feat: initial commit

internal/auth/jwt.go

@@ -0,0 +1,47 @@
+package auth
+
+import (
+	"fmt"
+
+	"github.com/golang-jwt/jwt/v5"
+)
+
+type JWTAuthenticator struct {
+	secret string
+	aud    string
+	iss    string
+}
+
+func NewJWTAuthenticator(secret, aud, iss string) *JWTAuthenticator {
+	return &JWTAuthenticator{
+		secret: secret,
+		aud:    aud,
+		iss:    iss,
+	}
+}
+
+func (j *JWTAuthenticator) GenerateToken(claims jwt.Claims) (string, error) {
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+
+	tokenString, err := token.SignedString([]byte(j.secret))
+	if err != nil {
+		return "", err
+	}
+
+	return tokenString, nil
+}
+
+func (j *JWTAuthenticator) ValidateToken(tokenString string) (*jwt.Token, error) {
+	return jwt.Parse(tokenString, func(t *jwt.Token) (any, error) {
+		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
+			return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
+		}
+
+		return []byte(j.secret), nil
+	},
+		jwt.WithExpirationRequired(),
+		jwt.WithAudience(j.aud),
+		jwt.WithIssuer(j.iss),
+		jwt.WithValidMethods([]string{jwt.SigningMethodHS256.Name}),
+	)
+}