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mux.go
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mux.go
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package runtime
import (
"context"
"errors"
"fmt"
"net/http"
"net/textproto"
"regexp"
"strings"
"github.com/grpc-ecosystem/grpc-gateway/v2/internal/httprule"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/grpclog"
"google.golang.org/grpc/health/grpc_health_v1"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/status"
"google.golang.org/protobuf/proto"
)
// UnescapingMode defines the behavior of ServeMux when unescaping path parameters.
type UnescapingMode int
const (
// UnescapingModeLegacy is the default V2 behavior, which escapes the entire
// path string before doing any routing.
UnescapingModeLegacy UnescapingMode = iota
// UnescapingModeAllExceptReserved unescapes all path parameters except RFC 6570
// reserved characters.
UnescapingModeAllExceptReserved
// UnescapingModeAllExceptSlash unescapes URL path parameters except path
// separators, which will be left as "%2F".
UnescapingModeAllExceptSlash
// UnescapingModeAllCharacters unescapes all URL path parameters.
UnescapingModeAllCharacters
// UnescapingModeDefault is the default escaping type.
// TODO(v3): default this to UnescapingModeAllExceptReserved per grpc-httpjson-transcoding's
// reference implementation
UnescapingModeDefault = UnescapingModeLegacy
)
var encodedPathSplitter = regexp.MustCompile("(/|%2F)")
// A HandlerFunc handles a specific pair of path pattern and HTTP method.
type HandlerFunc func(w http.ResponseWriter, r *http.Request, pathParams map[string]string)
// A Middleware handler wraps another HandlerFunc to do some pre- and/or post-processing of the request. This is used as an alternative to gRPC interceptors when using the direct-to-implementation
// registration methods. It is generally recommended to use gRPC client or server interceptors instead
// where possible.
type Middleware func(HandlerFunc) HandlerFunc
// ServeMux is a request multiplexer for grpc-gateway.
// It matches http requests to patterns and invokes the corresponding handler.
type ServeMux struct {
// handlers maps HTTP method to a list of handlers.
handlers map[string][]handler
middlewares []Middleware
forwardResponseOptions []func(context.Context, http.ResponseWriter, proto.Message) error
forwardResponseRewriter ForwardResponseRewriter
marshalers marshalerRegistry
incomingHeaderMatcher HeaderMatcherFunc
outgoingHeaderMatcher HeaderMatcherFunc
outgoingTrailerMatcher HeaderMatcherFunc
metadataAnnotators []func(context.Context, *http.Request) metadata.MD
errorHandler ErrorHandlerFunc
streamErrorHandler StreamErrorHandlerFunc
routingErrorHandler RoutingErrorHandlerFunc
disablePathLengthFallback bool
unescapingMode UnescapingMode
}
// ServeMuxOption is an option that can be given to a ServeMux on construction.
type ServeMuxOption func(*ServeMux)
// ForwardResponseRewriter is the signature of a function that is capable of rewriting messages
// before they are forwarded in a unary, stream, or error response.
type ForwardResponseRewriter func(ctx context.Context, response proto.Message) (any, error)
// WithForwardResponseRewriter returns a ServeMuxOption that allows for implementers to insert logic
// that can rewrite the final response before it is forwarded.
//
// The response rewriter function is called during unary message forwarding, stream message
// forwarding and when errors are being forwarded.
//
// NOTE: Using this option will likely make what is generated by `protoc-gen-openapiv2` incorrect.
// Since this option involves making runtime changes to the response shape or type.
func WithForwardResponseRewriter(fwdResponseRewriter ForwardResponseRewriter) ServeMuxOption {
return func(sm *ServeMux) {
sm.forwardResponseRewriter = fwdResponseRewriter
}
}
// WithForwardResponseOption returns a ServeMuxOption representing the forwardResponseOption.
//
// forwardResponseOption is an option that will be called on the relevant context.Context,
// http.ResponseWriter, and proto.Message before every forwarded response.
