From patchwork Mon Jun 5 16:55:54 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roberto Sassu X-Patchwork-Id: 13267803 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A42A7C7EE23 for ; Mon, 5 Jun 2023 16:56:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234559AbjFEQ45 (ORCPT ); Mon, 5 Jun 2023 12:56:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59776 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233729AbjFEQ44 (ORCPT ); Mon, 5 Jun 2023 12:56:56 -0400 Received: from frasgout13.his.huawei.com (unknown [14.137.139.46]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E7B7F7 for ; Mon, 5 Jun 2023 09:56:54 -0700 (PDT) Received: from mail02.huawei.com (unknown [172.18.147.229]) by frasgout13.his.huawei.com (SkyGuard) with ESMTP id 4QZfdL2n3xz9ypbg for ; Tue, 6 Jun 2023 00:46:30 +0800 (CST) Received: from huaweicloud.com (unknown [10.204.63.22]) by APP1 (Coremail) with SMTP id LxC2BwDXU_+pE35kXiQSAw--.3839S6; Mon, 05 Jun 2023 17:56:36 +0100 (CET) From: Roberto Sassu To: zohar@linux.ibm.com, dmitry.kasatkin@gmail.com Cc: linux-integrity@vger.kernel.org, vt@altlinux.org, pvorel@suse.cz, stefanb@linux.ibm.com, paul@paul-moore.com, casey@schaufler-ca.com, Roberto Sassu Subject: [PATCH v2 ima-evm-utils 4/4] Add simple test to check EVM HMAC calculation Date: Mon, 5 Jun 2023 18:55:54 +0200 Message-Id: <20230605165554.1965238-5-roberto.sassu@huaweicloud.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230605165554.1965238-1-roberto.sassu@huaweicloud.com> References: <20230605165554.1965238-1-roberto.sassu@huaweicloud.com> MIME-Version: 1.0 X-CM-TRANSID: LxC2BwDXU_+pE35kXiQSAw--.3839S6 X-Coremail-Antispam: 1UD129KBjvJXoW3tFyrJr4xAFykCFWrZrWkZwb_yoWkJrWfpw 48WF98Kr4kJFy7t3y3GFsru3WxKayfCry3GFn8twn0yFyDXrWIqryIqr17Gr9IgrWfWr4S yw4Iqr43Ww1DCa7anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvEb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUAV Cq3wA2048vs2IY020Ec7CjxVAFwI0_Xr0E3s1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0 rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVWUJVWUCwA2z4x0Y4vE2Ix0cI8IcVCY1x0267 AKxVW8JVWxJwA2z4x0Y4vEx4A2jsIE14v26r4j6F4UM28EF7xvwVC2z280aVCY1x0267AK xVW8Jr0_Cr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7 xfMcIj6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Y z7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41l42xK82IYc2Ij64vIr41l4I8I3I0E4IkC6x0Yz7 v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF 1VAY17CE14v26r1q6r43MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_Jr0_JF4lIx AIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI 42IY6I8E87Iv67AKxVW8JVWxJwCI42IY6I8E87Iv6xkF7I0E14v26r4j6r4UJbIYCTnIWI evJa73UjIFyTuYvjxUFgAwUUUUU X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAQATBF1jj4467wAAs8 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org From: Roberto Sassu Add a simple test to ensure that the kernel and evmctl provide the same result for the HMAC calculation. Also add another test to evaluate the HMAC on a directory for which Smack added the SMACK64TRANSMUTE xattr. The second test fails without the kernel patch 'smack: Set the SMACK64TRANSMUTE xattr in smack_inode_init_security()', as Smack uses __vfs_setxattr() to set SMACK64TRANSMUTE, which does not go through EVM, and makes the HMAC invalid. Require (unless the UML kernel is used) that the TST_EVM_CHANGE_MODE environment variable is set to 1, so that users acknowledge that they are initializing EVM with a well-known HMAC key, which can introduce obvious security concerns. Signed-off-by: Roberto Sassu --- kernel-configs/base | 4 +- kernel-configs/integrity | 1 + tests/Makefile.am | 2 +- tests/evm_hmac.test | 251 +++++++++++++++++++++++++++++++++++++++ tests/functions.sh | 6 + 5 files changed, 262 insertions(+), 2 deletions(-) create mode 100755 tests/evm_hmac.test diff --git a/kernel-configs/base b/kernel-configs/base index 7acbd5b3b2a..6973e71f7bb 100644 --- a/kernel-configs/base +++ b/kernel-configs/base @@ -46,11 +46,13 @@ CONFIG_TMPFS_XATTR=y CONFIG_CONFIGFS_FS=y CONFIG_KEYS=y CONFIG_ENCRYPTED_KEYS=y +CONFIG_USER_DECRYPTED_DATA=y CONFIG_SECURITY=y CONFIG_SECURITYFS=y CONFIG_SECURITY_NETWORK=y CONFIG_SECURITY_PATH=y -CONFIG_LSM="lockdown,yama,loadpin,safesetid,integrity,bpf" +CONFIG_SECURITY_SMACK=y +CONFIG_LSM="lockdown,yama,loadpin,safesetid,smack,bpf" CONFIG_CRYPTO_AEAD2=y CONFIG_CRYPTO_SKCIPHER=y CONFIG_CRYPTO_SKCIPHER2=y diff --git a/kernel-configs/integrity b/kernel-configs/integrity index a7e01e19466..2e104d205ba 100644 --- a/kernel-configs/integrity +++ b/kernel-configs/integrity @@ -27,3 +27,4 @@ CONFIG_EVM_ATTR_FSUUID=y CONFIG_EVM_ADD_XATTRS=y CONFIG_EVM_LOAD_X509=y CONFIG_EVM_X509_PATH="/etc/keys/x509_evm.der" +CONFIG_EVM_EXTRA_SMACK_XATTRS=y diff --git a/tests/Makefile.am b/tests/Makefile.am index 03aa5b76088..a28f671398f 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -3,7 +3,7 @@ TESTS = $(check_SCRIPTS) check_SCRIPTS += ima_hash.test sign_verify.test boot_aggregate.test \ fsverity.test portable_signatures.test ima_policy_check.test \ - mmap_check.test + mmap_check.test evm_hmac.test check_PROGRAMS := test_mmap diff --git a/tests/evm_hmac.test b/tests/evm_hmac.test new file mode 100755 index 00000000000..e88ff4bf10c --- /dev/null +++ b/tests/evm_hmac.test @@ -0,0 +1,251 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# Copyright (C) 2023 Roberto Sassu +# +# Check if the kernel and evmctl provide the same result for HMAC calculation. + +trap '_report_exit_and_cleanup _cleanup_env cleanup' SIGINT SIGTERM SIGSEGV EXIT + +# Base VERBOSE on the environment variable, if set. +VERBOSE="${VERBOSE:-0}" +TST_EVM_CHANGE_MODE="${TST_EVM_CHANGE_MODE:-0}" +IMA_UUID="28b23254-9467-44c0-b6ba-34b12e85a26f" + +PATCHES=( +'KEYS: encrypted: fix key instantiation with user-provided data' +'KEYS: encrypted: Instantiate key with user-provided decrypted data' +'smack: Set the SMACK64TRANSMUTE xattr in smack_inode_init_security()' +) + +# From security/integrity/evm/evm.h in kernel source directory +(( EVM_INIT_HMAC=0x0001 )) + +cd "$(dirname "$0")" || exit 1 +export PATH=$PWD/../src:$PATH +export LD_LIBRARY_PATH=$LD_LIBRARY_PATH +. ./functions.sh +_require evmctl + +cleanup() { + if [ "$g_loop_mounted" = "1" ]; then + popd > /dev/null || exit "$FAIL" + umount "$g_mountpoint" + fi + + if [ -n "$g_dev" ]; then + losetup -d "$g_dev" + fi + + if [ -n "$g_image" ]; then + rm -f "$g_image" + fi + + if [ -n "$g_mountpoint" ]; then + rm -Rf "$g_mountpoint" + fi +} + +get_xattr() { + local format="hex" + + if [ "$1" = "security.selinux" ]; then + format="text" + fi + + getfattr -n "$1" -e "$format" -d "$2" 2> /dev/null | awk -F "=" '$1 == "'"$1"'" {if ("'"$format"'" == "hex") v=substr($2, 3); else { split($2, temp, "\""); v=temp[2] }; print v}' +} + +# Compare HMAC calculated by the kernel with that calculated by evmctl. +compare_xattr() { + local algo=$1 + local path=$2 + local evm_xattr evm_xattr_evmctl true_digest + + evm_xattr="$(get_xattr security.evm "$path")" + true_digest=$("$algo"sum /bin/true | awk '{print $1}') + # evm_xattr has an extra byte at the beginning for the xattr type. + if [ "${#evm_xattr}" != $(( ${#true_digest} + 2 )) ]; then + echo "${RED}Unexpected size of security.evm for $path${NORM}" + return "$FAIL" + fi + + evm_xattr_evmctl="$(evmctl hmac --smack -v -n "$path" --uuid="$IMA_UUID" -a "$algo" --hmackey "$g_hmackey" 2>&1 | awk -F " " '$1 == "hmac:" {print $2}')" + if [ "$evm_xattr" != "02$evm_xattr_evmctl" ]; then + echo "${RED}$path security.evm mismatch between the kernel and evmctl${NORM}" + return "$FAIL" + fi + + return "$OK" +} + +# The purpose of this test is to verify if the kernel and evmctl produce the +# same HMAC. +check_evm_hmac() { + echo "Test: ${FUNCNAME[0]} (evm_hash: $1, evm_value: $g_evm_value, algo: $1, fs: $2)" + + if ! touch test-file; then + echo "${RED}Cannot create test-file${NORM}" + return "$FAIL" + fi + + compare_xattr "$1" test-file + return $? +} + +cleanup_evm_hmac() { + rm -f test-file +} + +# The purpose of this test is to verify that SMACK64TRANSMUTE is successfully +# set on a newly created directory, and that the HMAC on that directory is valid. +check_evm_hmac_transmute() { + echo "Test: ${FUNCNAME[0]} (evm_hash: $1, evm_value: $g_evm_value, algo: $1, fs: $2)" + + if ! grep -q smack < /sys/kernel/security/lsm; then + echo "Smack LSM not active" + return "${SKIP}" + fi + + # Add a Smack rule for transmuting of test-dir/test-dir2 + if ! echo "_ system rwxatl" > /sys/fs/smackfs/load2; then + echo "${RED}Cannot set Smack policy${NORM}" + return "$FAIL" + fi + + # Smack adds security.SMACK64=_. + if ! mkdir test-dir; then + echo "${RED}Cannot create test-dir${NORM}" + return "$FAIL" + fi + + # Change the directory label so that transmuting happens. + if ! setfattr -n security.SMACK64 -v system test-dir; then + echo "${RED}Cannot set security.SMACK64 on test-dir${NORM}" + return "$FAIL" + fi + + # Add the transmute xattr so that transmuting happens. + if ! setfattr -n security.SMACK64TRANSMUTE -v TRUE test-dir; then + echo "${RED}Cannot set security.SMACK64TRANSMUTE on test-dir${NORM}" + return "$FAIL" + fi + + compare_xattr "$1" test-dir + result=$? + + if [ "$result" -ne "$OK" ]; then + return "$result" + fi + + # Smack adds security.SMACK64=system and security.SMACK64TRANSMUTE=TRUE. + if ! mkdir test-dir/test-dir2; then + echo "${RED}Cannot create test-dir/test-dir2${NORM}" + return "$FAIL" + fi + + compare_xattr "$1" test-dir/test-dir2 + return $? +} + +cleanup_evm_hmac_transmute() { + rm -Rf test-dir +} + +_run_env "$TST_KERNEL" "$PWD/$(basename "$0")" "TST_ENV=$TST_ENV TST_KERNEL=$TST_KERNEL PATH=$PATH LD_LIBRARY_PATH=$LD_LIBRARY_PATH VERBOSE=$VERBOSE" + +# Exit from the creator of the new environment. +_exit_env "$TST_KERNEL" + +# Mount filesystems in the new environment. +_init_env + +# Assume that the EVM mode can be changed in a new environment. +if [ -z "$TST_ENV" ] && [ "$TST_EVM_CHANGE_MODE" -eq 0 ]; then + echo "${CYAN}TST_EVM_CHANGE_MODE env variable must be set to 1${NORM}" + exit "$SKIP" +fi + +g_lsm_init_xattr=$(awk '$1 ~ /(smack|selinux)/' < /sys/kernel/security/lsm) +if [ -z "$g_lsm_init_xattr" ]; then + echo "${CYAN}Either SMACK or SELinux must be active in the system${NORM}" + exit "$SKIP" +fi + +g_mountpoint="$(mktemp -d)" +g_image="$(mktemp)" + +if [ -z "$g_mountpoint" ]; then + echo "${RED}Mountpoint directory not created${NORM}" + exit "$FAIL" +fi + +if [ "$(whoami)" != "root" ]; then + echo "${CYAN}This script must be executed as root${NORM}" + exit "$SKIP" +fi + +if ! evmctl -h | grep -q hmackey; then + echo "${CYAN}Missing HMAC support, run: ./configure --enable-debug${NORM}" + exit "$SKIP" +fi + +if [ ! -f /sys/kernel/security/integrity/evm/evm_xattrs ] || + ! grep -q SMACK64TRANSMUTE < /sys/kernel/security/integrity/evm/evm_xattrs; then + echo "${CYAN}Set CONFIG_EVM_ADD_XATTRS=y and CONFIG_EVM_EXTRA_SMACK_XATTRS=y in the kernel configuration${NORM}" + exit "$SKIP" +fi + +if ! dd if=/dev/zero of="$g_image" bs=1M count=10 &> /dev/null; then + echo "${RED}Cannot create test image${NORM}" + exit "$FAIL" +fi + +g_dev="$(losetup -f "$g_image" --show)" +if [ -z "$g_dev" ]; then + echo "${RED}Cannot create loop device${NORM}" + exit "$FAIL" +fi + +if ! mkfs.ext4 -U $IMA_UUID -b 4096 "$g_dev" &> /dev/null; then + echo "${RED}Cannot format $g_dev${NORM}" + exit "$FAIL" +fi + +if ! mount "$g_dev" "$g_mountpoint"; then + echo "${RED}Cannot mount loop device${NORM}" + exit "$FAIL" +fi + +g_loop_mounted=1 +chmod 777 "$g_mountpoint" +pushd "$g_mountpoint" > /dev/null || exit "$FAIL" + +if [ -f /sys/kernel/security/evm ]; then + g_evm_value=$(cat /sys/kernel/security/evm) +fi + +g_hmackey_data="abcdefABCDEF1234567890aaaaaaaaaaabcdefABCDEF1234567890aaaaaaaaaa" + +g_hmackey="$(mktemp)" +echo $g_hmackey_data | xxd -r -p > "$g_hmackey" + +if [ -n "$g_evm_value" ] && [ $((g_evm_value & EVM_INIT_HMAC)) -ne $EVM_INIT_HMAC ]; then + g_evm_id="$(keyctl add encrypted evm-key "new enc32 user:kmk 32 $g_hmackey_data" @u)" + if ! echo "$EVM_INIT_HMAC" | tee /sys/kernel/security/evm &> /dev/null; then + # Retry with sudo -i, to force search in the root user keyring. + if ! echo "$EVM_INIT_HMAC" | sudo -i tee /sys/kernel/security/evm &> /dev/null; then + keyctl unlink "$g_evm_id" + echo "${RED}Failed to initialize EVM${NORM}" + exit "$FAIL" + fi + fi + + g_evm_value=$(cat /sys/kernel/security/evm) +fi + +expect_pass_if '0 1' check_evm_hmac sha1 ext4 +cleanup_evm_hmac + +expect_pass_if '2' check_evm_hmac_transmute sha1 ext4 +cleanup_evm_hmac_transmute diff --git a/tests/functions.sh b/tests/functions.sh index ed06040b394..35e925cc963 100755 --- a/tests/functions.sh +++ b/tests/functions.sh @@ -434,6 +434,9 @@ _init_env() { mount -t proc proc /proc mount -t sysfs sysfs /sys mount -t securityfs securityfs /sys/kernel/security + if grep -q smack < /sys/kernel/security/lsm; then + mount -t smackfs smackfs /sys/fs/smackfs + fi if [ -n "$(command -v haveged 2> /dev/null)" ]; then $(command -v haveged) -w 1024 &> /dev/null @@ -455,6 +458,9 @@ _cleanup_env() { $1 + if grep -q smack < /sys/kernel/security/lsm; then + umount /sys/fs/smackfs + fi umount /sys/kernel/security umount /sys umount /proc