Add a new implementation of chain_reply

This the global variable "orig_inbuf" in the old chain_reply code. This global
variable was one of the reasons why we had the silly restriction to not allow
async requests within a request chain.

2 files changed, 217 insertions, 6 deletions

diff --git a/source3/smbd/blocking.c b/source3/smbd/blocking.c
index cccc5ce727..9936fb219f 100644
--- a/source3/smbd/blocking.c
+++ b/source3/smbd/blocking.c
@@ -238,12 +238,6 @@ static void reply_lockingX_success(blocking_lock_record *blr)
 	 */
 
 	chain_reply(blr->req);
-
-	if (!srv_send_smb(smbd_server_fd(), (char *)blr->req->outbuf,
-			IS_CONN_ENCRYPTED(blr->fsp->conn))) {
-		exit_server_cleanly("send_blocking_reply: srv_send_smb failed.");
-	}
-
 	TALLOC_FREE(blr->req->outbuf);
 }
 
diff --git a/source3/smbd/process.c b/source3/smbd/process.c
index 60e58aac22..3547bfcc3a 100644
--- a/source3/smbd/process.c
+++ b/source3/smbd/process.c
@@ -372,6 +372,7 @@ void init_smb_request(struct smb_request *req,
 	req->encrypted = encrypted;
 	req->conn = conn_find(req->tid);
 	req->chain_fsp = NULL;
+	req->chain_outbuf = NULL;
 
 	/* Ensure we have at least wct words and 2 bytes of bcc. */
 	if (smb_size + req->wct*2 > req_size) {
@@ -1613,6 +1614,8 @@ void construct_reply_common_req(struct smb_request *req, char *outbuf)
  Construct a chained reply and add it to the already made reply
 ****************************************************************************/
 
+#if 0
+
 void chain_reply(struct smb_request *req)
 {
 	/*
@@ -1817,6 +1820,220 @@ void chain_reply(struct smb_request *req)
 	return;
 }
 
