During my search, I found several ways of signing a SSL Certificate Signing Request:

  1. Using the x509 module:

    openssl x509 -req -days 360 -in server.csr -CA ca.crt -CAkey ca.key -CAcreateserial -out server.crt

  2. Using the ca module:

    openssl ca -cert ca.crt -keyfile ca.key -in server.csr -out server.crt

Note: I am unsure of the use of the right parameters for this one. Please advise correct usage if I am to use it.

What way should one use to sign certificate requests with your Certification Authority? Is one method better than the other (for example, one being deprecated)?

5

3 Answers

1. Using the x509 module openssl x509 ... ... 2 Using the ca module openssl ca ... ...

You are missing the prelude to those commands.

This is a two-step process. First you set up your CA, and then you sign an end entity certificate (a.k.a server or user). Both of the two commands elide the two steps into one. And both assume you have a an OpenSSL configuration file already setup for both CAs and Server (end entity) certificates.

First, create a basic configuration file:

$ touch openssl-ca.cnf

Then, add the following to it:

HOME = . RANDFILE = $ENV::HOME/.rnd #################################################################### [ ca ] default_ca = CA_default # The default ca section [ CA_default ] default_days = 1000 # How long to certify for default_crl_days = 30 # How long before next CRL default_md = sha256 # Use public key default MD preserve = no # Keep passed DN ordering x509_extensions = ca_extensions # The extensions to add to the cert email_in_dn = no # Don't concat the email in the DN copy_extensions = copy # Required to copy SANs from CSR to cert #################################################################### [ req ] default_bits = 4096 default_keyfile = cakey.pem distinguished_name = ca_distinguished_name x509_extensions = ca_extensions string_mask = utf8only #################################################################### [ ca_distinguished_name ] countryName = Country Name (2 letter code) countryName_default = US stateOrProvinceName = State or Province Name (full name) stateOrProvinceName_default = Maryland localityName = Locality Name (eg, city) localityName_default = Baltimore organizationName = Organization Name (eg, company) organizationName_default = Test CA, Limited organizationalUnitName = Organizational Unit (eg, division) organizationalUnitName_default = Server Research Department commonName = Common Name (e.g. server FQDN or YOUR name) commonName_default = Test CA emailAddress = Email Address emailAddress_default = #################################################################### [ ca_extensions ] subjectKeyIdentifier = hash authorityKeyIdentifier = keyid:always, issuer basicConstraints = critical, CA:true keyUsage = keyCertSign, cRLSign

The fields above are taken from a more complex openssl.cnf (you can find it in /usr/lib/openssl.cnf), but I think they are the essentials for creating the CA certificate and private key.

Tweak the fields above to suit your taste. The defaults save you the time from entering the same information while experimenting with configuration file and command options.

I omitted the CRL-relevant stuff, but your CA operations should have them. See openssl.cnf and the related crl_ext section.

Then, execute the following. The -nodes omits the password or passphrase so you can examine the certificate. It's a really bad idea to omit the password or passphrase.

$ openssl req -x509 -config openssl-ca.cnf -newkey rsa:4096 -sha256 -nodes -out cacert.pem -outform PEM

After the command executes, cacert.pem will be your certificate for CA operations, and cakey.pem will be the private key. Recall the private key does not have a password or passphrase.

You can dump the certificate with the following.

$ openssl x509 -in cacert.pem -text -noout Certificate: Data: Version: 3 (0x2) Serial Number: 11485830970703032316 (0x9f65de69ceef2ffc) Signature Algorithm: sha256WithRSAEncryption Issuer: C=US, ST=MD, L=Baltimore, CN=Test CA/emailAddress= Validity Not Before: Jan 24 14:24:11 2014 GMT Not After : Feb 23 14:24:11 2014 GMT Subject: C=US, ST=MD, L=Baltimore, CN=Test CA/emailAddress= Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (4096 bit) Modulus: 00:b1:7f:29:be:78:02:b8:56:54:2d:2c:ec:ff:6d: ... 39:f9:1e:52:cb:8e:bf:8b:9e:a6:93:e1:22:09:8b: 59:05:9f Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Subject Key Identifier: 4A:9A:F3:10:9E:D7:CF:54:79:DE:46:75:7A:B0:D0:C1:0F:CF:C1:8A X509v3 Authority Key Identifier: keyid:4A:9A:F3:10:9E:D7:CF:54:79:DE:46:75:7A:B0:D0:C1:0F:CF:C1:8A X509v3 Basic Constraints: critical CA:TRUE X509v3 Key Usage: Certificate Sign, CRL Sign Signature Algorithm: sha256WithRSAEncryption 4a:6f:1f:ac:fd:fb:1e:a4:6d:08:eb:f5:af:f6:1e:48:a5:c7: ... cd:c6:ac:30:f9:15:83:41:c1:d1:20:fa:85:e7:4f:35:8f:b5: 38:ff:fd:55:68:2c:3e:37

