chore: initial commit

internal/pkg/gwauth/gateway.go

@@ -0,0 +1,96 @@
+// Copyright (C) 2024 Declan Teevan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package gwauth
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+
+	"google.golang.org/grpc/metadata"
+
+	"github.com/hexolan/stocklet/internal/pkg/errors"
+)
+
+const JWTPayloadHeader string = "X-JWT-Payload"
+
+type JWTClaims struct {
+	Subject  string `json:"sub"`
+	IssuedAt int64  `json:"iat"`
+	Expiry   int64  `json:"exp"`
+}
+
+func IsGatewayRequest(ctx context.Context) (bool, *metadata.MD) {
+	// Check the gRPC request has metadata
+	md, exists := metadata.FromIncomingContext(ctx)
+	if !exists {
+		return false, nil
+	}
+
+	if len(md.Get("from-gateway")) != 0 {
+		return true, &md
+	}
+
+	return false, &md
+}
+
+func GetGatewayUser(md *metadata.MD) (*JWTClaims, error) {
+	// Check a token payload has been passed down
+	// Envoy validates JWT tokens and provides a "X-JWT-Payload" header (containing base64 JWT token claims)
+	authorization := md.Get("jwt-payload")
+	if len(authorization) != 1 {
+		return nil, errors.NewServiceError(errors.ErrCodeUnauthorised, "invalid jwt")
+	}
+
+	// User is authenticated
+	// Attempt to decode the jwt-payload
+	bytes, err := base64.StdEncoding.DecodeString(authorization[0])
+	if err != nil {
+		return nil, errors.WrapServiceError(errors.ErrCodeUnauthorised, "malformed jwt", err)
+	}
+
+	var claims JWTClaims
+	err = json.Unmarshal(bytes, &claims)
+	if err != nil {
+		return nil, errors.WrapServiceError(errors.ErrCodeUnauthorised, "malformed jwt", err)
+	}
+
+	return &claims, nil
+}
+
+func getTokenPayload(md *metadata.MD) (*JWTClaims, error) {
+	// Envoy validates JWT tokens and provides a header containing
+	// valid auth token claims in base64 format.
+	authorization := md.Get("jwt-payload")
+	if len(authorization) != 1 {
+		return nil, errors.NewServiceError(errors.ErrCodeUnauthorised, "auth token not provided")
+	}
+
+	// User is authenticated
+	// Attempt to decode the jwt-payload
+	bytes, err := base64.StdEncoding.DecodeString(authorization[0])
+	if err != nil {
+		return nil, errors.WrapServiceError(errors.ErrCodeUnauthorised, "malformed jwt", err)
+	}
+
+	var claims JWTClaims
+	err = json.Unmarshal(bytes, &claims)
+	if err != nil {
+		return nil, errors.WrapServiceError(errors.ErrCodeUnauthorised, "malformed jwt", err)
+	}
+
+	return &claims, nil
+}