+#else
+
+/*
+ * Hack around reply_nterror & friends not being aware of chained requests,
+ * generating illegal (i.e. wct==0) chain replies.
+ */
+
+static void fixup_chain_error_packet(struct smb_request *req)
+{
+	uint8_t *outbuf = req->outbuf;
+	req->outbuf = NULL;
+	reply_outbuf(req, 2, 0);
+	memcpy(req->outbuf, outbuf, smb_wct);
+	TALLOC_FREE(outbuf);
+	SCVAL(req->outbuf, smb_vwv0, 0xff);
+}
+
+void chain_reply(struct smb_request *req)
+{
+	size_t smblen = smb_len(req->inbuf);
+	size_t already_used, length_needed;
+	uint8_t chain_cmd;
+	uint32_t chain_offset;	/* uint32_t to avoid overflow */
+
+	uint8_t wct;
+	uint16_t *vwv;
+	uint16_t buflen;
+	uint8_t *buf;
+
+	if (IVAL(req->outbuf, smb_rcls) != 0) {
+		fixup_chain_error_packet(req);
+	}
+
+	/*
+	 * Any of the AndX requests and replies have at least a wct of
+	 * 2. vwv[0] is the next command, vwv[1] is the offset from the
+	 * beginning of the SMB header to the next wct field.
+	 *
+	 * None of the AndX requests put anything valuable in vwv[0] and [1],
+	 * so we can overwrite it here to form the chain.
+	 */
+
+	if ((req->wct < 2) || (CVAL(req->outbuf, smb_wct) < 2)) {
+		goto error;
+	}
+
+	/*
+	 * Here we assume that this is the end of the chain. For that we need
+	 * to set "next command" to 0xff and the offset to 0. If we later find
+	 * more commands in the chain, this will be overwritten again.
+	 */
+
+	SCVAL(req->outbuf, smb_vwv0, 0xff);
+	SCVAL(req->outbuf, smb_vwv0+1, 0);
+	SSVAL(req->outbuf, smb_vwv1, 0);
+
+	if (req->chain_outbuf == NULL) {
+		/*
+		 * In req->chain_outbuf we collect all the replies. Start the
+		 * chain by copying in the first reply.
+		 */
+		req->chain_outbuf = req->outbuf;
+		req->outbuf = NULL;
+	} else {
+		if (!smb_splice_chain(&req->chain_outbuf,
+				      CVAL(req->outbuf, smb_com),
+				      CVAL(req->outbuf, smb_wct),
+				      (uint16_t *)(req->outbuf + smb_vwv),
+				      0, smb_buflen(req->outbuf),
+				      (uint8_t *)smb_buf(req->outbuf))) {
+			goto error;
+		}
+		TALLOC_FREE(req->outbuf);
+	}
+
+	/*
+	 * We use the old request's vwv field to grab the next chained command
+	 * and offset into the chained fields.
+	 */
+
+	chain_cmd = CVAL(req->vwv+0, 0);
+	chain_offset = SVAL(req->vwv+1, 0);
+
+	if (chain_cmd == 0xff) {
+		/*
+		 * End of chain, no more requests from the client. So ship the
+		 * replies.
+		 */
+		smb_setlen((char *)(req->chain_outbuf),
+			   talloc_get_size(req->chain_outbuf) - 4);
+		if (!srv_send_smb(smbd_server_fd(), (char *)req->chain_outbuf,
+				  IS_CONN_ENCRYPTED(req->conn)
+				  ||req->encrypted)) {
+			exit_server_cleanly("chain_reply: srv_send_smb "
+					    "failed.");
+		}
+		return;
+	}
+
+	/*
+	 * Check if the client tries to fool us. The request so far uses the
+	 * space to the end of the byte buffer in the request just
+	 * processed. The chain_offset can't point into that area. If that was
+	 * the case, we could end up with an endless processing of the chain,
+	 * we would always handle the same request.
+	 */
+
+	already_used = PTR_DIFF(req->buf+req->buflen, smb_base(req->inbuf));
+	if (chain_offset < already_used) {
+		goto error;
+	}
+
+	/*
+	 * Next check: Make sure the chain offset does not point beyond the
+	 * overall smb request length.
+	 */
+
+	length_needed = chain_offset+1;	/* wct */
+	if (length_needed > smblen) {
+		goto error;
+	}
+
+	/*
+	 * Now comes the pointer magic. Goal here is to set up req->vwv and
+	 * req->buf correctly again to be able to call the subsequent
+	 * switch_message(). The chain offset (the former vwv[1]) points at
+	 * the new wct field.
+	 */
+
+	wct = CVAL(smb_base(req->inbuf), chain_offset);
+
+	/*
+	 * Next consistency check: Make the new vwv array fits in the overall
+	 * smb request.
+	 */
+
+	length_needed += (wct+1)*sizeof(uint16_t); /* vwv+buflen */
+	if (length_needed > smblen) {
+		goto error;
+	}
+	vwv = (uint16_t *)(smb_base(req->inbuf) + chain_offset + 1);
+
+	/*
+	 * Now grab the new byte buffer....
+	 */
+
+	buflen = SVAL(vwv+wct, 0);
+
+	/*
+	 * .. and check that it fits.
+	 */
+
+	length_needed += buflen;
+	if (length_needed > smblen) {
+		goto error;
+	}
+	buf = (uint8_t *)(vwv+wct+1);
+
+	req->cmd = chain_cmd;
+	req->wct = wct;
+	req->vwv = vwv;
+	req->buflen = buflen;
+	req->buf = buf;
+
+	switch_message(chain_cmd, req, smblen);
+
+	if (req->outbuf == NULL) {
+		/*
+		 * This happens if the chained command has suspended itself or
+		 * if it has called srv_send_smb() itself.
+		 */
+		return;
+	}
+
+	/*
+	 * We end up here if the chained command was not itself chained or
+	 * suspended, but for example a close() command. We now need to splice
+	 * the chained commands' outbuf into the already built up chain_outbuf
+	 * and ship the result.
+	 */
+	goto done;
+
+ error:
+	/*
+	 * We end up here if there's any error in the chain syntax. Report a
+	 * DOS error, just like Windows does.
+	 */
+	reply_nterror(req, NT_STATUS_DOS(ERRSRV, ERRerror));
+	fixup_chain_error_packet(req);
+
+ done:
+	if (!smb_splice_chain(&req->chain_outbuf,
+			      CVAL(req->outbuf, smb_com),
+			      CVAL(req->outbuf, smb_wct),
+			      (uint16_t *)(req->outbuf + smb_vwv),
+			      0, smb_buflen(req->outbuf),
+			      (uint8_t *)smb_buf(req->outbuf))) {
+		exit_server_cleanly("chain_reply: smb_splice_chain failed\n");
+	}
+	TALLOC_FREE(req->outbuf);
+
+	smb_setlen((char *)(req->chain_outbuf),
+		   talloc_get_size(req->chain_outbuf) - 4);
+
+	show_msg((char *)(req->chain_outbuf));
+
+	if (!srv_send_smb(smbd_server_fd(), (char *)req->chain_outbuf,
+			  IS_CONN_ENCRYPTED(req->conn)||req->encrypted)) {
+		exit_server_cleanly("construct_reply: srv_send_smb failed.");
+	}
+}
+
+#endif
+
 /****************************************************************************
  Check if services need reloading.
 ****************************************************************************/