Issue python#16038: CVE-2013-1752: ftplib: Limit amount of data read by

birkenfeld · birkenfeld · commit c9cb18d3f7e5 · 2014-09-30T14:12:24.000+02:00
limiting the call to readline().  Original patch by Michał
Jastrzębski and Giampaolo Rodola.
diff --git a/Lib/ftplib.py b/Lib/ftplib.py
@@ -49,6 +49,8 @@
 
 # The standard FTP server control port
 FTP_PORT = 21
+# The sizehint parameter passed to readline() calls
+MAXLINE = 8192
 
 
 # Exception raised when an error or invalid response is received
@@ -96,6 +98,7 @@ class FTP:
     debugging = 0
     host = ''
     port = FTP_PORT
+    maxline = MAXLINE
     sock = None
     file = None
     welcome = None
@@ -190,7 +193,9 @@ def putcmd(self, line):
     # Internal: return one line from the server, stripping CRLF.
     # Raise EOFError if the connection is closed
     def getline(self):
-        line = self.file.readline()
+        line = self.file.readline(self.maxline + 1)
+        if len(line) > self.maxline:
+            raise Error("got more than %d bytes" % self.maxline)
         if self.debugging > 1:
             print('*get*', self.sanitize(line))
         if not line: raise EOFError
@@ -444,7 +449,9 @@ def retrlines(self, cmd, callback = None):
         with self.transfercmd(cmd) as conn, \
                  conn.makefile('r', encoding=self.encoding) as fp:
             while 1:
-                line = fp.readline()
+                line = fp.readline(self.maxline + 1)
+                if len(line) > self.maxline:
+                    raise Error("got more than %d bytes" % self.maxline)
                 if self.debugging > 2: print('*retr*', repr(line))
                 if not line:
                     break
@@ -494,7 +501,9 @@ def storlines(self, cmd, fp, callback=None):
         self.voidcmd('TYPE A')
         with self.transfercmd(cmd) as conn:
             while 1:
-                buf = fp.readline()
+                buf = fp.readline(self.maxline + 1)
+                if len(buf) > self.maxline:
+                    raise Error("got more than %d bytes" % self.maxline)
                 if not buf: break
                 if buf[-2:] != B_CRLF:
                     if buf[-1] in B_CRLF: buf = buf[:-1]
@@ -741,7 +750,9 @@ def retrlines(self, cmd, callback = None):
             fp = conn.makefile('r', encoding=self.encoding)
             try:
                 while 1:
-                    line = fp.readline()
+                    line = fp.readline(self.maxline + 1)
+                    if len(line) > self.maxline:
+                        raise Error("got more than %d bytes" % self.maxline)
                     if self.debugging > 2: print('*retr*', repr(line))
                     if not line:
                         break
@@ -779,7 +790,9 @@ def storlines(self, cmd, fp, callback=None):
             conn = self.transfercmd(cmd)
             try:
                 while 1:
-                    buf = fp.readline()
+                    buf = fp.readline(self.maxline + 1)
+                    if len(buf) > self.maxline:
+                        raise Error("got more than %d bytes" % self.maxline)
                     if not buf: break
                     if buf[-2:] != B_CRLF:
                         if buf[-1] in B_CRLF: buf = buf[:-1]
diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
@@ -70,6 +70,7 @@ def __init__(self, conn):
         self.last_received_data = ''
         self.next_response = ''
         self.rest = None
+        self.next_retr_data = RETR_DATA
         self.push('220 welcome')
 
     def collect_incoming_data(self, data):
@@ -199,7 +200,7 @@ def cmd_retr(self, arg):
             offset = int(self.rest)
         else:
             offset = 0
-        self.dtp.push(RETR_DATA[offset:])
+        self.dtp.push(self.next_retr_data[offset:])
         self.dtp.close_when_done()
         self.rest = None
 
@@ -213,6 +214,11 @@ def cmd_nlst(self, arg):
         self.dtp.push(NLST_DATA)
         self.dtp.close_when_done()
 
+    def cmd_setlongretr(self, arg):
+        # For testing. Next RETR will return long line.
+        self.next_retr_data = 'x' * int(arg)
+        self.push('125 setlongretr ok')
+
 
 class DummyFTPServer(asyncore.dispatcher, threading.Thread):
 
@@ -628,6 +634,20 @@ def test_parse257(self):
         self.assertEqual(ftplib.parse257('257 "/foo/b""ar"'), '/foo/b"ar')
         self.assertEqual(ftplib.parse257('257 "/foo/b""ar" created'), '/foo/b"ar')
 
+    def test_line_too_long(self):
+        self.assertRaises(ftplib.Error, self.client.sendcmd,
+                          'x' * self.client.maxline * 2)
+
+    def test_retrlines_too_long(self):
+        self.client.sendcmd('SETLONGRETR %d' % (self.client.maxline * 2))
+        received = []
+        self.assertRaises(ftplib.Error,
+                          self.client.retrlines, 'retr', received.append)
+
+    def test_storlines_too_long(self):
+        f = io.BytesIO(b'x' * self.client.maxline * 2)
+        self.assertRaises(ftplib.Error, self.client.storlines, 'stor', f)
+
 
 class TestIPv6Environment(TestCase):
 
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -10,6 +10,10 @@ What's New in Python 3.2.6?
 Library
 -------
 
+- Issue #16038: CVE-2013-1752: ftplib: Limit amount of data read by
+  limiting the call to readline().  Original patch by Michał
+  Jastrzębski and Giampaolo Rodola.
+
 - Issue #16037: HTTPMessage.readheaders() raises an HTTPException when more than
   100 headers are read.  Adapted from patch by Jyrki Pulliainen.
 
