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S e n t r y =========== V4.1 Instruction Manual Copyright (C) 1996 Michael A. Bobbitt NightShade Computing Mike.Bobbitt@AcadiaU.CA http//dragon.acadiau.ca/~910318b/Sentry.html S e n t r y =========== Table of Contents 1.0 Introduction 1.1 Purpose of Sentry 1.1.1 In the Home 1.1.2 In a Business Environment 1.1.3 In an Educational Environment 1.1.4 General 1.2 Features of Sentry 1.2.1 General 1.2.2 Expiry Dates 1.2.3 Windows 1.2.4 File Protection 1.3 Distribution of Sentry 2.0 Setup 2.1 Installing Sentry 2.2 The Initial Login 2.3 First Priorities 2.4 Using the Initialization Settings 2.5 Uninstalling Sentry 3.0 Securing Your Computer 3.1 BIOS Password 3.2 Boot Sequence 3.3 SWITCHES in CONFIG.SYS 3.4 BootKeys in MSDOS.SYS 3.5 BREAK in CONFIG.SYS 3.6 Passwords 3.7 Placement in AUTOEXEC.BAT 3.8 Keep a Backup 4.0 Logging In 4.1 The Login Procedure 4.2 Changing Passwords 5.0 The SuperUser Menu 5.1 The User Maintenance Menu 5.1.1 Create User 5.1.2 Delete User 5.1.3 View Users 5.1.4 Toggle SuperUser Status 5.1.5 Change Account Exipry Date 5.1.6 Change Password Expiry Date 5.1.7 Change Account Password 5.1.8 Assign Max Invalid Logins 5.1.9 Return to SuperUser Menu 5.2 The Log File Maintenance Menu 5.2.1 View Log File 5.2.2 View Backup Log File 5.2.3 Move Log File to Backup 5.2.4 Return to SuperUser Menu 5.3 Edit Initialization Settings 5.4 Send a Message to a User 5.5 Protect a File 5.6 Export Initialization Settings 5.7 Exit 6.0 Using Sentry With Windows 6.1 General 6.2 Installation Procedure 6.3 Windows 95 7.0 Securing Other Programs 7.1 General 7.2 Setup 7.3 Account Information 7.4 Using Templates 7.5 Running a Protected File 8.0 Creating a new Instance of Sentry 9.0 Registration 9.1 General 9.2 Benefits of Registration 10.0 The Initialization Settings 10.1 Location of the Log File 10.2 Location of the Backup Log File 10.3 Location of the Message File 10.4 Minimum Password Length 10.5 Maximum Password Length 10.6 Maximum Invalid Tries 10.7 Wait Time After an Invalid Login 10.8 Max Log File Size 10.9 Key to Change Password 10.10 Password Echo Character 10.11 Days Until Passwords Expire 10.12 Days Until Accounts Expire 10.13 Screen Saver Activation Time 10.14 Screen Saver Message 10.15 Login Prompt 10.16 Password Prompt 10.17 Wrong Password Message 10.18 Wrong Login Message 10.19 Bad Password Length Message 10.20 Bad Login Length Message 10.21 Wrong Password Log Message 10.22 Wrong Login Log Message 10.23 Bad Password Length Log Message 10.24 Bad Login Length Log Message 10.25 Environment Variable 10.26 Enable Sentry with Windows 10.27 Show Title 10.28 Date Format 10.29 Case Sensitivity 10.30 Windowed Mode 10.31 Enable Colour 10.32 Text Colour 10.33 Text Background 10.34 Highlighted Text Colour 10.35 Highlighted Text Background 10.36 Maximum Invalid Logins 11.0 Technical Notes 11.1 Encoding Algorithm 11.2 SuperUser Access 11.3 Files 11.4 File_id.diz 11.5 Time / Date 11.6 Environment Variables 11.7 Virus Scanners 11.8 General 12.0 Potential Threats To Security 12.1 Account Information 12.2 Hardware Loopholes 13.0 Troubleshooting 13.1 Error messages 13.1.1 Environment overflow - not modified. 13.1.2 Cannot locate environment! 13.1.3 Error Reading Data Segment! [Open] 13.1.4 Error Reading Data Segment! [Scan] 13.1.5 Error in Initialization Settings! 13.1.6 Error in creating log file! 13.1.7 Error in Account Information. 13.1.8 Error opening log file! 13.1.9 Error opening backup log file! 13.1.10 Error opening temp file! 13.1.11 Internal Screen Error. [Reading] 13.1.12 Internal Screen Error. [Writing] 13.1.13 Out of memory! 13.1.14 Registration Error - Program Aborted! 13.1.15 This account has expired. 13.1.16 Cannot allocate memory for environment block 13.1.17 Error Opening Message File. 13.1.18 Error Opening System Files! 13.1.19 Error opening protected file! 13.1.20 Error opening Sentry.ins! 13.2 Other problems 14.0 Standard Disclaimer 15.0 Contact Information 16.0 Credits ======================== S e n t r y =========== Security for the Home and Business 1.0 Introduction ================ Currently, almost all fields of computer security are growing and advancing, with a few notable exceptions. Networks, servers and public access systems are all tightening their access to avoid potential problems. But what of the non-networked PC? Is the information contained on these any less valuable? Often times not, yet adequate security programs do not exist for PC's. In my search for security, I discovered that PC's were virtually ignored, and those programs that did exist were weak and faulty. Faced with this situation, I decided to write my own security program from scratch, incorporating the tightest security measures possible, while allowing flexible, easy use. 1.1 Purpose of Sentry Sentry is meant for one basic purpose only: to keep unwanted people out of "private" information. It is flexible enough that this single purpose can be used in many different ways, for many different reasons. Here are just a few. 1.1.1 In the Home Most people have something on their home PC that they consider to be "sensitive". Maybe it's a private letter, maybe it's copies of e-mail, or maybe it's financial information. Or quite possibly, you just want to keep track of who is using your system. Sentry has the solution for all of these problems, by restricting access and logging all attempts to use the system. Alternatively, sometimes you just want to keep people out, period. It could be your nosy room mate, your little brother, or your boss at work. In any case, Sentry will keep them out, while letting a select group of people in. 1.1.2 In a Business Environment Businesses will find Sentry valuable to guard against unauthorized entry into PC's. With Sentry, you can leave your terminals unattended while knowing that nobody can access the information held on them, unless you want them to. Many businesses have cleaners or other independent contractors come in during silent hours. A lot of businesses have PC's in open areas where a "passer-by" could use them. Most terminals are left unattended for a portion of the day (lunch, during errands, during meetings, etc.). There's no guarantee that an unauthorized person won't attempt to use your PC's when you're not around. For businesses that work in groups, Sentry is useful for keeping track of who used the PC's and when. Supervisors could have SuperUser access on all PC's in their group, allowing them to manage and control access as required. Also, the log that Sentry keeps could be a valuable tool in determining who was doing what, and when. 1.1.3 In an Educational Environment Schools and educational institutes will find Sentry useful for limiting access to certain terminals. If, for example, only a select group of people (staff, administrators, or a certain class) should have access to specific PC's, simply give each person an account. Anyone without an account cannot log in. Sentry will also help track usage, attempted break-ins, and any suspicious activity. Often school terminals are left unattended, with nothing to stop a student from "poking around." Sentry can act as protection from the prying eyes of the student body. 1.1.4 General You may not need to use Sentry on your system. You might never have a security problem to worry about. But the truth is that Security isn't something to take a chance on. It is a serious problem in today's computing society, and many legitimate users find themselves helpless or confused about the real issues. It is a shame that the immoral few have ruined it for the rest, but we cannot let them get in the way of our daily business. With the proper tools and knowledge, we can fight back by closing up the common loopholes that attackers use. 1.2 Features of Sentry 1.2.1 General Sentry will allow you to set up accounts on your computer, one account for each person you want to have access. If someone doesn't have an account, they don't get in. It's that simple. Each person has their own account, with their own password, making it easy to track who logs in and when. Since Sentry doesn't use a "master access" password, you can wipe a single users account without affecting any other users. Sentry records each login attempt in a log file which can be viewed by a SuperUser at any time. 1.2.2 Expiry Dates You can set accounts to expire on a certain date, effectively barring access to the specified user after that. For example, if you know that Joe will be leaving on April 14th, you can set his account to expire on April 15th. That means you don't have to remember to delete his account on the 15th... It will expire on it's own, and you can delete it whenever you remember. You can also set expiry dates for passwords, meaning that a user will have to enter a new password once his old one has expired. In addition, you can set the period of time that new passwords are good for. 1.2.3 Windows Sentry can be used in conjunction with Windows to make it a more secure environment. You can protect your MS-DOS icon so that only users with an account can drop to DOS. In addition, you can tailor the way Windows operates to allow more protection from accidental deletion or modification of important items. 1.2.4 File Protection In addition to securing your PC, Sentry can secure individual files. If you have a program that you need to keep on your hard drive, but you want to restrict who uses it, you can simply protect that file with Sentry. A good example of this is the FORMAT program. This is a useful command, however you probably don't want it available to the masses. The solution? Protect it with Sentry. Once protected, only those people you designate will be able to execute the program. 1.3 Distribution of Sentry Sentry is a copywritten piece of work, however distribution of the ShareWare version is allowed and encouraged. The only stipulation is that it must be unmodified, and must contain all of the original files (and no others). Essentially, the SentryXX.zip file you initially received is the only format that Sentry is distributable in. DO NOT distribute any registered versions whatsoever. (By distributing a registered version, you are giving out copies of a specific encoding scheme, which can be used against the registered user - and only the registered user!) 2.0 Setup ========= Since you are reading this, I can safely assume you have unzipped Sentry. Along with that, I will also assume that you have created a directory for Sentry, and that all Sentry files are currently in it. (If this is not true, do it now). You may want to read the section entitled "Creating a new Instance of Sentry" below. 