[LTP] [PATCH v4 4/4] ima: Add overlay test + doc

[Ignaz Forster]

Am 13.06.19 um 18:14 Uhr schrieb Petr Vorel:
> test demonstrate a bug on overlayfs on current mainline kernel when
> combining IMA with EVM.
> 
> Based on reproducer made by Ignaz Forster <iforster@suse.de>
> 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@suse.de>
> Acked-by: Mimi Zohar <zohar@linux.ibm.com>
> Signed-off-by: Petr Vorel <pvorel@suse.cz>
> ---
>   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).

This test requires "appraise_tcb" ("tcb" is not enough), as the errors 
only occur during appraisal.

> +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.

I guess this should be
"Although a custom policy, loaded via dracut, systemd or manually from 
user space, may contain equivalent measurement tcb rules, detecting them 
would [...]"

> +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`                              ^^
                              a

> +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.
                                                       ^q

> +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

I was missing the measurement option. ima_policy should have been
ima_policy='tcb|appraise_tcb' for the statement below to be true.

> +  (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:
                            ^
                            is

> +```
> +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.

Maybe also add the tcb option for measurement here.

Ignaz

> 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@suse.cz>
> +# Based on reproducer and further discussion with Ignaz Forster <iforster@suse.de>
> +# 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()
>