How to decode a base64 string from aes 128 in cbc mode?

[neoflume]

I have a string which is encoded in aes-128-cbc.
I have a key in the form of string.
IV is not needed, I think. Because its 16 bytes of zeroes.

I'm translating nodejs to rust. These three lines I'm trying to do it in rust.

      var decipher  = crypto.createDecipheriv ('aes-128-cbc',key, iv);
      var PlainText = decipher.update (EncEncodedBuffer , 'base64', 'utf8');
      PlainText += decipher.final('utf8');

For my case, I'm using only aes-128-cbc. So, I don't want large library like nodejs crypto to handle it.
So, how to do this?

[LegionMammal978]

You can do this with the base64, aes, and cbc crates.

/*
[dependencies]
aes = "0.8.2"
base64 = "0.13.1"
cbc = { version = "0.1.2", features = ["alloc"] }
*/

use aes::cipher::{block_padding::Pkcs7, BlockDecryptMut, KeyIvInit};
use std::str;

type Aes128CbcDec = cbc::Decryptor<aes::Aes128>;

fn main() {
    let key = [
        142, 46, 73, 7, 14, 216, 229, 77, 195, 183, 29, 93, 159, 38, 53, 163,
    ];
    let ciphertext = "tCmGLnG7+tKGSFBhtkn+sg==";
    let ciphertext = base64::decode(&ciphertext).unwrap();
    let decryptor = Aes128CbcDec::new(&key.into(), &[0; 16].into());
    let plaintext = decryptor
        .decrypt_padded_vec_mut::<Pkcs7>(&ciphertext)
        .unwrap();
    let plaintext = str::from_utf8(&plaintext).unwrap();
    println!("{plaintext}");
}

Note that the base64 crate will not accept any whitespace in the Base64-encoded string: you'll have to filter out any whitespace before passing it into base64::decode(). Otherwise, it should be roughly equivalent to your Node.js snippet. You mention that you don't want large libraries, but it can't get much smaller than these three: they add 1.5 MB to a debug build, 33 kB to a release build, or 23 kB to a release build with LTO.

[neoflume]

Thanks