Implement secpolicy_vnode_setid_retain()

Don't unconditionally return 0 (i.e. retain SUID/SGID).
Test CAP_FSETID capability.

https://github.com/pjd/pjdfstest/blob/master/tests/chmod/12.t
which expects SUID/SGID to be dropped on write(2) by non-owner fails
without this. Most filesystems make this decision within VFS by using
a generic file write for fops.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tomohiro Kusumi <[email protected]>
Closes openzfs#9035
Closes openzfs#9043

configure.ac

@@ -328,6 +328,7 @@ AC_CONFIG_FILES([
 	tests/zfs-tests/tests/functional/snapshot/Makefile
 	tests/zfs-tests/tests/functional/snapused/Makefile
 	tests/zfs-tests/tests/functional/sparse/Makefile
+	tests/zfs-tests/tests/functional/suid/Makefile
 	tests/zfs-tests/tests/functional/alloc_class/Makefile
 	tests/zfs-tests/tests/functional/threadsappend/Makefile
 	tests/zfs-tests/tests/functional/tmpfile/Makefile

module/zfs/policy.c

@@ -209,7 +209,7 @@ secpolicy_vnode_setdac(const cred_t *cr, uid_t owner)
 int
 secpolicy_vnode_setid_retain(const cred_t *cr, boolean_t issuidroot)
 {
-	return (0);
+	return (priv_policy_user(cr, CAP_FSETID, B_FALSE, EPERM));
 }
 
 /*

tests/runfiles/linux.run

@@ -847,6 +847,11 @@ tags = ['functional', 'snapused']
 tests = ['sparse_001_pos']
 tags = ['functional', 'sparse']
 
+[tests/functional/suid]
+tests = ['suid_write_to_suid', 'suid_write_to_sgid', 'suid_write_to_suid_sgid',
+    'suid_write_to_none']
+tags = ['functional', 'suid']
+
 [tests/functional/threadsappend]
 tests = ['threadsappend_001_pos']
 tags = ['functional', 'threadsappend']

tests/zfs-tests/tests/functional/Makefile.am

@@ -66,6 +66,7 @@ SUBDIRS = \
 	snapshot \
 	snapused \
 	sparse \
+	suid \
 	threadsappend \
 	tmpfile \
 	trim \

tests/zfs-tests/tests/functional/suid/.gitignore

@@ -0,0 +1 @@
+/suid_write_to_file

tests/zfs-tests/tests/functional/suid/Makefile.am

@@ -0,0 +1,16 @@
+include $(top_srcdir)/config/Rules.am
+
+pkgdatadir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/suid
+
+dist_pkgdata_SCRIPTS = \
+	suid_write_to_suid.ksh \
+	suid_write_to_sgid.ksh \
+	suid_write_to_suid_sgid.ksh \
+	suid_write_to_none.ksh \
+	cleanup.ksh \
+	setup.ksh
+
+pkgexecdir = $(datadir)/@PACKAGE@/zfs-tests/tests/functional/suid
+
+pkgexec_PROGRAMS = suid_write_to_file
+suid_write_to_file_SOURCES = suid_write_to_file.c

tests/zfs-tests/tests/functional/suid/cleanup.ksh

@@ -0,0 +1,34 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+# Use is subject to license terms.
+#
+
+#
+# Copyright (c) 2019 by Tomohiro Kusumi. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+default_cleanup

tests/zfs-tests/tests/functional/suid/setup.ksh

@@ -0,0 +1,35 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+# Use is subject to license terms.
+#
+
+#
+# Copyright (c) 2019 by Tomohiro Kusumi. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+DISK=${DISKS%% *}
+default_setup $DISK

