change password file directly

main.go

@@ -1,11 +1,13 @@
 package main
 
 import (
+	"crypto"
+	"fmt"
 	"log"
 	"net/http"
 	"os"
-	"os/exec"
 	"path"
+	"strings"
 	"text/template"
 	"time"
 
@@ -123,9 +125,8 @@ func main() {
 			tmpl.Execute(w, d)
 			return
 		}
-		cm := exec.Command("/root/docker/mail/setup.sh", "email", "update", f.GetValue("email"), f.GetValue("newpassword"))
-		err = cm.Run()
-		if err != nil {
+		// Change the password
+		if !modifyPasswordFile(f.GetValue("email"), f.GetValue("newpassword")) {
 			log.Println(err)
 			d.Body = "Internal error"
 			tmpl.Execute(w, d)
@@ -139,3 +140,47 @@ func main() {
 	tmpl.Execute(os.Stdout, d)
 	http.ListenAndServe("127.0.0.1:8910", r)
 }
+
+/*
+example password entry:
+recreation@pinnaclelake.com|{SHA512-CRYPT}$6$uTiy7Q5xn1CIN22w$3VAElns3TFfejtdTCTJMcz8k2UPPwAmlUIoXC4NgPJRnDcgo3CnI91EsB6irgwuecCrolxAx7i4mjvTxPaAlf0
+
+*/
+
+// createPasswordEntry: input email and plain text password, output a password entry with sha512-crypt.
+
+func modifyPasswordFile(email, password string) bool {
+	// read the password file
+	// find the entry with the given email
+	// replace the password with the new password
+	// write the file back
+	in, err := os.ReadFile("/root/docker/mail/config/postfix-accounts")
+	if err != nil {
+		log.Println(err)
+		return false
+	}
+	out, err := os.Create("/root/docker/mail/config/postfix-accounts.tmp")
+	if err != nil {
+		log.Println(err)
+		return false
+	}
+
+	lines := strings.Split(string(in), "\n")
+	for _, line := range lines {
+		if strings.HasPrefix(line, email) {
+			line = createPasswordEntry(email, password)
+		}
+		out.WriteString(line)
+		out.WriteString("\n")
+	}
+	out.Close()
+	os.Rename("/root/docker/mail/config/postfix-accounts.tmp", "/root/docker/mail/config/postfix-accounts")
+	return true
+}
+
+func createPasswordEntry(email, password string) string {
+	c := crypto.SHA512.New()
+	c.Write([]byte(password))
+	hash := c.Sum(nil)
+	return fmt.Sprintf("%s|{SHA512-CRYPT}$6$%s", email, hash)
+}