[Python-checkins] bpo-39055: Reject a trailing \n in base64.b64decode() with validate=True. (GH-17616)

[Miss Islington (bot)]

https://github.com/python/cpython/commit/3bdb2d9daf3ce41b325bd508e3dd29041e85dd1f
commit: 3bdb2d9daf3ce41b325bd508e3dd29041e85dd1f
branch: 3.7
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2020-01-05T04:32:45-08:00
summary:

bpo-39055: Reject a trailing \n in base64.b64decode() with validate=True. (GH-17616)

(cherry picked from commit b19c0d77e6f25ea831ab608c71f15d0d9266c8c4)

Co-authored-by: Serhiy Storchaka <storchaka at gmail.com>

files:
A Misc/NEWS.d/next/Library/2019-12-15-19-23-23.bpo-39055.FmN3un.rst
M Lib/base64.py
M Lib/test/test_base64.py

diff --git a/Lib/base64.py b/Lib/base64.py
index 2be9c395a9667..2e70223dfe782 100755
--- a/Lib/base64.py
+++ b/Lib/base64.py
@@ -82,7 +82,7 @@ def b64decode(s, altchars=None, validate=False):
         altchars = _bytes_from_decode_data(altchars)
         assert len(altchars) == 2, repr(altchars)
         s = s.translate(bytes.maketrans(altchars, b'+/'))
-    if validate and not re.match(b'^[A-Za-z0-9+/]*={0,2}$', s):
+    if validate and not re.fullmatch(b'[A-Za-z0-9+/]*={0,2}', s):
         raise binascii.Error('Non-base64 digit found')
     return binascii.a2b_base64(s)
 
diff --git a/Lib/test/test_base64.py b/Lib/test/test_base64.py
index 2a4cc2acad24b..7dba6635d4eae 100644
--- a/Lib/test/test_base64.py
+++ b/Lib/test/test_base64.py
@@ -250,6 +250,7 @@ def test_b64decode_invalid_chars(self):
                  (b'3d}==', b'\xdd'),
                  (b'@@', b''),
                  (b'!', b''),
+                 (b"YWJj\n", b"abc"),
                  (b'YWJj\nYWI=', b'abcab'))
         funcs = (
             base64.b64decode,
diff --git a/Misc/NEWS.d/next/Library/2019-12-15-19-23-23.bpo-39055.FmN3un.rst b/Misc/NEWS.d/next/Library/2019-12-15-19-23-23.bpo-39055.FmN3un.rst
new file mode 100644
index 0000000000000..83b1431e92fcb
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-12-15-19-23-23.bpo-39055.FmN3un.rst
@@ -0,0 +1,2 @@
+:func:`base64.b64decode` with ``validate=True`` raises now a binascii.Error
+if the input ends with a single ``\n``.