2.1 Installing Sentry The very first thing you should do is make sure you keep a copy of all the Sentry files somewhere safe. Copying them to a floppy disk and storing it is a good idea. From here, installation is relatively simple. Just run the program called INSTALL.EXE. You will now be asked for the directory you wish to install to. If it the current directory, you can simply enter a period (.) at this prompt. If you enter another directory, the files will be copied to that new directory, but not deleted from the current one. (You must do that yourself). If you have previously exported your initialization settings, they will be detected now, and you will be asked if you wish to use them. If there are no exported settings, the install program will automatically search to see if your copy of Sentry already has initialization settings. If it does, you will be asked if you wish to over-write them. Enter 'y' if you wish to overwrite them. If you do not already have initialization settings, the install program will automatically use the defaults. Next you will be asked if you wish to update your system files. If you answer 'y' then your AUTOEXEC.BAT, CONFIG.SYS and MSDOS.SYS (for Windows 95 only) will be backed up and modified. This action will cause Sentry to run automatically the next time your computer reboots. Finally, you will be asked if you wish to use Sentry with Windows. If you answer 'y' then you will be asked for the path to your windows directory. You will also be asked a series of questions about general Windows security. The options you select will automatically be set within windows. If you wish to re-set any options, simply run the install program again. Please note that the install program deletes itself after running. This is so it cannot be run by a regular user to gain access. Make sure you keep a backup of the install program in case you need it. 2.2 The Initial Login Now the next thing you must do is to change the password and login provided with the initial copy of Sentry. To do this, you must run the Sentry.exe program. If it displays an error message, check the troubleshooting section at the end of this file. When it asks for a login, use "Sentry", with the password "Sentry". You can turn case sensitivity off via the initialization settings, but only for logins. The password must be entered exactly as shown (sentry or SENTRY will not work). The Sentry account has SuperUser access, meaning you can create and delete accounts while logged in as Sentry. To log in as a SuperUser, enter Sentry for a login, and instead of pressing enter, hold down the CONTROL key and press enter. This tells the Sentry program that you want to log in as a SuperUser. Then enter your password normally, and instead of dropping to DOS, you will go to the SuperUser menu. (See the section below on "The SuperUser Menu" for more information). From here, you should create a new user (you) and grant yourself SuperUser access. You can do this during creation by holding the CTRL key while pressing enter after typing your login name. You can also do this by using the "Create User" option normally and then using the "Toggle SuperUser Access" menu option to give yourself SuperUser privileges. 2.3 First Priorities Once you have your account set up, you should delete the Sentry account, so nobody else can use it. This is very important as a potential intruder will probably try to enter through the default Sentry account first. (If you delete it, that closes the loophole). Sentry will not let you delete the last SuperUser, so you must create a new user with SuperUser access before deleting the Sentry account. From here, you can create the other users of your system, and define their starting passwords, expiry dates and access rights. See the section below on "The SuperUser Menu" for more information. 2.4 Using the Initialization Settings Sentry can be configured to your needs by way of the initialization settings. These settings contain information that you may wish to change, allowing Sentry to adapt to many different situations. You can edit the initialization settings from the SuperUser menu. You can do this by selecting the "Edit Initialization Settings" option (see section 5.10 and section 10 for details). Each setting includes helpful hints and information to simplify customization. Any changes you make will not take effect until the next time you use Sentry. 2.5 Uninstalling Sentry Sentry is simple to uninstall. Simply re-run the INSTALL.EXE program (you may have to get it from backup as it deletes itself after installing). At the "Install Path" prompt, simply enter an asterisk (*) to uninstall. From here you will be asked if you wish to remove Sentry from your hard drive. Responding with a 'y' will delete the files and remove the directory that Sentry is in. Next you will be prompted for your windows directory. If you did not install Sentry with Windows, you can simply enter an asterisk (*) to skip this. When the program finishes, Sentry will no longer be on your system. If you change your mind, you can re-install it at any time. 3.0 Securing Your Computer ========================== Sentry is essentially useless unless you take the appropriate additional security measures for your machine. Below I have outlined some of the things you can do to increase the security of your system. 3.1 BIOS Password Protect your BIOS! It has a built in password, so set it! Without the password, any user can get into your BIOS and change your critical system settings. I have seen several different types of BIOS setups, but generally, you use the CHANGE PASSWORD command (Sometimes also listed as SUPERVISOR PASSWORD) from the main menu and set the SECURITY OPTION to "Setup" (as opposed to "System") in the BIOS FEATURES SETUP screen. Depending on the layout of your BIOS, you may have a CHANGE SETUP PASSWORD option right on the main menu. 3.2 Boot Sequence Change your boot sequence. Again, in your BIOS, under the BIOS FEATURES SETUP screen, set your BOOT SEQUENCE to boot from your hard drive first. (This usually means set it to C,A as opposed to A,C). This will ensure that no-one can bypass Sentry by means of a boot disk. 3.3 SWITCHES in CONFIG.SYS This step is not required for Windows 95 users. Add "switches /n/f" as the first line of your CONFIG.SYS file. The /n will disallow pressing F8 or F5. F8 allows users to step through each command of the CONFIG.SYS and AUTOEXEC.BAT files, and F5 gives them the option of skipping them all together. This means that users cannot bypass Sentry by this method. The /f switch is optional, it simply speeds up your boot-up time (by about 2 seconds). This is automatically done if you update your system files through the install program. 3.4 BootKeys in MSDOS.SYS This step is for Windows 95 users ONLY. Add the line "BootKeys=0" to your MSDOS.SYS file. This will disable the use of F8, F4 or SHIFT to bypass the CONFIG.SYS and AUTOEXEC.BAT files. Adding this line is therefore a must, otherwise people will be able to defeat Sentry with the press of a key. To edit your MSDOS.SYS file, you may need to issue the command "attrib -h -s c:\msdos.sys" which will make it readable. When you are finished, you should issue the command "attrib +h +s c:\msdos.sys" which will restore it to it's previous condition. This is automatically done if you update your system files through the install program. 3.5 BREAK in CONFIG.SYS You must also check your CONFIG.SYS file for any BREAK commands. If the command BREAK=ON is present, delete it! This command may allow users to break out of the CONFIG.SYS file, which is wrong! If BREAK=OFF exists, that is ok (since that is the DOS default, and it is secure), however you must get rid of any BREAK=ON commands. This is automatically done if you update your system files through the install program. 3.6 Passwords Pick a good password. Short passwords are a bad idea, as well as birthdays, girlfriends names, etc. Anything that is easy to guess should be avoided. Good passwords are not words at all, but made up from a "mnemonic" sentence. For example, the sentence "I'll wait for you" turns into "Illw84u" (trust me). Mixing lower case letters, upper case letters, and numbers increases the security of a password, and passwords of this type are near impossible to guess or crack. Do not write your password down, especially near your computer. Try to memorize it if possible. Change your password, but not too often. People who change their passwords too often (less than 6 months or so) tend to write them down, which is a bigger risk. Don't enter your password with someone looking over your shoulder. If someone is in the room, block their view, or wait until they leave. 3.7 Placement in AUTOEXEC.BAT When you are installing Sentry, make sure it is the FIRST file in your AUTOEXEC.BAT! Otherwise, the user may be able to exit when another program is running and avoid Sentry all together! This is automatically done if you update your system files through the install program. 3.8 Keep a Backup Keep a backup copy of all your Sentry files! If something happens to these files, you may be locked out your computer if you don't have a backup. It is best to copy your entire Sentry directory to a floppy disk about once a week, so you won't be caught short. 