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I've got a little private webserver where I have several virtualhosts. I know that it's impossible to assign a certificate to each individual virtualhost, because the server finds out which virtualhost was requested only AFTER the SSL connection has been established. But is it possible to have a single SSL certificate which lists several domains? Or at least a wildcard domain, like *.example.com. If yes, what Linux commands do I have to write to make such a self-signed certificate?

Added: To clarify - I have just one IP address for all the virtual hosts.

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5 Answers 5

To expand on AlberT's answer:

http://blog.loftninjas.org/2008/11/11/configuring-ssl-requests-with-subjectaltname-with-openssl/

You don't have to use wildcard domains. You can just list all hostnames you need as subject alt names and it should work on all major browsers.

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2  
Unfortunately that link is dead. The WayBackMachine still has a record of that blogposting. –  Jpsy Oct 7 '13 at 19:47
    
At the time of this writing, the loftninjas.org link above is active (again). –  Mikhail T. Feb 25 at 17:22

Create a certificate with domain.com as the CN and *.domain.com in the subjectAltName:dNSName names field - that works.

In openssl, add this to the extensions:

subjectAltName          = DNS:*.domain.com
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How does one do that without using a CSR? –  Walf Feb 23 '12 at 1:56

I guess, this might help you : http://adam.shand.net/archives/2007/the_easy_way_to_generate_openssl_csrs_with_subjectaltnames/

What you have to do is to set up subjectAltNames with all the domain you want to use.

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The following should work for you:

cp /etc/ssl/openssl.cnf /tmp
echo '[ subject_alt_name ]' >> /tmp/openssl.cnf
echo 'subjectAltName = DNS:www.example.com, DNS:site1.example.com, DNS:site2.example.com' >> /tmp/openssl.cnf
openssl req -x509 -nodes -newkey rsa:2048 \
  -config /tmp/openssl.cnf \
  -extensions subject_alt_name \
  -keyout www.example.com.key \
  -out www.example.com.pem \
  -subj '/C=XX/ST=XXXX/L=XXXX/O=XXXX/OU=XXXX/CN=www.example.com/emailAddress=postmaster@example.com'

Result:

$ openssl x509 -in www.example.com.pem -text -noout
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 17965603478303142689 (0xf952a52d7bc7f321)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: C=XX, ST=XXXX, L=XXXX, O=XXXX, OU=XXXX, CN=www.example.com/emailAddress=flb.helpdesk@morpho.com
        Validity
            Not Before: Apr  3 15:34:27 2015 GMT
            Not After : May  3 15:34:27 2015 GMT
        Subject: C=XX, ST=XXXX, L=XXXX, O=XXXX, OU=XXXX, CN=www.example.com/emailAddress=flb.helpdesk@morpho.com
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    00:c6:e8:17:93:a4:8f:08:11:61:11:1b:cc:17:52:
                    b6:33:39:33:0e:94:3f:ac:ae:dd:70:4b:e6:d6:b0:
                    11:f1:93:b4:3d:dc:34:99:27:b6:45:4b:13:0c:69:
                    1e:11:d2:b9:38:5f:e0:d1:b0:58:e4:3c:c0:9f:58:
                    3d:5d:fa:67:3e:3c:05:1b:e3:86:20:18:d5:d7:83:
                    77:b5:0c:1d:9a:26:96:10:3f:2c:e5:ce:ed:6e:99:
                    5a:35:3e:06:f0:52:aa:72:5e:c0:33:7c:c8:16:f9:
                    6b:3e:7d:7e:5a:1f:cf:11:63:4d:ad:bf:77:bd:e3:
                    0f:8f:24:1d:f5:c8:06:ab:d9:62:8d:13:56:62:a9:
                    b8:77:c0:11:b6:ff:a7:63:93:a7:22:c2:41:48:6f:
                    bd:42:10:00:33:14:da:3b:ca:e0:07:c2:b6:50:55:
                    f0:4d:6b:0d:eb:87:a8:bd:4d:c6:1b:20:d8:27:68:
                    d0:e2:3b:32:91:b8:8e:cf:25:06:bf:43:fd:8f:96:
                    fa:eb:af:0f:e1:5c:47:06:84:8b:f4:35:0a:a8:f3:
                    7e:af:34:50:7f:62:bc:5e:53:09:90:97:27:cf:9a:
                    56:d7:f6:af:32:92:c4:c9:ab:90:6e:a6:09:20:0b:
                    46:28:22:0b:45:71:b9:17:77:d8:da:63:24:27:5c:
                    60:a5
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Subject Alternative Name: 
                DNS:www.example.com, DNS:site1.example.com, DNS:site2.example.com
    Signature Algorithm: sha256WithRSAEncryption
         83:ce:18:74:f9:17:92:91:bd:82:13:ac:64:e7:de:9e:38:d7:
         26:0f:2d:3e:8f:f2:17:c5:fc:17:06:fb:27:e7:0a:b7:f2:8e:
         bb:18:6e:f4:4c:17:e8:8d:dc:51:d5:d2:e6:1c:72:e4:28:75:
         a2:79:ae:b6:b6:8c:ec:08:08:4d:73:79:b7:22:26:40:ac:38:
         5c:f2:2b:4f:44:60:55:db:90:b3:63:74:ad:e7:26:12:ad:0d:
         ec:4a:cd:4f:7a:a0:54:62:f5:a7:bc:80:c2:fa:34:43:3c:f1:
         aa:f7:6e:4e:e1:80:fb:c7:cc:44:3a:2b:a4:6c:5b:0f:3f:83:
         6e:8d:d5:28:cf:6c:f0:c6:40:4d:c4:d4:3f:9c:9d:a4:47:a7:
         27:d1:5b:2b:5f:0d:bd:3f:7c:2e:19:fa:bc:24:bd:1f:64:81:
         8b:a4:e3:33:10:35:55:f9:73:2d:8b:e8:b8:d7:e3:49:0c:35:
         af:53:df:48:d8:df:ce:b1:5f:6c:74:1c:74:89:45:2e:28:2c:
         1f:fe:d8:a4:44:9c:c7:bc:d8:6a:46:38:df:e3:d0:05:37:27:
         d0:08:e5:93:b8:0e:d9:d9:dd:7c:28:75:18:27:be:4e:72:47:
         13:b9:a2:93:0e:83:e9:b8:49:f4:75:ad:e0:0f:9b:e5:96:4f:
         33:33:f1:27

If you want request instead of self-signed just replace -x509 with -new and -extensions with -reqexts.

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First of all - you can assign a certificate for each individual virtual host - the key is to make different private (and external/public, if you want to make it world accessible) ip address for each virtualhost.

But then yes - alternatively, you can assign a wildcard certificate if your virtual hosts is simply *.example.com.

For the command - there are many results from google - i'll just put an example from here:

http://www.justinsamuel.com/2006/03/11/howto-create-a-self-signed-wildcard-ssl-certificate/

And make sure you enter *.example.com for the Common Name.

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1  
That's the point - I have just one IP address. Guess I was unclear on that. –  Vilx- Oct 13 '09 at 12:52
    
@coolwater - Good advice if I'm setting up a production server at work, which would be in our own /16 block. For those of us with small business connections that only give five static IPs, not really an option. I've dealt with this by limiting myself to five SSL Vhosts, one per IP. –  Jason Antman Oct 13 '09 at 22:06

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