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bpo-29606: urllib throwing an exception on any URLs that contain one of '\r\n' for the FTP protocol. #1216

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bpo-29606: urllib throwing an exception on any URLs that contain one of '\r\n' for the FTP protocol. #1216

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16 changes: 16 additions & 0 deletions Lib/test/test_urllib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -426,6 +426,22 @@ def test_ftp_nonexisting(self):
self.assertFalse(e.exception.filename)
self.assertTrue(e.exception.reason)

def test_ftp_illegalhost(self):
illegal_ftp_hosts = [
'ftp://foo:bar%0d%[email protected]/file.png',
'fTp://foo:bar%0d%[email protected]/file.png',
'FTP://foo:bar%0d%[email protected]/file.png',
'ftp://foo:bar%[email protected]/file.png',
'fTp://foo:bar%[email protected]/file.png',
'FTP://foo:bar%[email protected]/file.png'
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I don't think that it's interesting to test different cases, I suggest to only test %0d%0a and %0a, so only keep two tests using ftp:// prefix.

]

for host in illegal_ftp_hosts:
with self.assertRaises(urllib.error.URLError) as e:
urlopen(host)
self.assertFalse(e.exception.filename)
self.assertTrue(e.exception.reason)
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The test is invalid: it must check that the error contains "illegal host". In my case, the test only succeded because of another URLError.

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For example, the test pass if the connection fails with <urlopen error ftp error ConnectionRefusedError(111, 'Connection refused')>

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As I mentioned above, the tests should also include injection attempts on directories and filenames. After all, these portions of a URL illicit different FTP commands at different times.


@patch.object(urllib.request, 'MAXFTPCACHE', 0)
def test_ftp_cache_pruning(self):
self.fakeftp()
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3 changes: 3 additions & 0 deletions Lib/urllib/request.py
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Expand Up @@ -1502,6 +1502,9 @@ def ftp_open(self, req):
host = req.host
if not host:
raise URLError('ftp error: no host given')
target_host = unquote(host)
if '\n' in target_host:
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Should we also blacklist \r?

raise URLError("illegal ftp host")
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I suggest to keep the "ftp error" prefix for the error message, so:

ftp error: illegal host

host, port = splitport(host)
if port is None:
port = ftplib.FTP_PORT
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3 changes: 3 additions & 0 deletions Misc/NEWS
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Expand Up @@ -365,6 +365,9 @@ Extension Modules
Library
-------

- bpo-29606: urllib throwing an URL exception on any URLs that
contain one of '\n' for the FTP protocol. Patch by Dong-hee Na

- [Security] bpo-29591: Update expat copy from 2.1.1 to 2.2.0 to get fixes
of CVE-2016-0718 and CVE-2016-4472. See
https://sourceforge.net/p/expat/bugs/537/ for more information.
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