4.0 Logging In ============== 4.1 The Login Procedure When you first run Sentry, you should see the standard startup screen. Your registration information is contained here. (The shareware release simply says it is registered to Shareware). You should also see a prompt asking you to enter your login (or user name). If instead you see an error message, check at the end of this file for help. While entering your user name, if you have SuperUser access, you can log in as such. You can do this by holding down the CTRL key while pressing enter (CTRL-ENTER). If you do not have SuperUser access, or do not wish to log in as such, simply press enter. In either case, this will send you to the password prompt. Once you have reached the password prompt, you simply enter your password, and hit enter when you are finished. Your password is not echoed to the screen. The minimum and maximum length of both the login and password are set by initialization settings. If you wish to change these, you must do so from the SuperUser menu. After correctly entering your password, Sentry will search for any messages addressed to you. If you have a message waiting, it will be displayed. Pressing 'd' will delete that message, any other key will keep it for the next time you log in. Each message is displayed individually. Next, the date and time of your last login will be displayed. If there have been any invalid login attempts made against your account since the last valid login, you will be told so, and how many. If the number of invalid login attempts against your account has exceeded the maximum allowed, your account will be locked out until the SuperUser resets it. If your account has expired, it will say so, and subsequently lock you out. If your password has expired, it will also say so, but will then prompt you to enter a new password. You may not re-use your old password, and you must pick a password that corresponds to the length limits set out by the initialization settings. Once you have entered and verified your new password, it is given a new expiry date according to the default (again determined by the initialization settings). If you have logged in as a SuperUser, and have SuperUser access, you will now be in the SuperUser menu (see the section below). If not, you will simply be dropped to DOS, and the login procedure is complete. 4.2 Changing Passwords If you wish to change your password at any time, you can do so by entering the pass key. The pass key is defined in the initialization settings, and is displayed when Sentry starts up. The default pass key is "passwd". To change your password, simply enter your user name as usual, and when prompted for your password, enter the pass key. You will then be prompted for your old password (to make sure it is really you), and then you will be asked for your new password, which will be verified and saved to disk. Your new password will expire in the number of days designated by the initialization settings. Changing your password has no effect on SuperUser access. 5.0 The SuperUser Menu ====================== The SuperUser menu is where most of the important actions take place. From here it is easy to perform system administrator tasks, and maintain user accounts. The following options are shown on the SuperUser menu: 1. The User Maintenance Menu 2. View Log File 3. Edit Initialization Settings 4. Send a Message to a User 5. Protect a File 6. Export Initialization Settings 7. Exit Each option is described below. 5.1 The User Maintenance Menu The User Maintenance Menu contains all actions that affect users. The following options can be accessed through the User Maintenance Menu: 1. Create User 2. Delete User 3. View Users 4. Toggle SuperUser Status 5. Change Account Exipry Date 6. Change Password Expiry Date 7. Change Account Password 8. Assign Max Invalid Logins 9. Return to SuperUser Menu Each option is described below. 5.1.1 Create User This option allows you to create users on your system. First of all, you must enter the username (or login) you wish to assign to that user. If you wish to create a user with SuperUser status, type in the username and hold down the CONTROL key when pressing enter. Otherwise, just press enter. Once that is complete, Sentry asks for the password. The password is not echoed to the screen. The user should choose and enter their own password. SuperUsers need not know what the passwords are since they can still manage the accounts without knowing them. The password is entered twice to ensure no typos were made, and then saved in encoded form. The ESCAPE key will abort this operation at any time. Note: There is currently a maximum of 100 users allowed. This limit can be bypassed if required (contact me for a larger capacity version). 5.1.2 Delete User The delete option is very simple. It brings up a list of all users, and you simply use the cursor keys to highlight the user you wish to delete. SuperUsers are denoted by a * to the right of their username. Press enter to select the appropriate user. If the selected user is a SuperUser, Sentry will give a warning. SuperUser or not, Sentry will then ask if you are sure you want to delete them. Any input other than a 'y' will not perform the delete. The ESCAPE key will abort this option at any time. 5.1.3 View Users This option allows you to view all users who currently have accounts on your system. SuperUsers are again denoted by a * to the right of their login name. The last login date/time, account expiry date and password expiry date are also shown to the right of the user's login name. In addition, the number of invalid logins since the users last valid login are shown with the number of invalid logins allowed before an account is locked up. An "X" in the "Max Inv Log" (Maximum Number of Invalid Logins Allowed) column means there is no limit. You can use the PAGE UP and PAGE DOWN keys to scroll forward and back if there are multiple pages of users. Arrows (- and ) will be present if there are additional pages above/below. The ESCAPE key will exit back to the main menu. 5.1.4 Toggle SuperUser Status When this option is selected, it first brings up a list of all users on the system. Again, SuperUsers are denoted by a *. Once you have selected a user, Sentry will ask you if you want to grant/revoke SuperUser access to/from the appropriate user. Any input other than a 'y' will not change that users status. Now the user must enter a password. (Since the SuperUser status is encoded in the password, and the password can never be decoded, I can't change SuperUser access without resetting the password). The user can re-enter their old password, or enter a new one (the old one will be over-written). In a worst case scenario, the SuperUser can re-assign a new password to the user if he is unavailable to enter a new password himself. (A hostile user can have SuperUser access revoked without having to enter a new password; you can do it for him). 5.1.5 Change Account Exipry Date This option lets you define when an account will expire on your system. Expired accounts no longer have access. This option is useful if a user will be leaving. Then you don't have to remember to delete their account on the day they leave. You can set it to expire, and delete it when you remember. This option also works in conjunction with the "Assign Max Invalid Logins" option. Once an account reaches it's maximum number of sequential invalid logins, it expires. The only way to re-activate the account is to change the expiry date with this option. Once you select this option, some information about the account will be displayed. If it is a SuperUser account, Sentry will tell you so. It will then display the account's current expiry date. You will be asked if you are sure you want to change that user's expiry date. Any input other than a 'y' will abort the process, otherwise you will be prompted for the year the account will expire. The year must be entered as 4 digits (IE: 1997). If you enter 'N' at the year prompt, no expiry date is assigned to that account (it is valid forever). If you enter a valid year, you will then be prompted for the expiry month, which is entered as 2 digits (IE: 06 for June) followed by the expiry day, which is also entered as 2 digits. Accounts expire at one second past midnight on the date of expiry. 5.1.6 Change Password Expiry Date This option lets you define when a users password will expire. Once the password has expired, the user must enter a new one. This forces the user to change their password. Once a password has expired, the next time the user logs in he will be forced to enter a new password. The new password is valid for the number of days set by the initialization settings. Once a password has expired, the user cannot re-enter it. He must select a new password. (NOTE: Sentry does not keep historical records on passwords, so a user may alternate back and forth between 2 passwords. This is not a secure practice and should be avoided). Once you select this option, some information about the account will be displayed. If it is a SuperUser account, Sentry will tell you so. It will then display the current expiry date for the password. You will be asked if you are sure you want to change that user's expiry date. Any input other than a 'y' will abort the process, otherwise you will be prompted for the year the password will expire. The year must be entered as 4 digits (IE: 1997). If you enter 'N' at the year prompt, no expiry date is assigned to that password (it is valid forever). If you enter a valid year, you will then be prompted for the expiry month, which is entered as 2 digits (IE: 06 for June) followed by the expiry day, which is also entered as 2 digits. Passwords expire at one second past midnight on the date of expiry. 5.1.7 Change Account Password This option allows the SuperUser to change an account's password, in case the user forgot it, or some other strange disaster has occurred. When assigning a new password to an account, you should set the expiry date to be immediately, so the user is forced to choose a new one. If the previous password had no expiry date, none is assigned to the new password. Otherwise the password expires in the number of days assigned in the initialization settings. You can abort at any time by pressing the ESCAPE key. 5.1.8 Assign Max Invalid Logins This allows you to set the maximum number of invalid logins allowed before an account is disabled. The default number is defined in the initialization settings, and is assigned to all accounts when they are first used. To assign a new maximum, simply select the "Assign Max Invalid Logins" option from the SuperUser menu. From here you will be shown the complete user list, and asked to select the user you wish to change. Pressing the ESCAPE key will abort the operation here. Once you have selected the user, you will be informed if that user is a SuperUser. NOTE: You should not assign a maximum number of invalid logins to your last SuperUser account. If you do, and someone attempts to break in to that account, you could be locked out of the SuperUser menu! Next you will be told what the user's current max invalid login setting is, and asked if you want to change it. Any input other than a 'Y' will abort the operation. Now you will be asked to enter the number of invalid login attempts before an account is disabled. Entering 'N' or a 0 will mean that there can be unlimited invalid login attempts made. Please note that a value of less than 10 may cause you more trouble than good. You may be spending a lot of time re-setting accounts if you pick too low a value, so consider this carefully. Also note that when an account is locked up, it is actually set to expire immediately. As a result, if you wish to re-activate an account, you must change the account's expiry date (see above). This is also handy for determining when the account was actually de-activated. The expiry date for that account it set the day it was locked out. Every time a successful login is made to an account, the invalid login counter is reset. This means that an account will not be locked out if it has a valid login before the maximum is reached. (For example, say an account has a maximum of 10 invalid logins. If there are 7 invalid logins before a successful login, and then 5 more invalid logins, the account will not be locked up. There must be 10 sequential invalid logins for the account to be disabled.) Once you have finished making the change, you can view the user list to make sure it is acceptable. 