[PATCH ima-evm-utils] Add tests for MMAP_CHECK and MMAP_CHECK_REQPROT hooks
Roberto Sassu
roberto.sassu at huaweicloud.com
Thu Jan 26 16:38:12 UTC 2023
From: Roberto Sassu <roberto.sassu at huawei.com>
Add tests to ensure that, after applying the kernel patch 'ima: Align
ima_file_mmap() parameters with mmap_file LSM hook', the MMAP_CHECK hook
checks the protections applied by the kernel and not those requested by the
application.
Also ensure that after applying 'ima: Introduce MMAP_CHECK_REQPROT hook',
the MMAP_CHECK_REQPROT hook checks the protections requested by the
application.
Test both with the test_mmap application that by default requests the
PROT_READ protection flag. Its syntax is:
test_mmap <file> <mode>
where mode can be:
- exec: adds the PROT_EXEC protection flag to mmap()
- read_implies_exec: calls the personality() system call with
READ_IMPLIES_EXEC as the first argument before mmap()
- mprotect: adds the PROT_EXEC protection flag to a memory area in addition
to PROT_READ
- exec_on_writable: calls mmap() with PROT_EXEC on a file which has a
writable mapping
Check the different combinations of hooks/modes and ensure that a
measurement entry is found in the IMA measurement list only when it is
expected. No measurement entry should be found when only the PROT_READ
protection flag is requested or the matching policy rule has the
MMAP_CHECK_REQPROT hook and the personality() system call was called with
READ_IMPLIES_EXEC.
mprotect() with PROT_EXEC on an existing memory area protected with
PROT_READ should be denied (with an appraisal rule), regardless of the MMAP
hook specified in the policy. The same applies for mmap() with PROT_EXEC on
a file with a writable mapping.
Signed-off-by: Roberto Sassu <roberto.sassu at huawei.com>
---
tests/Makefile.am | 4 +-
tests/mmap_check.test | 282 ++++++++++++++++++++++++++++++++++++++++++
tests/test_mmap.c | 69 +++++++++++
3 files changed, 354 insertions(+), 1 deletion(-)
create mode 100755 tests/mmap_check.test
create mode 100644 tests/test_mmap.c
diff --git a/tests/Makefile.am b/tests/Makefile.am
index a0463b7b5b5d..ca9c4ca18380 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -2,7 +2,9 @@ check_SCRIPTS =
TESTS = $(check_SCRIPTS)
check_SCRIPTS += ima_hash.test sign_verify.test boot_aggregate.test \
- fsverity.test portable_signatures.test
+ fsverity.test portable_signatures.test mmap_check.test
+
+check_PROGRAMS := test_mmap
.PHONY: check_logs
check_logs:
diff --git a/tests/mmap_check.test b/tests/mmap_check.test
new file mode 100755
index 000000000000..2efdd8e01785
--- /dev/null
+++ b/tests/mmap_check.test
@@ -0,0 +1,282 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2022-2023 Roberto Sassu <roberto.sassu at huawei.com>
+#
+# Check the behavior of MMAP_CHECK and MMAP_CHECK_REQPROT
+
+trap '_report_exit_and_cleanup _cleanup_env cleanup' SIGINT SIGTERM SIGSEGV EXIT
+
+# Base VERBOSE on the environment variable, if set.
+VERBOSE="${VERBOSE:-0}"
+
+cd "$(dirname "$0")" || exit "$FAIL"
+export PATH=$PWD/../src:$PWD:$PATH
+export LD_LIBRARY_PATH=$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 "$g_mountpoint"
+ fi
+
+ if [ -n "$key_path_der" ]; then
+ rm -f "$key_path_der"
+ fi
+}
+
+# Use the fsuuid= IMA policy keyword to select only files created/used by the
+# tests below. Also use fowner= to differentiate between files created/used by
+# individual tests.
