From fad7fc57f7d26c9f4c6280d243922930a07a007b Mon Sep 17 00:00:00 2001 From: Eric Sandeen Date: Mon, 18 May 2020 11:14:43 -0500 Subject: [PATCH] fstests: test restricted symlinks & hardlinks sysctls This tests the fs.protected_symlinks and fs.protected_hardlinks sysctls which restrict links behavior in sticky world-writable directories as documented in the kernel at Documentation/admin-guide/sysctl/fs.rst Signed-off-by: Eric Sandeen Reviewed-by: Zorro Lang Signed-off-by: Eryu Guan --- tests/generic/597 | 117 ++++++++++++++++++++++++++++++++++++++++++ tests/generic/597.out | 14 +++++ tests/generic/group | 1 + 3 files changed, 132 insertions(+) create mode 100755 tests/generic/597 create mode 100644 tests/generic/597.out diff --git a/tests/generic/597 b/tests/generic/597 new file mode 100755 index 00000000..1d87a23a --- /dev/null +++ b/tests/generic/597 @@ -0,0 +1,117 @@ +#! /bin/bash +# SPDX-License-Identifier: GPL-2.0 +# Copyright (c) 2020 Red Hat, Inc. All Rights Reserved. +# +# FS QA Test No. 597 +# +# Test protected_symlink and protected_hardlink sysctls +# +seq=`basename $0` +seqres=$RESULT_DIR/$seq +echo "QA output created by $seq" + +here=`pwd` +tmp=/tmp/$$ +status=1 # failure is the default! +trap "_cleanup; exit \$status" 0 1 2 3 15 + +_cleanup() +{ + rm -rf $TEST_DIR/$seq + [ ! -z "$SYMLINK_PROTECTION" ] \ + && sysctl -qw fs.protected_symlinks=$SYMLINK_PROTECTION + [ ! -z "$HARDLINK_PROTECTION" ] \ + && sysctl -qw fs.protected_hardlinks=$HARDLINK_PROTECTION + cd / + rm -f $tmp.* +} + +# get standard environment, filters and checks +. ./common/rc +. ./common/filter + +# remove previous $seqres.full before test +rm -f $seqres.full + +# real QA test starts here + +# Modify as appropriate. +_supported_fs generic +_supported_os Linux +_require_test +_require_sysctl_variable fs.protected_symlinks +_require_sysctl_variable fs.protected_hardlinks +# su in _require_user prints warnings about user name starts with a digit, +# discard the warning +_require_user 123456-fsgqa >/dev/null 2>&1 +# Do this SECOND so that qa_user is fsgqa, and _user_do uses that account +_require_user fsgqa + +OWNER=123456-fsgqa +OTHER=fsgqa + +# Save current system state to reset when done +SYMLINK_PROTECTION=`sysctl -n fs.protected_symlinks` +HARDLINK_PROTECTION=`sysctl -n fs.protected_hardlinks` + +test_symlink() +{ + ln -s $TEST_DIR/$seq/target $TEST_DIR/$seq/sticky_dir/symlink + chown $OTHER.$OTHER $TEST_DIR/$seq/sticky_dir + chown $OWNER.$OWNER $TEST_DIR/$seq/sticky_dir/symlink + # If we can read the target, we followed the link + _user_do "cat $TEST_DIR/$seq/sticky_dir/symlink" | _filter_test_dir + rm -f $TEST_DIR/$seq/sticky_dir/symlink +} + +test_hardlink() +{ + chown $OWNER.$OWNER $TEST_DIR/$seq/target + chmod go-rw $TEST_DIR/$seq/target + _user_do "ln $TEST_DIR/$seq/target $TEST_DIR/$seq/sticky_dir/hardlink" \ + | _filter_test_dir + test -f $TEST_DIR/$seq/sticky_dir/hardlink \ + && echo "successfully created hardlink" + rm -f $TEST_DIR/$seq/sticky_dir/hardlink +} + +setup_tree() +{ + # Create world-writable sticky dir + mkdir -p $TEST_DIR/$seq/sticky_dir + chmod 1777 $TEST_DIR/$seq/sticky_dir + # And a file elsewhere that will be linked to from that sticky dir + mkdir -p $TEST_DIR/$seq + # If we can read it, we followed the link. + echo "successfully followed symlink" > $TEST_DIR/$seq/target +} + +setup_tree + +# First test fs.protected_symlinks +# With protection on, symlink follows should fail if the +# link owner != the sticky directory owner, and the process +# is not the link owner. +echo "== Test symlink follow protection when" +echo "== process != link owner and dir owner != link owner" +sysctl -w fs.protected_symlinks=0 +test_symlink +sysctl -w fs.protected_symlinks=1 +test_symlink + +echo + +# Now test fs.protected_hardlinks +# With protection on, hardlink creation should fail if the +# process does not own the target file, and the process does not have +# read-write access to the target +echo "== Test hardlink create protection when" +echo "== process != target owner and process cannot read target" +sysctl -w fs.protected_hardlinks=0 +test_hardlink +sysctl -w fs.protected_hardlinks=1 +test_hardlink + +# success, all done +status=0 +exit diff --git a/tests/generic/597.out b/tests/generic/597.out new file mode 100644 index 00000000..c654da7d --- /dev/null +++ b/tests/generic/597.out @@ -0,0 +1,14 @@ +QA output created by 597 +== Test symlink follow protection when +== process != link owner and dir owner != link owner +fs.protected_symlinks = 0 +successfully followed symlink +fs.protected_symlinks = 1 +Permission denied + +== Test hardlink create protection when +== process != target owner and process cannot read target +fs.protected_hardlinks = 0 +successfully created hardlink +fs.protected_hardlinks = 1 +ln: failed to create hard link 'TEST_DIR/597/sticky_dir/hardlink' => 'TEST_DIR/597/target': Operation not permitted diff --git a/tests/generic/group b/tests/generic/group index e82004e8..db7d936e 100644 --- a/tests/generic/group +++ b/tests/generic/group @@ -599,3 +599,4 @@ 594 auto quick quota 595 auto quick encrypt 596 auto quick +597 auto quick perms -- 2.39.5