postfix tls subcommand
The following subcommands are available:
Specify randsource to update the value of the tls_random_source configuration parameter (typically, /dev/urandom). Prepend dev: to device paths or egd: to EGD socket paths.
See also the all-default-client subcommand.
The randsource parameter is as with enable-client above, and the remaining options are as with new-server-key below.
See also the all-default-server subcommand.
The algorithm defaults to rsa, and bits defaults to 2048. If you choose the ecdsa algorithm then bits will be an EC curve name (by default secp256r1, also known as prime256v1). Curves other than secp256r1, secp384r1 or secp521r1 are unlikely to be widely interoperable. When generating EC keys, use one of these three. DSA keys are obsolete and are not supported.
Note: ECDSA support requires OpenSSL 1.0.0 or later and may not be available on your system. Not all client systems will support ECDSA, so you'll generally want to deploy both RSA and ECDSA certificates to make use of ECDSA with compatible clients and RSA with the rest. If you want to deploy certificate chains with intermediate CAs for both RSA and ECDSA, you'll want at least OpenSSL 1.0.2, as earlier versions may not handle multiple chain files correctly.
The first hostname argument will be the CommonName of both the subject and issuer of the self-signed certificate. It, and any additional hostname arguments, will also be listed as DNS alternative names in the certificate. If no hostname is provided the value of the myhostname main.cf parameter will be used.
For RSA, the generated private key and certificate files are named key-yyyymmdd-hhmmss.pem and cert-yyyymmdd-hhmmss.pem, where yyyymmdd is the calendar date and hhmmss is the time of day in UTC. For ECDSA, the file names start with eckey- and eccert- instead of key- and cert- respectively.
Before deploying the new key and certificate with DANE, update the DNS with new DANE TLSA records, then wait for secondary nameservers to update and then for stale records in remote DNS caches to expire.
Before deploying a new CA certificate make sure to include all the required intermediate issuing CA certificates in the certificate chain file. The server certificate must be the first certificate in the chain file. Overwrite and deploy the file with the original self-signed certificate that was generated together with the key.
This command is rarely needed, because the self-signed certificates generated have a 100-year nominal expiration time. The underlying public key algorithms may well be obsoleted by quantum computers long before then.
The most plausible reason for using this command is when the system hostname changes, and you'd like the name in the certificate to match the new hostname (not required for DANE "3 1 1", but some needlessly picky non-DANE opportunistic TLS clients may log warnings or even refuse to communicate).
Instead of an absolute pathname or a pathname relative to $config_directory, keyfile may specify one of the supported key algorithm names (see "postconf -T public-key-algorithms"). In that case, the corresponding setting from main.cf is used to locate the keyfile. The default keyfile value is rsa.
Zero or more hostname values can be specified. The default hostname is the value of myhostname main.cf parameter.
Instead of absolute pathnames or pathnames relative to $config_directory, the keyfile list may specify names of supported public key algorithms (see "postconf -T public-key-algorithms"). In that case, the actual keyfile list uses the values of the corresponding Postfix server TLS key file parameters. If a parameter value is empty or equal to none, then no TLSA record is output for that algorithm.
The default keyfile list consists of the two supported algorithms rsa and ecdsa.
The "postfix tls subcommand" feature reads or updates the following configuration parameters.
Use "postconf readme_directory" or "postconf html_directory" to locate this information.
TLS_README, Postfix TLS configuration and operation
The Secure Mailer license must be distributed with this software.