//
// The message may be nil in the case where just a header is being sent.
func WithForwardResponseOption(forwardResponseOption func(context.Context, http.ResponseWriter, proto.Message) error) ServeMuxOption {
return func(serveMux *ServeMux) {
serveMux.forwardResponseOptions = append(serveMux.forwardResponseOptions, forwardResponseOption)
}
}
// WithUnescapingMode sets the escaping type. See the definitions of UnescapingMode
// for more information.
func WithUnescapingMode(mode UnescapingMode) ServeMuxOption {
return func(serveMux *ServeMux) {
serveMux.unescapingMode = mode
}
}
// WithMiddlewares sets server middleware for all handlers. This is useful as an alternative to gRPC
// interceptors when using the direct-to-implementation registration methods and cannot rely
// on gRPC interceptors. It's recommended to use gRPC interceptors instead if possible.
func WithMiddlewares(middlewares ...Middleware) ServeMuxOption {
return func(serveMux *ServeMux) {
serveMux.middlewares = append(serveMux.middlewares, middlewares...)
}
}
// SetQueryParameterParser sets the query parameter parser, used to populate message from query parameters.
// Configuring this will mean the generated OpenAPI output is no longer correct, and it should be
// done with careful consideration.
func SetQueryParameterParser(queryParameterParser QueryParameterParser) ServeMuxOption {
return func(serveMux *ServeMux) {
currentQueryParser = queryParameterParser
}
}
// HeaderMatcherFunc checks whether a header key should be forwarded to/from gRPC context.
type HeaderMatcherFunc func(string) (string, bool)
// DefaultHeaderMatcher is used to pass http request headers to/from gRPC context. This adds permanent HTTP header
// keys (as specified by the IANA, e.g: Accept, Cookie, Host) to the gRPC metadata with the grpcgateway- prefix. If you want to know which headers are considered permanent, you can view the isPermanentHTTPHeader function.
// HTTP headers that start with 'Grpc-Metadata-' are mapped to gRPC metadata after removing the prefix 'Grpc-Metadata-'.
// Other headers are not added to the gRPC metadata.
func DefaultHeaderMatcher(key string) (string, bool) {
switch key = textproto.CanonicalMIMEHeaderKey(key); {
case isPermanentHTTPHeader(key):
return MetadataPrefix + key, true
case strings.HasPrefix(key, MetadataHeaderPrefix):
return key[len(MetadataHeaderPrefix):], true
}
return "", false
}
func defaultOutgoingHeaderMatcher(key string) (string, bool) {
return fmt.Sprintf("%s%s", MetadataHeaderPrefix, key), true
}
func defaultOutgoingTrailerMatcher(key string) (string, bool) {
return fmt.Sprintf("%s%s", MetadataTrailerPrefix, key), true
}
// WithIncomingHeaderMatcher returns a ServeMuxOption representing a headerMatcher for incoming request to gateway.
//
// This matcher will be called with each header in http.Request. If matcher returns true, that header will be
// passed to gRPC context. To transform the header before passing to gRPC context, matcher should return the modified header.
func WithIncomingHeaderMatcher(fn HeaderMatcherFunc) ServeMuxOption {
for _, header := range fn.matchedMalformedHeaders() {
grpclog.Warningf("The configured forwarding filter would allow %q to be sent to the gRPC server, which will likely cause errors. See https://github.com/grpc/grpc-go/pull/4803#issuecomment-986093310 for more information.", header)
}
return func(mux *ServeMux) {
mux.incomingHeaderMatcher = fn
}
}
// matchedMalformedHeaders returns the malformed headers that would be forwarded to gRPC server.
func (fn HeaderMatcherFunc) matchedMalformedHeaders() []string {
if fn == nil {
return nil
}
headers := make([]string, 0)
for header := range malformedHTTPHeaders {
out, accept := fn(header)
if accept && isMalformedHTTPHeader(out) {
headers = append(headers, out)
}
}
return headers
}
// WithOutgoingHeaderMatcher returns a ServeMuxOption representing a headerMatcher for outgoing response from gateway.
//
// This matcher will be called with each header in response header metadata. If matcher returns true, that header will be
// passed to http response returned from gateway. To transform the header before passing to response,
// matcher should return the modified header.
func WithOutgoingHeaderMatcher(fn HeaderMatcherFunc) ServeMuxOption {
return func(mux *ServeMux) {
mux.outgoingHeaderMatcher = fn
}
}
// WithOutgoingTrailerMatcher returns a ServeMuxOption representing a headerMatcher for outgoing response from gateway.
//
// This matcher will be called with each header in response trailer metadata. If matcher returns true, that header will be
// passed to http response returned from gateway. To transform the header before passing to response,
// matcher should return the modified header.
func WithOutgoingTrailerMatcher(fn HeaderMatcherFunc) ServeMuxOption {
return func(mux *ServeMux) {
mux.outgoingTrailerMatcher = fn
}
}
// WithMetadata returns a ServeMuxOption for passing metadata to a gRPC context.
