This is for a homework assignment!
I get the server’s certificate using get_peer_certificate()
and the calling dump_certificate to dump the certificate in a variable. The format is PEM and looks right to me.
-----BEGIN CERTIFICATE----- GIBBERISH................ ...................... ........................ -----END CERTIFICATE-----
How do I extract the server’s public key from this file (‘server.pubkey’) and encrypt plaintext using RSA algorithm and any python library. At the time of writing this, I am using pyOpenSSL
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Answer
I’d recommend using a more broad crypto library such as M2Crypto which has the X509 certificate functions as well as RSA encryption:
from M2Crypto import RSA, X509
data = ssl_sock.getpeercert(1)
# load the certificate into M2Crypto to manipulate it
cert = X509.load_cert_string(data, X509.FORMAT_DER)
pub_key = cert.get_pubkey()
rsa_key = pub_key.get_rsa()
cipher = rsa_key.public_encrypt('plaintext', RSA.pkcs1_padding)