nicolasmesa / print-spooler Goto Github PK

Print Spooler
By: Nicolas Mesa (nm2805)



This project produces three commands that are supposed to simulate a Print Spooler:

1. addqueue: receives paths to different files as its arguments and, after performing some validations, copies each file to a protected directory. The output of the program provides a summary for each file, displaying the file name and a "Y" if the file was added successfully to the queue or an "X" followed by a description of the error if it could not be added.

Example: addqueue file01 file02 file03


2. showqueue: displays the current print queue with some information about the files. This information includes the file name, the id of the user that made the request to print the file, the date and time that the file was added and a unique identifier for the file.

Example: showqueue


3. rmqueue: receives the ids of different files that currently reside in the queue, performs some validations and deletes each file from the protected directory. The output provides a summary for each file id displaying the file id and a "Y" if the deletion was successful or an "X" followed by an error message if the file could not be deleted.

Example: rmqueue 1 3 2



Example:

$ ls -al
total 32
drwxr-xr-x 2 root root 4096 Nov 10 20:20 .
drwxr-xr-x 4 root root 4096 Nov 10 20:14 ..
-rw-r--r-- 1 root root    7 Nov 10 13:57 file01
-rw-r--r-- 1 root root    7 Nov 10 13:57 file02
-rw-r--r-- 1 root root    7 Nov 10 13:57 file03
-rw-r--r-- 1 root root    7 Nov 10 13:57 file04
-rw-r--r-- 1 root root    7 Nov 10 13:57 file05
-rw------- 1 root root    8 Nov 10 20:20 file06
$ showqueue
1 0 2015-11-10_20:21 1
$ addqueue file01 file02 file03 file04 file05 file06 file07
file01: Y 2
file02: Y 3
file03: Y 4
file04: Y 5
file05: Y 6
file06: X Permission denied
file07: X No such file or directory
$ showqueue
1 0 2015-11-10_20:21 1
2 1003 2015-11-10_20:22 2
3 1003 2015-11-10_20:22 3
4 1003 2015-11-10_20:22 4
5 1003 2015-11-10_20:22 5
6 1003 2015-11-10_20:22 6
$ rmqueue 1 2 3 4 6 7
1: X Can't remove this file, permission denied
2: Y
3: Y
4: Y
6: Y
7: X File not found
$ showqueue
1 0 2015-11-10_20:21 1
5 1003 2015-11-10_20:22 5
$ exit


Make

Building

To build just run "make" or "make build" and the commands will be compiled.


Installation

To install just run the command "make install" as root. This will build the commands, copy them to the /bin folder, set the right permissions, add the setUID permission and create the protected directories with the right permissions.


Uninstalling

To uninstall just type the command "make uninstall"


Testing

To run the tests type the command "make test". This will do the same thing as running "make uninstall", then "make install", then the tests are run then, "make uninstall" is called again and finally, "make install" is called


Cleaning

To clean the directory just type "make clean" and all of the object files and commands will be removed from the source code directory.


Internals

Spooler User: "user01" is the user that is the owner of the commands in /bin and also the owner of the protected directories. The commands run as this user and group.

Protected directories: The main protected directory is located at "/home/user01/spooler". Inside this directory, other two directories reside: "config" and "printer". The "config" directory starts empty but after files are added to the queue, contains a "config" file and a "file-list" file. The "printer" directory contains the files that are added to the queue. All of these directories and files belong to the user "user01".


Project specification:

For this assignment, you will implement something that looks a lot
like a print spooler.  You will run these commands on a virtual
machine; see the <a href="vmware.pd">instructions</a>.

The print spooler itself will run as some other userid.  You must
test it as one or more other users.

Briefly, you must implement three commands, "addqueue", "showqueue",
and "rmqueue".  All are privileged.  "addqueue' takes a set of file
names as arguments, and copies the contents of those files to some
protected directory.  "showqueue" lists the queued files: some
arbitrary name (*not* the original file name, but a number is fine),
the owner (the userid who made the request), the time and date it
was added, and some sort of unique identifier.  This unique identifier
may or may not be the same as the file name; that's entirely up to
you.  "rmqueue" takes a list of unique identifiers and deletes those
entries from the queue.  Only the user who added a file to the queue
may delete it.

You do not need to worry about race conditions for generating file
names or unique identifiers.  That is, there is no need to lock any
resource for the counter.

You may use setuid or message-passing.  If you use the latter, it's
perfectly ok to start some daemons manually.

You must use at least three userids: one for the protected resource,
and at least two test userids.  That latter is needed to test if
one user can delete the other's files.

There must not be any way to look at or change the spool directory
or its contents except through these commands.