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Create CMS Signed File (PDF) with Multiple Signing Certificates

See more Digital Signatures Examples

Demonstrates how to sign a file by adding multiple signatures (multiple certificates). This example signs a PDF file to produce an output file that is a CMS signature wrapping the original PDF. (Note: This is different than modifying a PDF by injecting a signature into the PDF file format.)

Note: This example requires Chilkat v9.5.0.83 or greater.

Zig

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

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

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

    const crypt = try chilkat.Crypt2.init();
    defer crypt.deinit();

    // ------------ This example requires Chilkat v9.5.0.83 or greater.

    const cert1 = try chilkat.Cert.init();
    defer cert1.deinit();
    cert1.loadPfxFile("qa_data/pfx/cert_test123.pfx", "test123") catch {
        std.debug.print("{s}\n", .{try cert1.getLastErrorText(alloc)});
        return;
    };

    const cert2 = try chilkat.Cert.init();
    defer cert2.deinit();
    cert2.loadPfxFile("qa_data/pfx/test_secret.pfx", "secret") catch {
        std.debug.print("{s}\n", .{try cert2.getLastErrorText(alloc)});
        return;
    };

    // ------------ This example requires Chilkat v9.5.0.83 or greater.

    // Tell the crypt component to use both certificates for signing.
    // When we create the signature, it will be signed by both certificates.
    crypt.addSigningCert(cert1) catch {
        std.debug.print("{s}\n", .{try crypt.getLastErrorText(alloc)});
        return;
    };

    crypt.addSigningCert(cert2) catch {
        std.debug.print("{s}\n", .{try crypt.getLastErrorText(alloc)});
        return;
    };

    // The CadesEnabled property applies to all methods that create PKCS7 signatures.
    // To create a CAdES-BES signature, set this property equal to true.
    crypt.setCadesEnabled(true);

    crypt.setHashAlgorithm("sha256");

    // We can sign any type of file, creating a .p7s as output.
    // The .p7s contains the signature and also embeds the data of the file that is signed.
    const in_file = "qa_data/pdf/sample.pdf";
    const p7s_file = "qa_output/sample.pdf.p7s";

    // Create the CAdES-BES attached signature, which contains the original data.
    // Note: Chilkat's function naming is not accurate.  CreateP7M creates a PKCS7 signature where the signed file
    // is contained within the signature.  CreateP7S creates a detached PKCS7 signature where the signed file
    // is NOT contained within the signature.  We want the data to be contained in the signature, therefore
    // we call CreateP7M even though we are naming our output file .p7s.
    crypt.createP7M(in_file, p7s_file) catch {
        std.debug.print("{s}\n", .{try crypt.getLastErrorText(alloc)});
        return;
    };

    // Verify the .p7s file and extract the original file from the .p7s.
    const extracted_to_file_path = "qa_output/sample.pdf";
    crypt.verifyP7M(p7s_file, extracted_to_file_path) catch {
        std.debug.print("{s}\n", .{try crypt.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Success!\n", .{});
}