path: root/hook-plugin/PolicyHookUnix.c

/*
 * Copyright (C) 2016 "IoT.bzh"
 * Author Fulup Ar Foll <fulup@iot.bzh>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * AfbCallBack (snd_ctl_hal_t *handle, int numid, void **response);
 *  AlsaHookInit is mandatory and called with numid=0
 *
 * Syntax in .asoundrc file
 *   CrlLabel    { cb MyFunctionName name "My_Second_Control" }
 *
 * Testing:
 *   aplay -DAlsaHook /usr/share/sounds/alsa/test.wav
 *
 * References:
 *  https://www.spinics.net/lists/alsa-devel/msg54235.html
 *  https://github.com/shivdasgujare/utilities/blob/master/nexuss/alsa-scenario-hook/src/alsa-wrapper.c
 */

#define _GNU_SOURCE
#include <stdio.h>
#include <alloca.h>

#include <alsa/asoundlib.h>
#include <alsa/conf.h>
#include <alsa/pcm.h>

#include <systemd/sd-event.h>
#include <json-c/json.h>

#include "afb/afb-wsj1.h"
#include "afb/afb-ws-client.h"
#include "afb/afb-proto-ws.h"

#include <pthread.h>
#include <semaphore.h>


#define PLUGIN_ENTRY_POINT AlsaInstallHook
    // Fulup Note: What ever you may find on Internet you should use
    // SND_CONFIG_DLSYM_VERSION_HOOK and not SND_CONFIG_DLSYM_VERSION_HOOK
    SND_DLSYM_BUILD_VERSION(PLUGIN_ENTRY_POINT, SND_PCM_DLSYM_VERSION)

// this should be more than enough
#define MAX_API_CALL 10
#define MAX_EVT_CALL 10

// timeout in ms
#define REQUEST_DEFAULT_TIMEOUT 500
#ifndef MAINLOOP_WATCHDOG
#define MAINLOOP_WATCHDOG 100000
#endif

// closing message is added to query when PCM is closed
#define CLOSING_MSG ",\"source\":-1}"

// Currently not implemented
#define UNUSED_ARG(x) UNUSED_ ## x __attribute__((__unused__))

typedef struct {
    const char *openVerb;
    const char *closeVerb;
    json_object *queryJ;
    long timeout;

    sd_event_source *evtSource;
    char *callIdTag;
    void *afbClient;
} afbRequestT;

typedef struct {
    const char *name;
    int  signal;
} afbEventT;

typedef struct {
    char *name;
    snd_pcm_t *pcm;
    const char *uri;
    struct afb_proto_ws *pws;
    sd_event *sdLoop;
    int verbose;
    sem_t semaphore;
    int count;
    int error;
    afbRequestT **request;
    afbEventT **event;
} afbClientT;


static void *LoopInThread(void *handle) {
    afbClientT *afbClient = (afbClientT*) handle;
    int count=0;
    int watchdog= MAINLOOP_WATCHDOG *1000;

    /* loop until end */
    for (;;) {

        if (afbClient->verbose) printf("ON-MAINLOOP ping=%d\n", count++);
        sd_event_run(afbClient->sdLoop, watchdog);
    }

    return NULL;
}

// lost connect with the AudioDaemon
static void OnHangupCB(void *handle) {

    afbClientT *afbClient = (afbClientT*) handle;
    SNDERR("(Hoops) Lost Connection to %s", afbClient->uri);

    // try to close PCM when impossible terminate client
    int err = snd_pcm_close (afbClient->pcm);
    if (err) exit(1);
}

typedef enum {
    HOOK_INSTALL,
    HOOK_CLOSE,
} hookActionT;

void OnEventCB(void *handle, const char *event, int evtid, struct json_object *eventJ) {
    afbClientT *afbClient = (afbClientT*) handle;
    afbEventT **afbEvent = afbClient->event;
    json_object *dataJ, *tmpJ;
    const char *label;
    int value, done, index;

    done= json_object_object_get_ex(eventJ,"data", &dataJ);
    if (!done) {
        SNDERR ("PCM_HOOK: uri=%s empty event label", afbClient->uri);
        goto OnErrorExit;
    }

