diff mbox series

[v6,6/8] selftests/brute: Add tests for the Brute LSM

Message ID 20210307113031.11671-7-john.wood@gmx.com (mailing list archive)
State New, archived
Headers show
Series Fork brute force attack mitigation | expand

Commit Message

John Wood March 7, 2021, 11:30 a.m. UTC 
Add tests to check the brute LSM functionality and cover fork/exec brute
force attacks crossing the following privilege boundaries:

1.- setuid process
2.- privilege changes
3.- network to local

Also, as a first step check that fork/exec brute force attacks without
crossing any privilege boundariy already commented doesn't trigger the
detection and mitigation stage.

All the fork brute force attacks are carried out via the "exec" app to
avoid the triggering of the "brute" LSM over the shell script running
the tests.

Signed-off-by: John Wood <john.wood@gmx.com>
---
 tools/testing/selftests/Makefile         |   1 +
 tools/testing/selftests/brute/.gitignore |   2 +
 tools/testing/selftests/brute/Makefile   |   5 +
 tools/testing/selftests/brute/config     |   1 +
 tools/testing/selftests/brute/exec.c     |  44 ++
 tools/testing/selftests/brute/test.c     | 507 +++++++++++++++++++++++
 tools/testing/selftests/brute/test.sh    | 226 ++++++++++
 7 files changed, 786 insertions(+)
 create mode 100644 tools/testing/selftests/brute/.gitignore
 create mode 100644 tools/testing/selftests/brute/Makefile
 create mode 100644 tools/testing/selftests/brute/config
 create mode 100644 tools/testing/selftests/brute/exec.c
 create mode 100644 tools/testing/selftests/brute/test.c
 create mode 100755 tools/testing/selftests/brute/test.sh

--
2.25.1

Comments

Kees Cook March 18, 2021, 4:08 a.m. UTC | #1 
On Sun, Mar 07, 2021 at 12:30:29PM +0100, John Wood wrote:
> Add tests to check the brute LSM functionality and cover fork/exec brute
> force attacks crossing the following privilege boundaries:
> 
> 1.- setuid process
> 2.- privilege changes
> 3.- network to local
> 
> Also, as a first step check that fork/exec brute force attacks without
> crossing any privilege boundariy already commented doesn't trigger the
> detection and mitigation stage.
> 
> All the fork brute force attacks are carried out via the "exec" app to
> avoid the triggering of the "brute" LSM over the shell script running
> the tests.
> 
> Signed-off-by: John Wood <john.wood@gmx.com>

Yay tests!

