Send secure email messages/files using SSL public certificate without PGP keys

openssl_hack.sh

# https://www.madboa.com/geek/openssl - Some usefull openssl cooks.
# If you couldn't find somebody's PGP key, you can still send secure 
# email using their SSL public certificate
# Fetching public certificate from example.com server and grabing the key from stream.
openssl s_client -connect example.com:443 | sed -ne \
        '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > publickey.pem
 
# Encrypting a file/message using retrieved public certificate.
# You can choose another encryption algorithms, rather than `des3`.
# If a file is a binary file, you must put `-binary` option.
openssl smime -encrypt [-binary] [-des3] -in secret.xxx \
        -from foo@bar.com -to mail@example.com \
        -subject "Top secret message/file" \
        -out secret.enc.txt publickey.pem  
 
# Decrypting the encrypted file/message using private key (placed to example.com server).
# The `-binary` & `-des3` options are optional.
openssl smime -decrypt [-binary] [-des3] -in secret.enc.txt \
        -out secret.xxx -inkey privatekey.pem