System Architecture

Implementation Requirements

To satisfy the needs identified in the requirement analysis, a multi-tiered approach to the design is preferred. In particular, the components that effect the necessary changes to the system configuration based on actions taken within the UMS should be isolated from the rest of the system. In this way, a migration to a new server or a new operating system release will require changes to these components without incurring the complete system rewrite that the current migration entails.

At the same time, where multiple procedures require the same function, a list of shared libraries should encapsulate these functions for this same reason. In this way, functions and services specific to the current version of RedHat (such as user authentication) can easily be altered to take into account new features or services of future releases.

However, to leverage volunteer resources, the tasks of developing the web interface (a task best suited to web developers) are separated from the tasks of developing back-end functionality (a task for formal PERL programmers). This distinction has the added benefit of allowing the web interface to be updated to a new corporate look in the future without affecting the application logic.

Implementation Structure

As depicted in Figure 1 below, the develop effort can be broken into a number of conceptual parts:

Those volunteers knowledgeable in HTML will primarily develop the Web Interface. Skills for these people should include HTML forms, graphic design and layout and site navigation expertise. A common visual theme should predominate these pieces. As well, these people will develop HTML snippets that will be incorporated by CGI Application developers when a CGI application needs to return a complete web page to the client.
CGI Applications will leverage people knowledgeable in PERL. These individuals should understand CGI applications, be conversant in PERL and preferably have some knowledge of SQL and how to embed database calls within PERL scripts.
Shared Libraries will require people very knowledgeable in PERL. Ideally, these libraries should use PERL or Object-Oriented PERL objects for functionality such as maintaining persistent user sessions.
The Relational Database will use MySQL. If CGI application developers are not sufficiently conversant to embed SQL calls within their applications, an SQL-PERL specialist may perform this specialized function.
The System Configuration APIs will likely be written in Shell script or compiled C. They will require developers with the highest skills and most likely root access to the host machine.

Implementation Components

Web Interface

Before development of the Web Interface, a Visual Identity Guide (VIG) will be required. This guide will contain the basic style elements to ensure that all pages on the User Interface are visually and thematically consistent with each other and with the general GPFN web site.

The Visual Identity Guide will also contain directives concerning how users will navigate around the pages as well as how linkages outside the UMS pages back to the GPFN general web site will be incorporated.

In addition to the VIG, web developers will require a common set of resources such as icons, navigation bar graphics, template files and HTML Style. Developing the VIG and the other components will be the duty of the GPFN webmaster.

System Configuration APIs

All System Configuration APIs must be intrinsically distrustful of their calling functions. This prevents a potential malefactor from directly calling these programs while masquerading as coming from a valid user. Such a masquerade could be successful if the API did not verify the authenticity of the caller on its own.

This distrust is managed by creating a virtual domain within the webserver for the UMS. The virtual domain along with its libraries and system configuration APIs will run under a distinct set of user and group permissions.

Password Change

The Password Change API is responsible to ensure that the username and old password successfully authenticate the user. Only if the user is verified in this way is the new password checked for hardness according to the system configuration (normally using the cracklib libraries), then using a suid program, this API effects the password change on the system.

Mail Forwarding

The Mail Forwarding API authenticates the user and if authenticated, allows the user to review, change or set the contents of their home .forward file.

Mail Filtering

The Mail Filtering API can perform many functions. For the purpose of this application, it copies a system .procmailrc template file into the user’s home account, thus effecting spam control. Again, the API must authenticate the user before effecting these changes.

Reviewing Disk Quota

The Disk Quota API authenticates the user and once authenticated, returns the user’s current quota values for display back to the user via a CGI script.

Shared Libraries

The Shared Library functions include all functions and methods used by two or more components of the system. It will include user authentication and managing of session credentials.

These functions will involve setting and retrieving cookies on the user’s browser, writing to and retrieving session values from the relational database, and managing Object Oriented PERL constructs and entities.

User Authentication

User authentication involves comparing the username supplied on a web form with the existence of the username on the system then comparing the password supplied on the form with the password maintained for the account on the system.

On a modern Linux system, Pluggable Authentication Modules, or PAM, supports user PAM supported libraries and applications are available on the Internet to be used as a template in constructing a custom authentication package.

