------------------------------------------------------------
revno: 310
committer: Scott Moser <smoser@ubuntu.com>
branch nick: trunk
timestamp: Mon 2010-09-20 09:42:56 -0400
message:
  fix transient 'Odd-length string' error in euca-bundle-image
  
  The problem was that the euca2ools/__init__.py was doing:
     iv = (hex(BN.rand(16 * 8,top=0)))[2:34].replace('L','c')
  then
     unhexlify(iv)
  
  But BN.rand(16*8) is not guaranteed to return a number that is
  represented by 32 hex digits. I suspect that the .replace('L','c') was
  added to get around this issue. By specifying 'top=0' in the BN.rand
  call, we guarantee that the number will have the top bit set.
  
  I've ran the following snippet past i=40,000,000 . Without the fix in
  place I never saw it run past 1000.
  
  while True:
     i=i+1
     try:
        uh = unhexlify((hex(BN.rand(17 * 8,top=0)))[4:36])
     except KeyboardInterrupt:
        print "tried %i times, no failures yet" % i
     except:
        print "found failure, i=%s, iv=%s len=(%s)" % (i,iv,len(iv))
        sys.exit(1)
diff:
=== modified file 'euca2ools/euca2ools/__init__.py'
--- euca2ools/euca2ools/__init__.py	2010-09-03 16:18:03 +0000
+++ euca2ools/euca2ools/__init__.py	2010-09-20 13:42:56 +0000
@@ -711,10 +711,13 @@
         print 'Encrypting image'
         enc_file = '%s.part' % file.replace('.tar.gz', '')
 
-        key = hex(BN.rand(16 * 8))[2:34].replace('L', 'c')
+        # get 17 bytes of randomness with top bit a '1'.
+        # convert to a hex string like '0x<34 hex chars>L'
+        # then take the last 32 of the hex digits, giving 32 random hex chars
+        key = hex(BN.rand(17 * 8,top=0))[4:36]
         if self.debug:
             print 'Key: %s' % key
-        iv = hex(BN.rand(16 * 8))[2:34].replace('L', 'c')
+        iv = hex(BN.rand(17 * 8,top=0))[4:36]
         if self.debug:
             print 'IV: %s' % iv