feat(story-1.4): add session-based authentication with login/logout

_bmad-output/implementation-artifacts/sprint-status.yaml

@@ -38,8 +38,8 @@ development_status:
   epic-1: in-progress
   1-1-project-initialization-walking-skeleton: done
   1-2-database-migration-system: done
-  1-3-user-registration-api: review
-  1-4-session-authentication: backlog
+  1-3-user-registration-api: done
+  1-4-session-authentication: review
   1-5-frontend-auth-foundation: backlog
   epic-1-retrospective: optional
 

cmd/server/main.go

@@ -37,9 +37,10 @@ func main() {
 
 	// Initialize repositories
 	userRepo := repository.NewUserRepository(pool)
+	sessionRepo := repository.NewSessionRepository(pool)
 
 	// Initialize services
-	authService := service.NewAuthService(userRepo)
+	authService := service.NewAuthService(userRepo, sessionRepo)
 
 	// Initialize handlers
 	authHandler := handler.NewAuthHandler(authService)
@@ -72,9 +73,16 @@ func main() {
 			w.Write([]byte(`{"message":"FlowReader API v1"}`))
 		})
 
-		// Auth routes
+		// Auth routes (public)
 		r.Route("/auth", func(r chi.Router) {
 			r.Post("/register", authHandler.Register)
+			r.Post("/login", authHandler.Login)
+			r.Post("/logout", authHandler.Logout)
+		})
+
+		// User routes
+		r.Route("/users", func(r chi.Router) {
+			r.Get("/me", authHandler.Me)
 		})
 	})
 

internal/domain/session.go

@@ -0,0 +1,27 @@
+package domain
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// Session represents an active user session.
+type Session struct {
+	ID        uuid.UUID `json:"id"`
+	UserID    uuid.UUID `json:"user_id"`
+	Token     string    `json:"-"` // Never expose in JSON
+	ExpiresAt time.Time `json:"expires_at"`
+	CreatedAt time.Time `json:"created_at"`
+	UserAgent string    `json:"user_agent,omitempty"`
+	IPAddress string    `json:"ip_address,omitempty"`
+}
+
+// SessionRepository defines the interface for session data access.
+type SessionRepository interface {
+	Create(session *Session) error
+	GetByToken(token string) (*Session, error)
+	Delete(token string) error
+	DeleteByUserID(userID uuid.UUID) error
+	DeleteExpired() (int64, error)
+}

internal/handler/auth.go

@@ -1,10 +1,10 @@
-// Package handler contains HTTP handlers for the REST API.
 package handler
 
 import (
 	"encoding/json"
 	"errors"
 	"net/http"
+	"strings"
 
 	"github.com/michael/flowreader/internal/service"
 )
@@ -45,6 +45,111 @@ func (h *AuthHandler) Register(w http.ResponseWriter, r *http.Request) {
 	respondJSON(w, http.StatusCreated, resp)
 }
 
