A small utility for swapping the hosts from keycloak SSO metadata

go.mod

module saml-replace

go 1.21.5

saml-replace.go

package main

// saml-replace is a small utility for generating a SAML service provider
// metadata URL to provide to a clinic that's integrating their SSO.
//
// git clone git@gist.github.com:4d4778b6b9ef65b87fd3ab4b07887159.git saml-replace
//
//   $ ./saml-replace \
//         --keycloak-url <URL where you downloaded the SAML metadata (XML)> \
//         --xml-filename <filename where you saved the SAML metadata XML>

import (
	"encoding/xml"
	"flag"
	"fmt"
	"log"
	"net/url"
	"os"
)

type samlMetadata struct {
	EntityID string `xml:"entityID,attr"`
}

func main() {
	var keycloakURL, xmlFilename string
	flag.StringVar(&keycloakURL, "keycloak-url", "", "the keycloak URL with the metadata XML")
	flag.StringVar(&xmlFilename, "xml-filename", "-", "the XML metadata from keycloak")
	flag.Parse()

	var f *os.File = os.Stdin
	if xmlFilename != "-" {
		xmlFile, err := os.Open(xmlFilename)
		if err != nil {
			log.Fatalf("opening XML filename %q: %s", xmlFilename, err)
		}
		defer xmlFile.Close()
		f = xmlFile
	}

	metadata := &samlMetadata{}
	if err := xml.NewDecoder(f).Decode(&metadata); err != nil {
		log.Fatal("parsing XML: %s", err)
	}

	entityURL, err := url.Parse(metadata.EntityID)
	if err != nil {
		log.Fatalf("parsing entityID URL: %s", err)
	}

	kcURL, err := url.Parse(keycloakURL)
	if err != nil {
		log.Fatalf("parsing keycloak-url: %s", err)
	}

	kcURL.Host = entityURL.Host

	fmt.Println(kcURL.String())
}