Improve documentation.

cache.go

@@ -5,26 +5,41 @@ import (
 	"time"
 )
 
-// CacheItem represents an item in the cache
+// CacheItem represents an item stored in the cache with its associated metadata.
 type CacheItem struct {
-	Value     interface{}
+	// Value is the cached data of any type
+	Value interface{}
+
+	// ExpiresAt is the timestamp when this item should be considered expired
+	// and removed from the cache during cleanup operations
 	ExpiresAt time.Time
 }
 
-// Cache is a simple in-memory cache
+// Cache provides a thread-safe in-memory caching mechanism with expiration support.
+// It uses a read-write mutex to ensure safe concurrent access to the cached items.
 type Cache struct {
+	// items stores the cached data with string keys
 	items map[string]CacheItem
+
+	// mutex protects concurrent access to the items map
+	// Use RLock/RUnlock for reads and Lock/Unlock for writes
 	mutex sync.RWMutex
 }
 
-// NewCache creates a new Cache
+// NewCache creates a new empty cache instance.
+// The cache is immediately ready for use and is thread-safe.
 func NewCache() *Cache {
 	return &Cache{
 		items: make(map[string]CacheItem),
 	}
 }
 
-// Set adds an item to the cache
+// Set adds or updates an item in the cache with the specified expiration duration.
+// Parameters:
+//   - key: Unique identifier for the cached item
+//   - value: The data to cache (can be of any type)
+//   - expiration: How long the item should remain in the cache
+// Thread-safe: Uses write locking to ensure safe concurrent access.
 func (c *Cache) Set(key string, value interface{}, expiration time.Duration) {
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
@@ -34,7 +49,13 @@ func (c *Cache) Set(key string, value interface{}, expiration time.Duration) {
 	}
 }
 
-// Get retrieves an item from the cache
+// Get retrieves an item from the cache if it exists and hasn't expired.
+// Parameters:
+//   - key: The identifier of the item to retrieve
+// Returns:
+//   - value: The cached data (nil if not found or expired)
+//   - found: true if the item was found and is valid, false otherwise
+// Thread-safe: Uses read locking to ensure safe concurrent access.
 func (c *Cache) Get(key string) (interface{}, bool) {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
@@ -49,14 +70,19 @@ func (c *Cache) Get(key string) (interface{}, bool) {
 	return item.Value, true
 }
 
-// Delete removes an item from the cache
+// Delete removes an item from the cache if it exists.
+// If the item doesn't exist, this operation is a no-op.
+// Thread-safe: Uses write locking to ensure safe concurrent access.
 func (c *Cache) Delete(key string) {
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
 	delete(c.items, key)
 }
 
-// Cleanup removes expired items from the cache
+// Cleanup removes all expired items from the cache.
+// This should be called periodically to prevent memory leaks from
+// expired items that haven't been accessed (and thus not removed during Get operations).
+// Thread-safe: Uses write locking to ensure safe concurrent access.
 func (c *Cache) Cleanup() {
 	c.mutex.Lock()
 	defer c.mutex.Unlock()

helpers.go

@@ -16,6 +16,13 @@ import (
 	"github.com/gorilla/sessions"
 )
 
+// newSessionOptions creates secure session cookie options.
+// Parameters:
+//   - isSecure: Whether to set the Secure flag on cookies
+// Returns session options configured for security with:
+//   - HttpOnly flag to prevent JavaScript access
+//   - SameSite=Lax for CSRF protection
+//   - Appropriate timeout and path settings
 func newSessionOptions(isSecure bool) *sessions.Options {
 	return &sessions.Options{
 		HttpOnly: true,
@@ -26,7 +33,10 @@ func newSessionOptions(isSecure bool) *sessions.Options {
 	}
 }
 
-// generateNonce generates a random nonce
+// generateNonce creates a cryptographically secure random nonce
+// for use in the OIDC authentication flow. The nonce is used to
+// prevent replay attacks by ensuring the token received matches
+// the authentication request.
 func generateNonce() (string, error) {
 	nonceBytes := make([]byte, 32)
 	_, err := rand.Read(nonceBytes)
@@ -36,7 +46,33 @@ func generateNonce() (string, error) {
 	return base64.URLEncoding.EncodeToString(nonceBytes), nil
 }
 
-// exchangeTokens exchanges a code or refresh token for tokens
+// TokenResponse represents the response from the OIDC token endpoint.
+// It contains the various tokens and metadata returned after successful
+// code exchange or token refresh operations.
+type TokenResponse struct {
+	// IDToken is the OIDC ID token containing user claims
+	IDToken string `json:"id_token"`
+
+	// AccessToken is the OAuth 2.0 access token for API access
+	AccessToken string `json:"access_token"`
+
+	// RefreshToken is the OAuth 2.0 refresh token for obtaining new tokens
+	RefreshToken string `json:"refresh_token"`
+
+	// ExpiresIn is the lifetime in seconds of the access token
+	ExpiresIn int `json:"expires_in"`
+
+	// TokenType is the type of token, typically "Bearer"
+	TokenType string `json:"token_type"`
+}
+
+// exchangeTokens performs the OAuth 2.0 token exchange with the OIDC provider.
+// It supports both authorization code and refresh token grant types.
+// Parameters:
+//   - ctx: Context for the HTTP request
+//   - grantType: The OAuth 2.0 grant type ("authorization_code" or "refresh_token")
+//   - codeOrToken: Either the authorization code or refresh token
+//   - redirectURL: The callback URL for authorization code grant
 func (t *TraefikOidc) exchangeTokens(ctx context.Context, grantType, codeOrToken, redirectURL string) (*TokenResponse, error) {
 	data := url.Values{
 		"grant_type":    {grantType},
@@ -76,16 +112,8 @@ func (t *TraefikOidc) exchangeTokens(ctx context.Context, grantType, codeOrToken
 	return &tokenResponse, nil
 }
 
-// TokenResponse represents the response from the token endpoint
-type TokenResponse struct {
-	IDToken      string `json:"id_token"`
-	AccessToken  string `json:"access_token"`
-	RefreshToken string `json:"refresh_token"`
-	ExpiresIn    int    `json:"expires_in"`
-	TokenType    string `json:"token_type"`
-}
-
-// getNewTokenWithRefreshToken refreshes the token using the refresh token
+// getNewTokenWithRefreshToken obtains new tokens using a refresh token.
+// This is used to refresh access tokens before they expire.
 func (t *TraefikOidc) getNewTokenWithRefreshToken(refreshToken string) (*TokenResponse, error) {
 	ctx := context.Background()
 	tokenResponse, err := t.exchangeTokens(ctx, "refresh_token", refreshToken, "")
@@ -94,24 +122,23 @@ func (t *TraefikOidc) getNewTokenWithRefreshToken(refreshToken string) (*TokenRe
 	}
 
 	t.logger.Debugf("Token response: %+v", tokenResponse)
-
 	return tokenResponse, nil
 }
 
