Apple: Use POSIX IPC instead of System V in sandboxed applications

System V semaphores are not supported in sandboxed applications,
so when Qt is configured with App Store compliance, or the user
requests POSIX IPC explicitly, we use that instead.

https://developer.apple.com/library/archive/documentation/Security/Conceptual/AppSandboxDesignGuide/AppSandboxInDepth/AppSandboxInDepth.html#//apple_ref/doc/uid/TP40011183-CH3-SW24

As the shared memory name limit on Apple platforms is very low,
we have to skip the existing logic for naming, and instead use
a truncated hash of the key. This should still be fine for
avoiding any collisions in practice.

An explicit check for the ENAMETOOLONG error has been added to
catch any cases where they key goes beyond the allowed length.

Sandboxed applications also have an extra requirement that the
key must include an application group identifier. This requirement
has been pushed up to the user and documented, as we don't have
enough information in Qt to know which identifier to use.

Both tst_QSystemSemaphore and tst_QSharedMemory work as before
with both sandboxed and non-sandboxed applications, after removing
some assumptions in tst_QSharedMemory about System V behavior.

Fixes: QTBUG-91130
Change-Id: Iaf1edb36a5d84d69e42ec31471a48d112faa8c6a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 0 insertions, 2 deletions

diff --git a/src/corelib/kernel/qsharedmemory_posix.cpp b/src/corelib/kernel/qsharedmemory_posix.cpp
index d83ff4cb92..9406e200be 100644
--- a/src/corelib/kernel/qsharedmemory_posix.cpp
+++ b/src/corelib/kernel/qsharedmemory_posix.cpp
@@ -102,7 +102,6 @@ bool QSharedMemoryPrivate::create(qsizetype size)
         const int errorNumber = errno;
         const QLatin1String function("QSharedMemory::attach (shm_open)");
         switch (errorNumber) {
-        case ENAMETOOLONG:
         case EINVAL:
             errorString = QSharedMemory::tr("%1: bad name").arg(function);
             error = QSharedMemory::KeyError;
@@ -146,7 +145,6 @@ bool QSharedMemoryPrivate::attach(QSharedMemory::AccessMode mode)
         const int errorNumber = errno;
         const QLatin1String function("QSharedMemory::attach (shm_open)");
         switch (errorNumber) {
-        case ENAMETOOLONG:
         case EINVAL:
             errorString = QSharedMemory::tr("%1: bad name").arg(function);
             error = QSharedMemory::KeyError;