, and the SASL code would have read the second SASL
packet (to decrypt enough data for the LDAP packet), and no data would
remain on the socket.

Without data on the socket, read events stop.  That is why I add timed
events, until the SASL buffer is drained.

Another approach would be to add a hack to the event system, to have it
pretend there remained data to read off the network (but that is ugly).

In improving the code, to handle more real-world cases, I've been able
to remove almost all the special-cases in the testnonblock code.  The
only special case is that we must use a deterministic partial packet
when calling send, rather than a random length.  (1 + n/2).  This is
needed because of the way the SASL and TLS code works, and the 'resend
on failure' requirements.

Andrew Bartlett
(This used to be commit 5d7c9c12cb2b39673172a357092b80cd814850b0)

2 files changed, 35 insertions, 4 deletions

diff --git a/source4/lib/stream/packet.c b/source4/lib/stream/packet.c
index e06f4985ef..2759c75214 100644
--- a/source4/lib/stream/packet.c
+++ b/source4/lib/stream/packet.c
@@ -28,7 +28,6 @@
 #include "lib/socket/socket.h"
 #include "lib/stream/packet.h"
 
-
 struct packet_context {
 	packet_callback_fn_t callback;
 	packet_full_request_fn_t full_request;
@@ -53,6 +52,8 @@ struct packet_context {
 		struct send_element *next, *prev;
 		DATA_BLOB blob;
 		size_t nsent;
+		packet_send_callback_fn_t send_callback;
+		void *send_callback_private;
 	} *send_queue;
 };
 
@@ -374,6 +375,7 @@ next_partial:
 		return;
 	}
 
+	/* Have we consumed the whole buffer yet? */
 	if (pc->partial.length == 0) {
 		return;
 	}
@@ -436,7 +438,7 @@ _PUBLIC_ void packet_queue_run(struct packet_context *pc)
 		status = socket_send(pc->sock, &blob, &nwritten);
 
 		if (NT_STATUS_IS_ERR(status)) {
-			packet_error(pc, NT_STATUS_NET_WRITE_FAULT);
+			packet_error(pc, status);
 			return;
 		}
 		if (!NT_STATUS_IS_OK(status)) {
@@ -445,6 +447,9 @@ _PUBLIC_ void packet_queue_run(struct packet_context *pc)
 		el->nsent += nwritten;
 		if (el->nsent == el->blob.length) {
 			DLIST_REMOVE(pc->send_queue, el);
+			if (el->send_callback) {
+				el->send_callback(el->send_callback_private);
+			}
 			talloc_free(el);
 		}
 	}
@@ -455,9 +460,15 @@ _PUBLIC_ void packet_queue_run(struct packet_context *pc)
 }
 
 /*
-  put a packet in the send queue
+  put a packet in the send queue.  When the packet is actually sent,
+  call send_callback.  
+
+  Useful for operations that must occour after sending a message, such
+  as the switch to SASL encryption after as sucessful LDAP bind relpy.
 */
-_PUBLIC_ NTSTATUS packet_send(struct packet_context *pc, DATA_BLOB blob)
+_PUBLIC_ NTSTATUS packet_send_callback(struct packet_context *pc, DATA_BLOB blob,
+				       packet_send_callback_fn_t send_callback, 
+				       void *private)
 {
 	struct send_element *el;
 	el = talloc(pc, struct send_element);
@@ -466,6 +477,8 @@ _PUBLIC_ NTSTATUS packet_send(struct packet_context *pc, DATA_BLOB blob)
 	DLIST_ADD_END(pc->send_queue, el, struct send_element *);
 	el->blob = blob;
 	el->nsent = 0;
+	el->send_callback = send_callback;
+	el->send_callback_private = private;
 
 	/* if we aren't going to free the packet then we must reference it
 	   to ensure it doesn't disappear before going out */
@@ -477,11 +490,23 @@ _PUBLIC_ NTSTATUS packet_send(struct packet_context *pc, DATA_BLOB blob)
 		talloc_steal(el, blob.data);
 	}
 
+	if (private && !talloc_reference(el, private)) {
+		return NT_STATUS_NO_MEMORY;
+	}
+
 	EVENT_FD_WRITEABLE(pc->fde);
 
 	return NT_STATUS_OK;
 }
 
+/*
+  put a packet in the send queue
+*/
+_PUBLIC_ NTSTATUS packet_send(struct packet_context *pc, DATA_BLOB blob)
+{
+	return packet_send_callback(pc, blob, NULL, NULL);
+}
+
 
 /*
   a full request checker for NBT formatted packets (first 3 bytes are length)
diff --git a/source4/lib/stream/packet.h b/source4/lib/stream/packet.h
index b7ee428186..0d875d777c 100644
--- a/source4/lib/stream/packet.h
+++ b/source4/lib/stream/packet.h
@@ -24,6 +24,9 @@
 typedef NTSTATUS (*packet_full_request_fn_t)(void *private, 
 					     DATA_BLOB blob, size_t *packet_size);
 typedef NTSTATUS (*packet_callback_fn_t)(void *private, DATA_BLOB blob);
+
+/* Used to notify that a packet has been sent, and is on the wire */
+typedef void (*packet_send_callback_fn_t)(void *private);
 typedef void (*packet_error_handler_fn_t)(void *private, NTSTATUS status);
 
 
@@ -43,6 +46,9 @@ void packet_recv(struct packet_context *pc);
 void packet_recv_disable(struct packet_context *pc);
 void packet_recv_enable(struct packet_context *pc);
 NTSTATUS packet_send(struct packet_context *pc, DATA_BLOB blob);
+NTSTATUS packet_send_callback(struct packet_context *pc, DATA_BLOB blob,
+			      packet_send_callback_fn_t send_callback, 
+			      void *private);
 void packet_queue_run(struct packet_context *pc);
 
 /*