-// handleExpiredToken handles the case when a token has expired
+// handleExpiredToken manages token expiration by clearing the session
+// and initiating a new authentication flow.
 func (t *TraefikOidc) handleExpiredToken(rw http.ResponseWriter, req *http.Request, session *SessionData, redirectURL string) {
-	// Clear the existing session
 	if err := session.Clear(req, rw); err != nil {
 		t.logger.Errorf("Failed to clear session: %v", err)
 		http.Error(rw, "Internal Server Error", http.StatusInternalServerError)
 		return
 	}
-
-	// Initialize new authentication
 	t.defaultInitiateAuthentication(rw, req, session, redirectURL)
 }
 
-// handleCallback handles the callback from the OIDC provider
+// handleCallback processes the authentication callback from the OIDC provider.
+// It validates the callback parameters, exchanges the authorization code for
+// tokens, verifies the tokens, and establishes the user's session.
 func (t *TraefikOidc) handleCallback(rw http.ResponseWriter, req *http.Request, redirectURL string) {
 	session, err := t.sessionManager.GetSession(req)
 	if err != nil {
@@ -122,7 +149,7 @@ func (t *TraefikOidc) handleCallback(rw http.ResponseWriter, req *http.Request,
 
 	t.logger.Debugf("Handling callback, URL: %s", req.URL.String())
 
-	// Check for errors in the query parameters
+	// Check for errors in the callback
 	if req.URL.Query().Get("error") != "" {
 		errorDescription := req.URL.Query().Get("error_description")
 		t.logger.Errorf("Authentication error: %s - %s", req.URL.Query().Get("error"), errorDescription)
@@ -130,7 +157,7 @@ func (t *TraefikOidc) handleCallback(rw http.ResponseWriter, req *http.Request,
 		return
 	}
 
-	// Validate state parameter matches the session's CSRF token
+	// Validate CSRF state
 	state := req.URL.Query().Get("state")
 	if state == "" {
 		t.logger.Error("No state in callback")
@@ -166,7 +193,7 @@ func (t *TraefikOidc) handleCallback(rw http.ResponseWriter, req *http.Request,
 		return
 	}
 
-	// Verify and process tokens
+	// Verify tokens and claims
 	if err := t.verifyToken(tokenResponse.IDToken); err != nil {
 		t.logger.Errorf("Failed to verify id_token: %v", err)
 		http.Error(rw, "Authentication failed", http.StatusInternalServerError)
@@ -180,7 +207,7 @@ func (t *TraefikOidc) handleCallback(rw http.ResponseWriter, req *http.Request,
 		return
 	}
 
-	// Verify nonce
+	// Verify nonce to prevent replay attacks
 	nonceClaim, ok := claims["nonce"].(string)
 	if !ok || nonceClaim == "" {
 		t.logger.Error("Nonce claim missing in id_token")
@@ -201,7 +228,7 @@ func (t *TraefikOidc) handleCallback(rw http.ResponseWriter, req *http.Request,
 		return
 	}
 
-	// Process email
+	// Validate user's email domain
 	email, _ := claims["email"].(string)
 	if email == "" || !t.isAllowedDomain(email) {
 		t.logger.Errorf("Invalid or disallowed email: %s", email)
@@ -209,13 +236,12 @@ func (t *TraefikOidc) handleCallback(rw http.ResponseWriter, req *http.Request,
 		return
 	}
 
-	// Update session with new values
+	// Update session with authentication data
 	session.SetAuthenticated(true)
 	session.SetEmail(email)
 	session.SetAccessToken(tokenResponse.IDToken)
 	session.SetRefreshToken(tokenResponse.RefreshToken)
 
-	// Save session
 	if err := session.Save(req, rw); err != nil {
 		t.logger.Errorf("Failed to save session: %v", err)
 		http.Error(rw, "Failed to save session", http.StatusInternalServerError)
@@ -231,7 +257,8 @@ func (t *TraefikOidc) handleCallback(rw http.ResponseWriter, req *http.Request,
 	http.Redirect(rw, req, redirectPath, http.StatusFound)
 }
 
-// extractClaims extracts claims from a JWT token
+// extractClaims parses a JWT token and extracts its claims.
+// It handles base64url decoding and JSON parsing of the token payload.
 func extractClaims(tokenString string) (map[string]interface{}, error) {
 	parts := strings.Split(tokenString, ".")
 	if len(parts) != 3 {
@@ -251,27 +278,32 @@ func extractClaims(tokenString string) (map[string]interface{}, error) {
 	return claims, nil
 }
 
-// TokenBlacklist maintains a blacklist of tokens
+// TokenBlacklist maintains a thread-safe list of revoked tokens.
+// It stores tokens with their expiration times and automatically
+// removes expired entries during cleanup operations.
 type TokenBlacklist struct {
+	// blacklist maps token IDs to their expiration times
 	blacklist map[string]time.Time
-	mutex     sync.RWMutex
+
+	// mutex protects concurrent access to the blacklist
+	mutex sync.RWMutex
 }
 
-// NewTokenBlacklist creates a new TokenBlacklist
+// NewTokenBlacklist creates a new TokenBlacklist instance.
 func NewTokenBlacklist() *TokenBlacklist {
 	return &TokenBlacklist{
 		blacklist: make(map[string]time.Time),
 	}
 }
 
-// Add adds a token to the blacklist
+// Add adds a token to the blacklist with an expiration time.
 func (tb *TokenBlacklist) Add(tokenID string, expiration time.Time) {
 	tb.mutex.Lock()
 	defer tb.mutex.Unlock()
 	tb.blacklist[tokenID] = expiration
 }
 
-// IsBlacklisted checks if a token is blacklisted
+// IsBlacklisted checks if a token is in the blacklist and not expired.
 func (tb *TokenBlacklist) IsBlacklisted(tokenID string) bool {
 	tb.mutex.RLock()
 	defer tb.mutex.RUnlock()
@@ -279,7 +311,7 @@ func (tb *TokenBlacklist) IsBlacklisted(tokenID string) bool {
 	return exists && time.Now().Before(expiration)
 }
 
-// Cleanup removes expired tokens from the blacklist
+// Cleanup removes expired tokens from the blacklist.
 func (tb *TokenBlacklist) Cleanup() {
 	tb.mutex.Lock()
 	defer tb.mutex.Unlock()
@@ -291,25 +323,29 @@ func (tb *TokenBlacklist) Cleanup() {
 	}
 }
 
-// TokenCache caches tokens
+// TokenCache provides a caching mechanism for validated tokens.
+// It stores token claims to avoid repeated validation of the
+// same token, improving performance for frequently used tokens.
 type TokenCache struct {
+	// cache is the underlying cache implementation
 	cache *Cache
 }
 
