Topic: Alternative /etc/init.d/S50telnetd

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Post #1

Wallace78

2 Jan 2006, 04:54

I'm using this script to avoid telnetd running when it isn't needed at all, ie: a) no failsafe mode, b) root passwd is set.

#!/bin/sh
FSAFE=0
PWDSET=0
# test failsafe mode
test -n "$FAILSAFE" && FSAFE=1
# check if root passwd is set
if [ -f /etc/passwd ]; then
  RPWD=$(cat /etc/passwd | grep root | cut -d":" -f2)
  if [ ".$RPWD" != ".*" ]; then
    PWDSET=1
  fi
fi
if [ ".$FSAFE" = ".1" ] || [ ".$PWDSET" = ".0" ]; then
  telnetd -l /bin/login
fi

Any side-effect?

Regards

Wallace

Post #2

6 Jan 2006, 08:08

I would write it more like this, but it's more a style preference.

#!/bin/sh
PWDSET=0
# check if root passwd is set
if [ -f /etc/passwd ]; then
  RPWD=$(grep root /etc/passwd | cut -d":" -f2)
  if [ ".$RPWD" != ".*" ]; then
    PWDSET=1
  fi
fi
if [ -n "$FAILSAFE" ] || [ ".$PWDSET" = ".0" ]; then
  telnetd -l /bin/login
fi

This way should avoid an extra variable assignment for FSAFE, and process creation for grep

Post #3

Stereo

6 Jan 2006, 11:39

Wallace78 wrote:

# test failsafe mode
test -n "$FAILSAFE" && FSAFE=1

Why don't you use $FAILSAFE directly?

Wallace78 wrote:

# check if root passwd is set
if [ -f /etc/passwd ]; then
  RPWD=$(cat /etc/passwd | grep root | cut -d":" -f2)
  if [ ".$RPWD" != ".*" ]; then
    PWDSET=1
  fi
fi

You can do this in one go with awk. Using cat | grep | cut for this isn't necessary.

Here's my version:

#!/bin/sh
if awk -F: '/^root:/ && $2 !~ /\*/ {exit 1}' /etc/passwd 2>/dev/null || test $FAILSAFE; then telnetd -l /bin/login; fi

The discussion might have continued from here.

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