#include "qtoe.h"

using namespace std;

QtOE::QtOE(QObject *parent) : QObject(parent)
{
}

RSA* QtOE::createPrivateRSA(QString key, QString passphrase) {
    RSA *rsa = NULL;
    BIO *keybio;
    keybio = BIO_new(BIO_s_mem());
    BIO_puts(keybio, key.toStdString().c_str());

    if(passphrase != "")
        rsa = PEM_read_bio_RSAPrivateKey(keybio, NULL, 0, (void*)passphrase.toStdString().c_str());
    else
        rsa = PEM_read_bio_RSAPrivateKey(keybio, NULL, &QtOE::pem_password_callback, NULL);

    if(rsa == NULL || rsa == 0)
        qDebug() << "[ERROR][QtOE] There was a problem rading the private key!";

    return rsa;
}

RSA* QtOE::createPublicRSA(QString key) {
    RSA *rsa = NULL;
    BIO *keybio;
    keybio = BIO_new(BIO_s_mem());
    BIO_puts(keybio, key.toStdString().c_str());

    rsa = PEM_read_bio_RSA_PUBKEY(keybio, &rsa,NULL, NULL);
    return rsa;
}

RSA* QtOE::createPublicRSA(X509* cert) {
    if(cert == NULL)
        return 0;

    EVP_PKEY * pubkey;
    pubkey = X509_get_pubkey(cert);

    RSA * rsa;
    rsa = EVP_PKEY_get1_RSA(pubkey);
    return rsa;
}

X509* QtOE::createX509(QString cert) {
    X509 *x509 = NULL;
    BIO *certbio;
    certbio = BIO_new(BIO_s_mem());
    BIO_puts(certbio, cert.toStdString().c_str());
    x509 = PEM_read_bio_X509(certbio, &x509, NULL, NULL);
    return x509;
}

bool QtOE::RSASign( RSA* rsa,
                    const unsigned char* Msg,
                    size_t MsgLen,
                    unsigned char** EncMsg,
                    size_t* MsgLenEnc) {
    EVP_MD_CTX* m_RSASignCtx = EVP_MD_CTX_create();
    EVP_PKEY* priKey  = EVP_PKEY_new();
    EVP_PKEY_assign_RSA(priKey, rsa);
    if (EVP_DigestSignInit(m_RSASignCtx,NULL, EVP_sha256(), NULL,priKey)<=0) {
        return false;
    }
    if (EVP_DigestSignUpdate(m_RSASignCtx, Msg, MsgLen) <= 0) {
        return false;
    }
    if (EVP_DigestSignFinal(m_RSASignCtx, NULL, MsgLenEnc) <=0) {
        return false;
    }
    *EncMsg = (unsigned char*)malloc(*MsgLenEnc);
    if (EVP_DigestSignFinal(m_RSASignCtx, *EncMsg, MsgLenEnc) <= 0) {
        return false;
    }
    //EVP_MD_CTX_cleanup(m_RSASignCtx);
    return true;
}

bool QtOE::RSAVerifySignature( RSA* rsa,
                               unsigned char* MsgHash,
                               size_t MsgHashLen,
                               const char* Msg,
                               size_t MsgLen,
                               bool* Authentic) {
    *Authentic = false;
    EVP_PKEY* pubKey  = EVP_PKEY_new();
    EVP_PKEY_assign_RSA(pubKey, rsa);
    EVP_MD_CTX* m_RSAVerifyCtx = EVP_MD_CTX_create();

    if (EVP_DigestVerifyInit(m_RSAVerifyCtx,NULL, EVP_sha256(),NULL,pubKey)<=0) {
        return false;
    }
    if (EVP_DigestVerifyUpdate(m_RSAVerifyCtx, Msg, MsgLen) <= 0) {
        return false;
    }
    int AuthStatus = EVP_DigestVerifyFinal(m_RSAVerifyCtx, MsgHash, MsgHashLen);
    if (AuthStatus==1) {
        *Authentic = true;
        //EVP_MD_CTX_cleanup(m_RSAVerifyCtx);
        return true;
    } else if(AuthStatus==0){
        *Authentic = false;
        //EVP_MD_CTX_cleanup(m_RSAVerifyCtx);
        return true;
    } else{
        *Authentic = false;
        //EVP_MD_CTX_cleanup(m_RSAVerifyCtx);
        return false;
    }
}

