Zig Requires Chilkat v11.0.0+
Send a Signed Email using RSASSA-PSS with SHA256

Demonstrates how to sign and send an email using the RSASSA-PSS signing algorithm with the SHA256 hash algorithm. .
Chilkat Zig Downloads

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.

    // Get a digital certificate with private key from a .pfx
    // (Chilkat has many different ways to provide a cert + private key for siging.
    // Using a PFX is just one possible option.)
    const pfx = try chilkat.Pfx.init();
    defer pfx.deinit();
    pfx.loadPfxFile("qa_data/rsassa-pss/privatekey.pfx", "PFX_PASSWORD") catch {
        std.debug.print("{s}\n", .{try pfx.getLastErrorText(alloc)});
        return;
    };

    const email = try chilkat.Email.init();
    defer email.deinit();

    // Create a simple email.
    email.setSubject("Sample RSASSA-PSS Signed Email");
    email.setBody("Sample RSASSA-PSS Signed Email");
    email.setFrom("from_name@mydomain.com");
    // Add one ore more recipients..
    email.addTo("Chilkat Support", "support@chilkatsoft.com") catch {};
    email.addTo("Chilkat GMail", "chilkat.support@gmail.com") catch {};

    // Indicate that the email is to be signed, and that we want to use RSASSA-PSS.
    email.setSendSigned(true);
    email.setSigningAlg("pss");
    email.setSigningHashAlg("sha256");

    // Get the certificate to be used for signing.
    // (The typical case for a PFX is that it contains a cert with an associated private key,
    // as well as other certificates in the chain of authentication.  The cert with the private
    // key should be in the first position at index 0.)

    const cert = try chilkat.Cert.init();
    defer cert.deinit();
    pfx.certAt(0, cert) catch {
        std.debug.print("{s}\n", .{try pfx.getLastErrorText(alloc)});
        return;
    };

    // Tell the email object to use this cert (and private key) for signing.
    email.setSigningCert(cert) catch {};

    const mailman = try chilkat.MailMan.init();
    defer mailman.deinit();

    // Set the SMTP settings for your email account on your mail server.
    mailman.setSmtpUsername("SMTP_LOGIN");
    mailman.setSmtpPassword("SMTP_PASSWORD");
    mailman.setSmtpHost("MY_SMTP_DOMAIN_OR_IP");
    mailman.setSmtpPort(587);
    mailman.setStartTLS(true);

    // Signed email can be sent in two different ways.
    // In a multipart/signed email, the signature is attached as a separate MIME part.
    // In an opaque email (signedData) the content of the email is encapsulated within the signature
    // and the email is sent as "application/pkcs7-mime".
    // Either should be fine, but some receiving systems might require one or the other..
    mailman.setOpaqueSigning(false);

    // Send the email.  The mailman will sign the email as directed by the
    // property settings of the email object.
    mailman.sendEmail(email) catch {
        std.debug.print("{s}\n", .{try mailman.getLastErrorText(alloc)});
        return;
    };

    mailman.closeSmtpConnection() catch {
        std.debug.print("Connection to SMTP server not closed cleanly.\n", .{});
    };

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

    // -----------------------------------------------------------
    // This is the MIME of the RSASSA-PSS signed email that was sent

