STL files into readable text

[Mani_kandan]

is there any step in qt for encrypting and decrypting the file using openssl

[raven-worx]

@Mani_kandan
stl are encoded either in ASCII (plain text) or binary format.
the binary format is not security encrypted, so OpenSSL wont help you here.

you will need to follow the binary format specification and read the binary directly.
pseudo code taken from wikipedia:

UINT8[80]         -   Header
UINT32            -   triangle count
foreach triangle
  REAL32[3]       -    vector
  REAL32[3]       -    Vertex 1
  REAL32[3]       -    Vertex 2
  REAL32[3]       -    Vertex 3
  UINT16          -    attribute byte count
end

what is your actual use case? do you want to display the STL file?

[Mani_kandan]

@raven-worx thanks @raven-worx but I don't know how to read the binary directly

[KroMignon]

@Mani_kandan said in STL files into readable text:

but I don't know how to read the binary directly

You could take a look at this https://github.com/sreiter/stl_reader

[Mani_kandan]

@Mani_kandan code for ascii to string conversion in qt

[raven-worx]

@Mani_kandan
to me it looks like you are missing some basic fundamentals in programming/C++/Qt
and therefore IMO this task seems a bit too much to begin with

[Mani_kandan]

@raven-worx any one knows how to encrypt and decrypt the file in qt I m using openssl library for that

[Mani_kandan]

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTextEdit>
#include <QString>
#include <QDebug>
#include <QFile>
#include <QTextStream>
#include <QLabel>
#include <QFileDialog>
#include <QMessageBox>

// OpenSSL
#include <openssl/rsa.h>
#include <openssl/engine.h>
#include <openssl/aes.h>
#include <openssl/pem.h>
#include <openssl/conf.h>
#include <openssl/evp.h>
#include <openssl/err.h>
#include <openssl/bio.h>
#include <openssl/rand.h>
#include <openssl/randerr.h>

#define PADDING RSA_PKCS1_PADDING
#define KEYSIZE 32
#define IVSIZE 32
#define BLOCKSIZE 256
#define SALTSIZE 8


QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

    /**
     * @brief Encrypt a byte array with AES 256 CBC
     * @param data The byte array to encrypt
     * @return QByteArray
     */
    QByteArray encryptAES(QByteArray passphrase, QByteArray &data);

    /**
     * @brief Decrypt a byte array with AES 256 CBC
     * @param data The byte array to decrypt
     * @return QByteArray
     */
    QByteArray decryptAES(QByteArray passphrase, QByteArray &data);

    /**
     * @brief Get a byte array filled with random information
     * @param size The size of the byte array to generate
     * @return QByteArray
     */
    QByteArray randomBytes(int size);

private slots:

    void on_encrypt_clicked();

    void on_save_enc_clicked();

    void on_decrypt_clicked();

    void on_save_dec_clicked();

    void on_selecting_clicked();

private:
    Ui::MainWindow *ui;

    QByteArray encrypted;
    QString passphrase = "password";

};
#endif // MAINWINDOW_H


.**CPP**

#include "mainwindow.h"
#include "./ui_mainwindow.h"
#include "cipher.h"


MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}
QByteArray MainWindow::encryptAES(QByteArray passphrase, QByteArray &data)
{
    QByteArray msalt = randomBytes(SALTSIZE);
    int rounds = 1;
    unsigned char key[KEYSIZE];
    unsigned char iv[IVSIZE];

    const unsigned char* salt = (const unsigned char*) msalt.constData();
    const unsigned char* password = (const unsigned char*) passphrase.constData();

    int i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), salt,password, passphrase.length(),rounds,key,iv);

    if(i != KEYSIZE)
    {
        qCritical() << "EVP_BytesToKey() error: " << ERR_error_string(ERR_get_error(), NULL);
        return QByteArray();
    }