> ---
>  tools/testing/selftests/Makefile         |   1 +
>  tools/testing/selftests/brute/.gitignore |   2 +
>  tools/testing/selftests/brute/Makefile   |   5 +
>  tools/testing/selftests/brute/config     |   1 +
>  tools/testing/selftests/brute/exec.c     |  44 ++
>  tools/testing/selftests/brute/test.c     | 507 +++++++++++++++++++++++
>  tools/testing/selftests/brute/test.sh    | 226 ++++++++++
>  7 files changed, 786 insertions(+)
>  create mode 100644 tools/testing/selftests/brute/.gitignore
>  create mode 100644 tools/testing/selftests/brute/Makefile
>  create mode 100644 tools/testing/selftests/brute/config
>  create mode 100644 tools/testing/selftests/brute/exec.c
>  create mode 100644 tools/testing/selftests/brute/test.c
>  create mode 100755 tools/testing/selftests/brute/test.sh
> 
> diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
> index 6c575cf34a71..d4cf9e1c0a6d 100644
> --- a/tools/testing/selftests/Makefile
> +++ b/tools/testing/selftests/Makefile
> @@ -2,6 +2,7 @@
>  TARGETS = arm64
>  TARGETS += bpf
>  TARGETS += breakpoints
> +TARGETS += brute
>  TARGETS += capabilities
>  TARGETS += cgroup
>  TARGETS += clone3
> diff --git a/tools/testing/selftests/brute/.gitignore b/tools/testing/selftests/brute/.gitignore
> new file mode 100644
> index 000000000000..1ccc45251a1b
> --- /dev/null
> +++ b/tools/testing/selftests/brute/.gitignore
> @@ -0,0 +1,2 @@
> +exec
> +test
> diff --git a/tools/testing/selftests/brute/Makefile b/tools/testing/selftests/brute/Makefile
> new file mode 100644
> index 000000000000..52662d0b484c
> --- /dev/null
> +++ b/tools/testing/selftests/brute/Makefile
> @@ -0,0 +1,5 @@
> +# SPDX-License-Identifier: GPL-2.0
> +CFLAGS += -Wall -O2
> +TEST_PROGS := test.sh
> +TEST_GEN_FILES := exec test
> +include ../lib.mk
> diff --git a/tools/testing/selftests/brute/config b/tools/testing/selftests/brute/config
> new file mode 100644
> index 000000000000..3587b7bf6c23
> --- /dev/null
> +++ b/tools/testing/selftests/brute/config
> @@ -0,0 +1 @@
> +CONFIG_SECURITY_FORK_BRUTE=y
> diff --git a/tools/testing/selftests/brute/exec.c b/tools/testing/selftests/brute/exec.c
> new file mode 100644
> index 000000000000..1bbe72f6e4bd
> --- /dev/null
> +++ b/tools/testing/selftests/brute/exec.c
> @@ -0,0 +1,44 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <libgen.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +#include <unistd.h>
> +
> +static __attribute__((noreturn)) void error_failure(const char *message)
> +{
> +	perror(message);
> +	exit(EXIT_FAILURE);
> +}
> +
> +#define PROG_NAME basename(argv[0])
> +
> +int main(int argc, char **argv)
> +{
> +	pid_t pid;
> +	int status;
> +
> +	if (argc < 2) {
> +		printf("Usage: %s <EXECUTABLE>\n", PROG_NAME);
> +		exit(EXIT_FAILURE);
> +	}
> +
> +	pid = fork();
> +	if (pid < 0)
> +		error_failure("fork");
> +
> +	/* Child process */
> +	if (!pid) {
> +		execve(argv[1], &argv[1], NULL);
> +		error_failure("execve");
> +	}
> +
> +	/* Parent process */
> +	pid = waitpid(pid, &status, 0);
> +	if (pid < 0)
> +		error_failure("waitpid");
> +
> +	return EXIT_SUCCESS;
> +}
> diff --git a/tools/testing/selftests/brute/test.c b/tools/testing/selftests/brute/test.c
> new file mode 100644
> index 000000000000..44c32f446dca
> --- /dev/null
> +++ b/tools/testing/selftests/brute/test.c
> @@ -0,0 +1,507 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <arpa/inet.h>
> +#include <errno.h>
> +#include <libgen.h>
> +#include <pwd.h>
> +#include <signal.h>
> +#include <stdbool.h>
> +#include <stdint.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/socket.h>
> +#include <sys/time.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +#include <unistd.h>
> +
> +static const char *message = "message";
> +
> +enum mode {
