[PATCH 5 of 5] bundle2: detect and disallow a negative chunk size

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at fb.com>
# Date 1413368845 25200
#      Wed Oct 15 03:27:25 2014 -0700
# Node ID f52ea5af3c55e6846d9988a3b7741d6f5b6b975b
# Parent  91c0c243dae1d965bfb159c86445875188b9068a
bundle2: detect and disallow a negative chunk size

We have no usage planned for 2/3 of them and the support for the planned
usecase is not here yet. So we raise a BundleValueError when encountered

diff --git a/mercurial/bundle2.py b/mercurial/bundle2.py
--- a/mercurial/bundle2.py
+++ b/mercurial/bundle2.py
@@ -507,10 +507,13 @@ class unbundle20(unpackermixin):
     def params(self):
         """dictionary of stream level parameters"""
         self.ui.debug('reading bundle2 stream parameters\n')
         params = {}
         paramssize = self._unpack(_fstreamparamsize)[0]
+        if paramssize < 0:
+            raise error.BundleValueError('negative bundle param size: %i'
+                                         % paramssize)
         if paramssize:
             for p in self._readexact(paramssize).split(' '):
                 p = p.split('=', 1)
                 p = [urllib.unquote(i) for i in p]
                 if len(p) < 2:
@@ -556,10 +559,13 @@ class unbundle20(unpackermixin):
     def _readpartheader(self):
         """reads a part header size and return the bytes blob
 
         returns None if empty"""
         headersize = self._unpack(_fpartheadersize)[0]
+        if headersize < 0:
+            raise error.BundleValueError('negative part header size: %i'
+                                         % headersize)
         self.ui.debug('part header size: %i\n' % headersize)
         if headersize:
             return self._readexact(headersize)
         return None
 
@@ -763,10 +769,13 @@ class unbundlepart(unpackermixin):
         ## part payload
         def payloadchunks():
             payloadsize = self._unpack(_fpayloadsize)[0]
             self.ui.debug('payload chunk size: %i\n' % payloadsize)
             while payloadsize:
+                if payloadsize < 0:
+                    msg = 'negative payload chunk size: %i' % payloadsize
+                    raise error.BundleValueError(msg)
                 yield self._readexact(payloadsize)
                 payloadsize = self._unpack(_fpayloadsize)[0]
                 self.ui.debug('payload chunk size: %i\n' % payloadsize)
         self._payloadstream = util.chunkbuffer(payloadchunks())
         # we read the data, tell it