add optional encryption to rsa_key.pem

src/auth.rs

@@ -69,14 +69,59 @@ pub async fn initialize_keys() -> Result<(), Error> {
         Err(e) => return Err(e.into()),
     };
 
-    let (priv_key, priv_key_buffer) = if let Some(priv_key_buffer) = priv_key_buffer {
+    let passphrase = CONFIG.rsa_key_passphrase();
-        (Rsa::private_key_from_pem(priv_key_buffer.to_vec().as_slice())?, priv_key_buffer.to_vec())
+
+    let (priv_key, priv_key_buffer) = if let Some(stored_buffer) = priv_key_buffer {
+        let mut passphrase_error: Option<Error> = None;
+        let mut key_is_unencrypted = true;
+
+        // The callback is only invoked if the key file is encrypted. For unencrypted keys it is never called.
+        let rsa = Rsa::private_key_from_pem_callback(stored_buffer.to_vec().as_slice(), |buf| {
+            key_is_unencrypted = false;
+            if passphrase.is_empty() {
+                // Only reached when key is encrypted. Return any error to abort the callback;
+                // the actual error message is stored in passphrase_error above.
+                passphrase_error = Some(Error::other(
+                    "Private RSA key is encrypted but RSA_KEY_PASSPHRASE is not configured",
+                ));
+                return Err(openssl::error::ErrorStack::get());
+            }
+            let bytes = passphrase.as_bytes();
+            buf[..bytes.len()].copy_from_slice(bytes);
+            Ok(bytes.len())
+        });
+
+        let rsa = match rsa {
+            Ok(r) => r,
+            Err(_) if passphrase_error.is_some() => return Err(passphrase_error.unwrap().into()),
+            Err(e) => return Err(e.into()),
+        };
+
+        if key_is_unencrypted && !passphrase.is_empty() {
+            warn!(
+                "RSA key passphrase is configured but the existing private key '{}' is not encrypted.",
+                CONFIG.private_rsa_key()
+            );
+        }
+
+        // EncodingKey requires an unencrypted PEM, so export the in-memory key regardless of how it was stored on disk.
+        let unencrypted_pem = rsa.private_key_to_pem()?;
+        (rsa, unencrypted_pem)
     } else {
         let rsa_key = Rsa::generate(2048)?;
-        let priv_key_buffer = rsa_key.private_key_to_pem()?;
+
-        operator.write(&rsa_key_filename, priv_key_buffer.clone()).await?;
+        // Store encrypted on disk if a passphrase is configured, otherwise store plaintext.
+        let stored_pem = if passphrase.is_empty() {
+            rsa_key.private_key_to_pem()?
+        } else {
+            use openssl::symm::Cipher;
+            rsa_key.private_key_to_pem_passphrase(Cipher::aes_256_cbc(), passphrase.as_bytes())?
+        };
+        operator.write(&rsa_key_filename, stored_pem).await?;
         info!("Private key '{}' created correctly", CONFIG.private_rsa_key());
-        (rsa_key, priv_key_buffer)
+
+        let unencrypted_pem = rsa_key.private_key_to_pem()?;
+        (rsa_key, unencrypted_pem)
     };
     let pub_key_buffer = priv_key.public_key_to_pem()?;
 

src/config.rs

@@ -520,6 +520,8 @@ make_config! {
         templates_folder:       String, false,  auto,   |c| format!("{}/templates", c.data_folder);
         /// Session JWT key
         rsa_key_filename:       String, false,  auto,   |c| format!("{}/rsa_key", c.data_folder);
+        /// RSA key passphrase |> Passphrase used to encrypt the private RSA key file on disk (leave empty for unencrypted)
+        rsa_key_passphrase:     String, false,  def,    String::new();
         /// Web vault folder
         web_vault_folder:       String, false,  def,    "web-vault/".to_string();
     },
@@ -959,6 +961,11 @@ fn validate_config(cfg: &ConfigItems, on_update: bool) -> Result<(), Error> {
         err!(format!("`DATABASE_MIN_CONNS` must be smaller than or equal to `DATABASE_MAX_CONNS`.",));
     }
 
+    // 1024 = OpenSSL's PEM_BUFSIZE, the size of the buffer passed to the passphrase callback
+    if cfg.rsa_key_passphrase.as_bytes().len() > 1024 {
+        err!("`RSA_KEY_PASSPHRASE` must not exceed 1024 bytes");
+    }
+
     if let Some(log_file) = &cfg.log_file {
         if std::fs::OpenOptions::new().append(true).create(true).open(log_file).is_err() {
             err!("Unable to write to log file", log_file);

src/main.rs

@@ -77,7 +77,7 @@ async fn main() -> Result<(), Error> {
 
     check_data_folder().await;
     auth::initialize_keys().await.unwrap_or_else(|e| {
-        error!("Error creating private key '{}'\n{e:?}\nExiting Vaultwarden!", CONFIG.private_rsa_key());
+        error!("Error creating or loading private key '{}'\n{e:?}\nExiting Vaultwarden!", CONFIG.private_rsa_key());
         exit(1);
     });
     check_web_vault();