-// NewTokenCache creates a new TokenCache
+// NewTokenCache creates a new TokenCache instance.
 func NewTokenCache() *TokenCache {
 	return &TokenCache{
 		cache: NewCache(),
 	}
 }
 
-// Set sets a token in the cache
+// Set stores a token's claims in the cache with an expiration time.
 func (tc *TokenCache) Set(token string, claims map[string]interface{}, expiration time.Duration) {
 	token = "t-" + token
 	tc.cache.Set(token, claims, expiration)
 }
 
-// Get retrieves a token from the cache
+// Get retrieves a token's claims from the cache.
+// Returns the claims and a boolean indicating if the token was found.
 func (tc *TokenCache) Get(token string) (map[string]interface{}, bool) {
 	token = "t-" + token
 	value, found := tc.cache.Get(token)
@@ -320,18 +356,18 @@ func (tc *TokenCache) Get(token string) (map[string]interface{}, bool) {
 	return claims, ok
 }
 
-// Delete removes a token from the cache
+// Delete removes a token from the cache.
 func (tc *TokenCache) Delete(token string) {
 	token = "t-" + token
 	tc.cache.Delete(token)
 }
 
-// Cleanup cleans up expired tokens from the cache
+// Cleanup removes expired tokens from the cache.
 func (tc *TokenCache) Cleanup() {
 	tc.cache.Cleanup()
 }
 
-// exchangeCodeForToken exchanges the authorization code for tokens
+// exchangeCodeForToken exchanges an authorization code for tokens.
 func (t *TraefikOidc) exchangeCodeForToken(code string, redirectURL string) (*TokenResponse, error) {
 	ctx := context.Background()
 	tokenResponse, err := t.exchangeTokens(ctx, "authorization_code", code, redirectURL)
@@ -341,7 +377,8 @@ func (t *TraefikOidc) exchangeCodeForToken(code string, redirectURL string) (*To
 	return tokenResponse, nil
 }
 
-// createStringMap creates a map from a slice of strings
+// createStringMap creates a map from a slice of strings.
+// Used for efficient lookups in allowed domains and roles.
 func createStringMap(keys []string) map[string]struct{} {
 	result := make(map[string]struct{})
 	for _, key := range keys {
@@ -350,7 +387,9 @@ func createStringMap(keys []string) map[string]struct{} {
 	return result
 }
 
-// handleLogout handles the logout request
+// handleLogout manages the OIDC logout process.
+// It clears the session and redirects either to the OIDC provider's
+// end session endpoint (if available) or to the configured post-logout URL.
 func (t *TraefikOidc) handleLogout(rw http.ResponseWriter, req *http.Request) {
 	session, err := t.sessionManager.GetSession(req)
 	if err != nil {
@@ -359,22 +398,18 @@ func (t *TraefikOidc) handleLogout(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	// Get the access token before clearing session
 	accessToken := session.GetAccessToken()
 
-	// Clear all session data
 	if err := session.Clear(req, rw); err != nil {
 		t.logger.Errorf("Error clearing session: %v", err)
 		http.Error(rw, "Session error", http.StatusInternalServerError)
 		return
 	}
 
-	// Get the base URL for redirects
 	host := t.determineHost(req)
 	scheme := t.determineScheme(req)
 	baseURL := fmt.Sprintf("%s://%s", scheme, host)
 
-	// Determine post logout redirect URI
 	postLogoutRedirectURI := t.postLogoutRedirectURI
 	if postLogoutRedirectURI == "" {
 		postLogoutRedirectURI = fmt.Sprintf("%s/", baseURL)
@@ -382,7 +417,6 @@ func (t *TraefikOidc) handleLogout(rw http.ResponseWriter, req *http.Request) {
 		postLogoutRedirectURI = fmt.Sprintf("%s%s", baseURL, postLogoutRedirectURI)
 	}
 
-	// If we have an end session endpoint and an access token, use OIDC end session
 	if t.endSessionURL != "" && accessToken != "" {
 		logoutURL, err := BuildLogoutURL(t.endSessionURL, accessToken, postLogoutRedirectURI)
 		if err != nil {
@@ -394,11 +428,14 @@ func (t *TraefikOidc) handleLogout(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	// Otherwise, redirect to post logout URI
 	http.Redirect(rw, req, postLogoutRedirectURI, http.StatusFound)
 }
 
-// BuildLogoutURL constructs the OIDC end session URL
+// BuildLogoutURL constructs the OIDC end session URL with appropriate parameters.
+// Parameters:
+//   - endSessionURL: The OIDC provider's end session endpoint
+//   - idToken: The ID token to be invalidated
+//   - postLogoutRedirectURI: Where to redirect after logout completes
 func BuildLogoutURL(endSessionURL, idToken, postLogoutRedirectURI string) (string, error) {
 	u, err := url.Parse(endSessionURL)
 	if err != nil {
@@ -408,7 +445,6 @@ func BuildLogoutURL(endSessionURL, idToken, postLogoutRedirectURI string) (strin
 	q := u.Query()
 	q.Set("id_token_hint", idToken)
 	if postLogoutRedirectURI != "" {
-		// Ensure postLogoutRedirectURI is properly URL encoded
 		q.Set("post_logout_redirect_uri", postLogoutRedirectURI)
 	}
 	u.RawQuery = q.Encode()

jwk.go

@@ -16,37 +16,74 @@ import (
 	"time"
 )
 
-// JWK represents a JSON Web Key
+// JWK represents a JSON Web Key as defined in RFC 7517.
+// It contains the cryptographic key information used for token verification.
 type JWK struct {
+	// Kty is the key type (e.g., "RSA", "EC")
 	Kty string `json:"kty"`
+
+	// Kid is the unique key identifier
 	Kid string `json:"kid"`
+
+	// Use specifies the intended use of the key (e.g., "sig" for signature)
 	Use string `json:"use"`
-	N   string `json:"n"`
-	E   string `json:"e"`
+
+	// N is the modulus for RSA keys
+	N string `json:"n"`
+
+	// E is the exponent for RSA keys
+	E string `json:"e"`
+
+	// Alg is the algorithm intended for use with the key
 	Alg string `json:"alg"`
+
+	// Crv is the curve for EC keys (e.g., "P-256", "P-384", "P-521")
 	Crv string `json:"crv"`
-	X   string `json:"x"`
-	Y   string `json:"y"`
+
+	// X is the x-coordinate for EC keys
+	X string `json:"x"`
+
+	// Y is the y-coordinate for EC keys
+	Y string `json:"y"`
 }
 
-// JWKSet represents a set of JWKs
+// JWKSet represents a set of JSON Web Keys as returned by the JWKS endpoint.
+// OIDC providers typically expose multiple keys to support key rotation.
 type JWKSet struct {
+	// Keys is the array of JSON Web Keys
 	Keys []JWK `json:"keys"`
 }
 
