[tor-bugs] #10148 [Obfsproxy]: Scramblesuit doesn't handle base32 decoded shared secrets properly

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#10148: Scramblesuit doesn't handle base32 decoded shared secrets properly
-----------------------------+----------------------
 Reporter:  isis             |          Owner:  isis
     Type:  defect           |         Status:  new
 Priority:  normal           |      Milestone:
Component:  Obfsproxy        |        Version:
 Keywords:  pt,scramblesuit  |  Actual Points:
Parent ID:                   |         Points:
-----------------------------+----------------------
 Using a uniform DH shared secret passphrase of
 `93edd2b39b06115b38778e5447be6171d34cf63cc0e083db91fca9ce7fe920fa`, I get
 the following unhandled exception in my scramblesuit logfile:

 {{{
 Traceback (most recent call last):
   File "/usr/local/lib/python2.7/dist-packages/obfsproxy-0.2
 .3_14_g4acf4da-py2.7.egg/obfsproxy/pyobfsproxy.py", line 158, in run
     pyobfsproxy()
   File "/usr/local/lib/python2.7/dist-packages/obfsproxy-0.2
 .3_14_g4acf4da-py2.7.egg/obfsproxy/pyobfsproxy.py", line 137, in
 pyobfsproxy
     if (args.validation_function(args) == False):
   File "/usr/local/lib/python2.7/dist-packages/obfsproxy-0.2
 .3_14_g4acf4da-
 py2.7.egg/obfsproxy/transports/scramblesuit/scramblesuit.py", line 534, in
 validate_external_mode_cli
     rawLength = len(base64.b32decode(args.uniformDHSecret))
   File "/usr/lib/python2.7/base64.py", line 196, in b32decode
     quanta, leftover = divmod(len(s), 8)
 TypeError: object of type 'NoneType' has no len()
 }}}

 Scramblesuit should probably at least catch the case where
 `base64.b32decode` returns None, and the case where it raises `TypeError`s
 due to "invalid padding".

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/10148>
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