> +	MODE_NONE,
> +	MODE_CRASH,
> +	MODE_SERVER_CRASH,
> +	MODE_CLIENT,
> +};
> +
> +enum crash_after {
> +	CRASH_AFTER_NONE,
> +	CRASH_AFTER_FORK,
> +	CRASH_AFTER_EXEC,
> +};
> +
> +enum signal_from {
> +	SIGNAL_FROM_NONE,
> +	SIGNAL_FROM_USER,
> +	SIGNAL_FROM_KERNEL,
> +};
> +
> +struct args {
> +	uint32_t ip;
> +	uint16_t port;
> +	int counter;
> +	long timeout;
> +	enum mode mode;
> +	enum crash_after crash_after;
> +	enum signal_from signal_from;
> +	unsigned char has_counter : 1;
> +	unsigned char has_change_priv : 1;
> +	unsigned char has_ip : 1;
> +	unsigned char has_port : 1;
> +	unsigned char has_timeout : 1;
> +};
> +
> +#define OPT_STRING "hm:c:s:n:Ca:p:t:"
> +
> +static void usage(const char *prog)
> +{
> +	printf("Usage: %s <OPTIONS>\n", prog);
> +	printf("OPTIONS:\n");
> +	printf("  -h: Show this help and exit. Optional.\n");
> +	printf("  -m (crash | server_crash | client): Mode. Required.\n");
> +	printf("Options for crash mode:\n");
> +	printf("  -c (fork | exec): Crash after. Optional.\n");
> +	printf("  -s (user | kernel): Signal from. Required.\n");
> +	printf("  -n counter: Number of crashes.\n");
> +	printf("              Required if the option -c is used.\n");
> +	printf("              Not used without the option -c.\n");
> +	printf("              Range from 1 to INT_MAX.\n");
> +	printf("  -C: Change privileges before crash. Optional.\n");
> +	printf("Options for server_crash mode:\n");
> +	printf("  -a ip: Ip v4 address to accept. Required.\n");
> +	printf("  -p port: Port number. Required.\n");
> +	printf("           Range from 1 to UINT16_MAX.\n");
> +	printf("  -t secs: Accept timeout. Required.\n");
> +	printf("           Range from 1 to LONG_MAX.\n");
> +	printf("  -c (fork | exec): Crash after. Required.\n");
> +	printf("  -s (user | kernel): Signal from. Required.\n");
> +	printf("  -n counter: Number of crashes. Required.\n");
> +	printf("              Range from 1 to INT_MAX.\n");
> +	printf("Options for client mode:\n");
> +	printf("  -a ip: Ip v4 address to connect. Required.\n");
> +	printf("  -p port: Port number. Required.\n");
> +	printf("           Range from 1 to UINT16_MAX.\n");
> +	printf("  -t secs: Connect timeout. Required.\n");
> +	printf("           Range from 1 to LONG_MAX.\n");
> +}
> +
> +static __attribute__((noreturn)) void info_failure(const char *message,
> +						   const char *prog)
> +{
> +	printf("%s\n", message);
> +	usage(prog);
> +	exit(EXIT_FAILURE);
> +}
> +
> +static enum mode get_mode(const char *text, const char *prog)
> +{
> +	if (!strcmp(text, "crash"))
> +		return MODE_CRASH;
> +
> +	if (!strcmp(text, "server_crash"))
> +		return MODE_SERVER_CRASH;
> +
> +	if (!strcmp(text, "client"))
> +		return MODE_CLIENT;
> +
> +	info_failure("Invalid mode option [-m].", prog);
> +}
> +
> +static enum crash_after get_crash_after(const char *text, const char *prog)
> +{
> +	if (!strcmp(text, "fork"))
> +		return CRASH_AFTER_FORK;
> +
> +	if (!strcmp(text, "exec"))
> +		return CRASH_AFTER_EXEC;
> +
> +	info_failure("Invalid crash after option [-c].", prog);
> +}
> +
> +static enum signal_from get_signal_from(const char *text, const char *prog)
> +{
> +	if (!strcmp(text, "user"))
> +		return SIGNAL_FROM_USER;
> +
> +	if (!strcmp(text, "kernel"))
> +		return SIGNAL_FROM_KERNEL;
> +
> +	info_failure("Invalid signal from option [-s]", prog);
> +}
> +
> +static int get_counter(const char *text, const char *prog)
> +{
> +	int counter;
> +
> +	counter = atoi(text);
> +	if (counter > 0)
> +		return counter;
> +
> +	info_failure("Invalid counter option [-n].", prog);
> +}
> +
> +static __attribute__((noreturn)) void error_failure(const char *message)
> +{
> +	perror(message);
> +	exit(EXIT_FAILURE);
> +}
> +
