gh-75171: Fix parsing invalid email address headers starting or ending with a dot (GH-15600)

Co-authored-by: Tim Bell <timothybell@gmail.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

1 files changed, 14 insertions, 5 deletions

diff --git a/Lib/email/_header_value_parser.py b/Lib/email/_header_value_parser.py
index e4a342d..0cf23fc 100644
--- a/Lib/email/_header_value_parser.py
+++ b/Lib/email/_header_value_parser.py
@@ -566,12 +566,14 @@ class DisplayName(Phrase):
         if res[0].token_type == 'cfws':
             res.pop(0)
         else:
-            if res[0][0].token_type == 'cfws':
+            if (isinstance(res[0], TokenList) and
+                    res[0][0].token_type == 'cfws'):
                 res[0] = TokenList(res[0][1:])
         if res[-1].token_type == 'cfws':
             res.pop()
         else:
-            if res[-1][-1].token_type == 'cfws':
+            if (isinstance(res[-1], TokenList) and
+                    res[-1][-1].token_type == 'cfws'):
                 res[-1] = TokenList(res[-1][:-1])
         return res.value
 
@@ -586,9 +588,13 @@ class DisplayName(Phrase):
                     quote = True
         if len(self) != 0 and quote:
             pre = post = ''
-            if self[0].token_type=='cfws' or self[0][0].token_type=='cfws':
+            if (self[0].token_type == 'cfws' or
+                isinstance(self[0], TokenList) and
+                self[0][0].token_type == 'cfws'):
                 pre = ' '
-            if self[-1].token_type=='cfws' or self[-1][-1].token_type=='cfws':
+            if (self[-1].token_type == 'cfws' or
+                isinstance(self[-1], TokenList) and
+                self[-1][-1].token_type == 'cfws'):
                 post = ' '
             return pre+quote_string(self.display_name)+post
         else:
@@ -1772,7 +1778,10 @@ def get_name_addr(value):
             raise errors.HeaderParseError(
                 "expected name-addr but found '{}'".format(token))
         if leader is not None:
-            token[0][:0] = [leader]
+            if isinstance(token[0], TokenList):
+                token[0][:0] = [leader]
+            else:
+                token[:0] = [leader]
             leader = None
         name_addr.append(token)
     token, value = get_angle_addr(value)