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use aes::cipher::{block_padding::Pkcs7, BlockDecryptMut, BlockEncryptMut, KeyIvInit};
use aes::{Aes128, Aes192, Aes256};
use anyhow::{anyhow, bail, Result};
use cbc::{Decryptor, Encryptor};
use hmac::{Hmac, Mac};
use sha2::Sha256;
const IV_LEN: usize = 16;
const BLOCK_LEN: usize = 16;
const MAC_LEN: usize = 32;
const SALT_LEN: usize = 16;
const VERSION_LEN: usize = 1;
const MIN_LEN: usize = VERSION_LEN + 2 * BLOCK_LEN + MAC_LEN;
const ITERATIONS: u32 = 100_000;
type HmacSha256 = Hmac<Sha256>;
#[derive(Clone, Copy)]
pub enum Version {
V1,
V2,
V3,
V4,
}
struct VersionProperties {
version: Version,
version_byte: u8,
enc_key_len: usize,
mac_key_len: usize,
}
const VERSION_PROPS: [VersionProperties; 4] = [
VersionProperties {
version: Version::V1,
version_byte: 0x8a,
enc_key_len: 16,
mac_key_len: 16,
},
VersionProperties {
version: Version::V2,
version_byte: 0x8b,
enc_key_len: 16,
mac_key_len: 32,
},
VersionProperties {
version: Version::V3,
version_byte: 0x8c,
enc_key_len: 24,
mac_key_len: 32,
},
VersionProperties {
version: Version::V4,
version_byte: 0x8d,
enc_key_len: 32,
mac_key_len: 32,
},
];
pub fn create_secret_key(version: Version) -> Result<Vec<u8>> {
let props = &VERSION_PROPS[version as usize];
let key_len = props.enc_key_len + props.mac_key_len;
let mut key = vec![0u8; key_len];
getrandom::getrandom(&mut key)?;
Ok(key)
}
pub fn decrypt_with_key(key: &[u8], data: &[u8]) -> Result<Vec<u8>> {
let props = version_properties(data, false)?;
decrypt(key, data, props, false)
}
pub fn decrypt_with_password(password: &[u8], data: &[u8]) -> Result<Vec<u8>> {
let props = version_properties(data, true)?;
let (key, _) = derive_key(password, &data[VERSION_LEN..VERSION_LEN + SALT_LEN], props)?;
decrypt(&key, data, props, true)
}
pub fn encrypt_with_key(key: &[u8], data: &[u8], version: Version) -> Result<Vec<u8>> {
let props = &VERSION_PROPS[version as usize];
encrypt(key, &[], data, props)
}
pub fn encrypt_with_password(password: &[u8], data: &[u8], version: Version) -> Result<Vec<u8>> {
let props = &VERSION_PROPS[version as usize];
let (key, salt) = derive_key(password, &[], props)?;
encrypt(&key, &salt, data, props)
}
pub fn verify_with_key(key: &[u8], data: &[u8]) -> bool {
if let Ok(props) = version_properties(data, false) {
verify(key, data, props)
} else {
false
}
}
pub fn verify_with_password(password: &[u8], data: &[u8]) -> bool {
if let Ok(props) = version_properties(data, true) {
if let Ok((key, _)) =
derive_key(password, &data[VERSION_LEN..VERSION_LEN + SALT_LEN], props)
{
return verify(&key, data, props);
}
}
false
}
fn decrypt(key: &[u8], data: &[u8], props: &VersionProperties, with_salt: bool) -> Result<Vec<u8>> {
let (enc_key, mac_key) = split_key(key, props)?;
if !verify2(mac_key, data) {
bail!("signature could not be verified")
}
let iv_start_pos = if with_salt {
VERSION_LEN + SALT_LEN
} else {
VERSION_LEN
};
let ct_start_pos = iv_start_pos + IV_LEN;
let iv = &data[iv_start_pos..ct_start_pos];
let ct = &data[ct_start_pos..data.len() - MAC_LEN];
let res =
match props.version {
Version::V1 | Version::V2 => Decryptor::<Aes128>::new(enc_key.into(), iv.into())
.decrypt_padded_vec_mut::<Pkcs7>(ct),
Version::V3 => Decryptor::<Aes192>::new(enc_key.into(), iv.into())
.decrypt_padded_vec_mut::<Pkcs7>(ct),
Version::V4 => Decryptor::<Aes256>::new(enc_key.into(), iv.into())
.decrypt_padded_vec_mut::<Pkcs7>(ct),
};
Ok(res?)
}
fn encrypt(key: &[u8], salt: &[u8], data: &[u8], props: &VersionProperties) -> Result<Vec<u8>> {
let (enc_key, mac_key) = split_key(key, props)?;
let mut vec = vec![props.version_byte];
vec.extend_from_slice(salt);
let mut iv = [0u8; IV_LEN];
getrandom::getrandom(&mut iv)?;
vec.extend_from_slice(&iv[..]);
let mut ct = match props.version {
Version::V1 | Version::V2 => Encryptor::<Aes128>::new(enc_key.into(), &iv.into())
.encrypt_padded_vec_mut::<Pkcs7>(data),
Version::V3 => Encryptor::<Aes192>::new(enc_key.into(), &iv.into())
.encrypt_padded_vec_mut::<Pkcs7>(data),
Version::V4 => Encryptor::<Aes256>::new(enc_key.into(), &iv.into())
.encrypt_padded_vec_mut::<Pkcs7>(data),
};
vec.append(&mut ct);
let mut mac = HmacSha256::new_from_slice(mac_key).unwrap();
mac.update(&vec);
vec.extend_from_slice(mac.finalize().into_bytes().as_slice());
Ok(vec)
}
fn verify(key: &[u8], data: &[u8], props: &VersionProperties) -> bool {
if let Ok((_, mac_key)) = split_key(key, props) {
verify2(mac_key, data)
} else {
false
}
}
fn verify2(mac_key: &[u8], data: &[u8]) -> bool {
let pos = data.len() - MAC_LEN;
let mut mac = HmacSha256::new_from_slice(mac_key).unwrap();
mac.update(&data[..pos]);
mac.verify_slice(&data[pos..]).is_ok()
}
fn derive_key(
password: &[u8],
salt: &[u8],
props: &VersionProperties,
) -> Result<(Vec<u8>, Vec<u8>)> {
let key_len = props.enc_key_len + props.mac_key_len;
let mut key = vec![0u8; key_len];
let mut salt_vec = Vec::with_capacity(SALT_LEN);
if salt.is_empty() {
salt_vec.resize(SALT_LEN, 8u8);
getrandom::getrandom(&mut salt_vec)?;
} else {
salt_vec.extend_from_slice(salt);
}
pbkdf2::pbkdf2::<HmacSha256>(password, &salt_vec, ITERATIONS, &mut key);
Ok((key, salt_vec))
}
fn split_key<'a>(key: &'a [u8], props: &VersionProperties) -> Result<(&'a [u8], &'a [u8])> {
if key.len() == props.enc_key_len + props.mac_key_len {
Ok((&key[..props.enc_key_len], &key[props.enc_key_len..]))
} else {
Err(anyhow!("incorrect secret key size"))
}
}
fn version_properties(data: &[u8], with_salt: bool) -> Result<&VersionProperties> {
let min_len = if with_salt {
MIN_LEN + SALT_LEN
} else {
MIN_LEN
};
if data.len() < min_len {
bail!("not enough data");
}
for props in &VERSION_PROPS {
if props.version_byte == data[0] {
return Ok(props);
}
}
Err(anyhow!("unknown version"))
}