-// JWKCache caches the JWKs
+// JWKCache provides a thread-safe caching mechanism for JWK sets.
+// It caches the keys for a configurable duration to reduce load on the OIDC provider
+// while ensuring keys are refreshed periodically to handle key rotation.
 type JWKCache struct {
-	jwks      *JWKSet
+	// jwks holds the cached set of JSON Web Keys
+	jwks *JWKSet
+
+	// expiresAt is the timestamp when the cached keys should be refreshed
 	expiresAt time.Time
-	mutex     sync.RWMutex
+
+	// mutex protects concurrent access to the cache
+	mutex sync.RWMutex
 }
 
-// JWKCacheInterface defines the interface for the JWK cache
+// JWKCacheInterface defines the interface for JWK caching operations.
+// This interface allows for different caching implementations while
+// maintaining consistent behavior in the token verification process.
 type JWKCacheInterface interface {
 	GetJWKS(jwksURL string, httpClient *http.Client) (*JWKSet, error)
 }
 
-// GetJWKS gets the JWKS, either from cache or by fetching it
+// GetJWKS retrieves the JSON Web Key Set, either from cache or by fetching it
+// from the OIDC provider. It implements a thread-safe double-checked locking
+// pattern to prevent multiple simultaneous fetches of the same keys.
+// Parameters:
+//   - jwksURL: The URL of the JWKS endpoint
+//   - httpClient: The HTTP client to use for fetching keys
+// Returns:
+//   - The JSON Web Key Set
+//   - An error if the keys cannot be retrieved or parsed
 func (c *JWKCache) GetJWKS(jwksURL string, httpClient *http.Client) (*JWKSet, error) {
 	c.mutex.RLock()
 	if c.jwks != nil && time.Now().Before(c.expiresAt) {
@@ -73,7 +110,14 @@ func (c *JWKCache) GetJWKS(jwksURL string, httpClient *http.Client) (*JWKSet, er
 	return jwks, nil
 }
 
-// fetchJWKS fetches the JWKS from the provider
+// fetchJWKS retrieves the JSON Web Key Set from the OIDC provider's JWKS endpoint.
+// It handles HTTP communication and JSON parsing of the response.
+// Parameters:
+//   - jwksURL: The URL of the JWKS endpoint
+//   - httpClient: The HTTP client to use for the request
+// Returns:
+//   - The parsed JSON Web Key Set
+//   - An error if the request fails or the response is invalid
 func fetchJWKS(jwksURL string, httpClient *http.Client) (*JWKSet, error) {
 	resp, err := httpClient.Get(jwksURL)
 	if err != nil {
@@ -93,7 +137,9 @@ func fetchJWKS(jwksURL string, httpClient *http.Client) (*JWKSet, error) {
 	return &jwks, nil
 }
 
-// jwkToPEM converts a JWK to PEM format
+// jwkToPEM converts a JSON Web Key to PEM format for use with standard
+// cryptographic functions. It supports both RSA and EC keys, delegating
+// to the appropriate converter based on the key type.
 func jwkToPEM(jwk *JWK) ([]byte, error) {
 	converter, ok := jwkConverters[jwk.Kty]
 	if !ok {
@@ -109,7 +155,9 @@ var jwkConverters = map[string]jwkToPEMConverter{
 	"EC":  ecJWKToPEM,
 }
 
-// rsaJWKToPEM converts an RSA JWK to PEM
+// rsaJWKToPEM converts an RSA JSON Web Key to PEM format.
+// It handles base64url decoding of the modulus and exponent,
+// constructs an RSA public key, and encodes it in PEM format.
 func rsaJWKToPEM(jwk *JWK) ([]byte, error) {
 	nBytes, err := base64.RawURLEncoding.DecodeString(jwk.N)
 	if err != nil {
@@ -141,7 +189,10 @@ func rsaJWKToPEM(jwk *JWK) ([]byte, error) {
 	return pubKeyPEM, nil
 }
 
-// ecJWKToPEM converts an EC JWK to PEM
+// ecJWKToPEM converts an EC (Elliptic Curve) JSON Web Key to PEM format.
+// It supports the P-256, P-384, and P-521 curves as defined in the
+// OIDC specification, decoding the x and y coordinates and encoding
+// the resulting public key in PEM format.
 func ecJWKToPEM(jwk *JWK) ([]byte, error) {
 	xBytes, err := base64.RawURLEncoding.DecodeString(jwk.X)
 	if err != nil {

jwt.go

@@ -16,15 +16,31 @@ import (
 	"time"
 )
 
-// JWT represents a JSON Web Token
+// JWT represents a JSON Web Token as defined in RFC 7519.
+// It contains the three parts of a JWT: header, claims (payload),
+// and signature, along with the original token string.
 type JWT struct {
-	Header    map[string]interface{}
-	Claims    map[string]interface{}
+	// Header contains the token metadata (algorithm, key ID, etc.)
+	Header map[string]interface{}
+
+	// Claims contains the token claims (subject, expiration, etc.)
+	Claims map[string]interface{}
+
+	// Signature contains the raw signature bytes
 	Signature []byte
-	Token     string
+
+	// Token is the original JWT string
+	Token string
 }
 
-// parseJWT parses a JWT token string into a JWT struct
+// parseJWT parses a JWT token string into a JWT struct.
+// It validates the token format and decodes the three parts
+// (header, claims, signature) using base64url decoding.
+// Parameters:
+//   - tokenString: The raw JWT token string
+// Returns:
+//   - A parsed JWT struct
+//   - An error if the token format is invalid or parsing fails
 func parseJWT(tokenString string) (*JWT, error) {
 	parts := strings.Split(tokenString, ".")
 	if len(parts) != 3 {
@@ -63,7 +79,14 @@ func parseJWT(tokenString string) (*JWT, error) {
 	return jwt, nil
 }
 
-// Verify verifies the standard claims in the JWT
+// Verify validates the standard JWT claims as defined in RFC 7519.
+// It checks:
+//   - issuer (iss) matches the expected issuer URL
+//   - audience (aud) includes the client ID
+//   - expiration time (exp) is in the future
+//   - issued at time (iat) is in the past
+//   - subject (sub) is present and not empty
+// Returns an error if any validation fails.
 func (j *JWT) Verify(issuerURL, clientID string) error {
 	claims := j.Claims
 
@@ -107,7 +130,13 @@ func (j *JWT) Verify(issuerURL, clientID string) error {
 	return nil
 }
 
-// verifyAudience verifies the audience claim
+// verifyAudience validates the token's audience claim.
+// The audience can be either a single string or an array of strings.
+// For array audiences, the expected audience must match any one value.
+// Parameters:
+//   - tokenAudience: The audience claim from the token
+//   - expectedAudience: The expected audience value
+// Returns an error if validation fails.
 func verifyAudience(tokenAudience interface{}, expectedAudience string) error {
 	switch aud := tokenAudience.(type) {
 	case string:
@@ -131,7 +160,12 @@ func verifyAudience(tokenAudience interface{}, expectedAudience string) error {
 	return nil
 }
 
