test demonstrate a bug on overlayfs on current mainline kernel when combining IMA with EVM. Based on reproducer made by Ignaz Forster <iforster@xxxxxxx> used for not upstreamed patchset [1] and previous report [2]. IMA only behavior has already been fixed [3]. NOTE: backup variables are needed because ima_setup.sh calling tst_mount as well when TMPDIR is on tmpfs device. Documentation is based on Ignaz Forster instructions for openSUSE [4]. [1] https://www.spinics.net/lists/linux-integrity/msg05926.html [2] https://www.spinics.net/lists/linux-integrity/msg03593.html [3] https://patchwork.kernel.org/patch/10776231/ [4] http://lists.linux.it/pipermail/ltp/2019-May/011956.html Tested-by: Ignaz Forster <iforster@xxxxxxx> Acked-by: Mimi Zohar <zohar@xxxxxxxxxxxxx> Signed-off-by: Petr Vorel <pvorel@xxxxxxx> --- runtest/ima | 1 + .../security/integrity/ima/tests/README.md | 83 +++++++++++++++++ .../integrity/ima/tests/evm_overlay.sh | 93 +++++++++++++++++++ .../security/integrity/ima/tests/ima_setup.sh | 4 +- 4 files changed, 179 insertions(+), 2 deletions(-) create mode 100644 testcases/kernel/security/integrity/ima/tests/README.md create mode 100755 testcases/kernel/security/integrity/ima/tests/evm_overlay.sh diff --git a/runtest/ima b/runtest/ima index bcae16bb7..f3ea88cf0 100644 --- a/runtest/ima +++ b/runtest/ima @@ -3,3 +3,4 @@ ima_measurements ima_measurements.sh ima_policy ima_policy.sh ima_tpm ima_tpm.sh ima_violations ima_violations.sh +evm_overlay evm_overlay.sh diff --git a/testcases/kernel/security/integrity/ima/tests/README.md b/testcases/kernel/security/integrity/ima/tests/README.md new file mode 100644 index 000000000..961b68a38 --- /dev/null +++ b/testcases/kernel/security/integrity/ima/tests/README.md @@ -0,0 +1,83 @@ +IMA + EVM testing +================= + +IMA tests +--------- + +`ima_measurements.sh` require builtin IMA tcb policy to be loaded +(`ima_policy=tcb` or `ima_policy=appraise_tcb` kernel parameter). +Although custom policy which contains which may contain the equivalent +measurement tcb rules can be loaded via dracut, systemd or later manually +from user space, detecting it would require `IMA_READ_POLICY=y` therefore +ignore this option. + +Mandatory kernel configuration for IMA: +``` +CONFIG_INTEGRITY=y +CONFIG_IMA=y +``` + +EVM tests +--------- + +`evm_overlay.sh` requires to builtin IMA appraise tcb policy (e.g. `ima_policy=appraise_tcb` +kernel parameter) which appraises the integrity of all files owned by root and EVM setup. +Again, for simplicity ignore possibility to load reuired rules via custom policy. + +Mandatory kernel configuration for IMA & EVM: +``` +CONFIG_INTEGRITY=y +CONFIG_INTEGRITY_SIGNATURE=y +CONFIG_IMA=y +CONFIG_IMA_APPRAISE=y +CONFIG_EVM=y +CONFIG_KEYS=y +CONFIG_TRUSTED_KEYS=y +CONFIG_ENCRYPTED_KEYS=y +``` + +Example of installing IMA + EVM on openSUSE: + +* Boot install system with `ima_policy=appraise_tcb ima_appraise=fix evm=fix` kernel parameters + (for IMA measurement, IMA appraisal and EVM protection) +* Proceed with installation until summary screen, but do not start the installation yet +* Select package `dracut-ima` (required for early boot EVM support) for installation + (Debian based distros already contain IMA + EVM support in `dracut` package) +* Change to a console window and run commands to generate keys required by EVM: +``` +# mkdir /etc/keys +# user_key=$(keyctl add user kmk-user "`dd if=/dev/urandom bs=1 count=32 2>/dev/null`" @u) +# keyctl pipe "$user_key" > /etc/keys/kmk-user.blob +# evm_key=$(keyctl add encrypted evm-key "new user:kmk-user 64" @u) +# keyctl pipe "$evm_key" >/etc/keys/evm.blob +# cat <<END >/etc/sysconfig/masterkey +MASTERKEYTYPE="user" +MASTERKEY="/etc/keys/kmk-user.blob" +END +# cat <<END >/etc/sysconfig/evm +EVMKEY="/etc/keys/evm.blob" +END +# mount -t securityfs security /sys/kernel/security +# echo 1 >/sys/kernel/security/evm +``` + +* Go back to the installation summary screen and start the installation +* During the installation execute the following commands from the console: +``` +# cp -r /etc/keys /mnt/etc/ # Debian based distributions: use /target instead of /mnt +# cp /etc/sysconfig/{evm,masterkey} /mnt/etc/sysconfig/ +``` + +This should work on any distribution using dracut. +Loading EVM keys is also possible with initramfs-tools (Debian based distributions). + +Of course it's possible to install OS usual way, add keys later and fix missing xattrs with: +``` +evmctl -r ima_fix / +``` + +or with `find` if evmctl not available: +``` +find / \( -fstype rootfs -o -fstype ext4 -o -fstype btrfs -o -fstype xfs \) -exec sh -c "< '{}'" \; +``` +Again, fixing requires `ima_policy=appraise_tcb ima_appraise=fix evm=fix` kernel parameters. diff --git a/testcases/kernel/security/integrity/ima/tests/evm_overlay.sh b/testcases/kernel/security/integrity/ima/tests/evm_overlay.sh new file mode 100755 index 000000000..024b03917 --- /dev/null +++ b/testcases/kernel/security/integrity/ima/tests/evm_overlay.sh @@ -0,0 +1,93 @@ +#!/bin/sh +# Copyright (c) 2019 Petr Vorel <pvorel@xxxxxxx> +# Based on reproducer and further discussion with Ignaz Forster <iforster@xxxxxxx> +# Reproducer for not upstreamed patchset [1] and previous report [2]. +# [1] https://www.spinics.net/lists/linux-integrity/msg05926.html +# [2] https://www.spinics.net/lists/linux-integrity/msg03593.html + +TST_SETUP="setup" +TST_CLEANUP="cleanup" +TST_NEEDS_DEVICE=1 +TST_CNT=4 +. ima_setup.sh + +setup() +{ + EVM_FILE="/sys/kernel/security/evm" + + [ -f "$EVM_FILE" ] || tst_brk TCONF "EVM not enabled in kernel" + [ $(cat $EVM_FILE) -eq 1 ] || tst_brk TCONF "EVM not enabled for this boot" + + check_ima_policy "appraise_tcb" + + lower="$TST_MNTPOINT/lower" + upper="$TST_MNTPOINT/upper" + work="$TST_MNTPOINT/work" + merged="$TST_MNTPOINT/merged" + mkdir -p $lower $upper $work $merged + + device_backup="$TST_DEVICE" + TST_DEVICE="overlay" + + fs_type_backup="$TST_FS_TYPE" + TST_FS_TYPE="overlay" + + mntpoint_backup="$TST_MNTPOINT" + TST_MNTPOINT="$merged" + + params_backup="$TST_MNT_PARAMS" + TST_MNT_PARAMS="-o lowerdir=$lower,upperdir=$upper,workdir=$work" + + tst_mount + mounted=1 +} + +test1() +{ + local file="foo1.txt" + + tst_res TINFO "overwrite file in overlay" + EXPECT_PASS echo lower \> $lower/$file + EXPECT_PASS echo overlay \> $merged/$file +} + +test2() +{ + local file="foo2.txt" + + tst_res TINFO "append file in overlay" + EXPECT_PASS echo lower \> $lower/$file + EXPECT_PASS echo overlay \>\> $merged/$file +} + +test3() +{ + local file="foo3.txt" + + tst_res TINFO "create a new file in overlay" + EXPECT_PASS echo overlay \> $merged/$file +} + +test4() +{ + local f + + tst_res TINFO "read all created files" + for f in $(find $TST_MNTPOINT -type f); do + EXPECT_PASS cat $f \> /dev/null 2\> /dev/null + done +} + +cleanup() +{ + [ -n "$mounted" ] || return 0 + + tst_umount $TST_DEVICE + + TST_DEVICE="$device_backup" + TST_FS_TYPE="$fs_type_backup" + TST_MNTPOINT="$mntpoint_backup" + TST_MNT_PARAMS="$params_backup" +} + +tst_run diff --git a/testcases/kernel/security/integrity/ima/tests/ima_setup.sh b/testcases/kernel/security/integrity/ima/tests/ima_setup.sh index 606034fec..529b77529 100644 --- a/testcases/kernel/security/integrity/ima/tests/ima_setup.sh +++ b/testcases/kernel/security/integrity/ima/tests/ima_setup.sh @@ -66,14 +66,14 @@ print_ima_config() local config="/boot/config-$(uname -r)" local i - tst_res TINFO "/proc/cmdline: $(cat /proc/cmdline)" - if [ -r "$config" ]; then tst_res TINFO "IMA kernel config:" for i in $(grep ^CONFIG_IMA $config); do tst_res TINFO "$i" done fi + + tst_res TINFO "/proc/cmdline: $(cat /proc/cmdline)" } ima_setup() -- 2.21.0
