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send_email.go
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send_email.go
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package uadmin
import (
"encoding/base64"
"fmt"
"mime"
"net/smtp"
"os"
"path/filepath"
"strings"
"time"
"unicode/utf8"
)
// SendEmail sends email using system configured variables
func SendEmail(to, cc, bcc []string, subject, body string, attachments ...string) (err error) {
if CustomEmailHandler != nil {
attachmentsPointers := make([]*string, len(attachments))
for i := range attachments {
attachmentsPointers[i] = &attachments[i]
}
var proceed bool
proceed, err = CustomEmailHandler(&to, &cc, &bcc, &subject, &body, attachmentsPointers...)
if err != nil {
Trail(ERROR, "Error in CustomEmailHandler. %s", err)
}
if !proceed {
return
}
}
if EmailFrom == "" || EmailUsername == "" || EmailPassword == "" || EmailSMTPServer == "" || EmailSMTPServerPort == 0 {
errMsg := "Email not sent because email global variables are not set"
Trail(WARNING, errMsg)
return fmt.Errorf(errMsg)
}
// Get the domain name of sender
domain := strings.Split(EmailFrom, "@")
if len(domain) < 2 {
return
}
domain[0] = strings.TrimSpace(domain[0])
domain[0] = strings.TrimSuffix(domain[0], ">")
// prepare body by splitting it into lines of length 73 followed by =
body = strings.ReplaceAll(body, "\n", "<br/>")
body = strings.ReplaceAll(body, "=", "=3D")
body = strings.Join(splitString(body, 73), "=\r\n")
// Construct the email
MIME := "MIME-version: 1.0;\r\nContent-Type: text/html; charset=\"utf-8\";\r\nContent-Transfer-Encoding: quoted-printable\r\n"
delimeter := fmt.Sprintf("--=_uAdmin_%s_%s.%s", GenerateBase32(3), GenerateBase32(9), GenerateBase32(10))
if len(attachments) != 0 {
MIME = "MIME-version: 1.0;\r\n"
MIME += fmt.Sprintf("Content-Type: multipart/mixed; boundary=\"%s\"\r\nContent-Transfer-Encoding: quoted-printable\r\n", delimeter)
body = "\r\n--" + delimeter + "\r\n" + fmt.Sprintf("Content-Type: text/html; boundary=\"%s\"\r\nContent-Transfer-Encoding: quoted-printable\r\n\r\n", delimeter) + body
for i := range attachments {
// get filename
filename := filepath.Base(attachments[i])
// read the file
rawFile, err := os.ReadFile(attachments[i])
if err != nil {
Trail(WARNING, "Unable to attach file %s. %s", attachments[i], err)
continue
}
body += "\r\n\r\n--" + delimeter + "\r\n"
body += fmt.Sprintf("Content-Type: "+getMimeFromFileName(filename)+"; boundary=\"%s\"\r\n", delimeter)
body += "Content-Transfer-Encoding: base64\r\n"
body += "Content-Disposition: attachment;filename=\"" + filename + "\"\r\n"
body += "Content-Transfer-Encoding: quoted-printable\r\n"
body += "\r\n" + strings.Join(splitString(base64.StdEncoding.EncodeToString(rawFile), 73), "\r\n")
}
}
msg := "From: " + EmailFrom + "\r\n"
msg += "To: " + strings.Join(to, ",") + "\r\n"
if len(cc) > 0 {
msg += "CC: " + strings.Join(cc, ",") + "\r\n"
}
msg += "Date: " + time.Now().UTC().Format(time.RFC1123Z) + "\r\n"
msg += "Message-ID: " + fmt.Sprintf("<%s-%s-%s-%s-%s@%s>", GenerateBase32(8), GenerateBase32(4), GenerateBase32(4), GenerateBase32(4), GenerateBase32(12), domain[0]) + "\r\n"
msg += "Subject: " + subject + "\r\n"
msg += MIME + "\r\n"
msg += body
msg += "\r\n\r\n"
// Append CC and BCC
if cc != nil {
to = append(to, cc...)
}
if bcc != nil {
to = append(to, bcc...)
}
go func() {
err = smtp.SendMail(fmt.Sprintf("%s:%d", EmailSMTPServer, EmailSMTPServerPort),
smtp.PlainAuth(EmailFrom, EmailUsername, EmailPassword, EmailSMTPServer),
EmailFrom, to, []byte(msg))
if err != nil {
Trail(WARNING, "Email was not sent. %s", err)
}
}()
return nil
}
func splitString(v string, maxLen int) []string {
splits := []string{}
var l, r int
for l, r = 0, maxLen; r < len(v); l, r = r, r+maxLen {
for !utf8.RuneStart(v[r]) {
r--
}
splits = append(splits, v[l:r])
}
splits = append(splits, v[l:])
return splits
}
func getMimeFromFileName(v string) string {
ext := filepath.Ext(v)
mType := mime.TypeByExtension(ext)
if mType == "" {
return "application/octet-stream"
}
return mType
}