feat(ui): added daisy UI for beautification (#3)

Co-authored-by: Sharang Parnerkar <parnerkarsharang@gmail.com>
Reviewed-on: #3

src/infrastructure/auth.rs

@@ -16,28 +16,37 @@ use crate::infrastructure::{state::User, Error, UserStateInner};
 
 pub const LOGGED_IN_USER_SESS_KEY: &str = "logged-in-user";
 
-/// In-memory store for pending OAuth states and their associated redirect
-/// URLs. Keyed by the random state string. This avoids dependence on the
-/// session cookie surviving the Keycloak redirect round-trip (the `dx serve`
-/// proxy can drop `Set-Cookie` headers on 307 responses).
+/// Data stored alongside each pending OAuth state. Holds the optional
+/// post-login redirect URL and the PKCE code verifier needed for the
+/// token exchange.
+#[derive(Debug, Clone)]
+struct PendingOAuthEntry {
+    redirect_url: Option<String>,
+    code_verifier: String,
+}
+
+/// In-memory store for pending OAuth states. Keyed by the random state
+/// string. This avoids dependence on the session cookie surviving the
+/// Keycloak redirect round-trip (the `dx serve` proxy can drop
+/// `Set-Cookie` headers on 307 responses).
 #[derive(Debug, Clone, Default)]
-pub struct PendingOAuthStore(Arc<RwLock<HashMap<String, Option<String>>>>);
+pub struct PendingOAuthStore(Arc<RwLock<HashMap<String, PendingOAuthEntry>>>);
 
 impl PendingOAuthStore {
-    /// Insert a pending state with an optional post-login redirect URL.
-    fn insert(&self, state: String, redirect_url: Option<String>) {
+    /// Insert a pending state with an optional redirect URL and PKCE verifier.
+    fn insert(&self, state: String, entry: PendingOAuthEntry) {
         // RwLock::write only panics if the lock is poisoned, which
         // indicates a prior panic -- propagating is acceptable here.
         #[allow(clippy::expect_used)]
         self.0
             .write()
             .expect("pending oauth store lock poisoned")
-            .insert(state, redirect_url);
+            .insert(state, entry);
     }
 
-    /// Remove and return the redirect URL if the state was pending.
+    /// Remove and return the entry if the state was pending.
     /// Returns `None` if the state was never stored (CSRF failure).
-    fn take(&self, state: &str) -> Option<Option<String>> {
+    fn take(&self, state: &str) -> Option<PendingOAuthEntry> {
         #[allow(clippy::expect_used)]
         self.0
             .write()
@@ -122,6 +131,28 @@ fn generate_state() -> String {
     })
 }
 
+/// Generate a PKCE code verifier (43-128 char URL-safe random string).
+///
+/// Uses 32 random bytes encoded as base64url (no padding) to produce
+/// a 43-character verifier per RFC 7636.
+fn generate_code_verifier() -> String {
+    use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine};
+
+    let bytes: [u8; 32] = rand::rng().random();
+    URL_SAFE_NO_PAD.encode(bytes)
+}
+
+/// Derive the S256 code challenge from a code verifier per RFC 7636.
+///
+/// `code_challenge = BASE64URL(SHA256(code_verifier))`
+fn derive_code_challenge(verifier: &str) -> String {
+    use base64::{engine::general_purpose::URL_SAFE_NO_PAD, Engine};
+    use sha2::{Digest, Sha256};
+
+    let digest = Sha256::digest(verifier.as_bytes());
+    URL_SAFE_NO_PAD.encode(digest)
+}
+
 /// Redirect the user to Keycloak's authorization page.
 ///
 /// Generates a random CSRF state, stores it (along with the optional
@@ -142,9 +173,17 @@ pub async fn auth_login(
 ) -> Result<impl IntoResponse, Error> {
     let config = OAuthConfig::from_env()?;
     let state = generate_state();
+    let code_verifier = generate_code_verifier();
+    let code_challenge = derive_code_challenge(&code_verifier);
 
     let redirect_url = params.get("redirect_url").cloned();
-    pending.insert(state.clone(), redirect_url);
+    pending.insert(
+        state.clone(),
+        PendingOAuthEntry {
+            redirect_url,
+            code_verifier,
+        },
+    );
 
     let mut url = Url::parse(&config.auth_endpoint())
         .map_err(|e| Error::StateError(format!("invalid auth endpoint URL: {e}")))?;
@@ -154,7 +193,9 @@ pub async fn auth_login(
         .append_pair("redirect_uri", &config.redirect_uri)
         .append_pair("response_type", "code")
         .append_pair("scope", "openid profile email")
-        .append_pair("state", &state);
+        .append_pair("state", &state)
+        .append_pair("code_challenge", &code_challenge)
+        .append_pair("code_challenge_method", "S256");
 
     Ok(Redirect::temporary(url.as_str()))
 }
@@ -203,11 +244,11 @@ pub async fn auth_callback(
         .get("state")
         .ok_or_else(|| Error::StateError("missing state parameter".into()))?;
 
-    let redirect_url = pending
+    let entry = pending
         .take(returned_state)
         .ok_or_else(|| Error::StateError("unknown or expired oauth state".into()))?;
 
-    // --- Exchange code for tokens ---
+    // --- Exchange code for tokens (with PKCE code_verifier) ---
     let code = params
         .get("code")
         .ok_or_else(|| Error::StateError("missing code parameter".into()))?;
@@ -220,6 +261,7 @@ pub async fn auth_callback(
             ("client_id", &config.client_id),
             ("redirect_uri", &config.redirect_uri),
             ("code", code),
+            ("code_verifier", &entry.code_verifier),
         ])
         .send()
         .await
@@ -259,7 +301,8 @@ pub async fn auth_callback(
 
     set_login_session(session, user_state).await?;
 
-    let target = redirect_url
+    let target = entry
+        .redirect_url
         .filter(|u| !u.is_empty())
         .unwrap_or_else(|| "/".into());