xmpp/captcha/experimental.sh

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#!/bin/bash
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# Copyright © 2021 Adrien Bourmault (neox@a-lec.org)
# Copyright © 2021 Echolib (echolib@dismail.de)
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
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# This script is an example captcha script.
# It takes the text to recognize in the captcha image as a parameter.
# It return the image binary as a result. ejabberd support PNG, JPEG and GIF.
# The whole idea of the captcha script is to let server admins adapt it to
# their own needs. The goal is to be able to make the captcha generation as
# unique as possible, to make the captcha challenge difficult to bypass by
# a bot.
# Server admins are thus supposed to write and use their own captcha generators.
# This script relies on ImageMagick.
# It is NOT compliant with ImageMagick forks like GraphicsMagick.
INPUT=$1
LENINPUT=${#INPUT}
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DIGITS=(zéros uns deux trois quatres cinqs six septs huits neufs dix)
DIGIT=(zéro un deux trois quatre cinq six sept huit neuf dix)
# ****************************************************************************
#
# Tools
#
# ****************************************************************************
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# Loops 10 times (should be enough) to check if a TARGET number is in INPUT
GENERATE__NOTIN() {
for i in {1..10}
do
FALSENBR=`seq 1 9 | sort -R | head -n 1`
! [[ $INPUT =~ $FALSENBR ]] \
&& break
done
}
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# ****************************************************************************
#
# Captcha shapes
#
# ****************************************************************************
# REPLACEs a random number in INPUT by another one randomized
REPLACE() {
NAME="REPLACE"
PLACE=`seq 1 6 | sort -R | head -n 1`
TARGET=`echo "$INPUT" | head -c $PLACE | tail -c 1`
GENERATE__NOTIN
NAME+="-$FALSENBR-$TARGET"
NEWINPUT=${INPUT//$TARGET/$FALSENBR}
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INSTRUCTIONS1="Remplacez les ${DIGITS[FALSENBR]} par des ${DIGITS[TARGET]}"
}
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# REVERSEs INPUT. Ask to Add first or last number in random.
REVERSE() {
NAME="REVERSE"
RFL=`seq 1 2 | sort -R | head -n 1` # Rand First (1) or Last (2)
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ADDNBR=${DIGITS[ADDNBR]}
for ((i=$LENINPUT-1;i>=0;i--))
do
NEWINPUT="$NEWINPUT${INPUT:$i:1}"
done
if (( $RFL == 1 ));then
ADDNBR="${INPUT:0:1}"
NAME+="_FIRST"
NEWINPUT=${NEWINPUT:0:$LENINPUT-1} # Do not show first INPUT NBR
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INSTRUCTIONS1="Écrivez le chiffre ${DIGIT[$ADDNBR]} puis"
INSTRUCTIONS2="Recopiez de DROITE à GAUCHE ←"
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else
ADDNBR="${INPUT:$LENINPUT-1:1}"
NAME+="_LAST"
NEWINPUT=${NEWINPUT:1:$LENINPUT-1} # Do not show last INPUT NBR
INSTRUCTIONS1="Recopiez de DROITE à GAUCHE ←"
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INSTRUCTIONS2="Terminez par le chiffre ${DIGIT[$ADDNBR]}"
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fi
NAME+="-$ADDNBR"
}
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# Add FALSE NBR to INPUT at three randomized place
NOTIN() {
NAME="NOTIN"
GENERATE__NOTIN
PLACE=(`seq 0 $((LENINPUT-1)) | sort -R | head -n 3 | sort -n`)
for i in `seq 0 $((LENINPUT-1))`
do
(( $i == ${PLACE[0]} )) \
&& NEWINPUT+="$FALSENBR"
(( $i == ${PLACE[1]} )) \
&& NEWINPUT+="$FALSENBR"
(( $i == ${PLACE[2]} )) \
&& NEWINPUT+="$FALSENBR"
NEWINPUT="$NEWINPUT${INPUT:$i:1}"
done
NAME+="-$FALSENBR"
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INSTRUCTIONS1="Recopiez sans les ${DIGITS[FALSENBR]}"
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}
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# Take a random NBR from INPUT. Calculate X
CALCUL() {
PLACE=`seq 1 $((LENINPUT)) | sort -R | head -n 1`
TARGET=`echo "$INPUT" | head -c $PLACE | tail -c 1`
NEWINPUT=${INPUT//$TARGET/X}
RC=`seq 1 2 | sort -R | head -n 1` # 1 = - | 2 = +
if (( $RC == 1 ));then
FALSENBR=`seq $TARGET 10 | sort -R | head -n 1`
RESUME=$(( FALSENBR - TARGET ))
INSTRUCTIONS1="Calculez: $FALSENBR moins $RESUME. Copiez..."
NAME="CALCULM-$FALSENBR-$RESUME"
else
FALSENBR=`seq 1 4 | sort -R | head -n 1`
if (( $FALSENBR <= $TARGET ));then
RESULT=$(( TARGET + FALSENBR ))
RESUME=$(( TARGET - FALSENBR ))
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INSTRUCTIONS1="Calculez: ${DIGIT[FALSENBR]} + ${DIGIT[RESUME]}. Copiez..."
NAME="CALCULP-$FALSENBR-$RESUME"
else
RESULT=$(( FALSENBR - TARGET ))
RESUME=$(( TARGET - RESULT ))
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INSTRUCTIONS1="Calculez: ${DIGIT[RESULT]} + ${DIGIT[RESUME]}. Copiez..."
NAME="CALCULP-$RESULT-$RESUME"
fi
fi
INSTRUCTIONS2="...en remplaçant chaque X par la somme"
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}
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# ****************************************************************************
#
# Random captcha shape choice (aka main)
#
# ****************************************************************************
MODULES=(CALCUL NOTIN REPLACE REVERSE)
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NMODULES=
RMODULE=`seq 0 $(( ${#MODULES[@]} - 1)) | sort -R | head -n 1`
eval "${MODULES[RMODULE]}"
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TEXT="$NEWINPUT"
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CHAPRILURI="/var/lib/ejabberd/chapril_captchas_experimental/${NAME}_${NEWINPUT}_${INPUT}.png"
convert -size 300x70 xc:none -pointsize 20 \
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\( -clone 0 -fill black \
-stroke black -strokewidth 1 \
-font Helvetica-Narrow -annotate "0x0+0+0" "\n $INSTRUCTIONS1" \
-font Helvetica-Bold -annotate "0x0+0+22" "\n $TEXT" \
-font Helvetica-Narrow -annotate "0x0+0+44" "\n $INSTRUCTIONS2" \
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-roll +$ROLL_X+0 \
-wave "$WAVE1_AMPLITUDE"x"$WAVE1_LENGTH" \
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-roll -$ROLL_X+0 \) \
-flatten -crop 300x70 +repage -quality 500 \
-depth 11 png:"$CHAPRILURI"
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convert -size 300x70 xc:none -pointsize 20 \
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\( -clone 0 -fill black \
-stroke black -strokewidth 1 \
-font Helvetica-Narrow -annotate "0x0+0+0" "\n $INSTRUCTIONS1" \
-font Helvetica-Bold -annotate "0x0+0+22" "\n $TEXT" \
-font Helvetica-Narrow -annotate "0x0+0+44" "\n $INSTRUCTIONS2" \
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-roll +$ROLL_X+0 \
-wave "$WAVE1_AMPLITUDE"x"$WAVE1_LENGTH" \
-roll -$ROLL_X+0 \) \
-flatten -crop 300x70 +repage -quality 500 -depth 11 png:-