+// Login handles POST /api/v1/auth/login
+func (h *AuthHandler) Login(w http.ResponseWriter, r *http.Request) {
+	var req service.LoginRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		respondError(w, http.StatusBadRequest, "Invalid request body")
+		return
+	}
+
+	// Add request metadata
+	req.UserAgent = r.UserAgent()
+	req.IPAddress = getClientIP(r)
+
+	resp, err := h.authService.Login(req)
+	if err != nil {
+		if errors.Is(err, service.ErrInvalidCredentials) {
+			respondError(w, http.StatusUnauthorized, "Invalid email or password")
+		} else {
+			respondError(w, http.StatusInternalServerError, "Login failed")
+		}
+		return
+	}
+
+	// Set session cookie
+	http.SetCookie(w, &http.Cookie{
+		Name:     "session_id",
+		Value:    resp.Token,
+		Path:     "/",
+		Expires:  resp.ExpiresAt,
+		HttpOnly: true,
+		Secure:   r.TLS != nil, // Secure only if HTTPS
+		SameSite: http.SameSiteStrictMode,
+	})
+
+	respondJSON(w, http.StatusOK, resp)
+}
+
+// Logout handles POST /api/v1/auth/logout
+func (h *AuthHandler) Logout(w http.ResponseWriter, r *http.Request) {
+	cookie, err := r.Cookie("session_id")
+	if err != nil {
+		respondJSON(w, http.StatusOK, map[string]string{"message": "Already logged out"})
+		return
+	}
+
+	_ = h.authService.Logout(cookie.Value)
+
+	// Clear the cookie
+	http.SetCookie(w, &http.Cookie{
+		Name:     "session_id",
+		Value:    "",
+		Path:     "/",
+		MaxAge:   -1,
+		HttpOnly: true,
+		Secure:   r.TLS != nil,
+		SameSite: http.SameSiteStrictMode,
+	})
+
+	respondJSON(w, http.StatusOK, map[string]string{"message": "Logged out successfully"})
+}
+
+// Me handles GET /api/v1/users/me
+func (h *AuthHandler) Me(w http.ResponseWriter, r *http.Request) {
+	cookie, err := r.Cookie("session_id")
+	if err != nil {
+		respondError(w, http.StatusUnauthorized, "Not authenticated")
+		return
+	}
+
+	user, err := h.authService.GetUserByToken(cookie.Value)
+	if err != nil {
+		respondError(w, http.StatusInternalServerError, "Failed to get user")
+		return
+	}
+	if user == nil {
+		respondError(w, http.StatusUnauthorized, "Session expired")
+		return
+	}
+
+	respondJSON(w, http.StatusOK, service.UserInfo{
+		ID:      user.ID,
+		Email:   user.Email,
+		IsAdmin: user.IsAdmin,
+	})
+}
+
+// getClientIP extracts the client IP from the request.
+func getClientIP(r *http.Request) string {
+	// Check X-Forwarded-For header
+	forwarded := r.Header.Get("X-Forwarded-For")
+	if forwarded != "" {
+		// Take the first IP in the chain
+		parts := strings.Split(forwarded, ",")
+		return strings.TrimSpace(parts[0])
+	}
+
+	// Check X-Real-IP header
+	realIP := r.Header.Get("X-Real-IP")
+	if realIP != "" {
+		return realIP
+	}
+
+	// Fall back to RemoteAddr
+	return r.RemoteAddr
+}
+
 // respondJSON writes a JSON response.
 func respondJSON(w http.ResponseWriter, status int, data interface{}) {
 	w.Header().Set("Content-Type", "application/json")

internal/repository/session.go

@@ -0,0 +1,126 @@
+package repository
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/michael/flowreader/internal/domain"
+)
+
+// SessionRepository implements domain.SessionRepository using PostgreSQL.
+type SessionRepository struct {
+	pool *pgxpool.Pool
+}
+
+// NewSessionRepository creates a new session repository.
+func NewSessionRepository(pool *pgxpool.Pool) *SessionRepository {
+	return &SessionRepository{pool: pool}
+}
+
+// Create inserts a new session into the database.
+func (r *SessionRepository) Create(session *domain.Session) error {
+	ctx := context.Background()
+
+	query := `
+		INSERT INTO sessions (id, user_id, token, expires_at, created_at, user_agent, ip_address)
+		VALUES ($1, $2, $3, $4, $5, $6, $7)
+	`
+
+	_, err := r.pool.Exec(ctx, query,
+		session.ID,
+		session.UserID,
+		session.Token,
+		session.ExpiresAt,
+		session.CreatedAt,
+		session.UserAgent,
+		session.IPAddress,
+	)
+
+	if err != nil {
+		return fmt.Errorf("creating session: %w", err)
+	}
+
+	return nil
+}
+
+// GetByToken retrieves a session by its token.
+func (r *SessionRepository) GetByToken(token string) (*domain.Session, error) {
+	ctx := context.Background()
+
+	query := `
+		SELECT id, user_id, token, expires_at, created_at, user_agent, ip_address
+		FROM sessions
+		WHERE token = $1 AND expires_at > NOW()
+	`
+
+	var session domain.Session
+	var userAgent, ipAddress *string
+	err := r.pool.QueryRow(ctx, query, token).Scan(
+		&session.ID,
+		&session.UserID,
+		&session.Token,
+		&session.ExpiresAt,
+		&session.CreatedAt,
+		&userAgent,
+		&ipAddress,
+	)
+
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, nil // Session not found or expired
+		}
+		return nil, fmt.Errorf("getting session by token: %w", err)
+	}
+
+	if userAgent != nil {
+		session.UserAgent = *userAgent
+	}
+	if ipAddress != nil {
+		session.IPAddress = *ipAddress
+	}
+
+	return &session, nil
+}
+
+// Delete removes a session by its token.
+func (r *SessionRepository) Delete(token string) error {
+	ctx := context.Background()
+
+	query := `DELETE FROM sessions WHERE token = $1`
+	_, err := r.pool.Exec(ctx, query, token)
+	if err != nil {
+		return fmt.Errorf("deleting session: %w", err)
+	}
+
+	return nil
+}
+
+// DeleteByUserID removes all sessions for a user.
+func (r *SessionRepository) DeleteByUserID(userID uuid.UUID) error {
+	ctx := context.Background()
+
+	query := `DELETE FROM sessions WHERE user_id = $1`
+	_, err := r.pool.Exec(ctx, query, userID)
+	if err != nil {
+		return fmt.Errorf("deleting user sessions: %w", err)
+	}
+
+	return nil
+}
+
+// DeleteExpired removes all expired sessions.
+func (r *SessionRepository) DeleteExpired() (int64, error) {
+	ctx := context.Background()
+
+	query := `DELETE FROM sessions WHERE expires_at < NOW()`
+	result, err := r.pool.Exec(ctx, query)
+	if err != nil {
+		return 0, fmt.Errorf("deleting expired sessions: %w", err)
+	}
+
+	return result.RowsAffected(), nil
+}

