Expand allowedUsers email field to support comma-separated and domains (#9)

* Expand allowedUsers email field to support comma-separated and domains

Closes #8

* Refactor AuthFetch() to return AuthUser struct

Also, this breaks out a parseLine() function which can be easily tested.

* Ignore empty addrs after splitting commas

This ignores a trailing comma

* Add tests for auth parseLine()

* Update documentation in smtprelay.ini

* Fix bug where addrAllowed() was incorrectly case-sensitive

* Update allowedUsers allowed domain format to require leading @

This disambiguates a local user ('john.smith') from a domain ('example.com')

auth.go

@@ -13,6 +13,12 @@ var (
 	filename string
 )
 
+type AuthUser struct {
+	username string
+	passwordHash string
+	allowedAddresses []string
+}
+
 func AuthLoadFile(file string) error {
 	f, err := os.Open(file)
 	if err != nil {
@@ -28,50 +34,66 @@ func AuthReady() bool {
 	return (filename != "")
 }
 
-// Returns bcrypt-hash, email
-// email can be empty in which case it is not checked
-func AuthFetch(username string) (string, string, error) {
+// Split a string and ignore empty results
+// https://stackoverflow.com/a/46798310/119527
+func splitstr(s string, sep rune) []string {
+	return strings.FieldsFunc(s, func(c rune) bool { return c == sep })
+}
+
+func parseLine(line string) *AuthUser {
+	parts := strings.Fields(line)
+
+	if len(parts) < 2 || len(parts) > 3 {
+		return nil
+	}
+
+	user := AuthUser{
+		username: parts[0],
+		passwordHash: parts[1],
+		allowedAddresses: nil,
+	}
+
+	if len(parts) >= 3 {
+		user.allowedAddresses = splitstr(parts[2], ',')
+	}
+
+	return &user
+}
+
+func AuthFetch(username string) (*AuthUser, error) {
 	if !AuthReady() {
-		return "", "", errors.New("Authentication file not specified. Call LoadFile() first")
+		return nil, errors.New("Authentication file not specified. Call LoadFile() first")
 	}
 
 	file, err := os.Open(filename)
 	if err != nil {
-		return "", "", err
+		return nil, err
 	}
 	defer file.Close()
 
 	scanner := bufio.NewScanner(file)
 	for scanner.Scan() {
-		parts := strings.Fields(scanner.Text())
-
-		if len(parts) < 2 || len(parts) > 3 {
+		user := parseLine(scanner.Text())
+		if user == nil {
 			continue
 		}
 
-		if strings.ToLower(username) != strings.ToLower(parts[0]) {
+		if strings.ToLower(username) != strings.ToLower(user.username) {
 			continue
 		}
 
-		hash := parts[1]
-		email := ""
-
-		if len(parts) >= 3 {
-			email = parts[2]
-		}
-
-		return hash, email, nil
+		return user, nil
 	}
 
-	return "", "", errors.New("User not found")
+	return nil, errors.New("User not found")
 }
 
 func AuthCheckPassword(username string, secret string) error {
-	hash, _, err := AuthFetch(username)
+	user, err := AuthFetch(username)
 	if err != nil {
 		return err
 	}
-	if bcrypt.CompareHashAndPassword([]byte(hash), []byte(secret)) == nil {
+	if bcrypt.CompareHashAndPassword([]byte(user.passwordHash), []byte(secret)) == nil {
 		return nil
 	}
 	return errors.New("Password invalid")