5.1.9 Return to SuperUser Menu This option simply returns you to the SuperUser menu. It is the same as hitting the ESC key. 5.2 The Log File Maintenance Menu The Log File Maintenance Menu contains all actions required to manage the log file. The following options can be accessed through the Log File Maintenance Menu: 1. View Log File 2. View Backup Log File 3. Move Log File to Backup 4. Return to SuperUser Menu Each option is described below. 5.2.1 View Log File Every time a user logs in, a record is kept on disk. If you want to view that online record, select this option. You will be asked if you want view to the log file for one or all users. Entering 'o' (for one user) will bring you to the userlist, where you can select the user you wish to view. Any other input will show the log for all users. The log file will be displayed one screen at a time. You can press ESC at any time to skip to the end of the file. Once the entire log file has been displayed, Sentry will ask you if you want to clear the log file. If you were viewing a single user's log, Sentry will ask if you want to clear their file. Any input other than 'y' will exit, leaving the log file in tact. If you answer with a 'y', Sentry will clear out the old entries. When viewing the log for all users, that means that all entries will be removed. When viewing the log for a single user, only that user's entries will be removed. The log file itself will not consume much disk space, and so it should be left in tact for historical reasons. You may find it necessary to refer back to the log file to verify certain events. If disk space is a constraint, you can use the "Move Log File to Backup" option described later. You should always keep a close eye on the log file as this will often tell you when something is wrong on your system. All error messages are saved to the log file, so you can see if Sentry has run into any problems. Also, it records the current time, and the username of the user attempting to log in. This will help you to identify any potential attacks on your system. The log file is hidden by Sentry, but you should also place it somewhere safe so that users cannot tamper with it. You can set the location of the log file via the initialization settings. 5.2.2 View Backup Log File This option is the same as "View Log File" except it allows you to view the information you have backed up. This is strictly for historical purposes, so log file information is not lost. 5.2.3 Move Log File to Backup This moves all of the information in the current log file to the backup file. The backup file is not overwritten, the new information is appended to it. This makes it easier to manage when the log file gets large, but you don't want to clear it. 5.2.4 Return to SuperUser Menu This option simply returns you to the SuperUser menu. It is the same as hitting the ESC key. 5.3 Edit Initialization Settings This option allows you to edit the initialization settings. After installation, it is critical that you go through each and every attribute, and make sure it is set to your liking. Many of the initialization settings have serious implications on security. Once this option is selected, all of the attributes are displayed. Simply select the attribute you wish to modify, and you will be given the following information: - A one line description of the attribute. - A brief description of the attribute and it's uses. - Valid settings for the attribute, if applicable. - Any security notes, if applicable. - The default value for the attribute. - The current value for the attribute. At this time, you will be prompted to enter a new value for the attribute. Pressing ENTER on a blank line, or pressing the ESC key abort any changes the current value. Sentry performs strict checking on the values you enter, and will not save an invalid value. See section 10 for details on individual settings. 5.4 Send a Message to a User This option allows the SuperUser to send a one-line message to any user on the system (including themselves). Once this option is selected, you must pick the user you wish to send a message to from the list of all users. Once this is done, you will be prompted for your one-line message. If you wish to send more than one line, simply send two messages to the same user. After you have entered your message, you will be returned to the SuperUser menu. The next time that person logs in, your message will be displayed, including: - Who the message is from - The time and date the message was sent - The message itself The user then has the option to delete the message. If they do not delete the message, they will also see it on their next login. NOTE: Messages are displayed before any login information, so you can send messages to users that are locked out. That way, if you wish to send an explanation, you can. 5.5 Protect a File This option allows you to protect executable files (.EXE, .COM and .BAT). When this option is selected, it prompts for the file name. You must enter a path to a file that exists, and the file must be executable. If the file name is correct, Sentry then processes that file, and "protects" it. Protection means that the next time that file is run, Sentry will execute. If the user enters a valid login and password, then the original file executes. If not, then the file is not executed. This is useful for protecting individual files. After all, if a person successfully logs into your computer, they have free access to anything there. This will allow you to tighten up access to individual files. The current method of protection does not work with all files. That is to say, I have tested it on some files that do not run correctly once protected. (It seems to be memory or video conflicts). Currently, a protected file has about 100k less memory available to it than if it was run normally. Also, protecting programs that run within Windows does not work. These issues are "on the list" for research. See section 7 for specific details on protecting files. 5.6 Export Initialization Settings Selecting this option will export the Initialization Settings. This will allow you to use the same settings and account structure when you upgrade. The process for this is simple. Select this option, and it will export the settings. Now simply unzip the new SentryXX.zip into your directory (overwriting all files), and run the Install.exe program. Install will automatically sense the exported information, and ask if you want to use it. If you say yes, the settings are automatically updated to the new version, and loaded in. Please note that you should not export the settings unless you plan to import them right away into a new version (it can cause a slight security risk). 5.7 Exit This simply returns you to the DOS prompt. It is the same as pressing the ESCAPE key. 6.0 Using Sentry With Windows ============================= 6.1 General Sentry is also adaptable to Windows, allowing you to keep users away from DOS. This may be desirable if you enter Windows immediately upon startup (I.E.: your AUTOEXEC.BAT contains "win" as a command). If you want to limit access to your system as a whole, you could install Sentry in the usual way. This would keep out unwanted users all together. If you want to also limit access to the DOS prompt from Windows, you can do that too. All you must do is create a new instance of Sentry (see below), and then simply set up your windows to run Sentry when you drop to DOS. The example setup below assumes you have installed an instance of Sentry in c:\Sentry\Inst1, but you can substitute your actual directory names in where applicable. 6.2 Installation Procedure Installing Sentry in the Windows environment is simple. Included in the Sentry zip file are 2 files: Sentry.grp Sentry.pif Both of these will be copied to your windows directory during the install. Enter Windows and from the Program Manager, select [F]ile, then [N]ew. Next select Program Group. When prompted, enter "Sentry" for both description and file name. Now you should see a new program group called Sentry. The Sentry program group should contain a single icon, labeled MS-DOS. This icon actually points to sentry.pif, which contains specific information about running Sentry. You can edit the new icon (highlight it and press ALT-ENTER) and change the working directory to point to your Sentry files. IE: c:\Sentry, or c:\Sentry\Inst1, etc. From here, run the Pif Editor program (the icon is a little tag), and open Sentry.pif. Now change the "Program Filename" to point to your Sentry.exe file. IE: c:\Sentry\Sentry.exe, or c:\Sentry\Inst1\Sentry.exe, etc. In Addition, change the "Working Directory" to be the same as the working directory for the icon (see above). Once you save the .pif file, you are all set. At this point you should test out the new Sentry icon to make sure it works ok. When you double click on the new icon, it should take you directly to Sentry. Once you have entered a correct username and password, it will then drop you to a regular DOS shell. You can type "EXIT" to return to Windows at any time. Once you are sure it works, remove your old MS-DOS icon, so that users cannot use it to drop straight to DOS. You can drag your new icon into the same location as your old MS-DOS icon, so everything will look the same. Now there is one last step. If a user were to exit Windows, they would be at the DOS level, which is not what we want. Since your AUTOEXEC.BAT file is running windows on startup, you can block people from exiting by forcing them to go through Sentry. You can do this by adding a call to Sentry after the win command in your AUTOEXEC.BAT. For example, the last lines of your AUTOEXEC.BAT might look