How do you sign a Certificate Signing Request with your Certification Authority?
During my search, I found several ways of signing a SSL Certificate Signing Request:
Using the
x509module:openssl x509 -req -days 360 -in server.csr -CA ca.crt -CAkey ca.key -CAcreateserial -out server.crtUsing the
camodule: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)?
Answer
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 = [email protected]
####################################################################
[ 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/[email protected]
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/[email protected]
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 = [email protected]
####################################################################
[ 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 = www.example.com
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/[email protected]
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:www.example.com, 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:'[email protected]'
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/[email protected]
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:www.example.com, 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 www.example.com 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 5280, Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile
- RFC 6125, Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)
- RFC 6797, Appendix A, HTTP Strict Transport Security (HSTS)
- RFC 7469, Public Key Pinning Extension for HTTP
- CA/Browser Forum Baseline Requirements
- CA/Browser Forum Extended Validation Guidelines
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.