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OpenSSL: Manually verify a certificate against a CRL


This article shows you how to manually verfify a certificate against a CRL. CRL stands for Certificate Revocation List and is one way to validate a certificate status. It is an alternative to the OCSP, Online Certificate Status Protocol.

You can read more about CRL’s on Wikipedia.

We will be using OpenSSL in this article. I’m using the following version:

$ openssl version
OpenSSL 1.0.2 22 Jan 2015

Get a certificate with a CRL

First we will need a certificate from a website. I’ll be using Wikipedia as an example here. We can retreive this with the following openssl command:

openssl s_client -connect wikipedia.org:443 2>&1 < /dev/null | sed -n '/-----BEGIN/,/-----END/p'

Save this output to a file, for example, wikipedia.pem:

openssl s_client -connect wikipedia.org:443 2>&1 < /dev/null | sed -n '/-----BEGIN/,/-----END/p' > wikipedia.pem

Now, check if this certificate has an CRL URI:

openssl x509 -noout -text -in wikipedia.pem | grep -A 4 'X509v3 CRL Distribution Points'
X509v3 CRL Distribution Points: 
    Full Name:
      URI:http://crl.globalsign.com/gs/gsorganizationvalsha2g2.crl

If it does not give any output, the certificate has no CRL URI. You cannot valdiate it against a CRL.

Download the CRL:

wget -O crl.der http://crl.globalsign.com/gs/gsorganizationvalsha2g2.crl

The CRL will be in DER (binary) format. The OpenSSL command needs it in PEM (base64 encoded DER) format, so convert it:

openssl crl -inform DER -in crl.der -outform PEM -out crl.pem

Getting the certificate chain

It is required to have the certificate chain together with the certificate you want to validate. So, we need to get the certificate chain for our domain, wikipedia.org. Using the -showcerts option with openssl s_client, we can see all the certificates, including the chain:

openssl s_client -connect wikipedia.org:443 -showcerts 2>&1 < /dev/null

Results in a lot of output, but what we are interested in is the following:

 1 s:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance CA-3
   i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance EV Root CA
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

As you can see, this is number 1. Number 0 is the certificate for Wikipedia, we already have that. If your site has more certificates in its chain, you will see more here. Save them all, in the order OpenSSL sends them (as in, first the one which directly issued your server certificate, then the one that issues that certificate and so on, with the root or most-root at the end of the file) to a file, named chain.pem.

You can use the following command to save all the certificates OpenSSL command returns to a file named chain.pem. See [this article for more information)[https://raymii.org/s/articles/OpenSSLGetallcertificatesfromawebsiteinplaintext.html).

OLDIFS=$IFS; IFS=':' certificates=$(openssl s_client -connect wikipedia.org:443 -showcerts -tlsextdebug -tls1 2>&1 </dev/null | sed -n '/-----BEGIN/,/-----END/ {/-----BEGIN/ s/^/:/; p}'); for certificate in ${certificates#:}; do echo $certificate | tee -a chain.pem ; done; IFS=$OLDIFS 

Combining the CRL and the Chain

The Openssl command needs both the certificate chain and the CRL, in PEM format concatenated together for the validation to work. You can omit the CRL, but then the CRL check will not work, it will just validate the certificate against the chain.

cat chain.pem crl.pem > crl_chain.pem

OpenSSL Verify

We now have all the data we need can validate the certificate.

$ openssl verify -crl_check -CAfile crl_chain.pem wikipedia.pem 
wikipedia.pem: OK

Above shows a good certificate status.

Revoked certificate

If you have a revoked certificate, you can also test it the same way as stated above. The response looks like this:

$ openssl verify -crl_check -CAfile crl_chain.pem revoked-test.pem 
revoked-test.pem: OU = Domain Control Validated, OU = PositiveSSL, CN = xs4all.nl
error 23 at 0 depth lookup:certificate revoked

You can test this using the certificate and chain on the Verisign revoked certificate test page: https://test-sspev.verisign.com:2443/test-SSPEV-revoked-verisign.html.

OpenSSL: Manually verify a certificate against an OCSP


This article shows you how to manually verfify a certificate against an OCSP server. OCSP stands for the Online Certificate Status Protocol and is one way to validate a certificate status. It is an alternative to the CRL, certificate revocation list.

