The client.conf file configures the CUPS client and is normally located in the /etc/cups and/or ~/.cups directories.
Each line in the file can be a configuration directive, a blank line, or a comment. Comment lines start with the # character.
Note: Starting with macOS 10.7, this file is only used by command-line and X11 applications plus the IPP backend.
The ServerName directive is not supported on macOS at all.
Starting with macOS 10.12, all applications can access these settings in the /Library/Preferences/org.cups.PrintingPrefs.plist file instead.
See the NOTES section below for more information.
Sets encryption options (only in /etc/cups/client.conf).
By default, CUPS only supports encryption using TLS v1.0 or higher using known secure cipher suites.
Security is reduced when Allow options are used.
Security is enhanced when Deny options are used.
The AllowDH option enables cipher suites using plain Diffie-Hellman key negotiation (not supported on systems using GNU TLS).
The AllowRC4 option enables the 128-bit RC4 cipher suites, which are required for some older clients.
The AllowSSL3 option enables SSL v3.0, which is required for some older clients that do not support TLS v1.0.
The DenyCBC option disables all CBC cipher suites.
The DenyTLS1.0 option disables TLS v1.0 support - this sets the minimum protocol version to TLS v1.1.
The MinTLS options set the minimum TLS version to support.
The MaxTLS options set the maximum TLS version to support.
Not all operating systems support TLS 1.3 at this time.
Specifies whether to trust new TLS certificates by default.
The default is "Yes".
Specifies the default user name to use for requests.
Specifies whether to only allow TLS with certificates whose common name matches the hostname.
The default is "No".