-// verifyIssuer verifies the issuer claim
+// verifyIssuer validates the token's issuer claim.
+// The issuer URL must exactly match the expected issuer.
+// Parameters:
+//   - tokenIssuer: The issuer claim from the token
+//   - expectedIssuer: The expected issuer URL
+// Returns an error if validation fails.
 func verifyIssuer(tokenIssuer, expectedIssuer string) error {
 	if tokenIssuer != expectedIssuer {
 		return fmt.Errorf("invalid issuer")
@@ -139,7 +173,11 @@ func verifyIssuer(tokenIssuer, expectedIssuer string) error {
 	return nil
 }
 
-// verifyExpiration checks if the token has expired
+// verifyExpiration checks if the token's expiration time has passed.
+// The expiration time is compared against the current time.
+// Parameters:
+//   - expiration: The expiration timestamp from the token
+// Returns an error if the token has expired.
 func verifyExpiration(expiration float64) error {
 	expirationTime := time.Unix(int64(expiration), 0)
 	if time.Now().After(expirationTime) {
@@ -148,7 +186,12 @@ func verifyExpiration(expiration float64) error {
 	return nil
 }
 
-// verifyIssuedAt checks if the token was issued in the future
+// verifyIssuedAt validates the token's issued-at time.
+// Ensures the token wasn't issued in the future, which could
+// indicate clock skew or a malicious token.
+// Parameters:
+//   - issuedAt: The issued-at timestamp from the token
+// Returns an error if the token was issued in the future.
 func verifyIssuedAt(issuedAt float64) error {
 	issuedAtTime := time.Unix(int64(issuedAt), 0)
 	if time.Now().Before(issuedAtTime) {
@@ -157,7 +200,16 @@ func verifyIssuedAt(issuedAt float64) error {
 	return nil
 }
 
-// verifySignature verifies the token signature using the provided public key and algorithm
+// verifySignature validates the token's cryptographic signature.
+// Supports multiple signature algorithms:
+//   - RSA: RS256, RS384, RS512 (PKCS#1 v1.5)
+//   - RSA-PSS: PS256, PS384, PS512
+//   - ECDSA: ES256, ES384, ES512
+// Parameters:
+//   - tokenString: The complete JWT token string
+//   - publicKeyPEM: The PEM-encoded public key for verification
+//   - alg: The signature algorithm identifier
+// Returns an error if signature verification fails.
 func verifySignature(tokenString string, publicKeyPEM []byte, alg string) error {
 	// Split the token into its three parts
 	parts := strings.Split(tokenString, ".")

session.go

@@ -8,34 +8,54 @@ import (
 	"github.com/gorilla/sessions"
 )
 
+// Cookie names and configuration constants used for session management
 const (
-	mainCookieName     = "_raczylo_oidc"         // Main session cookie
-	accessTokenCookie  = "_raczylo_oidc_access"  // Access token cookie
-	refreshTokenCookie = "_raczylo_oidc_refresh" // Refresh token cookie
-	maxCookieSize      = 2000                    // Max size for each chunk to stay within 4096-byte cookie limit
+	// mainCookieName is the name of the main session cookie that stores authentication state
+	// and basic user information like email and CSRF tokens
+	mainCookieName = "_raczylo_oidc"
 
-	// REASON:
-	// Let x be the maximum size of the chunk (maxCookieSize).
-	// Encrypted size = x + 28 bytes
-	// Base64-encoded size = ((x + 28) * 4) / 3 bytes
-	// ((x + 28) * 4) / 3 <= 4096
-	// Multiply both sides by 3:
-	// 4 * (x + 28) <= 4096 * 3
-	// 4 * (x + 28) <= 12288
-	// Divide both sides by 4:
-	// x + 28 <= 3072
-	// Subtract 28 from both sides:
-	// x <= 3044
+	// accessTokenCookie is the name of the cookie that stores the OIDC access token
+	// This may be split into multiple cookies if the token is large
+	accessTokenCookie = "_raczylo_oidc_access"
+
+	// refreshTokenCookie is the name of the cookie that stores the OIDC refresh token
+	// This may be split into multiple cookies if the token is large
+	refreshTokenCookie = "_raczylo_oidc_refresh"
+
+	// maxCookieSize is the maximum size for each cookie chunk.
+	// This value is calculated to ensure the final cookie size stays within browser limits:
+	// 1. Browser cookie size limit is typically 4096 bytes
+	// 2. Cookie content undergoes encryption (adds 28 bytes) and base64 encoding (4/3 ratio)
+	// 3. Calculation:
+	//    - Let x be the chunk size
+	//    - After encryption: x + 28 bytes
+	//    - After base64: ((x + 28) * 4/3) bytes
+	//    - Must satisfy: ((x + 28) * 4/3) ≤ 4096
+	//    - Solving for x: x ≤ 3044
+	// 4. We use 2000 as a conservative limit to account for cookie metadata
+	maxCookieSize = 2000
 )
 
-// SessionManager handles multiple session cookies
+// SessionManager handles the management of multiple session cookies for OIDC authentication.
+// It provides functionality for storing and retrieving authentication state, tokens,
+// and other session-related data across multiple cookies to handle large tokens.
 type SessionManager struct {
-	store      sessions.Store
+	// store is the underlying session store for cookie management
+	store sessions.Store
+
+	// forceHTTPS enforces secure cookie attributes regardless of request scheme
 	forceHTTPS bool
-	logger     *Logger
+
+	// logger provides structured logging capabilities
+	logger *Logger
 }
 
-// NewSessionManager creates a new session manager
+// NewSessionManager creates a new session manager with the specified configuration.
+// Parameters:
+//   - encryptionKey: Key used to encrypt session data (must be at least 32 bytes)
+//   - forceHTTPS: When true, forces secure cookie attributes regardless of request scheme
+//   - logger: Logger instance for recording session-related events
+// The manager handles session creation, storage, and cookie security settings.
 func NewSessionManager(encryptionKey string, forceHTTPS bool, logger *Logger) *SessionManager {
 	return &SessionManager{
 		store:      sessions.NewCookieStore([]byte(encryptionKey)),
@@ -44,7 +64,14 @@ func NewSessionManager(encryptionKey string, forceHTTPS bool, logger *Logger) *S
 	}
 }
 
-// getSessionOptions returns session options based on scheme
+// getSessionOptions returns secure session options configured for the current request.
+// Parameters:
+//   - isSecure: Whether the current request is using HTTPS
+// The options ensure cookies are:
+//   - HTTP-only (not accessible via JavaScript)
+//   - Secure when using HTTPS or when forceHTTPS is enabled
+//   - Using SameSite=Lax for CSRF protection
+//   - Set with appropriate timeout and path settings
 func (sm *SessionManager) getSessionOptions(isSecure bool) *sessions.Options {
 	return &sessions.Options{
 		HttpOnly: true,
@@ -55,7 +82,10 @@ func (sm *SessionManager) getSessionOptions(isSecure bool) *sessions.Options {
 	}
 }
 
