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xmpp.chapril.org-ejabberd/tools/captcha-ng.sh

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Executable File

#!/bin/bash
# Copyright © 2021 Adrien Bourmault (neox@os-k.eu)
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# 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=$1
TRANSFORMATIONS=(INTRUDER SUM)
DIGIT=(zero one two three four five six seven eight nine ten)
if test -n "${BASH_VERSION:-''}" ; then
get_random ()
{
R=$RANDOM
}
else
for n in $(od -A n -t u2 -N 64 /dev/urandom); do RL="$RL$n "; done
get_random ()
{
R=${RL%% *}
RL=${RL#* }
}
fi
INTRUDER()
{
NUMBERS=$(echo "$INPUT" | grep -o . | tr '\n' ' ')
SORTED_UNIQ_NUM=$(echo "${NUMBERS[@]}" | sort -u | tr '\n' ' ')
RANDOM_DIGITS=$(echo 123456789 | grep -o . | sort -R | tr '\n' ' ')
INTRUDER=-1
for i in $RANDOM_DIGITS
do
if [[ ! " ${SORTED_UNIQ_NUM[@]} " =~ ${i} ]]; then
INTRUDER=$i
break
fi
done
# Worst case
if [[ $INTRUDER -eq "-1" ]]
then
printf "Type %s \n without changes" "$INPUT"
return
fi
for num in ${NUMBERS}
do
get_random
R=$((R % 100))
if [[ $R -lt 60 ]]; then
NEWINPUT=${NEWINPUT}${num}${INTRUDER}
else
NEWINPUT=${NEWINPUT}${num}
fi
done
get_random
R=$((R % 100))
if [[ $R -lt 50 ]]; then
printf "Type %s by\n deleting the %s" "$NEWINPUT" "${DIGIT[$INTRUDER]}"
else
printf "Enter %s by\n removing the %s" "$NEWINPUT" "${DIGIT[$INTRUDER]}"
fi
}
SUM()
{
get_random
RA=$((R % 100))
if [[ $((INPUT % 2)) -eq 0 ]]; then
A=$((INPUT - RA))
B=$RA
else
B=$((INPUT - RA))
A=$RA
fi
get_random
R=$((R % 100))
if [[ $R -lt 25 ]]; then
printf "Type the result\n of %s + %s" "$A" "$B"
elif [[ $R -lt 50 ]]; then
printf "SUMx\n %s and %s" "$A" "$B"
elif [[ $R -lt 75 ]]; then
printf "Add\n %s and %s" "$A" "$B"
else
printf "Enter the result\n of %s + %s" "$A" "$B"
fi
}
get_random
RAND_ITALIC=$((R % 25))
get_random
RAND_ANGLE=$((R % 3))
get_random
RAND_INDEX=$((R % ${#TRANSFORMATIONS[@]}))
convert -size 300x60 xc:none -pointsize 20 \
\( -clone 0 -fill black \
-stroke black -strokewidth 1 \
-annotate "${RAND_ANGLE}x${RAND_ITALIC}+0+0" "\n $(${TRANSFORMATIONS[$RAND_INDEX]})" \
-roll +"$ROLL_X"+0 \
-wave "$WAVE1_AMPLITUDE"x"$WAVE1_LENGTH" \
-roll -"$ROLL_X"+0 \) \
-flatten -crop 300x60 +repage -quality 500 -depth 11 png:-