moved key_derivation.rs from pbs_datastore to pbs-config/src/key_config.rs

Also moved pbs-datastore/src/crypt_config.rs to pbs-tools/src/crypt_config.rs.
We do not want to depend on pbs-api-types there, so I use [u8;32] instead of
Fingerprint.

pbs-tools/src/crypt_config.rs

@@ -0,0 +1,115 @@
+//! Wrappers for OpenSSL crypto functions
+//!
+//! We use this to encrypt and decrypt data chunks. Cipher is
+//! AES_256_GCM, which is fast and provides authenticated encryption.
+//!
+//! See the Wikipedia Artikel for [Authenticated
+//! encryption](https://en.wikipedia.org/wiki/Authenticated_encryption)
+//! for a short introduction.
+
+use anyhow::{Error};
+use openssl::hash::MessageDigest;
+use openssl::pkcs5::pbkdf2_hmac;
+use openssl::symm::{Cipher, Crypter, Mode};
+
+// openssl::sha::sha256(b"Proxmox Backup Encryption Key Fingerprint")
+/// This constant is used to compute fingerprints.
+const FINGERPRINT_INPUT: [u8; 32] = [
+    110, 208, 239, 119,  71,  31, 255,  77,
+    85, 199, 168, 254,  74, 157, 182,  33,
+    97,  64, 127,  19,  76, 114,  93, 223,
+    48, 153,  45,  37, 236,  69, 237,  38,
+];
+
+/// Encryption Configuration with secret key
+///
+/// This structure stores the secret key and provides helpers for
+/// authenticated encryption.
+pub struct CryptConfig {
+    // the Cipher
+    cipher: Cipher,
+    // A secrect key use to provide the chunk digest name space.
+    id_key: [u8; 32],
+    // Openssl hmac PKey of id_key
+    id_pkey: openssl::pkey::PKey<openssl::pkey::Private>,
+    // The private key used by the cipher.
+    enc_key: [u8; 32],
+}
+
+impl CryptConfig {
+
+    /// Create a new instance.
+    ///
+    /// We compute a derived 32 byte key using pbkdf2_hmac. This second
+    /// key is used in compute_digest.
+    pub fn new(enc_key: [u8; 32]) -> Result<Self, Error> {
+
+        let mut id_key = [0u8; 32];
+
+        pbkdf2_hmac(
+            &enc_key,
+            b"_id_key",
+            10,
+            MessageDigest::sha256(),
+            &mut id_key)?;
+
+        let id_pkey = openssl::pkey::PKey::hmac(&id_key).unwrap();
+
+        Ok(Self { id_key, id_pkey, enc_key, cipher: Cipher::aes_256_gcm() })
+    }
+
+    /// Expose Cipher (AES_256_GCM)
+    pub fn cipher(&self) -> &Cipher {
+        &self.cipher
+    }
+
+    /// Expose encryption key
+    pub fn enc_key(&self) -> &[u8; 32] {
+        &self.enc_key
+    }
+
+    /// Compute a chunk digest using a secret name space.
+    ///
+    /// Computes an SHA256 checksum over some secret data (derived
+    /// from the secret key) and the provided data. This ensures that
+    /// chunk digest values do not clash with values computed for
+    /// other sectret keys.
+    pub fn compute_digest(&self, data: &[u8]) -> [u8; 32] {
+        let mut hasher = openssl::sha::Sha256::new();
+        hasher.update(data);
+        hasher.update(&self.id_key); // at the end, to avoid length extensions attacks
+        hasher.finish()
+    }
+
+    /// Returns an openssl Signer using SHA256
+    pub fn data_signer(&self) -> openssl::sign::Signer {
+        openssl::sign::Signer::new(MessageDigest::sha256(), &self.id_pkey).unwrap()
+    }
+
+    /// Compute authentication tag (hmac/sha256)
+    ///
+    /// Computes an SHA256 HMAC using some secret data (derived
+    /// from the secret key) and the provided data.
+    pub fn compute_auth_tag(&self, data: &[u8]) -> [u8; 32] {
+        let mut signer = self.data_signer();
+        signer.update(data).unwrap();
+        let mut tag = [0u8; 32];
+        signer.sign(&mut tag).unwrap();
+        tag
+    }
+
+    /// Computes a fingerprint for the secret key.
+    ///
+    /// This computes a digest using the derived key (id_key) in order
+    /// to hinder brute force attacks.
+    pub fn fingerprint(&self) -> [u8; 32] {
+        self.compute_digest(&FINGERPRINT_INPUT)
+    }
+
+    /// Returns an openssl Crypter using AES_256_GCM,
+    pub fn data_crypter(&self, iv: &[u8; 16], mode: Mode) -> Result<Crypter, Error>  {
+        let mut crypter = openssl::symm::Crypter::new(self.cipher, mode, &self.enc_key, Some(iv))?;
+        crypter.aad_update(b"")?; //??
+        Ok(crypter)
+    }
+}

pbs-tools/src/lib.rs

@@ -6,6 +6,7 @@ pub mod broadcast_future;
 pub mod cert;
 pub mod cli;
 pub mod compression;
+pub mod crypt_config;
 pub mod format;
 pub mod fd;
 pub mod fs;