    json_object_object_get_ex(dataJ,"signal", &tmpJ);
    label=json_object_get_string(tmpJ);

    json_object_object_get_ex(dataJ,"value", &tmpJ);
    value=json_object_get_int(tmpJ);

    for (index=0; afbEvent[index]!= NULL; index++) {
        if (!strcmp(afbEvent[index]->name, label)) break;
    }

    if (!afbEvent[index] || !afbEvent[index]->signal) {
        SNDERR ("PCM_HOOK: Unsupported uri=%s label=%s", afbClient->uri, label);
        return;
    }

    // send signal to self process
    kill (getpid(), afbEvent[index]->signal);

    if (afbClient->verbose) printf("ON-EVENT label=%s signal=%d\n", label, value);
    return;

OnErrorExit:
    SNDERR("ON-EVENT %s(%s)\n", event, json_object_get_string(dataJ));
    return;
}

static void OnSuccessCB(void* UNUSED_ARG(ctx) , void* handle, json_object* responseJ, const char* info) {
    
    afbRequestT *afbRequest= (afbRequestT*)handle;
    afbClientT *afbClient=(afbClientT*)afbRequest->afbClient;

    if (afbClient->verbose) printf("OnSuccessCB callid='%s' response='%s' info='%s'\n", afbRequest->callIdTag, json_object_get_string(responseJ), info);

    // Cancel timeout for this request
    sd_event_source_unref(afbRequest->evtSource);
    free(afbRequest->callIdTag);

    // When not more waiting call release semaphore
    afbClient->count--;
    if (afbClient->count == 0) {
        if (afbClient->verbose) printf("OnSuccessCB No More Waiting Request\n");
        afbClient->error=0;
        sem_post (&afbClient->semaphore);
    }
}

static void OnFailureCB(void* UNUSED_ARG(ctx), void* handle, const char *status, const char *info) {
    
    afbRequestT *afbRequest= (afbRequestT*)handle;
    afbClientT *afbClient=(afbClientT*)afbRequest->afbClient;

    if (afbClient->verbose) printf("OnFailureCB callid='%s' status='%s' info='%s'\n", afbRequest->callIdTag, status, info);

    // Cancel timeout for this request
    sd_event_source_unref(afbRequest->evtSource);
    free(afbRequest->callIdTag);

    afbClient->error=1;
    sem_post (&afbClient->semaphore);
}


/* the callback interface for pws */
static struct afb_proto_ws_client_itf itf = {
    .on_reply_success = OnSuccessCB,
    .on_reply_fail = OnFailureCB,
    .on_event_create = NULL,
    .on_event_remove = NULL,
    .on_event_subscribe = NULL,
    .on_event_unsubscribe = NULL,
    .on_event_push = OnEventCB,
    .on_event_broadcast = NULL,
    .on_subcall = NULL,
};

int OnTimeoutCB (sd_event_source* source, uint64_t timer, void* handle) {
    afbClientT *afbClient= (afbClientT*)handle;

    SNDERR("\nON-TIMEOUT Call Request Fail URI=%s\n", afbClient->uri);

    // Close PCM and release waiting client
    afbClient->error=1;
    sem_post (&afbClient->semaphore);

    return 0;
}

// Call AGL binder asynchronously by with a timeout
static int CallWithTimeout(afbClientT *afbClient, afbRequestT *afbRequest, int count, hookActionT action) {
    uint64_t usec;
    const char * apiVerb;
    int err;

    // create a unique tag for request
    (void) asprintf(&afbRequest->callIdTag, "%d:%s", count, afbRequest->openVerb);

    // create a timer with ~250us accuracy
    sd_event_now(afbClient->sdLoop, CLOCK_MONOTONIC, &usec);
    sd_event_add_time(afbClient->sdLoop, &afbRequest->evtSource, CLOCK_MONOTONIC, usec+afbRequest->timeout*1000, 250, OnTimeoutCB, afbClient);


