275 lines
7.9 KiB
Rust
275 lines
7.9 KiB
Rust
//! Wrappers for OpenSSL crypto functions
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//!
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//! We use this to encrypt and decryprt data chunks. Cipher is
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//! AES_256_GCM, which is fast and provides authenticated encryption.
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//!
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//! See the Wikipedia Artikel for [Authenticated
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//! encryption](https://en.wikipedia.org/wiki/Authenticated_encryption)
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//! for a short introduction.
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use std::fmt;
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use std::fmt::Display;
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use std::io::Write;
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use anyhow::{bail, Error};
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use openssl::hash::MessageDigest;
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use openssl::pkcs5::pbkdf2_hmac;
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use openssl::symm::{decrypt_aead, Cipher, Crypter, Mode};
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use serde::{Deserialize, Serialize};
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use crate::tools::format::{as_fingerprint, bytes_as_fingerprint};
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use proxmox::api::api;
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// openssl::sha::sha256(b"Proxmox Backup Encryption Key Fingerprint")
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const FINGERPRINT_INPUT: [u8; 32] = [ 110, 208, 239, 119, 71, 31, 255, 77,
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85, 199, 168, 254, 74, 157, 182, 33,
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97, 64, 127, 19, 76, 114, 93, 223,
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48, 153, 45, 37, 236, 69, 237, 38, ];
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#[api(default: "encrypt")]
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#[derive(Copy, Clone, Debug, Eq, PartialEq, Deserialize, Serialize)]
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#[serde(rename_all = "kebab-case")]
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/// Defines whether data is encrypted (using an AEAD cipher), only signed, or neither.
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pub enum CryptMode {
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/// Don't encrypt.
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None,
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/// Encrypt.
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Encrypt,
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/// Only sign.
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SignOnly,
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}
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#[derive(Debug, Eq, PartialEq, Deserialize, Serialize)]
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#[serde(transparent)]
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/// 32-byte fingerprint, usually calculated with SHA256.
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pub struct Fingerprint {
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#[serde(with = "bytes_as_fingerprint")]
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bytes: [u8; 32],
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}
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impl Fingerprint {
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pub fn bytes(&self) -> &[u8; 32] {
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&self.bytes
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}
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}
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/// Display as short key ID
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impl Display for Fingerprint {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(f, "{}", as_fingerprint(&self.bytes[0..8]))
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}
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}
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/// Encryption Configuration with secret key
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///
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/// This structure stores the secret key and provides helpers for
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/// authenticated encryption.
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pub struct CryptConfig {
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// the Cipher
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cipher: Cipher,
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// A secrect key use to provide the chunk digest name space.
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id_key: [u8; 32],
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// Openssl hmac PKey of id_key
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id_pkey: openssl::pkey::PKey<openssl::pkey::Private>,
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// The private key used by the cipher.
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enc_key: [u8; 32],
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}
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impl CryptConfig {
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/// Create a new instance.
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///
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/// We compute a derived 32 byte key using pbkdf2_hmac. This second
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/// key is used in compute_digest.
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pub fn new(enc_key: [u8; 32]) -> Result<Self, Error> {
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let mut id_key = [0u8; 32];
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pbkdf2_hmac(
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&enc_key,
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b"_id_key",
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10,
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MessageDigest::sha256(),
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&mut id_key)?;
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let id_pkey = openssl::pkey::PKey::hmac(&id_key).unwrap();
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Ok(Self { id_key, id_pkey, enc_key, cipher: Cipher::aes_256_gcm() })
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}
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/// Expose Cipher
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pub fn cipher(&self) -> &Cipher {
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&self.cipher
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}
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/// Compute a chunk digest using a secret name space.
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///
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/// Computes an SHA256 checksum over some secret data (derived
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/// from the secret key) and the provided data. This ensures that
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/// chunk digest values do not clash with values computed for
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/// other sectret keys.
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pub fn compute_digest(&self, data: &[u8]) -> [u8; 32] {
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let mut hasher = openssl::sha::Sha256::new();
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hasher.update(data);
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hasher.update(&self.id_key); // at the end, to avoid length extensions attacks
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hasher.finish()
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}
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pub fn data_signer(&self) -> openssl::sign::Signer {
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openssl::sign::Signer::new(MessageDigest::sha256(), &self.id_pkey).unwrap()
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}
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/// Compute authentication tag (hmac/sha256)
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///
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/// Computes an SHA256 HMAC using some secret data (derived
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/// from the secret key) and the provided data.
