CVE-2013-1752: poplib: Limit maximum line lengths to 2048

Issue #16041: CVE-2013-1752: poplib: Limit maximum line lengths to 2048 to
prevent readline() calls from consuming too much memory.  Patch by Jyrki
Pulliainen.

Change-Id: I3a9b6c76afba85f7c18de5a368df2dc96b534b55
Signed-off-by: Chanho Park <chanho61.park@samsung.com>

2 files changed, 15 insertions, 2 deletions

diff --git a/Lib/poplib.py b/Lib/poplib.py
index dc7cbdf..d03330f 100644
--- a/Lib/poplib.py
+++ b/Lib/poplib.py
@@ -32,6 +32,12 @@ CR = '\r'
 LF = '\n'
 CRLF = CR+LF
 
+# maximal line length when calling readline(). This is to prevent
+# reading arbitrary lenght lines. RFC 1939 limits POP3 line length to
+# 512 characters, including CRLF. We have selected 2048 just to be on
+# the safe side.
+_MAXLINE = 2048
+
 
 class POP3:
 
@@ -103,7 +109,10 @@ class POP3:
     # Raise error_proto('-ERR EOF') if the connection is closed.
 
     def _getline(self):
-        line = self.file.readline()
+        line = self.file.readline(_MAXLINE + 1)
+        if len(line) > _MAXLINE:
+            raise error_proto('line too long')
+
         if self._debugging > 1: print '*get*', repr(line)
         if not line: raise error_proto('-ERR EOF')
         octets = len(line)
diff --git a/Lib/test/test_poplib.py b/Lib/test/test_poplib.py
index af48fdd..7a7d7d9 100644
--- a/Lib/test/test_poplib.py
+++ b/Lib/test/test_poplib.py
@@ -81,7 +81,7 @@ class DummyPOP3Handler(asynchat.async_chat):
 
     def cmd_list(self, arg):
         if arg:
-            self.push('+OK %s %s' %(arg, arg))
+            self.push('+OK %s %s' % (arg, arg))
         else:
             self.push('+OK')
             asynchat.async_chat.push(self, LIST_RESP)
@@ -198,6 +198,10 @@ class TestPOP3Class(TestCase):
                     113)
         self.assertEqual(self.client.retr('foo'), expected)
 
+    def test_too_long_lines(self):
+        self.assertRaises(poplib.error_proto, self.client._shortcmd,
+                          'echo +%s' % ((poplib._MAXLINE + 10) * 'a'))
+
     def test_dele(self):
         self.assertOK(self.client.dele('foo'))