[Xen-devel] [PATCH] xend: Fix hex decoding in sxp.Parser

[Philipp Hahn <hahn@xxxxxxxxxxxxx>]

"xm list" sometimes failes with the following traceback:
> Traceback (most recent call last):
>   File "/root/36098_xend-expat.py", line 84, in <module>
>     main_xmlrpc()
>   File "/root/36098_xend-expat.py", line 50, in main_xmlrpc
>     result = xend.xend.domain(UUID)
>   File "/usr/lib/python2.6/xmlrpclib.py", line 1199, in __call__
>     return self.__send(self.__name, args)
>   File "/usr/lib/python2.6/xmlrpclib.py", line 1489, in __request
>     verbose=self.__verbose
>   File "/usr/lib/python2.6/xmlrpclib.py", line 1253, in request
>     return self._parse_response(h.getfile(), sock)
>   File "/usr/lib/python2.6/xmlrpclib.py", line 1387, in _parse_response
>     p.feed(response)
>   File "/usr/lib/python2.6/xmlrpclib.py", line 601, in feed
>     self._parser.Parse(data, 0)
> xml.parsers.expat.ExpatError: not well-formed (invalid token): line 45, 
> column 18

This happens when the descriptive text for a VM contains
non-ASCII-characters, which xen.xend.sxp.show() converts to Python
hex-escapes:
> print repr(unichr(8364).encode('UTF-8'))
> '\xe2\x82\xac'

On read-back those are processed by xen.xend.sxp.Parser.state_hex(),
which is broken: 'a'..'f' respective 'A'..'F' are converted to 0..5
instead of 10..15. Thus the above sequence gets read back as:
'B\x82\x02'. When converted to XML this produces invalid XML, which
breaks expat.

Use Pythont int(..., 16) instead.

Signed-off-by: Philipp Hahn <hahn@xxxxxxxxxxxxx>
---
 tools/python/xen/xend/sxp.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/python/xen/xend/sxp.py b/tools/python/xen/xend/sxp.py
index c87270f..d585218 100644
--- a/tools/python/xen/xend/sxp.py
+++ b/tools/python/xen/xend/sxp.py
@@ -305,9 +305,9 @@ class Parser:
             self.state.parent.buf += d
             self.pop_state()
             
-        def hexdigit(c, d):
+        def hexdigit(c):
             self.state.val *= 16
-            self.state.val += ord(c) - ord(d)
+            self.state.val += int(c, 16)
             self.state.buf += c
             if self.state.val < 0 or self.state.val > 0xff:
                 raise ParseError(self, "invalid hex escape: out of range " + 
self.state.buf)
@@ -317,11 +317,11 @@ class Parser:
         if self.at_eof():
             raise ParseError(self, "unexpected EOF")
         elif '0' <= c <= '9':
-            hexdigit(c, '0')
+            hexdigit(c)
         elif 'A' <= c <= 'F':
-            hexdigit(c, 'A')
+            hexdigit(c)
         elif 'a' <= c <= 'f':
-            hexdigit(c, 'a')
+            hexdigit(c)
         elif len(buf):
             hexdone()
             self.input_char(c)
-- 
1.9.1


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