[bug] Send plaintext emails to fix "message refused: Message is not RFC 2822 compliant" (#366)

* trying to fix "message refused: Message is not RFC 2822 compliant"

* fix "message refused: Message is not RFC 2822 compliant"

550 5.7.1 Delivery not authorized, message refused: Message is not RFC
2822 compliant

* remove silly regex

* lint

* fix tests

* we should use text/template instead of html/template now

11 files changed, 78 insertions, 28 deletions

diff --git a/internal/email/confirm.go b/internal/email/confirm.go
index 4503137b3..34e2fb660 100644
--- a/internal/email/confirm.go
+++ b/internal/email/confirm.go
@@ -21,11 +21,15 @@ package email
 import (
 	"bytes"
 	"net/smtp"
+
+	"github.com/sirupsen/logrus"
+	"github.com/spf13/viper"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
 )
 
 const (
-	confirmTemplate = "email_confirm.tmpl"
-	confirmSubject  = "Subject: GoToSocial Email Confirmation"
+	confirmTemplate = "email_confirm_text.tmpl"
+	confirmSubject  = "GoToSocial Email Confirmation"
 )
 
 func (s *sender) SendConfirmEmail(toAddress string, data ConfirmData) error {
@@ -35,7 +39,11 @@ func (s *sender) SendConfirmEmail(toAddress string, data ConfirmData) error {
 	}
 	confirmBody := buf.String()
 
-	msg := assembleMessage(confirmSubject, confirmBody, toAddress, s.from)
+	msg, err := assembleMessage(confirmSubject, confirmBody, toAddress, s.from)
+	if err != nil {
+		return err
+	}
+	logrus.WithField("func", "SendConfirmEmail").Trace(s.hostAddress + "\n" + viper.GetString(config.Keys.SMTPUsername) + ":password" + "\n" + s.from + "\n" + toAddress + "\n\n" + string(msg) + "\n")
 	return smtp.SendMail(s.hostAddress, s.auth, s.from, []string{toAddress}, msg)
 }
 
diff --git a/internal/email/noopsender.go b/internal/email/noopsender.go
index efec303f0..9f587f319 100644
--- a/internal/email/noopsender.go
+++ b/internal/email/noopsender.go
@@ -20,7 +20,7 @@ package email
 
 import (
 	"bytes"
-	"html/template"
+	"text/template"
 
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/viper"
@@ -57,7 +57,10 @@ func (s *noopSender) SendConfirmEmail(toAddress string, data ConfirmData) error
 	}
 	confirmBody := buf.String()
 
-	msg := assembleMessage(confirmSubject, confirmBody, toAddress, "test@example.org")
+	msg, err := assembleMessage(confirmSubject, confirmBody, toAddress, "test@example.org")
+	if err != nil {
+		return err
+	}
 
 	logrus.Tracef("NOT SENDING confirmation email to %s with contents: %s", toAddress, msg)
 
@@ -74,7 +77,10 @@ func (s *noopSender) SendResetEmail(toAddress string, data ResetData) error {
 	}
 	resetBody := buf.String()
 
-	msg := assembleMessage(resetSubject, resetBody, toAddress, "test@example.org")
+	msg, err := assembleMessage(resetSubject, resetBody, toAddress, "test@example.org")
+	if err != nil {
+		return err
+	}
 
 	logrus.Tracef("NOT SENDING reset email to %s with contents: %s", toAddress, msg)
 
diff --git a/internal/email/reset.go b/internal/email/reset.go
index 7a08ebda9..b646ef99b 100644
--- a/internal/email/reset.go
+++ b/internal/email/reset.go
@@ -24,8 +24,8 @@ import (
 )
 
 const (
-	resetTemplate = "email_reset.tmpl"
-	resetSubject  = "Subject: GoToSocial Password Reset"
+	resetTemplate = "email_reset_text.tmpl"
+	resetSubject  = "GoToSocial Password Reset"
 )
 
 func (s *sender) SendResetEmail(toAddress string, data ResetData) error {
@@ -35,7 +35,10 @@ func (s *sender) SendResetEmail(toAddress string, data ResetData) error {
 	}
 	resetBody := buf.String()
 
