Rapid Application Development toolkit for building Administrative Web Applications

The RADICORE Security Model

By Tony Marston

25th April 2006
Amended 1st December 2009

Introduction

1. Authentication

2. Security Policy

3. Authorisation Manager

4. Audit Log Manager

5. System Manager

Introduction

Compliance with various security requirements is essential if an application is to be taken seriously by prospective clients. Having no security at all can lead to delicate information falling into the wrong hands, or allowing delicate information to be modified or destroyed by unauthorised personnel. On the other hand, too much security can prevent an authorised person from completing a legitimate task. Clearly some sort of balance is necessary, and each decision, whether to employ or not employ a particular security mechanism, may benefit from explanation and justification.

The purpose of this document is to identify what security features either do or do not exist within RADICORE, and to give explanations where necessary. It should be noted that RADICORE is a web application that uses the stateless HTTP protocol, which means that certain options which are available to traditional desktop applications are inapplicable.

1. Authentication

1.1 The system has to ensure that login of a user is always possible only with authentication.

The RADICORE system forces every user to navigate through a login screen which requires the input of a user_id and a password. These will be validated against the contents of the USER database table, and only if there is a match will the user be allowed to proceed. If either of these inputs is wrong a simple "security violation" message will be issued which does not identify which of the inputs was wrong.

Internal password authentication may be replaced with external authentication by using either a RADIUS or an LDAP server. These servers may allow passwords to be either static or supplied by a One Time Password (OTP) generator in order to implement Two Factor Authentication (2FA), also known as Two Token Authentication (TTA). This password generator, which may be either a piece of hardware or software, will generate random passwords which can be used only once.

A user's login rights can also be restricted to a particular date range by means of a START_DATE and END_DATE on the user's profile. If the user attempts to login outside of this period then a suitable error message will be issued.

There is also provision for a user's login rights to be temporarily disabled by an administrator by setting an IS_DISABLED flag on the user's profile. All rights can be restored simply by unsetting this flag.

1.2 Logging out

RADICORE provides the following methods for logging out:

• Using the "logout" hyperlink at the top right of each screen. This will erase the data for current session and return the user to the logon screen.
• Using the "logout (all)" hyperlink at the top right of each screen. This will erase the data for all sessions which may be active on that client device and return the user to the logon screen.
• Automatic logout after session timeout. If a client has no activity within the session timeout period (which is configurable) then the data for that expired session will be erased. Any further attempts to continue that session will cause the login screen to be displayed.

Note 1: It is not possible to return the client to the logon screen until the client issues a request as the web server cannot initiate any activity on the client, it can only send a response in reply to a request from the client.

Note 2: It is not possible to force the client to send a "logout" request to the server. The client may terminate the web browser at any time without sending any notification to the server.

Note 3: It is not possible to prompt the user to save any pending changes as the web application is totally unaware of any activity on the client until the client issues a request.

1.3 Only one access by any user at any one time

It may be a requirement in some systems to ensure that the same user is not logged in from multiple locations, and for a second login to automatically cancel an earlier session, but that is not implemented in RADICORE. Special facilities have been built into RADICORE to allow a user to open multiple sessions on the same client as this is a legitimate method of working. It is only possible to limit these multiple sessions to the same device provided that the device has a static IP address. See Restrict access to authorised devices for details.

1.4 Traffic overload protection

It may be a requirement in some systems to ensure that the system does not crash because of too many users, but that is not practical in a web application:

• Although a user may appear to be logged on he/she may actually have stopped using the application without sending a "logout" request, therefore the count of logged on users is unreliable.
• A web application is not limited by the current number of sessions but by the number of concurrent requests. Each client session only uses resources on the server when responding to a request, and once a response has been issued those resources are immediately freed and made available to service requests from other clients. This means that although a server may only be able to respond to a certain number of requests within each second, the total number of active client sessions may exceed this number as there is usually a delay between a client receiving a response and sending out the next request.

