key: add fingerprint to key config

and set/generate it on
- key creation
- key passphrase change
- key decryption if not already set
- key encryption with master key

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

src/backup/crypt_config.rs

@@ -17,6 +17,8 @@ use openssl::pkcs5::pbkdf2_hmac;
 use openssl::symm::{decrypt_aead, Cipher, Crypter, Mode};
 use serde::{Deserialize, Serialize};
 
+use crate::tools::format::{as_fingerprint, bytes_as_fingerprint};
+
 use proxmox::api::api;
 
 // openssl::sha::sha256(b"Proxmox Backup Encryption Key Fingerprint")
@@ -37,14 +39,18 @@ pub enum CryptMode {
     SignOnly,
 }
 
+#[derive(Debug, Eq, PartialEq, Deserialize, Serialize)]
+#[serde(transparent)]
 /// 32-byte fingerprint, usually calculated with SHA256.
 pub struct Fingerprint {
+    #[serde(with = "bytes_as_fingerprint")]
     bytes: [u8; 32],
 }
 
+/// Display as short key ID
 impl Display for Fingerprint {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}", self.bytes)
+        write!(f, "{}", as_fingerprint(&self.bytes[0..8]))
     }
 }
 
@@ -243,7 +249,13 @@ impl CryptConfig {
     ) -> Result<Vec<u8>, Error> {
 
         let modified = proxmox::tools::time::epoch_i64();
-        let key_config = super::KeyConfig { kdf: None, created, modified, data: self.enc_key.to_vec() };
+        let key_config = super::KeyConfig {
+            kdf: None,
+            created,
+            modified,
+            data: self.enc_key.to_vec(),
+            fingerprint: Some(self.fingerprint()),
+        };
         let data = serde_json::to_string(&key_config)?.as_bytes().to_vec();
 
         let mut buffer = vec![0u8; rsa.size() as usize];

src/backup/key_derivation.rs

@@ -2,6 +2,8 @@ use anyhow::{bail, format_err, Context, Error};
 
 use serde::{Deserialize, Serialize};
 
+use crate::backup::{CryptConfig, Fingerprint};
+
 use proxmox::tools::fs::{file_get_contents, replace_file, CreateOptions};
 use proxmox::try_block;
 
@@ -66,6 +68,9 @@ pub struct KeyConfig {
     pub modified: i64,
     #[serde(with = "proxmox::tools::serde::bytes_as_base64")]
     pub data: Vec<u8>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    #[serde(default)]
+    pub fingerprint: Option<Fingerprint>,
  }
 
 pub fn store_key_config(
@@ -142,13 +147,14 @@ pub fn encrypt_key_with_passphrase(
         created,
         modified: created,
         data: enc_data,
+        fingerprint: None,
     })
 }
 
 pub fn load_and_decrypt_key(
     path: &std::path::Path,
     passphrase: &dyn Fn() -> Result<Vec<u8>, Error>,
-) -> Result<([u8;32], i64), Error> {
+) -> Result<([u8;32], i64, Fingerprint), Error> {
     do_load_and_decrypt_key(path, passphrase)
         .with_context(|| format!("failed to load decryption key from {:?}", path))
 }
@@ -156,14 +162,14 @@ pub fn load_and_decrypt_key(
 fn do_load_and_decrypt_key(
     path: &std::path::Path,
     passphrase: &dyn Fn() -> Result<Vec<u8>, Error>,
-) -> Result<([u8;32], i64), Error> {
+) -> Result<([u8;32], i64, Fingerprint), Error> {
     decrypt_key(&file_get_contents(&path)?, passphrase)
 }
 
 pub fn decrypt_key(
     mut keydata: &[u8],
     passphrase: &dyn Fn() -> Result<Vec<u8>, Error>,
-) -> Result<([u8;32], i64), Error> {
+) -> Result<([u8;32], i64, Fingerprint), Error> {
     let key_config: KeyConfig = serde_json::from_reader(&mut keydata)?;
 
     let raw_data = key_config.data;
@@ -203,5 +209,13 @@ pub fn decrypt_key(
     let mut result = [0u8; 32];
     result.copy_from_slice(&key);
 