void QtOE::Base64Encode( const unsigned char* buffer,
                         size_t length,
                         char** base64Text) {
    BIO *bio, *b64;
    BUF_MEM *bufferPtr;

    b64 = BIO_new(BIO_f_base64());
    bio = BIO_new(BIO_s_mem());
    bio = BIO_push(b64, bio);

    BIO_write(bio, buffer, length);
    BIO_flush(bio);
    BIO_get_mem_ptr(bio, &bufferPtr);
    BIO_set_close(bio, BIO_NOCLOSE);
    BIO_free_all(bio);

    *base64Text=(*bufferPtr).data;
}

size_t QtOE::calcDecodeLength(const char* b64input) {
    size_t len = strlen(b64input), padding = 0;

    if (b64input[len-1] == '=' && b64input[len-2] == '=') //last two chars are =
        padding = 2;
    else if (b64input[len-1] == '=') //last char is =
        padding = 1;
    return (len*3)/4 - padding;
}

void QtOE::Base64Decode(const char* b64message, unsigned char** buffer, size_t* length) {
    BIO *bio, *b64;

    int decodeLen = calcDecodeLength(b64message);
    *buffer = (unsigned char*)malloc(decodeLen + 1);
    (*buffer)[decodeLen] = '\0';

    bio = BIO_new_mem_buf(b64message, -1);
    b64 = BIO_new(BIO_f_base64());
    bio = BIO_push(b64, bio);

    *length = BIO_read(bio, *buffer, strlen(b64message));
    BIO_free_all(bio);
}

QString QtOE::signMessage(RSA* privateKey, QString plainText) {
    if(privateKey == 0 || privateKey == NULL || privateKey == nullptr) {
        qDebug() << "[ERROR][QtOE] private key must not be NULL!";
        return "";
    }

    unsigned char* encMessage;
    char* base64Text;
    size_t encMessageLength;
    RSASign(privateKey, (unsigned char*) plainText.toStdString().c_str(), plainText.length(), &encMessage, &encMessageLength);
    Base64Encode(encMessage, encMessageLength, &base64Text);
    free(encMessage);
    return base64Text;
}

bool QtOE::verifySignature(RSA* publicKey, QString plainText, QString signatureBase64) {
    if(publicKey == 0 || publicKey == NULL || publicKey == nullptr) {
        qDebug() << "[ERROR][QtOE] public key must not be NULL!";
        return false;
    }
    unsigned char* encMessage;
    size_t encMessageLength;
    bool authentic;
    Base64Decode(signatureBase64.toStdString().c_str(), &encMessage, &encMessageLength);
    bool result = RSAVerifySignature(publicKey, encMessage, encMessageLength, plainText.toStdString().c_str(), plainText.length(), &authentic);
    return result & authentic;
}

void QtOE::printCertBio(X509 *cert) {
    X509_NAME *subject = X509_get_subject_name(cert);

    // Print the subject into a BIO and then get a string
    BIO * bio = BIO_new(BIO_s_mem());
    X509_NAME_print_ex(bio, subject, 0, 0);

    // Create a buffer and zero it out
    const int& max_len = 4096;
    char buffer[max_len];
    memset(buffer, 0, max_len);
    // Read one smaller than the buffer to make sure we end up with a null
    // terminator no matter what
    BIO_read(bio, buffer, max_len - 1);

    std::string cert_subject = buffer;

    qDebug() << QString::fromStdString(cert_subject);
}

int QtOE::pem_password_callback(char *buf, int max_len, int flag, void *ctx)
{
    Q_UNUSED(buf);
    Q_UNUSED(max_len);
    Q_UNUSED(flag);
    Q_UNUSED(ctx);

    qDebug() << "[ERROR][QtOE] A passphrase was required for this key, but none was given!";
    return 0;
}