refactor authentication.go

proxy/pkg/middleware/authentication.go

@@ -8,42 +8,35 @@ import (
 	"time"
 )
 
-// SupportedAuthStrategies stores configured challenges.
-var SupportedAuthStrategies []string
+var (
+	// SupportedAuthStrategies stores configured challenges.
+	SupportedAuthStrategies []string
 
-// ProxyWwwAuthenticate is a list of endpoints that do not rely on reva underlying authentication, such as ocs.
-// services that fallback to reva authentication are declared in the "frontend" command on OCIS. It is a list of strings
-// to be regexp compiled.
-var ProxyWwwAuthenticate = []string{"/ocs/v[12].php/cloud/"}
+	// ProxyWwwAuthenticate is a list of endpoints that do not rely on reva underlying authentication, such as ocs.
+	// services that fallback to reva authentication are declared in the "frontend" command on OCIS. It is a list of strings
+	// to be regexp compiled.
+	ProxyWwwAuthenticate = []string{"/ocs/v[12].php/cloud/"}
+
+	// WWWAuthenticate captures the Www-Authenticate header string.
+	WWWAuthenticate = "Www-Authenticate"
+)
+
+// userAgentLocker aids in dependency injection for helper methods. The set of fields is arbitrary and the only relation
+// they share is to fulfill their duty and lock a User-Agent to its correct challenge if configured.
+type userAgentLocker struct {
+	w        http.ResponseWriter
+	r        *http.Request
+	locks    map[string]string // locks represents a reva user-agent:challenge mapping.
+	fallback string
+}
 
 // Authentication is a higher order authentication middleware.
 func Authentication(opts ...Option) func(next http.Handler) http.Handler {
 	options := newOptions(opts...)
-	if options.OIDCIss != "" {
-		SupportedAuthStrategies = append(SupportedAuthStrategies, "bearer")
-	}
 
-	if options.EnableBasicAuth {
-		SupportedAuthStrategies = append(SupportedAuthStrategies, "basic")
-	}
-
-	oidc := OIDCAuth(
-		Logger(options.Logger),
-		OIDCProviderFunc(options.OIDCProviderFunc),
-		HTTPClient(options.HTTPClient),
-		OIDCIss(options.OIDCIss),
-		TokenCacheSize(options.UserinfoCacheSize),
-		TokenCacheTTL(time.Second*time.Duration(options.UserinfoCacheTTL)),
-		CredentialsByUserAgent(options.CredentialsByUserAgent),
-	)
-
-	basic := BasicAuth(
-		Logger(options.Logger),
-		EnableBasicAuth(options.EnableBasicAuth),
-		AccountsClient(options.AccountsClient),
-		OIDCIss(options.OIDCIss),
-		CredentialsByUserAgent(options.CredentialsByUserAgent),
-	)
+	configureSupportedChallenges(options)
+	oidc := newOIDCAuth(options)
+	basic := newBasicAuth(options)
 
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -62,34 +55,77 @@ func Authentication(opts ...Option) func(next http.Handler) http.Handler {
 	}
 }
 
+// configureSupportedChallenges adds known authentication challenges to the current session.
+func configureSupportedChallenges(options Options) {
+	if options.OIDCIss != "" {
+		SupportedAuthStrategies = append(SupportedAuthStrategies, "bearer")
+	}
+
+	if options.EnableBasicAuth {
+		SupportedAuthStrategies = append(SupportedAuthStrategies, "basic")
+	}
+}
+
 func writeSupportedAuthenticateHeader(w http.ResponseWriter, r *http.Request) {
 	for i := 0; i < len(SupportedAuthStrategies); i++ {
-		w.Header().Add("WWW-Authenticate", fmt.Sprintf("%v realm=\"%s\", charset=\"UTF-8\"", strings.Title(SupportedAuthStrategies[i]), r.Host))
+		w.Header().Add(WWWAuthenticate, fmt.Sprintf("%v realm=\"%s\", charset=\"UTF-8\"", strings.Title(SupportedAuthStrategies[i]), r.Host))
 	}
 }
 
 func removeSuperfluousAuthenticate(w http.ResponseWriter) {
-	w.Header().Del("Www-Authenticate")
+	w.Header().Del(WWWAuthenticate)
 }
 
 // userAgentAuthenticateLockIn sets Www-Authenticate according to configured user agents. This is useful for the case of
 // legacy clients that do not support protocols like OIDC or OAuth and want to lock a given user agent to a challenge
 // such as basic. For more context check https://github.com/cs3org/reva/pull/1350
-func userAgentAuthenticateLockIn(w http.ResponseWriter, req *http.Request, creds map[string]string, fallback string) {
+func userAgentAuthenticateLockIn(w http.ResponseWriter, r *http.Request, locks map[string]string, fallback string) {
+	u := userAgentLocker{
+		w:        w,
+		r:        r,
+		locks:    locks,
+		fallback: fallback,
+	}
+
 	for i := 0; i < len(ProxyWwwAuthenticate); i++ {
-		if r, err := regexp.Compile(ProxyWwwAuthenticate[i]); err == nil {
-			if r.Match([]byte(req.RequestURI)) {
-				for k, v := range creds {
-					if strings.Contains(k, req.UserAgent()) {
-						removeSuperfluousAuthenticate(w)
-						w.Header().Add("Www-Authenticate", fmt.Sprintf("%v realm=\"%s\", charset=\"UTF-8\"", strings.Title(v), req.Host))
-						return
-					}
-				}
-				w.Header().Add("Www-Authenticate", fmt.Sprintf("%v realm=\"%s\", charset=\"UTF-8\"", strings.Title(fallback), req.Host))
-			}
-		} else {
-			// deal with err
-		}
+		evalRequestURI(&u, i)
 	}
 }
+
+func evalRequestURI(l *userAgentLocker, i int) {
+	r := regexp.MustCompile(ProxyWwwAuthenticate[i])
+	if r.Match([]byte(l.r.RequestURI)) {
+		for k, v := range l.locks {
+			if strings.Contains(k, l.r.UserAgent()) {
+				removeSuperfluousAuthenticate(l.w)
+				l.w.Header().Add(WWWAuthenticate, fmt.Sprintf("%v realm=\"%s\", charset=\"UTF-8\"", strings.Title(v), l.r.Host))
+				return
+			}
+		}
+		l.w.Header().Add(WWWAuthenticate, fmt.Sprintf("%v realm=\"%s\", charset=\"UTF-8\"", strings.Title(l.fallback), l.r.Host))
+	}
+}
+
+// newOIDCAuth returns a configured oidc middleware
+func newOIDCAuth(options Options) func(http.Handler) http.Handler {
+	return OIDCAuth(
+		Logger(options.Logger),
+		OIDCProviderFunc(options.OIDCProviderFunc),
+		HTTPClient(options.HTTPClient),
+		OIDCIss(options.OIDCIss),
+		TokenCacheSize(options.UserinfoCacheSize),
+		TokenCacheTTL(time.Second*time.Duration(options.UserinfoCacheTTL)),
+		CredentialsByUserAgent(options.CredentialsByUserAgent),
+	)
+}
+
+// newBasicAuth returns a configured oidc middleware
+func newBasicAuth(options Options) func(http.Handler) http.Handler {
+	return BasicAuth(
+		Logger(options.Logger),
+		EnableBasicAuth(options.EnableBasicAuth),
+		AccountsClient(options.AccountsClient),
+		OIDCIss(options.OIDCIss),
+		CredentialsByUserAgent(options.CredentialsByUserAgent),
+	)
+}