-	msg := assembleMessage(resetSubject, resetBody, toAddress, s.from)
+	msg, err := assembleMessage(resetSubject, resetBody, toAddress, s.from)
+	if err != nil {
+		return err
+	}
 	return smtp.SendMail(s.hostAddress, s.auth, s.from, []string{toAddress}, msg)
 }
 
diff --git a/internal/email/sender.go b/internal/email/sender.go
index 97bbcd23b..f44627496 100644
--- a/internal/email/sender.go
+++ b/internal/email/sender.go
@@ -20,8 +20,8 @@ package email
 
 import (
 	"fmt"
-	"html/template"
 	"net/smtp"
+	"text/template"
 
 	"github.com/spf13/viper"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
diff --git a/internal/email/util.go b/internal/email/util.go
index db95128fa..52290dbe4 100644
--- a/internal/email/util.go
+++ b/internal/email/util.go
@@ -19,15 +19,12 @@
 package email
 
 import (
+	"errors"
 	"fmt"
-	"html/template"
 	"os"
 	"path/filepath"
-)
-
-const (
-	mime = `MIME-version: 1.0;
-Content-Type: text/html;`
+	"strings"
+	"text/template"
 )
 
 func loadTemplates(templateBaseDir string) (*template.Template, error) {
@@ -41,16 +38,34 @@ func loadTemplates(templateBaseDir string) (*template.Template, error) {
 	return template.ParseGlob(tmPath)
 }
 
-func assembleMessage(mailSubject string, mailBody string, mailTo string, mailFrom string) []byte {
-	from := fmt.Sprintf("From: GoToSocial <%s>", mailFrom)
-	to := fmt.Sprintf("To: %s", mailTo)
+// https://datatracker.ietf.org/doc/html/rfc2822
+// I did not read the RFC, I just copy and pasted from
+// https://pkg.go.dev/net/smtp#SendMail
+// and it did seem to work.
+func assembleMessage(mailSubject string, mailBody string, mailTo string, mailFrom string) ([]byte, error) {
+
+	if strings.Contains(mailSubject, "\r") || strings.Contains(mailSubject, "\n") {
+		return nil, errors.New("email subject must not contain newline characters")
+	}
+
+	if strings.Contains(mailFrom, "\r") || strings.Contains(mailFrom, "\n") {
+		return nil, errors.New("email from address must not contain newline characters")
+	}
+
+	if strings.Contains(mailTo, "\r") || strings.Contains(mailTo, "\n") {
+		return nil, errors.New("email to address must not contain newline characters")
+	}
+
+	// normalize the message body to use CRLF line endings
+	mailBody = strings.ReplaceAll(mailBody, "\r\n", "\n")
+	mailBody = strings.ReplaceAll(mailBody, "\n", "\r\n")
 
 	msg := []byte(
-		mailSubject + "\r\n" +
-			from + "\r\n" +
-			to + "\r\n" +
-			mime + "\r\n" +
-			mailBody + "\r\n")
+		"To: " + mailTo + "\r\n" +
+			"Subject: " + mailSubject + "\r\n" +
+			"\r\n" +
+			mailBody + "\r\n",
+	)
 
-	return msg
+	return msg, nil
 }
diff --git a/internal/email/util_test.go b/internal/email/util_test.go
index b5c7a9852..8895785f7 100644
--- a/internal/email/util_test.go
+++ b/internal/email/util_test.go
@@ -39,7 +39,7 @@ func (suite *UtilTestSuite) TestTemplateConfirm() {
 
