Using openssl to get the certificate from a server

问题:

I am trying to get the certificate of a remote server, which I can then use to add to my keystore and use within my java application.

A senior dev (who is on holidays :( ) informed me I can run this:

openssl s_client -connect host.host:9999

To get a raw certificate dumped out, which I can then copy and export. I receive the following output:

depth=1 /C=NZ/ST=Test State or Province/O=Organization Name/OU=Organizational Unit Name/CN=Test CA
verify error:num=19:self signed certificate in certificate chain
verify return:0
23177:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure:s3_pkt.c:1086:SSL alert number 40
23177:error:140790E5:SSL routines:SSL23_WRITE:ssl handshake failure:s23_lib.c:188:

I have also tried with this option

-showcerts 

and this one (running on debian mind you)

-CApath /etc/ssl/certs/ 

But get the same error.

This source says I can use that CApath flag but it doesn't seem to help. I tried multiple paths to no avail.

Please let me know where I'm going wrong.

回答1:

With SNI

If the remote server is using SNI (that is, sharing multiple SSL hosts on a single IP address) you will need to send the correct hostname in order to get the right certificate.

openssl s_client -showcerts -servername www.example.com -connect www.example.com:443 </dev/null

Without SNI

If the remote server is not using SNI, then you can skip -servername parameter:

openssl s_client -showcerts -connect www.example.com:443 </dev/null

To view the full details of a site's cert you can use this chain of commands as well:

$ echo | \
    openssl s_client -servername www.example.com -connect www.example.com:443 2>/dev/null | \
    openssl x509 -text

回答2:

While I agree with Ari's answer (and upvoted it :), I needed to do an extra step to get it to work with Java on Windows (where it needed to be deployed):

openssl s_client -showcerts -connect www.example.com:443 < /dev/null | openssl x509 -outform DER > derp.der

Before adding the openssl x509 -outform DER conversion, I was getting an error from keytool on Windows complaining about the certificate's format. Importing the .der file worked fine.

回答3:

It turns out there is more complexity here: I needed to provide many more details to get this rolling. I think its something to do with the fact that its a connection that needs client authentication, and the hankshake needed more info to continue to the stage where the certificates were dumped.

Here is my working command:

openssl s_client -connect host:port -key our_private_key.pem -showcerts \
                 -cert our_server-signed_cert.pem

Hopefully this is a nudge in the right direction for anyone who could do with some more info.

回答4:

The easiest command line for this, which includes the PEM output to add it to the keystore, as well as a human readable output and also supports SNI, which is important if you are working with an HTTP server is:

openssl s_client -servername example.com -connect example.com:443 \
    </dev/null 2>/dev/null | openssl x509 -text

The -servername option is to enable SNI support and the openssl x509 -text prints the certificate in human readable format.

回答5:

To get the certificate of remote server you can use openssl tool and you can find it between BEGIN CERTIFICATE and END CERTIFICATE which you need to copy and paste into your certificate file (CRT).

Here is the command demonstrating it:

ex +'/BEGIN CERTIFICATE/,/END CERTIFICATE/p' <(echo | openssl s_client -showcerts -connect example.com:443) -scq > file.crt

To return all certificates from the chain, just add g (global) like:

ex +'g/BEGIN CERTIFICATE/,/END CERTIFICATE/p' <(echo | openssl s_client -showcerts -connect example.com:443) -scq

Then you can simply import your certificate file (file.crt) into your keychain and make it trusted, so Java shouldn't complain.

On OS X you can double-click on the file or drag and drop in your Keychain Access, so it'll appear in login/Certificates. Then double-click on the imported certificated and make it Always Trust for SSL.

On CentOS 5 you can append them into /etc/pki/tls/certs/ca-bundle.crt file (and run: sudo update-ca-trust force-enable), or in CentOS 6 copy them into /etc/pki/ca-trust/source/anchors/ and run sudo update-ca-trust extract.

In Ubuntu, copy them into /usr/local/share/ca-certificates and run sudo update-ca-certificates.

回答6:

HOST=gmail-pop.l.google.com
PORT=995

openssl s_client -servername $HOST -connect $HOST:$PORT < /dev/null 2>/dev/null | openssl x509 -outform pem

回答7:

You can get and store the server root certificate using next bash script:

CERTS=$(echo -n | openssl s_client -connect $HOST_NAME:$PORT -showcerts | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p')
echo "$CERTS" | awk -v RS="-----BEGIN CERTIFICATE-----" 'NR > 1 { printf RS $0 > "'$SERVER_ROOT_CERTIFICATE'"; close("'$SERVER_ROOT_CERTIFICATE'") }'

Just overwrite required variables.

回答8:

to print only the certificate chain and not the server's certificate:

# MYHOST=myhost.com
# MYPORT=443
# openssl s_client -connect ${MYHOST}:${MYPORT} -showcerts 2>/dev/null </dev/null | awk '/^.*'"${MYHOST}"'/,/-----END CERTIFICATE-----/{next;}/-----BEGIN/,/-----END CERTIFICATE-----/{print}'

to update CA trust on CentOS/RHEL 6/7 :

# update-ca-trust enable
# openssl s_client -connect ${MYHOST}:${MYPORT} -showcerts 2>/dev/null </dev/null | awk '/^.*'"${MYHOST}"'/,/-----END CERTIFICATE-----/{next;}/-----BEGIN/,/-----END CERTIFICATE-----/{print}' >/etc/pki/ca-trust/source/anchors/myca.cert
# update-ca-trust extract

on CentOS/RHEL 5:

# openssl s_client -connect ${MYHOST}:${MYPORT} -showcerts 2>/dev/null </dev/null | awk '/^.*'"${MYHOST}"'/,/-----END CERTIFICATE-----/{next;}/-----BEGIN/,/-----END CERTIFICATE-----/{print}' >>/etc/pki/tls/certs/ca-bundle.crt

回答9:

A one-liner to extract the certificate from a remote server in PEM format, this time using sed:

openssl s_client -connect www.google.com:443 2>/dev/null </dev/null |  sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p'

回答10:

For the benefit of others like me who tried to follow the good advice here when accessing AWS CloudFront but failed, the trick is to add -servername domain.name...

Source: https://serverfault.com/a/780450/8972