This is a text-only version of the following page on https://raymii.org:
---
Title       : 	OpenSSL get entire certificate chain from a domain or loop over entire chain in file
Author      : 	Remy van Elst
Date        : 	16-07-2024 18:30
URL         : 	https://raymii.org/s/snippets/OpenSSL_get_entire_certificate_chain_from_a_domain_or_use_all_certs_in_a_file.html
Format      : 	Markdown/HTML
---



The `openssl x509` command can be used to get information from a certificate. If you supply a filename, the command will only use the topmost certificate in the file, not all certificates in the file, like in the case of a certificate chain. The `openssl s_client -connect` command can connect to a server and show all certificates served by that server. The command I'm providing in this snippet splits up all certificates found in a file or as the result of `openssl s_client` and allows `openssl x509` to loop over each one individually. 

<p class="ad"> <b>Recently I removed all Google Ads from this site due to their invasive tracking, as well as Google Analytics. Please, if you found this content useful, consider a small donation using any of the options below:</b><br><br> <a href="https://leafnode.nl">I'm developing an open source monitoring app called  Leaf Node Monitoring, for windows, linux & android. Go check it out!</a><br><br> <a href="https://github.com/sponsors/RaymiiOrg/">Consider sponsoring me on Github. It means the world to me if you show your appreciation and you'll help pay the server costs.</a><br><br> <a href="https://www.digitalocean.com/?refcode=7435ae6b8212">You can also sponsor me by getting a Digital Ocean VPS. With this referral link you'll get $200 credit for 60 days. Spend $25 after your credit expires and I'll get $25!</a><br><br> </p>


The command I use to print the entire certificate chain from a domain is the
following:


	OLDIFS=$IFS; IFS=':' certificates=$(openssl s_client -connect raymii.org:443 -showcerts -tlsextdebug 2>&1 </dev/null | sed -n '/-----BEGIN/,/-----END/{/-----BEGIN/ s/^/:/; p}'); for certificate in ${certificates#:}; do echo $certificate | openssl x509 -noout -subject -issuer  -ext subjectAltName; echo; done; IFS=$OLDIFS

Output:

	subject=CN = raymii.org
	issuer=C = GB, ST = Greater Manchester, L = Salford, O = Sectigo Limited, CN = Sectigo RSA Domain Validation Secure Server CA
	X509v3 Subject Alternative Name:
	    DNS:raymii.org, DNS:www.raymii.org

	subject=C = GB, ST = Greater Manchester, L = Salford, O = Sectigo Limited, CN = Sectigo RSA Domain Validation Secure Server CA
	issuer=C = US, ST = New Jersey, L = Jersey City, O = The USERTRUST Network, CN = USERTrust RSA Certification Authority
	No extensions in certificate

	subject=C = US, ST = New Jersey, L = Jersey City, O = The USERTRUST Network, CN = USERTrust RSA Certification Authority
	issuer=C = US, ST = New Jersey, L = Jersey City, O = The USERTRUST Network, CN = USERTrust RSA Certification Authority
	No extensions in certificate
	

If you have the certificates in a local file, for this example `chain.pem`, this is the command:

    OLDIFS=$IFS; IFS=':' certificates=$(sed -n '/-----BEGIN/,/-----END/{/-----BEGIN/ s/^/:/; p}' chain.pem); for certificate in ${certificates#:}; do echo $certificate | openssl x509 -noout -subject; echo; done; IFS=$OLDIFS

Output:

    subject=CN = raymii.org

    subject=C = GB, ST = Greater Manchester, L = Salford, O = Sectigo Limited, CN = Sectigo RSA Domain Validation Secure Server CA

    subject=C = US, ST = New Jersey, L = Jersey City, O = The USERTRUST Network, CN = USERTrust RSA Certification Authority


You can replace the `openssl x509 -noout -subject -issuer -ext subjectAltName`
by any option supported by `openssl x509`. For this example I choose to echo
the `subject`, `issuer` and `subjectAlternativeNames` but you get the gist. 


Here's a breakdown of what the script does:

- `OLDIFS=$IFS; IFS=':'` - This changes the Internal Field Separator (IFS) to
  `:`. The IFS is a special shell variable used for word splitting after
  expansion and to split lines into words with the read built-in command. The
  original `IFS` is saved in `OLDIFS` to restore it later.

- `certificates=$(openssl s_client [...] |
  sed -n '/-----BEG[...] s/^/:/; p}')` - This uses the
  `openssl` command to connect to `google.nl` on port 443 and extract the SSL
  certificates. The `sed` command is used to format the output so that each
  certificate starts with a `:`.

- `for certificate in ${certificates#:}; do echo [...]` - This loops over each
  certificate (split by `:` due to the `IFS`) and uses `openssl` to extract the
  subject alternative name, subject, and issuer of each certificate.

- `IFS=$OLDIFS` - This restores the original `IFS`.


---

License:
All the text on this website is free as in freedom unless stated otherwise. 
This means you can use it in any way you want, you can copy it, change it 
the way you like and republish it, as long as you release the (modified) 
content under the same license to give others the same freedoms you've got 
and place my name and a link to this site with the article as source.

This site uses Google Analytics for statistics and Google Adwords for 
advertisements. You are tracked and Google knows everything about you. 
Use an adblocker like ublock-origin if you don't want it.

All the code on this website is licensed under the GNU GPL v3 license 
unless already licensed under a license which does not allows this form 
of licensing or if another license is stated on that page / in that software:

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

Just to be clear, the information on this website is for meant for educational 
purposes and you use it at your own risk. I do not take responsibility if you 
screw something up. Use common sense, do not 'rm -rf /' as root for example. 
If you have any questions then do not hesitate to contact me.

See https://raymii.org/s/static/About.html for details.