Add Support for CBC, CTR Cipher modes with AES 128 & 256 bit keys.

[skmcgrail]

Description of changes:

This pull request adds support for CBC and CTR cipher mode encryption for 128-bit and 256-bit AES keys.

• Introduces aws_lc_rs::cipher module which supports unauthenticated ciphers for encryption/decryption.
• PaddedBlockEncryptingKey, PaddedBlockDecryptingKey provide encryption/decryption of plaintext/ciphertext for block cipher modes using padding. PaddedBlockEncryptingKey::cbc_pkcs7(...) PaddedBlockDecryptingKey::cbc_pkcs7(...) and are the constructor methods provided for using CBC mode with PKCS#7 padding.
  • Users who need to explicitly set an initialization vector can use PaddedBlockEncryptingKey::less_safe_cbc_pkcs7.
• EncryptingKey, DecryptingKey provide encryption/decryption of plaintext/ciphertext for unpadded block cipher modes. PaddedBlockEncryptingKey::ctr(...) PaddedBlockDecryptingKey::ctr(...) and are the constructor methods provided for using CTR mode (unpadded).
  • Users who need to explicitly set an initialization vector can use EncryptingKey::less_safe_ctr.

API Usage Examples

AES-128 CBC

use aws_lc_rs::cipher::{
    PaddedBlockDecryptingKey, PaddedBlockEncryptingKey, UnboundCipherKey, AES_128,
};

let original_message = "This is a secret message!".as_bytes();
let mut in_out_buffer = Vec::from(original_message);

let key_bytes: &[u8] = &[
    0xff, 0x0b, 0xe5, 0x84, 0x64, 0x0b, 0x00, 0xc8, 0x90, 0x7a, 0x4b, 0xbf, 0x82, 0x7c, 0xb6,
    0xd1,
];

let key = UnboundCipherKey::new(&AES_128, key_bytes)?;
let encrypting_key = PaddedBlockEncryptingKey::cbc_pkcs7(key)?;
let context = encrypting_key.encrypt(&mut in_out_buffer)?;

let key = UnboundCipherKey::new(&AES_128, key_bytes)?;
let decrypting_key = PaddedBlockDecryptingKey::cbc_pkcs7(key)?;
let plaintext = decrypting_key.decrypt(&mut in_out_buffer, context)?;
assert_eq!(original_message, plaintext);

AES-128 CTR

use aws_lc_rs::cipher::{DecryptingKey, EncryptingKey, UnboundCipherKey, AES_128};

let original_message = "This is a secret message!".as_bytes();
let mut in_out_buffer = Vec::from(original_message);

let key_bytes: &[u8] = &[
    0xff, 0x0b, 0xe5, 0x84, 0x64, 0x0b, 0x00, 0xc8, 0x90, 0x7a, 0x4b, 0xbf, 0x82, 0x7c, 0xb6,
    0xd1,
];

let key = UnboundCipherKey::new(&AES_128, key_bytes)?;
let encrypting_key = EncryptingKey::ctr(key)?;
let context = encrypting_key.encrypt(&mut in_out_buffer)?;

let key = UnboundCipherKey::new(&AES_128, key_bytes)?;
let decrypting_key = DecryptingKey::ctr(key)?;
let plaintext = decrypting_key.decrypt(&mut in_out_buffer, context)?;
assert_eq!(original_message, plaintext);

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[samuel40791765]

initialization in initialization vector seems to be misspelled throughout the PR, so we might want to adjust that.

[skmcgrail]

#155 has some API improvements which will allow reuse of the Encrypt/Decrypt keys so that they aren't consumed by value after calling encrypt/decrypt. Will allow us a path for future optimizations if/when we decide to migrate to the EVP_CIPHER based APIs.

[camshaft]

I got through everything outside of cipher.rs and cipher/key.rs. I'll need to do the rest tomorrow.

[camshaft]

nit: it might be worth extracting some of this out into an actual function rather than a macro. It's especially annoying to work with paste! and other tooling like rustfmt or rust-analyzer.

[torben-hansen]

CI looks unhappy. But otherwise, OK from me.

[justsmth]

CI looks unhappy. But otherwise, OK from me.

CI is happy now.