From: Roberto Sassu <roberto.sassu@xxxxxxxxxx> Verify that operations on files with EVM portable signatures succeed and that the new kernel patch set does not break the existing kernel integrity expectations. Build and install mount-idmapped for ci/fedora.sh, to additionally test idmapped mounts. To run the tests, pass the path of the kernel private key with the TST_KEY_PATH environment variable. If not provided, the script searches the key in /lib/modules/$(uname -r)/source/certs/signing_key.pem and in the current directory. Root privileges are required to mount the image, configure IMA/EVM and set xattrs. Set UML_MODE to 1, to relaunch the script in a new environment after booting an UML kernel. The UML kernel must be named 'linux' and placed in the ima-evm-utils directory. Alternatively, set the TST_EVM_CHANGE_MODE variable to 1, to change the current EVM mode, if a test needs a different one. Otherwise, execute only the tests compatible with the current EVM mode. Also set the EVM_ALLOW_METADATA_WRITES flag in the EVM mode, before launching the script, to run the check_evm_revalidate() test. Execute: echo 4 > /sys/kernel/security/evm The last two environment variables above affect which tests will run the next time the script is executed. Without setting UML_MODE to 1, changes to the current EVM mode will be irreversibly done in the host. Next time, unless the host is rebooted, only tests compatible with the last EVM mode set will run. The others will be skipped. With the UML kernel, this problem does not arise as, every time the UML kernel is executed, it will create a clean environment with no flags set in the EVM mode. Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx> --- build.sh | 5 + ci/fedora.sh | 7 +- tests/Makefile.am | 2 +- tests/install-mount-idmapped.sh | 7 + tests/portable_signatures.test | 1173 +++++++++++++++++++++++++++++++ 5 files changed, 1192 insertions(+), 2 deletions(-) create mode 100755 tests/install-mount-idmapped.sh create mode 100755 tests/portable_signatures.test diff --git a/build.sh b/build.sh index 4e2f1bb7353b..0920599b2780 100755 --- a/build.sh +++ b/build.sh @@ -114,6 +114,11 @@ if [ $ret -eq 0 ]; then grep "skipped" tests/fsverity.log && \ grep "skipped" tests/fsverity.log | wc -l fi + if [ -f tests/portable_signatures.log ]; then + [ -n "$CI" ] && cat tests/portable_signatures.log || tail tests/portable_signatures.log + grep "skipped" tests/portable_signatures.log && \ + grep "skipped" tests/portable_signatures.log | wc -l + fi exit 0 fi diff --git a/ci/fedora.sh b/ci/fedora.sh index 198034a34e3c..3f75d2e1ddbd 100755 --- a/ci/fedora.sh +++ b/ci/fedora.sh @@ -47,7 +47,11 @@ yum -y install \ which \ zstd \ haveged \ - systemd + systemd \ + keyutils \ + e2fsprogs \ + acl \ + libcap yum -y install docbook5-style-xsl || true yum -y install swtpm || true @@ -59,3 +63,4 @@ fi yum -y install softhsm || true ./tests/install-fsverity.sh +./tests/install-mount-idmapped.sh diff --git a/tests/Makefile.am b/tests/Makefile.am index 305082483f36..421fac577b55 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -2,7 +2,7 @@ check_SCRIPTS = TESTS = $(check_SCRIPTS) check_SCRIPTS += ima_hash.test sign_verify.test boot_aggregate.test \ - fsverity.test + fsverity.test portable_signatures.test clean-local: -rm -f *.txt *.out *.sig *.sig2 diff --git a/tests/install-mount-idmapped.sh b/tests/install-mount-idmapped.sh new file mode 100755 index 000000000000..e9768e2fbf7a --- /dev/null +++ b/tests/install-mount-idmapped.sh @@ -0,0 +1,7 @@ +#!/bin/sh + +git clone https://github.com/brauner/mount-idmapped.git +cd mount-idmapped +gcc -o mount-idmapped mount-idmapped.c +cd .. +rm -rf mount-idmapped diff --git a/tests/portable_signatures.test b/tests/portable_signatures.test new file mode 100755 index 000000000000..a6d79c929281 --- /dev/null +++ b/tests/portable_signatures.test @@ -0,0 +1,1173 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# Copyright (C) 2022-2023 Roberto Sassu <roberto.sassu@xxxxxxxxxx> +# +# Check if operations on files with EVM portable signatures succeed. + +trap cleanup SIGINT SIGTERM SIGSEGV EXIT + +# Base VERBOSE on the environment variable, if set. +VERBOSE="${VERBOSE:-0}" +TST_EVM_CHANGE_MODE="${TST_EVM_CHANGE_MODE:-0}" +UML_MODE="${UML_MODE:-0}" + +# From security/integrity/evm/evm.h in kernel source directory. +let "EVM_INIT_HMAC=0x0001" +let "EVM_INIT_X509=0x0002" +let "EVM_ALLOW_METADATA_WRITES=0x0004" +let "EVM_SETUP_COMPLETE=0x80000000" + +cd "$(dirname "$0")" +export PATH=$PWD/../src:$PWD/../mount-idmapped:$PATH +export LD_LIBRARY_PATH=$LD_LIBRARY_PATH +. ./functions.sh +_require evmctl + +_cleanup() { + if [ "$loop_mounted" = "1" ]; then + popd > /dev/null + + if [ -n "$mountpoint_idmapped" ]; then + umount $mountpoint_idmapped + fi + + umount $mountpoint + fi + + if [ -n "$dev" ]; then + losetup -d $dev + fi + + if [ -n "$image" ]; then + rm -f $image + fi + + if [ -n "$key_path_der" ]; then + rm -f $key_path_der + fi + + if [ -n "$mountpoint" ]; then + rm -Rf $mountpoint + fi + + if [ -n "$mountpoint_idmapped" ]; then + rm -Rf $mountpoint_idmapped + fi +} + +cleanup() { + _cleanup_user_mode _cleanup + _report_exit_and_cleanup +} + +get_xattr() { + 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($2, temp, "\""); v=temp[2] }; print v}' +} + +# Use the fsuuid= IMA policy keyword to select only files created/used by the +# tests below. Also use fowner= to differentiate between files created/used by +# individual tests. +IMA_UUID="28b23254-9467-44c0-b6ba-34b12e85a26d" +APPRAISE_DIGSIG_FOWNER=2000 +APPRAISE_DIGSIG_RULE="appraise fsuuid=$IMA_UUID fowner=$APPRAISE_DIGSIG_FOWNER appraise_type=imasig" +MEASURE_FOWNER=2001 +MEASURE_RULE="measure fsuuid=$IMA_UUID fowner=$MEASURE_FOWNER template=ima-sig" +APPRAISE_FOWNER=2002 +APPRAISE_RULE="appraise fsuuid=$IMA_UUID fowner=$APPRAISE_FOWNER" +METADATA_CHANGE_FOWNER=3001 +METADATA_CHANGE_FOWNER_2=3002 + +check_load_ima_rule() { + rule_loaded=$(cat /sys/kernel/security/ima/policy | grep "$1") + if [ -z "$rule_loaded" ]; then + new_policy=$(mktemp -p $mountpoint) + echo $1 > $new_policy + evmctl sign -o -a sha256 --imasig --key $key_path $new_policy &> /dev/null + echo $new_policy > /sys/kernel/security/ima/policy + result=$? + rm -f $new_policy + + if [ $result -ne 0 ]; then + echo "${RED}Failed to set IMA policy${NORM}" + return $FAIL + fi + fi + + return $OK +} + +# The purpose of this test is to verify that the patch 'ima: Allow imasig +# requirement to be satisfied by EVM portable signatures' didn't break the +# current behavior (IMA signatures still satisfy the imasig requirement). +check_ima_sig_appraisal() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + if [ $((evm_value & (EVM_INIT_X509 | EVM_INIT_HMAC))) -ne 0 ]; then + echo "${CYAN}EVM mode 0 required${NORM}" + return $SKIP + fi + + echo "test" > test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + evmctl ima_sign -a sha256 --key $key_path test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot sign test-file${NORM}" + return $FAIL + fi + + chown $APPRAISE_DIGSIG_FOWNER test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change owner of test-file${NORM}" + return $FAIL + fi + + check_load_ima_rule "$APPRAISE_DIGSIG_RULE" + result=$? + if [ $result -ne $OK ]; then + return $result + fi + + # Check if appraisal works. + cat test-file > /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file${NORM}" + return $FAIL + fi + + # Ensure that files with IMA signature cannot be updated (immutable). + echo "test" 2> /dev/null >> test-file + if [ $? -eq 0 ]; then + echo "${RED}Write to test-file should not succeed (immutable file)${NORM}" + return $FAIL + fi + + return $OK +} + +cleanup_ima_sig_appraisal() { + rm -f test-file +} + +# Requires: +# - ima: Don't remove security.ima if file must not be appraised +# +# The purpose of this test is to verify that the patch 'ima: Introduce template +# field evmsig and write to field sig as fallback' still allows IMA signatures +# to be displayed in the measurement list. +check_ima_sig_ima_measurement_list() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + echo "test" > test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + evmctl ima_sign -a sha256 --imasig --key $key_path test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot sign test-file${NORM}" + return $FAIL + fi + + chown $MEASURE_FOWNER test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change owner of test-file${NORM}" + return $FAIL + fi + + check_load_ima_rule "$MEASURE_RULE" + result=$? + if [ $result -ne $OK ]; then + return $result + fi + + # Read the file to add it to the measurement list. + cat test-file > /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file${NORM}" + return $FAIL + fi + + ima_sig_fs=$(get_xattr security.ima test-file) + if [ -z "$ima_sig_fs" ]; then + echo "${RED}security.ima not found${NORM}" + return $FAIL + fi + + # Search security.ima in the measurement list. + ima_sig_list=$(cat /sys/kernel/security/ima/ascii_runtime_measurements | awk '$6 == "'$ima_sig_fs'"') + if [ -z "$ima_sig_list" ]; then + echo "${RED}security.ima mismatch (xattr != measurement list)${NORM}" + return $FAIL + fi + + return $OK +} + +cleanup_ima_sig_ima_measurement_list() { + rm -f test-file +} + +# Requires: +# - evm: Execute evm_inode_init_security() only when an HMAC key is loaded +# +# The purpose of this test is to verify that