/lib/udev/rules.d/40-dahdi.rules is in dahdi 1:2.7.0-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | # DAHDI devices with ownership/permissions for running as non-root
SUBSYSTEM=="dahdi", OWNER="asterisk", GROUP="asterisk", MODE="0660"
SUBSYSTEM=="dahdi_devices", RUN="/usr/share/dahdi/handle_device"
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