    //     MIME-Version: 1.0
    //     Date: Thu, 20 Apr 2017 10:14:58 -0500
    //     Message-ID: <3682A87344CB3A4FB5EB5BC9908C0C4DA01DA461@CHILKAT13>
    //     Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha256;
    //      boundary="------------050103020705000601010800"
    //     X-Priority: 3 (Normal)
    //     Subject: Sample RSASSA-PSS Signed Email
    //     From: support@chilkatsoft.com
    //     To: "Chilkat Support" <support@chilkatsoft.com>,
    //      "Chilkat GMail" <chilkat.support@gmail.com>
    //
    //     --------------050103020705000601010800
    //     Content-Type: text/plain; format=flowed
    //     Content-Transfer-Encoding: 7bit
    //
    //     Sample RSASSA-PSS Signed Email
    //     --------------050103020705000601010800
    //     Content-Transfer-Encoding: base64
    //     Content-Type: application/pkcs7-signature; name="smime.p7s"
    //     Content-Disposition: attachment; filename="smime.p7s"
    //
    //     MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg
    //     ggL4MIIC9DCCAl2gAwIBAgIJAMPsJCT11cniMA0GCSqGSIb3DQEBCwUAMIGSMQswCQYDVQQGEwJB
    //     VTERMA8GA1UECAwIVmljdG9yaWExEjAQBgNVBAcMCU1lbGJvdXJuZTEhMB8GA1UECgwYSW50ZXJu
    //     ZXQgV2lkZ2l0cyBQdHkgTHRkMQ8wDQYDVQQDDAZXaWRnZXQxKDAmBgkqhkiG9w0BCQEWGWFkbWlu
    //     QGludGVybmV0d2lkZ2V0cy5jb20wHhcNMTYxMTAxMTY1MjMyWhcNMjExMDMxMTY1MjMyWjCBkjEL
    //     MAkGA1UEBhMCQVUxETAPBgNVBAgMCFZpY3RvcmlhMRIwEAYDVQQHDAlNZWxib3VybmUxITAfBgNV
    //     BAoMGEludGVybmV0IFdpZGdpdHMgUHR5IEx0ZDEPMA0GA1UEAwwGV2lkZ2V0MSgwJgYJKoZIhvcN
    //     AQkBFhlhZG1pbkBpbnRlcm5ldHdpZGdldHMuY29tMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKB
    //     gQDGIdoCjyavs+F/Rm0VIB4m6O7VL1j+1IqieoR9NEX2GQvu2VCdceyxf9qaw1bxipEvjLwUkw7M
    //     e+BTlLpWQbBMH87s6KpsC8MVyXhMLpP0oM8NFix/vLz2wdLhUh7CZvJA0plqkJk9bj57QIu+EO1k
    //     tUHM2DFb6sckvCL2yybD1wIDAQABo1AwTjAdBgNVHQ4EFgQUONKKu2zsXIrinWxIGT654vrcQwsw
    //     HwYDVR0jBBgwFoAUONKKu2zsXIrinWxIGT654vrcQwswDAYDVR0TBAUwAwEB/zANBgkqhkiG9w0B
    //     AQsFAAOBgQArFvdi5u9i2QF1Qw+cdC1l7w2Y3+q6RIkln2W8rWJFje00644o8hXy7v46giJCedmF
    //     ULlhm1n7XIsZGy2W3lJ77v5agn9gFwXu1h3cqkGXkoteE6SQJQXWgsW3GWPveObvTL8LF4y57fgM
    //     9ZWS+V9MJajeu44Rf/tU17TLYKjvEjGCA7MwggOvAgEBMIGgMIGSMQswCQYDVQQGEwJBVTERMA8G
    //     A1UECAwIVmljdG9yaWExEjAQBgNVBAcMCU1lbGJvdXJuZTEhMB8GA1UECgwYSW50ZXJuZXQgV2lk
    //     Z2l0cyBQdHkgTHRkMQ8wDQYDVQQDDAZXaWRnZXQxKDAmBgkqhkiG9w0BCQEWGWFkbWluQGludGVy
    //     bmV0d2lkZ2V0cy5jb20CCQDD7CQk9dXJ4jANBglghkgBZQMEAgEFAKCCAjQwGAYJKoZIhvcNAQkD
    //     MQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTcwNDIwMTUxNDU4WjAvBgkqhkiG9w0BCQQx
    //     IgQgoHOtpFiAgti0cwDw46C8wyYSZbhx2yJqJZ/qRE8WPSQwXwYJKoZIhvcNAQkPMVIwUDALBglg
    //     hkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFAMAcGBSsO
    //     AwIHMA0GCCqGSIb3DQMCAgEoMIGxBgkrBgEEAYI3EAQxgaMwgaAwgZIxCzAJBgNVBAYTAkFVMREw
    //     DwYDVQQIDAhWaWN0b3JpYTESMBAGA1UEBwwJTWVsYm91cm5lMSEwHwYDVQQKDBhJbnRlcm5ldCBX
    //     aWRnaXRzIFB0eSBMdGQxDzANBgNVBAMMBldpZGdldDEoMCYGCSqGSIb3DQEJARYZYWRtaW5AaW50
    //     ZXJuZXR3aWRnZXRzLmNvbQIJAMPsJCT11cniMIGzBgsqhkiG9w0BCRACCzGBo6CBoDCBkjELMAkG
    //     A1UEBhMCQVUxETAPBgNVBAgMCFZpY3RvcmlhMRIwEAYDVQQHDAlNZWxib3VybmUxITAfBgNVBAoM
    //     GEludGVybmV0IFdpZGdpdHMgUHR5IEx0ZDEPMA0GA1UEAwwGV2lkZ2V0MSgwJgYJKoZIhvcNAQkB
    //     FhlhZG1pbkBpbnRlcm5ldHdpZGdldHMuY29tAgkAw+wkJPXVyeIwPQYJKoZIhvcNAQEKMDCgDTAL
    //     BglghkgBZQMEAgGhGjAYBgkqhkiG9w0BAQgwCwYJYIZIAWUDBAIBogMCASAEgYCDQpT6vJZ9zERJ
    //     JVX69PGUfCN5Eq9pKzoOTQSrIBe1YgNDSPd5pyOPP2MN1RpI0T/GTQZw4iWy5LZq0T5sjmk3fFVB
    //     +VZjKtkTuhGaCdzMQXomVLBbI2fN4UaA4v1/Ayrqr8SY9Rsa20TpKv/bufK7oYs083UOtlcA1EHY
    //     41wQ5A==
    //
    //     --------------050103020705000601010800--
}