    // on PCM close replace last '}' by CLOSING_MSG
    if (action == HOOK_CLOSE) apiVerb= afbRequest->closeVerb;
    else apiVerb= afbRequest->openVerb;

    // release action is optional
    if (apiVerb) {
        char * sessionId;
        (void) asprintf(&sessionId, "alsa-hook-pid:%d", getpid());
        if (afbClient->verbose) printf("CALL-REQUEST verb=%s tag=%s\n", apiVerb, afbRequest->callIdTag);
        err = afb_proto_ws_client_call(afbClient->pws, apiVerb, afbRequest->queryJ, sessionId, afbRequest);
        if (err < 0 ) goto OnErrorExit;        
    }
    // save client handle in request
    afbRequest->afbClient = afbClient;
    afbClient->count ++;

    return 0;

OnErrorExit:
    fprintf(stderr, "LaunchCallRequest: Fail call %s//%s&%s", afbClient->uri, apiVerb, json_object_get_string(afbRequest->queryJ));
    return 1;
}

static int LaunchCallRequest(afbClientT *afbClient, hookActionT action) {

    pthread_t tid;
    int err, idx;
    afbRequestT **afbRequest= afbClient->request;

    if (action == HOOK_INSTALL) {
        // init waiting counting semaphore
        if (sem_init(&afbClient->semaphore, 1, 0) == -1) {
           fprintf(stderr, "LaunchCallRequest: Fail Semaphore Init: %s\n", afbClient->uri);
        }

        // Create a main loop
        err = sd_event_default(&afbClient->sdLoop);
        if (err < 0) {
            fprintf(stderr, "LaunchCallRequest: Connection to default event loop failed: %s\n", strerror(-err));
            goto OnErrorExit;
        }

        // start a thread with a mainloop to monitor Audio-Agent
        err = pthread_create(&tid, NULL, &LoopInThread, afbClient);
        if (err) goto OnErrorExit;
        
	afbClient->pws = afb_ws_client_connect_api(afbClient->sdLoop, afbClient->uri, &itf, afbClient);
	if (afbClient->pws == NULL) {
            fprintf(stderr, "LaunchCallRequest: Connection to %s failed\n", afbClient->uri);
            goto OnErrorExit;
	}
        
        // register hanghup callback
        afb_proto_ws_on_hangup(afbClient->pws, OnHangupCB);
    }

    // send call request to audio-agent asynchronously (respond with thread mainloop context)
    for (idx = 0; afbRequest[idx] != NULL; idx++) {
        err = CallWithTimeout(afbClient, afbRequest[idx], idx, action);
        if (err) goto OnErrorExit;
    }

    // launch counter to keep track of waiting request call
    afbClient->count=idx;

    return 0;

OnErrorExit:
    return -1;
}

static int AlsaCloseHook(snd_pcm_hook_t *hook) {

    afbClientT *afbClient = (afbClientT*) snd_pcm_hook_get_private (hook);

    // launch call request and create a waiting mainloop thread
    int err = LaunchCallRequest(afbClient, HOOK_CLOSE);
    if (err < 0) {
        fprintf (stderr, "PCM Fail to Enter Mainloop\n");
        goto OnErrorExit;
    }

    // wait for all call request to return
    sem_wait(&afbClient->semaphore);
    if (afbClient->error) {
        fprintf (stderr, "AlsaCloseHook: Notice exit before audio-4a response\n");
        goto OnErrorExit;
    }

    if (afbClient->verbose) fprintf(stdout, "\nAlsaHook Close Success PCM=%s URI=%s\n", snd_pcm_name(afbClient->pcm), afbClient->uri);
    return 0;

OnErrorExit:
    fprintf(stderr, "\nAlsaPcmHook Plugin Close Fail PCM=%s\n", snd_pcm_name(afbClient->pcm));
    return 0;
}

// Function call when Plugin PCM is OPEN
int PLUGIN_ENTRY_POINT (snd_pcm_t *pcm, snd_config_t *conf) {
    snd_pcm_hook_t *h_close = NULL;
    snd_config_iterator_t it, next;
    afbClientT *afbClient = malloc(sizeof (afbClientT));
    afbRequestT **afbRequest = malloc(MAX_API_CALL * sizeof(afbRequestT*));
    afbEventT **afbEvent= malloc(MAX_EVT_CALL * sizeof(afbEventT*));
    int err;

    // start populating client handle
    afbClient->pcm = pcm;
    afbClient->name= strdup(snd_pcm_name(pcm));
    afbClient->verbose = 0;
    afbClient->request = afbRequest;

    // Get PCM arguments from asoundrc
    snd_config_for_each(it, next, conf) {
        snd_config_t *node = snd_config_iterator_entry(it);
        const char *id;

        // ignore comment en empty lines
        if (snd_config_get_id(node, &id) < 0) continue;
        if (strcmp(id, "comment") == 0 || strcmp(id, "hint") == 0) continue;

        if (strcmp(id, "ws-client") == 0) {
            const char *uri;
            if (snd_config_get_string(node, &uri) < 0) {
                SNDERR("Invalid String for %s", id);
                goto OnErrorExit;
            }
            afbClient->uri=strdup(uri);
            continue;
        }

        if (strcmp(id, "verbose") == 0) {
            afbClient->verbose= snd_config_get_bool(node);
            if (afbClient->verbose < 0) {
                SNDERR("Invalid Boolean for %s", id);
                goto OnErrorExit;
            }
            continue;
        }

        if (strcmp(id, "controls") == 0) {
            const char *callConf, *callLabel;
            snd_config_type_t ctype;
            snd_config_iterator_t currentCall, follow;
            snd_config_t *itemConf;
            int callCount=0;

            ctype = snd_config_get_type(node);
            if (ctype != SND_CONFIG_TYPE_COMPOUND) {
                snd_config_get_string(node, &callConf);
                SNDERR("Invalid compound type for %s", callConf);
                goto OnErrorExit;
            }
            
            // loop on each call
            snd_config_for_each(currentCall, follow, node) {
                snd_config_t *ctlconfig = snd_config_iterator_entry(currentCall);

                // ignore empty line
                if (snd_config_get_id(ctlconfig, &callLabel) < 0) continue;

                // each clt should be a valid config compound
                ctype = snd_config_get_type(ctlconfig);
                if (ctype != SND_CONFIG_TYPE_COMPOUND) {
                    snd_config_get_string(node, &callConf);
                    SNDERR("Invalid call element for %s value=%s", callLabel, callConf);
                    goto OnErrorExit;
                }

                // allocate an empty call request
                afbRequest[callCount] = calloc(1, sizeof (afbRequestT));

                err = snd_config_search(ctlconfig, "request", &itemConf);
                if (!err) {
                    const char *verb;
                    if (snd_config_get_string(itemConf, &verb) < 0) {
                        SNDERR("Invalid open verb string %s", id);
                        goto OnErrorExit;
                    }
                    afbRequest[callCount]->openVerb=strdup(verb);
                }

                err = snd_config_search(ctlconfig, "release", &itemConf);
                if (!err) {
                    const char *verb;
                    if (snd_config_get_string(itemConf, &verb) < 0) {
                        SNDERR("Invalid close verb string %s", id);
                        goto OnErrorExit;
                    }
                    afbRequest[callCount]->closeVerb=strdup(verb);
                }

                err = snd_config_search(ctlconfig, "timeout", &itemConf);
                if (!err) {
                    if (snd_config_get_integer(itemConf, &afbRequest[callCount]->timeout) < 0) {
                        SNDERR("Invalid timeout Integer %s", id);
                        goto OnErrorExit;
                    }
                }

                err = snd_config_search(ctlconfig, "args", &itemConf);
                if (!err) {
                    char *query;
                    if (snd_config_get_string(itemConf, (const char**) &query) < 0) {
                        SNDERR("Invalid args string %s", id);
                        goto OnErrorExit;
                    }