-    Ok((result, created))
+    let fingerprint = match key_config.fingerprint {
+        Some(fingerprint) => fingerprint,
+        None => {
+            let crypt_config = CryptConfig::new(result.clone())?;
+            crypt_config.fingerprint()
+        },
+    };
+
+    Ok((result, created, fingerprint))
 }

src/bin/proxmox-backup-client.rs

@@ -1069,7 +1069,7 @@ async fn create_backup(
     let (crypt_config, rsa_encrypted_key) = match keydata {
         None => (None, None),
         Some(key) => {
-            let (key, created) = decrypt_key(&key, &key::get_encryption_key_password)?;
+            let (key, created, _fingerprint) = decrypt_key(&key, &key::get_encryption_key_password)?;
 
             let crypt_config = CryptConfig::new(key)?;
 
@@ -1380,7 +1380,7 @@ async fn restore(param: Value) -> Result<Value, Error> {
     let crypt_config = match keydata {
         None => None,
         Some(key) => {
-            let (key, _) = decrypt_key(&key, &key::get_encryption_key_password)?;
+            let (key, _, _) = decrypt_key(&key, &key::get_encryption_key_password)?;
             Some(Arc::new(CryptConfig::new(key)?))
         }
     };
@@ -1538,7 +1538,7 @@ async fn upload_log(param: Value) -> Result<Value, Error> {
     let crypt_config = match keydata {
         None => None,
         Some(key) => {
-            let (key, _created) = decrypt_key(&key, &key::get_encryption_key_password)?;
+            let (key, _created, _) = decrypt_key(&key, &key::get_encryption_key_password)?;
             let crypt_config = CryptConfig::new(key)?;
             Some(Arc::new(crypt_config))
         }

src/bin/proxmox_backup_client/benchmark.rs

@@ -151,7 +151,7 @@ pub async fn benchmark(
     let crypt_config = match keyfile {
         None => None,
         Some(path) => {
-            let (key, _) = load_and_decrypt_key(&path, &crate::key::get_encryption_key_password)?;
+            let (key, _, _) = load_and_decrypt_key(&path, &crate::key::get_encryption_key_password)?;
             let crypt_config = CryptConfig::new(key)?;
             Some(Arc::new(crypt_config))
         }

src/bin/proxmox_backup_client/catalog.rs

@@ -73,7 +73,7 @@ async fn dump_catalog(param: Value) -> Result<Value, Error> {
     let crypt_config = match keydata {
         None => None,
         Some(key) => {
-            let (key, _created) = decrypt_key(&key, &get_encryption_key_password)?;
+            let (key, _created, _fingerprint) = decrypt_key(&key, &get_encryption_key_password)?;
             let crypt_config = CryptConfig::new(key)?;
             Some(Arc::new(crypt_config))
         }
@@ -170,7 +170,7 @@ async fn catalog_shell(param: Value) -> Result<(), Error> {
     let crypt_config = match keydata {
         None => None,
         Some(key) => {
-            let (key, _created) = decrypt_key(&key, &get_encryption_key_password)?;
+            let (key, _created, _fingerprint) = decrypt_key(&key, &get_encryption_key_password)?;
             let crypt_config = CryptConfig::new(key)?;
             Some(Arc::new(crypt_config))
         }

src/bin/proxmox_backup_client/key.rs

@@ -11,7 +11,11 @@ use proxmox::sys::linux::tty;
 use proxmox::tools::fs::{file_get_contents, replace_file, CreateOptions};
 
 use proxmox_backup::backup::{
-    encrypt_key_with_passphrase, load_and_decrypt_key, store_key_config, KeyConfig,
+    encrypt_key_with_passphrase,
+    load_and_decrypt_key,
+    store_key_config,
+    CryptConfig,
+    KeyConfig,
 };
 use proxmox_backup::tools;
 
@@ -120,7 +124,10 @@ fn create(kdf: Option<Kdf>, path: Option<String>) -> Result<(), Error> {
 
     let kdf = kdf.unwrap_or_default();
 
