Rails: Digitally sign outgoing emails (S/MIME)
In this article, I will introduce one method to digitally sign outgoing emails with S/MIME using Ruby on Rails.
require ‘openssl’ vs. Kernel.system openssl
At first, I tried to sign mails using the Ruby OpenSSL library which is basically a lightweight wrapper for libopenssl. However, I was not successful; I found out how to create PKCS7 signatures in general, but not especially for S/MIME mails.
So I decided to use the openssl command line tool that can be invoked like this:
openssl smime -sign -signer $CERT_FILE -passin pass:$CERT_PASS
-in $UNSIGNED_MAIL -out $SIGNED_MAIL -certfile $CERT_CA_FILE
-from ‘your ’ -to ‘recipients <email@address>’
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