wk2: account management tooling

src/account-manager/go.mod

@@ -0,0 +1,3 @@
+module jupiter-mail.org/account-manager
+
+go 1.23

src/account-manager/main.go

@@ -0,0 +1,136 @@
+package main
+
+import (
+	_ "embed"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"os/exec"
+	"path"
+	"strings"
+
+	"jupiter-mail.org/account-manager/model"
+)
+
+//go:embed res/help.txt
+var helpText string
+
+var USERDB_PATH = path.Clean("/etc/dovecot/userdb")
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Fprintln(os.Stderr, helpText)
+		os.Exit(1)
+	}
+
+	switch os.Args[1] {
+	case "create":
+		account, err := createAccount(os.Args[2], os.Args[3])
+		if err != nil {
+			log.Fatalf("Failed to create account: %v", err)
+			os.Exit(1)
+		}
+		log.Printf("Account \"%s\" created successfully.", account.FullUsername())
+	case "list":
+		log.Fatalf("list: not implemented")
+		os.Exit(1)
+	case "update":
+		log.Fatalf("update: not implemented")
+		os.Exit(1)
+	case "delete":
+		log.Fatalf("delete: not implemented")
+		os.Exit(1)
+	default:
+		log.Fatalf("Unrecognised action \"%s\"", os.Args[1])
+		os.Exit(1)
+	}
+}
+
+func openUserDB() (*os.File, error) {
+	err := os.MkdirAll(path.Dir(USERDB_PATH), 0755)
+	if err != nil { return nil, err }
+
+	file, err := os.OpenFile(USERDB_PATH, os.O_CREATE | os.O_RDWR, 0640)
+	if err != nil && errors.Is(err, os.ErrExist) { return nil, err }
+
+	return file, nil
+}
+
+func getMailHome(user string, domain string) string {
+	return fmt.Sprintf("/var/mail/%s/%s/home", domain, user)
+}
+
+func checkAccountExists(username string) (bool, error) {
+	file, err := openUserDB()
+	if err != nil { return false, fmt.Errorf("open userdb: %v", err)  }
+
+	data, err := io.ReadAll(file)
+	if err != nil { return false, fmt.Errorf("read userdb: %v", err)  }
+	file.Close()
+
+	lines := strings.Split(string(data), "\n")
+	for _, line := range lines {
+		if strings.HasPrefix(line, username) { return true, nil }
+	}
+
+	return false, nil
+}
+
+func createAccount(fullUsername string, password string) (*model.MailAccount, error) {
+	exists, err := checkAccountExists(fullUsername)
+	if err != nil { return nil, fmt.Errorf("failed to check if account exists: %v", err)  }
+	if exists { return nil, fmt.Errorf("account already exists: %s", fullUsername) }
+
+	usernameSplits := strings.Split(fullUsername, "@")
+	if len(usernameSplits) != 2 {
+		return nil, fmt.Errorf("invalid email format: %s", fullUsername)
+	}
+	username := usernameSplits[0]
+	domain := usernameSplits[1]
+
+	passwordHash, err := hashPassword(username, password)
+	if err != nil { return nil, fmt.Errorf("hash password: %v", err) }
+
+	account := model.NewMailAccount(username, domain, []byte(passwordHash))
+
+	uid := 5000; gid := 5000
+	// <username>:<password>:5000:5000::/var/mail/<domain>/<user>/home::
+	userDbLine := fmt.Sprintf(
+		"%s:%s:%d:%d::%s::\n",
+		account.FullUsername(),
+		account.PasswordHash,
+		uid, gid,
+		getMailHome(account.Username, account.Domain),
+	)
+
+	file, err := openUserDB()
+	if err != nil { return nil, fmt.Errorf("open userdb: %v", err) }
+	buf := make([]byte, 1024)
+	for n, err := file.Read(buf); n > 0; {
+		if err != nil {
+			return nil, fmt.Errorf("read userdb: %v", err)
+		}
+	}
+	_, err = file.Write([]byte(userDbLine))
+	if err != nil { return nil, err }
+
+	err = file.Close()
+	if err != nil { return nil, err }
+
+	return &account, nil
+}
+
+func hashPassword(username string, password string) (string, error) {
+	// doveadm pw -s SHA512-CRYPT -u "$USERNAME" -p "$PASSWORD"
+	hashCmd := exec.Command(
+		"doveadm", "pw",
+		"-s", "SHA512-CRYPT",
+		"-u", username,
+		"-p", password,
+	)
+	out, err := hashCmd.Output()
+	if err != nil { return "", err }
+	return string(out), nil
+}

src/account-manager/model/account.go

@@ -0,0 +1,23 @@
+package model
+
+import "fmt"
+
+type (
+	MailAccount struct {
+		Username		string `json:"username"`
+		Domain			string `json:"domain"`
+		PasswordHash	[]byte `json:"password"`
+	}
+)
+
+func NewMailAccount(username string, domain string, passwordHash []byte) MailAccount {
+	return MailAccount{
+		Username: username,
+		Domain: domain,
+		PasswordHash: passwordHash,
+	}
+}
+
+func (account *MailAccount) FullUsername() string {
+	return fmt.Sprintf("%s@%s", account.Username, account.Domain)
+}

src/account-manager/res/help.txt

@@ -0,0 +1,7 @@
+usage: accounts <action> [...opts]
+
+actions:
+    create <username> <password>
+    list
+    update <username> <password>
+    delete <username>