aws-host-fingerprints

#! /bin/sh
# aws-host-fingerprints (Bourne shell script) -- extract SSH host key fingerprints from boot log
#
# Keywords: ssh AWS EC2 security

while [ "$(echo "x$1" | cut -c2)" = - ] ; do
  args="$args $1"
  shift
done

self=aws-host-fingerprints

if [ -z "$1" ] ; then
  echo "Usage: $self <instance-id>" >&2
  exit 1
fi

cont=y
while [ $cont = y ]
do
  # Redirect STDERR because 
  aws ec2 --output=text get-console-output $args --instance-id=$1 |
    sed -n '/^ec2: -----BEGIN SSH HOST KEY FINGERPRINTS-----/,/^ec2: -----END SSH HOST KEY FINGERPRINTS-----/p' |
    tee /tmp/aws-host-fingerprints_$$ 2> /tmp/aws-host-fingerprints_errors_$$

  # Check if valid output was produced
  if [ -s /tmp/aws-host-fingerprints_errors_$$ ] && \
       grep -q -v -e "'Output'" -e '^$' /tmp/aws-host-fingerprints_errors_$$
  then
    # if not, loop again
    echo waiting...
    sleep 3
    cont=y
  else
    # print the errors as they would have been if not captured
    cat /tmp/aws-host-fingerprints_errors_$$ >&2
    cont=n
  fi
done

# If there is nothing in the file, throw an error
if [ ! -s /tmp/aws-host-fingerprints_$$ ] ; then
  echo "${self}: Warning: console output for instance $1 does not contain host fingerprints" >&2
  exit 2
fi