Secure Unix-domain sockets of "make check" temporary clusters.

Any OS user able to access the socket can connect as the bootstrap
superuser and proceed to execute arbitrary code as the OS user running
the test.  Protect against that by placing the socket in a temporary,
mode-0700 subdirectory of /tmp.  The pg_regress-based test suites and
the pg_upgrade test suite were vulnerable; the $(prove_check)-based test
suites were already secure.  Back-patch to 8.4 (all supported versions).
The hazard remains wherever the temporary cluster accepts TCP
connections, notably on Windows.

As a convenient side effect, this lets testing proceed smoothly in
builds that override DEFAULT_PGSOCKET_DIR.  Popular non-default values
like /var/run/postgresql are often unwritable to the build user.

Security: CVE-2014-0067

Author: nmisch

contrib/pg_upgrade/test.sh

@@ -17,15 +17,43 @@ set -e
 unset MAKEFLAGS
 unset MAKELEVEL
 
-# Set listen_addresses desirably
+# Establish how the server will listen for connections
 testhost=`uname -s`
 
 case $testhost in
-	MINGW*)	LISTEN_ADDRESSES="localhost" ;;
-	*)		LISTEN_ADDRESSES="" ;;
+	MINGW*)
+		LISTEN_ADDRESSES="localhost"
+		PGHOST=""; unset PGHOST
+		;;
+	*)
+		LISTEN_ADDRESSES=""
+		# Select a socket directory.  The algorithm is from the "configure"
+		# script; the outcome mimics pg_regress.c:make_temp_sockdir().
+		PGHOST=$PG_REGRESS_SOCK_DIR
+		if [ "x$PGHOST" = x ]; then
+			{
+				dir=`(umask 077 &&
+					  mktemp -d /tmp/pg_upgrade_check-XXXXXX) 2>/dev/null` &&
+				[ -d "$dir" ]
+			} ||
+			{
+				dir=/tmp/pg_upgrade_check-$$-$RANDOM
+				(umask 077 && mkdir "$dir")
+			} ||
+			{
+				echo "could not create socket temporary directory in \"/tmp\""
+				exit 1
+			}
+
+			PGHOST=$dir
+			trap 'rm -rf "$PGHOST"' 0
+			trap 'exit 3' 1 2 13 15
+		fi
+		export PGHOST
+		;;
 esac
 
-POSTMASTER_OPTS="-F -c listen_addresses=$LISTEN_ADDRESSES"
+POSTMASTER_OPTS="-F -c listen_addresses=$LISTEN_ADDRESSES -k \"$PGHOST\""
 
 temp_root=$PWD/tmp_check
 
@@ -86,7 +114,6 @@ PGSERVICE="";         unset PGSERVICE
 PGSSLMODE="";         unset PGSSLMODE
 PGREQUIRESSL="";      unset PGREQUIRESSL
 PGCONNECT_TIMEOUT=""; unset PGCONNECT_TIMEOUT
-PGHOST="";            unset PGHOST
 PGHOSTADDR="";        unset PGHOSTADDR
 
 # Select a non-conflicting port number, similarly to pg_regress.c

doc/src/sgml/regress.sgml

@@ -58,21 +58,14 @@ make check
 
   <warning>
    <para>
-    This test method starts a temporary server, which is configured to accept
-    any connection originating on the local machine.  Any local user can gain
-    database superuser privileges when connecting to this server, and could
-    in principle exploit all privileges of the operating-system user running
-    the tests.  Therefore, it is not recommended that you use <literal>make
-    check</> on machines shared with untrusted users.  Instead, run the tests
-    after completing the installation, as described in the next section.
-   </para>
-
-   <para>
-    On Unix-like machines, this danger can be avoided if the temporary
-    server's socket file is made inaccessible to other users, for example
-    by running the tests in a protected chroot.  On Windows, the temporary
-    server opens a locally-accessible TCP socket, so filesystem protections
-    cannot help.
+    On systems lacking Unix-domain sockets, notably Windows, this test method
+    starts a temporary server configured to accept any connection originating
+    on the local machine.  Any local user can gain database superuser
+    privileges when connecting to this server, and could in principle exploit
+    all privileges of the operating-system user running the tests.  Therefore,
+    it is not recommended that you use <literal>make check</> on an affected
+    system shared with untrusted users.  Instead, run the tests after
+    completing the installation, as described in the next section.
    </para>
   </warning>
 

src/test/regress/pg_regress.c

@@ -30,6 +30,7 @@
 #endif
 
 #include "getopt_long.h"
+#include "libpq/pqcomm.h"		/* needed for UNIXSOCK_PATH() */
 #include "pg_config_paths.h"
 
 /* for resultmap we need a list of pairs of strings */
@@ -109,6 +110,12 @@ static const char *progname;
 static char *logfilename;
 static FILE *logfile;
 static char *difffilename;
+static const char *sockdir;
+#ifdef HAVE_UNIX_SOCKETS
+static const char *temp_sockdir;
+static char sockself[MAXPGPATH];
+static char socklock[MAXPGPATH];
+#endif
 
 static _resultmap *resultmap = NULL;
 
