!_linux_commands

# Some useful commands for reference

cert_related

# check installed ca certs on Ubuntu
awk -v cmd='openssl x509 -n /BEGIN/{close(cmd)};{print | cmd}' < /etc/ssl/certs/ca-certificates.crt

# on bosh director
cat /usr/local/share/ca-certificates/bosh_os_conf_ca_cert_*

openssl s_client -connect www.google.com:443

# test custom root ca cert directly
openssl verify -verbose -x509_strict <(cat root_ca.crt)

cert_name="root_ca.crt"
openssl x509 -in "${cert_name}" -noout -text

curl -v https://www.google.com 1> /dev/null
# varies on OS. Ubuntu hides useful "Server certificate:" info but centos does not
# *   Trying 172.217.8.4...
# * Connected to www.google.com (172.217.8.4) port 443 (#0)
# * Initializing NSS with certpath: sql:/etc/pki/nssdb
# *   CAfile: /etc/pki/tls/certs/ca-bundle.crt
#   CApath: none
# * Server certificate:
# *       subject: CN=www.google.com,O=Google LLC,L=Mountain View,ST=California,C=US
# *       start date: Oct 06 06:41:20 2020 GMT
# *       expire date: Dec 29 06:41:20 2020 GMT
# *       common name: www.google.com
# *       issuer: <clearly intercepted judging by the output here>

exploring_commands

# https://unix.stackexchange.com/a/202326  

# $ type local
# local is a shell builtin

# Bash shell builtins are documented inside man bash and their documentation can be also invoked with help
help type
help local

# $ type -a echo
# echo is a shell builtin
# echo is /usr/bin/echo
# echo is /bin/echo

find

find /home/ubuntu/poc-deployment-pipeline/ \( -type d -name .git -prune \) -o -type f -print0 | xargs -0 sed -i 's/repo-ci/concourse/g'

# https://stackoverflow.com/a/16957078
grep -rnw '/path/to/somewhere/' -e 'pattern'

network_related

# Check IPs in use on a network
nmap -sP 192.168.100.0/24

# Check services in use from https://hackertarget.com/nmap-cheatsheet-a-quick-reference-guide/
Service and OS Detection
# Detect OS and Services	
nmap -A 192.168.1.1
# Standard service detection	
# nmap -sV 192.168.1.1
More aggressive Service Detection	
nmap -sV --version-intensity 5 192.168.1.1
# Lighter banner grabbing detection	
nmap -sV --version-intensity 0 192.168.1.1

windows_crap

# check affected files in a git repo
git grep -I --files-with-matches --perl-regexp '\r' HEAD

# https://stackoverflow.com/questions/14219092/bash-script-and-bin-bashm-bad-interpreter-no-such-file-or-directory
# Specifically https://stackoverflow.com/a/29747593
sed -i -e 's/\r$//' scriptname.sh