For the UMS, a web form will request a user to input his username and password. PAM will then authenticate this user. If the user is successfully authenticated, a session token will be created for the user. This token will have an expiry date one hour into the future.

Authenticating GPFN volunteers is a slightly different matter. A GPFN volunteer is not simply a user, but rather a user with increased permissions to the system this system may not be suitable for volunteers. As well, volunteers may not want to use their system password to authenticate themselves to the UMS. Instead, they may want to use a password specific to the UMS.

For this reason, authenticating GPFN volunteers will use the htaccess and htpasswd functions inherent in the Apache web server. Web pages and CGI scripts specific to volunteers will be in a separate directory under which the web server will apply access controls.

Session Credentials

Once the system authenticates a user, the libraries will have to manage session persistence for the user. To effect this persistence, the libraries will have their own database in the RDBMS. When a user is authenticated, a session token will be created composed of the username, the access level, the session creation timestamp, and a unique pseudo-random session ID. This token is inserted into the database and a cookie with this session token will be sent back to the user’s browser.

From then on, any calls by the user to a page on the system will return the cookie. This cookie is matched with the cookie in the database. If a match exists, then the user is the holder of a currently valid session. Any of the following conditions indicates that the session is not currently valid:

There is no corresponding session token in the database matching the session token contained in the supplied cookie.
There is no cookie containing a session token sent back by the web browser.
The session tokens for this user between the database and the sent cookie do not match.
If the timestamp of the cookie as recorded in the database exceeds the current timestamp less the expiry period of the session.

In any of these cases, the user is redirected back to the login page with the current pages’ URL stored in the QUERY_STRING for re-authentication and the session token is deleted from the database and the cookie. Once re-authenticated, the stored URL can be used to return the user to the page they were viewing before the authentication failure.

Data Flow Analysis

The system implementation involves a number of distinct yet inter-related functions. The following dataflow diagrams show the interaction flows in the system. The last dataflow case: “Manage User Account” is slated for Phases 2 and 3 of the project.

Data Flow Diagrams

Top Level Data Flow Diagram

The top-level dataflow diagram lists the interactions between the system. This interaction is further exploded for each dataflow in the subsequent diagrams:

DFD 0

1. Process User Application Data Flow Diagram

Process User Application Data Flow Diagram

2. Process User Upgrade Data Flow Diagram

3. Generate Invoice Data Flow Diagram

4. Process Receipt Data Flow Diagram

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5. Manage User Account Data Flow Diagram

The Manage User Account Data Flow is slated for implementation in phases 2 and 3 of the project.

5. Manage User Account Data Flow Diagram

Web Navigation Model

The dataflow will be managed using a combination of HTML pages, Javascript functions within HTML, CGI scripts, embedded PERL within HTML, and some shell script and PERL script library functions.

To visualize the data flow as it relates to the actual structure of the web site, the following Web Navigation Flow Diagrams were prepared. Figure 2 shows the pages available through the public web space to all users and potential users. Note that while an initial applicant can make an application without any sort of authentication, a user requesting an upgrade and all other user functions require the user to be authenticated prior to performing any of these actions.

User Interactions with the System

The volunteer portion of the web site will be secured using the inherent access controls of the Apache web server. As such, no user authentication library calls are required, the processing flow is somewhat simplified.

GPFN Volunteer interations with the System

Data Model

The Data Model is intended to be a comprehensive model to support both the immediate needs of the UMS and possible future features and enhancements. Not all fields will be used in the currently scoped implementation.

