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120 lines
4.8 KiB
120 lines
4.8 KiB
From f7fb35b563a9182c22fbdd03c72ec3724dafe918 Mon Sep 17 00:00:00 2001
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From: Gen Xu <xgbarry@gmail.com>
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Date: Wed, 5 May 2021 15:42:41 -0700
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Subject: [PATCH] bpo-44022: Fix http client infinite line reading (DoS) after
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a HTTP 100 Continue (GH-25916)
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Fixes http.client potential denial of service where it could get stuck reading lines from a malicious server after a 100 Continue response.
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Co-authored-by: Gregory P. Smith <greg@krypto.org>
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(cherry picked from commit 47895e31b6f626bc6ce47d175fe9d43c1098909d)
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Co-authored-by: Gen Xu <xgbarry@gmail.com>
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---
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Lib/http/client.py | 38 ++++++++++---------
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Lib/test/test_httplib.py | 10 ++++-
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.../2021-05-05-17-37-04.bpo-44022.bS3XJ9.rst | 2 +
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3 files changed, 32 insertions(+), 18 deletions(-)
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create mode 100644 Misc/NEWS.d/next/Security/2021-05-05-17-37-04.bpo-44022.bS3XJ9.rst
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diff --git a/Lib/http/client.py b/Lib/http/client.py
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index 53581eca20587..07e675fac5981 100644
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--- a/Lib/http/client.py
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+++ b/Lib/http/client.py
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@@ -205,15 +205,11 @@ def getallmatchingheaders(self, name):
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lst.append(line)
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return lst
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-def parse_headers(fp, _class=HTTPMessage):
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- """Parses only RFC2822 headers from a file pointer.
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-
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- email Parser wants to see strings rather than bytes.
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- But a TextIOWrapper around self.rfile would buffer too many bytes
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- from the stream, bytes which we later need to read as bytes.
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- So we read the correct bytes here, as bytes, for email Parser
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- to parse.
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+def _read_headers(fp):
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+ """Reads potential header lines into a list from a file pointer.
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+ Length of line is limited by _MAXLINE, and number of
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+ headers is limited by _MAXHEADERS.
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"""
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headers = []
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while True:
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@@ -225,6 +221,19 @@ def parse_headers(fp, _class=HTTPMessage):
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raise HTTPException("got more than %d headers" % _MAXHEADERS)
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if line in (b'\r\n', b'\n', b''):
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break
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+ return headers
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+
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+def parse_headers(fp, _class=HTTPMessage):
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+ """Parses only RFC2822 headers from a file pointer.
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+
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+ email Parser wants to see strings rather than bytes.
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+ But a TextIOWrapper around self.rfile would buffer too many bytes
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+ from the stream, bytes which we later need to read as bytes.
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+ So we read the correct bytes here, as bytes, for email Parser
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+ to parse.
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+
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+ """
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+ headers = _read_headers(fp)
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hstring = b''.join(headers).decode('iso-8859-1')
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return email.parser.Parser(_class=_class).parsestr(hstring)
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@@ -312,15 +321,10 @@ def begin(self):
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if status != CONTINUE:
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break
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# skip the header from the 100 response
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- while True:
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- skip = self.fp.readline(_MAXLINE + 1)
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- if len(skip) > _MAXLINE:
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- raise LineTooLong("header line")
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- skip = skip.strip()
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- if not skip:
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- break
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- if self.debuglevel > 0:
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- print("header:", skip)
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+ skipped_headers = _read_headers(self.fp)
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+ if self.debuglevel > 0:
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+ print("headers:", skipped_headers)
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+ del skipped_headers
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self.code = self.status = status
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self.reason = reason.strip()
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diff --git a/Lib/test/test_httplib.py b/Lib/test/test_httplib.py
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index 03e049b13fd21..0db287507c7bf 100644
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--- a/Lib/test/test_httplib.py
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+++ b/Lib/test/test_httplib.py
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@@ -971,6 +971,14 @@ def test_overflowing_header_line(self):
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resp = client.HTTPResponse(FakeSocket(body))
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self.assertRaises(client.LineTooLong, resp.begin)
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+ def test_overflowing_header_limit_after_100(self):
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+ body = (
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+ 'HTTP/1.1 100 OK\r\n'
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+ 'r\n' * 32768
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+ )
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+ resp = client.HTTPResponse(FakeSocket(body))
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+ self.assertRaises(client.HTTPException, resp.begin)
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+
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def test_overflowing_chunked_line(self):
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body = (
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'HTTP/1.1 200 OK\r\n'
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@@ -1377,7 +1385,7 @@ def readline(self, limit):
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class OfflineTest(TestCase):
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def test_all(self):
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# Documented objects defined in the module should be in __all__
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- expected = {"responses"} # White-list documented dict() object
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+ expected = {"responses"} # Allowlist documented dict() object
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# HTTPMessage, parse_headers(), and the HTTP status code constants are
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# intentionally omitted for simplicity
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blacklist = {"HTTPMessage", "parse_headers"}
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diff --git a/Misc/NEWS.d/next/Security/2021-05-05-17-37-04.bpo-44022.bS3XJ9.rst b/Misc/NEWS.d/next/Security/2021-05-05-17-37-04.bpo-44022.bS3XJ9.rst
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new file mode 100644
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index 0000000000000..cf6b63e396155
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--- /dev/null
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+++ b/Misc/NEWS.d/next/Security/2021-05-05-17-37-04.bpo-44022.bS3XJ9.rst
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@@ -0,0 +1,2 @@
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+mod:`http.client` now avoids infinitely reading potential HTTP headers after a
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+``100 Continue`` status response from the server.
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