JWT, KeyAuth, CSRF multivalue extractors (#2060)

* CSRF, JWT, KeyAuth middleware support for multivalue value extractors
* Add flag to JWT and KeyAuth middleware to allow continuing execution `next(c)` when error handler decides to swallow the error (returns nil).

Author: aldas

echo.go

@@ -111,10 +111,10 @@ type (
 	}
 
 	// MiddlewareFunc defines a function to process middleware.
-	MiddlewareFunc func(HandlerFunc) HandlerFunc
+	MiddlewareFunc func(next HandlerFunc) HandlerFunc
 
 	// HandlerFunc defines a function to serve HTTP requests.
-	HandlerFunc func(Context) error
+	HandlerFunc func(c Context) error
 
 	// HTTPErrorHandler is a centralized HTTP error handler.
 	HTTPErrorHandler func(error, Context)

middleware/csrf.go

@@ -2,9 +2,7 @@ package middleware
 
 import (
 	"crypto/subtle"
-	"errors"
 	"net/http"
-	"strings"
 	"time"
 
 	"github.com/labstack/echo/v4"
@@ -21,13 +19,15 @@ type (
 		TokenLength uint8 `yaml:"token_length"`
 		// Optional. Default value 32.
 
-		// TokenLookup is a string in the form of "<source>:<key>" that is used
+		// TokenLookup is a string in the form of "<source>:<name>" or "<source>:<name>,<source>:<name>" that is used
 		// to extract token from the request.
 		// Optional. Default value "header:X-CSRF-Token".
 		// Possible values:
-		// - "header:<name>"
-		// - "form:<name>"
+		// - "header:<name>" or "header:<name>:<cut-prefix>"
 		// - "query:<name>"
+		// - "form:<name>"
+		// Multiple sources example:
+		// - "header:X-CSRF-Token,query:csrf"
 		TokenLookup string `yaml:"token_lookup"`
 
 		// Context key to store generated CSRF token into context.
@@ -62,12 +62,11 @@ type (
 		// Optional. Default value SameSiteDefaultMode.
 		CookieSameSite http.SameSite `yaml:"cookie_same_site"`
 	}
-
-	// csrfTokenExtractor defines a function that takes `echo.Context` and returns
-	// either a token or an error.
-	csrfTokenExtractor func(echo.Context) (string, error)
 )
 
+// ErrCSRFInvalid is returned when CSRF check fails
+var ErrCSRFInvalid = echo.NewHTTPError(http.StatusForbidden, "invalid csrf token")
+
 var (
 	// DefaultCSRFConfig is the default CSRF middleware config.
 	DefaultCSRFConfig = CSRFConfig{
@@ -114,14 +113,9 @@ func CSRFWithConfig(config CSRFConfig) echo.MiddlewareFunc {
 		config.CookieSecure = true
 	}
 
-	// Initialize
-	parts := strings.Split(config.TokenLookup, ":")
-	extractor := csrfTokenFromHeader(parts[1])
-	switch parts[0] {
-	case "form":
-		extractor = csrfTokenFromForm(parts[1])
-	case "query":
-		extractor = csrfTokenFromQuery(parts[1])
+	extractors, err := createExtractors(config.TokenLookup, "")
+	if err != nil {
+		panic(err)
 	}
 
 	return func(next echo.HandlerFunc) echo.HandlerFunc {
@@ -130,28 +124,50 @@ func CSRFWithConfig(config CSRFConfig) echo.MiddlewareFunc {
 				return next(c)
 			}
 
-			req := c.Request()
-			k, err := c.Cookie(config.CookieName)
 			token := ""
-
-			// Generate token
-			if err != nil {
-				token = random.String(config.TokenLength)
+			if k, err := c.Cookie(config.CookieName); err != nil {
+				token = random.String(config.TokenLength) // Generate token
 			} else {
-				// Reuse token
-				token = k.Value
+				token = k.Value // Reuse token
 			}
 
-			switch req.Method {
+			switch c.Request().Method {
 			case http.MethodGet, http.MethodHead, http.MethodOptions, http.MethodTrace:
 			default:
 				// Validate token only for requests which are not defined as 'safe' by RFC7231
-				clientToken, err := extractor(c)
-				if err != nil {
-					return echo.NewHTTPError(http.StatusBadRequest, err.Error())
+				var lastExtractorErr error
+				var lastTokenErr error
+			outer:
+				for _, extractor := range extractors {
+					clientTokens, err := extractor(c)
+					if err != nil {
+						lastExtractorErr = err
+						continue
+					}
+
+					for _, clientToken := range clientTokens {
+						if validateCSRFToken(token, clientToken) {
+							lastTokenErr = nil
+							lastExtractorErr = nil
+							break outer
+						}
+						lastTokenErr = ErrCSRFInvalid
+					}
 				}
-				if !validateCSRFToken(token, clientToken) {
-					return echo.NewHTTPError(http.StatusForbidden, "invalid csrf token")
+				if lastTokenErr != nil {
+					return lastTokenErr
+				} else if lastExtractorErr != nil {
+					// ugly part to preserve backwards compatible errors. someone could rely on them
+					if lastExtractorErr == errQueryExtractorValueMissing {
+						lastExtractorErr = echo.NewHTTPError(http.StatusBadRequest, "missing csrf token in the query string")
+					} else if lastExtractorErr == errFormExtractorValueMissing {
+						lastExtractorErr = echo.NewHTTPError(http.StatusBadRequest, "missing csrf token in the form parameter")
+					} else if lastExtractorErr == errHeaderExtractorValueMissing {
+						lastExtractorErr = echo.NewHTTPError(http.StatusBadRequest, "missing csrf token in request header")
+					} else {
+						lastExtractorErr = echo.NewHTTPError(http.StatusBadRequest, lastExtractorErr.Error())
+					}
+					return lastExtractorErr
 				}
 			}
 
@@ -184,38 +200,6 @@ func CSRFWithConfig(config CSRFConfig) echo.MiddlewareFunc {
 	}
 }
 
-// csrfTokenFromForm returns a `csrfTokenExtractor` that extracts token from the
-// provided request header.
-func csrfTokenFromHeader(header string) csrfTokenExtractor {
-	return func(c echo.Context) (string, error) {
-		return c.Request().Header.Get(header), nil
-	}
-}
-
-// csrfTokenFromForm returns a `csrfTokenExtractor` that extracts token from the
-// provided form parameter.
-func csrfTokenFromForm(param string) csrfTokenExtractor {
-	return func(c echo.Context) (string, error) {
-		token := c.FormValue(param)
-		if token == "" {
-			return "", errors.New("missing csrf token in the form parameter")
-		}
-		return token, nil
-	}
-}
-
-// csrfTokenFromQuery returns a `csrfTokenExtractor` that extracts token from the
-// provided query parameter.
-func csrfTokenFromQuery(param string) csrfTokenExtractor {
-	return func(c echo.Context) (string, error) {
-		token := c.QueryParam(param)
-		if token == "" {
-			return "", errors.New("missing csrf token in the query string")
-		}
-		return token, nil
-	}
-}
-
 func validateCSRFToken(token, clientToken string) bool {
 	return subtle.ConstantTimeCompare([]byte(token), []byte(clientToken)) == 1
 }