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RSA and DSA C++ generated keysets are incompatibles with Java implementation #56

Closed GoogleCodeExporter closed 9 years ago

GoogleCodeExporter commented 9 years ago 
Thanks to Cory Bennett for having reported this issue in the first place.

What steps will reproduce the problem?
1. When RSA or DSA keysets are generated from the C++ implementation they can't 
not be correctly loaded from the Java implementation.

Original issue reported on code.google.com by sebastien.martini on 19 Jun 2010 at 12:18

GoogleCodeExporter commented 9 years ago 
It turns out that the Python and Java implementations generates keys with an 
additional msb set to 0, that is keys are padded on the left with \x00.

While the Python implementation tolerates keys without this additional byte, 
Java implementation raises javax.crypto.BadPaddingException: Message is larger 
than modulus

Below is attached a script which should help converting previously generated 
C++ keysets to Java "compatible" keysets. Only RSA and DSA keysets need to be 
converted.

Additionally the C++ implementation needs to be fixed to generate keys with the 
same format than others implementations. Note that this modification will still 
work with previously generated C++ keysets, but they won't be converted 
automatically.

Original comment by sebastien.martini on 19 Jun 2010 at 12:38

Attachments:

GoogleCodeExporter commented 9 years ago

Original comment by sebastien.martini on 19 Jun 2010 at 4:53

GoogleCodeExporter commented 9 years ago 
I ran the convert_keyset.py, and it fixes some issues.  I can now use the 
keyset to encrypt in java, however I cannot use it to decrypt in java.  I 
verified I can  encrypt in java and use that output to decrypt in c++ and 
python, but when attempting to decrypt in java I get:

Exception in thread "main" java.lang.ArithmeticException: BigInteger: modulus 
not positive
        at java.math.BigInteger.modPow(BigInteger.java:1548)
        at sun.security.rsa.RSACore.crtCrypt(RSACore.java:137)
        at sun.security.rsa.RSACore.rsa(RSACore.java:84)
        at com.sun.crypto.provider.RSACipher.a(DashoA13*..)
        at com.sun.crypto.provider.RSACipher.engineDoFinal(DashoA13*..)
        at javax.crypto.CipherSpi.a(DashoA13*..)
        at javax.crypto.CipherSpi.engineDoFinal(DashoA13*..)
        at javax.crypto.Cipher.doFinal(DashoA13*..)
        at org.keyczar.RsaPrivateKey$RsaPrivateStream.doFinalDecrypt(RsaPrivateKey.java:183)
        at org.keyczar.Crypter.decrypt(Crypter.java:168)
        at org.keyczar.Crypter.decrypt(Crypter.java:84)
        at org.keyczar.Crypter.decrypt(Crypter.java:184)

Thanks
-Cory

Original comment by g.co...@gmail.com on 19 Jun 2010 at 5:19

GoogleCodeExporter commented 9 years ago 
Ooops try this version instead this should be better.

Original comment by sebastien.martini on 19 Jun 2010 at 6:43

Attachments:

GoogleCodeExporter commented 9 years ago 
The last convert_keyset.py works great.  All my test cases passed with new 
converted keysets.  Thanks Sebastien!

-Cory

Original comment by g.co...@gmail.com on 20 Jun 2010 at 5:35

GoogleCodeExporter commented 9 years ago 
Great, I've just committed these changes of format to the C++ implementation 
itself, see http://code.google.com/p/keyczar/source/detail?r=466

Original comment by sebastien.martini on 20 Jun 2010 at 7:29

GoogleCodeExporter commented 9 years ago 
Of course, report if you observe any remaining problem or regression 
encountered with these changes.

Otherwise I'll close this issue.

Original comment by sebastien.martini on 20 Jun 2010 at 7:54

GoogleCodeExporter commented 9 years ago 
This issue was the result of different binary representations of big integers 
in Java and OpenSSL. Java uses one additional byte to represent value's sign (0 
when positive), OpenSSL serializes absolute values thus doesn't need this byte. 
Therefore C++ and Python implementation just prepend a null byte to their 
binary keys.

Next is a quick summary about how developers could be affected by this issue 
and what steps they should take to resolve it:

- C++ users have to convert [1] their RSA/DSA keysets generated from old 
versions (<r466) of Keyczar C++ if they plan to use these keysets from the Java 
implementation of Keyczar.
- C++ users should upgrade their version of Keyczar C++ (with a version whose 
revision is >=466) in order to generate new keys with a format compatible with 
C++/Java/Python versions of Keyczar. Moreover old keysets even if not 
explicitly converted will still be working with this new C++ implementation.
- Old C++ keysets work with Python implementation.

[1] 
http://code.google.com/p/keyczar/source/browse/trunk/cpp/src/keyczar/keyczar_too
l/convert_keyset.py

Original comment by sebastien.martini on 21 Jun 2010 at 11:45

GoogleCodeExporter commented 9 years ago

Original comment by sebastien.martini on 24 Jun 2010 at 11:59