From e55d4d9859a942415994cbbb506006f674012345 Mon Sep 17 00:00:00 2001
From: Robert Sesek <rsesek@bluestatic.org>
Date: Wed, 14 Dec 2016 00:52:14 -0500
Subject: [PATCH] Handle case-insensitivity properly for SMTP commands.

---
 smtp/conn.go      | 31 ++++++++++++++++++++++---------
 smtp/conn_test.go | 24 ++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 9 deletions(-)

diff --git a/smtp/conn.go b/smtp/conn.go
index c379484..3485894 100644
--- a/smtp/conn.go
+++ b/smtp/conn.go
@@ -5,6 +5,7 @@ import (
 	"net"
 	"net/mail"
 	"net/textproto"
+	"strings"
 )
 
 type state int
@@ -56,7 +57,7 @@ func AcceptConnection(netConn net.Conn, server Server) error {
 			continue
 		}
 
-		switch cmd {
+		switch strings.ToUpper(cmd) {
 		case "QUIT":
 			conn.writeReply(221, "Goodbye")
 			conn.tp.Close()
@@ -101,6 +102,19 @@ func (conn *connection) writeReply(code int, msg string) {
 	}
 }
 
+// parsePath parses out either a forward-, reverse-, or return-path from the
+// current connection line. Returns a (valid-path, ReplyOK) if it was
+// successfully parsed.
+func (conn *connection) parsePath(command string) (string, ReplyLine) {
+	if len(conn.line) < len(command) {
+		return "", ReplyBadSyntax
+	}
+	if strings.ToUpper(command) != strings.ToUpper(conn.line[:len(command)]) {
+		return "", ReplyLine{500, "unrecognized command"}
+	}
+	return conn.line[len(command):], ReplyOK
+}
+
 func (conn *connection) doEHLO() {
 	conn.resetBuffers()
 
@@ -130,13 +144,13 @@ func (conn *connection) doMAIL() {
 		return
 	}
 
-	var mailFrom string
-	_, err := fmt.Sscanf(conn.line, "MAIL FROM:%s", &mailFrom)
-	if err != nil {
-		conn.reply(ReplyBadSyntax)
+	mailFrom, reply := conn.parsePath("MAIL FROM:")
+	if reply != ReplyOK {
+		conn.reply(reply)
 		return
 	}
 
+	var err error
 	conn.mailFrom, err = mail.ParseAddress(mailFrom)
 	if err != nil {
 		conn.reply(ReplyBadSyntax)
@@ -153,10 +167,9 @@ func (conn *connection) doRCPT() {
 		return
 	}
 
-	var rcptTo string
-	_, err := fmt.Sscanf(conn.line, "RCPT TO:%s", &rcptTo)
-	if err != nil {
-		conn.reply(ReplyBadSyntax)
+	rcptTo, reply := conn.parsePath("RCPT TO:")
+	if reply != ReplyOK {
+		conn.reply(reply)
 		return
 	}
 
diff --git a/smtp/conn_test.go b/smtp/conn_test.go
index 5aa5234..32ca484 100644
--- a/smtp/conn_test.go
+++ b/smtp/conn_test.go
@@ -164,3 +164,27 @@ func TestVerifyAddress(t *testing.T) {
 		{"QUIT", 221, nil},
 	})
 }
+
+func TestCaseSensitivty(t *testing.T) {
+	s := &testServer{}
+	l := runServer(t, s)
+	defer l.Close()
+
+	conn := createClient(t, l.Addr())
+	readCodeLine(t, conn, 220)
+
+	runTableTest(t, conn, []requestResponse{
+		{"nOoP", 250, nil},
+		{"ehLO test.TEST", 0, func(t testing.TB, conn *textproto.Conn) { conn.ReadResponse(250) }},
+		{"mail FROM:<sender@example.com>", 250, nil},
+		{"RcPT tO:<receive@mail.com>", 250, nil},
+		{"DATa", 0, func(t testing.TB, conn *textproto.Conn) {
+			readCodeLine(t, conn, 354)
+
+			ok(t, conn.PrintfLine("."))
+			readCodeLine(t, conn, 250)
+		}},
+		{"MAIL FR:", 501, nil},
+		{"QUiT", 221, nil},
+	})
+}
-- 
2.22.5