From: Emmanuel T Odeke <emmanuel@orijtech.com>
Date: Tue, 26 May 2020 21:14:08 +0000 (-0700)
Subject: net/mail: avoid ParseDate confusion if day name includes "T"
X-Git-Tag: go1.16beta1~327
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=3ef8562c9c2c7f6897572b05b70ac936a99fd043;p=gostls13.git

net/mail: avoid ParseDate confusion if day name includes "T"

Fixes the check for RFC 5322 "obsolete time zone" to ensure
that we correctly extract the entire date from the "T" of the
implied time zone.

Obsolete Time zones come in the form:
* GMT
* PST
* MDT
etc, as per Section 4.3 of RFC 5322,
https://tools.ietf.org/html/rfc5322#section-4.3.

The prior check from CL 117596 erronenously used strings.Index
which selects the first "T", and that meant that dates containing
days "Tue" or "Thu" could not be parsed.

We also now deal with "T" in the CFWS "Comment Folding White Space".

Thus we'll now accept dates:
* Thu, 20 Nov 1997 09:55:06 MDT
* Thu, 20 Nov 1997 09:55:06 MDT (MDT)
* Fri, 21 Nov 1997 09:55:06 MDT (This comment)
* Fri, 21 Nov 1997 09:55:06 MDT (MDT

Fixes #39260

Change-Id: I6d59d99bc4f05a82582c826b5c5a080a25fd999b
Reviewed-on: https://go-review.googlesource.com/c/go/+/235200
Run-TryBot: Emmanuel Odeke <emmanuel@orijtech.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
---

diff --git a/src/net/mail/message.go b/src/net/mail/message.go
index 09fb794005..47bbf6ca97 100644
--- a/src/net/mail/message.go
+++ b/src/net/mail/message.go
@@ -112,11 +112,25 @@ func ParseDate(date string) (time.Time, error) {
 	if ind := strings.IndexAny(p.s, "+-"); ind != -1 && len(p.s) >= ind+5 {
 		date = p.s[:ind+5]
 		p.s = p.s[ind+5:]
-	} else if ind := strings.Index(p.s, "T"); ind != -1 && len(p.s) >= ind+1 {
-		// The last letter T of the obsolete time zone is checked when no standard time zone is found.
-		// If T is misplaced, the date to parse is garbage.
-		date = p.s[:ind+1]
-		p.s = p.s[ind+1:]
+	} else {
+		ind := strings.Index(p.s, "T")
+		if ind == 0 {
+			// In this case we have the following date formats:
+			// * Thu, 20 Nov 1997 09:55:06 MDT
+			// * Thu, 20 Nov 1997 09:55:06 MDT (MDT)
+			// * Thu, 20 Nov 1997 09:55:06 MDT (This comment)
+			ind = strings.Index(p.s[1:], "T")
+			if ind != -1 {
+				ind++
+			}
+		}
+
+		if ind != -1 && len(p.s) >= ind+5 {
+			// The last letter T of the obsolete time zone is checked when no standard time zone is found.
+			// If T is misplaced, the date to parse is garbage.
+			date = p.s[:ind+1]
+			p.s = p.s[ind+1:]
+		}
 	}
 	if !p.skipCFWS() {
 		return time.Time{}, errors.New("mail: misformatted parenthetical comment")
diff --git a/src/net/mail/message_test.go b/src/net/mail/message_test.go
index 188d0bf766..0daa3d6c63 100644
--- a/src/net/mail/message_test.go
+++ b/src/net/mail/message_test.go
@@ -102,6 +102,18 @@ func TestDateParsing(t *testing.T) {
 			"Fri, 21 Nov 1997 09:55:06 -0600 (MDT)",
 			time.Date(1997, 11, 21, 9, 55, 6, 0, time.FixedZone("", -6*60*60)),
 		},
+		{
+			"Thu, 20 Nov 1997 09:55:06 -0600 (MDT)",
+			time.Date(1997, 11, 20, 9, 55, 6, 0, time.FixedZone("", -6*60*60)),
+		},
+		{
+			"Thu, 20 Nov 1997 09:55:06 MDT (MDT)",
+			time.Date(1997, 11, 20, 9, 55, 6, 0, time.FixedZone("MDT", 0)),
+		},
+		{
+			"Fri, 21 Nov 1997 09:55:06 +1300 (TOT)",
+			time.Date(1997, 11, 21, 9, 55, 6, 0, time.FixedZone("", +13*60*60)),
+		},
 	}
 	for _, test := range tests {
 		hdr := Header{
@@ -243,6 +255,33 @@ func TestDateParsingCFWS(t *testing.T) {
 			time.Date(1997, 11, 21, 9, 55, 6, 0, time.FixedZone("", -6*60*60)),
 			false,
 		},
+		// Ensure that the presence of "T" in the date
+		// doesn't trip out ParseDate, as per issue 39260.
+		{
+			"Tue, 26 May 2020 14:04:40 GMT",
+			time.Date(2020, 05, 26, 14, 04, 40, 0, time.UTC),
+			true,
+		},
+		{
+			"Tue, 26 May 2020 14:04:40 UT",
+			time.Date(2020, 05, 26, 14, 04, 40, 0, time.UTC),
+			false,
+		},
+		{
+			"Thu, 21 May 2020 14:04:40 UT",
+			time.Date(2020, 05, 21, 14, 04, 40, 0, time.UTC),
+			false,
+		},
+		{
+			"Thu, 21 May 2020 14:04:40 UTC",
+			time.Date(2020, 05, 21, 14, 04, 40, 0, time.UTC),
+			true,
+		},
+		{
+			"Fri, 21 Nov 1997 09:55:06 MDT (MDT)",
+			time.Date(1997, 11, 21, 9, 55, 6, 0, time.FixedZone("MDT", 0)),
+			true,
+		},
 	}
 	for _, test := range tests {
 		hdr := Header{