Entity Relationship Diagram

Entity Relationship Model diagram

Data Dictionary

System_Default Table

System_Default Table
	Data Type	Constraints	Default Value	Description
Sys_Default_Id	Int	Primary Key		System Generated Sequential Key
Sys_Ind_Mem_Price	Float	Not NULL	24.00	Approved Annual Fee for Individual Memberships
Sys_Inst_Mem_Price	Float	Not NULL	48.00	Approved Annual Fee for Institutional Memberships
Sys_Reg_User_Price	Float	Not NULL	0.00	Approved Annual Fee for Registered Non-member users
Sys_PPP_Price	Float	Not NULL	125.00	Approved Annual Fee for Graphical PPP Access
Sys_DB_Price	Float	Not NULL		Approved Annual Fee for Database Hosting
Sys_VirtualDomain_Price	Float	Not NULL		Approved Annual Fee for Virtual Domain Hosting
Sys_TimeQuota1	Float	Not NULL	?	Maximum allowed time per single session for users
Sys_TimeQuota2	Float	Not NULL	?	Maximum allowed sessions per day for users
Sys_SSL_Price	Float	Not NULL		Approved Additional Annual Fee for SSL encrypted Virtual Domain Hosting
Sys_ListServer_Price	Float	Not NULL	100.00	Approved Annual Fee for Listserver Hosting
Sys_Next_UserId	String (5)	Not NULL		Next available UserName for Registered User accounts following the Csuite naming convention of aannn1
Sys_ExtraDiskQuota_Price	Float	Not NULL	?	Approved Annual Pricing per Mb of extra Disk Quota above the approved included amounts
Sys_Incl_Quota1	Int	Not NULL		Approved Amount of basic disk space in filesystem1
Sys_Incl_Quota2	Int	Not NULL		Approved Amount of basic disk space in filesystem2
Sys_Incl_Quota3	Int	Not NULL		Approved Amount of basic disk space in filesystem3
Sys_Quota1_Mnt	String (8)	Not NULL		Mount point on the system for quota1
Sys_Quota2_Mnt	String (8)	Not NULL		Mount point on the system for quota2
Sys_Quota3_Mnt	String (8)	Not NULL		Mount point on the system for quota3
Sys_Last_Annual_Cycle	Timestamp			The timestamp of the last generated invoice cycle. This is used to frequent duplicate invoice cycles within the same fiscal year.

User Table

User Table
Field Name	Data Type	Constraints	Default Value	Description
User_Number	Int	Primary Key		System Generated Sequential Number
User_LastName	String (30)	Not NULL		User’s Last Name
User_FirstName	String (20)	Not NULL		User’s First Name
User_Initial	String (60)			User’s Initial
User_Salutation	String (60)		One of “Mr.”, “Mrs.”, “Ms.”, “Dr.”, “Rev.”	User’s Title of Address
User_Organization	String (50)			Name of User’s Organization if user is a group or collective entity
User_Title	String (30)			Position or title of person within the organization
User_StreetAddress1	String (30)	Not NULL		User’s first line of mailing address
User_StreetAddress2	String (30)
User_City	String (30)	Not NULL
User_Province	String (30)	Not NULL
User_Country	String (30)	Not NULL
User_PostalCode	String (20)	Not NULL
User_HomePhone	String (20)
User_WorkPhone	String (20)
User_Age	Int			Really only required for users under the age of majority (so we get their parent’s signature on any application)
User_IsActive	Int	Not NULL	0	0 for not active, 1 for active, 2 for declined, 3 for expired, 4 for purged
User_Since	Timestamp	Not NULL		Date the user applied for an account
User_IsMember	Int	Not NULL	0	0 for non-member, 1 for member
User_Status_Msg	String (60)			Any Volunteer entered text string to describe issues concerning a user
User_UserName	String (16)	Not NULL		The system generated username for non- members, or the personalized username for members. This is only used during the account application process and NOT changed for users who upgrade to membership later.
User_InitialPassword	String (16)	Not NULL	Must be checked against the cracklib	The User requested initial password in MD5 hash encryption
User_EnteredBy	String (16)	Not NULL		The name of the GPFN Volunteer adding the user to the system

Member Table

Member Table
Field Name	Data Type	Constraint	Default Value	Description
User_Number	Int	Foreign Key	References User	If an entry exists in this table with User_Number, then we know that this User is also a member
Affinity_Number	String (10)	Foreign Key	References Affinity	If an entry exists in this table, then the member has a special pricing relationship with GPFN (to be implemented in Phase 4)
Member_Type	Int	Not NULL	1 or 2	1 for Individual Member, 2 for Institutional Member
Member_Since	Timestamp	Not NULL		Date on which user applied to become a member
Member_EnteredBy	String (16)	Not NULL		The name of the GPFN Volunteer adding the member to the system

Affinity Table (Phase 4)