//
// This can be used by services that need to read from http.Request and modify gRPC context. A common use case
// is reading token from cookie and adding it in gRPC context.
func WithMetadata(annotator func(context.Context, *http.Request) metadata.MD) ServeMuxOption {
return func(serveMux *ServeMux) {
serveMux.metadataAnnotators = append(serveMux.metadataAnnotators, annotator)
}
}
// WithErrorHandler returns a ServeMuxOption for configuring a custom error handler.
//
// This can be used to configure a custom error response.
func WithErrorHandler(fn ErrorHandlerFunc) ServeMuxOption {
return func(serveMux *ServeMux) {
serveMux.errorHandler = fn
}
}
// WithStreamErrorHandler returns a ServeMuxOption that will use the given custom stream
// error handler, which allows for customizing the error trailer for server-streaming
// calls.
//
// For stream errors that occur before any response has been written, the mux's
// ErrorHandler will be invoked. However, once data has been written, the errors must
// be handled differently: they must be included in the response body. The response body's
// final message will include the error details returned by the stream error handler.
func WithStreamErrorHandler(fn StreamErrorHandlerFunc) ServeMuxOption {
return func(serveMux *ServeMux) {
serveMux.streamErrorHandler = fn
}
}
// WithRoutingErrorHandler returns a ServeMuxOption for configuring a custom error handler to handle http routing errors.
//
// Method called for errors which can happen before gRPC route selected or executed.
// The following error codes: StatusMethodNotAllowed StatusNotFound StatusBadRequest
func WithRoutingErrorHandler(fn RoutingErrorHandlerFunc) ServeMuxOption {
return func(serveMux *ServeMux) {
serveMux.routingErrorHandler = fn
}
}
// WithDisablePathLengthFallback returns a ServeMuxOption for disable path length fallback.
func WithDisablePathLengthFallback() ServeMuxOption {
return func(serveMux *ServeMux) {
serveMux.disablePathLengthFallback = true
}
}
// WithHealthEndpointAt returns a ServeMuxOption that will add an endpoint to the created ServeMux at the path specified by endpointPath.
// When called the handler will forward the request to the upstream grpc service health check (defined in the
// gRPC Health Checking Protocol).
//
// See here https://grpc-ecosystem.github.io/grpc-gateway/docs/operations/health_check/ for more information on how
// to setup the protocol in the grpc server.
//
// If you define a service as query parameter, this will also be forwarded as service in the HealthCheckRequest.
func WithHealthEndpointAt(healthCheckClient grpc_health_v1.HealthClient, endpointPath string) ServeMuxOption {
return func(s *ServeMux) {
// error can be ignored since pattern is definitely valid
_ = s.HandlePath(
http.MethodGet, endpointPath, func(w http.ResponseWriter, r *http.Request, _ map[string]string,
) {
_, outboundMarshaler := MarshalerForRequest(s, r)
resp, err := healthCheckClient.Check(r.Context(), &grpc_health_v1.HealthCheckRequest{
Service: r.URL.Query().Get("service"),
})
if err != nil {
s.errorHandler(r.Context(), s, outboundMarshaler, w, r, err)
return
}
w.Header().Set("Content-Type", "application/json")
if resp.GetStatus() != grpc_health_v1.HealthCheckResponse_SERVING {
switch resp.GetStatus() {
case grpc_health_v1.HealthCheckResponse_NOT_SERVING, grpc_health_v1.HealthCheckResponse_UNKNOWN:
err = status.Error(codes.Unavailable, resp.String())
case grpc_health_v1.HealthCheckResponse_SERVICE_UNKNOWN:
err = status.Error(codes.NotFound, resp.String())
}
s.errorHandler(r.Context(), s, outboundMarshaler, w, r, err)
return
}
_ = outboundMarshaler.NewEncoder(w).Encode(resp)
})
}
}
// WithHealthzEndpoint returns a ServeMuxOption that will add a /healthz endpoint to the created ServeMux.