internal/service/auth.go

@@ -3,10 +3,12 @@ package service
 
 import (
 	"crypto/rand"
+	"crypto/subtle"
 	"encoding/base64"
 	"errors"
 	"fmt"
 	"regexp"
+	"strings"
 	"time"
 
 	"github.com/google/uuid"
@@ -25,21 +27,27 @@ var (
 
 // Argon2 parameters (OWASP recommended)
 const (
-	argon2Time    = 1
-	argon2Memory  = 64 * 1024 // 64MB
-	argon2Threads = 4
-	argon2KeyLen  = 32
-	saltLength    = 16
+	argon2Time      = 1
+	argon2Memory    = 64 * 1024 // 64MB
+	argon2Threads   = 4
+	argon2KeyLen    = 32
+	saltLength      = 16
+	tokenLength     = 32
+	sessionDuration = 7 * 24 * time.Hour // 7 days
 )
 
 // AuthService handles user authentication business logic.
 type AuthService struct {
-	userRepo domain.UserRepository
+	userRepo    domain.UserRepository
+	sessionRepo domain.SessionRepository
 }
 
 // NewAuthService creates a new authentication service.
-func NewAuthService(userRepo domain.UserRepository) *AuthService {
-	return &AuthService{userRepo: userRepo}
+func NewAuthService(userRepo domain.UserRepository, sessionRepo domain.SessionRepository) *AuthService {
+	return &AuthService{
+		userRepo:    userRepo,
+		sessionRepo: sessionRepo,
+	}
 }
 
 // RegisterRequest contains the data needed to register a new user.
@@ -55,6 +63,28 @@ type RegisterResponse struct {
 	CreatedAt time.Time `json:"created_at"`
 }
 
+// LoginRequest contains the data needed to log in.
+type LoginRequest struct {
+	Email     string `json:"email"`
+	Password  string `json:"password"`
+	UserAgent string `json:"-"`
+	IPAddress string `json:"-"`
+}
+
+// LoginResponse contains the session token.
+type LoginResponse struct {
+	Token     string    `json:"token"`
+	ExpiresAt time.Time `json:"expires_at"`
+	User      UserInfo  `json:"user"`
+}
+
+// UserInfo contains basic user information.
+type UserInfo struct {
+	ID      uuid.UUID `json:"id"`
+	Email   string    `json:"email"`
+	IsAdmin bool      `json:"is_admin"`
+}
+
 // Register creates a new user account.
 func (s *AuthService) Register(req RegisterRequest) (*RegisterResponse, error) {
 	// Validate email format
@@ -104,6 +134,78 @@ func (s *AuthService) Register(req RegisterRequest) (*RegisterResponse, error) {
 	}, nil
 }
 
