How to set password to zip file with libZip

Question

I'm using libZip in my project, I success to create zip file output, but I'm having difficulty to set a password to a zip file.

I'm calling the zip_set_default_password fucntion and I'm getting the OK response, but when I'm trying to extract it didn't ask for a password.

Code sample:

int CompressWithPassword(const char * psFileContent, int iFileSize, const char * pcPassword)
{
    zip_source *psZipSource = NULL;
    zip_int64_t iIndex = 0;
    int iError = EOK;
    const char * pcZipOutputPath = "/home/user/Documents/myzip.zip";

    // Open zip file.
    m_psZip =
            zip_open(pcZipOutputPath,
                    ZIP_CREATE /*Create the archive if it does not exist*/,
                    &iError);

    // Zip opend ?
    if(iError != ZIP_ER_OK)
    {
        Close();
        return iError;
    }

    // Generate zip source content.
    psZipSource =
            zip_source_buffer(m_psZip,
                              psFileContent,
                              iFileSize,
                              0);

    // Valid zip source ?
    if(psZipSource == NULL)
    {
        Close();
        iError = -1;
        return iError;
    }

    iIndex =
            zip_file_add(m_psZip,
                         pcZipOutputPath,
                         psZipSource, ZIP_FL_OVERWRITE);
    if(iIndex < 0)
    {    
        Close();
        return iIndex;
    }

    // Create password
    int iRetPassword =
                zip_set_default_password(m_psZip, pcPassword);

    // password set ?
    if (iRetPassword == -1)
    {
        Close();
        return iRetPassword;
    }

    // Close zip file.
    Close();

    return iError;
}

When I'm calling this function, I'm getting OK and the zip file is created, What I'm missing here?

LibZip version 1.1.3-1, OS: fedora 25

Thanks.

Answer 1

I saw that has a lot of people searching by this question, then i'll make an example of zip_file_set_encryption, the method basically ask for zip archive, file index,encryption method and the password:

int main(){
    int errCode = 0;
    zip *z = zip_open("package.zip",ZIP_CREATE,&errCode);

    zip_source_t *source;

    char buffer[] = "Hello world!";
    source = zip_source_buffer(z,buffer,strlen(buffer),0);
    zip_file_add(z,"example.txt",source,0);

    /* Available encryption methods: 
    ZIP_EM_AES_128
    ZIP_EM_AES_192
    ZIP_EM_AES_256
    */

    zip_file_set_encryption(z,/* Index of the file */ 0,/* Encryption method */ ZIP_EM_AES_256,/* Password to encrypt file */ "myPassword");

    zip_close(z);
};

then when i use 7-zip to open the zip file created by my program:

7z e package.zip  

It just prompt the password to me, if you type the correct then the files in your workspace will be filled with the content:

Enter password (will not be echoed):

with the libzip is possible set file password by name, but with a little process before:

int main(){
    int errCode = 0;
    zip *z = zip_open("package.zip",ZIP_CREATE,&errCode);

    zip_source_t *source;

    char buffer[] = "Hello world!";
    source = zip_source_buffer(z,buffer,strlen(buffer),0);
    zip_file_add(z,"example.txt",source,0);

    source = zip_source_buffer(z,buffer,strlen(buffer),0);
    zip_file_add(z,"example2.txt",source,0);

    // Create struct of file stat
    struct zip_stat st;

    // Fill the struct with the file name that you want
    zip_stat(z,"example2.txt",0,&st);

    // Set the password to the file using index that had got by name

    /* Available encryption methods: 
    ZIP_EM_AES_128
    ZIP_EM_AES_192
    ZIP_EM_AES_256
    */

    zip_file_set_encryption(z,/* Index of file */ st.index, /* encryption method */ ZIP_EM_AES_256, /* password */"myPassword");

    zip_close(z);
};

I'm creating an wrapper for libzip (not complete yet), an easy way to interact with zip files, the GitHub URL is there: https://github.com/Romulo-Moraes/zipCrafter

Caution, if you set an password to a file, you should set the same password for the whole zip file, cause it can generate an error when you try open with 7-zip, it will try open the first file with your password then will try the same password for the whole zip.

Some unzip program versions will skip your file that was set with password by libzip, i recommend 7-zip

Answer 2

As written in the Libzip Documentation here, 'zip_set_default_password' will "sets the default password used when accessing encrypted files", if you use 'zip_fopen' to open files. otherwise, if you have a different password for single files you can use 'zip_fopen_encrypted' to open them.

If you want to encrypt files you add to an archive you need to use 'zip_file_set_encryption' with (m_psZip, iIndex, method you choose, pcPassword).