How to write key pair to a string?

[deltadecay]

Hello, I want to write a key pair EvpPKey to an IOBuffer in PEM format. How can I do that?

I assumed this would work:

using OpenSSL

rsa_key = OpenSSL.EvpPKey(rsa_generate_key())
io = IOBuffer()
write(io, rsa_key)

but it throws an error

OpenSSL.OpenSSLError("404824FD01000000:error:04880007:PEM routines:PEM_write_bio:BUF lib:crypto/pem/pem_lib.c:664:\n")

For the public key I wrote this function

function write_pubkey(io::IO, evp_pkey::OpenSSL.EvpPKey)
    bio = OpenSSL.BIO(io)
    GC.@preserve bio io begin
        # int PEM_write_bio_PUBKEY(BIO *bp, EVP_PKEY *x);
        if ccall(
            (:PEM_write_bio_PUBKEY, libcrypto),
            Cint,
            (OpenSSL.BIO, OpenSSL.EvpPKey),
            bio,
            evp_pkey) != 1
            throw(OpenSSL.OpenSSLError())
        end
    end
end

using OpenSSL

rsa_key = OpenSSL.EvpPKey(rsa_generate_key())
io = IOBuffer()
write_pubkey(io, rsa_key)

and get the same error

OpenSSL.OpenSSLError("404824FD01000000:error:04880007:PEM routines:PEM_write_bio:BUF lib:crypto/pem/pem_lib.c:664:\n")

Is there something I'm missing when it comes to configuring the IOBuffer and the OpenSSL.BIO?