Compared to CRL’s:

  • Since an OCSP response contains less information than a typical CRL (certificate revocation list), OCSP can use networks and client resources more efficiently.
  • Using OCSP, clients do not need to parse CRLs themselves, saving client-side complexity. However, this is balanced by the practical need to maintain a cache. In practice, such considerations are of little consequence, since most applications rely on third-party libraries for all X.509 functions.
  • OCSP discloses to the responder that a particular network host used a particular certificate at a particular time. OCSP does not mandate encryption, so other parties may intercept this information.

You can read more about the OCSP on wikipedia

We will be using OpenSSL in this article. I’m using the following version:

$ openssl version
OpenSSL 1.0.1g 7 Apr 2014

Get a certificate with an OCSP

First we will need a certificate from a website. I’ll be using Wikipedia as an example here. We can retreive this with the following openssl command:

openssl s_client -connect wikipedia.org:443 2>&1 < /dev/null | sed -n '/-----BEGIN/,/-----END/p'

Save this output to a file, for example, wikipedia.pem:

openssl s_client -connect wikipedia.org:443 2>&1 < /dev/null | sed -n '/-----BEGIN/,/-----END/p' > wikipedia.pem

Now, check if this certificate has an OCSP URI:

openssl x509 -noout -ocsp_uri -in wikipedia.pem
http://ocsp.digicert.com

If it does not give any output, the certificate has no OCSP URI. You cannot valdiate it against an OCSP.

Getting the certificate chain

It is required to send the certificate chain along with the certificate you want to validate. So, we need to get the certificate chain for our domain, wikipedia.org. Using the -showcerts option with openssl s_client, we can see all the certificates, including the chain:

openssl s_client -connect wikipedia.org:443 -showcerts 2>&1 < /dev/null

Results in a boatload of output, but what we are interested in is the following:

 1 s:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance CA-3
   i:/C=US/O=DigiCert Inc/OU=www.digicert.com/CN=DigiCert High Assurance EV Root CA
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

As you can see, this is number 1. Number 0 is the certificate for Wikipedia, we already have that. If your site has more certificates in its chain, you will see more here. Save them all, in the order OpenSSL sends them (as in, first the one which directly issued your server certificate, then the one that issues that certificate and so on, with the root or most-root at the end of the file) to a file, named chain.pem.

Sending the OCSP request

We now have all the data we need to do an OCSP request. Using the following Openssl command we can send an OCSP request and only get the text output:

openssl ocsp -issuer chain.pem -cert wikipedia.pem -text -url http://ocsp.digicert.com

Results in:

OCSP Request Data:
    Version: 1 (0x0)
    Requestor List:
        Certificate ID:
          Hash Algorithm: sha1
          Issuer Name Hash: ED48ADDDCB7B00E20E842AA9B409F1AC3034CF96
          Issuer Key Hash: 50EA7389DB29FB108F9EE50120D4DE79994883F7
          Serial Number: 0114195F66FAFF8FD66E12496E516F4F
    Request Extensions:
        OCSP Nonce:
            0410DA634F2ADC31DC48AE89BE64E8252D12
OCSP Response Data:
    OCSP Response Status: successful (0x0)
    Response Type: Basic OCSP Response
    Version: 1 (0x0)
    Responder Id: 50EA7389DB29FB108F9EE50120D4DE79994883F7
    Produced At: Apr  9 08:45:00 2014 GMT
    Responses:
    Certificate ID:
      Hash Algorithm: sha1
      Issuer Name Hash: ED48ADDDCB7B00E20E842AA9B409F1AC3034CF96
      Issuer Key Hash: 50EA7389DB29FB108F9EE50120D4DE79994883F7
      Serial Number: 0114195F66FAFF8FD66E12496E516F4F
    Cert Status: good
    This Update: Apr  9 08:45:00 2014 GMT
    Next Update: Apr 16 09:00:00 2014 GMT

