client, health/client: set dummy host header on unix:// local communi…

…cation

Go 1.20.6 added a security fix [1] which leads to stricter sanitization
of the HTTP host header in the net/http client. Cilium's pkg/client
currently sets the Host header to the UDS path (e.g.
/var/run/cilium/cilium.sock), however the slashes in that Host header
now lead net/http to reject it.

RFC 7230, Section 5.4 states [2]:

> If the authority component is missing or undefined for the target URI,
> then a client MUST send a Host header field with an empty field-value.

The authority component is undefined for the unix:// scheme. Thus, the
correct value to use would be the empty string. However, this does not
work due to OpenAPI runtime using the same value for the URL's host and
the http client's host header. Thus, use a dummy value "localhost".

[1] https://go.dev/issue/60374
[2] https://datatracker.ietf.org/doc/html/rfc7230#section-5.4

Signed-off-by: Tobias Klauser <tobias@cilium.io>

pkg/client/client.go

@@ -120,6 +120,8 @@ func NewRuntime(host string) (*runtime_client.Runtime, error) {
 		return nil, fmt.Errorf("invalid host format '%s'", host)
 	}
 
+	hostHeader := tmp[1]
+
 	switch tmp[0] {
 	case "tcp":
 		if _, err := url.Parse("tcp://" + tmp[1]); err != nil {
@@ -128,11 +130,15 @@ func NewRuntime(host string) (*runtime_client.Runtime, error) {
 		host = "http://" + tmp[1]
 	case "unix":
 		host = tmp[1]
+		// For local communication (unix domain sockets), the hostname is not used. Leave
+		// Host header empty because otherwise it would be rejected by net/http client-side
+		// sanitization, see https://go.dev/issue/60374.
+		hostHeader = "localhost"
 	}
 
 	transport := configureTransport(nil, tmp[0], host)
 	httpClient := &http.Client{Transport: transport}
-	clientTrans := runtime_client.NewWithClient(tmp[1], clientapi.DefaultBasePath,
+	clientTrans := runtime_client.NewWithClient(hostHeader, clientapi.DefaultBasePath,
 		clientapi.DefaultSchemes, httpClient)
 	return clientTrans, nil
 }

pkg/health/client/client.go

@@ -88,6 +88,8 @@ func NewClient(host string) (*Client, error) {
 		return nil, fmt.Errorf("invalid host format '%s'", host)
 	}
 
+	hostHeader := tmp[1]
+
 	switch tmp[0] {
 	case "tcp":
 		if _, err := url.Parse("tcp://" + tmp[1]); err != nil {
@@ -96,11 +98,15 @@ func NewClient(host string) (*Client, error) {
 		host = "http://" + tmp[1]
 	case "unix":
 		host = tmp[1]
+		// For local communication (unix domain sockets), the hostname is not used. Leave
+		// Host header empty because otherwise it would be rejected by net/http client-side
+		// sanitization, see https://go.dev/issue/60374.
+		hostHeader = "localhost"
 	}
 
 	transport := configureTransport(nil, tmp[0], host)
 	httpClient := &http.Client{Transport: transport}
-	clientTrans := runtime_client.NewWithClient(tmp[1], clientapi.DefaultBasePath,
+	clientTrans := runtime_client.NewWithClient(hostHeader, clientapi.DefaultBasePath,
 		clientapi.DefaultSchemes, httpClient)
 	return &Client{*clientapi.New(clientTrans, strfmt.Default)}, nil
 }