like this: ----------------- CUT ---------------- win \Sentry\Inst1\Sentry ----------------- CUT ---------------- Alternatively, you can add the security measures offered by the install program. If it seems like a complicated process, just try the steps one at a time, and make sure everything works ok. The end result is that when you click on the MS-DOS icon, it will run Sentry before dropping you to the DOS shell. That means that you can limit access to the operating system, without pulling any fancy tricks in Windows. Since you have made a new instance of Sentry, you could have one instance run when you boot up (giving access to windows), and have another instance run when you click on the DOS icon (giving access to the operating system). That way, a user that has access to your PC may not be able to drop to DOS. Be warned that Sentry will still lock up your terminal if a user fails to log in. If this happens in Windows, you may be able to recover back to Windows by pressing CTRL-ALT-DELETE and closing the DOS prompt. This will still not allow access to DOS, but you will not lose anything you were working on. 6.3 Windows 95 Sentry is easily adaptable to use in a Windows 95 environment. In most respects, the setup is the same as in a DOS/Windows environment. The primary difference with Windows 95 is instead of adding the line "switches /n/f" to your CONFIG.SYS file, you must add the following line to your MSDOS.SYS file: BootKeys=0 This will disable the use of F8, F4 or SHIFT to bypass the CONFIG.SYS and AUTOEXEC.BAT files. Adding this line is therefore a must, otherwise people will be able to defeat Sentry with the press of a key. To edit your MSDOS.SYS file, you may need to issue the command "attrib -h -s c:\msdos.sys" which will make it readable. When you are finished, you should issue the command "attrib +h +s c:\msdos.sys" which will restore it to it's previous condition. As before, ensure that the call to Sentry is at the beginning of your AUTOEXEC.BAT file. The Sentry.pif file and Sentry.grp file will still work with Windows 95, although at this time I have not drawn up specific instructions for installation. I have not yet conducted thorough tests in a Windows 95 environment, however documentation for this should be forthcoming in a future revision. 7.0 Securing Other Programs =========================== 7.1 General In some cases, it might be beneficial to secure a single program. It might be a word-processor, Windows, or a potentially dangerous file like FORMAT.COM. In any case, you can secure it with Sentry, even if you don't use Sentry during boot-up. 7.2 Setup To successfully protect your file, you must keep a backup. (Sentry cannot reverse the process of protecting a file!) This backup should not be kept anywhere accessible (IE: make a backup on floppy, and store it somewhere safe). After all, if a user can run an unprotected version of the file, why bother protecting it in the first place? It is wise to test the file once it has been protected to ensure it works as expected. To protect a file, simply chose "Protect a File" from the SuperUser menu. Sentry will ask for the file name of the file to protect. The file must be an executable (IE: it ends with .EXE, .COM or .BAT). Batch files are automatically converted into .EXE files. Once you have entered a correct file name, Sentry will then proceed to protect the file. When it is finished, you will be returned to the SuperUser menu. Your file is now protected! The applications for this type of protection are almost limitless. Use your imagination. If you come up with an innovative idea, I would be interested in hearing about it. 7.3 Account Information The account structure for a given protected file is copied from the version of Sentry that protected the file, but is unique. That is, once a file is protected, a SuperUser can add/delete/modify any accounts for that protected file without affecting any other copies of Sentry. The initialization settings are treated in the same manner. Each protected file has their own unique copy. To change account information on a protected file, simply run the file, and when Sentry executes, log in as a SuperUser. You can now perform all SuperUser options as usual. 7.4 Using Templates It is possible to set up "template" instances of Sentry for use when protecting files. This can be extremely useful as it saves the administrator a considerable amount of time, as well as decreasing the possibility of making a mistake. To use templates, you must set up several instances of Sentry (one for each template you wish to use). See section 8 for instructions on how to create an instance of Sentry. A sample setup could be as follows: c:\Sentry | +----+------- Private | +------- Public | +------- SemiPub With each instance having a complete copy of Sentry. Next simply modify the account structure of each instance to match the template. That is, the Private instance would contain only the SuperUser(s), the Public may contain all users, and the Semi-Public would contain the SuperUser(s) plus some users. Now you would use the Private instance as a template to protect exclusive executables, such as format.com. When you use the Private template, the protected file is automatically set to allow only SuperUsers to run it. Similarly, the Semi-Public template can be used for programs that only the SuperUser and a select number of users have access to. The advantage to using templates is that the administrator need only set up the account structure and initialization settings once. From that point forward it becomes the default for all files protected using that template. 7.5 Running a Protected File To use a protected file, simply run it as usual. Now, instead of the program executing, Sentry will run. The user will be confronted with a login prompt, and they must enter a correct login and password to continue. An unsuccessful login will result in the user being locked out (as with Sentry in normal use). A successful login will simply run the protected file. Once the file is run, the user will be returned to whatever they were doing (IE: the DOS prompt, etc). Command line arguments are passed to protected files in the same manner as usual. To run the file FORMAT with the argument A:, it would look like this: format a: which is identical to the usual way of passing command line arguments. 8.0 Creating a new Instance of Sentry ===================================== In some of the scenarios listed above, you may be required to create a new "instance" of Sentry. That is to say, a completely new copy of Sentry, that works independently of all other copies. This is a fairly simple process, that you can perform as many times as required. The first thing you must do when creating a new instance is to create the directory you wish to place it under. If you plan to have several instances, you may want to create a Sentry main directory, with your instances branching off of that. For example: c:\Sentry | +----+------- Inst1 | +------- Inst2 This will allow you to keep all your Sentry files well organized, and separate from your other programs. Create a directory for each instance you anticipate you will need. From there, simply copy ALL of the Sentry files into each directory. The final step is to set up the accounts of each instance according to your needs. To do this, you must go into each directory individually and run Sentry. Now log in as a SuperUser and set up all the required accounts. Remember that each instance is independent of the others. Your account information will not be the same for any 2 instances (otherwise there is no advantage to having 2 instances). You should always test out each instance and make sure it works before using it. 9.0 Registration ================ 9.1 General If you use Sentry on your machine(s), I urge you to register. I have put a lot of time and effort into making Sentry a viable security program, and I would appreciate the effort very much. On the other hand, I realize that not everyone can afford to register. In that case, please feel free to continue to use the ShareWare version. There are no limitations on how long or how many times it can be used. My intention with Sentry was to make a contribution to PC security, and to make it available to everyone. All I ask is that if you use Sentry, and are able, please register. The shareware version of Sentry has all the functionality of the registered version, with one exception: it does not encode passwords. This will allow you to test out all the functions of Sentry before you commit to purchasing it. The ShareWare version in itself is a very secure program as is, however if you are serious about Security, plaintext passwords are not a viable option. To order, simply fill out the order form provided (Order.frm) and e-mail or snail-mail a copy to me. 9.2 Benefits of Registration As a registered user, you will receive: - The full Sentry program (with password encryption) and related files on 3.5" disk. - A laser printed user's manual (essentially this file, with a few changes in format and content). - Online internet support via e-mail. - Free upgrades as soon as they are available. - Notices about any potential security risks, and instructions on how to protect yourself. - The ability to request specific features in future versions of Sentry. - A clear conscience knowing that you paid for your software. NOTE: Registered versions are not inter-compatible. That is, user X's account information is encrypted differently than user Y's. The version of Sentry that you receive is good only for you and your files. (Likewise, nobody else can use their copy of Sentry with your account information). See the order form for information on obtaining compatible versions of Sentry. 