WIP: Email verification

mail/mail.go

@@ -0,0 +1,126 @@
+package mail
+
+import (
+	"crypto/rand"
+	"fmt"
+	"math/big"
+	"mime"
+	"net"
+	"net/smtp"
+	"strings"
+	"sync"
+	"time"
+
+	"heckel.io/ntfy/v2/log"
+)
+
+const (
+	verifyCodeExpiry  = 10 * time.Minute
+	verifyCodeLength  = 6
+	verifyCodeSubject = "ntfy email verification"
+)
+
+// Config holds the SMTP configuration for the mail sender
+type Config struct {
+	SMTPAddr string // SMTP server address (host:port)
+	SMTPUser string // SMTP auth username
+	SMTPPass string // SMTP auth password
+	From     string // Sender email address
+}
+
+// Sender sends emails and manages email verification codes
+type Sender struct {
+	config      *Config
+	verifyCodes map[string]verifyCode // keyed by email
+	mu          sync.Mutex
+}
+
+type verifyCode struct {
+	code    string
+	expires time.Time
+}
+
+// NewSender creates a new mail Sender with the given SMTP config
+func NewSender(config *Config) *Sender {
+	return &Sender{
+		config:      config,
+		verifyCodes: make(map[string]verifyCode),
+	}
+}
+
+// Send sends a plain text email via SMTP
+func (s *Sender) Send(to, subject, body string) error {
+	host, _, err := net.SplitHostPort(s.config.SMTPAddr)
+	if err != nil {
+		return err
+	}
+	var auth smtp.Auth
+	if s.config.SMTPUser != "" {
+		auth = smtp.PlainAuth("", s.config.SMTPUser, s.config.SMTPPass, host)
+	}
+	date := time.Now().UTC().Format(time.RFC1123Z)
+	encodedSubject := mime.BEncoding.Encode("utf-8", subject)
+	message := `From: ntfy <{from}>
+To: {to}
+Date: {date}
+Subject: {subject}
+Content-Type: text/plain; charset="utf-8"
+
+{body}`
+	message = strings.ReplaceAll(message, "{from}", s.config.From)
+	message = strings.ReplaceAll(message, "{to}", to)
+	message = strings.ReplaceAll(message, "{date}", date)
+	message = strings.ReplaceAll(message, "{subject}", encodedSubject)
+	message = strings.ReplaceAll(message, "{body}", body)
+	log.Tag("mail").Field("email_to", to).Debug("Sending email")
+	return smtp.SendMail(s.config.SMTPAddr, auth, s.config.From, []string{to}, []byte(message))
+}
+
+// SendVerification generates a 6-digit code, stores it in-memory, and sends a verification email
+func (s *Sender) SendVerification(to string) error {
+	code, err := generateCode()
+	if err != nil {
+		return err
+	}
+	s.mu.Lock()
+	s.verifyCodes[to] = verifyCode{
+		code:    code,
+		expires: time.Now().Add(verifyCodeExpiry),
+	}
+	s.mu.Unlock()
+	body := fmt.Sprintf("Your ntfy email verification code is: %s\n\nThis code expires in 10 minutes.", code)
+	return s.Send(to, verifyCodeSubject, body)
+}
+
+// CheckVerification checks if the code matches and hasn't expired. Removes the entry on success.
+func (s *Sender) CheckVerification(email, code string) bool {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	vc, ok := s.verifyCodes[email]
+	if !ok || time.Now().After(vc.expires) || vc.code != code {
+		return false
+	}
+	delete(s.verifyCodes, email)
+	return true
+}
+
+// ExpireVerificationCodes removes expired entries from the in-memory map
+func (s *Sender) ExpireVerificationCodes() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	now := time.Now()
+	for email, vc := range s.verifyCodes {
+		if now.After(vc.expires) {
+			delete(s.verifyCodes, email)
+		}
+	}
+}
+
+func generateCode() (string, error) {
+	max := big.NewInt(1000000) // 0-999999
+	n, err := rand.Int(rand.Reader, max)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%06d", n.Int64()), nil
+}