[project @ robey@lag.net-20061215211936-rgc3uzy5ai9h6qho]

bug 75370: notice garbage sftp packets
since sftp packets shouldn't be larger than about 32k, if the first length
byte is non-zero (ie, the packet size > 16M), raise an exception.

1 files changed, 6 insertions, 1 deletions

diff --git a/paramiko/sftp.py b/paramiko/sftp.py
index 0b2bbe29..8047c4a2 100644
--- a/paramiko/sftp.py
+++ b/paramiko/sftp.py
@@ -176,7 +176,12 @@ class BaseSFTP (object):
         self._write_all(out)
 
     def _read_packet(self):
-        size = struct.unpack('>I', self._read_all(4))[0]
+        x = self._read_all(4)
+        # most sftp servers won't accept packets larger than about 32k, so
+        # anything with the high byte set (> 16MB) is just garbage.
+        if x[0] != '\x00':
+            raise SFTPError('Garbage packet received')
+        size = struct.unpack('>I', x)[0]
         data = self._read_all(size)
         if self.ultra_debug:
             self._log(DEBUG, util.format_binary(data, 'IN: '));