Added ability to update Passwords

cmd/data/db.go

@@ -41,7 +41,7 @@ func (db *DB) AddUser(user, pass, first, last string, writer, editor, admin bool
 	}
 
 	if !permissionsOK(writer, editor, admin) {
-		return fmt.Errorf("error with mutually exclusive user permissions: writer = %v, editor = %v, admin = %v",
+		return fmt.Errorf("error with mutually exclusive permissions: writer = %v, editor = %v, admin = %v",
 			writer, editor, admin)
 	}
 
@@ -58,3 +58,39 @@ func (db *DB) AddUser(user, pass, first, last string, writer, editor, admin bool
 
 	return nil
 }
+
+func (db *DB) ChangePassword(id int64, oldPass, newPass string) error {
+	var oldHashedPass string
+
+	selectQuery := `
+    SELECT password FROM
+        users
+    WHERE
+        id = ?
+    `
+	row := db.QueryRow(selectQuery, id)
+	if err := row.Scan(&oldHashedPass); err != nil {
+		return fmt.Errorf("error reading password from DB: %v", err)
+	}
+
+	if err := bcrypt.CompareHashAndPassword([]byte(oldHashedPass), []byte(oldPass)); err != nil {
+		return fmt.Errorf("error checking password: %v", err)
+	}
+
+	newHashedPass, err := bcrypt.GenerateFromPassword([]byte(newPass), bcrypt.DefaultCost)
+	if err != nil {
+		return fmt.Errorf("error creating password hash: %v", err)
+	}
+
+	updateQuery := `
+    UPDATE users
+    SET password = ?
+    WHERE id = ?
+    `
+	_, err = db.Exec(updateQuery, newHashedPass, id)
+	if err != nil {
+		return fmt.Errorf("error updating password in DB: %v", err)
+	}
+
+	return nil
+}