Print fingerprints of the keys in $HOME/.ssh/authorized_keys

authorized_fingerprints.sh

#!/bin/sh
# script to print fingerprints of the keys in authorized_keys
set -eu
IFS='
'
if ! which ssh-keygen > /dev/null 2>&1; then
    echo "OpenSSH is needed to run this script" >&2
    exit 1
fi
print_fingerprints() {
    if ssh-keygen -l -E md5 -f "$keyfile" > /dev/null 2>&1; then
        # New OpenSSH, print both SHA256 and MD5 fingerprints
        ssh-keygen -l -E md5 -f "$1"
        ssh-keygen -l -E sha256 -f "$1"
    else
        # Old OpenSSH, print just the MD% fingerprints
        ssh-keygen -l -f "$1"
    fi
}

TMPFILE=$(mktemp -d -p /dev/shm -t key.XXXXX)
trap 'rm -rf $TMPFILE;exit' 0 1 2 15

for line in $(grep -v '^\([[:space:]]*$\|#\)' $HOME/.ssh/authorized_keys \
    | sort -u)
do
    keyfile="$TMPFILE/$(echo $line | awk '{print $3}' | sed 's/\//∕/g')"
    echo $line > $keyfile
    print_fingerprints $keyfile |sed "s/$(echo $TMPFILE \
        | sed 's/\([/]\)/\\\1/g')//;s/\///"
done | sort -k1,1n -k3