1.5 Session time recording

It may be a requirement in some systems to record the start time, end time and duration of each user session, but as a session can end without the server receiving a "logout" request this is not completely practicable. However, all login attempts, whether successful or unsuccessful, are logged, and all logout requests, when received, are also logged.

2. Security Policy

2.1 Each user must have a unique id and password

Although RADICORE forces each user to have a unique identity, it does not force each user to have a unique password. This is because each user password is encrypted with a different key, which means that it would not be possible to perform a lookup on a particular password without first decrypting all the existing passwords. Besides, what benefit comes from having unique passwords? A password on its own is nothing, it is only the combination of user_id and password that has any significance, and not every password is valid with every user_id.

2.2 Password changes must be confirmed

When changing their passwords, users must retype them in order to confirm them in order to avoid spelling mistakes or typing errors which would render their passwords as ineffective. Any mismatches must be cleared before a password change can be put into effect.

2.3 Passwords Format Rules

The system must allow passwords to contain both letters and numbers, and to distinguish between upper case and lower case.

RADICORE allows the system administrator to define a valid format for new passwords by means of the following specifications:

• A minimum number of lower case letters.
• A minimum number of upper case letters.
• A minimum number of numeric digits.

These alphanumeric characters can appear in any order as it is only their number which is checked.

These formatting rules are enforced only when passwords are being changed, not when being entered in the login screen.

2.4 Password Length

It must be possible for a system administrator to define a minimum length for new passwords. This can be anywhere between 1 character and the maximum size (currently 16 characters). This rule is enforced only when passwords are being changed, not when being entered in the login screen.

2.5 Password Login Attempts

To help protect against denial of service attacks the system must have some sort of lock-out mechanism after a predefined number of failed login attempts. RADICORE has the following features:

• Each failed login attempt is recorded in a separate database table showing the date, time, IP address, user_id and failed password.
• After each failed login attempt the system will pause before sending a response to the client. The length of this pause will increase with each failure.
• After a predefined number of failed attempts (where this number is configurable by the system administrator) the user_id which is being used will be marked as disabled, thus preventing it from being used even if the next attempt provided the correct password. This "is_disabled" flag can only be unset by a system administrator.

2.6 Secure Password Storage

The system must ensure that all passwords are encrypted before being stored in the database. Also, when comparing passwords the system must encrypt the input password instead of decrypting the actual password so that a plain-text version of the password is never passed over the network.

It may be a requirement in some systems to use one-way (i.e. non-reversible) password encryption in the belief that this is more secure, but this is a false assumption. It is possible for a determined attacker to break any encryption algorithm, one-way or not, so the only defence is to use an algorithm which requires so many resources to break that it is not worth the effort.

The algorithm employed within RADICORE is reversible, but the encryption process requires a separate customisable key. Even if an attacker knew the algorithm he would have to know the key that was used during the encryption process in order to decrypt it.

The encryption algorithm employed within RADICORE does not use simple character substitution but progressive substitution, which means that if the same character appears more than once in the input string its encrypted equivalent in the output string will not be the same.

Having a reversible (two-way) encryption process does mean that the settings (algorithm or key) can be changed at any time without losing the current password values as known by the users. Simply decrypt all passwords, change the settings, then encrypt all the passwords again using the new settings.

2.7 Login Using Secure Password

The system must ensure that the password that a user types into the login screen is encrypted before being transmitted over the network. This will ensure that an eavesdropper does not have access to a plain text version of any password.

RADICORE achieves this by ensuring that each screen which requires the user to enter a password is transmitted using SSL (Secure Socket Layer) via the HTTPS protocol. This can be verified by seeing the characters HTTPS:// at the start of the URL, not the unsecure HTTP://

2.8 Forgotten Passwords

If a user forgets his/her password then there should be a method of retrieving it without requiring the intervention of an administrator.

RADICORE achieves this by supplying a "recover password" link on the login screen which will activate a form into which the user can enter his/her e-mail address. This address is used to locate the user's details in the MENU database, then the password is e-mailed to this address. The user can retrieve this message from his/her e-mail inbox and use the details to gain access to the system.

