Reading RSA keys from .PEM file to RSA structure in C

问题

JKJS

Observations:

Suppose RSA private key is created by following commands:

openssl genrsa -out mykey.pem 1024

Then, there is no problem reading key from that file in C:

RSA *privatekey=NULL;
privatekey=PEM_read_RSAPrivateKey(fp,NULL,NULL,NULL);
if(privatekey==NULL)
ERR_print_errors_fp(stderr);

But, if RSA keypair is created by following command:

openssl req -newkey rsa:1024 -sha1 -keyout mykey.pem -out rootreq.pem

Then reading from mykey.pem results in error. Why?

JKJS Hardik

回答1:

In the 2nd, command, did you give a passphrase? Open the key created by the 2nd command in any editor - do you see ENCRYPTED in the haders?

If yes, then that's why you aren't able to read it using PEM_read_RSAPrivateKey because you are passing 3rd param as NULL.

Pass a callback to get a password in the call to PEM_read_RSAPrivateKey.

Alternately you can remove the password from the key by using the following command

openssl rsa -in mykey.pem -out mykey1.pem.

This will ask you for a passphrase - if you give the right passphrase, you will get the key in an unencrypted form in mykey1.pem

来源：https://stackoverflow.com/questions/13659613/reading-rsa-keys-from-pem-file-to-rsa-structure-in-c