From c28e4a5160d3283b12514c7c28ed6e0a2a52271a Mon Sep 17 00:00:00 2001 From: Abhilash Raj Date: Sat, 7 Sep 2019 00:08:53 -0700 Subject: [3.5] bpo-37461: Fix infinite loop in parsing of specially crafted email headers (GH-14794) (#15446) * [3.5] bpo-37461: Fix infinite loop in parsing of specially crafted email headers (GH-14794) 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 Co-Authored-By: Ashwin Ramaswami --- 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 facc208..5c4eb75 100644 --- a/Lib/email/_header_value_parser.py +++ b/Lib/email/_header_value_parser.py @@ -2771,6 +2771,9 @@ 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 8ae617a..0cc5898 100644 --- a/Lib/test/test_email/test__header_value_parser.py +++ b/Lib/test/test_email/test__header_value_parser.py @@ -2573,6 +2573,13 @@ 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..9d47578 --- /dev/null +++ b/Misc/NEWS.d/next/Security/2019-07-16-08-11-00.bpo-37461.1Ahz7O.rst @@ -0,0 +1,2 @@ +Fix an infinite loop when parsing specially crafted email headers. Patch by +Abhilash Raj. -- cgit v0.12