From: Abhilash Raj <maxking@users.noreply.github.com>
Date: Mon, 9 Dec 2019 01:37:34 +0000 (-0800)
Subject: bpo-38708: email: Fix a potential IndexError when parsing Message-ID (GH-17504)
X-Git-Tag: v3.9.0a2~56
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=3ae4ea1931361dd2743e464790e739d9285501bf;p=thirdparty%2FPython%2Fcpython.git

bpo-38708: email: Fix a potential IndexError when parsing Message-ID (GH-17504)

Fix a potential IndexError when passing an empty value to the message-id
parser. Instead, HeaderParseError should be raised.
---

diff --git a/Lib/email/_header_value_parser.py b/Lib/email/_header_value_parser.py
index cb013225ec60..9c55ef7fb453 100644
--- a/Lib/email/_header_value_parser.py
+++ b/Lib/email/_header_value_parser.py
@@ -2047,7 +2047,7 @@ def get_msg_id(value):
        no-fold-literal = "[" *dtext "]"
     """
     msg_id = MsgID()
-    if value[0] in CFWS_LEADER:
+    if value and value[0] in CFWS_LEADER:
         token, value = get_cfws(value)
         msg_id.append(token)
     if not value or value[0] != '<':
diff --git a/Lib/test/test_email/test__header_value_parser.py b/Lib/test/test_email/test__header_value_parser.py
index d59d70117b81..1bdcfa129b4c 100644
--- a/Lib/test/test_email/test__header_value_parser.py
+++ b/Lib/test/test_email/test__header_value_parser.py
@@ -2583,6 +2583,11 @@ class TestParser(TestParserMixin, TestEmailBase):
 
     # get_msg_id
 
+    def test_get_msg_id_empty(self):
+        # bpo-38708: Test that HeaderParseError is raised and not IndexError.
+        with self.assertRaises(errors.HeaderParseError):
+            parser.get_msg_id('')
+
     def test_get_msg_id_valid(self):
         msg_id = self._test_get_x(
             parser.get_msg_id,
@@ -2694,6 +2699,7 @@ class TestParser(TestParserMixin, TestEmailBase):
         self.assertEqual(msg_id.token_type, 'msg-id')
 
 
+
 @parameterize
 class Test_parse_mime_parameters(TestParserMixin, TestEmailBase):
 
diff --git a/Misc/NEWS.d/next/Library/2019-12-07-22-25-39.bpo-38708.rZTUfk.rst b/Misc/NEWS.d/next/Library/2019-12-07-22-25-39.bpo-38708.rZTUfk.rst
new file mode 100644
index 000000000000..23a0a46d1fea
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-12-07-22-25-39.bpo-38708.rZTUfk.rst
@@ -0,0 +1 @@
+Fix a potential IndexError in email parser when parsing an empty msg-id.