    Signature Algorithm: sha1WithRSAEncryption
         56:21:4c:dc:84:21:f7:a8:ac:a7:b9:bc:10:19:f8:19:f1:34:
         c1:63:ca:14:7f:8f:5a:85:2a:cc:02:b0:f8:b5:05:4a:0f:28:
         50:2a:4a:4d:04:01:b5:05:ef:a5:88:41:d8:9d:38:00:7d:76:
         1a:aa:ff:21:50:68:90:d2:0c:93:85:49:e7:8e:f1:58:08:77:
         a0:4e:e2:22:98:01:b7:e3:27:75:11:f5:b7:8f:e0:75:7d:19:
         9b:74:cf:05:dc:ae:1c:36:09:95:b6:08:bc:e7:3f:ea:a2:e3:
         ae:d7:8f:c0:9d:8e:c2:37:67:c7:5b:d8:b0:67:23:f1:51:53:
         26:c2:96:b0:1a:df:4e:fb:4e:e3:da:a3:98:26:59:a8:d7:17:
         69:87:a3:68:47:08:92:d0:37:04:6b:49:9a:96:9d:9c:b1:e8:
         cb:dc:68:7b:4a:4d:cb:08:f7:92:67:41:99:b6:54:56:80:0c:
         18:a7:24:53:ac:c6:da:1f:4d:f4:3c:7d:68:44:1d:a4:df:1d:
         48:07:85:52:86:59:46:d1:35:45:1a:c7:6b:6b:92:de:24:ae:
         c0:97:66:54:29:7a:c6:86:a6:da:9f:06:24:dc:ac:80:66:95:
         e0:eb:49:fd:fb:d4:81:6a:2b:81:41:57:24:78:3b:e0:66:70:
         d4:2e:52:92
wikipedia.pem: good
    This Update: Apr  9 08:45:00 2014 GMT
    Next Update: Apr 16 09:00:00 2014 GMT

If you want to have a more summarized output, leave out the -text option. I most of the time include it to find out problems with an OCSP.

This is how a good certificate status looks:

openssl ocsp -issuer chain.pem -cert wikipedia.pem -url http://ocsp.digicert.com
wikipedia.pem: good
    This Update: Apr  9 08:45:00 2014 GMT
    Next Update: Apr 16 09:00:00 2014 GMT

Revoked certificate

If you have a revoked certificate, you can also test it the same way as stated above. The response looks like this:

Response verify OK
test-revoked.pem: revoked
    This Update: Apr  9 03:02:45 2014 GMT
    Next Update: Apr 10 03:02:45 2014 GMT
    Revocation Time: Mar 25 15:45:55 2014 GMT

You can test this using the certificate and chain on the Verisign revoked certificate test page: https://test-sspev.verisign.com:2443/test-SSPEV-revoked-verisign.html

Other errors

If we send this request to another OCSP, one who did not issued this certificate, we should receive an unauthorized error:

openssl ocsp -issuer chain.pem -cert wikipedia.pem -url http://rapidssl-ocsp.geotrust.com
Responder Error: unauthorized (6)

The -text option here shows more information:

OCSP Request Data:
    Version: 1 (0x0)
    Requestor List:
        Certificate ID:
          Hash Algorithm: sha1
          Issuer Name Hash: ED48ADDDCB7B00E20E842AA9B409F1AC3034CF96
          Issuer Key Hash: 50EA7389DB29FB108F9EE50120D4DE79994883F7
          Serial Number: 0114195F66FAFF8FD66E12496E516F4F
    Request Extensions:
        OCSP Nonce:
            041015BB718C43C46C41122E841DB2282ECE
Responder Error: unauthorized (6)

Some OCSP’s are configured differently and give out this error:

openssl ocsp -issuer chain.pem -cert wikipedia.pem -url http://ocsp.digidentity.eu/L4/services/ocsp
Response Verify Failure
140735308649312:error:2706B06F:OCSP routines:OCSP_CHECK_IDS:response contains no revocation data:ocsp_vfy.c:269:
140735308649312:error:2706B06F:OCSP routines:OCSP_CHECK_IDS:response contains no revocation data:ocsp_vfy.c:269:
wikipedia.pem: ERROR: No Status found.

If we do include the -text option here we can see that a response is sent, however, that it has no data in it:

OCSP Response Data:
    OCSP Response Status: successful (0x0)
    Response Type: Basic OCSP Response
    Version: 1 (0x0)
    Responder Id: C = NL, O = Digidentity B.V., CN = Digidentity OCSP
    Produced At: Apr  9 12:02:00 2014 GMT
    Responses:
    Response Extensions:
OCSP Nonce:
    0410EB540472EA2D8246E88F3317B014BEEF
Signature Algorithm: sha256WithRSAEncryption

Other OCSP’s give out the “unknown” status:

openssl ocsp -issuer chain.pem -cert wikipedia.pem  -url http://ocsp.quovadisglobal.com/
Response Verify Failure
140735308649312:error:27069070:OCSP routines:OCSP_basic_verify:root ca not trusted:ocsp_vfy.c:152:
wikipedia.pem: unknown
    This Update: Apr  9 12:09:18 2014 GMT

