An AES encryption/decryption program

I write a simple AES encryption/decryption program, not recommend using it, but show some basic concepts:

(1) Refer my previous post: initialise EVP_CIPHER_CTX only once, which can improve code efficiency:

......
    EVP_CIPHER_CTX *enc_ctx = EVP_CIPHER_CTX_new();

    if (EVP_EncryptInit_ex(enc_ctx, EVP_aes_128_ecb(), NULL, key, NULL) == 0) {
        goto END;
    }
......

(2) Because the key length is 128 bits, the cipher text length should be multiples of 16 bytes. The plain text length is 98; EVP_EncryptUpdate() will encrypt first 96 bytes, and EVP_EncryptFinal_ex() will encrypt the remaining 2 bytes. The total length of encrypted text is 112.

......
        if (EVP_EncryptUpdate(enc_ctx, ct, &ct_len, pt, sizeof(pt)) == 0) {
            goto END;
        }

        if (EVP_EncryptFinal_ex(enc_ctx, ct + ct_len, &len) == 0) {
            goto END;
        }

        ct_len += len;
......

Correspondingly, EVP_DecryptUpdate() will decrypt first 96 bytes, and EVP_DecryptFinal_ex() will decrypt the trailing 2 bytes:

......
        if (EVP_DecryptUpdate(dec_ctx, decrypted, &decrypted_len, ct, ct_len) == 0) {
            goto END;
        }

        if (EVP_DecryptFinal_ex(dec_ctx, decrypted + decrypted_len, &len) == 0) {
            goto END;
        }

        decrypted_len += len;
......