And test its purpose with the following (don't worry about the Any Purpose: Yes; see "critical,CA:FALSE" but "Any Purpose CA : Yes").

$ openssl x509 -purpose -in cacert.pem -inform PEM Certificate purposes: SSL client : No SSL client CA : Yes SSL server : No SSL server CA : Yes Netscape SSL server : No Netscape SSL server CA : Yes S/MIME signing : No S/MIME signing CA : Yes S/MIME encryption : No S/MIME encryption CA : Yes CRL signing : Yes CRL signing CA : Yes Any Purpose : Yes Any Purpose CA : Yes OCSP helper : Yes OCSP helper CA : Yes Time Stamp signing : No Time Stamp signing CA : Yes -----BEGIN CERTIFICATE----- MIIFpTCCA42gAwIBAgIJAJ9l3mnO7y/8MA0GCSqGSIb3DQEBCwUAMGExCzAJBgNV ... aQUtFrV4hpmJUaQZ7ySr/RjCb4KYkQpTkOtKJOU1Ic3GrDD5FYNBwdEg+oXnTzWP tTj//VVoLD43 -----END CERTIFICATE-----

For part two, I'm going to create another configuration file that's easily digestible. First, touch the openssl-server.cnf (you can make one of these for user certificates also).

$ touch openssl-server.cnf

Then open it, and add the following.

HOME = . RANDFILE = $ENV::HOME/.rnd #################################################################### [ req ] default_bits = 2048 default_keyfile = serverkey.pem distinguished_name = server_distinguished_name req_extensions = server_req_extensions string_mask = utf8only #################################################################### [ server_distinguished_name ] countryName = Country Name (2 letter code) countryName_default = US stateOrProvinceName = State or Province Name (full name) stateOrProvinceName_default = MD localityName = Locality Name (eg, city) localityName_default = Baltimore organizationName = Organization Name (eg, company) organizationName_default = Test Server, Limited commonName = Common Name (e.g. server FQDN or YOUR name) commonName_default = Test Server emailAddress = Email Address emailAddress_default = #################################################################### [ server_req_extensions ] subjectKeyIdentifier = hash basicConstraints = CA:FALSE keyUsage = digitalSignature, keyEncipherment subjectAltName = @alternate_names nsComment = "OpenSSL Generated Certificate" #################################################################### [ alternate_names ] DNS.1 = example.com DNS.2 = DNS.3 = mail.example.com DNS.4 = ftp.example.com

If you are developing and need to use your workstation as a server, then you may need to do the following for Chrome. Otherwise Chrome may complain a Common Name is invalid (ERR_CERT_COMMON_NAME_INVALID). I'm not sure what the relationship is between an IP address in the SAN and a CN in this instance.

# IPv4 localhost IP.1 = 127.0.0.1 # IPv6 localhost IP.2 = ::1

Then, create the server certificate request. Be sure to omit -x509*. Adding -x509 will create a certificate, and not a request.

$ openssl req -config openssl-server.cnf -newkey rsa:2048 -sha256 -nodes -out servercert.csr -outform PEM

After this command executes, you will have a request in servercert.csr and a private key in serverkey.pem.

And you can inspect it again.

