Zig

Get the S/MIME Signer's Certificate

Demonstrates the Chilkat Mime.LastSignerCert method, which loads the signer certificate at a zero-based index from the most recent successful verification (or security-unwrapping) into a Cert. The first argument is the signer index and the second is the receiving Cert.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: Verifying tells you the signature is mathematically valid, but you usually also need to know who signed — the subject, the issuer, the validity dates — to decide whether to trust it. This retrieves each signer's certificate after verification so your code can inspect and apply its own trust rules. A message can have multiple signers, so iterate from 0 to NumSignerCerts - 1.

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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();

    const mime = try chilkat.Mime.init();
    defer mime.deinit();
    mime.loadMimeFile("qa_data/signed.eml") catch {
        std.debug.print("{s}\n", .{try mime.getLastErrorText(alloc)});
        return;
    };

    // After a successful verification, load each signer's certificate to inspect it.  The 1st argument
    // is the zero-based signer index and the 2nd is a Cert object that receives the certificate.
    mime.verify() catch {
        std.debug.print("{s}\n", .{try mime.getLastErrorText(alloc)});
        return;
    };

    const n = mime.getNumSignerCerts();
    const cert = try chilkat.Cert.init();
    defer cert.deinit();
    var i: i32 = 0;
    i = 0;
    while (i < n) : (i += 1) {
        mime.lastSignerCert(i, cert) catch {
            std.debug.print("{s}\n", .{try mime.getLastErrorText(alloc)});
            return;
        };

        std.debug.print("Signer {d}: {s} (issued by {s})\n", .{ i, try cert.getSubjectCN(alloc), try cert.getIssuerCN(alloc) });
    }
}