Switch to jwt tokens and allow some extra rdp settings

security/jwt.go

@@ -0,0 +1,70 @@
+package security
+
+import (
+	"errors"
+	"fmt"
+	"github.com/bolkedebruin/rdpgw/protocol"
+	"github.com/dgrijalva/jwt-go/v4"
+	"log"
+	"time"
+)
+
+var SigningKey []byte
+var ExpiryTime time.Duration = 5
+
+type customClaims struct {
+	RemoteServer string `json:"remoteServer"`
+	jwt.StandardClaims
+}
+
+func VerifyPAAToken(s *protocol.SessionInfo, tokenString string) (bool, error) {
+	token, err := jwt.ParseWithClaims(tokenString, &customClaims{}, func(token *jwt.Token) (interface{}, error) {
+		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
+			return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
+		}
+
+		return SigningKey, nil
+	})
+
+	if err != nil {
+		return false, err
+	}
+
+	if _, ok := token.Claims.(*customClaims); ok && token.Valid {
+		return true, nil
+	}
+
+	log.Printf("token validation failed: %s", err)
+	return false, err
+}
+
+func GeneratePAAToken(username string, server string) (string, error) {
+	if len(SigningKey) < 32 {
+		return "", errors.New("token signing key not long enough or not specified")
+	}
+
+	exp := &jwt.Time{
+		Time: time.Now().Add(time.Minute * 5),
+	}
+	now := &jwt.Time{
+		Time: time.Now(),
+	}
+
+	c := customClaims{
+		RemoteServer: server,
+		StandardClaims: jwt.StandardClaims{
+			ExpiresAt: exp,
+			IssuedAt: now,
+			Issuer: "rdpgw",
+			Subject: username,
+		},
+	}
+
+	token := jwt.NewWithClaims(jwt.SigningMethodHS512, c)
+	if ss, err := token.SignedString(SigningKey); err != nil {
+		log.Printf("Cannot sign PAA token %s", err)
+		return "", err
+	} else {
+		return ss, nil
+	}
+}