+IMA_UUID="28b23254-9467-44c0-b6ba-34b12e85a26e"
+MMAP_CHECK_FOWNER=2000
+MMAP_CHECK_REQPROT_FOWNER=2001
+MEASURE_MMAP_CHECK_RULE="measure func=MMAP_CHECK fsuuid=$IMA_UUID fowner=$MMAP_CHECK_FOWNER"
+MEASURE_MMAP_CHECK_REQPROT_RULE="measure func=MMAP_CHECK_REQPROT fsuuid=$IMA_UUID fowner=$MMAP_CHECK_REQPROT_FOWNER"
+APPRAISE_MMAP_CHECK_RULE="appraise func=MMAP_CHECK fsuuid=$IMA_UUID fowner=$MMAP_CHECK_FOWNER"
+APPRAISE_MMAP_CHECK_REQPROT_RULE="appraise func=MMAP_CHECK_REQPROT fsuuid=$IMA_UUID fowner=$MMAP_CHECK_REQPROT_FOWNER"
+
+check_load_ima_rule() {
+ local rule_loaded
+ local result
+ local new_policy
+
+ rule_loaded=$(grep "$1" /sys/kernel/security/ima/policy)
+ if [ -z "$rule_loaded" ]; then
+ new_policy=$(mktemp -p "$g_mountpoint")
+ echo "$1" > "$new_policy"
+ 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"
+}
+
+check_mmap() {
+ local hook="$1"
+ local arg="$2"
+ local test_file
+ local fowner
+ local rule
+ local result
+ local test_file_entry
+
+ if ! test_file=$(mktemp -p "$PWD"); then
+ echo "${RED}Cannot write $test_file${NORM}"
+ return "$FAIL"
+ fi
+
+ fowner="$MMAP_CHECK_FOWNER"
+ rule="$MEASURE_MMAP_CHECK_RULE"
+
+ if [ "$hook" = "MMAP_CHECK_REQPROT" ]; then
+ fowner="$MMAP_CHECK_REQPROT_FOWNER"
+ rule="$MEASURE_MMAP_CHECK_REQPROT_RULE"
+ fi
+
+ if ! chown "$fowner" "$test_file"; then
+ echo "${RED}Cannot change owner of $test_file${NORM}"
+ return "$FAIL"
+ fi
+
+ check_load_ima_rule "$rule"
+ result=$?
+ if [ $result -ne "$OK" ]; then
+ return $result
+ fi
+
+ test_mmap "$test_file" "$arg"
+
+ if [ "$TFAIL" != "yes" ]; then
+ echo -n "Test (expect: found): "
+ else
+ echo -n "Test (expect: not found): "
+ fi
+
+ echo -n "${FUNCNAME[0]} (hook=\"$hook\", test_mmap arg: \"$arg\") - "
+
+ test_file_entry=$(awk '$5 == "'"$test_file"'"' < /sys/kernel/security/ima/ascii_runtime_measurements)
+ if [ -z "$test_file_entry" ]; then
+ echo "not found"
+ return "$FAIL"
+ fi
+
+ echo "found"
+ return "$OK"
+}
+
+check_deny() {
+ local hook="$1"
+ local arg="$2"
+ local test_file
+ local fowner
+ local rule
+ local result
+
+ if ! test_file=$(mktemp -p "$PWD"); then
+ echo "${RED}Cannot write $test_file${NORM}"
+ return "$FAIL"
+ fi
+
+ echo "test" > "$test_file"
+
+ if ! evmctl ima_sign -a sha256 --key "$key_path" "$test_file" &> /dev/null; then
+ echo "${RED}Cannot sign $test_file${NORM}"
+ return "$FAIL"
+ fi
+
+ fowner="$MMAP_CHECK_FOWNER"
+ rule="$APPRAISE_MMAP_CHECK_RULE"
+
+ if [ "$hook" = "MMAP_CHECK_REQPROT" ]; then
+ fowner="$MMAP_CHECK_REQPROT_FOWNER"
+ rule="$APPRAISE_MMAP_CHECK_REQPROT_RULE"
+ fi
+
+ if ! chown "$fowner" "$test_file"; then
+ echo "${RED}Cannot change owner of $test_file${NORM}"
+ return "$FAIL"
+ fi
+
+ check_load_ima_rule "$rule"
+ result=$?
+ if [ $result -ne "$OK" ]; then
+ return $result
+ fi
+
+ if ! test_mmap "$test_file" exec > /dev/null; then
+ echo "${RED}Cannot read $test_file${NORM}"
+ return "$FAIL"
+ fi
+
+ echo -n "Test (expect: denied): ${FUNCNAME[0]} (hook=\"$hook\", test_mmap arg: \"$arg\") - "
+ if test_mmap "$test_file" "$arg"; then
+ echo "allowed"
+ return "$FAIL"
+ fi
+
+ echo "denied"
+
+ return "$OK"
+}
+
+# Run in the new environment if TST_ENV is set.
+_run_env "$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 "$TST_KERNEL"
+
+# Mount filesystems in the new environment.
