Lua

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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Lua

local chilkat = require("chilkat")

-- 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.

local email = chilkat.Email.new()

local success = email:load_eml("qa_data/eml/signed.eml")
if not success then
    print(email.last_error_text)
    return
end

if email.received_signed then
    print("This email was received with a digital signature.")
    if email.signatures_valid then
        print("All signatures are valid.")
    else
        print("One or more signatures are NOT valid.")
    end
else
    print("This email was not signed.")
end

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