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mcp: remove default cross origin protection (#906)

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Fixes #902
This commit is contained in:
Maciej Kisiel 2026-04-24 11:35:22 +02:00 • committed by GitHub
commit 41e1f941bb
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GPG key ID: B5690EEEBB952194
1 changed files with 41 additions and 118 deletions
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42
mcp/streamable.go
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@ -180,9 +180,15 @@ type StreamableHTTPOptions struct {
// CrossOriginProtection allows to customize cross-origin protection.
// The deny handler set in the CrossOriginProtection through SetDenyHandler
// is ignored.
// If nil, default (zero-value) cross-origin protection will be used.
// Use `disablecrossoriginprotection` MCPGODEBUG compatibility parameter
// to disable the default protection until v1.7.0.
// If nil, no cross-origin protection is applied. Use the `enableoriginverification`
// MCPGODEBUG compatibility parameter to enable the default protection until v1.8.0.
//
// Deprecated: wrap the handler with cross-origin protection middleware
// instead. For example:
//
// handler := mcp.NewStreamableHTTPHandler(...)
// protection := http.NewCrossOriginProtection()
// protectedHandler := protection.Handler(handler)
CrossOriginProtection *http.CrossOriginProtection
}
@ -202,7 +208,7 @@ func NewStreamableHTTPHandler(getServer func(*http.Request) *Server, opts *Strea
h.opts.Logger = ensureLogger(h.opts.Logger)
if h.opts.CrossOriginProtection == nil {
if h.opts.CrossOriginProtection == nil && enableoriginverification == "1" {
h.opts.CrossOriginProtection = &http.CrossOriginProtection{}
}
@ -235,15 +241,16 @@ func (h *StreamableHTTPHandler) closeAll() {
// disablelocalhostprotection is a compatibility parameter that allows to disable
// DNS rebinding protection, which was added in the 1.4.0 version of the SDK.
// See the documentation for the mcpgodebug package for instructions how to enable it.
// The option will be removed in the 1.7.0 version of the SDK.
// The option will be removed in the 1.6.0 version of the SDK.
var disablelocalhostprotection = mcpgodebug.Value("disablelocalhostprotection")
// disablecrossoriginprotection is a compatibility parameter that allows to disable
// the verification of the 'Origin' and 'Content-Type' headers, which was added in
// the 1.4.1 version of the SDK. See the documentation for the mcpgodebug package
// for instructions how to enable it.
// The option will be removed in the 1.7.0 version of the SDK.
var disablecrossoriginprotection = mcpgodebug.Value("disablecrossoriginprotection")
// enableoriginverification is a compatibility parameter that restores the
// default cross-origin protection behavior from v1.4.1-v1.5.0. When set to
// "1", a zero-value CrossOriginProtection will be applied if none is
// explicitly provided in StreamableHTTPOptions.
// See the documentation for the mcpgodebug package for instructions how to enable it.
// The option will be removed in the 1.8.0 version of the SDK.
var enableoriginverification = mcpgodebug.Value("enableoriginverification")
func (h *StreamableHTTPHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
// DNS rebinding protection: auto-enabled for localhost servers.
@ -257,17 +264,18 @@ func (h *StreamableHTTPHandler) ServeHTTP(w http.ResponseWriter, req *http.Reque
}
}
if disablecrossoriginprotection != "1" {
if h.opts.CrossOriginProtection != nil {
// Verify the 'Origin' header to protect against CSRF attacks.
if err := h.opts.CrossOriginProtection.Check(req); err != nil {
http.Error(w, err.Error(), http.StatusForbidden)
return
}
// Validate 'Content-Type' header.
if req.Method == http.MethodPost && baseMediaType(req.Header.Get("Content-Type")) != "application/json" {
http.Error(w, "Content-Type must be 'application/json'", http.StatusUnsupportedMediaType)
return
}
}
// Validate 'Content-Type' header.
if req.Method == http.MethodPost && baseMediaType(req.Header.Get("Content-Type")) != "application/json" {
http.Error(w, "Content-Type must be 'application/json'", http.StatusUnsupportedMediaType)
return
}
// Allow multiple 'Accept' headers.