//
// See WithHealthEndpointAt for the general implementation.
func WithHealthzEndpoint(healthCheckClient grpc_health_v1.HealthClient) ServeMuxOption {
return WithHealthEndpointAt(healthCheckClient, "/healthz")
}
// NewServeMux returns a new ServeMux whose internal mapping is empty.
func NewServeMux(opts ...ServeMuxOption) *ServeMux {
serveMux := &ServeMux{
handlers: make(map[string][]handler),
forwardResponseOptions: make([]func(context.Context, http.ResponseWriter, proto.Message) error, 0),
forwardResponseRewriter: func(ctx context.Context, response proto.Message) (any, error) { return response, nil },
marshalers: makeMarshalerMIMERegistry(),
errorHandler: DefaultHTTPErrorHandler,
streamErrorHandler: DefaultStreamErrorHandler,
routingErrorHandler: DefaultRoutingErrorHandler,
unescapingMode: UnescapingModeDefault,
}
for _, opt := range opts {
opt(serveMux)
}
if serveMux.incomingHeaderMatcher == nil {
serveMux.incomingHeaderMatcher = DefaultHeaderMatcher
}
if serveMux.outgoingHeaderMatcher == nil {
serveMux.outgoingHeaderMatcher = defaultOutgoingHeaderMatcher
}
if serveMux.outgoingTrailerMatcher == nil {
serveMux.outgoingTrailerMatcher = defaultOutgoingTrailerMatcher
}
return serveMux
}
// Handle associates "h" to the pair of HTTP method and path pattern.
func (s *ServeMux) Handle(meth string, pat Pattern, h HandlerFunc) {
if len(s.middlewares) > 0 {
h = chainMiddlewares(s.middlewares)(h)
}
s.handlers[meth] = append([]handler{{pat: pat, h: h}}, s.handlers[meth]...)
}
// HandlePath allows users to configure custom path handlers.
// refer: https://grpc-ecosystem.github.io/grpc-gateway/docs/operations/inject_router/
func (s *ServeMux) HandlePath(meth string, pathPattern string, h HandlerFunc) error {
compiler, err := httprule.Parse(pathPattern)
if err != nil {
return fmt.Errorf("parsing path pattern: %w", err)
}
tp := compiler.Compile()
pattern, err := NewPattern(tp.Version, tp.OpCodes, tp.Pool, tp.Verb)
if err != nil {
return fmt.Errorf("creating new pattern: %w", err)
}
s.Handle(meth, pattern, h)
return nil
}
// ServeHTTP dispatches the request to the first handler whose pattern matches to r.Method and r.URL.Path.
func (s *ServeMux) ServeHTTP(w http.ResponseWriter, r *http.Request) {
ctx := r.Context()
path := r.URL.Path
if !strings.HasPrefix(path, "/") {
_, outboundMarshaler := MarshalerForRequest(s, r)
s.routingErrorHandler(ctx, s, outboundMarshaler, w, r, http.StatusBadRequest)
return
}
// TODO(v3): remove UnescapingModeLegacy
if s.unescapingMode != UnescapingModeLegacy && r.URL.RawPath != "" {
path = r.URL.RawPath
}
if override := r.Header.Get("X-HTTP-Method-Override"); override != "" && s.isPathLengthFallback(r) {
if err := r.ParseForm(); err != nil {
_, outboundMarshaler := MarshalerForRequest(s, r)
sterr := status.Error(codes.InvalidArgument, err.Error())
s.errorHandler(ctx, s, outboundMarshaler, w, r, sterr)
return
}
r.Method = strings.ToUpper(override)
}
var pathComponents []string
// since in UnescapeModeLegacy, the URL will already have been fully unescaped, if we also split on "%2F"
// in this escaping mode we would be double unescaping but in UnescapingModeAllCharacters, we still do as the
// path is the RawPath (i.e. unescaped). That does mean that the behavior of this function will change its default
// behavior when the UnescapingModeDefault gets changed from UnescapingModeLegacy to UnescapingModeAllExceptReserved
if s.unescapingMode == UnescapingModeAllCharacters {
pathComponents = encodedPathSplitter.Split(path[1:], -1)
} else {
pathComponents = strings.Split(path[1:], "/")
}
lastPathComponent := pathComponents[len(pathComponents)-1]
for _, h := range s.handlers[r.Method] {
// If the pattern has a verb, explicitly look for a suffix in the last
// component that matches a colon plus the verb. This allows us to
// handle some cases that otherwise can't be correctly handled by the
// former LastIndex case, such as when the verb literal itself contains
// a colon. This should work for all cases that have run through the
// parser because we know what verb we're looking for, however, there
// are still some cases that the parser itself cannot disambiguate. See
// the comment there if interested.
