The R Language is really good at data and statistical analysis, but when it comes to working with information security data it has a few holes that need plugging up. Bob has been doing a couple of posts using Rcpp to do things like Basic DNS Lookups, TXT lookups, and IPv4 Conversions. I wanted to add to some of that work with a quick package for parsing domain names.
While *.com, *.net and *.org top-level domains are easy to parse, the rest of the world gets messy rather quick. Just taking the entry after the last dot creates problems for top-level domains like anything in *.com.uk. Or to make things even more complicated, the name of “us-west-1.compute.amazonaws.com” is considered (for name parsing) to be a top-level domain and the domain name we’d want to process is the name that would appear before the us-west-1 in that name.
Introducing TLD Extract (the R version)
It’s always easier to imitate rather than reinvent, so I took some time to read through the tldextract Python package, and used that to test my code was executing properly during development so I used the same name for the R pacakge. The data for the package is drawn from the same source as the python package, the Public Suffix List from the Mozilla Foundation. For convenience, I include a cached version of the data so it can run offline.
To install this package, use the devtools package:
Using the package is fairly straight forward, it will return a data frame with the original name and seperate columns for each parsed component.
library(tldextract) # use the cached lookup data, simple call tldextract("www.google.com") ## host subdomain domain tld ## 1 www.google.com www google com # it can take multiple domains at the same time tldextract(c("www.google.com", "www.google.com.ar", "googlemaps.ca", "tbn0.google.cn")) ## host subdomain domain tld ## 1 www.google.com www google com ## 2 www.google.com.ar www google com.ar ## 3 googlemaps.ca <NA> googlemaps ca ## 4 tbn0.google.cn tbn0 google cn
The specification for the top-level domains is cached in the package and is viewable.
# view and update the TLD domains list in the tldnames data data(tldnames) head(tldnames) ##  "ac" "com.ac" "edu.ac" "gov.ac" "net.ac" "mil.ac"
If the cached version is out of data and the package isn’t updated, the data can be manually loaded, and then passed into the function.
# get most recent TLD listings tld <- getTLD() # optionally pass in a different URL than the default manyhosts <- c("pages.parts.marionautomotive.com", "www.embroiderypassion.com", "fsbusiness.co.uk", "www.vmm.adv.br", "ttfc.cn", "carole.co.il", "visiontravail.qc.ca", "mail.space-hoppers.co.uk", "chilton.k12.pa.us") tldextract(manyhosts, tldnames=tld) ## host subdomain domain tld ## 1 pages.parts.marionautomotive.com pages.parts marionautomotive com ## 2 www.embroiderypassion.com www embroiderypassion com ## 3 fsbusiness.co.uk <NA> fsbusiness co.uk ## 4 www.vmm.adv.br www vmm adv.br ## 5 ttfc.cn <NA> ttfc cn ## 6 carole.co.il <NA> carole co.il ## 7 visiontravail.qc.ca <NA> visiontravail qc.ca ## 8 mail.space-hoppers.co.uk mail space-hoppers co.uk ## 9 chilton.k12.pa.us <NA> chilton k12.pa.us
And there we have it!
One last thing, this is the first package I created with unit tests. This package is really simple and adding in unit tests seamed like a no-brainer. After reading through Hadley Wickham’s Advanced R online book and exploring how other packages implement the testthat package, I implemented a few simple tests. If you are creating (or about to create) R packages, look at the source for the tldextract package for the incredibly simple unit tests included with it!