> +static uint32_t get_ip(const char *text, const char *prog)
> +{
> +	int ret;
> +	uint32_t ip;
> +
> +	ret = inet_pton(AF_INET, text, &ip);
> +	if (!ret)
> +		info_failure("Invalid ip option [-a].", prog);
> +	else if (ret < 0)
> +		error_failure("inet_pton");
> +
> +	return ip;
> +}
> +
> +static uint16_t get_port(const char *text, const char *prog)
> +{
> +	long port;
> +
> +	port = atol(text);
> +	if ((port > 0) && (port <= UINT16_MAX))
> +		return htons(port);
> +
> +	info_failure("Invalid port option [-p].", prog);
> +}
> +
> +static long get_timeout(const char *text, const char *prog)
> +{
> +	long timeout;
> +
> +	timeout = atol(text);
> +	if (timeout > 0)
> +		return timeout;
> +
> +	info_failure("Invalid timeout option [-t].", prog);
> +}
> +
> +static void check_args(const struct args *args, const char *prog)
> +{
> +	if (args->mode == MODE_CRASH && args->crash_after != CRASH_AFTER_NONE &&
> +	    args->signal_from != SIGNAL_FROM_NONE && args->has_counter &&
> +	    !args->has_ip && !args->has_port && !args->has_timeout)
> +		return;
> +
> +	if (args->mode == MODE_CRASH && args->signal_from != SIGNAL_FROM_NONE &&
> +	    args->crash_after == CRASH_AFTER_NONE && !args->has_counter &&
> +	    !args->has_ip && !args->has_port && !args->has_timeout)
> +		return;
> +
> +	if (args->mode == MODE_SERVER_CRASH && args->has_ip && args->has_port &&
> +	    args->has_timeout && args->crash_after != CRASH_AFTER_NONE &&
> +	    args->signal_from != SIGNAL_FROM_NONE && args->has_counter &&
> +	    !args->has_change_priv)
> +		return;
> +
> +	if (args->mode == MODE_CLIENT && args->has_ip && args->has_port &&
> +	    args->has_timeout && args->crash_after == CRASH_AFTER_NONE &&
> +	    args->signal_from == SIGNAL_FROM_NONE && !args->has_counter &&
> +	    !args->has_change_priv)
> +		return;
> +
> +	info_failure("Invalid use of options.", prog);
> +}
> +
> +static uid_t get_non_root_uid(void)
> +{
> +	struct passwd *pwent;
> +	uid_t uid;
> +
> +	while (true) {
> +		errno = 0;
> +		pwent = getpwent();
> +		if (!pwent) {
> +			if (errno) {
> +				perror("getpwent");
> +				endpwent();
> +				exit(EXIT_FAILURE);
> +			}
> +			break;
> +		}
> +
> +		if (pwent->pw_uid) {
> +			uid = pwent->pw_uid;
> +			endpwent();
> +			return uid;
> +		}
> +	}
> +
> +	endpwent();
> +	printf("A user different of root is needed.\n");
> +	exit(EXIT_FAILURE);
> +}
> +
> +static inline void do_sigsegv(void)
> +{
> +	int *p = NULL;
> +	*p = 0;
> +}
> +
> +static void do_sigkill(void)
> +{
> +	int ret;
> +
> +	ret = kill(getpid(), SIGKILL);
> +	if (ret)
> +		error_failure("kill");
> +}
> +
> +static void crash(enum signal_from signal_from, bool change_priv)
> +{
> +	int ret;
> +
> +	if (change_priv) {
> +		ret = setuid(get_non_root_uid());
> +		if (ret)
> +			error_failure("setuid");
> +	}
> +
> +	if (signal_from == SIGNAL_FROM_KERNEL)
> +		do_sigsegv();
> +
> +	do_sigkill();
> +}
> +
> +static void execve_crash(char *const argv[])
> +{
> +	execve(argv[0], argv, NULL);
> +	error_failure("execve");
> +}
> +
> +static void exec_crash_user(void)
> +{
> +	char *const argv[] = {
> +		"./test", "-m", "crash", "-s", "user", NULL,
> +	};
> +
> +	execve_crash(argv);
> +}
> +
> +static void exec_crash_user_change_priv(void)
> +{
> +	char *const argv[] = {
> +		"./test", "-m", "crash", "-s", "user", "-C", NULL,
> +	};
> +
> +	execve_crash(argv);
> +}
> +
> +static void exec_crash_kernel(void)
> +{
> +	char *const argv[] = {
> +		"./test", "-m", "crash", "-s", "kernel", NULL,
> +	};
> +
> +	execve_crash(argv);
> +}
> +
> +static void exec_crash_kernel_change_priv(void)
> +{
> +	char *const argv[] = {
> +		"./test", "-m", "crash", "-s", "kernel", "-C", NULL,
> +	};
> +
> +	execve_crash(argv);
> +}
> +
> +static void exec_crash(enum signal_from signal_from, bool change_priv)
