web/captcha.py
author Sylvain Thénault <sylvain.thenault@logilab.fr>
Tue, 13 Apr 2010 12:19:24 +0200
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child 5423 e15abfdcce38
permissions -rw-r--r--
#773448: refactor session and 'no connection' handling, by introducing proper web session. We should now be able to see page even when no anon is configured, and be redirected to the login form as soon as one tries to do a query.
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"""Simple captcha library, based on PIL. Monkey patch functions in this module
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if you want something better...
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:organization: Logilab
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:copyright: 2009-2010 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.
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:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
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:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses
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"""
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__docformat__ = "restructuredtext en"
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from random import randint, choice
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from cStringIO import StringIO
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import Image, ImageFont, ImageDraw, ImageFilter
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from time import time
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from cubicweb import tags
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from cubicweb.web import ProcessFormError, formwidgets as fw
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def pil_captcha(text, fontfile, fontsize):
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    """Generate a captcha image. Return a PIL image object.
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    adapted from http://code.activestate.com/recipes/440588/
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    """
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    # randomly select the foreground color
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    fgcolor = randint(0, 0xffff00)
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    # make the background color the opposite of fgcolor
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    bgcolor = fgcolor ^ 0xffffff
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    # create a font object
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    font = ImageFont.truetype(fontfile, fontsize)
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    # determine dimensions of the text
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    dim = font.getsize(text)
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    # create a new image slightly larger that the text
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    img = Image.new('RGB', (dim[0]+5, dim[1]+5), bgcolor)
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    draw = ImageDraw.Draw(img)
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    # draw 100 random colored boxes on the background
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    x, y = img.size
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    for num in xrange(100):
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        draw.rectangle((randint(0, x), randint(0, y),
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                        randint(0, x), randint(0, y)),
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                       fill=randint(0, 0xffffff))
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    # add the text to the image
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    draw.text((3, 3), text, font=font, fill=fgcolor)
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    img = img.filter(ImageFilter.EDGE_ENHANCE_MORE)
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    return img
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def captcha(fontfile, fontsize, size=5, format='JPEG'):
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    """Generate an arbitrary text, return it together with a buffer containing
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    the captcha image for the text
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    """
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    text = u''.join(choice('QWERTYUOPASDFGHJKLZXCVBNM') for i in range(size))
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    img = pil_captcha(text, fontfile, fontsize)
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    out = StringIO()
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    img.save(out, format)
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    out.seek(0)
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    return text, out
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class CaptchaWidget(fw.TextInput):
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    def render(self, form, field, renderer=None):
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        # t=int(time()*100) to make sure img is not cached
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        src = form._cw.build_url('view', vid='captcha', t=int(time()*100),
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                                 captchakey=field.input_name(form))
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        img = tags.img(src=src, alt=u'captcha')
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        img = u'<div class="captcha">%s</div>' % img
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        return img + super(CaptchaWidget, self).render(form, field, renderer)
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    def process_field_data(self, form, field):
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        captcha = form._cw.session.data.pop(field.input_name(form), None)
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        val = super(CaptchaWidget, self).process_field_data(form, field)
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        if val is None:
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            return val # required will be checked by field
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        if captcha is None:
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            msg = form._cw._('unable to check captcha, please try again')
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            raise ProcessFormError(msg)
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        elif val.lower() != captcha.lower():
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            msg = form._cw._('incorrect captcha value')
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            raise ProcessFormError(msg)
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        return val