xmpp/captcha/captcha.sh

#!/bin/bash

# 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=(INTRUS SOMME)
DIGIT=(zéros uns deux trois quatres cinqs six septs huits neufs dix)

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

INTRUS()
{
    LENGTH=${#INPUT}
    NUMBERS=$(echo $INPUT | grep -o . | tr '\n' ' ')
    SORTED_UNIQ_NUM=$(echo "${NUMBERS[@]}" | sort -u | tr '\n' ' ')
    INTRUS=-1
    
    for i in 1 2 3 4 5 6 7 8 9
    do
        if [[ ! " ${SORTED_UNIQ_NUM[@]} " =~ " ${i} " ]]; then
            INTRUS=$i
            break
        fi
    done
    
    # Worst case
    if [[ $INTRUS -eq "-1" ]]
    then
        echo Tapez "$INPUT |sans changement"
        return
    fi
    
    for num in ${NUMBERS[@]}
    do
        get_random
        R=$(($R % 100))
             
        if [[ $R -lt 60 ]]; then 
            NEWINPUT=${NEWINPUT}${num}${INTRUS}
        else
            NEWINPUT=${NEWINPUT}${num}
        fi
    done
    
    get_random
    R=$(($R % 100))
    
    if [[ $R -lt 50 ]]; then
        echo "Tapez | $NEWINPUT |en supprimant les ${DIGIT[$INTRUS]}"
    else
        echo "Saisissez | $NEWINPUT |en enlevant les ${DIGIT[$INTRUS]}"
    fi
}

SOMME()
{
    get_random
    RB=$(($R % 5))
    get_random
    RA=$(($R % 10 * (10 ** $RB)))
    
    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
        echo "Tapez le résultat de | $A + $B"
    elif [[ $R -lt 50 ]]; then
        echo "Sommez | $A et $B"
    elif [[ $R -lt 75 ]]; then
        echo "Additionnez | $A et $B"
    else
        echo "Saisissez le résultat de | $A + $B"
    fi
}

get_random
RAND_INDEX=$(($R % ${#TRANSFORMATIONS[@]}))

INSTRUCTIONS=$(echo "$(${TRANSFORMATIONS[$RAND_INDEX]})" | cut -d "|" -f 1)
INSTRUCTIONS2=$(echo "$(${TRANSFORMATIONS[$RAND_INDEX]})" | cut -d "|" -f 3)
TEXT=$(echo "$(${TRANSFORMATIONS[$RAND_INDEX]})" | cut -d "|" -f 2)

convert -size 300x60 xc:none -pointsize 20 \
	\( -clone 0 -fill black \
	-stroke black -strokewidth 1 \
	-font Helvetica-Narrow -weight Thin -annotate "0x0+0+0" "\n $INSTRUCTIONS" \
	-font Helvetica-Bold -weight Light -annotate "0x0+0+18" "\n  $TEXT" \
	-font Helvetica-Narrow -weight Thin -annotate "0x0+0+35" "\n $INSTRUCTIONS2" \
	-roll +$ROLL_X+0 \
	-wave "$WAVE1_AMPLITUDE"x"$WAVE1_LENGTH" \
	-roll -$ROLL_X+0 \) \
	-flatten -crop 300x60 +repage -quality 500 -depth 11 png:"/var/lib/ejabberd/chapril_captchas/$(date "+%Y-%m-%d-%H%M%S")_${INPUT}.png"

convert -size 300x60 xc:none -pointsize 20 \
	\( -clone 0 -fill black \
	-stroke black -strokewidth 1 \
	-font Helvetica-Narrow -weight Thin -annotate "0x0+0+0" "\n $INSTRUCTIONS" \
	-font Helvetica-Bold -annotate "0x0+0+18" "\n $TEXT" \
	-font Helvetica-Narrow -weight Thin -annotate "0x0+0+36" "\n $INSTRUCTIONS2" \
	-roll +$ROLL_X+0 \
	-wave "$WAVE1_AMPLITUDE"x"$WAVE1_LENGTH" \
	-roll -$ROLL_X+0 \) \
	-flatten -crop 300x60 +repage -quality 500 -depth 11 png:-