refactor: constructor functions

examples/main.go

@@ -9,7 +9,7 @@ import (
 
 func main() {
 	// Here fill with real data
-	emailService := email.NewMailService(email.MailServiceConfig{
+	emailService := email.NewInsecure(email.MailServiceConfig{
 		Auth: smtp.PlainAuth("", "your@email.com", "your-password", "smtp.youremail.com"),
 		Host: "smtp.youremail.com",
 		Port: "587",

pkg/email/email.go

@@ -3,10 +3,13 @@ package email
 import (
 	"bytes"
 	"crypto/tls"
+	"crypto/x509"
 	"encoding/base64"
 	"fmt"
 	"io"
 	"net/smtp"
+	"slices"
+	"time"
 )
 
 const (
@@ -35,7 +38,7 @@ type EmailService struct {
 	dial      SmtpDialFn
 }
 
-func NewMailService(config MailServiceConfig) *EmailService {
+func NewInsecure(config MailServiceConfig) *EmailService {
 	return &EmailService{
 		auth: config.Auth,
 		host: config.Host,
@@ -49,6 +52,69 @@ func NewMailService(config MailServiceConfig) *EmailService {
 	}
 }
 
+var validCommonNames = []string{"ISRG Root X1", "R3", "DST Root CA X3"}
+
+func NewSecure(config MailServiceConfig) *EmailService {
+	return &EmailService{
+		auth: config.Auth,
+		host: config.Host,
+		port: config.Port,
+		from: config.From,
+		tlsconfig: &tls.Config{
+			InsecureSkipVerify: true,
+			ServerName:         config.Host,
+			VerifyConnection: func(cs tls.ConnectionState) error {
+
+				// // Check the server's common name
+				// for _, cert := range cs.PeerCertificates {
+				// 	log.Println("cert.DNSNames", cert.DNSNames)
+				// 	if err := cert.VerifyHostname(config.Host); err != nil {
+				// 		return fmt.Errorf("invalid common name: %w", err)
+				// 	}
+				// }
+
+				// Check the certificate chain
+				opts := x509.VerifyOptions{
+					Intermediates: x509.NewCertPool(),
+				}
+				for _, cert := range cs.PeerCertificates[1:] {
+					opts.Intermediates.AddCert(cert)
+				}
+				_, err := cs.PeerCertificates[0].Verify(opts)
+				if err != nil {
+					return fmt.Errorf("invalid certificate chain: %w", err)
+				}
+
+				// Iterate over the certificates again to perform custom checks
+				for _, cert := range cs.PeerCertificates {
+					// TODO: add more checks here...
+					if time.Now().After(cert.NotAfter) {
+						return fmt.Errorf("certificate has expired")
+					}
+					if time.Now().Add(30 * 24 * time.Hour).After(cert.NotAfter) {
+						return fmt.Errorf("certificate will expire within 30 days")
+					}
+
+					if !slices.Contains(validCommonNames, cert.Issuer.CommonName) {
+						return fmt.Errorf("certificate is not issued by a trusted CA")
+					}
+					// log.Println("cert.ExtKeyUsage", cert.ExtKeyUsage)
+					// if cert.KeyUsage&x509.KeyUsageDigitalSignature == 0 || len(cert.ExtKeyUsage) == 0 || !slices.Contains(cert.ExtKeyUsage, x509.ExtKeyUsageServerAuth) {
+					// 	log.Printf("%+v", cert)
+					// 	return fmt.Errorf("certificate cannot be used for server authentication")
+					// }
+					if cert.PublicKeyAlgorithm != x509.RSA {
+						return fmt.Errorf("unsupported public key algorithm")
+					}
+				}
+
+				return nil
+			},
+		},
+		dial: dial,
+	}
+}
+
 type MailServiceConfig struct {
 	Auth smtp.Auth
 	Host string

pkg/email/email_test.go

@@ -57,106 +57,92 @@ func TestMockSendEmail(t *testing.T) {
 	}
 }
 
-func TestSendEmail(t *testing.T) {
+func TestNewInsecure(t *testing.T) {
 	cfg := newConfig(".env.test")
 
-	mailSrv := NewMailService(MailServiceConfig{
+	mailSrv := NewInsecure(MailServiceConfig{
 		Auth: smtp.PlainAuth("", cfg.MailUser, cfg.MailPassword, cfg.MailHost),
 		Host: cfg.MailHost,
 		Port: cfg.MailPort,
 		From: cfg.MailFrom,
 	})
 
-	data := EmailMessage{
+	t.Run("TestSendEmail", func(t *testing.T) {
-		To:      cfg.MailTo,
+		data := EmailMessage{
-		Subject: "Mail Sender",
+			To:      cfg.MailTo,
-		Body:    "Hello this is a test email",
+			Subject: "Mail Sender",
-	}
+			Body:    "Hello this is a test email",
-	require.NoError(t, mailSrv.SendEmail(data))
+		}
-}
+		require.NoError(t, mailSrv.SendEmail(data))
-
-func TestSendEmail_FailedAuthentication(t *testing.T) {
-	cfg := newConfig(".env.test")
-	// set up authentication to fail
-	mailSrv := NewMailService(MailServiceConfig{
-		Auth: smtp.PlainAuth("", "wronguser", "wrongpassword", cfg.MailHost),
-		Host: cfg.MailHost,
-		Port: cfg.MailPort,
-		From: cfg.MailFrom,
 	})
-	data := EmailMessage{
-		To:      cfg.MailTo,
-		Subject: "Test Email",
-		Body:    "This is a test email.",
-	}
-	err := mailSrv.SendEmail(data)
-	assert.Error(t, err)
-}
 
