Alsa-Hook-Plugin Object: Provide a Hook on Alsa PCM to check permission again AGL Advance Audio Agent Status: Working Proof of Concept Author: Fulup Ar Foll fulup@iot.bzh Date : August-2017 Functionalities: - Execute a set of websocket RPC request again AGL binders to allow/deny access - Keep websocket open in an idepandant thread on order to monitor event receive from AGL audio agent Installation - Alsaplugins are typically search in /usr/share/alsa-lib. Nevertheless a full path might be given - This plugin implement a hook on a slave PCM. Typically this slave PCM is a dedicated virtual channel (eg: navigation, emergency,...) - Config should be place in ~/.asoundrc (see config sample in PROJECT_ROOT/conf.d/alsa) Config ``` # Define sharelib location and entry point # ----------------------------------------- pcm_hook_type.MyHookPlugin { install "AlsaInstallHook" lib "/home/fulup/Workspace/AGL-AppFW/audio-bindings-dev/build/Alsa-Plugin/Alsa-Hook-Callback/alsa_hook_cb.so" } # Create PCM HOOK with corresponding request calls to AGL Audio Agent # -------------------------------------------------------------------- pcm.MyNavigationHook { type hooks slave.pcm "MyMixerPCM" # Defined used hook sharelib and provide arguments/config to install func hooks.0 { type "MyHookPlugin" hook_args { verbose true # print few log messages (default false); # Every Call should return OK in order PCM to open (default timeout 100ms) uri "ws://localhost:1234/api?token='audio-agent-token'" request { # Request autorisation to write on navigation RequestNavigation { api "control" verb "navigation" } # subscribe to Audio Agent Event SubscriveEvents { api "control" verb "monitor" } # force PCM stop after 10s TestAutoStop { api "control" verb "event_test" query "{'label':'stop', 'delay':10000}" } } } } } ``` NOTE: * Hook plugin is loaded by Alsa libasound within player context. It inherits client process attributes, as UID/GID or the SMACK label on AGL. This smack label is tested by AGL security framework when requested a call on the audio-agent binder. As a result the call will only succeed it the permission attached the application in Cynara matches. * Hook plugin keep a connection with the Audio-Agent until PCM is closed by the application. This connection allow the Audio-Agent to send events. eg: pause, quit, mute, ...