server: if authentication enabled, and no users, create one

If authentication is enabled and there are no users, create an admin
user with username "admin" and a random password.

Issue: #274

Cargo.toml

@@ -39,7 +39,7 @@ md5 = "0.7.0"
 mime_guess = "2.0.3"
 nom = "7.1.0"
 percent-encoding = "2.1.0"
-rand = "0.7.3"
+rand = "0.8.5"
 reqwest = { version = "0.11.18", default-features = false, features = ["json", "rustls-tls", "rustls-tls-webpki-roots", "rustls-tls-native-roots"] }
 rpassword = "4.0.5"
 rust-embed = { version = "6.3.0", features = ["compression", "debug-embed"] }

src/server/main.rs

@@ -119,7 +119,12 @@ pub async fn main(args: &clap::ArgMatches) -> Result<()> {
     let mut context = build_context(server_config.clone(), datastore).await?;
 
     if server_config.authentication_required && !context.config_repo.has_users()? {
-        warn!("Username/password authentication is required, but no users exist");
+        warn!("Username/password authentication is required, but no users exist, creating a user");
+        let (username, password) = create_admin_user(&context)?;
+        warn!(
+            "Created administrator username and password: username={}, password={}",
+            username, password
+        );
     }
 
     if let Some(filename) = config_filename {
@@ -263,6 +268,19 @@ fn is_authentication_required(config: &Config) -> bool {
     true
 }
 
+fn create_admin_user(context: &ServerContext) -> Result<(String, String)> {
+    use rand::Rng;
+    let rng = rand::thread_rng();
+    let username = "admin";
+    let password: String = rng
+        .sample_iter(&rand::distributions::Alphanumeric)
+        .take(12)
+        .map(char::from)
+        .collect();
+    context.config_repo.add_user(username, &password)?;
+    Ok((username.to_string(), password))
+}
+
 fn is_input_enabled(config: &Config) -> bool {
     config.args.contains_id("input.filename")
         || config.get_bool("input.enabled").unwrap_or(false)