$ openssl req -text -noout -verify -in servercert.csr Certificate: verify OK Certificate Request: Version: 0 (0x0) Subject: C=US, ST=MD, L=Baltimore, CN=Test Server/emailAddress= Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:ce:3d:58:7f:a0:59:92:aa:7c:a0:82:dc:c9:6d: ... f9:5e:0c:ba:84:eb:27:0d:d9:e7:22:5d:fe:e5:51: 86:e1 Exponent: 65537 (0x10001) Attributes: Requested Extensions: X509v3 Subject Key Identifier: 1F:09:EF:79:9A:73:36:C1:80:52:60:2D:03:53:C7:B6:BD:63:3B:61 X509v3 Basic Constraints: CA:FALSE X509v3 Key Usage: Digital Signature, Key Encipherment X509v3 Subject Alternative Name: DNS:example.com, DNS: DNS:mail.example.com, DNS:ftp.example.com Netscape Comment: OpenSSL Generated Certificate Signature Algorithm: sha256WithRSAEncryption 6d:e8:d3:85:b3:88:d4:1a:80:9e:67:0d:37:46:db:4d:9a:81: ... 76:6a:22:0a:41:45:1f:e2:d6:e4:8f:a1:ca:de:e5:69:98:88: a9:63:d0:a7

Next, you have to sign it with your CA.

You are almost ready to sign the server's certificate by your CA. The CA's openssl-ca.cnf needs two more sections before issuing the command.

First, open openssl-ca.cnf and add the following two sections.

#################################################################### [ signing_policy ] countryName = optional stateOrProvinceName = optional localityName = optional organizationName = optional organizationalUnitName = optional commonName = supplied emailAddress = optional #################################################################### [ signing_req ] subjectKeyIdentifier = hash authorityKeyIdentifier = keyid,issuer basicConstraints = CA:FALSE keyUsage = digitalSignature, keyEncipherment

Second, add the following to the [ CA_default ] section of openssl-ca.cnf. I left them out earlier, because they can complicate things (they were unused at the time). Now you'll see how they are used, so hopefully they will make sense.

base_dir = . certificate = $base_dir/cacert.pem # The CA certifcate private_key = $base_dir/cakey.pem # The CA private key new_certs_dir = $base_dir # Location for new certs after signing database = $base_dir/index.txt # Database index file serial = $base_dir/serial.txt # The current serial number unique_subject = no # Set to 'no' to allow creation of # several certificates with same subject.

Third, touch index.txt and serial.txt:

$ touch index.txt $ echo '01' > serial.txt

Then, perform the following:

$ openssl ca -config openssl-ca.cnf -policy signing_policy -extensions signing_req -out servercert.pem -infiles servercert.csr

You should see similar to the following:

Using configuration from openssl-ca.cnf Check that the request matches the signature Signature ok The Subject's Distinguished Name is as follows countryName :PRINTABLE:'US' stateOrProvinceName :ASN.1 12:'MD' localityName :ASN.1 12:'Baltimore' commonName :ASN.1 12:'Test CA' emailAddress :IA5STRING:'' Certificate is to be certified until Oct 20 16:12:39 2016 GMT (1000 days) Sign the certificate? [y/n]:Y 1 out of 1 certificate requests certified, commit? [y/n]Y Write out database with 1 new entries Data Base Updated

After the command executes, you will have a freshly minted server certificate in servercert.pem. The private key was created earlier and is available in serverkey.pem.

Finally, you can inspect your freshly minted certificate with the following:

