Zig Requires Chilkat v11.0.0+

Verify an RSA Signature Against the Signed String

See more Apple Keychain Examples

Demonstrates how to validate an RSA Signature against the string that was signed. Zig

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

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

    var success: bool = false;

    // Create the same string we previously signed in this example:
    // RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

    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 base64_rsa_sig = "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ==";

    // Get the public key to be used for signature verification.
    const pub_key = try chilkat.PublicKey.init();
    defer pub_key.deinit();
    success = if (pub_key.loadFromFile("rsaKeys/chilkat-rsa-2048.pem")) true else |_| false;
    if (!success) {
        std.debug.print("{s}\n", .{try pub_key.getLastErrorText(alloc)});
        return;
    }

    const rsa = try chilkat.Rsa.init();
    defer rsa.deinit();
    success = if (rsa.usePublicKey(pub_key)) true else |_| false;
    if (!success) {
        std.debug.print("{s}\n", .{try rsa.getLastErrorText(alloc)});
        return;
    }

    // Verify the string against the signature.
    // We signed the utf-8 byte representation of the string, so we must indicate
    // to also validate against the utf-8 byte representation.
    rsa.setCharset("utf-8");
    rsa.setEncodingMode("base64");
    const signed_string = try sb.getAsString(alloc);

    success = if (rsa.verifyStringENC(signed_string, "sha256", base64_rsa_sig)) true else |_| false;
    if (!success) {
        std.debug.print("{s}\n", .{try rsa.getLastErrorText(alloc)});
        std.debug.print("Signature invalid.\n", .{});
    } else {
        std.debug.print("Signature valid.\n", .{});
    }
}