加载私钥

要直接从磁盘加载私钥，请使用 PEM_read_PrivateKey 函数：

FILE *f;
EVP_PKEY *pkey;
f = fopen("key.pem", "rb");
PEM_read_PrivateKey(
    f,     /* use the FILE* that was opened */
    &pkey, /* pointer to EVP_PKEY structure */
    NULL,  /* password callback - can be NULL */
    NULL   /* parameter passed to callback or password if callback is NULL */
);

要从 BIO 加载私钥，请使用 PEM_read_bio_PrivateKey ：

BIO *bio;
bio = BIO_new_mem_buf((void *)input, input_len);
PEM_read_bio_PrivateKey(
    bio,   /* BIO to read the private key from */
    &pkey, /* pointer to EVP_PKEY structure */
    NULL,  /* password callback - can be NULL */
    NULL   /* parameter passed to callback or password if callback is NULL */
);