QT C++ - OpenSSL AES - EVP.h

I've been trying to use OpenSSL with QT in the past few days but the documentation and the examples are rare or none.

Anyway, I come up with this code:

void qkCrypto::AES_CBC(const unsigned char *string, const unsigned char *key, const unsigned char *iv)
{

    int outlen;
    unsigned char *out;

    EVP_CIPHER_CTX ctx;
    EVP_CIPHER_CTX_init(&ctx);
    const EVP_CIPHER *cipher = EVP_aes_128_cbc();

    EVP_EncryptInit(&ctx,cipher,key,iv);
    EVP_EncryptUpdate(&ctx,out,&outlen,string,strlen(string));

    EVP_EncryptFinal(&ctx,out,&outlen);

    EVP_CIPHER_CTX_cleanup(&ctx);

    qDebug() << out;

}

But when I compile it I get some error... this are conversion and cast errors and since I'm not the best C++ programmer out there I would really appreciate some help to solve them:

[...]/qkcrypto.cpp: In member function 'void qkCrypto::AES_CBC(const unsigned char*, const unsigned char*, const unsigned char*)':
[...]/qkcrypto.cpp:39: error: invalid conversion from 'const unsigned char*' to 'const char*'
[...]/qkcrypto.cpp:39: error: initializing argument 1 of 'size_t strlen(const char*)'

Anyway, how can I make this more QT friendly converting the chars to QByteArrays?

Best Regards, Thank you all ;)

---

Code Update

I've been "messing around" and I'm trying to do this without any luck:

void qkCrypto::AES_CBC(QByteArray string, QByteArray key, QByteArray iv)
{

    int outlen;
    QByteArray out;

    EVP_CIPHER_CTX ctx;
    EVP_CIPHER_CTX_init(&ctx);
    const EVP_CIPHER *cipher = EVP_aes_128_cbc();

    EVP_EncryptInit(&ctx,cipher, key.constData() , iv.constData() );
    EVP_EncryptUpdate(&ctx, out.constData() ,&outlen, string.constData() ,strlen((const char*)string));

    EVP_EncryptFinal(&ctx, out.constData() ,&outlen);

    EVP_CIPHER_CTX_cleanup(&ctx);

    qDebug() << "OUT: "<< out;


}

I got lot's of errors regarding to the conversions:

[...]/qkcrypto.cpp: In member function 'void qkCrypto::AES_CBC(QByteArray, QByteArray, QByteArray)':
[...]/qkcrypto.cpp:38: error: invalid conversion from 'const char*' to 'const unsigned char*'
[...]/qkcrypto.cpp:38: error:   initializing argument 3 of 'int EVP_EncryptInit(EVP_CIPHER_CTX*, const EVP_CIPHER*, const unsigned char*, const unsigned char*)'
[...]/qkcrypto.cpp:38: error: invalid conversion from 'const char*' to 'const unsigned char*'
[...]/qkcrypto.cpp:38: error:   initializing argument 4 of 'int EVP_EncryptInit(EVP_CIPHER_CTX*, const EVP_CIPHER*, const unsigned char*, const unsigned char*)'
[...]/qkcrypto.cpp:39: error: invalid conversion from 'const char*' to 'unsigned char*'
[...]/qkcrypto.cpp:39: error:   initializing argument 2 of 'int EVP_EncryptUpdate(EVP_CIPHER_CTX*, unsigned char*, int*, const unsigned char*, int)'
[...]/qkcrypto.cpp:39: error: invalid conversion from 'const char*' to 'const unsigned char*'
[...]/qkcrypto.cpp:39: error:   initializing argument 4 of 'int EVP_EncryptUpdate(EVP_CIPHER_CTX*, unsigned char*, int*, const unsigned char*, int)'
[...]/qkcrypto.cpp:41: error: invalid conversion from 'const char*' to 'unsigned char*'
[...]/qkcrypto.cpp:41: error:   initializing argument 2 of 'int EVP_EncryptFinal(EVP_CIPHER_C开发者_JAVA百科TX*, unsigned char*, int*)'

Thanks.

---

Well, as the error says, you're trying to convert between pointers to char and to unsigned char, which is not allowed. You have to add an explicit cast, e.g.

EVP_EncryptUpdate(&ctx, out, &outlen, string, strlen((const char*)string));
                                                     ^^^^^^^^^^^^^

---

It seems like strlen requires a const pointer to a signed char. So you need to cast that one. Either using the plain C casts ((const char*)), static_cast<const char*> or reinterpret_cast<const char*>. All should go well.

---

Anyway, how can I make this more QT friendly converting the chars to QByteArrays?

Looking at the documentation, the easiest solution would be something like this:

QByteArray arr((const char*)string);

---

I've new code now almost perfect.

QByteArray qkCrypto::encrypt_AES_CBC(QByteArray string, QByteArray key, QByteArray ivv)
{

    char mykey[EVP_MAX_KEY_LENGTH] = { 0 };
    strcpy(mykey,key.constData());

    char iv[EVP_MAX_IV_LENGTH] = { 0 };
    strcpy(iv,ivv.constData());

    char ciphertext[1024];

    const EVP_CIPHER *cipher = EVP_aes_256_cbc();
    int in_len;
    int out_len=0;

    in_len = (string.length());

    qDebug() << "Before encrypt: " << string << "\r\n";

         EVP_EncryptInit(&ctx, cipher, (const unsigned char*)mykey, (const unsigned char*)iv);
         EVP_EncryptUpdate(&ctx, ( unsigned char*)ciphertext, &out_len, (const unsigned char*)string.data(), in_len);
         EVP_EncryptFinal(&ctx, ( unsigned char*)&ciphertext[out_len], &out_len);
    EVP_CIPHER_CTX_cleanup(&ctx);
    qDebug() << "Encrypted: " << ciphertext << "\r\n";

    return ciphertext;

}

By some reason the output is only right some times... other times the output is wrong and I can't decrypt it later with OpenSSL.

What's wrong about this? :S

Thanks.