-/**
- * Decrypt a buffer using a private key.
- *
- * \param key_file Full path of the key.
- * \param outbuf The output buffer.
- * \param inbuf The encrypted input buffer.
- * \param inlen The length of \a inbuf in bytes.
- *
- * The \a outbuf must be large enough to hold at least \a rsa_inlen bytes.
- *
- * \return The size of the recovered plaintext on success, negative on errors.
- *
- * \sa RSA_private_decrypt(3)
- **/