Zig

RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

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Demonstrates how RSA sign the utf-8 byte representation of a string to get the signature in base64 format. Zig

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

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

    // Assuming the smartcard/USB token is installed with the correct drivers from the manufacturer,
    // this code can work on multiple platforms including Windows, MacOS, Linux, and iOS.

    // Chilkat automatically detects and determines the way in which the HSM is used,
    // which can be by PKCS11, Apple Keychain, Microsoft CNG / Crypto API, or ScMinidriver.

    const cert = try chilkat.Cert.init();
    defer cert.deinit();

    // Set the token/smartcard PIN prior to loading.
    cert.setSmartCardPin("123456");

    // Specify the certificate by its common name.
    cert.loadFromSmartcard("cn=chilkat-rsa-2048") catch {
        std.debug.print("{s}\n", .{try cert.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("Signing with cert: {s}\n", .{try cert.getSubjectCN(alloc)});

    // Create a string to be hashed and signed.
    const sb = try chilkat.StringBuilder.init();
    defer sb.deinit();
    const crlf_line_ending = true;
    var i: i32 = 0;
    i = 0;
    while (i <= 10) : (i += 1) {
        sb.appendLine("This is a test.", crlf_line_ending) catch {};
    }

    const rsa = try chilkat.Rsa.init();
    defer rsa.deinit();

    // Use the certificate's private key for signing.
    rsa.setX509Cert(cert, true) catch {
        std.debug.print("{s}\n", .{try rsa.getLastErrorText(alloc)});
        return;
    };

    // Sign the SHA-256 hash of the utf-8 byte representation of the contents of sb
    // Return the signature in base64 format.
    rsa.setEncodingMode("base64");
    rsa.setCharset("utf-8");
    const string_to_sign = try sb.getAsString(alloc);
    const sig_base64 = rsa.signStringENC(alloc, string_to_sign, "sha256") catch {
        std.debug.print("{s}\n", .{try rsa.getLastErrorText(alloc)});
        return;
    };

    std.debug.print("RSA signature as base64: {s}\n", .{sig_base64});
}