 	suite.sender.SendConfirmEmail("user@example.org", confirmData)
 	suite.Len(suite.sentEmails, 1)
-	suite.Equal("Subject: GoToSocial Email Confirmation\r\nFrom: GoToSocial <test@example.org>\r\nTo: user@example.org\r\nMIME-version: 1.0;\nContent-Type: text/html;\r\n<!DOCTYPE html>\n<html>\n    </head>\n    <body>\n        <div>\n            <h1>\n                Hello test!\n            </h1>\n        </div>\n        <div>\n            <p>\n                You are receiving this mail because you've requested an account on <a href=\"https://example.org\">Test Instance</a>.\n            </p>\n            <p>\n                We just need to confirm that this is your email address. To confirm your email, <a href=\"https://example.org/confirm_email?token=ee24f71d-e615-43f9-afae-385c0799b7fa\">click here</a> or paste the following in your browser's address bar:\n            </p>\n            <p>\n                <code>\n                    https://example.org/confirm_email?token=ee24f71d-e615-43f9-afae-385c0799b7fa\n                </code>\n            </p>\n        </div>\n        <div>\n            <p>\n                If you believe you've been sent this email in error, feel free to ignore it, or contact the administrator of <a href=\"https://example.org\">Test Instance</a>.\n            </p>\n        </div>\n    </body>\n</html>\r\n", suite.sentEmails["user@example.org"])
+	suite.Equal("To: user@example.org\r\nSubject: GoToSocial Email Confirmation\r\n\r\nHello test!\r\n\r\nYou are receiving this mail because you've requested an account on https://example.org.\r\n\r\nWe just need to confirm that this is your email address. To confirm your email, paste the following in your browser's address bar:\r\n\r\nhttps://example.org/confirm_email?token=ee24f71d-e615-43f9-afae-385c0799b7fa\r\n\r\nIf you believe you've been sent this email in error, feel free to ignore it, or contact the administrator of https://example.org\r\n\r\n", suite.sentEmails["user@example.org"])
 }
 
 func (suite *UtilTestSuite) TestTemplateReset() {
@@ -52,7 +52,7 @@ func (suite *UtilTestSuite) TestTemplateReset() {
 
 	suite.sender.SendResetEmail("user@example.org", resetData)
 	suite.Len(suite.sentEmails, 1)
-	suite.Equal("Subject: GoToSocial Password Reset\r\nFrom: GoToSocial <test@example.org>\r\nTo: user@example.org\r\nMIME-version: 1.0;\nContent-Type: text/html;\r\n<!DOCTYPE html>\n<html>\n    </head>\n    <body>\n        <div>\n            <h1>\n                Hello test!\n            </h1>\n        </div>\n        <div>\n            <p>\n                You are receiving this mail because a password reset has been requested for your account on <a href=\"https://example.org\">Test Instance</a>.\n            </p>\n            <p>\n                To reset your password, <a href=\"https://example.org/reset_email?token=ee24f71d-e615-43f9-afae-385c0799b7fa\">click here</a> or paste the following in your browser's address bar:\n            </p>\n            <p>\n                <code>\n                    https://example.org/reset_email?token=ee24f71d-e615-43f9-afae-385c0799b7fa\n                </code>\n            </p>\n        </div>\n        <div>\n            <p>\n                If you believe you've been sent this email in error, feel free to ignore it, or contact the administrator of <a href=\"https://example.org\">Test Instance</a>.\n            </p>\n        </div>\n    </body>\n</html>\r\n", suite.sentEmails["user@example.org"])
+	suite.Equal("To: user@example.org\r\nSubject: GoToSocial Password Reset\r\n\r\nHello test!\r\n\r\nYou are receiving this mail because a password reset has been requested for your account on https://example.org.\r\n\r\nTo reset your password, paste the following in your browser's address bar:\r\n\r\nhttps://example.org/reset_email?token=ee24f71d-e615-43f9-afae-385c0799b7fa\r\n\r\nIf you believe you've been sent this email in error, feel free to ignore it, or contact the administrator of https://example.org.\r\n\r\n", suite.sentEmails["user@example.org"])
 }
 
 func TestUtilTestSuite(t *testing.T) {
diff --git a/internal/processing/user/emailconfirm_test.go b/internal/processing/user/emailconfirm_test.go
index 58836d40d..6f22306a1 100644
--- a/internal/processing/user/emailconfirm_test.go
+++ b/internal/processing/user/emailconfirm_test.go
@@ -54,7 +54,7 @@ func (suite *EmailConfirmTestSuite) TestSendConfirmEmail() {
 	suite.NotEmpty(token)
 