                    // cleanup string for json_tokener
                    for (int idx = 0; query[idx] != '\0'; idx++) {
                        if (query[idx] == '\'') query[idx] = '"';
                    }
                    afbRequest[callCount]->queryJ = json_tokener_parse(query);
                    if (!afbRequest[callCount]->queryJ) {
                        SNDERR("Invalid Json %s args=%s should be args=\"{'tok1':'val1', 'tok2':'val2'}\" ", id, query);
                        goto OnErrorExit;
                    }
                }

                // Simple check on call request validity
                if (!afbRequest[callCount]->timeout) afbRequest[callCount]->timeout=REQUEST_DEFAULT_TIMEOUT ;
                if (!afbRequest[callCount]->openVerb || !afbRequest[callCount]->closeVerb) {
                    SNDERR("Missing open(verb)/close(verb) %s in asoundrc", callLabel);
                    goto OnErrorExit;
                }

                // move to next call if any
                callCount ++;
                if (callCount == MAX_API_CALL) {
                    SNDERR("Too Many call MAX_API_CALL=%d", MAX_API_CALL);
                    goto OnErrorExit;
                }
                afbRequest[callCount]=NULL; // afbRequest array is NULL terminated

            }
            continue;
        }
        if (strcmp(id, "events") == 0) {
            const char *callConf, *callLabel;
            snd_config_type_t ctype;
            snd_config_iterator_t currentCall, follow;
            int callCount=0;

            ctype = snd_config_get_type(node);
            if (ctype != SND_CONFIG_TYPE_COMPOUND) {
                snd_config_get_string(node, &callConf);
                SNDERR("Invalid compound type for %s", callConf);
                goto OnErrorExit;
            }


            // loop on each call
            snd_config_for_each(currentCall, follow, node) {
                snd_config_t *ctlconfig = snd_config_iterator_entry(currentCall);
                long sigval;

                // ignore empty line
                if (snd_config_get_id(ctlconfig, &callLabel) < 0) continue;

                // each clt should be a valid config compound
                ctype = snd_config_get_type(ctlconfig);
                if (ctype != SND_CONFIG_TYPE_INTEGER) {
                    snd_config_get_string(ctlconfig, &callConf);
                    SNDERR("Invalid signal number for %s value=%s", callLabel, callConf);
                    goto OnErrorExit;
                }

                // allocate an empty call request
                snd_config_get_integer(ctlconfig, &sigval);
                afbEvent[callCount] = calloc(1, sizeof (afbEventT));
                afbEvent[callCount]->name=strdup(callLabel);
                afbEvent[callCount]->signal= (int)sigval;

                // move to next call if any
                callCount ++;
                if (callCount == MAX_EVT_CALL) {
                    SNDERR("Too Many call MAX_EVT_CALL=%d", MAX_EVT_CALL);
                    goto OnErrorExit;
                }
                afbEvent[callCount]=NULL; // afbEvent array is NULL terminated

            }
            continue;
        }
    }

    if (afbClient->verbose) fprintf(stdout, "\nAlsaHook Install Start PCM=%s URI=%s\n", snd_pcm_name(afbClient->pcm), afbClient->uri);

    err = snd_pcm_hook_add(&h_close, afbClient->pcm, SND_PCM_HOOK_TYPE_CLOSE, AlsaCloseHook, afbClient);
    if (err < 0) goto OnErrorExit;

    // launch call request and create a waiting mainloop thread
    err = LaunchCallRequest(afbClient, HOOK_INSTALL);
    if (err < 0) {
        fprintf (stderr, "PCM Fail to Enter Mainloop\n");
        goto OnErrorExit;
    }

    // wait for all call request to return
    sem_wait(&afbClient->semaphore);
    if (afbClient->error) {
        fprintf (stderr, "PCM Authorisation Deny from AAAA Controller (AGL Advanced Audio Agent)\n");
        goto OnErrorExit;
    }

    if (afbClient->verbose) fprintf(stdout, "\nAlsaHook Install Success PCM=%s URI=%s\n", afbClient->name, afbClient->uri);
    return 0;

OnErrorExit:
    fprintf(stderr, "\nAlsaPcmHook Plugin Policy Control Fail PCM=%s\n", afbClient->name);
    if (h_close)
        snd_pcm_hook_remove(h_close);

    return -EINVAL;
}