bash script question
 

I have written a script to compare a file containing the md5sums of all files in a directory. I would like to compare this file with a master file of the same type to monitor that these files are not changed.
There will be many authorised changes made via scripting and a new master file will be created after each authorised change. Using tripwire it just goes batty - hence the need for a script (before anyone asks :-)

Anyway - it's bailing at the if statement, what it's supposed to do is check whether if a is = to b then quit else run ...

Here's the script - thanks for any help.

#!/bin/bash
# create md5 list and compare to master list
# list files that have been changed (if any) and mail admins
#
##########################
# Set variables
#########################1#
master="/tmp/master"
compare="/tmp/compare"
changed="/tmp/changed"
notify="/tmp/notify"
EMAILLIST="user@domain"
#############################
#Path to programs
#############################
diff="/usr/bin/diff"
mail="/bin/mail"
cat="/bin/cat"
############################################################
#create compare file
find /home/test/list/ -type f -exec md5sum \{\} \; >/tmp/compare
#compare the two md5 files
if [ "a${master}" != "a${compare}" ]; then
exit 1
else #diff the files and create changed file
diff $master $compare > /tmp/changed
#
echo "^MFiles that have been changed:" >$notify
echo "^M" >>$notify
cat $changed |awk ' { print $3 }' >> $notify
mail -s "Unauthorized Website Change" ${EMAILLIST} < $notify
#clean up files
#rm $compare $changed $notify
fi

fixed it - here is the working script for anyone who is curious
(btw - the ^M is a line break created by ctrl-v ctrl-M)

#!/bin/bash
# create md5 list and compare to master list
# list files that have been changed (if any) and mail admins
#
#########################
# Set variables
#########################
master="/tmp/master"
compare="/tmp/compare"
changed="/tmp/changed"
notify="/tmp/notify"
EMAILLIST="user@domain.com"
#########################
#create compare file
#
find /home/user/test/ -type f -exec md5sum \{\} \; >/tmp/compare
#compare the two md5 files
if [ "a${master}" = "a${compare}" ]; then
echo "Files Are the same."
exit 0
fi
#diff the files and create changed file
diff $master $compare > $changed
#
echo "^MFiles that have been changed:" >$notify
echo "^M" >>$notify
cat $changed |awk ' { print $3 }' >> $notify #strips md5sum and lists only the files
mail -s "Unauthorized Change" ${EMAILLIST} < $notify
#clean up files
rm $compare $changed $notify

Re: bash script question
 

hmmm... never mind. you fixed it while i was responding....

I don't believe you can compare files that way. You should
probably diff them then check the return value of diff to
see if they are different and mail yourself the results if
they are.

diff $master $compare > /tmp/changed
if [ ! $? -eq 0 ]; then
#mail yourself the diffs
fi

Also you probably want to change the /tmp/changed
file to a randomly generated name otherwise you'll
be very vulnerable to a link attack. Initialize it with
something like

compare=changed`dd if=/dev/random bs=1 count=10 2>/dev/null | md5sum | cut -f1 -d" '`

That'll give you a nice unpredictable name, that's just off
the top of my head there's probably a
simpler way to do it but you probably get the idea.

good points LogicG8

thanks.

//moderator.note: moved to Linux - Programming, not a security issue.