MIME S/MIME Signing Algorithm Properties

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Demonstrates the properties that control S/MIME signing: SigningAlg (the RSA signature scheme, PKCS1-V1_5 or RSASSA-PSS), SigningHashAlg (the message-digest algorithm), Micalg and Protocol (the micalg and protocol parameters of a multipart/signed Content-Type), and UseXPkcs7 (whether historical x-pkcs7 media-type names are used). The properties are configured before creating a detached signature.

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

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

    const mime = try chilkat.Mime.init();
    defer mime.deinit();
    mime.setBodyFromPlainText("This message will be signed.") catch {
        std.debug.print("{s}\n", .{try mime.getLastErrorText(alloc)});
        return;
    };

    // SigningAlg is the RSA signature scheme.  The default is PKCS1-V1_5; set RSASSA-PSS (or pss) for
    // RSASSA-PSS.
    mime.setSigningAlg("PKCS1-V1_5");

    // SigningHashAlg is the message-digest algorithm.  The default is sha256.
    mime.setSigningHashAlg("sha256");

    // Micalg and Protocol are the micalg and protocol parameters written into a multipart/signed
    // Content-Type header field.  They are normally set automatically, but can be controlled here.
    mime.setMicalg("sha-256");
    mime.setProtocol("application/pkcs7-signature");

    // UseXPkcs7 controls whether newly created S/MIME media types use the historical x-pkcs7 names.
    mime.setUseXPkcs7(false);

    // Load a signing certificate (with private key access) from a PFX.  The PFX password should come
    // from a secure source rather than being hard-coded.
    const pfx_password = "myPfxPassword";
    const cert = try chilkat.Cert.init();
    defer cert.deinit();
    cert.loadPfxFile("qa_data/signer.pfx", pfx_password) catch {
        std.debug.print("{s}\n", .{try cert.getLastErrorText(alloc)});
        return;
    };

    // Create the detached signature using the algorithms configured above.
    mime.addDetachedSignature(cert) catch {
        std.debug.print("{s}\n", .{try mime.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Signed with SigningAlg={s} SigningHashAlg={s}\n", .{ try mime.getSigningAlg(alloc), try mime.getSigningHashAlg(alloc) });
}