lib/http: Add authentication middleware with basic auth implementation

lib/http/auth/basic.go

@@ -0,0 +1,119 @@
+package auth
+
+import (
+	"context"
+	"encoding/base64"
+	"net/http"
+	"strings"
+
+	auth "github.com/abbot/go-http-auth"
+	"github.com/rclone/rclone/fs"
+	httplib "github.com/rclone/rclone/lib/http"
+)
+
+// parseAuthorization parses the Authorization header into user, pass
+// it returns a boolean as to whether the parse was successful
+func parseAuthorization(r *http.Request) (user, pass string, ok bool) {
+	authHeader := r.Header.Get("Authorization")
+	if authHeader != "" {
+		s := strings.SplitN(authHeader, " ", 2)
+		if len(s) == 2 && s[0] == "Basic" {
+			b, err := base64.StdEncoding.DecodeString(s[1])
+			if err == nil {
+				parts := strings.SplitN(string(b), ":", 2)
+				user = parts[0]
+				if len(parts) > 1 {
+					pass = parts[1]
+					ok = true
+				}
+			}
+		}
+	}
+	return
+}
+
+type contextUserType struct{}
+
+// ContextUserKey is a simple context key for storing the username of the request
+var ContextUserKey = &contextUserType{}
+
+type contextAuthType struct{}
+
+// ContextAuthKey is a simple context key for storing info returned by CustomAuthFn
+var ContextAuthKey = &contextAuthType{}
+
+// LoggedBasicAuth extends BasicAuth to include access logging
+type LoggedBasicAuth struct {
+	auth.BasicAuth
+}
+
+// CheckAuth extends BasicAuth.CheckAuth to emit a log entry for unauthorised requests
+func (a *LoggedBasicAuth) CheckAuth(r *http.Request) string {
+	username := a.BasicAuth.CheckAuth(r)
+	if username == "" {
+		user, _, _ := parseAuthorization(r)
+		fs.Infof(r.URL.Path, "%s: Unauthorized request from %s", r.RemoteAddr, user)
+	}
+	return username
+}
+
+// NewLoggedBasicAuthenticator instantiates a new instance of LoggedBasicAuthenticator
+func NewLoggedBasicAuthenticator(realm string, secrets auth.SecretProvider) *LoggedBasicAuth {
+	return &LoggedBasicAuth{BasicAuth: auth.BasicAuth{Realm: realm, Secrets: secrets}}
+}
+
+// Helper to generate required interface for middleware
+func basicAuth(authenticator *LoggedBasicAuth) httplib.Middleware {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			if username := authenticator.CheckAuth(r); username == "" {
+				authenticator.RequireAuth(w, r)
+			} else {
+				r = r.WithContext(context.WithValue(r.Context(), ContextUserKey, username))
+				next.ServeHTTP(w, r)
+			}
+		})
+	}
+}
+
+// HtPasswdAuth instantiates middleware that authenticates against the passed htpasswd file
+func HtPasswdAuth(path, realm string) httplib.Middleware {
+	fs.Infof(nil, "Using %q as htpasswd storage", path)
+	secretProvider := auth.HtpasswdFileProvider(path)
+	authenticator := NewLoggedBasicAuthenticator(realm, secretProvider)
+	return basicAuth(authenticator)
+}
+
+// SingleAuth instantiates middleware that authenticates for a single user
+func SingleAuth(user, pass, realm string) httplib.Middleware {
+	fs.Infof(nil, "Using --user %s --pass XXXX as authenticated user", user)
+	pass = string(auth.MD5Crypt([]byte(pass), []byte("dlPL2MqE"), []byte("$1$")))
+	secretProvider := func(user, realm string) string {
+		if user == user {
+			return pass
+		}
+		return ""
+	}
+	authenticator := NewLoggedBasicAuthenticator(realm, secretProvider)
+	return basicAuth(authenticator)
+}
+
+// CustomAuth instantiates middleware that authenticates using a custom function
+func CustomAuth(fn CustomAuthFn, realm string) httplib.Middleware {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			user, pass, ok := parseAuthorization(r)
+			if ok {
+				value, err := fn(user, pass)
+				if err != nil {
+					fs.Infof(r.URL.Path, "%s: Auth failed from %s: %v", r.RemoteAddr, user, err)
+					auth.NewBasicAuthenticator(realm, func(user, realm string) string { return "" }).RequireAuth(w, r) //Reuse BasicAuth error reporting
+					return
+				}
+				if value != nil {
+					r = r.WithContext(context.WithValue(r.Context(), ContextAuthKey, value))
+				}
+			}
+		})
+	}
+}