    EVP_CIPHER_CTX *en = EVP_CIPHER_CTX_new();
    EVP_CIPHER_CTX_init(en);

    if(!EVP_EncryptInit_ex(en, EVP_aes_256_cbc(),NULL,key, iv))
    {
        qCritical() << "EVP_EncryptInit_ex() failed " << ERR_error_string(ERR_get_error(), NULL);
        return QByteArray();
    }

    char *input = data.data();
    int len = data.size();

    int c_len = len + AES_BLOCK_SIZE, f_len = 0;
    unsigned char *ciphertext = (unsigned char*)malloc(c_len);

    if(!EVP_EncryptInit_ex(en, NULL, NULL, NULL, NULL))
    {
        qCritical() << "EVP_EncryptInit_ex() failed " << ERR_error_string(ERR_get_error(), NULL);
        return QByteArray();
    }

    // May have to repeat this for large files

    if(!EVP_EncryptUpdate(en, ciphertext, &c_len,(unsigned char *)input, len))
    {
        qCritical() << "EVP_EncryptUpdate() failed " << ERR_error_string(ERR_get_error(), NULL);
        return QByteArray();
    }

    if(!EVP_EncryptFinal(en, ciphertext+c_len, &f_len))
    {
        qCritical() << "EVP_EncryptFinal_ex() failed "  << ERR_error_string(ERR_get_error(), NULL);
        return QByteArray();
    }

    len = c_len + f_len;
    EVP_CIPHER_CTX_cipher(en);

    //ciphertext

    QByteArray encrypted = QByteArray(reinterpret_cast<char*>(ciphertext), len);
    QByteArray finished;
    finished.append("Salted__");
    finished.append(msalt);
    finished.append(encrypted);

    free(ciphertext);

    return finished;
}

QByteArray MainWindow::decryptAES(QByteArray passphrase, QByteArray &data)
{
    QByteArray msalt;
    if(QString(data.mid(0,8)) == "Salted__")
    {
        msalt = data.mid(8,8);
        data = data.mid(16);
    }
    else
    {
        qWarning() << "Could not load salt from data!";
        msalt = randomBytes(SALTSIZE);
    }

    int rounds = 1;
    unsigned char key[KEYSIZE];
    unsigned char iv[IVSIZE];
    const unsigned char* salt = (const unsigned char*)msalt.constData();
    const unsigned char* password = (const unsigned char*)passphrase.data();

    int i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), salt,password, passphrase.length(),rounds,key,iv);

    if(i != KEYSIZE)
    {
        qCritical() << "EVP_BytesToKey() error: " << ERR_error_string(ERR_get_error(), NULL);
        return QByteArray();
    }

    EVP_CIPHER_CTX *de=EVP_CIPHER_CTX_new();
    EVP_CIPHER_CTX_init(de);

    if(!EVP_DecryptInit_ex(de,EVP_aes_256_cbc(), NULL, key,iv ))
    {
        qCritical() << "EVP_DecryptInit_ex() failed" << ERR_error_string(ERR_get_error(), NULL);
        return QByteArray();
    }

    char *input = data.data();
    int len = data.size();

    int p_len = len, f_len = 0;
    unsigned char *plaintext = (unsigned char *)malloc(p_len + AES_BLOCK_SIZE);

    //May have to do this multiple times for large data???
    if(!EVP_DecryptUpdate(de, plaintext, &p_len, (unsigned char *)input, len))
    {
        qCritical() << "EVP_DecryptUpdate() failed " <<  ERR_error_string(ERR_get_error(), NULL);
        return QByteArray();
    }

    if(!EVP_DecryptFinal_ex(de,plaintext+p_len,&f_len))
    {
        qCritical() << "EVP_DecryptFinal_ex() failed " <<  ERR_error_string(ERR_get_error(), NULL);
        return QByteArray();
    }

    len = p_len + f_len;

    EVP_CIPHER_CTX_cleanup(de);


    QByteArray decrypted = QByteArray(reinterpret_cast<char*>(plaintext), len);
    free(plaintext);

    return decrypted;

}

QByteArray MainWindow::randomBytes(int size)
{

    unsigned char *arr= new unsigned char[size];
    RAND_bytes(arr,size);
    // int arr[size];
    //int RAND_bytes(unsigned char *buf,int num);