2.9 Password Change process - User Initiated

The system must allow the user to change his/her password at any time.

RADICORE achieves this in the following ways:

• After logging on to the system using the current password every user has access to a "Change Password" function.
• This function will ask the user for the current password, then ask for the new password to be entered into two separate fields to avoid any mis-typing. The two versions of the new password must match.
• The new password cannot be the same as the old password, and it must conform to the system's formatting rules.
• The new password is recorded in the user's details, and will be required in all future logon attempts.
• The fact that the password has changed will be written to the audit log, but the actual value will not be shown.

2.10 Password Change process - System Initiated

The system must allow the system administrator to define an interval after which the password must be changed.

RADICORE achieves this in the following ways:

• The system administrator may configure the system to require password changes after an interval which may be either:
  • A number of days (irrespective of the number of logons).
  • A number of logons (irrespective of the number of days).
• After this interval has elapsed the user will be forced to change his/her password. The user is allowed to pass through the logon screen with the current password, but will immediately be presented with the "Change Password" screen (see previous section). This screen cannot be bypassed, and must be completed before the user will be allowed to continue.
• There is also the option for the system administrator to define a warning period to indicate to user's that a change in their password is becoming imminent. This is simply a number which will be interpreted as either a number of days or a number of logons, whichever is appropriate. This will cause a suitable warning message to appear on the first screen which appears immediately after the login screen. The user may elect to change his/her password immediately, or may wait until forced to by the system. When the password is changed the counter/date will be reset so that a new interval will start.

2.11 Password Change - Check Against Previous Passwords

It may be a requirement in some systems to remember a selected number of previous passwords for each user so that a new password for the same user is not on this list, but this facility is not available in RADICORE. Currently the only check is that the proposed password is not the same as the existing password.

2.12 Password Change - Check Against Reserved Words

It may be a requirement in some systems to check proposed passwords against a list of reserved words so that common words, or words which may be easy to guess, are not used.

RADICORE does not do this as the Formatting Rules give the system administrator the ability to define patterns which automatically eliminate common words.

2.13 Deactivation only by an Administrator

User accounts can only be de-activated by a system administrator.

In RADICORE the ability to de-activate or modify user accounts is by default given only to system administrators. There are two ways in which an account can be de-activated:

1. Set the END_DATE field to the last day of that person's employment. Any attempt to use that user's login after this date will automatically be rejected by the system.
2. Set the IS_DISABLED to YES. This will immediately prevent any and all future logins by that user, but it will not cancel any current session that the user may have.

Whichever method is chosen will, of course, be recorded in the system's audit log, as will any failed logon attempts.

2.14 Auto-Login and Auto-Complete of User Names and Passwords

The system has to ensure that it will be possible for customers to decide whether they want to enable/disable the auto-complete feature for user names and passwords.

This is an optional feature of the web browser and cannot be modified by the application software which runs on the server.

RADICORE does not have an auto-logon facility, therefore everyone must go though the login screen.

3. Authorisation Manager

3.1 Role Based Access Control - Function Level

A system may have hundreds of users and hundreds of functions, but not all users may be allowed to access all functions. The system must therefore have some method by which a user's access to functions can be defined and limited, and all access attempts must be verified against this list.

RADICORE achieves this by having all information regarding functions, users and access control maintained in a central database. The functions to maintain the contents of this database are, by default, only accessible by a system administrator. The structure of this database is as follows:

• TASK - this table holds details of each function (task, or user transaction). This information includes configurable options which are given to the unction when it is executed.
• USER - this table holds details of each user who is allowed to access the system. This information includes the user's current password. Each USER belongs to one ROLE
• ROLE - this table is a method of allocating users to groups so that all users within the same group can share the same security provisions without having to define them individually for each user.
• ROLE-TASK - this table is used to signify if a TASK can be accessed by USERs of a particular ROLE. If a record exists in this table with a particular combination of ROLE_ID and TASK_ID then access is permitted. The absence of a record with a particular combination of ROLE_ID and TASK_ID means that access is denied. There is n concept of groups of ROLEs or groups of TASKs - it is strictly a one-to-one relationship.