10.0 The Initialization Settings ================================ 10.1 Location of the Log File This contains the location of the log file. The log file should be kept somewhere safe, tucked away from prying eyes. NOTE: You should change the name of the file from Sentry.log to some other, inconspicuous name. Potential intruders will search for the Sentry.log file. You can hide it under misleading names such as file_id.diz, chklist.ms, warm.com etc etc. Default: c:\Sentry.log 10.2 Location of the Backup Log File This contains the location of the backup log file. When the max log file size has been reached, half of the log file is automatically moved to the backup log file. This prevents the primary log file from getting too large. Default: c:\backup.log 10.3 Location of the Message File This contains the location of the message file. The message file should be kept somewhere safe, tucked away from prying eyes. NOTE: You should change the name of the file from Sentry.msg to some other, inconspicuous name. Potential intruders will search for the Sentry.msg file. You can hide it under misleading names such as file_id.diz, chklist.ms, warm.com etc. Default: c:\Sentry.msg 10.4 Minimum Password Length Sets the minimum length for passwords and logins. NOTE: A value of 4 should be the absolute minimum for MinPasswordLen. A value of 5 or 6 would be even better. Short passwords are much easier to stumble across since less attempts have to be made before it is guessed. Default: 4 10.5 Maximum Password Length Sets the maximum length for passwords and logins. Default: 20 10.6 Maximum Invalid Tries Sets the maximum times a user can attempt to log in before being locked out. NOTE: This should not be set too high. It is very rare for a legitimate user to botch a login attempt 3 times in a row. A potential intruder will usually have to make many attempts before getting anywhere. Setting MaxTries to around 3 will slow him down greatly, as he will have to reset after 3 failed attempts. Default: 3 10.7 Wait Time After an Invalid Login Sets the delay in seconds to wait after the user fails to log in. NOTE: Setting the WaitTime to 3 or above greatly slows any methodical attempt to guess or discover passwords. It offers little inconvenience to the end users while providing added security. Default: 3 10.8 Max Log File Size This sets the maximum size the log file can reach before the oldest half of it is automatically moved to the backup log file. The size is given in number of kilobytes (1024 bytes). A value of 0 means never backup the log file. Default: 20 10.9 Key to Change Password Sets the "key" to enter as a password to change passwords. Default: passwd 10.10 Password Echo Character Sets the character to be echoed to the screen when the password is being entered. Enter '?' to display no character. Enter '!' to display the actual character (not recommended). Default: * 10.11 Days Until Passwords Expire Sets the number of days a password is good before it expires. This is the Default value used whenever a password is changed. Individual passwords can be set to expire on the SuperUser menu. NOTE: It is a good idea to have this set to between 180 and 365. Anything over a year is a security risk due to age. Anything under half a year is a risk because people will tend to forget their passwords and start writing them down. This setting should depend on how busy your system generally is. 0 = Never expire passwords. Default: 365 10.12 Days Until Accounts Expire Sets the number of days an unused account is good before it expires. This is the Default value used whenever an account is created. Individual accounts can be set to expire on the SuperUser menu. NOTE: This setting should depend on the level of activity on your system. Active systems can afford to have a lower setting than generally inactive settings. You should also take into consideration the probability of an intruder using an old account. 0 = Never expire unused accounts. Default: 365 10.13 Screen Saver Activation Time This sets the amount of idle time (in seconds) that may pass before the screen saver is activated. Default: 300 10.14 Screen Saver Message This is the message that is displayed randomly on the screen when the screen saver is active. Default: This is a Secure Terminal. 10.15 Login Prompt This sets the value of the prompt that is displayed when the user is expected to enter their login name. Modifying this allows you to customize your environment as you see fit. Default: Login: 10.16 Password Prompt This sets the value of the prompt that is displayed when the user is expected to enter their password. Modifying this allows you to customize your environment as you see fit. Default: Password: 10.17 Wrong Password Message This sets the message to be displayed when a user enters the wrong password. NOTE: It is a good idea to keep the wrong password and wrong login messages the same. Otherwise, a potential intruder will know when he has found an account (IE: If Sentry responds with "Invalid Password", he knows the login was correct). Keeping the two the same prevents an attacker from knowing if he even has the correct login. Default: Invalid Login. 10.18 Wrong Login Message This sets the message to be displayed when a user enters the wrong login. NOTE: It is a good idea to keep the wrong password and wrong login messages the same. Otherwise, a potential intruder will know when he has found an account (IE: If Sentry responds with "Invalid Password", he knows the login was correct). Keeping the two the same prevents an attacker from knowing if he even has the correct login. Default: Invalid Login. 10.19 Bad Password Length Message This sets the message to be displayed when a user enters a password of invalid length. NOTE: It is wise to keep the wrong password length, wrong login length, wrong password and wrong login messages the same. This will prevent a potential attacker from knowing the max and min settings for passwords or logins on your system. (Knowing the length of a password can greatly decrease the amount of time required to crack it). Default: Invalid Login. 10.20 Bad Login Length Message This sets the message to be displayed when a user enters a login of invalid length. NOTE: It is wise to keep the wrong password length, wrong login length, wrong password and wrong login messages the same. This will prevent a potential attacker from knowing the max and min settings for passwords or logins on your system. (Knowing the length of a password can greatly decrease the amount of time required to crack it). Default: Invalid Login. 10.21 Wrong Password Log Message This sets the message to be saved to the log file when a user enters the wrong password. Default: User entered the wrong password. 10.22 Wrong Login Log Message This sets the message to be saved to the log file when a user enters the wrong login. NOTE: This message should be descriptive, since the SuperUser will use it to determine what sort of activities have been happening. Default: User entered the wrong login. 10.23 Bad Password Length Log Message This sets the message to be saved to the log file when a user enters a password of invalid length. Default: Invalid Password Length. 10.24 Bad Login Length Log Message This sets the message to be saved to the log file when a user enters a login of invalid length. Default: Invalid Login Length. 10.25 Environment Variable This sets the environment variable used to store the user's login name after a successful login. NOTE: The environment variable USER is used by many networks, such Novell. By using this setting, Sentry can be used in conjunction with these networks. Default: USER 10.26 Enable Sentry with Windows The Windows flag is set if you wish to run Sentry from Windows. Technically, this allows Sentry to open up a DOS shell after a successful login. Setting this option to 1 has no effect on normal use, and is not a security risk. (0=Do Not Run In Windows, 1=Run In Windows) Default: 1 10.27 Show Title This determines if the intro screen is displayed or not. You may choose not to display the title information if you don't want users to know what program you are using. On the other hand, the registration information should be displayed for authenticity's sake. I have added this option because security comes before all else. (0=Not Displayed, 1=Displayed) Default: 1 10.28 Date Format This will allow you to have dates displayed in different formats. Some people prefer different formats than others, so this will allow you to define the way dates are displayed. (0=MM/DD/YYYY, 1=DD/MM/YYYY) Default: 1 10.29 Case Sensitivity This sets the case sensitivity. If "Case Insensitive" is selected, "SENTRY" "sentry" and "Sentry" are all treated as the same at the login prompt. If case sensitivity is enabled, the three are all treated as different logins. (0=Case Sensitive, 1=Case Insensitive) NOTE: Using "Case Insensitive" reduces the number of allowable logins, and increases the probability of an attacker getting a correct login. Still, some people find it easier to work with Case Sensitivity off. Default: 0 10.30 Windowed Mode This allows you to use Sentry in a "windowed" mode (not to be confused with Microsoft Windows). If the windowed mode is undesirable, you can choose not to use it. (0=Regular Mode, 1=Normal Windowed Mode, 2=Exploding Windowed Mode) Default: 2 10.31 Enable Colour This determines if colour will be displayed by Sentry or not. Some laptop users may wish to use the black and white setting for better readability. (0=Black and White, 1=Colour) Default: 1 10.32 Text Colour You can set TextColour to the value of the colour you wish normal text to appear in. Colour values are shown in the chart below. COLOURS: 0 Black 4 Red 8 Dark Gray 12 Light Red 1 Blue 5 Magenta 9 Light Blue 13 Light Magenta 2 Green 6 Brown 10 Light Green 14 Yellow 3 Cyan 7 Light Gray 11 Light Cyan 15 White Default: 15 10.33 Text Background You can set TextBackground to the value of the colour you wish normal text to have as a background. Colour values are shown in the chart below. COLOURS: 0 Black 4 Red 1 Blue 5 Magenta 2 Green 6 Brown 3 Cyan 7 Light Gray Default: 1 10.34 Highlighted Text Colour You can set HighColour to the value of the colour you wish highlighted text to appear in. Colour values are shown in the chart below. COLOURS: 0 Black 4 Red 8 Dark Gray 12 Light Red 1 Blue 5 Magenta 9 Light Blue 13 Light Magenta 2 Green 6 Brown 10 Light Green 14 Yellow 3 Cyan 7 Light Gray 11 Light Cyan 15 White Default: 1 10.35 Highlighted Text Background You can set HighBackground to the value of the colour you wish highlighted text to have as a background. Colour values are shown in the chart below. COLOURS: 0 Black 4 Red 1 Blue 5 Magenta 2 Green 6 Brown 3 Cyan 7 Light Gray Default: 7 10.36 Maximum Invalid Logins This sets the Default number of consecutive invalid logins possible before an account is locked out. Only a SuperUser can subsequently unlock an account. Default: 10 11.0 Technical Notes ==================== 11.1 Encoding Algorithm The encoding algorithm used is the standard UNIX Crypt() algorithm. It is a one-way encoding algorithm that incorporates the Data Encryption Standard (DES) and RSA technology. It is used on UNIX systems to secure passwords. (As a note, the encryption code is not included with the ShareWare version, so no amount of examining the code will reveal the algorithm). The users' passwords are never decoded. They are stored on disk and in memory in an encoded format. The entered passwords are encoded using the same algorithm and matched in an encoded form. This prevents disk or memory scans from revealing the password to prying eyes. I have begun running some tests on cracking the passwords, and I will include my results. So far, this is what I have found: Password Length Maximum Time to Break ------------------------------------------------ 4 22 days 5 1368 days or 3.75 years 6 232.4 years 7 14409 years 8 893357 years All times listed are approximated as using a Pentium 90MHz CPU and an alpha-numeric password. These figures may be adjusted as my testing becomes more accurate. The above figures also assume you know the length of the password, which cannot be determined by looking at the encrypted version. As a result, the search time may be much greater. 