Moved error handling for short passwords to library

lib/generator.go

@@ -1,6 +1,8 @@
+// Package securepassword implements a password generator and check.
 package securepassword // import "github.com/Luzifer/password/lib"
 
 import (
+	"errors"
 	"fmt"
 	"math/rand"
 	"regexp"
@@ -8,12 +10,21 @@ import (
 	"time"
 )
 
+// SecurePassword provides methods for generating secure passwords and
+// checking the security requirements of passwords
 type SecurePassword struct {
 	characterTables map[string]string
 	insecurePattern []string
 	badCharacters   []string
 }
 
+var (
+	// ErrLengthTooLow represents an error thrown if the password will
+	// never be able match the security considerations in this package
+	ErrLengthTooLow = errors.New("Passwords with a length lower than 4 will never meet the security requirements")
+)
+
+// NewSecurePassword initializes a new SecurePassword generator
 func NewSecurePassword() *SecurePassword {
 	return &SecurePassword{
 		characterTables: map[string]string{
@@ -36,7 +47,16 @@ func NewSecurePassword() *SecurePassword {
 	}
 }
 
-func (s *SecurePassword) GeneratePassword(length int, special bool) string {
+// GeneratePassword generates a new password with a given length and
+// optional special characters in it. The password is automatically
+// checked against CheckPasswordSecurity in order to only deliver secure
+// passwords.
+func (s *SecurePassword) GeneratePassword(length int, special bool) (string, error) {
+	// Sanity check
+	if length < 4 {
+		return "", ErrLengthTooLow
+	}
+
 	characterTable := strings.Join([]string{
 		s.characterTables["simple"],
 		strings.ToUpper(s.characterTables["simple"]),
@@ -60,9 +80,14 @@ func (s *SecurePassword) GeneratePassword(length int, special bool) string {
 			password = ""
 		}
 	}
-	return password
+	return password, nil
 }
 
+// CheckPasswordSecurity executes three checks to ensure the passwords
+// meet the security considerations in this package:
+// - The password may not contain pattern found on the keyboard or in alphabet
+// - The password must have 3 or 4 different character groups in it
+// - The password may not have repeating characters
 func (s *SecurePassword) CheckPasswordSecurity(password string, needsSpecialCharacters bool) bool {
 	return !s.hasInsecurePattern(password) &&
 		s.matchesBasicSecurity(password, needsSpecialCharacters) &&

lib/generator_test.go

@@ -80,6 +80,15 @@ func TestSecurePasswordWithSpecialCharacter(t *testing.T) {
 	}
 }
 
+func TestImpossiblePasswords(t *testing.T) {
+	for i := 0; i < 4; i++ {
+		_, err := NewSecurePassword().GeneratePassword(i, false)
+		if err != ErrLengthTooLow {
+			t.Errorf("Password with a length of %d did not throw as ErrLengthTooLow error", i)
+		}
+	}
+}
+
 func BenchmarkGeneratePasswords8Char(b *testing.B) {
 	pwd := NewSecurePassword()
 	for i := 0; i < b.N; i++ {

main.go

@@ -65,12 +65,18 @@ func startAPIServer(c *cli.Context) {
 }
 
 func printPassword(c *cli.Context) {
-	if c.Int("length") < 5 {
-		fmt.Println("Passwords with fewer than 5 characters are too insecure.")
+	password, err := pwd.GeneratePassword(c.Int("length"), c.Bool("special"))
+	if err != nil {
+		switch {
+		case err == securepassword.ErrLengthTooLow:
+			fmt.Println("The password has to be more than 4 characters long to meet the security considerations")
+		default:
+			fmt.Println("An unknown error occured")
+		}
 		os.Exit(1)
 	}
 
-	fmt.Println(pwd.GeneratePassword(c.Int("length"), c.Bool("special")))
+	fmt.Println(password)
 }
 
 func handleAPIGetPasswordv1(res http.ResponseWriter, r *http.Request) {
@@ -80,12 +86,14 @@ func handleAPIGetPasswordv1(res http.ResponseWriter, r *http.Request) {
 	}
 	special := r.URL.Query().Get("special") == "true"
 
-	if length > 128 || length < 5 {
-		http.Error(res, "Please do not use length with more than 128 or fewer than 5 characters!", http.StatusNotAcceptable)
+	if length > 128 || length < 4 {
+		http.Error(res, "Please do not use length with more than 128 or fewer than 4 characters!", http.StatusNotAcceptable)
 		return
 	}
 
+	password, err := pwd.GeneratePassword(length, special)
+
 	res.Header().Add("Content-Type", "text/plain")
 	res.Header().Add("Cache-Control", "no-cache")
-	res.Write([]byte(pwd.GeneratePassword(length, special)))
+	res.Write([]byte(password))
 }