-// GetSession retrieves all session data
+// GetSession retrieves all session data for the current request.
+// It loads the main session and token sessions, including any chunked token data,
+// and combines them into a single SessionData structure for easy access.
+// Returns an error if any session component cannot be loaded.
 func (sm *SessionManager) GetSession(r *http.Request) (*SessionData, error) {
 	mainSession, err := sm.store.Get(r, mainCookieName)
 	if err != nil {
@@ -88,7 +118,12 @@ func (sm *SessionManager) GetSession(r *http.Request) (*SessionData, error) {
 	return sessionData, nil
 }
 
-// getTokenChunkSessions retrieves sessions for token chunks
+// getTokenChunkSessions retrieves all session chunks for a given token type.
+// Parameters:
+//   - r: The HTTP request
+//   - baseName: The base name for the token's session cookies
+// Returns a map of chunk index to session, used for handling large tokens
+// that exceed single cookie size limits.
 func (sm *SessionManager) getTokenChunkSessions(r *http.Request, baseName string) map[int]*sessions.Session {
 	chunks := make(map[int]*sessions.Session)
 	for i := 0; ; i++ {
@@ -103,18 +138,39 @@ func (sm *SessionManager) getTokenChunkSessions(r *http.Request, baseName string
 	return chunks
 }
 
-// SessionData holds all session information
+// SessionData holds all session information for an authenticated user.
+// It manages multiple session cookies to handle the main session state
+// and potentially large access and refresh tokens that may need to be
+// split across multiple cookies due to browser size limitations.
 type SessionData struct {
-	manager            *SessionManager
-	request            *http.Request
-	mainSession        *sessions.Session
-	accessSession      *sessions.Session
-	refreshSession     *sessions.Session
-	accessTokenChunks  map[int]*sessions.Session
+	// manager is the SessionManager that created this SessionData
+	manager *SessionManager
+
+	// request is the current HTTP request associated with this session
+	request *http.Request
+
+	// mainSession stores authentication state and basic user info
+	mainSession *sessions.Session
+
+	// accessSession stores the primary access token cookie
+	accessSession *sessions.Session
+
+	// refreshSession stores the primary refresh token cookie
+	refreshSession *sessions.Session
+
+	// accessTokenChunks stores additional chunks of the access token
+	// when it exceeds the maximum cookie size
+	accessTokenChunks map[int]*sessions.Session
+
+	// refreshTokenChunks stores additional chunks of the refresh token
+	// when it exceeds the maximum cookie size
 	refreshTokenChunks map[int]*sessions.Session
 }
 
-// Save saves all session data
+// Save persists all session data to cookies in the HTTP response.
+// It saves the main session, token sessions, and any token chunks,
+// applying appropriate security options to each cookie. All cookies
+// are saved with consistent security settings based on the request scheme.
 func (sd *SessionData) Save(r *http.Request, w http.ResponseWriter) error {
 	isSecure := strings.HasPrefix(r.URL.Scheme, "https") || sd.manager.forceHTTPS
 
@@ -158,7 +214,9 @@ func (sd *SessionData) Save(r *http.Request, w http.ResponseWriter) error {
 	return nil
 }
 
-// Clear clears all session data
+// Clear removes all session data by expiring all cookies and clearing their values.
+// This is typically used during logout to ensure all session data is properly cleaned up.
+// It handles both main session data and any token chunks that may exist.
 func (sd *SessionData) Clear(r *http.Request, w http.ResponseWriter) error {
 	// Clear and expire all sessions
 	sd.mainSession.Options.MaxAge = -1
@@ -182,7 +240,9 @@ func (sd *SessionData) Clear(r *http.Request, w http.ResponseWriter) error {
 	return sd.Save(r, w)
 }
 
-// clearTokenChunks clears chunked token sessions
+// clearTokenChunks removes all session chunks for a given token type.
+// It expires the cookies and removes all stored values to ensure
+// no token data remains after logout or token invalidation.
 func (sd *SessionData) clearTokenChunks(r *http.Request, chunks map[int]*sessions.Session) {
 	for _, session := range chunks {
 		session.Options.MaxAge = -1
@@ -192,18 +252,24 @@ func (sd *SessionData) clearTokenChunks(r *http.Request, chunks map[int]*session
 	}
 }
 
-// GetAuthenticated returns authentication status
+// GetAuthenticated returns whether the current session is authenticated.
+// Returns true if the user has successfully completed OIDC authentication,
+// false otherwise or if the authentication status cannot be determined.
 func (sd *SessionData) GetAuthenticated() bool {
 	auth, _ := sd.mainSession.Values["authenticated"].(bool)
 	return auth
 }
 
-// SetAuthenticated sets authentication status
+// SetAuthenticated updates the session's authentication status.
+// This should be called after successful OIDC authentication or during logout.
 func (sd *SessionData) SetAuthenticated(value bool) {
 	sd.mainSession.Values["authenticated"] = value
 }
 
-// GetAccessToken returns the access token
+// GetAccessToken retrieves the complete access token from the session.
+// If the token was split into chunks due to size limitations, it will
+// automatically reassemble the complete token from all chunks.
+// Returns an empty string if no token is found.
 func (sd *SessionData) GetAccessToken() string {
 	token, _ := sd.accessSession.Values["token"].(string)
 	if token != "" {
@@ -228,7 +294,11 @@ func (sd *SessionData) GetAccessToken() string {
 	return strings.Join(chunks, "")
 }
 
-// SetAccessToken sets the access token
+// SetAccessToken stores the access token in the session.
+// If the token exceeds maxCookieSize, it is automatically split into
+// multiple cookie chunks to handle large tokens while staying within
+// browser cookie size limits. Any existing token or chunks are cleared
+// before setting the new token.
 func (sd *SessionData) SetAccessToken(token string) {
 	// Clear existing chunks
 	sd.clearTokenChunks(sd.request, sd.accessTokenChunks)
@@ -249,7 +319,10 @@ func (sd *SessionData) SetAccessToken(token string) {
 	}
 }
 
-// GetRefreshToken returns the refresh token
+// GetRefreshToken retrieves the complete refresh token from the session.
+// If the token was split into chunks due to size limitations, it will
+// automatically reassemble the complete token from all chunks.
+// Returns an empty string if no token is found.
 func (sd *SessionData) GetRefreshToken() string {
 	token, _ := sd.refreshSession.Values["token"].(string)
 	if token != "" {
@@ -274,7 +347,11 @@ func (sd *SessionData) GetRefreshToken() string {
 	return strings.Join(chunks, "")
 }
 
