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Learn more about Teams // write rsa private key to file bio_private = BIO_new_file("private_new.pem", "w+"); ret = PEM_write_bio_PrivateKey(bio_private, pkey, NULL, NULL, 0, NULL, NULL); if (ret != 1) { goto cleanup; BIO_flush(bio_private); // write rsa public key to file bio_public = BIO_new_file("public_new.pem", "w+"); ret = PEM_write_bio_PUBKEY(bio_public, pkey); if (ret != 1) { goto cleanup; BIO_flush(bio_public);

instead of using

PEM_write_bio_PrivateKey(bio_private, pkey, NULL, NULL, 0, NULL, NULL);
I want the generated key text to be put into a string and NOT a file. I don't want it written to disk, just to a string in memory.  Is there a PEM_ function to do this? or any other way?  Thanks a lot for your help
                Very close to a duplicate of How to get PEM encoded X509 certificate as C++ string using openssl?, Convert OpenSSL x509 data to std::string, How to get PKCS7_sign result into a char * or std::string, etc. They are using std::strings instead of C strings. If using C strings, then be careful of embedded NULLs.
– jww
                Mar 14, 2017 at 15:11
as seen here.
You can use long BIO_get_mem_data(BIO *b, char **pp) to access the data in the BIO:
  
BIO_get_mem_data() sets pp to a pointer to the start of the memory BIOs data and returns the total amount of data available. It is implemented as a macro.
Thanks for Artjom's answer above. It worked! Here is the relevant code with the change :
/* Generate key */
if (EVP_PKEY_keygen(ctx, &pkey) <= 0)
    goto cleanup;
// write private key to memory
bio_private = BIO_new(BIO_s_mem());
ret = PEM_write_bio_PrivateKey(bio_private, pkey, NULL, NULL, 0, NULL, NULL);
if (ret != 1)
goto cleanup;
BIO_flush(bio_private);
BIO_get_mem_data(bio_private, &private_key_text);
cout << "PRIVE KEY :\n" << private_key_text << endl;
// write public key to memory
bio_public = BIO_new(BIO_s_mem());    
ret = PEM_write_bio_PUBKEY(bio_public, pkey);
if (ret != 1)
goto cleanup;
BIO_flush(bio_public);
BIO_get_mem_data(bio_public, &public_key_text);
cout << "PUBLIC KEY :\n" << public_key_text << endl;
                If private_key_text is a binary representation of the key, then you cannot simply treat it as a string. Binary data may contain \0 which is the string end character. So, it might happen that you print an incomplete key. The same goes for the public key.
– Artjom B.
                Mar 13, 2017 at 22:12
                you are right, but this is just to test that the code worked. I don't intend to print it out, I intend to use in-memory while the server is up and running, then re-generate it on re-start of the server. Thanks a lot!
– seedhom
                Mar 13, 2017 at 22:19
        
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