1 files changed, 95 insertions, 0 deletions

diff --git a/webd/src/config.rs b/webd/src/config.rs
new file mode 100644
index 0000000..d3ada8f
--- /dev/null
+++ b/webd/src/config.rs
@@ -0,0 +1,95 @@
+//! Gateway configuration from the environment.
+//!
+//! The upstream key is mandatory. There is no trust-on-first-use and no unsafe
+//! mode: the browser's credentials ride on this connection.
+
+use std::env;
+use std::time::Duration;
+
+pub const DEFAULT_BIND: &str = "127.0.0.1:8890";
+pub const DEFAULT_UPSTREAM: &str = "127.0.0.1:11525";
+pub const DEFAULT_GRACE_SECONDS: u64 = 60;
+pub const DEFAULT_ORIGIN: &str = "https://zagan.2137697.xyz";
+
+#[derive(Debug, Clone)]
+pub struct Config {
+    /// Loopback address nginx proxies `/ws` to.
+    pub bind: String,
+    /// Exact browser origin allowed on the WebSocket handshake.
+    pub origin: String,
+    /// Game server address, `host:port`.
+    pub upstream: String,
+    /// Lowercase hex SHA-256 of the upstream certificate's SPKI.
+    pub fingerprint: String,
+    /// How long a session survives without a browser socket.
+    pub grace: Duration,
+    /// `Secure` on the session cookie. Off only for local http testing.
+    pub cookie_secure: bool,
+}
+
+impl Config {
+    pub fn from_env() -> Result<Self, String> {
+        let bind = value("ZAGAN_WEB_BIND", DEFAULT_BIND);
+        let origin = value("ZAGAN_WEB_ORIGIN", DEFAULT_ORIGIN);
+        if !origin.starts_with("http://") && !origin.starts_with("https://") {
+            return Err("ZAGAN_WEB_ORIGIN must start with http:// or https://".to_string());
+        }
+        let origin = origin.trim_end_matches('/').to_string();
+
+        let upstream = value("ZAGAN_UPSTREAM", DEFAULT_UPSTREAM);
+        let fingerprint = required("ZAGAN_UPSTREAM_FINGERPRINT")?;
+        let fingerprint = fingerprint.trim().to_ascii_lowercase();
+        if fingerprint.len() != 64 || !fingerprint.bytes().all(|byte| byte.is_ascii_hexdigit()) {
+            return Err(
+                "ZAGAN_UPSTREAM_FINGERPRINT must be the 64-character SHA-256 of the upstream SPKI"
+                    .to_string(),
+            );
+        }
+
+        let grace_seconds = match env::var("ZAGAN_GRACE_SECONDS") {
+            Ok(raw) => raw
+                .trim()
+                .parse::<u64>()
+                .map_err(|_| "ZAGAN_GRACE_SECONDS must be a whole number of seconds".to_string())?,
+            Err(_) => DEFAULT_GRACE_SECONDS,
+        };
+
+        let cookie_secure = match env::var("ZAGAN_WEB_COOKIE_SECURE") {
+            Ok(raw) => matches!(
+                raw.trim().to_ascii_lowercase().as_str(),
+                "1" | "true" | "yes"
+            ),
+            Err(_) => origin.starts_with("https://"),
+        };
+
+        Ok(Self {
+            bind,
+            origin,
+            upstream,
+            fingerprint,
+            grace: Duration::from_secs(grace_seconds),
+            cookie_secure,
+        })
+    }
+}
+
+fn value(name: &str, default: &str) -> String {
+    env::var(name)
+        .ok()
+        .map(|value| value.trim().to_string())
+        .filter(|value| !value.is_empty())
+        .unwrap_or_else(|| default.to_string())
+}
+
+fn required(name: &str) -> Result<String, String> {
+    env::var(name)
+        .ok()
+        .map(|value| value.trim().to_string())
+        .filter(|value| !value.is_empty())
+        .ok_or_else(|| {
+            format!(
+                "{name} is required: the gateway pins the upstream key. \
+                 Use the SPKI fingerprint the desktop client shows."
+            )
+        })
+}