Intermediate Certificates
The "Standard Format" for CRT request files and public signed certificates is
the "Base64 X509" format which is accepted by most servers and browsers.
To chain certificates, append them into a single file starting with your site
certificate first, next the intermediates in the order they are chained.
$cat yourcert.crt intermediate.crt >certificate.crt
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The following ia extracted from a KB Article from Barracuda Networks:
In addition to root CA certificate verification, AsyncOS supports the use of
intermediate certificate verification. Intermediate certificates are certificates
issued by a Trusted Root CA which are then used to create additional certificates
effectively creating a chained line of trust. For example, a certificate may be
issued by godaddy.com who, in turn, is granted the rights to issue certificates
by a Trusted Root CA. The certificate issued by godaddy.com must be validated
against godaddy.com's private key as well as the Trusted Root CA's private key.
If after uploading your SSL certificate you see the error message "Error The
uploaded certificate is invalid. Discarding it.", you may be using an
intermediary SSL certificate. The two most widely trusted SSL certificate
vendors are VeriSign and Equifax. If you obtained your certificate through
GoDaddy, DigiCert, or any other SSL certificate vendor, you will need to
obtain as many intermediate certificates as necessary to relate your SLL
certificate back to the root certificates of either VeriSign or Equifax.
Once you have the intermediate certificates handy, create a new text file
and paste all of the contents of each certificate into that text file, one
after another. Regardless of the file extension, each certificate file should
be a text file; the contents are usually a bunch of text preceded and
followed by a series of dashes. The order in which they are pasted into the
new file does not matter. The extension of the new amalgamated file does not
matter either.
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Thawte Intermediate Certificate Support
In order for the SGC SuperCert to be authenticated correctly to all browsers the
Intermediate Certificate (thawte SGC CA ) must be installed on the server.
The SGC SuperCert is signed by the thawte SGC CA Intermediate Certificate which
is in turn signed by the Verisign Class 3 Public Primary CA Root Certificate
(Root Certificate > Intermediate Certificate > issued Certificate). Because the
Intermediate Certificate is not shipped with any browser and is therefore
untrusted, you have to install both the issued Certificate and the Intermediate
Certificate on the server so that whenever an SSL session is invoked the server
will present the Certificate chain (Intermediate Certificate > issued
Certificate) to the browser and the browser can validate the complete chain
right to the root issuer which is included in the browser and trust the
Certificate.
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Example of a chained CRT file (certificate.crt)
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----