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Installation and Usage of SSL Certificates That Are Signed by Intermediate CA

Technote (FAQ)


What is the proper installation and usage of SSL certificates signed by an intermediate CA?


The proper usage of SSL certificates (for SMTP TLS) that are signed by an intermediate CA is a bit tricky. On firmware 2.8 even uploading the certificates at 'SMTP | TLS Certificates | Upload New Certificates' is not possible (see Technote 1578722 'Manually uploading SSL certificates for TLS' --> When the certificates are uploaded manually - incoming TLS connections will only work when the validity of the certificate is not validated by the sending MTA. This article describes which manual modifications are necessary for a proper usage of such certificates.
For a proper installation of a certificate that is signed by an intermediate CA it is necessary to add the certificate of the intermediate CA to the certificate file.

1. If you do not already have the certificate of the intermediate CA you need to get it:
openssl x509 -in server.cert -text -noout
This command will give you all the information about your certificate. There will be a paragraph that points to certificate of the intermediate CA that has signed your certificate -> 'Authority Information Access'.

Download the certificate (in our example it is:

2. Check if the certificate of the intermediate CA is in PEM format.
openssl x509 -in CERTIFICATE_NAME.crt -text -noout
If it is NOT in PEM format but in DER format you will get an error like:

Convert the certificate from DER to PEM
openssl x509 -inform der -in CERTIFICATE_NAME.crt -out CERTIFICATE_NAME.cert

3. Append the certificate of the intermediate CA to your server certificate.

4. Put the private key and the server certificate in place as described in Technote 1578722 ( You may test the TLS connection with:
openssl s_client -starttls smtp -crlf -connect -CAfile /etc/apache2/ssl.crt/ca-bundle.crt
If the certificate can be successfully verified you should see Verify return code: 0 (ok)

Related information

Technote 1578722

Cross reference information
Segment Product Component Platform Version Edition
Security Proventia Network Mail Security System Firmware 2.6,, 2.8 All Editions

Document information

More support for: Lotus Protector for Mail Security

Software version: 2.5, 2.5.1, 2.8, 2.8.1, 2.8.3

Operating system(s): Platform Independent

Software edition: All Editions

Reference #: 1578783

Modified date: 20 January 2012

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