Add POST /api/registration

This URL sets a random 32 octet token as cookie `token` in Base64
encoding.

The SHA256 hash of the binary token is written as response also in
Base64 encoding.

3 files changed, 55 insertions, 0 deletions

diff --git a/handlers.go b/handlers.go
index 141230d..f23171f 100644
--- a/handlers.go
+++ b/handlers.go
@@ -13,6 +13,7 @@ var frontendEmbed embed.FS
 
 func init() {
 	router.HandleFunc("/api/version", version)
+	router.HandleFunc("/api/registration", registration).Methods("POST")
 
 	// frontend must come last to make sure /api takes precedence
 	frontend, err := fs.Sub(frontendEmbed, "build/frontend/public")
@@ -25,3 +26,23 @@ func init() {
 func version(w http.ResponseWriter, r *http.Request) {
 	fmt.Fprint(w, versionTxt)
 }
+
+func registration(w http.ResponseWriter, r *http.Request) {
+	token, err := NewToken()
+	if err != nil {
+		http.Error(w, "Failed to generate token.", http.StatusInternalServerError)
+		return
+	}
+
+	cookie := http.Cookie{
+		Name: "token",
+		Value: token.Private(),
+		HttpOnly: true,
+		Secure: true,
+		SameSite: http.SameSiteStrictMode,
+	}
+
+	http.SetCookie(w, &cookie)
+
+	fmt.Fprintf(w, "%s\n", token.Public())
+}
diff --git a/meson.build b/meson.build
index 0bd75d3..8d35ec0 100644
--- a/meson.build
+++ b/meson.build
@@ -11,6 +11,7 @@ finserv_linux_amd64 = custom_target(
   input : [
     meson.current_source_dir() / 'main.go',
     meson.current_source_dir() / 'handlers.go',
+    meson.current_source_dir() / 'token.go',
   ],
   output : 'finserv-linux-amd64',
   env : {'GOOS': 'linux', 'GOARCH': 'amd64'},
diff --git a/token.go b/token.go
new file mode 100644
index 0000000..bfb77d2
--- /dev/null
+++ b/token.go
@@ -0,0 +1,33 @@
+package main
+
+import (
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+)
+
+type Token struct {
+	secret []byte
+}
+
+func NewToken() (Token, error) {
+	token := Token{}
+	token.secret = make([]byte, 32)
+
+	_, err := rand.Read(token.secret)
+	if err != nil {
+		return token, err
+	}
+
+	return token, nil
+}
+
+func (t Token) Public() string {
+	hash := sha256.Sum256(t.secret)
+
+	return base64.StdEncoding.EncodeToString(hash[:])
+}
+
+func (t Token) Private() string {
+	return base64.StdEncoding.EncodeToString(t.secret[:])
+}