-// SetRefreshToken sets the refresh token
+// SetRefreshToken stores the refresh token in the session.
+// If the token exceeds maxCookieSize, it is automatically split into
+// multiple cookie chunks to handle large tokens while staying within
+// browser cookie size limits. Any existing token or chunks are cleared
+// before setting the new token.
 func (sd *SessionData) SetRefreshToken(token string) {
 	// Clear existing chunks
 	sd.clearTokenChunks(sd.request, sd.refreshTokenChunks)
@@ -295,7 +372,12 @@ func (sd *SessionData) SetRefreshToken(token string) {
 	}
 }
 
-// splitIntoChunks splits a string into chunks of specified size
+// splitIntoChunks splits a string into chunks of specified size.
+// This is used internally to handle large tokens that exceed cookie size limits.
+// Parameters:
+//   - s: The string to split
+//   - chunkSize: Maximum size of each chunk
+// Returns an array of string chunks, each no larger than chunkSize.
 func splitIntoChunks(s string, chunkSize int) []string {
 	var chunks []string
 	for len(s) > 0 {
@@ -310,46 +392,65 @@ func splitIntoChunks(s string, chunkSize int) []string {
 	return chunks
 }
 
-// GetCSRF returns the CSRF token
+// GetCSRF retrieves the CSRF token from the session.
+// This token is used to prevent cross-site request forgery attacks
+// by ensuring requests originate from the authenticated user.
+// Returns an empty string if no CSRF token is found.
 func (sd *SessionData) GetCSRF() string {
 	csrf, _ := sd.mainSession.Values["csrf"].(string)
 	return csrf
 }
 
-// SetCSRF sets the CSRF token
+// SetCSRF stores a new CSRF token in the session.
+// This should be called when initiating authentication to generate
+// a new token for the authentication flow.
 func (sd *SessionData) SetCSRF(token string) {
 	sd.mainSession.Values["csrf"] = token
 }
 
-// GetNonce returns the nonce
+// GetNonce retrieves the nonce value from the session.
+// The nonce is used to prevent replay attacks in the OIDC flow
+// by ensuring the token received matches the authentication request.
+// Returns an empty string if no nonce is found.
 func (sd *SessionData) GetNonce() string {
 	nonce, _ := sd.mainSession.Values["nonce"].(string)
 	return nonce
 }
 
-// SetNonce sets the nonce
+// SetNonce stores a new nonce value in the session.
+// This should be called when initiating authentication to generate
+// a new nonce for the OIDC authentication flow.
 func (sd *SessionData) SetNonce(nonce string) {
 	sd.mainSession.Values["nonce"] = nonce
 }
 
-// GetEmail returns the user's email
+// GetEmail retrieves the authenticated user's email address from the session.
+// The email is typically extracted from the OIDC ID token claims.
+// Returns an empty string if no email is found.
 func (sd *SessionData) GetEmail() string {
 	email, _ := sd.mainSession.Values["email"].(string)
 	return email
 }
 
-// SetEmail sets the user's email
+// SetEmail stores the user's email address in the session.
+// This should be called after successful authentication when
+// processing the OIDC ID token claims.
 func (sd *SessionData) SetEmail(email string) {
 	sd.mainSession.Values["email"] = email
 }
 
-// GetIncomingPath returns the original incoming path
+// GetIncomingPath retrieves the original request path that triggered
+// the authentication flow. This is used to redirect the user back
+// to their intended destination after successful authentication.
+// Returns an empty string if no path was stored.
 func (sd *SessionData) GetIncomingPath() string {
 	path, _ := sd.mainSession.Values["incoming_path"].(string)
 	return path
 }
 
-// SetIncomingPath sets the original incoming path
+// SetIncomingPath stores the original request path that triggered
+// the authentication flow. This should be called before redirecting
+// to the OIDC provider to remember where to send the user afterward.
 func (sd *SessionData) SetIncomingPath(path string) {
 	sd.mainSession.Values["incoming_path"] = path
 }

settings.go

@@ -5,35 +5,93 @@ import (
 	"io"
 	"log"
 	"net/http"
+	"net/url"
 	"os"
+	"strings"
 )
 
 const (
 	cookieName = "_raczylo_oidc"
 )
 
-// Config holds the configuration for the OIDC middleware
+// Config holds the configuration for the OIDC middleware.
+// It provides all necessary settings to configure OpenID Connect authentication
+// with various providers like Auth0, Logto, or any standard OIDC provider.
 type Config struct {
-	ProviderURL           string   `json:"providerURL"`
-	RevocationURL         string   `json:"revocationURL"`
-	CallbackURL           string   `json:"callbackURL"`
-	LogoutURL             string   `json:"logoutURL"`
-	ClientID              string   `json:"clientID"`
-	ClientSecret          string   `json:"clientSecret"`
-	Scopes                []string `json:"scopes"`
-	LogLevel              string   `json:"logLevel"`
-	SessionEncryptionKey  string   `json:"sessionEncryptionKey"`
-	ForceHTTPS            bool     `json:"forceHTTPS"`
-	RateLimit             int      `json:"rateLimit"`
-	ExcludedURLs          []string `json:"excludedURLs"`
-	AllowedUserDomains    []string `json:"allowedUserDomains"`
+	// ProviderURL is the base URL of the OIDC provider (required)
+	// Example: https://accounts.google.com
+	ProviderURL string `json:"providerURL"`
+
+	// RevocationURL is the endpoint for revoking tokens (optional)
+	// If not provided, it will be discovered from provider metadata
+	RevocationURL string `json:"revocationURL"`
+
+	// CallbackURL is the path where the OIDC provider will redirect after authentication (required)
+	// Example: /oauth2/callback
+	CallbackURL string `json:"callbackURL"`
+
+	// LogoutURL is the path for handling logout requests (optional)
+	// If not provided, it will be set to CallbackURL + "/logout"
+	LogoutURL string `json:"logoutURL"`
+
+	// ClientID is the OAuth 2.0 client identifier (required)
+	ClientID string `json:"clientID"`
+
+	// ClientSecret is the OAuth 2.0 client secret (required)
+	ClientSecret string `json:"clientSecret"`
+
+	// Scopes defines the OAuth 2.0 scopes to request (optional)
+	// Defaults to ["openid", "profile", "email"] if not provided
+	Scopes []string `json:"scopes"`
+
+	// LogLevel sets the logging verbosity (optional)
+	// Valid values: "debug", "info", "error"
+	// Default: "info"
+	LogLevel string `json:"logLevel"`
+
+	// SessionEncryptionKey is used to encrypt session data (required)
+	// Must be a secure random string
+	SessionEncryptionKey string `json:"sessionEncryptionKey"`
+
+	// ForceHTTPS forces the use of HTTPS for all URLs (optional)
+	// Default: false
+	ForceHTTPS bool `json:"forceHTTPS"`
+
+	// RateLimit sets the maximum number of requests per second (optional)
+	// Default: 100
+	RateLimit int `json:"rateLimit"`
+
+	// ExcludedURLs lists paths that bypass authentication (optional)
+	// Example: ["/health", "/metrics"]
+	ExcludedURLs []string `json:"excludedURLs"`
+
+	// AllowedUserDomains restricts access to specific email domains (optional)
+	// Example: ["company.com", "subsidiary.com"]
+	AllowedUserDomains []string `json:"allowedUserDomains"`
+
+	// AllowedRolesAndGroups restricts access to users with specific roles or groups (optional)
+	// Example: ["admin", "developer"]
 	AllowedRolesAndGroups []string `json:"allowedRolesAndGroups"`
-	OIDCEndSessionURL     string   `json:"oidcEndSessionURL"`
-	PostLogoutRedirectURI string   `json:"postLogoutRedirectURI"`
-	HTTPClient            *http.Client
+
+	// OIDCEndSessionURL is the provider's end session endpoint (optional)
+	// If not provided, it will be discovered from provider metadata
+	OIDCEndSessionURL string `json:"oidcEndSessionURL"`
+
+	// PostLogoutRedirectURI is the URL to redirect to after logout (optional)
+	// Default: "/"
+	PostLogoutRedirectURI string `json:"postLogoutRedirectURI"`
+
+	// HTTPClient allows customizing the HTTP client used for OIDC operations (optional)
+	HTTPClient *http.Client
 }
 
