Add client authorization example

2 files changed, 160 insertions, 1 deletions

diff --git a/examples/auth/auth.go b/examples/auth/auth.go
new file mode 100644
index 0000000..2827bec
--- /dev/null
+++ b/examples/auth/auth.go
@@ -0,0 +1,159 @@
+// +build example
+
+package main
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"fmt"
+	"log"
+
+	"git.sr.ht/~adnano/go-gemini"
+)
+
+type user struct {
+	password string // TODO: use hashes
+	admin    bool
+}
+
+type session struct {
+	username   string
+	authorized bool // whether or not the password was supplied
+}
+
+var (
+	// Map of usernames to user data
+	logins = map[string]user{
+		"admin": {"p@ssw0rd", true}, // NOTE: These are bad passwords!
+		"user1": {"password1", false},
+		"user2": {"password2", false},
+	}
+
+	// Map of certificate fingerprints to sessions
+	sessions = map[string]*session{}
+)
+
+func main() {
+	// Configure a certificate.
+	// To generate a TLS key pair, run:
+	//
+	//     go run -tags=example ../cert
+	cert, err := tls.LoadX509KeyPair("examples/client/localhost.crt", "examples/client/localhost.key")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	handler := &gemini.ServeMux{}
+	handler.HandleFunc("", welcome)
+	handler.HandleFunc("/login", login)
+	handler.HandleFunc("/login/password", loginPassword)
+	handler.HandleFunc("/profile", profile)
+	handler.HandleFunc("/admin", admin)
+	handler.HandleFunc("/logout", logout)
+
+	server := &gemini.Server{
+		Certificate: cert,
+		Handler:     handler,
+	}
+
+	if err := server.ListenAndServe(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func getSession(crt *x509.Certificate) (*session, bool) {
+	fingerprint := gemini.Fingerprint(crt)
+	session, ok := sessions[fingerprint]
+	return session, ok
+}
+
+func welcome(rw *gemini.ResponseWriter, req *gemini.Request) {
+	rw.WriteHeader(gemini.StatusSuccess, "text/gemini")
+	rw.Write([]byte("Welcome to this example.\n=> /login Login\n"))
+}
+
+func login(rw *gemini.ResponseWriter, req *gemini.Request) {
+	if len(req.TLS.PeerCertificates) > 0 {
+		if username := req.URL.RawQuery; username == "" {
+			rw.WriteHeader(gemini.StatusInput, "Username")
+		} else {
+			fingerprint := gemini.Fingerprint(req.TLS.PeerCertificates[0])
+			sessions[fingerprint] = &session{
+				username: username,
+			}
+			// TODO: Remove scheme and host once example client can handle relative redirects
+			rw.WriteHeader(gemini.StatusRedirectTemporary, "gemini://localhost/login/password")
+		}
+	} else {
+		rw.WriteHeader(gemini.StatusClientCertificateRequired, "Certificate required")
+	}
+}
+
+func loginPassword(rw *gemini.ResponseWriter, req *gemini.Request) {
+	if len(req.TLS.PeerCertificates) > 0 {
+		session, ok := getSession(req.TLS.PeerCertificates[0])
+		if !ok {
+			rw.WriteHeader(gemini.StatusCertificateNotAuthorised, "Not authorized")
+			return
+		}
+
+		if password := req.URL.RawQuery; password == "" {
+			rw.WriteHeader(gemini.StatusInput, "Password")
+		} else {
+			expected := logins[session.username].password
+			if password == expected {
+				// TODO: Remove scheme and host once example client can handle relative redirects
+				session.authorized = true
+				rw.WriteHeader(gemini.StatusRedirectTemporary, "gemini://localhost/profile")
+			} else {
+				rw.WriteHeader(gemini.StatusInput, "Wrong password. Please try again.\nPassword:")
+			}
+		}
+	} else {
+		rw.WriteHeader(gemini.StatusClientCertificateRequired, "Certificate required")
+	}
+}
+
+func logout(rw *gemini.ResponseWriter, req *gemini.Request) {
+	if len(req.TLS.PeerCertificates) > 0 {
+		fingerprint := gemini.Fingerprint(req.TLS.PeerCertificates[0])
+		delete(sessions, fingerprint)
+	}
+	rw.WriteHeader(gemini.StatusSuccess, "text/gemini")
+	rw.Write([]byte("Successfully logged out.\n"))
+}
+
+func profile(rw *gemini.ResponseWriter, req *gemini.Request) {
+	if len(req.TLS.PeerCertificates) > 0 {
+		session, ok := getSession(req.TLS.PeerCertificates[0])
+		if !ok {
+			rw.WriteHeader(gemini.StatusCertificateNotAuthorised, "Certificate not authorized")
+			return
+		}
+		user := logins[session.username]
+		profile := fmt.Sprintf("Username: %s\nAdmin: %t\n=> /logout Logout", session.username, user.admin)
+		rw.WriteHeader(gemini.StatusSuccess, "text/gemini")
+		rw.Write([]byte(profile))
+	} else {
+		rw.WriteHeader(gemini.StatusClientCertificateRequired, "Certificate required")
+	}
+}
+
+func admin(rw *gemini.ResponseWriter, req *gemini.Request) {
+	if len(req.TLS.PeerCertificates) > 0 {
+		session, ok := getSession(req.TLS.PeerCertificates[0])
+		if !ok {
+			rw.WriteHeader(gemini.StatusCertificateNotAuthorised, "Certificate not authorized")
+			return
+		}
+		user := logins[session.username]
+		if !user.admin {
+			rw.WriteHeader(gemini.StatusCertificateNotAuthorised, "Admins only!")
+			return
+		}
+		rw.WriteHeader(gemini.StatusSuccess, "text/gemini")
+		rw.Write([]byte("Welcome to the admin portal.\n"))
+	} else {
+		rw.WriteHeader(gemini.StatusClientCertificateRequired, "Certificate required")
+	}
+}
diff --git a/examples/client/client.go b/examples/client/client.go
index 5c1c104..a8256f2 100644
--- a/examples/client/client.go
+++ b/examples/client/client.go
@@ -65,7 +65,7 @@ func makeRequest(url string) {
 	if err != nil {
 		log.Fatal(err)
 	}
-	req.Certificate = cert
+	req.Certificate = &cert
 
 	resp, err := client.Send(req)
 	if err != nil {