[Python-checkins] bpo-38945: UU Encoding: Don't let newline in filename corrupt the output format (#17418)

[Guido van Rossum]

https://github.com/python/cpython/commit/a62ad4730c9b575f140f24074656c0257c86a09a
commit: a62ad4730c9b575f140f24074656c0257c86a09a
branch: master
author: Matthew Rollings <1211162+stealthcopter at users.noreply.github.com>
committer: Guido van Rossum <guido at python.org>
date: 2019-12-02T14:25:21-08:00
summary:

bpo-38945: UU Encoding: Don't let newline in filename corrupt the output format (#17418)

files:
A Misc/NEWS.d/next/Security/2019-12-01-22-44-40.bpo-38945.ztmNXc.rst
M Lib/encodings/uu_codec.py
M Lib/test/test_uu.py
M Lib/uu.py

diff --git a/Lib/encodings/uu_codec.py b/Lib/encodings/uu_codec.py
index 2a5728fb5b74a..4e58c62fe9ef0 100644
--- a/Lib/encodings/uu_codec.py
+++ b/Lib/encodings/uu_codec.py
@@ -20,6 +20,10 @@ def uu_encode(input, errors='strict', filename='<data>', mode=0o666):
     read = infile.read
     write = outfile.write
 
+    # Remove newline chars from filename
+    filename = filename.replace('\n','\\n')
+    filename = filename.replace('\r','\\r')
+
     # Encode
     write(('begin %o %s\n' % (mode & 0o777, filename)).encode('ascii'))
     chunk = read(45)
diff --git a/Lib/test/test_uu.py b/Lib/test/test_uu.py
index c9f05e5b760d9..c8709f7a0d666 100644
--- a/Lib/test/test_uu.py
+++ b/Lib/test/test_uu.py
@@ -136,6 +136,15 @@ def test_garbage_padding(self):
                 decoded = codecs.decode(encodedtext, "uu_codec")
                 self.assertEqual(decoded, plaintext)
 
+    def test_newlines_escaped(self):
+        # Test newlines are escaped with uu.encode
+        inp = io.BytesIO(plaintext)
+        out = io.BytesIO()
+        filename = "test.txt\n\roverflow.txt"
+        safefilename = b"test.txt\\n\\roverflow.txt"
+        uu.encode(inp, out, filename)
+        self.assertIn(safefilename, out.getvalue())
+
 class UUStdIOTest(unittest.TestCase):
 
     def setUp(self):
diff --git a/Lib/uu.py b/Lib/uu.py
index 9b1e5e607207f..9f1f37f1a6410 100755
--- a/Lib/uu.py
+++ b/Lib/uu.py
@@ -73,6 +73,13 @@ def encode(in_file, out_file, name=None, mode=None, *, backtick=False):
             name = '-'
         if mode is None:
             mode = 0o666
+
+        #
+        # Remove newline chars from name
+        #
+        name = name.replace('\n','\\n')
+        name = name.replace('\r','\\r')
+
         #
         # Write the data
         #
diff --git a/Misc/NEWS.d/next/Security/2019-12-01-22-44-40.bpo-38945.ztmNXc.rst b/Misc/NEWS.d/next/Security/2019-12-01-22-44-40.bpo-38945.ztmNXc.rst
new file mode 100644
index 0000000000000..1bf6ed567b241
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2019-12-01-22-44-40.bpo-38945.ztmNXc.rst
@@ -0,0 +1 @@
+Newline characters have been escaped when performing uu encoding to prevent them from overflowing into to content section of the encoded file. This prevents malicious or accidental modification of data during the decoding process.
\ No newline at end of file