HOW TO : Use awk to print values larger than certain number

Quick how to on using awk to filter results if a certain value (column) is larger than a set value.

For example, if you have a file (servers.txt) with lines in this format

a_datacenter, servers 20
error, servers xyz
b_datacenter, servers 21
c_datacenter, servers 50

and you want to show only the lines that have server value larger than 20, you can do this in awk by running

grep datacenter servers.txt | awk '$3 > 20  {print ;}' | more 

breaking down the commands

grep – parsing down the output to just show the lines containing datacenter

awk – $3 > 20 : Get the third variable (awk seperates text using spaces by default) and check if it is greater than 20

print – print the entire line

HOW TO : Parse IP Address in Windows Batch File

We had a recent challenge at work which required us to execute different actions based on which office a particular workstation was located in. Since we have unique network ranges per office, I thought this would be a good variable to use. Just for future reference, here is how we accomplished this in a batch file. The workstations were running Windows 7


@ECHO OFF

FOR /f "tokens=3" %%I IN (
'netsh interface ip show address "Local Area Connection" ^| findstr "IP Address"'
) DO SET ipAddress=%%I

REM "Office 1"
IF NOT x%ipAddress:10.130=%==x%ipAddress% (
ECHO "Office 1" + %ipAddress%
ECHO "do_something_else" )

REM "Office 2"
IF NOT x%ipAddress:10.140=%==x%ipAddress% (
ECHO "Office 2" + %ipAddress%
ECHO "do_something_else" )

Details of function used

  • netsh interface ip show address “Local Area Connection” : With this command we are extracting the IP information of just the LAN port
  • findstr “IP Address” : returns the line containing “IP Address”
  • IF NOT x%ipAddress:10.130=%==x%ipAddress% : We are using the substitution function and returning false if the new string doesnt match the original
  • FOR /f “tokens=3” : Using the functions in the FOR loop to extract the third variable in the matching line

Update 1 : Application Development : domainScan

Following up from my post earlier this month regarding building a security application that scans publicly available data (Google) and report on potential information leakage from a hostname.

I created a repo on github if anyone is interested in contributing. First thing any good developer does is to check code in early and often :). The repo is at https://github.com/kudithipudi/security-domainscan

Here’s the sudo code I put together as a framework to build on


functions
 read_file(file)
 open file;
 for each line
 process_line(hostname)

 process_line(hostname)
 search_google(hostname)
 write to log

 search_google (hostname)
 connect to google api
 get results for hostname
 return number of results

main
 read_file(input)

 

HOW TO : Search for a record in MongoDB based on length

Quick entry for my own records.

MongoDB is one of the popular open source document database that is part of the nosql movement. One of the applications we deployed at work uses MongoDB as an internal storage engine. We ran into an issue where MongoDB was trying to replicate data to MySQL and the replication stopped because of a size mismatch for an object between MongoDB and MySQL. Essentially MongoDB was trying to insert a record into MySQL that was larger than the defined length.

Here is the query we used to find the culprit objects. We used the awesome Robomongo client to connect to the MongoDB instance.

db.some_table_to_search.find({$where:"this.some_column_to_search.length > 40"})

Breaking down the command

db -> Specifies the database you are trying to search

some_table_to_search -> Specifie the table you are trying to search

some_column_to_search -> Specified the particular column you are trying to search.

In this specific example, we were looking for entries longer than 40 characters for this column.

If you come from the traditional RDBMS world, here is a link from MongoDB comparing terminology between RDBMS and MongoDB.

http://docs.mongodb.org/manual/reference/sql-comparison/

Idea for a security application

I think the best way to learn a new (programming) language is to address a real world problem :). So here is one, I want to solve in the next few months.

One of the things I like to do as part of a evaluation security process is to check the amount of public information available for a website. I frequently find that people find information leakage from websites they thought were secure or not publicly accessible.

The idea is to create a python script to do the following

  • Must have
    • Inject list of hostnames and do the following
      • Check whether they resolve to a public IP or not
      • If resolving to public IP, check the amount of data being exposed by this site by doing a quick google search
      • Report on the amount of information available sorted by amount
  • Nice to have
    • take domain name instead of hostnames and try to do a domain transfer and capture all hostnames in the domain
    • leverage Google API instead of web scraping
    • web interface to allow input and show output

Why python? Well, I have been trying to learn it for sometime now and I think it is time to put all that learning to use :).

Anyone interested in joining the fun?

Lessons of the trade : Handling CVV numbers

Just for my notes.. Even though the CVV numbers on a credit card, look like numbers :), don’t treat them as integers in your code. Some of the numbers start with a 0.. so 059 might become 59 by the time you try to process it if you capture the CVV field as an integer.

Just treat them like a string.

And obviously you are not storing them anywhere in your application/network :). Or you might end up in the headlines like some of our retailers.

Overheard : Comment about what is takes to be a competent person

Came across quote by Robert A. Heinlein on a blog post by Jacques Mattheij regarding a what a competent man should be able to do

A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.

Parenthood means..

  • Not hesitating for a moment to put your nose near someone’ arse to check if they pooped
  • Thinking it is cute when someone pees in your bed
  • Taking food that someone else spits out and finishing it off without hesitating for a second

Some of the joys I got to experience in the last two years raising our Son :).

And yes.. a whole lot of new found respect for my parents.