new files can be created when EVM +# is initialized only with a public key. +check_create_file() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + # To trigger the bug we need to enable public key verification without HMAC key loaded. + if [ $((evm_value & $EVM_INIT_X509)) -ne $EVM_INIT_X509 ]; then + echo "${CYAN}EVM mode $EVM_INIT_X509 required${NORM}" + return $SKIP + fi + + if [ $((evm_value & $EVM_INIT_HMAC)) -eq $EVM_INIT_HMAC ]; then + echo "${CYAN}EVM mode $EVM_INIT_HMAC must be disabled${NORM}" + return $SKIP + fi + + echo "test" > test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + return $OK +} + +cleanup_create_file() { + rm -f test-file +} + +# Requires: +# - evm: Introduce evm_hmac_disabled() to safely ignore verification errors +# - evm: Allow xattr/attr operations for portable signatures +# - evm: Execute evm_inode_init_security() only when an HMAC key is loaded +# +# The purpose of this test is to verify that EVM with the patches above allows +# metadata to copied one by one, even if the portable signature verification +# temporarily fails until the copy is completed. +check_cp_preserve_xattrs() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + if [ $evm_value -ne $EVM_INIT_X509 ]; then + echo "${CYAN}EVM mode $EVM_INIT_X509 required${NORM}" + return $SKIP + fi + + echo "test" > test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + evmctl sign -o -a sha256 --imahash --key $key_path test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot sign test-file${NORM}" + return $FAIL + fi + + # Check if cp is allowed to set metadata for the new file. + cp -a test-file test-file.copy + if [ $? -ne 0 ]; then + echo "${RED}Cannot copy test-file with attrs/xattrs preserved${NORM}" + return $FAIL + fi + + return $OK +} + +cleanup_cp_preserve_xattrs() { + rm -f test-file test-file.copy +} + +# Requires: +# - evm: Introduce evm_hmac_disabled() to safely ignore verification errors +# - evm: Allow xattr/attr operations for portable signatures +# - evm: Execute evm_inode_init_security() only when an HMAC key is loaded +# - ima: Don't remove security.ima if file must not be appraised +# +# The purpose of this test is similar to that of the previous test, with the +# difference that tar is used instead of cp. One remark is that the owner is +# intentionally different (or it should be) from the current owner, to +# incrementally test the patches without 'evm: Allow setxattr() and setattr() +# for unmodified metadata'. +check_tar_extract_xattrs_different_owner() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + if [ $evm_value -ne $EVM_INIT_X509 ]; then + echo "${CYAN}EVM mode $EVM_INIT_X509 required${NORM}" + return $SKIP + fi + + mkdir in out + if [ $? -ne 0 ]; then + echo "${RED}Cannot create directories${NORM}" + return $FAIL + fi + + echo "test" > in/test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + chown 3000 in/test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change owner of test-file${NORM}" + return $FAIL + fi + + chmod 600 in/test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change mode of test-file${NORM}" + return $FAIL + fi + + evmctl sign -o -a sha256 --imahash --key $key_path in/test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot sign test-file${NORM}" + return $FAIL + fi + + tar --xattrs-include=* -cf test-archive.tar in/test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot create archive with xattrs${NORM}" + return $FAIL + fi + + # Check if tar is allowed to set metadata for the extracted file. + # Ensure that the owner from the archive is different from the + # owner of the extracted file to avoid that portable signature + # verification succeeds before restoring original metadata + # (a patch allows modification of immutable metadata if portable + # signature verification fails). + tar --xattrs-include=* -xf test-archive.tar -C out + if [ $? -ne 0 ]; then + echo "${RED}Cannot extract archive with xattrs${NORM}" + return $FAIL + fi + + return $OK +} + +cleanup_tar_extract_xattrs_different_owner() { + rm -Rf in out test-archive.tar +} + +# Requires: +# - evm: Introduce evm_hmac_disabled() to safely ignore verification errors +# - evm: Allow xattr/attr operations for portable signatures +# - evm: Pass user namespace to set/remove xattr hooks +# - evm: Allow setxattr() and setattr() for unmodified metadata +# - evm: Execute evm_inode_init_security() only when an HMAC key is loaded +# - ima: Don't remove security.ima if file must not be appraised +# +# The purpose of this test is similar to that of the previous two tests. The +# difference is that tar is used instead of cp, and the extracted files have +# the same owner as the current one. Thus, this