Affinity Table (Phase 4)
Field Name	Data Type	Constraints	Default Value	Description
Affinity_Number	String (10)	Primary Key
Affinity_Name	String (50)	Not NULL		Name of group or organization entering into an affinity relationship with GPFN
Affinity_Contact_ LastName	String (30)	Not NULL		Name of contact person with the group or organization
Affinity_Contact_ FirstName	String (20)	Not NULL
Affinity_StreetAddress1	String (30)	Not NULL
Affinity_StreetAddress2	String (30)
Affinity_City	String (30)	Not NULL
Affinity_Province	String (30)	Not NULL
Affinity_Country	String (30)	Not NULL
Affinity_PostalCode	String (30)	Not NULL
Affinity_Phone	String (20)	Not NULL
Affinity_Ind_Mem_Price	Float	Not NULL	0.00	Agreed price of individual memberships under this affinity agreement
Affinity_Ind_Mem_Max_ Count	Int	Not NULL	0	Agreed maximum number of individual memberships to be sold under this affinity agreement
Affinity_PPP_Price	Float	Not NULL	0.00	Agreed price of PPP connections under this affinity agreement
Affinity_PPP_Max_Count	Int	Not NULL	0	Agreed maximum number of PPP connections to be sold under this affinity agreement
Affinity_Quota1_Amt	Int	Not NULL	0	Agreed amount of disk space in Quota space 1
Affinity_Quota2_Amt	Int	Not NULL	0	Agreed amount of disk space in Quota space 2
Affinity_Quota2_Amt	Int	Not NULL	0	Agreed amount of disk space in Quota space 2
Affinity_Quota_Max_ Count	Int	Not NULL	0	Agreed maximum number of members who benefit from the increased quota limits under this affinity
Affinity_Annual_ Agreement_Fee	Float	Not NULL	0.00	Annual Fee to be invoiced to the Affinity_Name for the terms of the affinity agreement
Affinity_EnteredBy	String (16)	Not NULL		The name of the GPFN Volunteer adding or editing the affinity to the system

Services Table

Services Table
Field Name	Data Type	Constraints	Default Value	Description
User_Number	Int	Foreign Key	References User
Service_Text_Access	Int	Not NULL	1	1 if user has access to text-only dial-up
Service_PPP_Access	Int	Not NULL	0	1 if user has access to PPP graphical dial-up
Service_WebSite	Int	Not NULL	0	1 if user has access to web space within GPFN’s public web space (not including the user’s public_html directory)
Service_Website_Path	String			The relative path from the Webserver’s document root to the directory for this members’ web space within the gpfn.ca domain.
Service_DBAccess	Int	Not NULL	0	Number of databases the user has access to on the database server
Service_Quota1	Int	Not NULL	0	Number of extra Mb of disk space the user has subscribed to on the filesystem referenced by Quota1
Service_Quota2	Int	Not NULL	0	Number of extra Mb of disk space the user has subscribed to on the filesystem referenced by Quota2
Service_Quota3	Int	Not NULL	0	Number of extra Mb of disk space the user has subscribed to on the filesystem referenced by Quota3
Service_VirtualDomain	Int	Not NULL	0	Number of virtual domains the user has on the system
Service_ VirtualDomainName	String			Registered Name of the Virtual Domain
Service_TimeQuota1	Int	NotNULL	0	Amount of extra time the user has paid to be added to the value included in Sys_TimeQuota1
Service_TimeQuota2	Int	NotNULL	0	Amount of extra time the user has paid to be added to the value included in Sys_TimeQuota2
Service_EmailAliases_ Max_Count	Int	Not NULL	0	The maximum number of e-mail aliases belonging to this user
Service_SSL	Int	Not NULL	0	The number of SSL enabled Virtual Domain web hosts for this user on the system
Service_Listserver	Int	Not NULL	0	The number of Listservers for this user on the system
Services_EnteredBy	String (16)	Not NULL		The name of the GPFN Volunteer adding or editing this service list on the system

Email_Alias Table

Email_Alias Table
Field Name	Data Type	Constraints	Default Value	Description
Alias_Id	Int	Primary Key		System Generated Incremental Number
User_Number	Int	Foreign Key	References User
Alias_GPFNAddress	String (30)	Not NULL		The GPFN address to which mail is received
Alias_ExtAddress	String (50)	Not NULL		The non-GPFN address to which mail is redirected