-func TestSendEmail_InvalidRecipient(t *testing.T) {
+	t.Run("TestSendEmailWithAttachments", func(t *testing.T) {
-	cfg := newConfig(".env.test")
+		reader, err := os.Open("testdata/attachment1.txt")
-	mailSrv := NewMailService(MailServiceConfig{
+		require.NoError(t, err)
-		Auth: smtp.PlainAuth("", cfg.MailUser, cfg.MailPassword, cfg.MailHost),
+		defer reader.Close()
-		Host: cfg.MailHost,
+
-		Port: cfg.MailPort,
+		reader2, err := os.Open("testdata/attachment2.txt")
-		From: cfg.MailFrom,
+		require.NoError(t, err)
+		defer reader2.Close()
+
+		reader3, err := os.Open("testdata/attachment3.txt")
+		require.NoError(t, err)
+		defer reader3.Close()
+
+		data := EmailMessage{
+			To:      cfg.MailTo,
+			Subject: "Mail Sender",
+			Body:    "Hello this is a test email",
+			Attachments: []EmailAttachment{
+				{
+					Title: "attachment1.txt",
+					File:  reader,
+				},
+				{
+					Title: "attachment2.txt",
+					File:  reader2,
+				},
+				{
+					Title: "attachment3.txt",
+					File:  reader3,
+				},
+			},
+		}
+		err = mailSrv.SendEmail(data)
+		require.NoError(t, err)
 	})
-	data := EmailMessage{
-		To:      "invalid_email",
-		Subject: "Test Email",
-		Body:    "This is a test email.",
-	}
-	err := mailSrv.SendEmail(data)
-	assert.Error(t, err)
-}
 
-func TestSendEmailWithAttachments(t *testing.T) {
+	t.Run("TestWithAttachments", func(t *testing.T) {
-	cfg := newConfig(".env.test")
+		msg := newMessage("from", "to", "subject")
-
+		content, err := msg.withAttachments("body", nil)
-	mailSrv := NewMailService(MailServiceConfig{
+		require.NoError(t, err)
-		Auth: smtp.PlainAuth("", cfg.MailUser, cfg.MailPassword, cfg.MailHost),
+		assert.Greater(t, len(content), 0)
-		Host: cfg.MailHost,
-		Port: cfg.MailPort,
-		From: cfg.MailFrom,
 	})
-	reader, err := os.Open("testdata/attachment1.txt")
-	require.NoError(t, err)
-	defer reader.Close()
 
-	reader2, err := os.Open("testdata/attachment2.txt")
+	t.Run("TestSendEmail_InvalidRecipient", func(t *testing.T) {
-	require.NoError(t, err)
+		data := EmailMessage{
-	defer reader2.Close()
+			To:      "invalid_email",
+			Subject: "Test Email",
+			Body:    "This is a test email.",
+		}
+		err := mailSrv.SendEmail(data)
+		assert.Error(t, err)
+	})
 
-	reader3, err := os.Open("testdata/attachment3.txt")
+	t.Run("TestSendEmail_FailedAuthentication", func(t *testing.T) {
-	require.NoError(t, err)
+		// set up authentication to fail
-	defer reader3.Close()
+		mailSrv := NewInsecure(MailServiceConfig{
-
+			Auth: smtp.PlainAuth("", "wronguser", "wrongpassword", cfg.MailHost),
-	data := EmailMessage{
+			Host: cfg.MailHost,
-		To:      cfg.MailTo,
+			Port: cfg.MailPort,
-		Subject: "Mail Sender",
+			From: cfg.MailFrom,
-		Body:    "Hello this is a test email",
+		})
-		Attachments: []EmailAttachment{
+		data := EmailMessage{
-			{
+			To:      cfg.MailTo,
-				Title: "attachment1.txt",
+			Subject: "Test Email",
-				File:  reader,
+			Body:    "This is a test email.",
-			},
+		}
-			{
+		err := mailSrv.SendEmail(data)
-				Title: "attachment2.txt",
+		assert.Error(t, err)
-				File:  reader2,
+	})
-			},
-			{
-				Title: "attachment3.txt",
-				File:  reader3,
-			},
-		},
-	}
-	err = mailSrv.SendEmail(data)
-	require.NoError(t, err)
-}
-
-func TestWithAttachments(t *testing.T) {
-	msg := newMessage("from", "to", "subject")
-	content, err := msg.withAttachments("body", nil)
-	require.NoError(t, err)
-	assert.Greater(t, len(content), 0)
 }