    QByteArray buffer = QByteArray(reinterpret_cast<char*>(arr), size);
    return buffer;
}
void MainWindow::on_selecting_clicked()
{
    QString filename=QFileDialog::getOpenFileName(this,"Open a file","F:/SoftwareTeam/Otherfiles/Manikandan/E&D_File");
    QFile file(filename);

    if(!file.open(QFile::ReadOnly | QFile::Text))
    {
        QMessageBox::warning(this,"title","file not open");

    }
    QTextStream in(&file);
    QString text = in.readAll();
    qDebug()<<text;
    ui->read_txt->setPlainText(text);


    file.close();
}

void MainWindow::on_encrypt_clicked()
{
    qDebug() << "Testing AES...";

    Cipher cWrapper;


    QByteArray plain = ui->read_txt->toPlainText().toLocal8Bit();
    encrypted = cWrapper.encryptAES(passphrase.toLatin1(),plain);
    ui->read_txt->setPlainText(encrypted);
    qDebug()<<"The plain text is:";
    qDebug() << plain;
    qDebug()<<"The text is encrypted";
    qDebug() << encrypted;


}

void MainWindow::on_save_enc_clicked()
{
    QString filename = QFileDialog::getSaveFileName(this,"Save as","F:/SoftwareTeam/Otherfiles/Manikandan/E&D_File");
    if(filename.isEmpty())
        return;

    QFile file(filename);

    if(!file.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Append))
        return;

    QTextStream out(&file);
    out<< ui->read_txt->toPlainText()<<"\n";

    file.close();

}


void MainWindow::on_decrypt_clicked()
{

    qDebug() << "Decrypting AES:";
    Cipher cWrapper;
    QByteArray decrypted = cWrapper.decryptAES(passphrase.toLatin1(),encrypted);
    qDebug()<<"The text is decrypted";
    qDebug() << decrypted;
     ui->read_txt->setText(decrypted);


}


void MainWindow::on_save_dec_clicked()
{
    //QString filter= "tr("Open 3D Object"),"",tr("3D Object(*.obj);;All files(*)");
    //QString filename = QFileDialog::getSaveFileName(this,"Save as","F:/SoftwareTeam/Otherfiles/Manikandan/E&D_File/objdec.obj/");
    QString filename = QFileDialog::getSaveFileName(this,
            tr("Save As"), "",
            tr("3D Object (*.obj);;All Files (*)"));
            //tr("DCM File (*.dcm);;All Files (*)"));
            //tr("STL File (*.stl);;All Files (*)"));
    if(filename.isEmpty())
        return;

    QFile file(filename);

    if(!file.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Append))
        return;

    QTextStream out(&file);
    out<< ui->read_txt->toPlainText()<<"\n";

    file.close();


}

[Mani_kandan]

@Mani_kandan in this code i m reading the file and encrypting the contents . I need a solution encrypt and decrypt the complete file without reading

[jsulm]

@Mani_kandan said in STL files into readable text:

I need a solution encrypt and decrypt the complete file without reading

What? How do you want to encrypt/decrypt a file without reading it?
Can you please try to explain better when asking?

[Mani_kandan]

@jsulm in the above code i m reading the contents inside the file and doing encryption and decryption. I have to know how to encrypt a complete and store its as encrypted file and decrypt the encrypted file .

[jsulm]

@Mani_kandan I really fail to understand what exact problem you have!
You are already reading whole file (though as text which is wrong for binary files).
You also write a file already.
So what EXACT problem/question do you have?

[Mani_kandan]

@jsulm I don't know how to explain it, but I need to encrypt the file as a file

[jsulm]

@Mani_kandan Sorry I give up as I have no idea what the problem is!
You are already reading the file, encrypting its content and writing encrypted content into another file.
No idea what you are asking...

[JonB]

@Mani_kandan
As @jsulm and I have been saying. If you have data in a file you want to encrypt you have to read the file to get the data to encrypt, so there is no point keep asking whether you can do it without reading the file content.

If you want to save the encrypted data back to a file you can do that. If you want the encrypted data to end up back in the same file as you read the encrypted data from: either read all the file content into memory, encrypt it, and write it back to the file you originally read from; or, read it a chunk at a time from the original file, write it encrypted a chunk at a time to a new, temporary file, and rename the new file to the original file right at the end.