feat: add authn-basic layer

internal/proxy/director/layer/authn/basic/authenticator.go

@@ -0,0 +1,75 @@
+package basic
+
+import (
+	"crypto/sha256"
+	"crypto/subtle"
+	"fmt"
+	"net/http"
+
+	"forge.cadoles.com/cadoles/bouncer/internal/proxy/director/layer/authn"
+	"forge.cadoles.com/cadoles/bouncer/internal/store"
+	"github.com/pkg/errors"
+	"github.com/prometheus/client_golang/prometheus"
+	"golang.org/x/crypto/bcrypt"
+)
+
+type Authenticator struct {
+}
+
+// Authenticate implements authn.Authenticator.
+func (a *Authenticator) Authenticate(w http.ResponseWriter, r *http.Request, layer *store.Layer) (*authn.User, error) {
+	options, err := fromStoreOptions(layer.Options)
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+
+	username, password, ok := r.BasicAuth()
+
+	unauthorized := func() {
+		w.Header().Set("WWW-Authenticate", fmt.Sprintf(`Basic realm="%s", charset="UTF-8"`, stripNonASCII(options.Realm)))
+		http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
+	}
+
+	if !ok {
+		unauthorized()
+		return nil, errors.WithStack(authn.ErrSkipRequest)
+	}
+
+	for _, userInfo := range options.Users {
+		if matches := a.matchUser(userInfo, username, password); !matches {
+			continue
+		}
+
+		metricAuthorizedTotal.With(prometheus.Labels{
+			metricLabelLayer: string(layer.Name),
+			metricLabelProxy: string(layer.Proxy),
+		}).Add(1)
+
+		user := authn.NewUser(userInfo.Username, userInfo.Attributes)
+
+		return user, nil
+	}
+
+	metricForbiddenTotal.With(prometheus.Labels{
+		metricLabelLayer: string(layer.Name),
+		metricLabelProxy: string(layer.Proxy),
+	}).Add(1)
+
+	unauthorized()
+
+	return nil, errors.WithStack(authn.ErrSkipRequest)
+}
+
+func (a *Authenticator) matchUser(user User, username, password string) bool {
+	usernameHash := sha256.Sum256([]byte(username))
+	expectedUsernameHash := sha256.Sum256([]byte(user.Username))
+
+	usernameMatch := (subtle.ConstantTimeCompare(usernameHash[:], expectedUsernameHash[:]) == 1)
+	passwordMatch := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(password)) == nil
+
+	return usernameMatch && passwordMatch
+}
+
+var (
+	_ authn.Authenticator = &Authenticator{}
+)