var verb string
patVerb := h.pat.Verb()
idx := -1
if patVerb != "" && strings.HasSuffix(lastPathComponent, ":"+patVerb) {
idx = len(lastPathComponent) - len(patVerb) - 1
}
if idx == 0 {
_, outboundMarshaler := MarshalerForRequest(s, r)
s.routingErrorHandler(ctx, s, outboundMarshaler, w, r, http.StatusNotFound)
return
}
comps := make([]string, len(pathComponents))
copy(comps, pathComponents)
if idx > 0 {
comps[len(comps)-1], verb = lastPathComponent[:idx], lastPathComponent[idx+1:]
}
pathParams, err := h.pat.MatchAndEscape(comps, verb, s.unescapingMode)
if err != nil {
var mse MalformedSequenceError
if ok := errors.As(err, &mse); ok {
_, outboundMarshaler := MarshalerForRequest(s, r)
s.errorHandler(ctx, s, outboundMarshaler, w, r, &HTTPStatusError{
HTTPStatus: http.StatusBadRequest,
Err: mse,
})
}
continue
}
s.handleHandler(h, w, r, pathParams)
return
}
// if no handler has found for the request, lookup for other methods
// to handle POST -> GET fallback if the request is subject to path
// length fallback.
// Note we are not eagerly checking the request here as we want to return the
// right HTTP status code, and we need to process the fallback candidates in
// order to do that.
for m, handlers := range s.handlers {
if m == r.Method {
continue
}
for _, h := range handlers {
var verb string
patVerb := h.pat.Verb()
idx := -1
if patVerb != "" && strings.HasSuffix(lastPathComponent, ":"+patVerb) {
idx = len(lastPathComponent) - len(patVerb) - 1
}
comps := make([]string, len(pathComponents))
copy(comps, pathComponents)
if idx > 0 {
comps[len(comps)-1], verb = lastPathComponent[:idx], lastPathComponent[idx+1:]
}
pathParams, err := h.pat.MatchAndEscape(comps, verb, s.unescapingMode)
if err != nil {
var mse MalformedSequenceError
if ok := errors.As(err, &mse); ok {
_, outboundMarshaler := MarshalerForRequest(s, r)
s.errorHandler(ctx, s, outboundMarshaler, w, r, &HTTPStatusError{
HTTPStatus: http.StatusBadRequest,
Err: mse,
})
}
continue
}
// X-HTTP-Method-Override is optional. Always allow fallback to POST.
// Also, only consider POST -> GET fallbacks, and avoid falling back to
// potentially dangerous operations like DELETE.
if s.isPathLengthFallback(r) && m == http.MethodGet {
if err := r.ParseForm(); err != nil {
_, outboundMarshaler := MarshalerForRequest(s, r)
sterr := status.Error(codes.InvalidArgument, err.Error())
s.errorHandler(ctx, s, outboundMarshaler, w, r, sterr)
return
}
s.handleHandler(h, w, r, pathParams)
return
}
_, outboundMarshaler := MarshalerForRequest(s, r)
s.routingErrorHandler(ctx, s, outboundMarshaler, w, r, http.StatusMethodNotAllowed)
return
}
}
_, outboundMarshaler := MarshalerForRequest(s, r)
s.routingErrorHandler(ctx, s, outboundMarshaler, w, r, http.StatusNotFound)
}
// GetForwardResponseOptions returns the ForwardResponseOptions associated with this ServeMux.
func (s *ServeMux) GetForwardResponseOptions() []func(context.Context, http.ResponseWriter, proto.Message) error {
return s.forwardResponseOptions
}
func (s *ServeMux) isPathLengthFallback(r *http.Request) bool {
return !s.disablePathLengthFallback && r.Method == "POST" && r.Header.Get("Content-Type") == "application/x-www-form-urlencoded"
}
type handler struct {
pat Pattern
h HandlerFunc
}
func (s *ServeMux) handleHandler(h handler, w http.ResponseWriter, r *http.Request, pathParams map[string]string) {
h.h(w, r.WithContext(withHTTPPattern(r.Context(), h.pat)), pathParams)
}
func chainMiddlewares(mws []Middleware) Middleware {
return func(next HandlerFunc) HandlerFunc {
for i := len(mws); i > 0; i-- {
next = mws[i-1](next)
}
return next
}
}