SHA256 difference between Windows+Ubuntu

[Murray]

Hi,

I'm quite new to both C++ and crypto++, and have been trying to work out this problem.

I've successfully installed crypto++ 5.6.2 to Windows 7 64-bit and Ubuntu 12.04 64-bit.

Under Ubuntu, my SHA256() function occasionally returns nothing. I can reproduce it usually by entering a few large values and then a couple small. It works 100% of the time under windows.

g++ version 4.6.3.

Any hints would be appreciated,

Thanks.

1. I compile with:
   g++ -m32 -O3 -fpic -g -c main.cpp -lcryptopp
2. g++ -m32 -shared -o test.exe main.o -lc --static -lcryptopp
   
   
   
   
   
   1. #include "cryptopp/sha.h"
   2. #include "cryptopp/base64.h"
   3. #include "cryptopp/hex.h"
   4. #include <iostream>
   5. #include <string>
   6.  
   7. const char * SHA256(const char * argv)
   8. {
   9.     CryptoPP::SHA256 hash;
   10.     byte digest[ CryptoPP::SHA256::DIGESTSIZE ];
   11.     std::string input = std::string(argv);
   12.  
   13.     hash.CalculateDigest( digest, (const byte *)input.c_str(), input.length() );
   14.  
   15.     CryptoPP::HexEncoder encoder;
   16.     std::string output;
   17.     encoder.Attach(new CryptoPP::StringSink( output ));
   18.     encoder.Put( digest, sizeof(digest) );
   19.     encoder.MessageEnd();
   20.     return output.c_str();
   21. }
   22. int main()
   23. {
   24.         std::string str;
   25.         while(1)
   26.         {
   27.                 str.clear();
   28.                 std::getline(std::cin, str);
   29.                 const char * result = SHA256(str.c_str());
   30.                 std::cout << "Hash: " << result << std::endl;
   31.         }
   32.         return 0;
   33. }

[Christopher Head]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

See below.

Chris

On Thu, 9 May 2013 20:13:34 -0700 (PDT)
Murray <in...@murrawhip.net> wrote:

> 7. const char * SHA256(const char * argv)
> 8. {
> 9. CryptoPP::SHA256 hash;
> 10. byte digest[ CryptoPP::SHA256::DIGESTSIZE ];
> 11. std::string input = std::string(argv);
> 12.
> 13. hash.CalculateDigest( digest, (const byte
> *)input.c_str(), input.length() );
> 14.
> 15. CryptoPP::HexEncoder encoder;
> 16. std::string output;
> 17. encoder.Attach(new CryptoPP::StringSink( output ));
> 18. encoder.Put( digest, sizeof(digest) );
> 19. encoder.MessageEnd();
> 20. return output.c_str();

On this line, you are returning a pointer to a member of a local
variable. The variable output is a local and will therefore be
destroyed on return, which also deallocates the internal storage used
to hold the c_str. You then use the c_str after it has been freed. You
should return an std::string instead.

> 21. }
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