Commit df0a637d authored by Kevin Morris's avatar Kevin Morris
Browse files

add aurweb.captcha, a CAPTCHA utility module

This CAPTCHA workflow is the same workflow used by our current
PHP implementation of account registration.

Signed-off-by: Kevin Morris's avatarKevin Morris <>
parent 7a6a3859
""" This module consists of aurweb's CAPTCHA utility functions and filters. """
import hashlib
import jinja2
from aurweb.db import query
from aurweb.models.user import User
def get_captcha_salts():
""" Produce salts based on the current user count. """
count = query(User).count()
salts = []
for i in range(0, 6):
salts.append(f"aurweb-{count - i}")
return salts
def get_captcha_token(salt):
""" Produce a token for the CAPTCHA salt. """
return hashlib.md5(salt.encode()).hexdigest()[:3]
def get_captcha_challenge(salt):
""" Get a CAPTCHA challenge string (shell command) for a salt. """
token = get_captcha_token(salt)
return f"LC_ALL=C pacman -V|sed -r 's#[0-9]+#{token}#g'|md5sum|cut -c1-6"
def get_captcha_answer(token):
""" Compute the answer via md5 of the real template text, return the
first six digits of the hexadecimal hash. """
text = r"""
.--. Pacman v%s.%s.%s - libalpm v%s.%s.%s
/ _.-' .-. .-. .-. Copyright (C) %s-%s Pacman Development Team
\ '-. '-' '-' '-' Copyright (C) %s-%s Judd Vinet
This program may be freely redistributed under
the terms of the GNU General Public License.
""" % tuple([token] * 10)
return hashlib.md5((text + "\n").encode()).hexdigest()[:6]
def captcha_salt_filter(context):
""" Returns the most recent CAPTCHA salt in the list of salts. """
salts = get_captcha_salts()
return salts[0]
def captcha_cmdline_filter(context, salt):
""" Returns a CAPTCHA challenge for a given salt. """
return get_captcha_challenge(salt)
......@@ -12,7 +12,7 @@ from fastapi.responses import HTMLResponse
import aurweb.config
from aurweb import l10n, time
from aurweb import captcha, l10n, time
# Prepare jinja2 objects.
loader = jinja2.FileSystemLoader(os.path.join(
......@@ -23,6 +23,10 @@ env = jinja2.Environment(loader=loader, autoescape=True,
# Add tr translation filter.
env.filters["tr"] =
# Add captcha filters.
env.filters["captcha_salt"] = captcha.captcha_salt_filter
env.filters["captcha_cmdline"] = captcha.captcha_cmdline_filter
def make_context(request: Request, title: str, next: str = None):
""" Create a context for a jinja2 TemplateResponse. """
import hashlib
from aurweb import captcha
def test_captcha_salts():
""" Make sure we can get some captcha salts. """
salts = captcha.get_captcha_salts()
assert len(salts) == 6
def test_captcha_token():
""" Make sure getting a captcha salt's token matches up against
the first three digits of the md5 hash of the salt. """
salts = captcha.get_captcha_salts()
salt = salts[0]
token1 = captcha.get_captcha_token(salt)
token2 = hashlib.md5(salt.encode()).hexdigest()[:3]
assert token1 == token2
def test_captcha_challenge_answer():
""" Make sure that executing the captcha challenge via shell
produces the correct result by comparing it against a straight
up token conversion. """
salts = captcha.get_captcha_salts()
salt = salts[0]
challenge = captcha.get_captcha_challenge(salt)
token = captcha.get_captcha_token(salt)
challenge2 = f"LC_ALL=C pacman -V|sed -r 's#[0-9]+#{token}#g'|md5sum|cut -c1-6"
assert challenge == challenge2
def test_captcha_salt_filter():
""" Make sure captcha_salt_filter returns the first salt from
Example usage:
<input type="hidden" name="captcha_salt" value="{{ captcha_salt }}">
salt = captcha.captcha_salt_filter(None)
assert salt == captcha.get_captcha_salts()[0]
def test_captcha_cmdline_filter():
""" Make sure that the captcha_cmdline filter gives us the
same challenge that get_captcha_challenge does.
Example usage:
<code>{{ captcha_salt | captcha_cmdline }}</code>
salt = captcha.captcha_salt_filter(None)
display1 = captcha.captcha_cmdline_filter(None, salt)
display2 = captcha.get_captcha_challenge(salt)
assert display1 == display2
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