crypto incompatibilities between pycrypto and bouncycastle

[Antoine Martin]

There are at least two things that need addressing:

• verify_key(...) sometimes fails and therefore the identity of the server is rejected, not sure why this is intermittent
• When decrypting encrypted messages:

  org.bouncycastle.crypto.DataLengthException: input too large for RSA cipher.
  

I am still a bit puzzled as to why pycrypto manages to decrypt such blocks and BouncyCastle does not. Either we fix the data length using a specific padding scheme (as the length of the input looks fine as it is: <100bytes with 4096bit keys is ok), or we use a symmetric cipher for all encrypted packets (and exchange it during the login phase).

More info on this issue: ​Too much data for RSA block fail

See also #158

[Antoine Martin]

verify_key is fixed in r4820: fix byte array size properly (not making assumptions)