From 6816ca30af7705db691343100e696ea3d8f447d5 Mon Sep 17 00:00:00 2001 From: "Miss Islington (bot)" <31488909+miss-islington@users.noreply.github.com> Date: Wed, 17 Jul 2019 10:13:54 -0700 Subject: bpo-37461: Fix infinite loop in parsing of specially crafted email headers (GH-14794) * bpo-37461: Fix infinite loop in parsing of specially crafted email headers. Some crafted email header would cause the get_parameter method to run in an infinite loop causing a DoS attack surface when parsing those headers. This patch fixes that by making sure the DQUOTE character is handled to prevent going into an infinite loop. (cherry picked from commit a4a994bd3e619cbaff97610a1cee8ffa87c672f5) Co-authored-by: Abhilash Raj --- Lib/email/_header_value_parser.py | 3 +++ Lib/test/test_email/test__header_value_parser.py | 7 +++++++ Misc/NEWS.d/next/Security/2019-07-16-08-11-00.bpo-37461.1Ahz7O.rst | 2 ++ 3 files changed, 12 insertions(+) create mode 100644 Misc/NEWS.d/next/Security/2019-07-16-08-11-00.bpo-37461.1Ahz7O.rst diff --git a/Lib/email/_header_value_parser.py b/Lib/email/_header_value_parser.py index 6475321..2fc8abc 100644 --- a/Lib/email/_header_value_parser.py +++ b/Lib/email/_header_value_parser.py @@ -2475,6 +2475,9 @@ def get_parameter(value): while value: if value[0] in WSP: token, value = get_fws(value) + elif value[0] == '"': + token = ValueTerminal('"', 'DQUOTE') + value = value[1:] else: token, value = get_qcontent(value) v.append(token) diff --git a/Lib/test/test_email/test__header_value_parser.py b/Lib/test/test_email/test__header_value_parser.py index 14d1ff3..6291749 100644 --- a/Lib/test/test_email/test__header_value_parser.py +++ b/Lib/test/test_email/test__header_value_parser.py @@ -2690,6 +2690,13 @@ class Test_parse_mime_parameters(TestParserMixin, TestEmailBase): # Defects are apparent missing *0*, and two 'out of sequence'. [errors.InvalidHeaderDefect]*3), + # bpo-37461: Check that we don't go into an infinite loop. + 'extra_dquote': ( + 'r*="\'a\'\\"', + ' r="\\""', + 'r*=\'a\'"', + [('r', '"')], + [errors.InvalidHeaderDefect]*2), } @parameterize diff --git a/Misc/NEWS.d/next/Security/2019-07-16-08-11-00.bpo-37461.1Ahz7O.rst b/Misc/NEWS.d/next/Security/2019-07-16-08-11-00.bpo-37461.1Ahz7O.rst new file mode 100644 index 0000000..4bfd350 --- /dev/null +++ b/Misc/NEWS.d/next/Security/2019-07-16-08-11-00.bpo-37461.1Ahz7O.rst @@ -0,0 +1,2 @@ +Fix an inifite loop when parsing specially crafted email headers. Patch by +Abhilash Raj. -- cgit v0.12