You are to implement a simple file system" with login authentication and access control. Specifically:

Construct a hash/salt/shadow based user/password creation system.
Construct a hash/salt/shadow based user authentication system.
Construct an associated file system, into which a user can log. Files can be created, read from, written to, but only in accordance with a three-level access control model.

The levels of the three-level access control model are 0, 1 and 2. 0 is dominated by 1 and 2, and 1 is dominated by 2.

You do not need to have an actual file system, simply an internal collection of records at the levels specified.

Although in practice we would use a client/server system, here we will simply simulate the transmission process. You can implement the program in C++, C or Java.

Use MD5.

You need to provide compilation instructions for your code that are compliant with conditions set by the tutor.

The initialisation details

Your program will, initially, need blank files salt.txt and shadow.txt.

Running your FileSystem with the instruction
FileSystem -i
runs the hash/salt/shadow based user/password creation system. This program should prompt for a username, something like...

Username: Bob

Check if the username exists already. If it does, terminate the program with an appropriate notification to the user. If it doesn't, request a password with something
like ...
Password: ........
Confirm Password: ........
Assuming the passwords are the same, we make a final request of the user, something like ...

User clearance (0 or 1 or 2): 1

Once we have this information we can modify the salt.txt and shadow.txt files to include this user. To salt.txt we add a line, with a generic example and a specific one for user Bob given here:

Bob:38475722
Username:Salt

where Salt is a randomly chosen string of 8 digits. The random generator should be seeded using time() and a secret key taken from the file Secret.txt. That file should be in plaintext and readable.

We also add a line to shadow.txt, with a generic example and a specific one for user

Bob given here:
Bob:dd2da44f4437d529a80809932cb3da83:0
Username:PassSaltHash:SecurityClearance

PassSaltHash is generated as the MD5 hash of the concatentation of the user's password with the salt, For example if the Password is "alphabet" and the Salt is "12345678", we would pass "alphabet12345678" to the MD5 function.

The file salt.txt is nominally associated with the client, while the file shadow.txt is nominally associated with the server, although here both the client and server are in the same program.

Logging in
Running FileSystem with no arguments will allow a user to try and log in to the file system.

Username: Bob
Password: ........

The "client" part checks if the Username is listed in the file salt.txt. If the Username is in the file then their salt value is retrieved and the PassSaltHash is generated. A message should be displayed to indicate that the salt has been retrieved.

Bob found in salt.txt
salt retrieved: Salt
hashing ...
hash value: PassSaltHash

The "server" part should now compare the PassSaltHash value with that in the file shadow.txt. If salt.txt doesn't contain an entry for the Username, or if the information in shadow.txt doesn't match the transmitted information, FileSystem should stop with appropriate error messages.

If the shadow.txt information matches, the clearance of the user is reported, and authentication is reported to be complete.

Authentication for user Bob complete.
The clearance for Bob is 1.

Once logged in ...
A list of allowed actions is now displayed
Options: (C)reate, (R)ead, (W)rite, (L)ist, (S)ave or (E)xit. (*****)
The C option will result in a request for filename and classification, from the client.

Filename: alpha
Security level (0 or 1 or 2): 0

The program should maintain a list of "files" as internal entries. If the passed file doesn't exist, it's name and classification should be added to the list. If the passed file does exist an appropriate message should be displayed and the client should re-display the menu (*****).

The R and W choices each result in a request for a filename.

Filename: alpha

Again a check is made as to whether the file exists. If the file doesn't exist an appropriate error message should be provided and the menu (*****) should be re-displayed. If the file does exist, a message informing success or failure will be displayed. Success or failure is determined by the relative clearance of the user and the classification of the file they are trying to access, in accordance with the ss-property and the star-property of the Bell-LaPadula model. Subsequently the menu (*****) should be re-displayed.

The L option lists all files in the FileServer records. The S option saves all the data to a file Files.store.

This file should always be loaded if it is available when FileServer starts without the -i argument.

The E option should exit the FileServer, after checking with the user:

Shut down the FileServer? (Y)es or (N)o

If FileServer is to be shut down, it should firstly display a list of files within it's records.

NOTE: When your program starts, before bringing up a prompt, it should report a test output of the MD5. You should call your MD5 with the string "This is a test".

MD5 ("This is a test") = ce114e4501d2f4e2dcea3e17b546f339