 	// email should contain the token
-	emailShould := fmt.Sprintf("Subject: GoToSocial Email Confirmation\r\nFrom: GoToSocial <test@example.org>\r\nTo: some.email@example.org\r\nMIME-version: 1.0;\nContent-Type: text/html;\r\n<!DOCTYPE html>\n<html>\n    </head>\n    <body>\n        <div>\n            <h1>\n                Hello the_mighty_zork!\n            </h1>\n        </div>\n        <div>\n            <p>\n                You are receiving this mail because you've requested an account on <a href=\"http://localhost:8080\">localhost:8080</a>.\n            </p>\n            <p>\n                We just need to confirm that this is your email address. To confirm your email, <a href=\"http://localhost:8080/confirm_email?token=%s\">click here</a> or paste the following in your browser's address bar:\n            </p>\n            <p>\n                <code>\n                    http://localhost:8080/confirm_email?token=%s\n                </code>\n            </p>\n        </div>\n        <div>\n            <p>\n                If you believe you've been sent this email in error, feel free to ignore it, or contact the administrator of <a href=\"http://localhost:8080\">localhost:8080</a>.\n            </p>\n        </div>\n    </body>\n</html>\r\n", token, token)
+	emailShould := fmt.Sprintf("To: some.email@example.org\r\nSubject: GoToSocial Email Confirmation\r\n\r\nHello the_mighty_zork!\r\n\r\nYou are receiving this mail because you've requested an account on http://localhost:8080.\r\n\r\nWe just need to confirm that this is your email address. To confirm your email, paste the following in your browser's address bar:\r\n\r\nhttp://localhost:8080/confirm_email?token=%s\r\n\r\nIf you believe you've been sent this email in error, feel free to ignore it, or contact the administrator of http://localhost:8080\r\n\r\n", token)
 	suite.Equal(emailShould, email)
 
 	// confirmationSentAt should be recent
diff --git a/web/template/email_confirm.tmpl b/web/template/email_confirm_html.tmpl
index 0a9907921..0a9907921 100644
--- a/web/template/email_confirm.tmpl
+++ b/web/template/email_confirm_html.tmpl
diff --git a/web/template/email_confirm_text.tmpl b/web/template/email_confirm_text.tmpl
new file mode 100644
index 000000000..8682cc49c
--- /dev/null
+++ b/web/template/email_confirm_text.tmpl
@@ -0,0 +1,9 @@
+Hello {{.Username}}!
+
+You are receiving this mail because you've requested an account on {{.InstanceURL}}.
+
+We just need to confirm that this is your email address. To confirm your email, paste the following in your browser's address bar:
+
+{{.ConfirmLink}}
+
+If you believe you've been sent this email in error, feel free to ignore it, or contact the administrator of {{.InstanceURL}}
diff --git a/web/template/email_reset.tmpl b/web/template/email_reset_html.tmpl
index 7318c6a45..7318c6a45 100644
--- a/web/template/email_reset.tmpl
+++ b/web/template/email_reset_html.tmpl
diff --git a/web/template/email_reset_text.tmpl b/web/template/email_reset_text.tmpl
new file mode 100644
index 000000000..ccac3bf75
--- /dev/null
+++ b/web/template/email_reset_text.tmpl
@@ -0,0 +1,9 @@
+Hello {{.Username}}!
+
+You are receiving this mail because a password reset has been requested for your account on {{.InstanceURL}}.
+
+To reset your password, paste the following in your browser's address bar:
+
+{{.ResetLink}}
+
+If you believe you've been sent this email in error, feel free to ignore it, or contact the administrator of {{.InstanceURL}}.