RADICORE also employs a dynamic menu system in which all menu pages are maintained within the database. When a user selects a menu the details are retrieved from the database and compared against the ROLE-TASK table so that any functions which are not accessible by the user are automatically filtered out before the menu options are displayed.

This method therefore has two levels of functionality:

• The user can only "see" options to which they actually have access, so there is little chance of a user seeing an option and selecting it, only to be informed afterwards that the option cannot be accessed.
• If the user tries to select an inaccessible option, for example by manipulating the URL, this will not succeed because the system will re-verify authorisation when the function is activated.

3.2 Role Based Access Control - Field Level

The system should also handle access control at the field level. Normally all fields are available, but there should be a facility to make certain fields either read-only or hidden to certain roles.

RADICORE achieves this by allowing an administrator to define the following on the central database:

• TASK-FIELD - this table holds for each task (function) a list of fields where additional access control may be defined.
• ROLE-TASK-FIELD - this table holds information where access to particular FIELDS within particular TASKS may deviate from the normal. No entry means FULL access (i.e. read and write). Other options may be NOEDIT (read-only) or HIDDEN (invisible).

Note: This facility is not provided by any mechanism within the database as everyone shares the same database login, without which the pooling of persistent connections would not be possible. It is instead provided completely within the application. This is made easier by the fact that each HTML page is built completely from scratch each time rather than being taken from some pre-compiled definition. When building the page easy it is therefore a straightforward process to make any HTML control read-only instead of writable, or not to include it in the output at all.

3.3 Row Level Security (RLS)

It it possible for the same database table(s) to hold data for several different customer accounts, but where users within an account can only access records (rows) which belong to that account. Account access can be turned on for any database table simply by adding a column called rdcaccount_id. The features of the RADICORE implementation are:

• There is a database table which lists all the available accounts, with the value '1' reserved for shared access.
• Each user can be assigned to one of these accounts, which limits his access to data which belongs to that account, plus any shared data (where the rdcaccount_id column has the value '1', or the table does not contain the rdcaccount_id column).
• Database tables which do not contain the rdcaccount_id column are shared, not private, therefore can be viewed and modified by users within any account.
• Database tables which contain the rdcaccount_id column may have a mixture of shared and private data:
  • Shared data has the value '1' in the rdcaccount_id column.
  • Private data has a value greater than '1' in the rdcaccount_id column.
• Users may or may not be assigned to a particular account, which has the following effect:
  • Users without a value for rdcaccount_id can only access shared data.
  • Users with a value for rdcaccount_id can only access data which belongs to that account, plus any shared data.

This topic is discussed in greater detail in Implementing Virtual Private Databases.

3.4 Prevention of Unauthorised Transactions

The system must have control mechanisms that prevent the accessing of functions outside the predefined access path, based on the access rights given to users. Unauthorised users must not be able to access, change or otherwise corrupt the data within the system.

RADICORE deals with this in the following ways:

• Nobody can start a new session without passing through the logon screen. Even if someone has a URL which activates a function, unless an identifier for an authorised session is also given this will cause the start of a new session which is automatically unauthorised.
• It is not possible to pass through the login screen without supplying a valid user id and the current password for that user id. All invalid login attempts will be logged, and if the same user id is supplied in a failed login attempt beyond a predefined number of times that user id will be disabled from all further login attempts, regardless of the validity of any password. Any user id thus disabled can only be enabled by the intervention of a supervisor.
• Even if someone does gain access to the system, they will only have access to those functions which have specifically been granted for that user. Functions which are not accessible will have no visible means to be selected, and cannot be accessed by falsifying a URL as permission is also checked at the start of each function.

3.5 Global Access Override

The system must have provision for granting automatic access to every function within the system without having to rebuild the access control list. This facility is required for system administrators, not everyday users.