$ openssl x509 -in servercert.pem -text -noout Certificate: Data: Version: 3 (0x2) Serial Number: 9 (0x9) Signature Algorithm: sha256WithRSAEncryption Issuer: C=US, ST=MD, L=Baltimore, CN=Test CA/emailAddress= Validity Not Before: Jan 24 19:07:36 2014 GMT Not After : Oct 20 19:07:36 2016 GMT Subject: C=US, ST=MD, L=Baltimore, CN=Test Server Subject Public Key Info: Public Key Algorithm: rsaEncryption Public-Key: (2048 bit) Modulus: 00:ce:3d:58:7f:a0:59:92:aa:7c:a0:82:dc:c9:6d: ... f9:5e:0c:ba:84:eb:27:0d:d9:e7:22:5d:fe:e5:51: 86:e1 Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Subject Key Identifier: 1F:09:EF:79:9A:73:36:C1:80:52:60:2D:03:53:C7:B6:BD:63:3B:61 X509v3 Authority Key Identifier: keyid:42:15:F2:CA:9C:B1:BB:F5:4C:2C:66:27:DA:6D:2E:5F:BA:0F:C5:9E X509v3 Basic Constraints: CA:FALSE X509v3 Key Usage: Digital Signature, Key Encipherment X509v3 Subject Alternative Name: DNS:example.com, DNS: DNS:mail.example.com, DNS:ftp.example.com Netscape Comment: OpenSSL Generated Certificate Signature Algorithm: sha256WithRSAEncryption b1:40:f6:34:f4:38:c8:57:d4:b6:08:f7:e2:71:12:6b:0e:4a: ... 45:71:06:a9:86:b6:0f:6d:8d:e1:c5:97:8d:fd:59:43:e9:3c: 56:a5:eb:c8:7e:9f:6b:7a

Earlier, you added the following to CA_default: copy_extensions = copy. This copies extension provided by the person making the request.

If you omit copy_extensions = copy, then your server certificate will lack the Subject Alternate Names (SANs) like and mail.example.com.

If you use copy_extensions = copy, but don't look over the request, then the requester might be able to trick you into signing something like a subordinate root (rather than a server or user certificate). Which means he/she will be able to mint certificates that chain back to your trusted root. Be sure to verify the request with openssl req -verify before signing.

If you omit unique_subject or set it to yes, then you will only be allowed to create one certificate under the subject's distinguished name.

unique_subject = yes # Set to 'no' to allow creation of # several ctificates with same subject.

Trying to create a second certificate while experimenting will result in the following when signing your server's certificate with the CA's private key:

Sign the certificate? [y/n]:Y failed to update database TXT_DB error number 2

So unique_subject = no is perfect for testing.

If you want to ensure the Organizational Name is consistent between self-signed CAs, Subordinate CA and End-Entity certificates, then add the following to your CA configuration files:

[ policy_match ] organizationName = match

If you want to allow the Organizational Name to change, then use:

[ policy_match ] organizationName = supplied

There are other rules concerning the handling of DNS names in X.509/PKIX certificates. Refer to these documents for the rules:

RFC 6797 and RFC 7469 are listed, because they are more restrictive than the other RFCs and CA/B documents. RFC's 6797 and 7469 do not allow an IP address, either.

23

In addition to answer of @jww, I would like to say that the configuration in openssl-ca.cnf,

default_days = 1000 # How long to certify for

defines the default number of days the certificate signed by this root-ca will be valid. To set the validity of root-ca itself you should use '-days n' option in:

openssl req -x509 -days 3000 -config openssl-ca.cnf -newkey rsa:4096 -sha256 -nodes -out cacert.pem -outform PEM

Failing to do so, your root-ca will be valid for only the default one month and any certificate signed by this root CA will also have validity of one month.

1

Sometimes, such as for testing, you just want a simplistic means of generating a signed certificate, without setting up a full-blown CA configuration. This is possible using just the openssl req and openssl x509 commands. You would never use this method for production certificates, but since it is useful for some non-production situations, here are the commands.

Generate a self-signed signing certificate

First, create a self-signed certificate that will be used as the root of trust:

openssl req -x509 -days 365 -key ca_private_key.pem -out ca_cert.pem

Or equivalently, if you want to generate a private key and a self-signed certificate in a single command:

openssl req -x509 -days 365 -newkey rsa:4096 -keyout ca_private_key.pem -out ca_cert.pem

Generate a certificate request

Next, create a certificate request for the certificate to be signed:

openssl req -new -key my_private_key.pem -out my_cert_req.pem

Again, you may generate the private key and the request simultaneously, if needed:

openssl req -new -newkey rsa:4096 -keyout my_private_key.pem -out my_cert_req.pem

Generate a signed certificate

Finally, use the self-signed signing certificate to generate a signed certificate from the certificate request:

openssl x509 -req -in my_cert_req.pem -days 365 -CA ca_cert.pem -CAkey ca_private_key.pem -CAcreateserial -out my_signed_cert.pem