test requires 'evm: Allow +# setxattr() and setattr() for unmodified metadata'. +check_tar_extract_xattrs_same_owner() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + if [ $evm_value -ne $EVM_INIT_X509 ]; then + echo "${CYAN}EVM mode $EVM_INIT_X509 required${NORM}" + return $SKIP + fi + + mkdir in out + if [ $? -ne 0 ]; then + echo "${RED}Cannot create directories${NORM}" + return $FAIL + fi + + echo "test" > in/test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + evmctl sign -o -a sha256 --imahash --key $key_path in/test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot sign test-file${NORM}" + return $FAIL + fi + + tar --xattrs-include=* -cf test-archive.tar in/test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot create archive with xattrs${NORM}" + return $FAIL + fi + + # Check if tar is allowed to set metadata for the extracted file. + # This test is different from the previous one, as the owner + # from the archive is the same of the owner of the extracted + # file. tar will attempt anyway to restore the original owner but + # unlike the previous test, portable signature verification already + # succeeds at the time the owner is set (another patch allows + # metadata operations if those operations don't modify current + # values). + tar --xattrs-include=* -xf test-archive.tar -C out + if [ $? -ne 0 ]; then + echo "${RED}Cannot extract archive with xattrs${NORM}" + return $FAIL + fi + + return $OK +} + +cleanup_tar_extract_xattrs_same_owner() { + rm -Rf in out test-archive.tar +} + +# Requires: +# - evm: Introduce evm_hmac_disabled() to safely ignore verification errors +# - evm: Allow xattr/attr operations for portable signatures +# - evm: Pass user namespace to set/remove xattr hooks +# - evm: Allow setxattr() and setattr() for unmodified metadata +# - ima: Don't remove security.ima if file must not be appraised +# - evm: Execute evm_inode_init_security() only when an HMAC key is loaded +# +# The purpose of this test is to further verify the patches above, by executing +# commands to set the same or different metadata. Setting the same metadata +# should be allowed, setting different metadata should be denied. +check_metadata_change() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + if [ $evm_value -ne $EVM_INIT_X509 ]; then + echo "${CYAN}EVM mode $EVM_INIT_X509 required${NORM}" + return $SKIP + fi + + echo "test" > test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + chown $METADATA_CHANGE_FOWNER test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change owner of test-file${NORM}" + return $FAIL + fi + + chgrp $METADATA_CHANGE_FOWNER test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change group of test-file${NORM}" + return $FAIL + fi + + chmod 2644 test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change mode of test-file${NORM}" + return $FAIL + fi + + evmctl sign -o -a sha256 --imahash --key $key_path test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot sign test-file${NORM}" + return $FAIL + fi + + # If metadata modification is not allowed, EVM should deny any + # operation that modifies metadata. Check if setting the same + # value is allowed. + chown $METADATA_CHANGE_FOWNER test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot set same owner for test-file${NORM}" + return $FAIL + fi + + # Setting a different value should not be allowed. + chown $METADATA_CHANGE_FOWNER_2 test-file 2> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}Owner change for test-file should not be allowed (immutable metadata)${NORM}" + return $FAIL + fi + + # Repeat the test for the file mode. + chmod 2644 test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot set same mode for test-file${NORM}" + return $FAIL + fi + + chmod 2666 test-file 2> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}Mode change for test-file should not be allowed (immutable metadata)${NORM}" + return $FAIL + fi + + if [ -n "$(which chcon 2> /dev/null)" ] && [ -n "$(which getenforce 2> /dev/null)" ] && [ "$(getenforce 2> /dev/null)" != "Disabled" ]; then + # Repeat the test for the SELinux label. + label=$(get_xattr security.selinux test-file) + + if [ -n "$label" ]; then + chcon $label test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot set same security.selinux for test-file${NORM}" + return $FAIL + fi + fi + + chcon unconfined_u:object_r:null_device_t:s0 test-file 2> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}security.selinux change for test file should not be allowed (immutable metadata)${NORM}" + return $FAIL + fi + fi + + # Repeat the test for the IMA signature. + ima_xattr=$(get_xattr security.ima test-file) + if [ -z "$ima_xattr" ]; then + echo "${RED}security.ima not found${NORM}" + return $FAIL + fi + + setfattr -n security.ima -v 0x$ima_xattr test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot set same security.ima for test-file${NORM}" + return $FAIL + fi + + last_char=${ima_xattr: -1} + ((last_char += 1)) + ((last_char %= 10)) + ima_xattr=${ima_xattr:0:-1}$last_char + + setfattr -n security.ima -v 0x$ima_xattr test-file 2> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}Change of security.ima for test-file should not be allowed (immutable metadata)${NORM}" + return $FAIL + fi + + # Repeat the test for ACLs. + msg=$(exec 2>&1 && setfacl --set u::rw,g::r,o::r,m:r test-file) + if [ $? -ne 0 ]; then + if [ "${msg%not supported}" != "$msg" ]; then + return $OK + fi + + echo "${RED}Cannot preserve system.posix_acl_access for test-file${NORM}" + return $FAIL + fi + + setfacl --set u::rw,g::r,o::r,m:rw test-file 2> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}Change of system.posix_acl_access for test-file should not be allowed (immutable metadata)${NORM}" + return $FAIL + fi + + if [ -n "$mountpoint_idmapped" ]; then + pushd $mountpoint_idmapped > /dev/null + + # Repeat the test for ACLs on an idmapped mount. + # + # This test relies on the fact that the caller of this script (root) is in + # the same owning group of test-file (in the idmapped mount the group is + # root, not $METADATA_CHANGE_FOWNER and, for this reason, the S_ISGID bit + # is not cleared. If EVM was not aware of the mapping, it would have + # determined that root is not in the owning group of test-file and given + # that also CAP_FSETID is cleared, the S_ISGID bit would have been cleared + # and thus the operation would fail (file metadata changed). + capsh --drop='cap_fsetid' -- -c 'setfacl --set u::rw,g::r,o::r test-file' + if [ $? -ne 0 ]; then + echo "${RED}Cannot preserve system.posix_acl_access for test-file${NORM}" + popd + return $FAIL + fi + + popd > /dev/null + fi + + return $OK +} + +cleanup_metadata_change() { + rm -f test-file +} + +# Requires: +# - evm: Introduce evm_revalidate_status() +# - evm: Execute evm_inode_init_security() only when an HMAC key is loaded +# +# Note: +# This test can be run if EVM_ALLOW_METADATA_WRITES is set in advance +# before running this script. If it is not set before, this script sets +# EVM_SETUP_COMPLETE, disabling further EVM mode modifications until reboot. +# +# Without EVM_ALLOW_METADATA_WRITES, EVM_SETUP_COMPLETE is necessary to ignore +# the INTEGRITY_NOLABEL and INTEGRITY_NOXATTRS errors. +# +# The purpose of this test is to verify that IMA detected a metadata change +# when EVM_ALLOW_METADATA_WRITES is set (metadata operations are always +# allowed). After the first successful appraisal, the test intentionally changes +# metadata and verifies that IMA revoked access to the file. The test also +# verifies that IMA grants access again to the file after restoring the correct +# metadata. +check_evm_revalidate() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + if [ $evm_value -ne $(($EVM_INIT_X509 | $EVM_ALLOW_METADATA_WRITES)) ]; then + echo "${CYAN}EVM mode $(($EVM_INIT_X509 | $EVM_ALLOW_METADATA_WRITES)) required, execute echo 4 > /sys/kernel/security/evm before running this test${NORM}" + return $SKIP + fi + + echo "test" > test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + chmod 600 test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change mode of test-file${NORM}" + return $FAIL + fi + + # We need to defer setting the correct owner, as there could be + # already an IMA policy rule preventing evmctl from reading the + # file to calculate the digest. + evmctl sign -o -a sha256 --imahash --uid $APPRAISE_FOWNER --key $key_path test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot sign test-file${NORM}" + return $FAIL + fi + + chown $APPRAISE_FOWNER test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change owner of test-file${NORM}" + return $FAIL + fi + + check_load_ima_rule "$APPRAISE_RULE" + result=$? + if [ $result -ne $OK ]; then + return $result + fi + + # Read the file so that IMA would not re-appraise it next time. + cat test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file${NORM}" + return $FAIL + fi + + # After enabling metadata modification, operations should succeed even + # if the file has a portable signature. However, the previously cached + # appraisal status should be invalidated. + chmod 644 test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change mode of test-file${NORM}" + return $FAIL + fi + + # Here check if IMA re-appraised the file. The read should fail + # since now file metadata is invalid. + cat test-file &> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}Read