+// Login authenticates a user and creates a session.
+func (s *AuthService) Login(req LoginRequest) (*LoginResponse, error) {
+	// Find user by email
+	user, err := s.userRepo.GetByEmail(req.Email)
+	if err != nil {
+		return nil, fmt.Errorf("finding user: %w", err)
+	}
+	if user == nil {
+		return nil, ErrInvalidCredentials
+	}
+
+	// Verify password
+	if !verifyPassword(req.Password, user.PasswordHash) {
+		return nil, ErrInvalidCredentials
+	}
+
+	// Generate session token
+	token, err := generateToken()
+	if err != nil {
+		return nil, fmt.Errorf("generating token: %w", err)
+	}
+
+	// Create session
+	now := time.Now()
+	session := &domain.Session{
+		ID:        uuid.New(),
+		UserID:    user.ID,
+		Token:     token,
+		ExpiresAt: now.Add(sessionDuration),
+		CreatedAt: now,
+		UserAgent: req.UserAgent,
+		IPAddress: req.IPAddress,
+	}
+
+	if err := s.sessionRepo.Create(session); err != nil {
+		return nil, fmt.Errorf("creating session: %w", err)
+	}
+
+	return &LoginResponse{
+		Token:     token,
+		ExpiresAt: session.ExpiresAt,
+		User: UserInfo{
+			ID:      user.ID,
+			Email:   user.Email,
+			IsAdmin: user.IsAdmin,
+		},
+	}, nil
+}
+
+// Logout invalidates a session.
+func (s *AuthService) Logout(token string) error {
+	return s.sessionRepo.Delete(token)
+}
+
+// GetUserByToken retrieves the user associated with a session token.
+func (s *AuthService) GetUserByToken(token string) (*domain.User, error) {
+	session, err := s.sessionRepo.GetByToken(token)
+	if err != nil {
+		return nil, fmt.Errorf("getting session: %w", err)
+	}
+	if session == nil {
+		return nil, nil // Invalid or expired session
+	}
+
+	user, err := s.userRepo.GetByID(session.UserID)
+	if err != nil {
+		return nil, fmt.Errorf("getting user: %w", err)
+	}
+
+	return user, nil
+}
+
 // hashPassword creates an Argon2id hash of the password.
 func hashPassword(password string) (string, error) {
 	salt := make([]byte, saltLength)
@@ -126,6 +228,47 @@ func hashPassword(password string) (string, error) {
 	return encoded, nil
 }
 
+// verifyPassword checks if the password matches the hash.
+func verifyPassword(password, encodedHash string) bool {
+	// Parse the encoded hash
+	parts := strings.Split(encodedHash, "$")
+	if len(parts) != 6 {
+		return false
+	}
+
+	var memory, time uint32
+	var threads uint8
+	_, err := fmt.Sscanf(parts[3], "m=%d,t=%d,p=%d", &memory, &time, &threads)
+	if err != nil {
+		return false
+	}
+
+	salt, err := base64.RawStdEncoding.DecodeString(parts[4])
+	if err != nil {
+		return false
+	}
+
+	expectedHash, err := base64.RawStdEncoding.DecodeString(parts[5])
+	if err != nil {
+		return false
+	}
+
+	// Compute hash with same parameters
+	computedHash := argon2.IDKey([]byte(password), salt, time, memory, threads, uint32(len(expectedHash)))
+
+	// Constant-time comparison
+	return subtle.ConstantTimeCompare(expectedHash, computedHash) == 1
+}
+
+// generateToken creates a cryptographically secure random token.
+func generateToken() (string, error) {
+	bytes := make([]byte, tokenLength)
+	if _, err := rand.Read(bytes); err != nil {
+		return "", err
+	}
+	return base64.URLEncoding.EncodeToString(bytes), nil
+}
+
 // isValidEmail checks if the email has a valid format.
 func isValidEmail(email string) bool {
 	emailRegex := regexp.MustCompile(`^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$`)

migrations/002_create_sessions.down.sql

@@ -0,0 +1,3 @@
+-- Rollback: 002_create_sessions
+
+DROP TABLE IF EXISTS sessions;

migrations/002_create_sessions.up.sql

@@ -0,0 +1,21 @@
+-- Migration: 002_create_sessions
+-- Description: Create the sessions table for stateful authentication
+
+CREATE TABLE IF NOT EXISTS sessions (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    token VARCHAR(64) NOT NULL UNIQUE,
+    expires_at TIMESTAMPTZ NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    user_agent TEXT,
+    ip_address VARCHAR(45)
+);
+
+-- Index for token lookup (authentication)
+CREATE INDEX IF NOT EXISTS idx_sessions_token ON sessions(token);
+
+-- Index for user_id (session cleanup)
+CREATE INDEX IF NOT EXISTS idx_sessions_user_id ON sessions(user_id);
+
+-- Index for expiration cleanup
+CREATE INDEX IF NOT EXISTS idx_sessions_expires_at ON sessions(expires_at);