11.2 SuperUser Access SuperUser access is also encoded in the password. I tried many different ways before finally settling on this. It is the most secure method. Actually, SuperUser access is stored on the password (which is then encoded), and then stored again on the encoded password. That looks like: password <-- Password as entered. super(password) <-- Password with SuperUser stamp. * This is the stamp that is used to determine access. crypt(super(password)) <-- Encoded password with SuperUser stamp. super(crypt(super(password))) <-- SuperUser stamped encoded password with SuperUser stamp. * This is the stamp that is used to "see" who has SuperUser access. That way when you use the "View Users" command, you can see which ones are SuperUsers. However, since the non-encoded SuperUser stamp can be edited, it is only used for viewing. The encoded SuperUser stamp is used for access. If anyone attempts to alter the SuperUser stamp, a warning will be displayed in the log file each time that user logs in. 11.3 Files The following files are included with this release of Sentry: Sentry.exe This is the executable program. Install.exe The installation program. File_id.diz Short description file. History.txt The complete revision history of Sentry. License.txt The license agreement. Order.frm The order form. Qstart.txt Quickstart instructions. Readme.com Displays this file. Readme.txt This file. Sentry.ins Descriptions of Initialization Settings. Sentry.hlp Sentry's Help file. Sentry.grp The Sentry Group file for Windows. Sentry.pif The Sentry .pif file for Windows. Whatsnew.txt A short description of modifications to the latest version. If you do not have all of these files, Sentry may not work for you. You can pick up a complete copy of Sentry (and updates as they become available) at: http://dragon.acadiau.ca/~910318b/Sentry.html 11.4 File_id.diz The actual contents of the file_id.diz file are shown below. If any modification has been made to the original file, please re-create it from the following section. NOTE: this is primarily for SysOps of BBS's. Single users can delete the file_id.diz if they wish. (However, please make sure that all files are present if you distribute the program.) -------------------CUT----------------------- (V4.1) Sentry - Security for DOS/Windows/95. Sentry is an extremely flexible program that allows you to secure your system, individual files, Windows, Win 95 or any combination. It supports up to 100 users with normal and "SuperUser" access. Detailed log files help keep track of activity. Expiry dates and a mini message system help with user admin. http://dragon.acadiau.ca/~910318b/Sentry.html Mike Bobbitt [Mike.Bobbitt@AcadiaU.Ca] -------------------CUT----------------------- 11.5 Time / Date NOTE: I have found one date which always seems to cause an error. 01/01/1997 translates to 01/15/1995 (1st day of the 15th month of 1995). This is obviously incorrect. I have determined it is a bug in Borland's date conversion routines. It is the ONLY date that causes problems, to my knowledge, all others translate fine. I advise against using 01/01/1997 for any expiry dates. This problem is still under investigation. 11.6 Environment Variables When a user successfully logs in, a DOS environment variable is set to that user's login name. This can be a very useful feature as it allows custom programs to link with Sentry in a meaningful way. For example, if you are running Sentry from a batch file, you can check to see who logged in, and take appropriate action. Shown below is a short batch file which can be used for this type of function: -----------CUT----------- @echo off rem *** Run Sentry. \sentry\sentry cls rem *** Test to see who logged in. if %user==ROBERT goto robert if %user==DANNY goto dan rem *** Use a line like the one above for each user. goto end :robert rem *** Note that individual users have their own commands. echo SuperUser (Robert) logged in. defrag c: goto end :dan echo Dan logged in. goto end rem *** add more users as you see fit :end -----------CUT----------- NOTE: Batch files are not secure! No critical functions should be placed here unless it's absolutely necessary! An alternative (and more secure) method is to write a program in another language (like C) and compile it. Most programming languages allow you to read environment variables. This means that you can write your own custom extensions to Sentry, which will execute after a person logs in. Please also note that the usernames in the environment variables are all capital letters. (Sentry becomes SENTRY when it is set). ** NOTE: Although the environment variables are secure immediately after Sentry runs, they may not be secure after other programs have run. By this I mean that another program could alter the environment variables to make it LOOK like a different user logged in. As a result, try to do all your checking immediately after Sentry runs. 11.7 Virus Scanners If you scan your system with a virus scanner such as Microsoft Anti-Virus, you may find that Sentry will show up quite often. The reason for this is that some virus scanners record statistics on executable files. When the next scan is performed, if the executable files do not match the statistics, the scanner panics. This can SOMETIMES be evidence of a virus on your system. Sentry modifies itself (in a manner similar to a virus) and so may be picked up on occasion, however please be aware that there is no threat from Sentry. SENTRY IS NOT A VIRUS! Every time you use Sentry, the executable is modified, and will cause your virus scanner to panic! Do not be alarmed, since this is normal operation for Sentry. 11.8 General Sentry is written in Borland C, with sections of C++. As of version 4.1, Sentry contains over 5400 lines of code. Portability between machines is not an issue, since Sentry has been designed and tested on standard MS-DOS machines. Sentry is verified compatible with Windows 3.x and Windows 95. 12.0 Potential Threats To Security ================================== Never underestimate your users. And never be satisfied that your system is completely "air-tight". Users are incredibly apt at finding loopholes in security, and once found, these holes can be exploited. Because of this, I am listing below all of the security loopholes that I am aware of at this time. 12.1 Account Information With the release of Sentry V3.0, account information has become much more secure. It is still POSSIBLE however that a user can find and dissect the account information. The probability of this is remote though, since the information is not easily edited or understood. Also, all of these methods require a working knowledge of how Sentry operates, and that is not commonly available. The best source for that information would be from this file, which is deliberately missing some key pieces of "technical" information. If a user did manage to decipher the account information, he could do any of the following: - Add/Remove an expiry date (account or password) This is not a serious issue for passwords, as the user would still have to enter their old one before being notified that their password has expired. An attacker can NOT expire a password and then log in to that account. - Edit a username This would effectively lock out that user, unless they could guess their new user name. - Delete a user Users can be deleted, but not created. - Destroy a password Since passwords are encoded, there is no way to change a password to something usable. An edited password will likely lock that user out of their account, until the password is reset. - Change "last login" information Not critical, but could be used to cover an attackers tracks. - Change "number of invalid logins since last login" information Same as above. - Add/Remove restrictions on the number of invalid login attempts Could allow a "brute force" technique to work on an account password if the restriction was lifted. Also, if an attacker set this restriction to 1 invalid login, that account would be disabled if a single failed login attempt was made. It is important to know however, that a renegade user can never grant himself SuperUser privileges, nor can he ever attempt to effectively modify a password. To perform any of these functions, he MUST be logged in as a SuperUser. In addition, NOBODY (not even SuperUsers) can view passwords. (They can never be decrypted, remember?) In essence: Sentry does it's part for security, but you must do yours as well... GUARD YOUR SUPERUSER PASSWORDS! 