The -text options shows us more:

OCSP Response Data:
    OCSP Response Status: successful (0x0)
    Response Type: Basic OCSP Response
    Version: 1 (0x0)
    Responder Id: C = CH, O = QuoVadis Limited, OU = OCSP Responder, CN = QuoVadis OCSP Authority Signature
    Produced At: Apr  9 12:09:10 2014 GMT
    Responses:
    Certificate ID:
      Hash Algorithm: sha1
      Issuer Name Hash: ED48ADDDCB7B00E20E842AA9B409F1AC3034CF96
      Issuer Key Hash: 50EA7389DB29FB108F9EE50120D4DE79994883F7
      Serial Number: 0114195F66FAFF8FD66E12496E516F4F
    Cert Status: unknown
    This Update: Apr  9 12:09:10 2014 GMT

    Response Extensions:

Sources

OpenSSL command line Root and Intermediate CA including OCSP, CRL and revocation


These are quick and dirty notes on generating a certificate authority (CA), intermediate certificate authorities and end certificates using OpenSSL. It includes OCSP, CRL and CA Issuer information and specific issue and expiry dates.

We’ll set up our own root CA. We’ll use the root CA to generate an example intermediate CA. We’ll use the intermediate CA to sign end user certificates.

Root CA

Create and move in to a folder for the root ca:

mkdir ~/SSLCA/root/
cd ~/SSLCA/root/

Generate a 8192-bit long SHA-256 RSA key for our root CA:

openssl genrsa -aes256 -out rootca.key 8192

Example output:

Generating RSA private key, 8192 bit long modulus
.........++
....................................................................................................................++
e is 65537 (0x10001)

If you want to password-protect this key, add the option -aes256.

Create the self-signed root CA certificate ca.crt; you’ll need to provide an identity for your root CA:

openssl req -sha256 -new -x509 -days 1826 -key rootca.key -out rootca.crt

Example output:

You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:NL
State or Province Name (full name) [Some-State]:Zuid Holland
Locality Name (eg, city) []:Rotterdam
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Sparkling Network
Organizational Unit Name (eg, section) []:Sparkling CA
Common Name (e.g. server FQDN or YOUR name) []:Sparkling Root CA
Email Address []:

Create a few files where the CA will store it’s serials:

touch certindex
echo 1000 > certserial
echo 1000 > crlnumber

Place the CA config file. This file has stubs for CRL and OCSP endpoints.

# vim ca.conf
[ ca ]
default_ca = myca

[ crl_ext ]
issuerAltName=issuer:copy 
authorityKeyIdentifier=keyid:always

 [ myca ]
 dir = ./
 new_certs_dir = $dir
 unique_subject = no
 certificate = $dir/rootca.crt
 database = $dir/certindex
 private_key = $dir/rootca.key
 serial = $dir/certserial
 default_days = 730
 default_md = sha1
 policy = myca_policy
 x509_extensions = myca_extensions
 crlnumber = $dir/crlnumber
 default_crl_days = 730

 [ myca_policy ]
 commonName = supplied
 stateOrProvinceName = supplied
 countryName = optional
 emailAddress = optional
 organizationName = supplied
 organizationalUnitName = optional

 [ myca_extensions ]
 basicConstraints = critical,CA:TRUE
 keyUsage = critical,any
 subjectKeyIdentifier = hash
 authorityKeyIdentifier = keyid:always,issuer
 keyUsage = digitalSignature,keyEncipherment,cRLSign,keyCertSign
 extendedKeyUsage = serverAuth
 crlDistributionPoints = @crl_section
 subjectAltName  = @alt_names
 authorityInfoAccess = @ocsp_section

 [ v3_ca ]
 basicConstraints = critical,CA:TRUE,pathlen:0
 keyUsage = critical,any
 subjectKeyIdentifier = hash
 authorityKeyIdentifier = keyid:always,issuer
 keyUsage = digitalSignature,keyEncipherment,cRLSign,keyCertSign
 extendedKeyUsage = serverAuth
 crlDistributionPoints = @crl_section
 subjectAltName  = @alt_names
 authorityInfoAccess = @ocsp_section

 [alt_names]
 DNS.0 = Sparkling Intermidiate CA 1
 DNS.1 = Sparkling CA Intermidiate 1

