If you can use Python, it is even easier if you have the pyopenssl
module. Here it is:
from OpenSSL import crypto
# May require "" for empty password depending on version
with open("push.p12", "rb") as file:
p12 = crypto.load_pkcs12(file.read(), "my_passphrase")
# PEM formatted private key
print crypto.dump_privatekey(crypto.FILETYPE_PEM, p12.get_privatekey())
# PEM formatted certificate
print crypto.dump_certificate(crypto.FILETYPE_PEM, p12.get_certificate())