RADICORE achieves this by having a GLOBAL_ACCESS switch on the ROLE record. If this switch is turned ON then all users with this role have global access. If this switch is turned OFF then access to each function is disabled until it is specifically enabled.

3.6 Restrict access to authorised devices

It may be required to restrict system access to authorised client devices. The following options may be required:

• A person may only be able to access the system from his work computer.
• He may be allowed to access the system from both his work and home computer.
• There may be a task he can access at work, but not at home.

With web applications each client device is recognised by its IP address. RADICORE implements this feature by maintaining a list of valid IP addresses for each user and each task. By default these lists are empty and this feature is turned off, but it may be turned on at any time by creating a non-empty list. Any number of IP address entries can be specified for each user and each task.

User access is checked in the logon screen. Task access is checked whenever a task is requested, either through a menu button or a navigation button.

1. If there are no IP address entries for a user then there are no restrictions on that user, and the user may access the system from any client device. If there are any entries then access is only permitted from a client device with an address which is in that list of entries.
2. If there are no IP address entries for a task then there are no restrictions on that task, and the task may be accessed from any client device. If there are any entries then access is only permitted from a client device with an address which is in that list of entries.

NOTE: This feature is only applicable to those devices which have static (fixed) addresses. In situations where IP addresses are assigned dynamically, such as through a DCHP server, or where they are shared or masked, such as through a proxy server, this feature will not work as expected.

4. Audit Log Manager

4.1 Permanent Audit Log Records

Data recorded in the Audit database may never be deleted or overwritten by anybody.

The RADICORE framework has facilities to write entries to the Audit database, and to view Audit records using a standard set of online screens, but there are no facilities which allow the user to modify or delete any entries.

This security requirement may be further enhanced by making use of MySQL's ARCHIVE storage engine which has two significant features:

1. All data is stored in compressed format, thus taking up far less space on disk.
2. It is physically impossible, even with SQL statements, to modify or delete any records.

4.2 Every database change must be capable of being audited

The system must have the capability of logging changes to all database tables, and there should also be a standard set of screens to search through and view the contents of the audit data.

The RADICORE framework comes with a ready-made AUDIT database, functions to write to the database and functions to search through and view the contents of the database. All the system administrator has to do to enable the logging of changes to any database table is to visit the Update Table screen in the Data Dictionary and turn on the "Audit Logging" switch, then export the details so that they can be used by the application.

When audit logging has been turned on for any database table this will by default include every column in that table. The logging of a particular column can be turned off by visiting the Update Column screen in the Data Dictionary and switching the "No Audit" flag to YES, then export the details so that they can be used by the application.

The following details are written to the AUDIT database and are viewable using the online screen enquiry:

• The data and time of the change.
• The identity of the person making the change.
• The function used to make the change.
• The database name, table name and column name being changed.
• Both the "before" and after" values for each column that was changed.

Th AUDIT database used within RADICORE has a fixed structure which can deal with deal with any number of application tables. This has the following advantages:

• New database tables can be included in the logging mechanism without requiring any changes to the structure of the AUDIT database.
• Existing database tables which are being logged can have their structure changed without requiring any changes to the structure of the AUDIT database.
• Because the structure of the AUDIT database is fixed then the screens to search and view the contents of the AUDIT database can also be fixed. Thus one small set of screens can be used to view any data in the AUDIT database.

5. System Manager

5.1 Automatic Incident Reporting

The system has to ensure that if there is an error during a user session that details of the error are automatically captured and made available to the system administrator. This removes the responsibility from the user who may not be aware of the procedure for reporting such incidents, or may not provide enough information.

In the RADICORE framework this is achieved by passing all errors through a standard error handler which performs the following:

• Displays a summary of the error in the client browser.
• Writes full details to a log file with the name errorlog.html which can be viewed through any browser.
• Writes full details in an e-mail message which is sent to the site administrator.

© Tony Marston
25th April 2006

http://www.tonymarston.net
http://www.radicore.org

Amendment history: