libpsl - C library to handle the Public Suffix List

A "public suffix" is a domain name under which Internet users can directly register own names.

Browsers and other web clients can use it to

• avoid privacy-leaking "supercookies"
• avoid privacy-leaking "super domain" certificates (see post from Jeffry Walton)
• domain highlighting parts of the domain in a user interface
• sorting domain lists by site

Libpsl...

• has built-in PSL data for fast access (DAWG/DAFSA reduces size from 180kB to ~32kB)
• allows to load PSL data from files
• checks if a given domain is a "public suffix"
• provides immediate cookie domain verification
• finds the longest public part of a given domain
• finds the shortest private part of a given domain
• works with international domains (UTF-8 and IDNA2008 Punycode)
• is thread-safe
• handles IDNA2008 UTS#46 (libicu is used by psl2c if installed)

Find more information about the Publix Suffix List here.

Download the Public Suffix List here.

The DAFSA code has been taken from Chromium Project.

API Documentation

You find the current API documentation here.

Quick API example

#include <stdio.h>
#include <libpsl.h>

int main(int argc, char **argv)
{
	const char *domain = "www.example.com";
	const char *cookie_domain = ".com";
	const psl_ctx_t *psl = psl_builtin();
	int is_public, is_acceptable;

	is_public = psl_is_public_suffix(psl, domain);
	printf("%s %s a public suffix.\n", domain, is_public ? "is" : "is not");

	is_acceptable = psl_is_cookie_domain_acceptable(psl, domain, cookie_domain);
	printf("cookie domain '%s' %s acceptable for domain '%s'.\n",
		cookie_domain, is_acceptable ? "is" : "is not", domain);

	return 0;
}

Command Line Tool

Libpsl comes with a tool 'psl' that gives you access to most of the library API via command line.

$ psl --help

prints the usage.

Convert PSL into DAFSA

The DAFSA format is a compressed representation of strings. Here we use it to reduce the whole PSL to about 32k in size.

Generate psl.dafsa from list/public_suffix_list.dat

$ src/make_dafsa.py --output-format=binary --input-format=psl list/public_suffix_list.dat psl.dafsa

Test the result (example)

$ tools/psl --load-psl-file psl.dafsa aeroclub.aero

License

Libpsl is made available under the terms of the MIT license.
See the LICENSE file that accompanies this distribution for the full text of the license.

src/make_dafsa.py and src/lookup_string_in_fixed_set.c are licensed under the term written in src/LICENSE.chromium.

Building from git

You should have python2.7+ installed.

Download project and prepare sources with

	git clone https://github.com/rockdaboot/libpsl
	./autogen.sh
	./configure
	make
	make check

Mailing List

Mailing List Archive

Mailing List

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libpsl-bugs+subscribe@googlegroups.com

and follow the instructions provided by the answer mail.

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