How to pause to avoid capturing passwords? #216

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1. kernc commented on May 14, 2020

   

   kernc

   on May 14, 2020

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   What happens if you killall -STOP logkeys and killall -CONT logkeys afterwards? Does it get the events it missed?
2. MatthieuStigler commented on May 14, 2020

   

   MatthieuStigler

   on May 14, 2020

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   Thanks for your quick answer!

   This is a good idea, although the issue is that I start logkeys with sudo, so to killall I also need sudo, so the sudo password will be stored in the logfile (making it extremely easy to detect for someone who could have access to the log file).

   I realize the same problem would happen if logkey had a --pause option but was started in sudo, so I guess the question is actually: what is the recommended way to use logkey in a secure way?

   Thanks a lot!
3. kernc commented on May 15, 2020

   

   kernc

   on May 15, 2020

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   Does the above sudo killall ... method work without logging your password characters, or do they backfill when the process is resumed?
4. MatthieuStigler commented on May 17, 2020

   

   MatthieuStigler

   on May 17, 2020

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   doing the first sudo killall -STOP already enters the password into the log, so it seems dangeous to use that approach?

   Thanks!
5. mFIND commented on May 19, 2020

   

   mFIND

   on May 19, 2020

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   My take at this issue would be to create new script, /usr/local/etc/logkeys-pause.sh doing $(kilall -STOP logkeys), and a new program, let's say "llkp" with the same permissions as "llkk".
   Would this approach be acceptable?
6. kernc commented on May 19, 2020

   

   kernc

   on May 19, 2020

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   The problem with shell scripts is that they can't setuid, so sudo password would still be required.
7. MatthieuStigler commented on May 19, 2020

   

   MatthieuStigler

   on May 19, 2020

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   it seems hence that using the method with sudo is difficult? Another approach would maybe try to not use sudo but yet to write to an encrypted file? do you have any recommendation or suggestions about this approach instead?

   thanks a lot!
8. kernc commented on May 20, 2020

   

   kernc

   on May 20, 2020

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   to write to an encrypted file?

   Something like:

   $ sudo logkeys ... -o - | mcrypt --force --flush > logkeys.log
   
   $ cat logkeys.log | mcrypt --decrypt
9. mFIND commented on May 20, 2020

   

   mFIND

   on May 20, 2020

   Last edited by kernc

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   I know that scripts can't use setuid, that's why I suggested writing new setuid'ed program in C:
   That way, the script won't need setuid, since llkp would have UID=0.

   #include <cstdlib>
   #include <unistd.h>
   
   int main() {
     setuid(0);
     exit(system(SYS_CONF_DIR "/logkeys-pause.sh"));  // SYS_CONF_DIR defined in CXXFLAGS in Makefile.am
   }

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