Zig Requires Chilkat v11.7.0+

Find Out Whether a PDF Needs a Password Before Loading It

See more PDF Protection Examples

Demonstrates PreLoadCheck, which examines a PDF file without loading it and without any password. It reports whether the file is encrypted, by which method and algorithm, whether a password is needed to open it, and what its permissions are. An application uses it to decide whether to ask for a password, or which certificate it needs, before calling LoadFile. PreLoadCheckBd does the same for a PDF held in memory. Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // The PDF used in this example is available at two_page_memo.pdf

    // The PDF used in this example is available at encrypted_user_password.pdf

    // The PDF used in this example is available at no_copy_permission.pdf

    const pdf = try chilkat.Pdf.init();
    defer pdf.deinit();
    const info = try chilkat.JsonObject.init();
    defer info.deinit();

    // A PDF that is not encrypted.  Nothing but "encrypted" is reported for it.
    pdf.preLoadCheck("qa_data/pdf/two_page_memo.pdf", info) catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("two_page_memo.pdf\n", .{});
    std.debug.print("  encrypted: {}\n", .{info.boolOf("encrypted")});

    // A PDF that needs a password to open.
    pdf.preLoadCheck("qa_data/pdf/encrypted_user_password.pdf", info) catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("encrypted_user_password.pdf\n", .{});
    std.debug.print("  encrypted: {}\n", .{info.boolOf("encrypted")});
    std.debug.print("  method: {s}\n", .{try info.stringOf(alloc, "method")});
    std.debug.print("  algorithm: {s}\n", .{try info.stringOf(alloc, "algorithm")});
    std.debug.print("  openPasswordRequired: {}\n", .{info.boolOf("openPasswordRequired")});

    // A PDF that opens without a password but is restricted.  The permissions are readable without
    // any password.
    pdf.preLoadCheck("qa_data/pdf/no_copy_permission.pdf", info) catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("no_copy_permission.pdf\n", .{});
    std.debug.print("  encrypted: {}\n", .{info.boolOf("encrypted")});
    std.debug.print("  openPasswordRequired: {}\n", .{info.boolOf("openPasswordRequired")});
    std.debug.print("  may copy: {}\n", .{info.boolOf("permissions.copy")});

    // The typical use: ask for a password only when one is needed, then load.
    pdf.preLoadCheck("qa_data/pdf/encrypted_user_password.pdf", info) catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    if (info.boolOf("openPasswordRequired")) {
        // An application would prompt for the password here.
        pdf.setUserPassword("secret");
    }

    pdf.loadFile("qa_data/pdf/encrypted_user_password.pdf") catch {
        std.debug.print("{s}\n", .{try pdf.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("loaded, pages: {d}\n", .{pdf.getNumPages()});

    // Sample output:

    // two_page_memo.pdf
    //   encrypted: False
    // encrypted_user_password.pdf
    //   encrypted: True
    //   method: password
    //   algorithm: rc4-128
    //   openPasswordRequired: True
    // no_copy_permission.pdf
    //   encrypted: True
    //   openPasswordRequired: False
    //   may copy: False
    // loaded, pages: 1
}