12.2 Hardware Loopholes Although it is unlikely that a user will do this, there is a potential security risk to Sentry. Fortunately, this method can only be implemented by highly technical users. If a user really wants to get into your system, he can disassemble it, and take the battery out of your BIOS. This will reset your BIOS to the standard setup, which does not include password protection. From there, the user can enter your BIOS, and change the boot sequence from C,A to A,C. This means that your computer will search for a boot disk before booting from your hard drive. Therefore, the user can get in if he has a pre-made boot disk. Like I said, it's unlikely, but possible. If you want to fix up this back door, you can re-wire your floppy disk drive so that it is never used on boot up. I do not have instructions for that at this time, however I am looking, and will include them in future. Along the same lines, a user could replace your hard drive (the one containing Sentry) with another hard-drive. This way he could then boot up using the new hard drive, and never have to worry about Sentry. Also, if he kept your hard drive on the system (as drive D for example), he could still access your data. This kind of trickery is highly improbable, but not impossible. The above two methods take more technical skill than the average user possesses, and should not be considered a serious threat. I include them simply so you can be aware such things exist. If you are concerned about attacks of this nature, you should secure your system's case to the frame (IE: make it impossible to open the case with a screwdriver - install a locking mechanism or fuse the screws to the frame). It is critical to realize that it is EXTREMELY difficult to repel a determined and well-organized attack. Using Sentry does not guarantee your computer's safety. It does however greatly reduce the threat of a successful attack, and more importantly, it can alert you to potential threats before they become a serious problem. Your ability to defend is much greater once you know you are under attack. Sentry can keep you informed of suspicious actions on your PC, as well as being is a powerful tool in defeating most threats. 13.0 Troubleshooting ==================== 13.1 Error messages Below are listed all possible error messages you can get while running Sentry. With each is a brief description of what it means, probable causes, and how to fix it. Please be aware that ALL of these errors cause Sentry to lock-up. This may be an inconvenience at times, but it is done for security reasons (that way an attacker can't "induce" an error and get into the system). 13.1.1 Environment overflow - not modified. There was an error trying to set modify the DOS environment. It may occur if you try to run Sentry from within the Sentry DOS shell (IE: running Sentry from Windows, then when you're in the shell, running it again). If this error occurs, you are generally using too many environment variables for the amount of space you have allotted. See your DOS manual for ways of increasing environment space. 13.1.2 Cannot locate environment! This indicates an error with your DOS environment. Make sure that you are using the regular environment, or that it is set up correctly. 13.1.3 Error Reading Data Segment! [Open] This occurs when the initialization settings or account information is not acting as expected. Make sure that you have about 80k of disk space free, and that your Sentry.exe file is not read-only. 13.1.4 Error Reading Data Segment! [Scan] This usually indicates that there are no initialization settings. The easiest way to remedy this is to re-install Sentry (see section 2 for details). That will create initialization settings, or over-write the old settings if they are invalid. 13.1.5 Error in Initialization Settings! Your initialization settings are corrupt or could not be read. The best bet here is to re-install Sentry from scratch, and over-write the current settings. If you find this occurring frequently, it is probably a bug of some sort, and I should be contacted. 13.1.6 Error in creating log file! The file that logs all transactions to your computer cannot be created. Make sure you have specified a valid pathname for this setting, and make sure you have about 80k of free space on your drive. If a log file already exists, it will be appended to. Otherwise it will be created. 13.1.7 Error in Account Information. This means there is a problem with the account information for a certain user. You can either try restoring your sentry.exe file from backup, or you can re-install it (see section 2 for details). If you continue to use corrupt account information, you will find you are locked out quite frequently. It should be a top priority to fix the account info. 13.1.8 Error opening log file! There is a problem with the log file. Make sure that the log file pointed to by the initialization settings is not write-protected. 13.1.9 Error opening backup log file! There is a problem with the backup log file. Make sure that the file pointed to by the initialization settings is not write-protected. 13.1.10 Error opening temp file! A temporary storage file cannot be opened. Make sure you have at around 80k of disk space left when you run Sentry. 13.1.11 Internal Screen Error. [Reading] This error should never occur. Having said that, if it does, your best bet is to check your video mode. Sentry has only been tested in 80x25 text mode, so make sure that is what you are using. If this error crops up, please contact me with the details. 13.1.12 Internal Screen Error. [Writing] See above. 13.1.13 Out of memory! When this error appears, it means that for some reason, Sentry didn't have enough memory to run. This is extremely rare, since Sentry requires very little memory. If this error occurs, try freeing up some memory by unloading some un-needed programs, or rebooting. 13.1.14 Registration Error - Program Aborted! Someone (probably you) has tried unsuccessfully to change the registration information. Very naughty, but if you want to fix it, simply restore Sentry.exe from your backup copy. (Again, a good reason to keep a backup somewhere!) 13.1.15 This account has expired. Sorry, you're out of luck. The SuperUser(s) have set your account to expire, and so it has. If you ARE the SuperUser, silly you (you shouldn't let your own account expire!). In that case, you will have to restore the Sentry.exe from a backup, and make the necessary changes to get your system running. 13.1.16 Cannot allocate memory for environment block This is another DOS environment error. Make sure your environment is set up correctly and has sufficient free memory allocated to it. 13.1.17 Error Opening Message File. This error indicates that the message file cannot be opened. Ensure that your initialization setting for the message file is correct, and that the file is not read-only. 13.1.18 Error Opening System Files! This is an error during installation. If this error occurs, make sure that your AUTOEXEC.BAT and CONFIG.SYS files are readable, if they exist. 13.1.19 Error opening protected file! This error may occur when protecting a file from the SuperUser menu. Make sure the file you indicate to protect is readable. 13.1.20 Error opening Sentry.ins! This error occurs when Sentry cannot find the file containing the descriptions for the initialization settings. Make sure that the file Sentry.ins is in the same directory as the Sentry.exe file. 13.2 Other problems When I run Sentry, is displays a warning saying I have newer/older initialization settings. A: You should probably get the latest version of Sentry (see section 11.3 for info on obtaining the latest version). Replace all your current files with the files you retrieve. This warning may not be a problem in itself, however it is not a good idea to use initialization settings from a different version. I get a warning about users being tampered with in the log file. A: Someone has been tampering with your users (obviously). They thought they could change the SuperUser access on your system, but really couldn't. The only side effect of this is that some users may appear to have SuperUser access when they don't (and vice-versa) when you view them from the SuperUser menu. The users' actual access has not changed. To remedy this situation, you can get the user to enter another password (this can easily be done by expiring their current password). As soon as the new password is entered, the problem will disappear. I can't log in at all. A: Are you a user on the system? Are your initialization settings set up correctly? Have you run the install program? I can't log in as a SuperUser. A: Did you give yourself SuperUser access? Are you remembering to hold down CTRL when you hit enter? My account information is corrupt or deleted. A: Pray you kept a backup somewhere. At the very least, you should have the install program sent with Sentry. In that case, re-install, and log in as Sentry. Since Sentry is initially a SuperUser, you can re-create your users (don't forget to delete the Sentry user when you are finished!). I can't create a c:\Sentry directory on my drive. A: If you are using MS-DOS's UNDELETE program, it may create a directory called "Sentry" off of your root directory. This directory is hidden, and can only be seen with the "dir /a" command. (This only occurs if you are using the "delete sentry" mode). Possible fixes are to stop using "delete sentry" mode, or to create your Sentry directory as something else (eg: c:\Sentry2, c:\Secur\Sentry, etc etc). 14.0 Standard Disclaimer ======================== Inexperienced users should take care with this program, as you may lock yourself out of your computer! If you feel you want to use it, but don't feel completely confident, leave a "back door" for you to use. (IE: don't implement all of the security measures listed in "Securing Your Computer"), so that if you DO get locked out, you can still get in somehow. Once you are satisfied that all is well, lock up the back door too. Please read the document "LICENSE.TXT" included with this software for the entire licensing agreement. 15.0 Contact Information ======================== I would greatly appreciate any comments you might have about this program (either positive or negative). If you encounter any problems, or have a suggestion for making Sentry better, please let me know, and I'll try to put it in a future release. I look forward to hearing from you. You can contact me via e-mail at Mike.Bobbitt@AcadiaU.Ca and I will reply as quickly as I can. If you do not have internet access, you can contact me via surface mail at: NightShade Computing P.O. Box 1336 Wolfville, Nova Scotia B0P 1X0 CANADA 16.0 Credits ============ My thanks go out to these people: Mark Saarinen for the encryption algorithm. Richard Brittain for use of his DOS environment variable code. D.J. Houghton and Rob Coombs for testing and advising during the design phase. Dexter J. Caldwell for suggestions on various options, as well as the "template" methodology for protected files. L.D. Best for suggestions, comments and bug reports, as well as detailed explanations of test situations. L.D. has provided many good ideas and useful comments with respect to Sentry, and has assisted greatly in "fine tuning" many features such as file protection. Bret Jacobsen for finding some serious errors in the first release, as well as continually making suggestions for improvement. Bret has given invaluable assistance in the development of Sentry. ...And my wife for listening to me talk incessantly about it.