Re: [PATCH] libselinux: android: fix lax service context lookup

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On Wed, Sep 28, 2016 at 12:17 PM, Stephen Smalley <sds@xxxxxxxxxxxxx> wrote:
> On 09/28/2016 12:04 PM, Janis Danisevskis wrote:
>> We use the same lookup function for service contexts
>> that we use for property contexts. However, property
>> contexts are namespace based and only compare the
>> prefix. This may lead to service associations with
>> a wrong label.
>>
>> This patch introduces a stricter lookup function for
>> services contexts. Now the service name must match
>> the key of the service label exactly.
>>
>> Signed-off-by: Janis Danisevskis <jdanis@xxxxxxxxxxx>
>> ---
>>  libselinux/include/selinux/label.h      |  2 ++
>>  libselinux/src/label.c                  |  1 +
>>  libselinux/src/label_android_property.c | 50 +++++++++++++++++++++++++++++++++
>>  libselinux/src/label_internal.h         |  3 ++
>>  4 files changed, 56 insertions(+)
>
> Normally each backend would go into its own file, so service would get
> its own.  Alternatively, since we are unlikely to ever support one
> without the other, perhaps label_android_property.c should be renamed to
> label_android.c and contain all of the Android-unique backends.
>
>>
>> diff --git a/libselinux/include/selinux/label.h b/libselinux/include/selinux/label.h
>> index f0b1e10..277287e 100644
>> --- a/libselinux/include/selinux/label.h
>> +++ b/libselinux/include/selinux/label.h
>> @@ -34,6 +34,8 @@ struct selabel_handle;
>>  #define SELABEL_CTX_DB               3
>>  /* Android property service contexts */
>>  #define SELABEL_CTX_ANDROID_PROP 4
>> +/* Android service contexts */
>> +#define SELABEL_CTX_ANDROID_SERVICE 5
>>
>>  /*
>>   * Available options
>> diff --git a/libselinux/src/label.c b/libselinux/src/label.c
>> index 96a4ff1..eb0e766 100644
>> --- a/libselinux/src/label.c
>> +++ b/libselinux/src/label.c
>> @@ -45,6 +45,7 @@ static selabel_initfunc initfuncs[] = {
>>       CONFIG_X_BACKEND(selabel_x_init),
>>       CONFIG_DB_BACKEND(selabel_db_init),
>>       &selabel_property_init,
>> +     &selabel_service_init,
>
> Wondering if we should support selective enablement of the property and
> service backends too, similar to what William introduced for media, x,
> and db so that he could disable them on Android (in our case, so we can
> disable property and service backends on Linux distributions).

I was wondering that too, im for it. If ANDROID_HOST patch is applied, we
should just set the defaults to strip them out and only on ANDROID_HOST=y
add them in.

We'd also need to coordinate with the AOSP patches, but I can
routinely update those
based on whats going on.

>
>>  };
>>
>>  static void selabel_subs_fini(struct selabel_sub *ptr)
>> diff --git a/libselinux/src/label_android_property.c b/libselinux/src/label_android_property.c
>> index 290b438..69d6afd 100644
>> --- a/libselinux/src/label_android_property.c
>> +++ b/libselinux/src/label_android_property.c
>> @@ -279,6 +279,38 @@ finish:
>>       return ret;
>>  }
>>
>> +static struct selabel_lookup_rec *service_lookup(struct selabel_handle *rec,
>> +             const char *key, int __attribute__((unused)) type)
>> +{
>> +     struct saved_data *data = (struct saved_data *)rec->data;
>> +     spec_t *spec_arr = data->spec_arr;
>> +     unsigned int i;
>> +     struct selabel_lookup_rec *ret = NULL;
>> +
>> +     if (!data->nspec) {
>> +             errno = ENOENT;
>> +             goto finish;
>> +     }
>> +
>> +     for (i = 0; i < data->nspec; i++) {
>> +             if (strcmp(spec_arr[i].property_key, key) == 0)
>> +                     break;
>> +             if (strcmp(spec_arr[i].property_key, "*") == 0)
>> +                     break;
>> +     }
>> +
>> +     if (i >= data->nspec) {
>> +             /* No matching specification. */
>> +             errno = ENOENT;
>> +             goto finish;
>> +     }
>> +
>> +     ret = &spec_arr[i].lr;
>> +
>> +finish:
>> +     return ret;
>> +}
>> +
>>  static void stats(struct selabel_handle __attribute__((unused)) *rec)
>>  {
>>       selinux_log(SELINUX_WARNING, "'stats' functionality not implemented.\n");
>> @@ -302,3 +334,21 @@ int selabel_property_init(struct selabel_handle *rec,
>>
>>       return init(rec, opts, nopts);
>>  }
>> +
>> +int selabel_service_init(struct selabel_handle *rec,
>> +             const struct selinux_opt *opts, unsigned nopts)
>> +{
>> +     struct saved_data *data;
>> +
>> +     data = (struct saved_data *)malloc(sizeof(*data));
>> +     if (!data)
>> +             return -1;
>> +     memset(data, 0, sizeof(*data));
>> +
>> +     rec->data = data;
>> +     rec->func_close = &closef;
>> +     rec->func_stats = &stats;
>> +     rec->func_lookup = &service_lookup;
>> +
>> +     return init(rec, opts, nopts);
>> +}
>> diff --git a/libselinux/src/label_internal.h b/libselinux/src/label_internal.h
>> index 7c55531..6a9481a 100644
>> --- a/libselinux/src/label_internal.h
>> +++ b/libselinux/src/label_internal.h
>> @@ -39,6 +39,9 @@ int selabel_db_init(struct selabel_handle *rec,
>>  int selabel_property_init(struct selabel_handle *rec,
>>                           const struct selinux_opt *opts,
>>                           unsigned nopts) hidden;
>> +int selabel_service_init(struct selabel_handle *rec,
>> +                         const struct selinux_opt *opts,
>> +                         unsigned nopts) hidden;
>>
>>  /*
>>   * Labeling internal structures
>>
>
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-- 
Respectfully,

William C Roberts
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