Zig

Check if an Email Was Received Digitally Signed

Demonstrates the read-only Chilkat Email.ReceivedSigned property, which is true if the email was originally received carrying one or more digital signatures. Knowing a message was signed is separate from knowing the signature checked out, so this example also reads SignaturesValid to report whether the signed content verified.

Background: A digital signature on an email (S/MIME) provides two things: authenticity (it was really sent by the holder of a particular certificate) and integrity (the content was not altered in transit). The sender signs a hash of the message with their private key; the recipient verifies it with the sender's public certificate. ReceivedSigned simply tells you a signature is present — verifying it is a separate step exposed through SignaturesValid.

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Zig

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

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

    // Demonstrates the read-only Email.ReceivedSigned property, which is true if this
    // email was originally received with a digital signature.  Use SignaturesValid to
    // determine whether the signed content actually verified.

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

    email.loadEml("qa_data/eml/signed.eml") catch {
        std.debug.print("{s}\n", .{try email.getLastErrorText(alloc)});
        return;
    };

    if (email.getReceivedSigned()) {
        std.debug.print("This email was received with a digital signature.\n", .{});
        if (email.getSignaturesValid()) {
            std.debug.print("All signatures are valid.\n", .{});
        } else {
            std.debug.print("One or more signatures are NOT valid.\n", .{});
        }
    } else {
        std.debug.print("This email was not signed.\n", .{});
    }

    // Note: Paths such as "qa_data/..." are relative local filesystem paths,
    // relative to the current working directory of the running application.
}