Invoice Table

Invoice Table
Field Name	Data Type	Constraints	Default Value	Description
Invoice_Number	Int	Primary Key		System Generated Incremental Number
User_Number	Int	Foreign Key	References User
Invoice_Date	Timestamp	Not NULL		Date on which the invoice was issued
Invoice_Medium	String (20)	Not NULL		One of “e-mail”, “paper”, “fax” or some other such descriptor of the method in which the invoice was delivered
Invoice_Amount	Float	Not NULL		The total value of the invoice
Invoice_EnteredBy	String (16)	Not NULL		The name of the GPFN Volunteer adding this invoice to the system

Invoice_Item Table

Invoice_Item Table
Field Name	Data Type	Constraints	Default Value	Description
Item_Number	Int	Primary Key		System Generated Incremental Number
Invoice_Number	Int	Foreign Key	References Invoice
User_Number	Int	Foreign Key	References User
Item_Description	String (60)	Not NULL		Description of the line item for the invoice
Item_Amount	Float	Not NULL	0.00	Amount of the line item for the invoice

Receipt Table

Receipt Table
Field Name	Data Type	Constraints	Default Value	Description
Receipt_Number	Int	Primary Key		System Generated Incremental Number
Invoice_Number	Int	Foreign Key	References Invoice
User_Number	Int	Foreign Key	References User
Receipt_Date	Timestamp	Not NULL		Date that the amount was received and processed by the volunteer
Receipt_Amount	Float	Not NULL	0.00	Amount received from the user
Receipt_Payment_Type	String (30)	Not NULL		One of “Cash”, “Cheque”, “Credit Card” or some other description
Receipt_Entered_By	String (16)	Not NULL		The name of the GPFN Volunteer adding this receipt to the system

Upgrade_Request Table

Upgrade_Request Table
Field Name	Data Type	Constraint	Default Value	Description
Upgrade_Id	Int	Primary Key		System Generated Incremental Number
Invoice_Number	Int	Foreign Key	References Invoice
User_Number	Int	Foreign_Key	References User
Upgrade_User-Ind	Int	Not NULL	0	1 if the upgrade turns a registered user into an individual member
Upgrade_User-Inst	Int	Not NULL	0	1 if the upgrade turns a registered user into an institutional member
Upgrade_Ind-Inst	Int	Not NULL	0	1 if the upgrade turns an individual into an institutional member
Upgrade_Username	String (16)			The selected username for a user upgrading to a membership from a registered user account.
Upgrade_toPPP	Int	Not NULL	0	1 if the upgrade enables PPP
Upgrade_toDB	Int	Not NULL	0	The number of Databases to be added to the User’s account
Upgrade_DBName	String			The requested name for a database on the database server.
Upgrade_Quota1	Int	Not NULL	0	Number of Mb to be added to the user’s disk quota of the filesystem referenced by Quota1
Upgrade_Quota2	Int	Not NULL	0	Number of Mb to be added to the user’s disk quota of the filesystem referenced by Quota2
Upgrade_Quota3	Int	Not NULL	0	Number of Mb to be added to the user’s disk quota of the filesystem referenced by Quota3
Upgrade_toVirtualDomain	Int	Not NULL	0	Number of Virtual Domains to add to the user
Upgrade_ VirtualDomainName	String			The requested domain for an application for a virtual domain
Upgrade_TimeQuota1	Int	Not NULL	0	Number of additional minutes to add to Sys_TimeQuota1
Upgrade_TimeQuota2	Int	Not NULL	0	Number of additional sessions to be added to Sys_TimeQuota2 for this user
Upgrade_toSSL	Int	Not NULL	0	Number of SSL enabled web hosts to be added to this client
Upgrade_toAliases	Int	Not NULL	0	Number of additional email aliases to be added to this user’s services
Upgrade_AliasExtAddress	String			e-mail address of the external service to which e-mail to the alias will be redirected
Upgrade_ AliasGPFNAddress	String			e-mail address of the GPFN address to which mail will be receive and then redirected
Upgrade_toListserver	Int	Not NULL	0	Number of additional Listservers to be added to this user’s services
Upgrade_ListserverName	String			Name of mailing list for an upgrade to Listserver.
Upgrade_ApprovedBy	String (16)	Not NULL		The name of the GPFN Volunteer approving this upgrade on the system