 [crl_section]
 URI.0 = http://pki.sparklingca.com/SparklingRoot.crl
 URI.1 = http://pki.backup.com/SparklingRoot.crl

 [ocsp_section]
 caIssuers;URI.0 = http://pki.sparklingca.com/SparklingRoot.crt
 caIssuers;URI.1 = http://pki.backup.com/SparklingRoot.crt
 OCSP;URI.0 = http://pki.sparklingca.com/ocsp/
 OCSP;URI.1 = http://pki.backup.com/ocsp/

If you need to set a specific certificate start / expiry date, add the following to [myca]

# format: YYYYMMDDHHMMSS
default_enddate = 20191222035911
default_startdate = 20181222035911

Creating Intermediate 1 CA

Generate the intermediate CA’s private key:

openssl genrsa -out intermediate1.key 4096

Generate the intermediate1 CA’s CSR:

openssl req -new -sha256 -key intermediate1.key -out intermediate1.csr

Example output:

You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:NL
State or Province Name (full name) [Some-State]:Zuid Holland
Locality Name (eg, city) []:Rotterdam
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Sparkling Network
Organizational Unit Name (eg, section) []:Sparkling CA
Common Name (e.g. server FQDN or YOUR name) []:Sparkling Intermediate CA
Email Address []:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

Make sure the subject (CN) of the intermediate is different from the root.

Sign the intermediate1 CSR with the Root CA:

openssl ca -batch -config ca.conf -notext -in intermediate1.csr -out intermediate1.crt

Example Output:

Using configuration from ca.conf
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
countryName           :PRINTABLE:'NL'
stateOrProvinceName   :ASN.1 12:'Zuid Holland'
localityName          :ASN.1 12:'Rotterdam'
organizationName      :ASN.1 12:'Sparkling Network'
organizationalUnitName:ASN.1 12:'Sparkling CA'
commonName            :ASN.1 12:'Sparkling Intermediate CA'
Certificate is to be certified until Mar 30 15:07:43 2017 GMT (730 days)

Write out database with 1 new entries
Data Base Updated

Generate the CRL (both in PEM and DER):

openssl ca -config ca.conf -gencrl -keyfile rootca.key -cert rootca.crt -out rootca.crl.pem

openssl crl -inform PEM -in rootca.crl.pem -outform DER -out rootca.crl

Generate the CRL after every certificate you sign with the CA.

If you ever need to revoke the this intermediate cert:

openssl ca -config ca.conf -revoke intermediate1.crt -keyfile rootca.key -cert rootca.crt

Configuring the Intermediate CA 1

Create a new folder for this intermediate and move in to it:

mkdir ~/SSLCA/intermediate1/
cd ~/SSLCA/intermediate1/

Copy the Intermediate cert and key from the Root CA:

cp ~/SSLCA/root/intermediate1.key ./
cp ~/SSLCA/root/intermediate1.crt ./

Create the index files:

touch certindex
echo 1000 > certserial
echo 1000 > crlnumber

Create a new ca.conf file:

# vim ca.conf
[ ca ]
default_ca = myca

[ crl_ext ]
issuerAltName=issuer:copy 
authorityKeyIdentifier=keyid:always

 [ myca ]
 dir = ./
 new_certs_dir = $dir
 unique_subject = no
 certificate = $dir/intermediate1.crt
 database = $dir/certindex
 private_key = $dir/intermediate1.key
 serial = $dir/certserial
 default_days = 365
 default_md = sha1
 policy = myca_policy
 x509_extensions = myca_extensions
 crlnumber = $dir/crlnumber
 default_crl_days = 365

 [ myca_policy ]
 commonName = supplied
 stateOrProvinceName = supplied
 countryName = optional
 emailAddress = optional
 organizationName = supplied
 organizationalUnitName = optional

 [ myca_extensions ]
 basicConstraints = critical,CA:FALSE
 keyUsage = critical,any
 subjectKeyIdentifier = hash
 authorityKeyIdentifier = keyid:always,issuer
 keyUsage = digitalSignature,keyEncipherment
 extendedKeyUsage = serverAuth
 crlDistributionPoints = @crl_section
 subjectAltName  = @alt_names
 authorityInfoAccess = @ocsp_section

 [alt_names]
 DNS.0 = example.com
 DNS.1 = example.org

 [crl_section]
 URI.0 = http://pki.sparklingca.com/SparklingIntermidiate1.crl
 URI.1 = http://pki.backup.com/SparklingIntermidiate1.crl

 [ocsp_section]
 caIssuers;URI.0 = http://pki.sparklingca.com/SparklingIntermediate1.crt
 caIssuers;URI.1 = http://pki.backup.com/SparklingIntermediate1.crt
 OCSP;URI.0 = http://pki.sparklingca.com/ocsp/
 OCSP;URI.1 = http://pki.backup.com/ocsp/

Change the [alt_names] section to whatever you need as Subject Alternative names. Remove it including thesubjectAltName = @alt_names line if you don’t want a Subject Alternative Name.