tests/zfs-tests/tests/functional/suid/suid_write_to_file.c

@@ -0,0 +1,133 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+/*
+ * Copyright (c) 2019 by Tomohiro Kusumi. All rights reserved.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+static void
+test_stat_mode(mode_t extra)
+{
+	struct stat st;
+	int i, fd;
+	char fpath[1024];
+	char *penv[] = {"TESTDIR", "TESTFILE0"};
+	char buf[] = "test";
+	mode_t res;
+	mode_t mode = 0777 | extra;
+
+	/*
+	 * Get the environment variable values.
+	 */
+	for (i = 0; i < sizeof (penv) / sizeof (char *); i++) {
+		if ((penv[i] = getenv(penv[i])) == NULL) {
+			fprintf(stderr, "getenv(penv[%d])\n", i);
+			exit(1);
+		}
+	}
+
+	umask(0);
+	if (stat(penv[0], &st) == -1 && mkdir(penv[0], mode) == -1) {
+		perror("mkdir");
+		exit(2);
+	}
+
+	snprintf(fpath, sizeof (fpath), "%s/%s", penv[0], penv[1]);
+	unlink(fpath);
+	if (stat(fpath, &st) == 0) {
+		fprintf(stderr, "%s exists\n", fpath);
+		exit(3);
+	}
+
+	fd = creat(fpath, mode);
+	if (fd == -1) {
+		perror("creat");
+		exit(4);
+	}
+	close(fd);
+
+	if (setuid(65534) == -1) {
+		perror("setuid");
+		exit(5);
+	}
+
+	fd = open(fpath, O_RDWR);
+	if (fd == -1) {
+		perror("open");
+		exit(6);
+	}
+
+	if (write(fd, buf, sizeof (buf)) == -1) {
+		perror("write");
+		exit(7);
+	}
+	close(fd);
+
+	if (stat(fpath, &st) == -1) {
+		perror("stat");
+		exit(8);
+	}
+	unlink(fpath);
+
+	/* Verify SUID/SGID are dropped */
+	res = st.st_mode & (0777 | S_ISUID | S_ISGID);
+	if (res != (mode & 0777)) {
+		fprintf(stderr, "stat(2) %o\n", res);
+		exit(9);
+	}
+}
+
+int
+main(int argc, char *argv[])
+{
+	const char *name;
+	mode_t extra;
+
+	if (argc < 2) {
+		fprintf(stderr, "Invalid argc\n");
+		exit(1);
+	}
+
+	name = argv[1];
+	if (strcmp(name, "SUID") == 0) {
+		extra = S_ISUID;
+	} else if (strcmp(name, "SGID") == 0) {
+		extra = S_ISGID;
+	} else if (strcmp(name, "SUID_SGID") == 0) {
+		extra = S_ISUID | S_ISGID;
+	} else if (strcmp(name, "NONE") == 0) {
+		extra = 0;
+	} else {
+		fprintf(stderr, "Invalid name %s\n", name);
+		exit(1);
+	}
+
+	test_stat_mode(extra);
+
+	return (0);
+}

tests/zfs-tests/tests/functional/suid/suid_write_to_none.ksh

@@ -0,0 +1,52 @@
+#! /bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2019 by Tomohiro Kusumi. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+# Verify write(2) to regular file by non-owner.
+# Also see https://github.com/pjd/pjdfstest/blob/master/tests/chmod/12.t
+#
+# STRATEGY:
+# 1. creat(2) a file.
+# 2. write(2) to the file with uid=65534.
+# 3. stat(2) the file and verify .st_mode value.
+#
+
+verify_runnable "both"
+
+function cleanup
+{
+	rm -f $TESTDIR/$TESTFILE0
+}
+
+log_onexit cleanup
+log_note "Verify write(2) to regular file by non-owner"
+
+log_must $STF_SUITE/tests/functional/suid/suid_write_to_file "NONE"
+
+log_pass "Verify write(2) to regular file by non-owner passed"

tests/zfs-tests/tests/functional/suid/suid_write_to_sgid.ksh

@@ -0,0 +1,52 @@
+#! /bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2019 by Tomohiro Kusumi. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+# Verify write(2) to SGID file by non-owner.
+# Also see https://github.com/pjd/pjdfstest/blob/master/tests/chmod/12.t
+#
+# STRATEGY:
+# 1. creat(2) a file with SGID.
+# 2. write(2) to the file with uid=65534.
+# 3. stat(2) the file and verify .st_mode value.
+#
+
+verify_runnable "both"
+
+function cleanup
+{
+	rm -f $TESTDIR/$TESTFILE0
+}
+
+log_onexit cleanup
+log_note "Verify write(2) to SGID file by non-owner"
+
+log_must $STF_SUITE/tests/functional/suid/suid_write_to_file "SGID"
+
+log_pass "Verify write(2) to SGID file by non-owner passed"