+_init_env
+
+if [ "$(whoami)" != "root" ]; then
+ echo "${CYAN}This script must be executed as root${NORM}"
+ exit "$SKIP"
+fi
+
+if [ ! -f /sys/kernel/security/ima/policy ]; then
+ echo "${CYAN}IMA policy file not found${NORM}"
+ exit "$SKIP"
+fi
+
+if ! cat /sys/kernel/security/ima/policy &> /dev/null; then
+ echo "${CYAN}IMA policy file is not readable${NORM}"
+ exit "$SKIP"
+fi
+
+if [ -n "$TST_KEY_PATH" ]; then
+ if [ "${TST_KEY_PATH:0:1}" != "/" ]; then
+ echo "${RED}Absolute path required for the signing key${NORM}"
+ exit "$FAIL"
+ fi
+
+ if [ ! -f "$TST_KEY_PATH" ]; then
+ echo "${RED}Kernel signing key not found in $TST_KEY_PATH${NORM}"
+ exit "$FAIL"
+ fi
+
+ key_path="$TST_KEY_PATH"
+elif [ -f "$PWD/../signing_key.pem" ]; then
+ key_path="$PWD/../signing_key.pem"
+elif [ -f "/lib/modules/$(uname -r)/source/certs/signing_key.pem" ]; then
+ key_path="/lib/modules/$(uname -r)/source/certs/signing_key.pem"
+elif [ -f "/lib/modules/$(uname -r)/build/certs/signing_key.pem" ]; then
+ key_path="/lib/modules/$(uname -r)/build/certs/signing_key.pem"
+else
+ echo "${CYAN}Kernel signing key not found${NORM}"
+ exit "$SKIP"
+fi
+
+key_path_der=$(mktemp)
+
+openssl x509 -in "$key_path" -out "$key_path_der" -outform der
+if ! keyctl padd asymmetric pubkey %keyring:.ima < "$key_path_der" &> /dev/null; then
+ echo "${RED}Public key cannot be added to the IMA keyring${NORM}"
+ exit "$FAIL"
+fi
+
+g_mountpoint=$(mktemp -d)
+g_image=$(mktemp)
+
+if [ -z "$g_mountpoint" ]; then
+ echo "${RED}Mountpoint directory not created${NORM}"
+ exit "$FAIL"
+fi
+
+if ! dd if=/dev/zero of="$g_image" bs=1M count=20 &> /dev/null; then
+ echo "${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 "$FAIL"
+fi
+
+if ! mount -o i_version "$g_dev" "$g_mountpoint"; then
+ echo "${RED}Cannot mount loop device${NORM}"
+ exit "$FAIL"
+fi
+
+g_loop_mounted=1
+pushd "$g_mountpoint" > /dev/null || exit "$FAIL"
+
+expect_fail check_mmap "MMAP_CHECK" ""
+expect_pass check_mmap "MMAP_CHECK" "exec"
+expect_pass check_mmap "MMAP_CHECK" "read_implies_exec"
+
+expect_fail check_mmap "MMAP_CHECK_REQPROT" ""
+expect_pass check_mmap "MMAP_CHECK_REQPROT" "exec"
+expect_fail check_mmap "MMAP_CHECK_REQPROT" "read_implies_exec"
+
+expect_pass check_deny "MMAP_CHECK" "mprotect"
+expect_pass check_deny "MMAP_CHECK_REQPROT" "mprotect"
+
+expect_pass check_deny "MMAP_CHECK" "exec_on_writable"
+expect_pass check_deny "MMAP_CHECK_REQPROT" "exec_on_writable"
diff --git a/tests/test_mmap.c b/tests/test_mmap.c
new file mode 100644
index 000000000000..c9396f66b3a9
--- /dev/null
+++ b/tests/test_mmap.c
@@ -0,0 +1,69 @@
+#include <stdio.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <sys/personality.h>
+
+int main(int argc, char *argv[])
+{
+ struct stat st;
+ void *ptr, *ptr_write = NULL;
+ int ret, fd, fd_write, prot = PROT_READ;
+
+ if (!argv[1])
+ return -ENOENT;
+
+ if (argv[2] && !strcmp(argv[2], "read_implies_exec")) {
+ ret = personality(READ_IMPLIES_EXEC);
+ if (ret < 0)
+ return ret;
+ }
+
+ if (stat(argv[1], &st) == -1)
+ return -errno;
+
+ if (argv[2] && !strcmp(argv[2], "exec_on_writable")) {
+ fd_write = open(argv[1], O_RDWR);
+ if (fd_write == -1)
+ return -errno;
+
+ ptr_write = mmap(0, st.st_size, PROT_WRITE, MAP_SHARED,
+ fd_write, 0);
+ close(fd_write);
+
+ if (ptr_write == (void *)-1)
+ return -errno;
+ }
+
+ fd = open(argv[1], O_RDONLY);
+ if (fd == -1) {
+ if (ptr_write)
+ munmap(ptr_write, st.st_size);
+
+ return -errno;
+ }
+
+ if (argv[2] && !strncmp(argv[2], "exec", 4))
+ prot |= PROT_EXEC;
+
+ ptr = mmap(0, st.st_size, prot, MAP_PRIVATE, fd, 0);
+
+ close(fd);
+
+ if (ptr_write)
+ munmap(ptr_write, st.st_size);
+
+ if (ptr == (void *)-1)
+ return -errno;
+
+ ret = 0;
+
+ if (argv[2] && !strcmp(argv[2], "mprotect"))
+ ret = mprotect(ptr, st.st_size, PROT_EXEC);
+
+ munmap(ptr, st.st_size);
+ return ret;
+}
--
2.25.1
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