of test-file should not succeed (invalid mode)${NORM}" + return $FAIL + fi + + # Restore metadata back to the original value. + chmod 600 test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot restore original mode of test-file${NORM}" + return $FAIL + fi + + # Ensure that now IMA appraisal succeeds. + cat test-file > /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file after restoring correct mode${NORM}" + return $FAIL + fi + + if [ -n "$(which chcon 2> /dev/null)" ] && [ -n "$(which getenforce 2> /dev/null)" ] && [ "$(getenforce 2> /dev/null)" != "Disabled" ]; then + # Repeat the test for the SELinux label. + label=$(get_xattr security.selinux test-file) + + chcon unconfined_u:object_r:null_device_t:s0 test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change security.selinux of test-file${NORM}" + return $FAIL + fi + + cat test-file &> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}Read of test-file should not succeed (invalid security.selinux)${NORM}" + return $FAIL + fi + + if [ -n "$label" ]; then + chcon $label test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot restore original security.selinux of test-file${NORM}" + return $FAIL + fi + else + attr -S -r selinux test-file + fi + + cat test-file > /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file after restoring correct security.selinux${NORM}" + return $FAIL + fi + fi + + # Repeat the test for the IMA signature. + ima_xattr=$(get_xattr security.ima test-file) + if [ -z "$ima_xattr" ]; then + echo "${RED}security.ima not found${NORM}" + return $FAIL + fi + + last_char=${ima_xattr: -1} + ((last_char += 1)) + ((last_char %= 10)) + ima_xattr_new=${ima_xattr:0:-1}$last_char + + setfattr -n security.ima -v 0x$ima_xattr_new test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot set security.ima of test-file${NORM}" + return $FAIL + fi + + cat test-file &> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}Read of test-file should not succeed (invalid security.ima)${NORM}" + return $FAIL + fi + + setfattr -n security.ima -v 0x$ima_xattr test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot restore original security.ima of test-file${NORM}" + return $FAIL + fi + + cat test-file > /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file after restoring correct security.ima${NORM}" + return $FAIL + fi + + # Repeat the test for the EVM signature. + evm_xattr=$(get_xattr security.evm test-file) + if [ -z "$evm_xattr" ]; then + echo "${RED}security.evm not found${NORM}" + return $FAIL + fi + + last_char=${evm_xattr: -1} + ((last_char += 1)) + ((last_char %= 10)) + evm_xattr_new=${evm_xattr:0:-1}$last_char + + setfattr -n security.evm -v 0x$evm_xattr_new test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot set security.evm of test-file${NORM}" + return $FAIL + fi + + cat test-file &> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}Read of test-file should not succeed (invalid security.evm)${NORM}" + return $FAIL + fi + + setfattr -n security.evm -v 0x$evm_xattr test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot restore original security.evm of test-file${NORM}" + return $FAIL + fi + + cat test-file > /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file after restoring correct security.evm${NORM}" + return $FAIL + fi + + # Repeat the test for ACLs. + setfacl -m u::rwx test-file 2> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot change system.posix_acl_access${NORM}" + return $FAIL + fi + + cat test-file &> /dev/null + if [ $? -eq 0 ]; then + echo "${RED}Read of test-file should not succeed (invalid system.posix_acl_access)${NORM}" + return $FAIL + fi + + setfacl -m u::rw test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot restore original system.posix_acl_access for test-file${NORM}" + return $FAIL + fi + + cat test-file > /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file after restoring correct system.posix_acl_access${NORM}" + return $FAIL + fi + + return $OK +} + +cleanup_evm_revalidate() { + rm -f test-file +} + +# Requires: +# - evm: Introduce evm_hmac_disabled() to safely ignore verification errors +# - evm: Introduce evm_revalidate_status() +# - ima: Allow imasig requirement to be satisfied by EVM portable signatures +# - evm: Execute evm_inode_init_security() only when an HMAC key is loaded +# +# The purpose of this test is to verify that IMA manages files with an EVM +# portable signature similarly to those with an IMA signature: content can be +# written to new files after adding the signature and files can be accessed +# when the imasig requirement is specified in the IMA policy. +check_evm_portable_sig_ima_appraisal() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + if [ $((evm_value & EVM_INIT_X509)) -ne $EVM_INIT_X509 ]; then + echo "${CYAN}EVM flag $EVM_INIT_X509 required${NORM}" + return $SKIP + fi + + echo "test" > test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + chmod 600 test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change mode of test-file${NORM}" + return $FAIL + fi + + # We need to defer setting the correct owner, as there could be + # already an IMA policy rule preventing evmctl from reading the + # file to calculate the digest. + evmctl sign -o -a sha256 --imahash --uid $APPRAISE_DIGSIG_FOWNER --key $key_path test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot sign test-file${NORM}" + return $FAIL + fi + + chown $APPRAISE_DIGSIG_FOWNER test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change owner of test-file${NORM}" + return $FAIL + fi + + check_load_ima_rule "$APPRAISE_DIGSIG_RULE" + result=$? + if [ $result -ne $OK ]; then + return $result + fi + + # Ensure that a file with a portable signature satisfies the + # appraise_type=imasig requirement specified in the IMA policy. + cat test-file > /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file${NORM}" + return $FAIL + fi + + # Even files with a portable signature should be considered as + # immutable by IMA. Write should fail. + echo "test" 2> /dev/null >> test-file + if [ $? -eq 0 ]; then + echo "${RED}Write to test-file should not succeed (immutable metadata)${NORM}" + return $FAIL + fi + + tar --xattrs-include=* -cf test-archive.tar test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot create archive with xattrs${NORM}" + return $FAIL + fi + + mkdir out + + # Appraisal of the new file, extracted by tar, should succeed + # not only if the new file has an IMA signature but also if + # it has a portable signature. + tar --xattrs-include=* -xf test-archive.tar -C out + if [ $? -ne 0 ]; then + echo "${RED}Cannot extract archive with xattrs${NORM}" + return $FAIL + fi + + # Check if xattrs have been correctly set. + xattr_orig=$(get_xattr security.selinux test-file) + xattr=$(get_xattr security.selinux out/test-file) + if [ "$xattr" != "$xattr_orig" ]; then + echo "${RED}security.selinux mismatch between original and extracted file${NORM}" + return $FAIL + fi + + xattr_orig=$(get_xattr security.ima test-file) + xattr=$(get_xattr security.ima out/test-file) + if [ "$xattr" != "$xattr_orig" ]; then + echo "${RED}security.ima mismatch between original and extracted file${NORM}" + return $FAIL + fi + + xattr_orig=$(get_xattr security.evm test-file) + xattr=$(get_xattr security.evm out/test-file) + if [ "$xattr" != "$xattr_orig" ]; then + echo "${RED}security.evm mismatch between original and extracted file${NORM}" + return $FAIL + fi + + # Check if attrs have been correctly set. + owner=$(stat -c "%u" out/test-file) + if [ "$owner" != "$APPRAISE_DIGSIG_FOWNER" ]; then + echo "${RED}owner mismatch between original and extracted file${NORM}" + return $FAIL + fi + + mode=$(stat -c "%a" out/test-file) + if [ "$mode" != "600" ]; then + echo "${RED}mode mismatch between original and extracted file${NORM}" + return $FAIL + fi + + return $OK +} + +cleanup_evm_portable_sig_ima_appraisal() { + rm -f test-file test-archive.tar + rm -Rf out +} + +# Requires: +# - ima: Introduce template field evmsig and write to field sig as fallback +# - evm: Execute evm_inode_init_security() only when an HMAC key is loaded +# - ima: Don't remove security.ima if file must not be appraised +# +# The purpose of this test is to verify that the EVM portable signature is +# displayed in the measurement list. +check_evm_portable_sig_ima_measurement_list() { + echo "Test: ${FUNCNAME[0]} (evm_value: $evm_value)" + + echo "test" > test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot write test-file${NORM}" + return $FAIL + fi + + chown $MEASURE_FOWNER test-file + if [ $? -ne 0 ]; then + echo "${RED}Cannot change owner of test-file${NORM}" + return $FAIL + fi + + evmctl sign -o -a sha256 --imahash --key $key_path test-file &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot sign test-file${NORM}" + return $FAIL + fi + + check_load_ima_rule "$MEASURE_RULE" + result=$? + if [ $result -ne $OK ]; then + return $result + fi + + # Invalidate previous measurement to add new entry + touch test-file + + # Read the file to add it to the measurement list. + cat test-file > /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Cannot read test-file${NORM}" + return $FAIL + fi + + evm_sig_fs=$(get_xattr security.evm test-file) + if [ -z "$evm_sig_fs" ]; then + echo "${RED}security.evm not found${NORM}" + return $FAIL + fi + + # Search security.evm in the measurement