/// ---------------------------------------------------------------------------------------- /// <summary> /// Encrypt preferences using a password /// </summary> /// ---------------------------------------------------------------------------------------- // Encrypt preferences using a password public static byte[] EncryptDataUsingPassword(byte[] data, string password, bool passwordIsHash, SEBSettings.sebConfigPurposes configPurpose) { string prefixString; // Check if .seb file should start exam or configure client if (configPurpose == SEBSettings.sebConfigPurposes.sebConfigPurposeStartingExam) { // prefix string for starting exam: normal password will be prompted prefixString = PASSWORD_MODE; } else { // prefix string for configuring client: configuring password will either be hashed admin pw on client // or if no admin pw on client set: empty pw prefixString = PASSWORD_CONFIGURING_CLIENT_MODE; if (!String.IsNullOrEmpty(password) && !passwordIsHash) { //empty password means no admin pw on clients and should not be hashed //or we got already a hashed admin pw as settings pw, then we don't hash again password = SEBProtectionController.ComputePasswordHash(password); } } byte[] encryptedData = SEBProtectionController.EncryptDataWithPassword(data, password); // Create byte array large enough to hold prefix and data byte[] encryptedSebData = new byte[encryptedData.Length + PREFIX_LENGTH]; Buffer.BlockCopy(Encoding.UTF8.GetBytes(prefixString), 0, encryptedSebData, 0, PREFIX_LENGTH); Buffer.BlockCopy(encryptedData, 0, encryptedSebData, PREFIX_LENGTH, encryptedData.Length); return(encryptedSebData); }
/// ---------------------------------------------------------------------------------------- /// <summary> /// Ask user to enter password and compare it to the passed (hashed) password string /// Returns true if correct password was entered /// </summary> /// ---------------------------------------------------------------------------------------- private static bool askForPasswordAndCompareToHashedPassword(string sebFileHashedAdminPassword, bool forEditing) { // Check if there wasn't a hashed password (= empty password) if (sebFileHashedAdminPassword.Length == 0) { return(true); } // We have to ask for the SEB administrator password used in the settings // and allow opening settings only if the user enters the right one // Allow up to 5 attempts for entering admin password int i = 5; string password = null; string hashedPassword; string enterPasswordString = SEBUIStrings.enterAdminPasswordRequired; bool passwordsMatch; do { i--; // Prompt for password password = SebPasswordDialogForm.ShowPasswordDialogForm(SEBUIStrings.loadingSettings + (String.IsNullOrEmpty(SEBClientInfo.LoadingSettingsFileName) ? "" : ": " + SEBClientInfo.LoadingSettingsFileName), enterPasswordString); // If cancel was pressed, abort if (password == null) { return(false); } if (password.Length == 0) { hashedPassword = ""; } else { hashedPassword = SEBProtectionController.ComputePasswordHash(password); } passwordsMatch = (String.Compare(hashedPassword, sebFileHashedAdminPassword, StringComparison.OrdinalIgnoreCase) == 0); // in case we get an error we allow the user to try it again enterPasswordString = SEBUIStrings.enterAdminPasswordRequiredAgain; } while ((password == null || !passwordsMatch) && i > 0); if (!passwordsMatch) { //wrong password entered in 5th try: stop reading .seb file MessageBox.Show(SEBUIStrings.loadingSettingsFailed, SEBUIStrings.loadingSettingsFailedWrongAdminPwd, MessageBoxButtons.OK, MessageBoxIcon.Error); return(false); } // Right password entered return(passwordsMatch); }
/// ---------------------------------------------------------------------------------------- /// <summary> /// Helper method which decrypts the byte array using an empty password, /// or the administrator password currently set in SEB /// or asks for the password used for encrypting this SEB file /// for configuring the client /// </summary> /// ---------------------------------------------------------------------------------------- private static DictObj DecryptDataWithPasswordForConfiguringClient(byte[] sebData, bool forEditing, ref string sebFilePassword, ref bool passwordIsHash) { passwordIsHash = false; string password; // First try to decrypt with the current admin password // get admin password hash string hashedAdminPassword = (string)SEBSettings.valueForDictionaryKey(SEBSettings.settingsCurrent, SEBSettings.KeyHashedAdminPassword); if (hashedAdminPassword == null) { hashedAdminPassword = ""; } // We use always uppercase letters in the base16 hashed admin password used for encrypting hashedAdminPassword = hashedAdminPassword.ToUpper(); DictObj sebPreferencesDict = null; byte[] decryptedSebData = SEBProtectionController.DecryptDataWithPassword(sebData, hashedAdminPassword); if (decryptedSebData == null) { // If decryption with admin password didn't work, try it with an empty password decryptedSebData = SEBProtectionController.DecryptDataWithPassword(sebData, ""); if (decryptedSebData == null) { // If decryption with empty and admin password didn't work, ask for the password the .seb file was encrypted with // Allow up to 5 attempts for entering decoding password int i = 5; password = null; string enterPasswordString = SEBUIStrings.enterEncryptionPassword; do { i--; // Prompt for password password = SebPasswordDialogForm.ShowPasswordDialogForm(SEBUIStrings.reconfiguringLocalSettings, enterPasswordString); // If cancel was pressed, abort if (password == null) { return(null); } string hashedPassword = SEBProtectionController.ComputePasswordHash(password); // we try to decrypt with the hashed password decryptedSebData = SEBProtectionController.DecryptDataWithPassword(sebData, hashedPassword); // in case we get an error we allow the user to try it again enterPasswordString = SEBUIStrings.enterEncryptionPasswordAgain; } while (decryptedSebData == null && i > 0); if (decryptedSebData == null) { //wrong password entered in 5th try: stop reading .seb file MessageBox.Show(SEBUIStrings.reconfiguringLocalSettingsFailed, SEBUIStrings.reconfiguringLocalSettingsFailedWrongPassword, MessageBoxButtons.OK, MessageBoxIcon.Error); return(null); } else { // Decrypting with entered password worked: We save it for returning it later if (forEditing) { sebFilePassword = password; } } } } else { //decrypting with hashedAdminPassword worked: we save it for returning as decryption password sebFilePassword = hashedAdminPassword; // identify that password as hash passwordIsHash = true; } /// Decryption worked // Ungzip the .seb (according to specification >= v14) decrypted serialized XML plist data decryptedSebData = GZipByte.Decompress(decryptedSebData); // Check if the openend reconfiguring seb file has the same admin password inside like the current one try { sebPreferencesDict = (DictObj)Plist.readPlist(decryptedSebData); } catch (Exception readPlistException) { // Error when deserializing the decrypted configuration data // We abort reading the new settings here MessageBox.Show(SEBUIStrings.loadingSettingsFailed, SEBUIStrings.loadingSettingsFailedReason, MessageBoxButtons.OK, MessageBoxIcon.Error); Console.WriteLine(readPlistException.Message); return(null); } // Get the admin password set in these settings string sebFileHashedAdminPassword = (string)SEBSettings.valueForDictionaryKey(sebPreferencesDict, SEBSettings.KeyHashedAdminPassword); if (sebFileHashedAdminPassword == null) { sebFileHashedAdminPassword = ""; } // Has the SEB config file the same admin password inside as the current settings have? if (String.Compare(hashedAdminPassword, sebFileHashedAdminPassword, StringComparison.OrdinalIgnoreCase) != 0) { //No: The admin password inside the .seb file wasn't the same as the current one if (forEditing) { // If the file is openend for editing (and not to reconfigure SEB) // we have to ask the user for the admin password inside the file if (!askForPasswordAndCompareToHashedPassword(sebFileHashedAdminPassword, forEditing)) { // If the user didn't enter the right password we abort return(null); } } else { // The file was actually opened for reconfiguring the SEB client: // we have to ask for the current admin password and // allow reconfiguring only if the user enters the right one // We don't check this for the case the current admin password was used to encrypt the new settings // In this case there can be a new admin pw defined in the new settings and users don't need to enter the old one if (passwordIsHash == false && hashedAdminPassword.Length > 0) { // Allow up to 5 attempts for entering current admin password int i = 5; password = null; string hashedPassword; string enterPasswordString = SEBUIStrings.enterCurrentAdminPwdForReconfiguring; bool passwordsMatch; do { i--; // Prompt for password password = SebPasswordDialogForm.ShowPasswordDialogForm(SEBUIStrings.reconfiguringLocalSettings, enterPasswordString); // If cancel was pressed, abort if (password == null) { return(null); } if (password.Length == 0) { hashedPassword = ""; } else { hashedPassword = SEBProtectionController.ComputePasswordHash(password); } passwordsMatch = (String.Compare(hashedPassword, hashedAdminPassword, StringComparison.OrdinalIgnoreCase) == 0); // in case we get an error we allow the user to try it again enterPasswordString = SEBUIStrings.enterCurrentAdminPwdForReconfiguringAgain; } while (!passwordsMatch && i > 0); if (!passwordsMatch) { //wrong password entered in 5th try: stop reading .seb file MessageBox.Show(SEBUIStrings.reconfiguringLocalSettingsFailed, SEBUIStrings.reconfiguringLocalSettingsFailedWrongCurrentAdminPwd, MessageBoxButtons.OK, MessageBoxIcon.Error); return(null); } } } } // We need to set the right value for the key sebConfigPurpose to know later where to store the new settings sebPreferencesDict[SEBSettings.KeySebConfigPurpose] = (int)SEBSettings.sebConfigPurposes.sebConfigPurposeConfiguringClient; // Reading preferences was successful! return(sebPreferencesDict); }