11

I wish to configure OpenSSL such that when running openssl req -new to generate a new certificate signing request, I am prompted for any alternative subject names to include on the CSR.

I have added this line to the [req_attributes] section of my openssl.cnf:

subjectAltName                  = Alternative subject names

This has the desired effect that I am now prompted for SANs when generating a CSR:

$ openssl req -new -out test.csr -key ./test.key                            <<<
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) [US]:
State or Province Name (full name) [New York]:
Locality Name (eg, city) []:
Organization Name (eg, company) [Example Co]:
Organizational Unit Name (eg, section) []:
Common Name (e.g. server FQDN or YOUR name) []:test.example.com
Email Address []:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
Alternative subject names []:DNS:alt1.example.com

In the above example, I have entered DNS:alt1.example.com when prompted for the SANs.

The problem is that the resulting CSR does not appear to be well formatted:

$ openssl req -text -in ./test.csr
Certificate Request:
    Data:
        Version: 0 (0x0)
        Subject: C=US, ST=New York, O=The Banes, CN=test.thebanes.org
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    [...]
                Exponent: 65537 (0x10001)
        Attributes:
            X509v3 Subject Alternative Name:unable to print attribute

OpenSSL complains that it is unable to print the value of the Subject Alternative Name attribute. From examples online (where people hard-code the SANs into their openssl.cnf, rather than prompting for them interactively as I want), I expect to see this instead:

        Attributes:
            X509v3 Subject Alternative Name:
                DNS:alt1.example.com

So, how can I generate a well-formed CSR with interactively prompted SANs?

  • Unfortunately I think there is no solution to do that with "pure" openssl - you would need a script that will mangle its config file for that. :( PS A proven solution to do that in a non-interactive manner is here: stackoverflow.com/a/9158662/2693875 – Greg Dubicki Jan 31 '16 at 13:26
4

I've battled with this little nugget myself ... what a PITA!

My solution: I moved the all of openssl.cnf file into a Template Toolkit file leaving only the sans piece as the replacement piece, then wrapped a perl script around it.

The perl script prompts for the SANs entries, then inserts them into the template, saves the template to a temp file and then I call openssl req with the -config option pointed at the temp file. discard the temp file after the CSR is generated.

You also might want to look at: http://www.openssl.org/docs/apps/config.html

There are others who override $ENV just prior to execution and wrap the call to openssl req in perl or shell and accomplish the same thing in a slightly more efficient manner: http://blog.loftninjas.org/2008/11/11/configuring-ssl-requests-with-subjectaltname-with-openssl/

  • The $ENV solution didn't work for me. :( – Greg Dubicki Jan 31 '16 at 13:21
2

This "subjectAltName" should not be in this section: attributes = req_attributes. But in a section for req_extensions = (call it whatever you want).

And no need for all the BS like

subjectAltName           = Alternative subject names
subjectAltName_default   = DNS:www.g00gle.com

Just type in what you want, how many you want:

subjectAltName = DNS:*.g00gle.com, DNS:g00gle.com, DNS:192.168.1.2

(The last one makes internal access like "https://192.168.1.2" without warning)

So something like:

[ req ]
req_extensions     = my_extensions

[my_extensions]
subjectAltName     = DNS:*.g00gle.com, DNS:g00gle.com, DNS:192.168.1.2

Cheers!

  • 1
    This is NOT what OP asked for - he wanted an interactive solution. – Greg Dubicki Jan 31 '16 at 13:22
  • 1
    Shouldn't IPs be recorded using "IP:192.168.1.2", not a DNS-format record? I noted this discussion from 2013 about bugs between browsers when using DNS or IP to store IP addresses as SANs -- michaelm.info/blog/?p=1281 -- but this bug should be nixed by now. – Chris Woods Dec 8 '17 at 11:21
2

I'm also looking for a solution. And this is, what you want:

[req]
default_bits      = 2048
default_key_file  = private.key.pem
...
...
attributes        = req_attributes

[req_attributes]
subjectAltName = Alternative DNS names, Email adresses or IPs (comma seperated list)
#optional default value
subjectAltName_default = DNS:myhost.com.au,IP:127.0.0.1,EMAIL:my@here.org

And you can get this by prompt for alternative subject name(s) :)

#openssl req -in mytest1/temp.csr.pem -noout -text
    Certificate Request:
    Data:
        Version: 0 (0x0)
        Subject: C=DE, ST=Sachsen, L=Heidenau, O=IT Rab\xC3\xB6se, OU=ssl
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
            RSA Public Key: (1024 bit)
                Modulus (1024 bit):
                    00:d8:cd:14:ca:d0:06:6c:8c:11:e9:52:bc:46:39:
                    c1:cf:5a:6e:dd:3b:a8:85:15:6b:13:82:82:4a:48:
                    cb:53:ea:70:ea:f4:02:b2:ef:b1:41:b2:d7:11:c7:
                    11:ba:07:1b:be:8c:30:bc:60:d2:82:83:a1:e1:19:
                    75:3b:69:03:01:3c:2b:7b:85:f4:2e:a9:58:68:8f:
                    0e:f4:5e:50:e1:3f:9e:cf:46:a0:eb:69:aa:1e:cb:
                    3a:99:cb:1d:93:60:d0:3b:38:96:87:45:19:51:f4:
                    40:72:e5:a7:5e:62:37:41:44:48:64:47:95:14:97:
                    4f:27:d0:0c:e7:6f:c1:e1:37
                Exponent: 65537 (0x10001)
        Attributes:
            X509v3 Subject Alternative Name:DNS:www.google.de,EMAIL:im@you.org
    Signature Algorithm: sha1WithRSAEncryption
        9d:2b:e4:eb:1b:c0:b6:0b:b4:62:a7:4d:01:68:98:68:36:98:
        1e:e9:bc:59:24:0f:1b:32:7b:da:9d:39:a4:0f:2c:70:3e:aa:
        f7:07:e7:6b:9b:3b:00:b3:71:e0:54:07:78:c7:6e:57:e3:89:
        07:e1:93:f1:77:e7:cc:0e:d0:ed:c5:d0:a3:5d:1a:cd:bb:d8:
        5f:64:25:81:1b:a8:2f:ef:c7:84:7a:f6:b8:52:4e:4c:1c:8d:
        83:b7:9b:02:8e:b2:39:68:a1:fe:f1:59:8b:e0:c4:91:f1:a9:
        c7:b3:82:a3:d2:92:2b:e5:79:9f:29:b6:63:e7:cf:9d:17:98:
        fe:70
  • This works when looking at the CSR, but when I create a certificate, it doesn't keep the SAN. – Jess Dec 8 '17 at 18:53
  • If the format correct for SAN? Comma separated list. Check with SAN-prefix DNS only, if not not supported IP, EMAIL. Example: INPUT >> DNS:my.dns.com, DNS:my.otherdns.org – raiserle Dec 10 '17 at 13:59
  • Ok. This is normal function of openssl wtf! You must also provide the SAN to the CA-command as -extensions <string>, or -extfile <file>. mta.openssl.org/pipermail/openssl-users/2016-January/… – raiserle Dec 10 '17 at 22:55

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