Parsing Log Files

10 Points

regular-expressions

Instructions

This exercise addresses the parsing of log files.

After a recent security review you have been asked to clean up the organization's archived log files.

All strings passed to the methods are guaranteed to be non-null and without leading and trailing spaces.

1. Identify garbled log lines

You need some idea of how many log lines in your archive do not comply with current standards. You believe that a simple test reveals whether a log line is valid. To be considered valid a line should begin with one of the following strings:

[TRC]
[DBG]
[INF]
[WRN]
[ERR]
[FTL]

Implement the LogParser.IsValidLine() method to return false if a string is not valid otherwise true.

var lp = new LogParser();
lp.IsValidLine("[ERR] A good error here");
// => true
lp.IsValidLine("Any old [ERR] text");
// => false
lp.IsValidLine("[BOB] Any old text");
// => false

2. Split the log line

A new team has joined the organization, and you find their log files are using a strange separator for "fields". Instead of something sensible like a colon ":" they use a string such as "<--->" or "<=>" (because it's prettier) in fact any string that has a first character of "<" and a last character of ">" and any combination of the following characters "^", "*", "=" and "-" in between.

Implement the LogParser.SplitLogLine() method that takes a line and returns an array of strings each of which contains a field.

var lp = new LogParser();
lp.SplitLogLine("Section 1<===>Section 2<^-^>Section 3");
// => {"Section 1", "Section 2", "Section 3"}

3. Count the number of lines containing a quoted password

The team needs to know about passwords occurring in quoted text so that they can be examined manually.

Implement the LogParser.CountQuotedPasswords() method to provide an indication of the likely scale of the manual exercise.

Identify log lines where the literal string "password", which may be in any combination of upper or lower case, is surrounded by quotation marks. You should account for the possibility of additional content between the quotation marks before and after "password".

Lines passed to the routine may or may not be valid as defined in task 1. We process them in the same way, whether or not they are valid.

string lines =
    "[INF] passWord " + Environment.NewLine + // contains 'password' but not surrounded by quotation marks
    "\"passWord\"" + Environment.NewLine + // count this one
    "[INF] User saw error message \"Unexpected Error\" on page load." + Environment.NewLine + //does not contain 'password'
    "[INF] \"The secret password was added by the user\""; // count this one

var lp = new LogParser();
lp.CountQuotedPasswords(lines);
// => 2

4. Remove artifacts from log

You have found that some upstream processing of the logs has been scattering the text "end-of-line" followed by a line number (without an intervening space) throughout the logs.

Implement the LogParser.RemoveEndOfLineText() method to take a string and remove the end-of-line text and return a "clean" string.

Lines not containing end-of-line text should be returned unmodified.

Just remove the end of line string. Do not attempt to adjust the whitespaces.

var lp = new LogParser();
lp.RemoveEndOfLineText("[INF] end-of-line23033 Network Failure end-of-line27");
// => "[INF]  Network Failure "

5. List lines with extremely weak passwords so the guilty can be punished

Before expunging the passwords from the file we need to list any instances where passwords begin with the text "password".

Implement the LogParser.ListLinesWithPasswords() method to print out the offending password followed by the complete line.

Lines with quoted passwords have already been removed and you process lines irrespective of whether they are valid (as per task 1).

Lines containing an offending password should be returned prefixed with "<password>: ".

Lines not containing an offending password should be returned prefixed with "--------: ".

var lp = new LogParser();
lp.ListLinesWithPasswords(new string[] {"my passwordsecret is great"});
// => "passwordsecret: my passwordsecret is great"
lp.ListLinesWithPasswords(new string[] {"my password secret"});
// => {"--------: my password secret"}

csharp