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pub fn compute_auth_tag(&self, data: &[u8]) -> [u8; 32] {
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let mut signer = self.data_signer();
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signer.update(data).unwrap();
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let mut tag = [0u8; 32];
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signer.sign(&mut tag).unwrap();
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tag
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}
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pub fn fingerprint(&self) -> Fingerprint {
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Fingerprint {
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bytes: self.compute_digest(&FINGERPRINT_INPUT)
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}
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}
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pub fn data_crypter(&self, iv: &[u8; 16], mode: Mode) -> Result<Crypter, Error> {
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let mut crypter = openssl::symm::Crypter::new(self.cipher, mode, &self.enc_key, Some(iv))?;
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crypter.aad_update(b"")?; //??
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Ok(crypter)
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}
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/// Encrypt data using a random 16 byte IV.
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///
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/// Writes encrypted data to ``output``, Return the used IV and computed MAC.
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pub fn encrypt_to<W: Write>(
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&self,
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data: &[u8],
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mut output: W,
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) -> Result<([u8;16], [u8;16]), Error> {
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let mut iv = [0u8; 16];
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proxmox::sys::linux::fill_with_random_data(&mut iv)?;
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let mut tag = [0u8; 16];
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let mut c = self.data_crypter(&iv, Mode::Encrypt)?;
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const BUFFER_SIZE: usize = 32*1024;
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let mut encr_buf = [0u8; BUFFER_SIZE];
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let max_encoder_input = BUFFER_SIZE - self.cipher.block_size();
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let mut start = 0;
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loop {
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let mut end = start + max_encoder_input;
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if end > data.len() { end = data.len(); }
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if end > start {
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let count = c.update(&data[start..end], &mut encr_buf)?;
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output.write_all(&encr_buf[..count])?;
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start = end;
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} else {
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break;
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}
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}
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let rest = c.finalize(&mut encr_buf)?;
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if rest > 0 { output.write_all(&encr_buf[..rest])?; }
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output.flush()?;
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c.get_tag(&mut tag)?;
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Ok((iv, tag))
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}
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/// Decompress and decrypt data, verify MAC.
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pub fn decode_compressed_chunk(
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&self,
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data: &[u8],
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iv: &[u8; 16],
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tag: &[u8; 16],
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) -> Result<Vec<u8>, Error> {
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let dec = Vec::with_capacity(1024*1024);
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let mut decompressor = zstd::stream::write::Decoder::new(dec)?;
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let mut c = self.data_crypter(iv, Mode::Decrypt)?;
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const BUFFER_SIZE: usize = 32*1024;
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let mut decr_buf = [0u8; BUFFER_SIZE];
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let max_decoder_input = BUFFER_SIZE - self.cipher.block_size();
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let mut start = 0;
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loop {
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let mut end = start + max_decoder_input;
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if end > data.len() { end = data.len(); }
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if end > start {
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let count = c.update(&data[start..end], &mut decr_buf)?;
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decompressor.write_all(&decr_buf[0..count])?;
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start = end;
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} else {
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break;
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}
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}
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c.set_tag(tag)?;
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let rest = c.finalize(&mut decr_buf)?;
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if rest > 0 { decompressor.write_all(&decr_buf[..rest])?; }
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decompressor.flush()?;
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Ok(decompressor.into_inner())
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}
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/// Decrypt data, verify tag.
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pub fn decode_uncompressed_chunk(
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&self,
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data: &[u8],
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iv: &[u8; 16],
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tag: &[u8; 16],
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) -> Result<Vec<u8>, Error> {
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let decr_data = decrypt_aead(
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self.cipher,
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&self.enc_key,
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Some(iv),
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b"", //??
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data,
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tag,
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)?;
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Ok(decr_data)
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}
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pub fn generate_rsa_encoded_key(
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&self,
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rsa: openssl::rsa::Rsa<openssl::pkey::Public>,
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created: i64,
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) -> Result<Vec<u8>, Error> {
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let modified = proxmox::tools::time::epoch_i64();
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let key_config = super::KeyConfig {
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kdf: None,
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created,
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modified,
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data: self.enc_key.to_vec(),
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fingerprint: Some(self.fingerprint()),
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};
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let data = serde_json::to_string(&key_config)?.as_bytes().to_vec();
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let mut buffer = vec![0u8; rsa.size() as usize];
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let len = rsa.public_encrypt(&data, &mut buffer, openssl::rsa::Padding::PKCS1)?;
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if len != buffer.len() {
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bail!("got unexpected length from rsa.public_encrypt().");
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}
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Ok(buffer)
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}
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}
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