If you need to set a specific certificate start / expiry date, add the following to [myca]

# format: YYYYMMDDHHMMSS
default_enddate = 20191222035911
default_startdate = 20181222035911

Generate an empty CRL (both in PEM and DER):

openssl ca -config ca.conf -gencrl -keyfile rootca.key -cert rootca.crt -out rootca.crl.pem

openssl crl -inform PEM -in rootca.crl.pem -outform DER -out rootca.crl

Creating end user certificates

We use this new intermediate CA to generate an end user certificate. Repeat these steps for every end user certificate you want to sign with this CA.

mkdir enduser-certs

Generate the end user’s private key:

openssl genrsa -out enduser-certs/enduser-example.com.key 4096

Generate the end user’s CSR:

openssl req -new -sha256 -key enduser-certs/enduser-example.com.key -out enduser-certs/enduser-example.com.csr

Example output:

You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:NL
State or Province Name (full name) [Some-State]:Noord Holland
Locality Name (eg, city) []:Amsterdam
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Example Inc
Organizational Unit Name (eg, section) []:IT Dept
Common Name (e.g. server FQDN or YOUR name) []:example.com
Email Address []:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

Sign the end user’s CSR with the Intermediate 1 CA:

openssl ca -batch -config ca.conf -notext -in enduser-certs/enduser-example.com.csr -out enduser-certs/enduser-example.com.crt

Example output:

Using configuration from ca.conf
Check that the request matches the signature
Signature ok
The Subject's Distinguished Name is as follows
countryName           :PRINTABLE:'NL'
stateOrProvinceName   :ASN.1 12:'Noord Holland'
localityName          :ASN.1 12:'Amsterdam'
organizationName      :ASN.1 12:'Example Inc'
organizationalUnitName:ASN.1 12:'IT Dept'
commonName            :ASN.1 12:'example.com'
Certificate is to be certified until Mar 30 15:18:26 2016 GMT (365 days)

Write out database with 1 new entries
Data Base Updated

Generate the CRL (both in PEM and DER):

openssl ca -config ca.conf -gencrl -keyfile intermediate1.key -cert intermediate1.crt -out intermediate1.crl.pem

openssl crl -inform PEM -in intermediate1.crl.pem -outform DER -out intermediate1.crl

Generate the CRL after every certificate you sign with the CA.

If you ever need to revoke the this end users cert:

openssl ca -config ca.conf -revoke enduser-certs/enduser-example.com.crt -keyfile intermediate1.key -cert intermediate1.crt

Example output:

Using configuration from ca.conf
Revoking Certificate 1000.
Data Base Updated

Create the certificate chain file by concatenating the Root and intermediate 1 certificates together.

cat ../root/rootca.crt intermediate1.crt > enduser-certs/enduser-example.com.chain

Send the following files to the end user:

enduser-example.com.crt
enduser-example.com.key
enduser-example.com.chain

You can also let the end user supply their own CSR and just send them the .crt file. Do not delete that from the server, otherwise you cannot revoke it.

Validating the certificate

You can validate the end user certificate against the chain using the following command:

openssl verify -CAfile enduser-certs/enduser-example.com.chain enduser-certs/enduser-example.com.crt 
enduser-certs/enduser-example.com.crt: OK

You can also validate it against the CRL. Concatenate the PEM CRL and the chain together first:

cat ../root/rootca.crt intermediate1.crt intermediate1.crl.pem > enduser-certs/enduser-example.com.crl.chain

Verify the certificate:

openssl verify -crl_check -CAfile enduser-certs/enduser-example.com.crl.chain enduser-certs/enduser-example.com.crt

Output when not revoked:

enduser-certs/enduser-example.com.crt: OK

Output when revoked:

enduser-certs/enduser-example.com.crt: CN = example.com, ST = Noord Holland, C = NL, O = Example Inc, OU = IT Dept
error 23 at 0 depth lookup:certificate revoked