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lmdb: patch semaphore names to use shared group container prefix

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mdb_env_setup_locks: using semnames
  'group.com.damus/MDBrwDDi_FHxD' (29),
  'group.com.damus/MDBwwDDi_FHxD' (29)

From old Apple docs:

> IPC and POSIX Semaphores and Shared Memory
>
> Normally, sandboxed apps cannot use Mach IPC, POSIX semaphores and
> shared memory, or UNIX domain sockets (usefully). However, by specifying
> an entitlement that requests membership in an application group, an app
> can use these technologies to communicate with other members of that
> application group.
>
> Note: System V semaphores are not supported in sandboxed apps.
>
> UNIX domain sockets are straightforward; they work just like any other
> file.
>
> Any semaphore or Mach port that you wish to access within a sandboxed
> app must be named according to a special convention:
>
> POSIX semaphores and shared memory names must begin with the application
> group identifier, followed by a slash (/), followed by a name of your
> choosing.
>
> Mach port names must begin with the application group identifier,
> followed by a period (.), followed by a name of your choosing.
>
> For example, if your application group’s name is
> Z123456789.com.example.app-group, you might create two semaphores named
> Z123456789.myappgroup/rdyllwflg and Z123456789.myappgroup/bluwhtflg. You
> might create a Mach port named
> Z123456789.com.example.app-group.Port_of_Kobe.
>
> Note: The maximum length of a POSIX semaphore name is only 31 bytes, so
> if you need to use POSIX semaphores, you should keep your app group
> names short.

Link: https://github.com/damus-io/damus/issues/2323#issuecomment-2323305949
Signed-off-by: William Casarin <jb55@jb55.com>
This commit is contained in:
William Casarin
2024-09-01 06:20:11 -07:00
parent 3a9dda5eb3
commit dcafcd9184
2 changed files with 17 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
nostrdb/mdb.c
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@@ -4893,8 +4893,17 @@ mdb_env_setup_locks(MDB_env *env, MDB_name *fname, int mode, int *excl)
#ifdef MDB_SHORT_SEMNAMES
encbuf[9] = '\0'; /* drop name from 15 chars to 14 chars */
#endif
sprintf(env->me_txns->mti_rmname, "/MDBr%s", encbuf);
sprintf(env->me_txns->mti_wmname, "/MDBw%s", encbuf);
#define DEF_STR(x) #x
#define DEF_TO_STRING(x) DEF_STR(x)
sprintf(env->me_txns->mti_rmname, DEF_TO_STRING(MDB_SEM_NAME_PREFIX) "/MDBr%s", encbuf);
sprintf(env->me_txns->mti_wmname, DEF_TO_STRING(MDB_SEM_NAME_PREFIX) "/MDBw%s", encbuf);
#undef DEF_STR
#undef DEF_TO_STRING
printf("mdb_env_setup_locks: using semnames '%s' (%d), '%s' (%d)\n",
env->me_txns->mti_rmname, strlen(env->me_txns->mti_rmname),
env->me_txns->mti_wmname, strlen(env->me_txns->mti_wmname));
/* Clean up after a previous run, if needed: Try to
* remove both semaphores before doing anything else.
*/