build: Don't use build-time TMPDIR, TEMP, TMP as socket directory

When the ancestor of this code was introduced in 2003 (commit e45e4382),
it was presumably most common to have these variables either unset, or
set to a value that is system-wide and remains valid in the long term,
such as /tmp or /var/tmp.

However, on modern systems they are sometimes set to a value that is
itself temporary, for example /var/folders/${some_long_path}/T on macOS,
or user-specific, for example /tmp/user/$(id -u) on Linux with
libpam-tmpdir. These values are certainly not useful to hard-code into
libdbus and dbus-daemon during installation: they will not be usable
when running dbus-related programs after a reboot or as a different user.

So, instead of assuming TMPDIR, TEMP and TMP remain valid long-term,
we now hard-code /tmp as our default.

As before, system integrators can override this default with
`-Dsession_socket_dir=...` (Meson) or `-DDBUS_SESSION_SOCKET_DIR=...`
(CMake) if a different directory is more appropriate than /tmp.
However, system integrators should note that because AF_UNIX paths have
a relatively short length limit (typically 108 bytes), a short path is
better than a long path in this context.

Resolves: dbus/dbus#551
Signed-off-by: Simon McVittie <smcv@collabora.com>

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 49ae125b3f3c70bb2b6d517bc17c561cef40ad16..82c1493a237f3c23042e7fc0f8e82dec03cdd7a4 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -562,23 +562,9 @@ if(MSVC_IDE)
     file(REMOVE ${PROJECT_BINARY_DIR}/data/dbus-1/services)
 endif()
 
-#### Find socket directories
-set(DBUS_SESSION_SOCKET_DIR "" CACHE STRING "Default directory for session socket")
-if(UNIX)
-    if (CMAKE_CROSSCOMPILING)
-        if (NOT DBUS_SESSION_SOCKET_DIR)
-            message(FATAL_ERROR "cannot autodetect session socket directory "
-                    "when crosscompiling, pass -DDBUS_SESSION_SOCKET_DIR=...")
-        endif()
-    elseif(NOT $ENV{TMPDIR} STREQUAL "")
-        set(DBUS_SESSION_SOCKET_DIR $ENV{TMPDIR})
-    elseif(NOT $ENV{TEMP} STREQUAL "")
-        set(DBUS_SESSION_SOCKET_DIR $ENV{TEMP})
-    elseif(NOT $ENV{TMP} STREQUAL "")
-        set(DBUS_SESSION_SOCKET_DIR $ENV{TMP})
-    else()
-        set(DBUS_SESSION_SOCKET_DIR /tmp)
-    endif()
+set(DBUS_SESSION_SOCKET_DIR "" CACHE STRING "Default directory for session socket on Unix")
+if(UNIX AND NOT DBUS_SESSION_SOCKET_DIR)
+    set(DBUS_SESSION_SOCKET_DIR /tmp)
 endif()
 
  # Not used on Windows, where there is no system bus

diff --git a/meson.build b/meson.build
index 65bb9d0d8e594d13c2dfee9adb4b3242224c8478..451da911446e492db69353ddf0c64b48d60ea8d6 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -1070,19 +1070,11 @@ endif
 data_config.set('SYSCONFDIR_FROM_PKGDATADIR', sysconfdir_from_pkgdatadir)
 data_config.set('DATADIR_FROM_PKGSYSCONFDIR', datadir_from_pkgsysconfdir)
 
-#### Find socket directories
-values = run_command(python, '-c',
-    'import os; [print(os.getenv(e, "")) for e in ["TMPDIR", "TEMP", "TMP"]]',
-    check: true,
-).stdout()
-values += '/tmp'
-default_socket_dir = values.strip().split('\n')[0]
-
 if platform_unix
     session_socket_dir = get_option('session_socket_dir')
 
     if session_socket_dir == ''
-        session_socket_dir = default_socket_dir
+        session_socket_dir = '/tmp'
     endif
 
     config.set_quoted('DBUS_SESSION_SOCKET_DIR', session_socket_dir)