list. + evm_sig_list=$(cat /sys/kernel/security/ima/ascii_runtime_measurements | awk '$6 == "'$evm_sig_fs'"') + if [ -z "$evm_sig_list" ]; then + echo "${RED}security.evm mismatch (xattr != measurement list)${NORM}" + return $FAIL + fi + + return $OK +} + +cleanup_evm_portable_sig_ima_measurement_list() { + rm -f test-file +} + +# Run in User Mode Linux. +_run_user_mode ../linux $PWD/$(basename $0) "UML_MODE=$UML_MODE PATH=$PATH LD_LIBRARY_PATH=$LD_LIBRARY_PATH VERBOSE=$VERBOSE TST_EVM_CHANGE_MODE=$TST_EVM_CHANGE_MODE TST_KEY_PATH=$TST_KEY_PATH" + +# Run in User Mode Linux (skipped test). +_run_user_mode ../linux $PWD/$(basename $0) "UML_MODE=$UML_MODE PATH=$PATH LD_LIBRARY_PATH=$LD_LIBRARY_PATH VERBOSE=$VERBOSE TST_EVM_CHANGE_MODE=$TST_EVM_CHANGE_MODE TST_KEY_PATH=$TST_KEY_PATH TST_LIST=check_evm_revalidate" + +# Exit from the parent if UML was used. +_exit_user_mode ../linux + +# Mount filesystems in UML environment. +_init_user_mode + +mountpoint=$(mktemp -d) +image=$(mktemp) + +if [ -z "$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 $SKIP +fi + +key_path="/lib/modules/$(uname -r)/source/certs/signing_key.pem" +if [ -f "$PWD/../signing_key.pem" ]; then + key_path=$PWD/../signing_key.pem +fi + +if [ -n "$TST_KEY_PATH" ]; then + key_path=$TST_KEY_PATH +fi + +if [ ${key_path:0:1} != "/" ]; then + echo "${RED}Absolute path required for the signing key${NORM}" + exit $FAIL +fi + +key_path_der=$(mktemp) + +if [ ! -f $key_path ]; then + echo "${CYAN}Kernel signing key not found in $key_path${NORM}" + exit $SKIP +fi + +if [ ! -f "/sys/kernel/security/evm" ]; then + echo "${CYAN}EVM support in the kernel disabled${NORM}" + exit $SKIP +fi + +# Assume that the EVM mode can be changed in a UML kernel +if [ -f $PWD/../linux ]; then + TST_EVM_CHANGE_MODE=1 +fi + +evm_value=$(cat /sys/kernel/security/evm) + +openssl x509 -in $key_path -out $key_path_der -outform der +cat $key_path_der | keyctl padd asymmetric pubkey %keyring:.ima &> /dev/null +if [ $? -ne 0 ]; then + echo "${RED}Public key cannot be added to the IMA keyring${NORM}" + exit $FAIL +fi + +dd if=/dev/zero of=$image bs=1M count=20 &> /dev/null +if [ $? -ne 0 ]; then + echo "${RED}Cannot create test image${NORM}" + exit $FAIL +fi + +dev=$(losetup -f $image --show) +if [ -z "$dev" ]; then + echo "${RED}Cannot create loop device${NORM}" + exit $FAIL +fi + +mkfs.ext4 -U $IMA_UUID -b 4096 $dev &> /dev/null +if [ $? -ne 0 ]; then + echo "${RED}Cannot format $dev${NORM}" + exit $FAIL +fi + +mount -o i_version $dev $mountpoint +if [ $? -ne 0 ]; then + echo "${RED}Cannot mount loop device${NORM}" + exit $FAIL +fi + +if [ -n "$(which mount-idmapped 2> /dev/null)" ]; then + mountpoint_idmapped=$(mktemp -d) + mount-idmapped --map-mount b:$METADATA_CHANGE_FOWNER:0:1 $mountpoint $mountpoint_idmapped + if [ $? -ne 0 ]; then + echo "${RED}mount-idmapped failed${NORM}" + exit $FAIL + fi +fi + +loop_mounted=1 +pushd $mountpoint > /dev/null + +expect_pass check_ima_sig_appraisal +cleanup_ima_sig_appraisal +expect_pass check_ima_sig_ima_measurement_list +cleanup_ima_sig_ima_measurement_list + +if [ $(echo -e "$(uname -r)\n5.12" | sort -V | head -n 1) != "5.12" ]; then + exit $OK +fi + +if [ $((evm_value & EVM_INIT_X509)) -ne $EVM_INIT_X509 ] && [ "$TST_EVM_CHANGE_MODE" -eq 1 ]; then + cat $key_path_der | keyctl padd asymmetric pubkey %keyring:.evm &> /dev/null + if [ $? -ne 0 ]; then + echo "${RED}Public key cannot be added to the EVM keyring${NORM}" + exit $FAIL + fi + + echo $EVM_INIT_X509 > /sys/kernel/security/evm 2> /dev/null +fi + +if [ $(expr index "$TST_LIST" "check_evm_revalidate") -gt 0 ] && [ "$TST_EVM_CHANGE_MODE" -eq 1 ]; then + echo $EVM_ALLOW_METADATA_WRITES > /sys/kernel/security/evm 2> /dev/null +fi + +# We cannot determine from securityfs if EVM_SETUP_COMPLETE is set, so we set it unless EVM_ALLOW_METADATA_WRITES is set. +if [ $((evm_value & EVM_ALLOW_METADATA_WRITES)) -ne $EVM_ALLOW_METADATA_WRITES ] && [ "$TST_EVM_CHANGE_MODE" -eq 1 ]; then + echo $EVM_SETUP_COMPLETE > /sys/kernel/security/evm 2> /dev/null +fi + +evm_value=$(cat /sys/kernel/security/evm) + +expect_pass check_create_file +cleanup_create_file +expect_pass check_cp_preserve_xattrs +cleanup_cp_preserve_xattrs +expect_pass check_tar_extract_xattrs_different_owner +cleanup_tar_extract_xattrs_different_owner +expect_pass check_tar_extract_xattrs_same_owner +cleanup_tar_extract_xattrs_same_owner +expect_pass check_metadata_change +cleanup_metadata_change +expect_pass check_evm_revalidate +cleanup_evm_revalidate +expect_pass check_evm_portable_sig_ima_appraisal +cleanup_evm_portable_sig_ima_appraisal +expect_pass check_evm_portable_sig_ima_measurement_list +cleanup_evm_portable_sig_ima_measurement_list -- 2.25.1
