From 2779fe7c10c172281e18e5133c4fb23634e62b2a Mon Sep 17 00:00:00 2001
From: Shivaram Lingamneni <slingamn@cs.stanford.edu>
Date: Thu, 14 May 2020 12:58:49 -0400
Subject: [PATCH] fix #1005

---
 irc/client.go     | 11 ++++++++---
 irc/handlers.go   | 36 +++++++++++++++++++-----------------
 irc/utils/text.go | 14 ++++++++++++++
 3 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/irc/client.go b/irc/client.go
index 8465fa6b..a5cc0f8f 100644
--- a/irc/client.go
+++ b/irc/client.go
@@ -175,7 +175,7 @@ func (s *Session) EndMultilineBatch(label string) (batch MultilineBatch, err err
 	}
 	s.deferredFakelagCount = fakelagBill
 
-	if batch.label == "" || batch.label != label || batch.message.LenLines() == 0 {
+	if batch.label == "" || batch.label != label || !batch.message.ValidMultiline() {
 		err = errInvalidMultilineBatch
 		return
 	}
@@ -1357,9 +1357,14 @@ func (session *Session) sendSplitMsgFromClientInternal(blocking bool, nickmask,
 				session.SendRawMessage(msg, blocking)
 			}
 		} else {
-			for i, messagePair := range message.Split {
+			msgidSent := false // send msgid on the first nonblank line
+			for _, messagePair := range message.Split {
+				if len(messagePair.Message) == 0 {
+					continue
+				}
 				var msgid string
-				if i == 0 {
+				if !msgidSent {
+					msgidSent = true
 					msgid = message.Msgid
 				}
 				session.sendFromClientInternal(blocking, message.Time, msgid, nickmask, accountName, tags, command, target, messagePair.Message)
diff --git a/irc/handlers.go b/irc/handlers.go
index 4427bdf9..c6745d95 100644
--- a/irc/handlers.go
+++ b/irc/handlers.go
@@ -1793,33 +1793,35 @@ func nickHandler(server *Server, client *Client, msg ircmsg.IrcMessage, rb *Resp
 
 // helper to store a batched PRIVMSG in the session object
 func absorbBatchedMessage(server *Server, client *Client, msg ircmsg.IrcMessage, batchTag string, histType history.ItemType, rb *ResponseBuffer) {
+	var errorCode, errorMessage string
+	defer func() {
+		if errorCode != "" {
+			if histType != history.Notice {
+				rb.Add(nil, server.name, "FAIL", "BATCH", errorCode, errorMessage)
+			}
+			rb.session.EndMultilineBatch("")
+		}
+	}()
+
 	if batchTag != rb.session.batch.label {
-		if histType != history.Notice {
-			rb.Add(nil, server.name, "FAIL", "BATCH", "MULTILINE_INVALID", client.t("Incorrect batch tag sent"))
-		}
-		rb.session.EndMultilineBatch("")
+		errorCode, errorMessage = "MULTILINE_INVALID", client.t("Incorrect batch tag sent")
 		return
-	} else if len(msg.Params) < 2 || msg.Params[1] == "" {
-		if histType != history.Notice {
-			rb.Add(nil, server.name, "FAIL", "BATCH", "MULTILINE_INVALID", client.t("Invalid multiline batch"))
-		}
-		rb.session.EndMultilineBatch("")
+	} else if len(msg.Params) < 2 {
+		errorCode, errorMessage = "MULTILINE_INVALID", client.t("Invalid multiline batch")
 		return
 	}
 	rb.session.batch.command = msg.Command
 	isConcat, _ := msg.GetTag(caps.MultilineConcatTag)
+	if isConcat && len(msg.Params[1]) == 0 {
+		errorCode, errorMessage = "MULTILINE_INVALID", client.t("Cannot send a blank line with the multiline concat tag")
+		return
+	}
 	rb.session.batch.message.Append(msg.Params[1], isConcat)
 	config := server.Config()
 	if config.Limits.Multiline.MaxBytes < rb.session.batch.message.LenBytes() {
-		if histType != history.Notice {
-			rb.Add(nil, server.name, "FAIL", "BATCH", "MULTILINE_MAX_BYTES", strconv.Itoa(config.Limits.Multiline.MaxBytes))
-		}
-		rb.session.EndMultilineBatch("")
+		errorCode, errorMessage = "MULTILINE_MAX_BYTES", strconv.Itoa(config.Limits.Multiline.MaxBytes)
 	} else if config.Limits.Multiline.MaxLines != 0 && config.Limits.Multiline.MaxLines < rb.session.batch.message.LenLines() {
-		if histType != history.Notice {
-			rb.Add(nil, server.name, "FAIL", "BATCH", "MULTILINE_MAX_LINES", strconv.Itoa(config.Limits.Multiline.MaxLines))
-		}
-		rb.session.EndMultilineBatch("")
+		errorCode, errorMessage = "MULTILINE_MAX_LINES", strconv.Itoa(config.Limits.Multiline.MaxLines)
 	}
 }
 
diff --git a/irc/utils/text.go b/irc/utils/text.go
index 5d46b140..d77b88d4 100644
--- a/irc/utils/text.go
+++ b/irc/utils/text.go
@@ -73,10 +73,24 @@ func (sm *SplitMessage) LenBytes() (result int) {
 	}
 	for i := 0; i < len(sm.Split); i++ {
 		result += len(sm.Split[i].Message)
+		// bill for the joining newline if necessary
+		if i != 0 && !sm.Split[i].Concat {
+			result += 1
+		}
 	}
 	return
 }
 
+func (sm *SplitMessage) ValidMultiline() bool {
+	// must contain at least one nonblank line
+	for i := 0; i < len(sm.Split); i++ {
+		if len(sm.Split[i].Message) != 0 {
+			return true
+		}
+	}
+	return false
+}
+
 func (sm *SplitMessage) IsRestrictedCTCPMessage() bool {
 	if IsRestrictedCTCPMessage(sm.Message) {
 		return true