CS4400 Internet Applications Assignment 3: File-Server

Features

• Distributed Transparent File Access
• Security Service
• Directory Service
• Replication
• Caching
• Transactions
• Lock Service
• API Docs for services

Overview

Distributed Transparent File Access

Flat file system. Every file is shared with everyone. The client is a typical AFS client with open, close functions.

• Example - A file being updated

• Example - Open, Closing functions. Write Mode + Persisting Files

Security Service

• All traffic is encrypted.
• https between servers
• 3-Key Authentication for Client-to-Server

There are three events that are affected by this given service.

1. User Login
2. User Connect to Server-X
3. Interacting with Server-X

Event: User Login

[t1]	
User ----> Authentication Server
Request Object: {username, password} 

[t2]	
User <---- Authentication Server
Response Object: {session-key} 

Session-key is encrypted with the users password

Event: User Connect to Server-X

[t1]	
User ----> Authentication Server
	
Request Object: {username, payload: {
	identity: 'Server-X'
	}
} 

Payload is encrypted with the users session-key. This is stored on the Authentication Server and can be looked up with their username: 

[t2]	
User <---- Authentication Server

Response Object: {
	ticket:'object containing the username and session-key of the user encrypted with Server-Xs secret key,
	session-key: 'users session key'
}

The ticket is then used to interact with Server-X.

Event: Interacting with Server-X

[t1]	User ----> Server-X
			{Ticket, Payload} 

Payload is encrypted with the users session-key. The ticket contains the users session-key. Server-X can decrypt the ticket, extract the session-key and then use the extracted key to then decrypt the payload.

[t2]	User <---- Authentication Server
			{Payload}

The response payload is also encrypted with the users session-key.

Client

The client is like any AFS client, it has the following functions.

Commands	Function
afs login	Authenticates the user. Also fetches and caches all files off the server to the local disk.
afs fetch	Manually fetch and cache all files in the server to the local disk.
afs open <write|read>	Opens a new (write-only) or existing file in a given mode.
afs close <write|read>	Closes a file for a given mode. If for write, it will push the new data up to the cloud.
afs rm	Deletes a given file locally and off the server

Directory Service

Supports

1. Get a single file
2. Get all files
3. Create a file
4. Update a file
5. Locking

Lock Service

The service is integrated into the directory service. See the api above. Each time a file is opened for write, the file is then locked so no one can write to it. Once the close has been called the file has been updated, it is then unlocked. To ensure the no body writes a file that they were not supposed to the permissions of the file are changed on-disk for all groups and the server will reject any requests that don't abide by the permissions.

• Example - Locking from another users point-of-view a file is locked to another user.

Transactions Service

Transactions can be initiated with this service. Transactions are stored with info of the user who started it. The service stores files affected by the transactions in a shadow-file collection - shadow files are copies which the actions are performed on instead of the actual files themselves - no files are affected by commits of a transaction till the transaction is completed with the necessary api call.

Supports

1. Start a transaction
2. Commit to transaction
3. Delete a transaction
4. Update a file
5. Locking

Replication

Replication is integrated into the databases using Replica Sets. This provides that there is always a server.

The setup looks like this...

			[  Primary	]

 [Secondary]<-Heartbeat->[Secondary]

Writes and reads are done through the primary. In the case that the primary disconnects, a vote will be made between the secondaries and one will be elected the new primary. To make the following setup...

 [Primary]<-Heartbeat->[Secondary]

Caching

Caching is simply done by caching files locally on the clients's disk. Each time new files are fetched from the directory server the files on disk are updated.

Demo - Logging in, fetching files and caching them locally

Installation, Configuration and Running

Dependencies

• Redis server
• MongoDB
• NodeJS Note: This was built with the LTS version.

Installing

Run the following in the root directory

	npm install

Configuration

HTTPS

You'll want to run the key and cert generator, in the project directory. This will create the https certificates and private keys for each server.

	./key-generator

Redis

You'll want to set the port of your redis server inside package.json.

    "redis": {
      "port": 8080,
      "host": "yourhostname",
      "socket": "/someplace/whereever.sock"
    }

After this when running, make sure this server is running with

	redis-server /location/redis.conf

MongoDB

You'll want to set the urls to your dbs inside the package.json. Same as with redis, obviously make sure to have mongod running in the background.

Running

Now that you've everything setup, you can run the all the servers with

	npm start