Strange Bug

Chris M. via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Fri Jan 20 00:19:57 PST 2017


I have no idea if this is an issue with D, or OpenSSL, or if I'm 
just doing something completely wrong. I'm writing a program that 
will either encrypt or decrypt a string using AES in ECB mode 
(for a school assignment) and it's giving me a very strange bug.

encrypt and decrypt are both bools, either one or the other is 
set based on command-line arguments passed to the program. aesKey 
is a 128-bit value hashed from user input, and is (obviously) 
used as the key for encryption. inputStr is either the string to 
be encrypted or decrypted (also passed in as a command-line 
argument). I grabbed the OpenSSL bindings from Deimos to do this.

if(encrypt)
{
     AES_KEY encKey;
     auto encOut = new ubyte[inputStr.length];

     // Encrypt and convert to base64
     AES_set_encrypt_key(aesKey.ptr, aesKey.sizeof * 8, &encKey);
     AES_ecb_encrypt(inputStr.ptr, encOut.ptr, &encKey, 
AES_ENCRYPT);
     writeln(Base64.encode(encOut));
}
else if(decrypt) // I'd leave this as else, but it's here for 
explanation purposes
{
     AES_KEY decKey;
     auto decLength = Base64.decodeLength(inputStr.length);
     auto decB64 = new ubyte[decLength], decOut = new 
ubyte[decLength];

     // convert back from base64 and decrypt
     decB64 = Base64.decode(inputStr); // Yes I checked, and 
decB64 has exact the same contents as encOut from the if block
     AES_set_decrypt_key(aesKey.ptr, aesKey.sizeof * 8, &decKey);
     AES_ecb_encrypt(decB64.ptr, decOut.ptr, &decKey, AES_DECRYPT);
     writeln(cast(char[]) decOut);
}

However, this isn't working for a very strange reason (spits back 
garbage instead of the string I originally encrypted).

Here's the problem. I tried running this without the if-else 
statements (i.e. encrypting and decrypting all in one run of the 
program, code below). If I leave in the base64 encoding and 
decoding, and use decB64 as the input to decrypt, it still 
doesn't work. However, if I decrypt with encOut directly, or 
assign encOut to decB64, it somehow works.

AES_KEY encKey;
auto encOut = new ubyte[inputStr.length];

// Encrypt and convert to base64
AES_set_encrypt_key(aesKey.ptr, aesKey.sizeof * 8, &encKey);
AES_ecb_encrypt(inputStr.ptr, encOut.ptr, &encKey, AES_ENCRYPT);

auto decLength = 
Base64.decodeLength(Base64.encode(encOut).length);
AES_KEY decKey;
auto decB64 = new ubyte[decLength], decOut = new ubyte[decLength];

// convert back from base64 and decrypt
decB64 = Base64.decode(Base64.encode(encOut));
// doesn't work unless I uncomment out the following line, or 
just use encOut directly
//decB64 = encOut;
AES_set_decrypt_key(aesKey.ptr, aesKey.sizeof * 8, &decKey);
AES_ecb_encrypt(decB64.ptr, decOut.ptr, &decKey, AES_DECRYPT);
writeln(cast(char[]) decOut);

tl;dr The decryption doesn't work unless I pass it the exact same 
buffer (including not only contents, but apparently the exact 
same memory address) that I used to receive output from encryption

Does anyone have any idea where the issue may lie, or how I could 
fix this?

Here's the full program if you want to take a look
http://pastebin.com/KyY103Ac


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