-// CreateConfig creates a new Config with default values
+// CreateConfig creates a new Config with sensible default values.
+// Default values are set for optional fields:
+//   - Scopes: ["openid", "profile", "email"]
+//   - LogLevel: "info"
+//   - LogoutURL: CallbackURL + "/logout"
+//   - RateLimit: 100 requests per second
+//   - PostLogoutRedirectURI: "/"
 func CreateConfig() *Config {
 	c := &Config{}
 
@@ -56,14 +114,22 @@ func CreateConfig() *Config {
 	return c
 }
 
-// Validate validates the Config
+// Validate performs validation checks on the Config.
+// It ensures all required fields are set and have valid values.
+// Returns an error if any validation check fails.
 func (c *Config) Validate() error {
 	if c.ProviderURL == "" {
 		return fmt.Errorf("providerURL is required")
 	}
+	if !isValidURL(c.ProviderURL) {
+		return fmt.Errorf("providerURL must be a valid URL")
+	}
 	if c.CallbackURL == "" {
 		return fmt.Errorf("callbackURL is required")
 	}
+	if !strings.HasPrefix(c.CallbackURL, "/") {
+		return fmt.Errorf("callbackURL must start with /")
+	}
 	if c.ClientID == "" {
 		return fmt.Errorf("clientID is required")
 	}
@@ -73,17 +139,48 @@ func (c *Config) Validate() error {
 	if c.SessionEncryptionKey == "" {
 		return fmt.Errorf("sessionEncryptionKey is required")
 	}
+	if len(c.SessionEncryptionKey) < 32 {
+		return fmt.Errorf("sessionEncryptionKey must be at least 32 characters long")
+	}
+	if c.RateLimit < 0 {
+		return fmt.Errorf("rateLimit must be non-negative")
+	}
+	if c.LogLevel != "" && !isValidLogLevel(c.LogLevel) {
+		return fmt.Errorf("logLevel must be one of: debug, info, error")
+	}
 	return nil
 }
 
-// Logger is a simple logger with different levels
+// isValidURL checks if the provided string is a valid URL
+func isValidURL(s string) bool {
+	u, err := url.Parse(s)
+	return err == nil && u.Scheme != "" && u.Host != ""
+}
+
+// isValidLogLevel checks if the provided log level is valid
+func isValidLogLevel(level string) bool {
+	return level == "debug" || level == "info" || level == "error"
+}
+
+// Logger provides structured logging capabilities with different severity levels.
+// It supports error, info, and debug levels with appropriate output streams
+// and formatting for each level.
 type Logger struct {
+	// logError handles error-level messages, writing to stderr
 	logError *log.Logger
-	logInfo  *log.Logger
+	// logInfo handles informational messages, writing to stdout
+	logInfo *log.Logger
+	// logDebug handles debug-level messages, writing to stdout when debug is enabled
 	logDebug *log.Logger
 }
 
-// NewLogger creates a new Logger
+// NewLogger creates a new Logger with the specified log level.
+// The log level determines which messages are output:
+//   - "debug": Outputs all messages (debug, info, error)
+//   - "info": Outputs info and error messages
+//   - "error": Outputs only error messages
+// Error messages are always written to stderr, while info and debug
+// messages are written to stdout when enabled.
 func NewLogger(logLevel string) *Logger {
 	logError := log.New(io.Discard, "ERROR: TraefikOidcPlugin: ", log.Ldate|log.Ltime)
 	logInfo := log.New(io.Discard, "INFO: TraefikOidcPlugin: ", log.Ldate|log.Ltime)
@@ -103,37 +200,51 @@ func NewLogger(logLevel string) *Logger {
 	}
 }
 
-// Info logs an info message
+// Info logs an informational message.
+// These messages are intended for general operational information
+// and are written to stdout.
 func (l *Logger) Info(format string, args ...interface{}) {
 	l.logInfo.Printf(format, args...)
 }
 
-// Debug logs a debug message
+// Debug logs a debug message.
+// These messages are only output when debug level logging is enabled
+// and are intended for detailed troubleshooting information.
 func (l *Logger) Debug(format string, args ...interface{}) {
 	l.logDebug.Printf(format, args...)
 }
 
-// Error logs an error message
+// Error logs an error message.
+// These messages indicate problems that need attention and are
+// always written to stderr regardless of the log level.
 func (l *Logger) Error(format string, args ...interface{}) {
 	l.logError.Printf(format, args...)
 }
 
-// Infof logs an info message
+// Infof logs an informational message using Printf formatting.
+// These messages are intended for general operational information
+// and are written to stdout.
 func (l *Logger) Infof(format string, args ...interface{}) {
 	l.logInfo.Printf(format, args...)
 }
 
-// Debugf logs a debug message
+// Debugf logs a debug message using Printf formatting.
+// These messages are only output when debug level logging is enabled
+// and are intended for detailed troubleshooting information.
 func (l *Logger) Debugf(format string, args ...interface{}) {
 	l.logDebug.Printf(format, args...)
 }
 
-// Errorf logs an error message
+// Errorf logs an error message using Printf formatting.
+// These messages indicate problems that need attention and are
+// always written to stderr regardless of the log level.
 func (l *Logger) Errorf(format string, args ...interface{}) {
 	l.logError.Printf(format, args...)
 }
 
-// handleError writes an error message to the response and logs it
+// handleError writes an error message to both the HTTP response and the error log.
+// It ensures consistent error handling across the middleware by logging the error
+// and sending an appropriate HTTP response to the client.
 func handleError(w http.ResponseWriter, message string, code int, logger *Logger) {
 	logger.Error(message)
 	http.Error(w, message, code)