关于rust:rust-aes256加密-为什么-加密结果无法输出字符串

[dependencies]

aes = "0.8.2"
ecb = "0.1.1"

use aes::cipher::{block_padding::Pkcs7, BlockDecryptMut, BlockEncryptMut, KeyInit};type Aes256CbcEnc = ecb::Encryptor<aes::Aes256>;type Aes256CbcDec = ecb::Decryptor<aes::Aes256>;// const KEY: &[u8; 16] = b"abcdedghijklmnop"; // 模仿密钥，请勿在理论程序中应用const key: &[u8; 32] = b"ec3d170007120634a792c6c7b694e336";/// 加密pub fn encrypt(plain: &[u8]) -> Vec<u8> {    // 随机值    let mut buf = [0u8; 48];    let pt_len = plain.len();    buf[..pt_len].copy_from_slice(plain);    let ct = Aes256CbcEnc::new(key.into())        .encrypt_padded_b2b_mut::<Pkcs7>(plain, &mut buf)        .unwrap();    ct.to_vec()}/// 解密pub fn decrypt(cipher: &[u8]) -> Vec<u8> {    let cipher_len = cipher.len();    let mut buf = [0u8; 48];    buf[..cipher_len].copy_from_slice(cipher);    let pt = Aes256CbcDec::new(key.into())        .decrypt_padded_b2b_mut::<Pkcs7>(cipher, &mut buf)        .unwrap();    pt.to_vec()}fn main() {    // 账号密码应为单向加密，参考：https://github.com/RustCrypto/password-hashes    // 这里的示例代码利用来加密如手机号、身份证号、银行卡号等波及用户隐衷的数据    let plain = b"admin";    let ct = encrypt(plain);    let ct2 = ct.clone();    println!("加密后果{:?}", String::from_utf8(ct2));//加密后果Err(FromUtf8Error { bytes: [225, 51, 115, 113, 36, 252, 95, 73, 227, 166, 134, 32, 50, 140, 248, 43], error: Utf8Error { valid_up_to: 0, error_len: Some(1) } })    // let text = "4TNzcST8X0njpoYgMoz4Kw==".as_bytes().to_vec();    let pt = decrypt(&ct);    println!("解密后果：{:?}", String::from_utf8(pt));//解密后果：Ok("admin")}