@@ -307,6 +314,82 @@ stop_postmaster(void)
 	}
 }
 
+#ifdef HAVE_UNIX_SOCKETS
+/*
+ * Remove the socket temporary directory.  pg_regress never waits for a
+ * postmaster exit, so it is indeterminate whether the postmaster has yet to
+ * unlink the socket and lock file.  Unlink them here so we can proceed to
+ * remove the directory.  Ignore errors; leaking a temporary directory is
+ * unimportant.  This can run from a signal handler.  The code is not
+ * acceptable in a Windows signal handler (see initdb.c:trapsig()), but
+ * Windows is not a HAVE_UNIX_SOCKETS platform.
+ */
+static void
+remove_temp(void)
+{
+	Assert(temp_sockdir);
+	unlink(sockself);
+	unlink(socklock);
+	rmdir(temp_sockdir);
+}
+
+/*
+ * Signal handler that calls remove_temp() and reraises the signal.
+ */
+static void
+signal_remove_temp(int signum)
+{
+	remove_temp();
+
+	pqsignal(signum, SIG_DFL);
+	raise(signum);
+}
+
+/*
+ * Create a temporary directory suitable for the server's Unix-domain socket.
+ * The directory will have mode 0700 or stricter, so no other OS user can open
+ * our socket to exploit our use of trust authentication.  Most systems
+ * constrain the length of socket paths well below _POSIX_PATH_MAX, so we
+ * place the directory under /tmp rather than relative to the possibly-deep
+ * current working directory.
+ *
+ * Compared to using the compiled-in DEFAULT_PGSOCKET_DIR, this also permits
+ * testing to work in builds that relocate it to a directory not writable to
+ * the build/test user.
+ */
+static const char *
+make_temp_sockdir(void)
+{
+	char	   *template = strdup("/tmp/pg_regress-XXXXXX");
+
+	temp_sockdir = mkdtemp(template);
+	if (temp_sockdir == NULL)
+	{
+		fprintf(stderr, _("%s: could not create directory \"%s\": %s\n"),
+				progname, template, strerror(errno));
+		exit(2);
+	}
+
+	/* Stage file names for remove_temp().  Unsafe in a signal handler. */
+	UNIXSOCK_PATH(sockself, port, temp_sockdir);
+	snprintf(socklock, sizeof(socklock), "%s.lock", sockself);
+
+	/* Remove the directory during clean exit. */
+	atexit(remove_temp);
+
+	/*
+	 * Remove the directory before dying to the usual signals.  Omit SIGQUIT,
+	 * preserving it as a quick, untidy exit.
+	 */
+	pqsignal(SIGHUP, signal_remove_temp);
+	pqsignal(SIGINT, signal_remove_temp);
+	pqsignal(SIGPIPE, signal_remove_temp);
+	pqsignal(SIGTERM, signal_remove_temp);
+
+	return temp_sockdir;
+}
+#endif   /* HAVE_UNIX_SOCKETS */
+
 /*
  * Check whether string matches pattern
  *
@@ -759,8 +842,7 @@ initialize_environment(void)
 		 * the wrong postmaster, or otherwise behave in nondefault ways. (Note
 		 * we also use psql's -X switch consistently, so that ~/.psqlrc files
 		 * won't mess things up.)  Also, set PGPORT to the temp port, and set
-		 * or unset PGHOST depending on whether we are using TCP or Unix
-		 * sockets.
+		 * PGHOST depending on whether we are using TCP or Unix sockets.
 		 */
 		unsetenv("PGDATABASE");
 		unsetenv("PGUSER");
@@ -769,10 +851,20 @@ initialize_environment(void)
 		unsetenv("PGREQUIRESSL");
 		unsetenv("PGCONNECT_TIMEOUT");
 		unsetenv("PGDATA");
+#ifdef HAVE_UNIX_SOCKETS
 		if (hostname != NULL)
 			doputenv("PGHOST", hostname);
 		else
-			unsetenv("PGHOST");
+		{
+			sockdir = getenv("PG_REGRESS_SOCK_DIR");
+			if (!sockdir)
+				sockdir = make_temp_sockdir();
+			doputenv("PGHOST", sockdir);
+		}
+#else
+		Assert(hostname != NULL);
+		doputenv("PGHOST", hostname);
+#endif
 		unsetenv("PGHOSTADDR");
 		if (port != -1)
 		{
@@ -2067,7 +2159,9 @@ regression_main(int argc, char *argv[], init_function ifunc, test_function tfunc
 		/*
 		 * To reduce chances of interference with parallel installations, use
 		 * a port number starting in the private range (49152-65535)
-		 * calculated from the version number.
+		 * calculated from the version number.  This aids !HAVE_UNIX_SOCKETS
+		 * systems; elsewhere, the use of a private socket directory already
+		 * prevents interference.
 		 */
 		port = 0xC000 | (PG_VERSION_NUM & 0x3FFF);
 
@@ -2240,10 +2334,11 @@ regression_main(int argc, char *argv[], init_function ifunc, test_function tfunc
 		 */
 		header(_("starting postmaster"));
 		snprintf(buf, sizeof(buf),
-				 "\"%s/postgres\" -D \"%s/data\" -F%s -c \"listen_addresses=%s\" > \"%s/log/postmaster.log\" 2>&1",
-				 bindir, temp_install,
-				 debug ? " -d 5" : "",
-				 hostname ? hostname : "",
+				 "\"%s/postgres\" -D \"%s/data\" -F%s "
+				 "-c \"listen_addresses=%s\" -k \"%s\" "
+				 "> \"%s/log/postmaster.log\" 2>&1",
+				 bindir, temp_install, debug ? " -d 5" : "",
+				 hostname ? hostname : "", sockdir ? sockdir : "",
 				 outputdir);
 		postmaster_pid = spawn_process(buf);
 		if (postmaster_pid == INVALID_PID)