Add JWT authorization functionality.

cmd/server/main.go

@@ -5,9 +5,11 @@ import (
 	"net/http"
 	"os"
 	"shagram/internal/api"
+	"shagram/internal/auth"
 	"shagram/internal/db"
 	"shagram/internal/models"
 	"shagram/internal/websocket"
+	"time"
 
 	"github.com/gin-gonic/gin"
 )
@@ -29,6 +31,27 @@ func main() {
 
 	router := gin.Default()
 
+	router.POST("/api/auth/login", func(c *gin.Context) {
+		var req struct {
+			Username string `json:"username"`
+		}
+		if err := c.ShouldBindJSON(&req); err != nil || req.Username == "" {
+			c.JSON(http.StatusBadRequest, gin.H{"error": "username required"})
+			return
+		}
+
+		token, err := auth.NewAccessToken(req.Username, time.Hour)
+		if err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+			return
+		}
+
+		c.JSON(200, gin.H{"access_token": token})
+	})
+	router.GET("/api/me", auth.Middleware(), func(c *gin.Context) {
+		username := c.GetString(auth.CtxUsernameKey)
+		c.JSON(200, gin.H{"username": username})
+	})
 	router.GET("/ws/:room", func(c *gin.Context) {
 		api.WebSocketHandler(hub, database)(c)
 	})

deploy/shagram/compose.yaml

@@ -6,6 +6,7 @@ services:
     container_name: shagram-app
     environment:
       - DATABASE_PATH=/app/data/shagram.db
+      - JWT_SECRET=${JWT_SECRET}
     volumes:
       - shagram_data:/app/data
     expose:

go.mod

@@ -14,6 +14,7 @@ require (
 	github.com/go-playground/validator/v10 v10.27.0 // indirect
 	github.com/goccy/go-json v0.10.2 // indirect
 	github.com/goccy/go-yaml v1.18.0 // indirect
+	github.com/golang-jwt/jwt/v5 v5.3.0 // indirect
 	github.com/gorilla/websocket v1.5.3 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/cpuid/v2 v2.3.0 // indirect

go.sum

@@ -22,6 +22,8 @@ github.com/goccy/go-json v0.10.2 h1:CrxCmQqYDkv1z7lO7Wbh2HN93uovUHgrECaO5ZrCXAU=
 github.com/goccy/go-json v0.10.2/go.mod h1:6MelG93GURQebXPDq3khkgXZkazVtN9CRI+MGFi0w8I=
 github.com/goccy/go-yaml v1.18.0 h1:8W7wMFS12Pcas7KU+VVkaiCng+kG8QiFeFwzFb+rwuw=
 github.com/goccy/go-yaml v1.18.0/go.mod h1:XBurs7gK8ATbW4ZPGKgcbrY1Br56PdM69F7LkFRi1kA=
+github.com/golang-jwt/jwt/v5 v5.3.0 h1:pv4AsKCKKZuqlgs5sUmn4x8UlGa0kEVt/puTpKx9vvo=
+github.com/golang-jwt/jwt/v5 v5.3.0/go.mod h1:fxCRLWMO43lRc8nhHWY6LGqRcf+1gQWArsqaEUEa5bE=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
 github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=
 github.com/gorilla/websocket v1.5.3/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=

internal/auth/jwt.go

@@ -0,0 +1,64 @@
+package auth
+
+import (
+	"errors"
+	"os"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+)
+
+type Claims struct {
+	Username string `json:"username"`
+	jwt.RegisteredClaims
+}
+
+func secret() ([]byte, error) {
+	s := os.Getenv("JWT_SECRET")
+	if s == "" {
+		return nil, errors.New("JWT_SECRET is not set")
+	}
+	return []byte(s), nil
+}
+
+func NewAccessToken(username string, ttl time.Duration) (string, error) {
+	key, err := secret()
+	if err != nil {
+		return "", err
+	}
+	now := time.Now()
+	claims := Claims{
+		Username: username,
+		RegisteredClaims: jwt.RegisteredClaims{
+			Subject:   username,
+			IssuedAt:  jwt.NewNumericDate(now),
+			ExpiresAt: jwt.NewNumericDate(now.Add(ttl)),
+		},
+	}
+
+	t := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+	return t.SignedString(key)
+}
+
+func ParseAccessToken(tokenString string) (*Claims, error) {
+	key, err := secret()
+	if err != nil {
+		return nil, err
+	}
+
+	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (any, error) {
+		return key, nil
+	},
+		jwt.WithValidMethods([]string{jwt.SigningMethodHS256.Alg()}),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	claims, ok := token.Claims.(*Claims)
+	if !ok || !token.Valid {
+		return nil, errors.New("invalid token")
+	}
+
+	return claims, nil
+}

internal/auth/middleware.go

@@ -0,0 +1,41 @@
+package auth
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+const CtxUsernameKey = "username"
+
+func Middleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		h := c.GetHeader("Authorization")
+		if h == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "missing Authorization header"})
+			return
+		}
+
+		const prefix = "Bearer "
+		if !strings.HasPrefix(h, prefix) {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "expected Bearer token"})
+			return
+		}
+
+		raw := strings.TrimSpace(strings.TrimPrefix(h, prefix))
+		if raw == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "empty token"})
+			return
+		}
+
+		claims, err := ParseAccessToken(raw)
+		if err != nil {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid token"})
+			return
+		}
+
+		c.Set(CtxUsernameKey, claims.Username)
+		c.Next()
+	}
+}