You must prepare a program which would carry out some of the basic tasks accomplished by a file integrity checker such as Tripwire. In this first part of the assignment you will be dealing strictly with processing one file at a time in any operation (in task 2 you will deal with directories). The program must present the user with a menu of four choices:
1) Add a file to the integrity database,
2) Remove a file from the integrity database,
3) Check the file for changes, and
Your integrity database must be maintained as a python dictionary with nested components. Between invocations of your program, the database must be stored in a file using the pickle module. You must establish a default name for your database, but permit the user to override this name by giving a new name as a command line argument. If the database already exists, read it in. If not, then create an empty new database. The database must be represented by a nested dictionary structure that mirrors the tree-like nature of the file system. The top level dictionary represents the root directory. Its components are the files and directories contained in /, indexing by their name as a key. Any subdirectories must be represented by another dictionary, continuing recursively.
When adding a new file into the database a nested set of entries must be made in this structure (if they do not already exist) according to the full path name of the file (all filenames could be assumed to have absolute paths) by breaking it up into the directory names between slashes. The final entry for the file must be a computed checksum value based on the file contents as indicated below. It is an error if the indicated name does not represent a valid file.
Removing a file from the database means first deleting the entry at the lowest file level in the structure, and then if the containing dictionary becomes empty it must be deleted also, and so forth up the line until a non-empty dictionary is encountered. It is an error if you attempt to remove the entry which is not in the database.
Checking the integrity of a file means computing the checksum value of the specified file and comparing it against the value stored in the database and reporting the result. It is an error if the file doesn't exist on the system or in the database.
You would add the following options to your program from task 1.
1) add the directory of files to the database. The user supplies the name of a directory. You must add a checksum entry for every file in the directory (not the directory itself), as well as recursively descend into any subdirectories, adding entries for files in them (but not themselves).
2) Delete the directory of files from the database. The user supplies the name of a directory. You must delete entries for all files contained in that directory, and any of its subdirectories.
3) Check the integrity of files in a directory. The user supplies the name of a directory. Each file contained in that directory, and recursively through its subdirectories, must have its checksum checked against the corresponding entry in the database, if it exists. All of the files that have been changed based on different checksums must be listed in sorted order. Any new files which are not currently in the database must be given in a separate sorted list.
Add the ability to store a file's permissions along with the checksum value in the database. Every time an entry is made in the database, the permissions must also be stored. Add a command line option, -p, that if specified means that an integrity check is not just comparing the checksum values, but also comparing to see if the permission bits have changed.
This version of the program must be able to handle relative file names based on the present working directory, not just absolute paths as was allowed in task 1.