From af79429d5f5fdd1acda3a00be30e8ce324a295ee Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torjus=20H=C3=A5kestad?= <torjus@usit.uio.no>
Date: Sun, 22 Oct 2023 21:35:00 +0200
Subject: [PATCH] Add authmw for other services to use as middleware

---
 authmw/token.go | 92 +++++++++++++++++++++++++++++++++++++++++++++++++
 token.go        |  5 +--
 version.go      |  2 +-
 3 files changed, 96 insertions(+), 3 deletions(-)
 create mode 100644 authmw/token.go

diff --git a/authmw/token.go b/authmw/token.go
new file mode 100644
index 0000000..8f6f9db
--- /dev/null
+++ b/authmw/token.go
@@ -0,0 +1,92 @@
+package authmw
+
+import (
+	"context"
+	"crypto/x509"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"slices"
+	"strings"
+
+	"git.t-juice.club/microfilm/auth"
+	"github.com/golang-jwt/jwt/v5"
+)
+
+func VerifyToken(authURL string, permittedRoles []string) func(http.Handler) http.Handler {
+	// Fetch current pubkey
+	url := fmt.Sprintf("%s/key", authURL)
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		panic(err)
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		panic(err)
+	}
+	defer resp.Body.Close()
+
+	var authResponse auth.PubkeyResponse
+	decoder := json.NewDecoder(resp.Body)
+	if err := decoder.Decode(&authResponse); err != nil {
+		panic(err)
+	}
+
+	// Parse pubkey
+	pub, err := x509.ParsePKIXPublicKey(authResponse.PubKey)
+	if err != nil {
+		panic(err)
+	}
+
+	fn := func(next http.Handler) http.Handler {
+		fn := func(w http.ResponseWriter, r *http.Request) {
+			authHeader := r.Header.Get("Authorization")
+			if !strings.Contains(authHeader, "Bearer ") {
+				// No token, pass if unathorized in permitted
+				// else reject
+				if slices.Contains[[]string, string](permittedRoles, auth.RoleUnauthorized) {
+					next.ServeHTTP(w, r)
+					return
+				}
+
+				// Reject and write error response
+				w.WriteHeader(http.StatusUnauthorized)
+				var errResp auth.ErrorResponse
+				errResp.Message = fmt.Sprintf("Authorization required: %s", strings.Join(permittedRoles, ","))
+				errResp.Status = http.StatusUnauthorized
+
+				encoder := json.NewEncoder(w)
+				_ = encoder.Encode(&errResp)
+				return
+			}
+
+			// Validate token
+			tokenString := strings.Split(authHeader, " ")[1]
+			token, err := jwt.ParseWithClaims(tokenString, &auth.MicrofilmClaims{}, func(t *jwt.Token) (interface{}, error) { return pub, nil })
+			if err != nil {
+				// Reject and write error response
+				w.WriteHeader(http.StatusUnauthorized)
+				var errResp auth.ErrorResponse
+				errResp.Message = fmt.Sprintf("Token verification failed: %s", err)
+				errResp.Status = http.StatusUnauthorized
+
+				encoder := json.NewEncoder(w)
+				_ = encoder.Encode(&errResp)
+				return
+			}
+
+			// Add claims to request context
+			if claims, ok := token.Claims.(*auth.MicrofilmClaims); ok && token.Valid {
+				ctx := context.WithValue(r.Context(), "claims", claims)
+				next.ServeHTTP(w, r.WithContext(ctx))
+				return
+			}
+
+			next.ServeHTTP(w, r)
+		}
+		return http.HandlerFunc(fn)
+	}
+
+	return fn
+}
diff --git a/token.go b/token.go
index 2e061f3..08739af 100644
--- a/token.go
+++ b/token.go
@@ -3,8 +3,9 @@ package auth
 import "github.com/golang-jwt/jwt/v5"
 
 const (
-	RoleUser  = "user"
-	RoleAdmin = "admin"
+	RoleUnauthorized = ""
+	RoleUser         = "user"
+	RoleAdmin        = "admin"
 )
 
 type MicrofilmClaims struct {
diff --git a/version.go b/version.go
index b831765..9811450 100644
--- a/version.go
+++ b/version.go
@@ -1,3 +1,3 @@
 package auth
 
-const Version = "v0.1.0"
+const Version = "v0.1.1"