-    let key = proxmox::sys::linux::random_data(32)?;
+    let mut key_array = [0u8; 32];
+    proxmox::sys::linux::fill_with_random_data(&mut key_array)?;
+    let crypt_config = CryptConfig::new(key_array.clone())?;
+    let key = key_array.to_vec();
 
     match kdf {
         Kdf::None => {
@@ -134,6 +141,7 @@ fn create(kdf: Option<Kdf>, path: Option<String>) -> Result<(), Error> {
                     created,
                     modified: created,
                     data: key,
+                    fingerprint: Some(crypt_config.fingerprint()),
                 },
             )?;
         }
@@ -145,7 +153,8 @@ fn create(kdf: Option<Kdf>, path: Option<String>) -> Result<(), Error> {
 
             let password = tty::read_and_verify_password("Encryption Key Password: ")?;
 
-            let key_config = encrypt_key_with_passphrase(&key, &password)?;
+            let mut key_config = encrypt_key_with_passphrase(&key, &password)?;
+            key_config.fingerprint = Some(crypt_config.fingerprint());
 
             store_key_config(&path, false, key_config)?;
         }
@@ -188,7 +197,7 @@ fn change_passphrase(kdf: Option<Kdf>, path: Option<String>) -> Result<(), Error
         bail!("unable to change passphrase - no tty");
     }
 
-    let (key, created) = load_and_decrypt_key(&path, &get_encryption_key_password)?;
+    let (key, created, fingerprint) = load_and_decrypt_key(&path, &get_encryption_key_password)?;
 
     match kdf {
         Kdf::None => {
@@ -202,6 +211,7 @@ fn change_passphrase(kdf: Option<Kdf>, path: Option<String>) -> Result<(), Error
                     created, // keep original value
                     modified,
                     data: key.to_vec(),
+                    fingerprint: Some(fingerprint),
                 },
             )?;
         }
@@ -210,6 +220,7 @@ fn change_passphrase(kdf: Option<Kdf>, path: Option<String>) -> Result<(), Error
 
             let mut new_key_config = encrypt_key_with_passphrase(&key, &password)?;
             new_key_config.created = created; // keep original value
+            new_key_config.fingerprint = Some(fingerprint);
 
             store_key_config(&path, true, new_key_config)?;
         }

src/bin/proxmox_backup_client/mount.rs

@@ -182,7 +182,7 @@ async fn mount_do(param: Value, pipe: Option<RawFd>) -> Result<Value, Error> {
     let crypt_config = match keyfile {
         None => None,
         Some(path) => {
-            let (key, _) = load_and_decrypt_key(&path, &crate::key::get_encryption_key_password)?;
+            let (key, _, _) = load_and_decrypt_key(&path, &crate::key::get_encryption_key_password)?;
             Some(Arc::new(CryptConfig::new(key)?))
         }
     };

src/tools/format.rs

@@ -102,6 +102,40 @@ impl From<u64> for HumanByte {
     }
 }
 
+pub fn as_fingerprint(bytes: &[u8]) -> String {
+    proxmox::tools::digest_to_hex(bytes)
+        .as_bytes()
+        .chunks(2)
+        .map(|v| std::str::from_utf8(v).unwrap())
+        .collect::<Vec<&str>>().join(":")
+}
+
+pub mod bytes_as_fingerprint {
+    use serde::{Deserialize, Serializer, Deserializer};
+
+    pub fn serialize<S>(
+        bytes: &[u8; 32],
+        serializer: S,
+    ) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let s = crate::tools::format::as_fingerprint(bytes);
+        serializer.serialize_str(&s)
+    }
+
+    pub fn deserialize<'de, D>(
+        deserializer: D,
+    ) -> Result<[u8; 32], D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let mut s = String::deserialize(deserializer)?;
+        s.retain(|c| c != ':');
+        proxmox::tools::hex_to_digest(&s).map_err(serde::de::Error::custom)
+    }
+}
+
 #[test]
 fn correct_byte_convert() {
     fn convert(b: usize) -> String {