> +{
> +	if (signal_from == SIGNAL_FROM_USER && !change_priv)
> +		exec_crash_user();
> +	if (signal_from == SIGNAL_FROM_USER && change_priv)
> +		exec_crash_user_change_priv();
> +	if (signal_from == SIGNAL_FROM_KERNEL && !change_priv)
> +		exec_crash_kernel();
> +	if (signal_from == SIGNAL_FROM_KERNEL && change_priv)
> +		exec_crash_kernel_change_priv();
> +}
> +
> +static void do_crash(enum crash_after crash_after, enum signal_from signal_from,
> +		     int counter, bool change_priv)
> +{
> +	pid_t pid;
> +	int status;
> +
> +	if (crash_after == CRASH_AFTER_NONE)
> +		crash(signal_from, change_priv);
> +
> +	while (counter > 0) {
> +		pid = fork();
> +		if (pid < 0)
> +			error_failure("fork");
> +
> +		/* Child process */
> +		if (!pid) {
> +			if (crash_after == CRASH_AFTER_FORK)
> +				crash(signal_from, change_priv);
> +
> +			exec_crash(signal_from, change_priv);
> +		}
> +
> +		/* Parent process */
> +		counter -= 1;
> +		pid = waitpid(pid, &status, 0);
> +		if (pid < 0)
> +			error_failure("waitpid");
> +	}
> +}
> +
> +static __attribute__((noreturn)) void error_close_failure(const char *message,
> +							  int fd)
> +{
> +	perror(message);
> +	close(fd);
> +	exit(EXIT_FAILURE);
> +}
> +
> +static void do_server(uint32_t ip, uint16_t port, long accept_timeout)
> +{
> +	int sockfd;
> +	int ret;
> +	struct sockaddr_in address;
> +	struct timeval timeout;
> +	int newsockfd;
> +
> +	sockfd = socket(AF_INET, SOCK_STREAM, 0);
> +	if (sockfd < 0)
> +		error_failure("socket");
> +
> +	address.sin_family = AF_INET;
> +	address.sin_addr.s_addr = ip;
> +	address.sin_port = port;
> +
> +	ret = bind(sockfd, (const struct sockaddr *)&address, sizeof(address));
> +	if (ret)
> +		error_close_failure("bind", sockfd);
> +
> +	ret = listen(sockfd, 1);
> +	if (ret)
> +		error_close_failure("listen", sockfd);
> +
> +	timeout.tv_sec = accept_timeout;
> +	timeout.tv_usec = 0;
> +	ret = setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO,
> +			 (const struct timeval *)&timeout, sizeof(timeout));
> +	if (ret)
> +		error_close_failure("setsockopt", sockfd);
> +
> +	newsockfd = accept(sockfd, NULL, NULL);
> +	if (newsockfd < 0)
> +		error_close_failure("accept", sockfd);
> +
> +	close(sockfd);
> +	close(newsockfd);
> +}
> +
> +static void do_client(uint32_t ip, uint16_t port, long connect_timeout)
> +{
> +	int sockfd;
> +	int ret;
> +	struct timeval timeout;
> +	struct sockaddr_in address;
> +
> +	sockfd = socket(AF_INET, SOCK_STREAM, 0);
> +	if (sockfd < 0)
> +		error_failure("socket");
> +
> +	timeout.tv_sec = connect_timeout;
> +	timeout.tv_usec = 0;
> +	ret = setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO,
> +			 (const struct timeval *)&timeout, sizeof(timeout));
> +	if (ret)
> +		error_close_failure("setsockopt", sockfd);
> +
> +	address.sin_family = AF_INET;
> +	address.sin_addr.s_addr = ip;
> +	address.sin_port = port;
> +
> +	ret = connect(sockfd, (const struct sockaddr *)&address,
> +		      sizeof(address));
> +	if (ret)
> +		error_close_failure("connect", sockfd);
> +
> +	ret = write(sockfd, message, strlen(message));
> +	if (ret < 0)
> +		error_close_failure("write", sockfd);
> +
> +	close(sockfd);
> +}
> +
> +#define PROG_NAME basename(argv[0])
> +
> +int main(int argc, char **argv)
> +{
> +	int opt;
> +	struct args args = {
> +		.mode = MODE_NONE,
> +		.crash_after = CRASH_AFTER_NONE,
> +		.signal_from = SIGNAL_FROM_NONE,
> +		.has_counter = false,
> +		.has_change_priv = false,
> +		.has_ip = false,
> +		.has_port = false,
> +		.has_timeout = false,
> +	};
> +
> +	while ((opt = getopt(argc, argv, OPT_STRING)) != -1) {
> +		switch (opt) {
> +		case 'h':
> +			usage(PROG_NAME);
> +			return EXIT_SUCCESS;
> +		case 'm':
> +			args.mode = get_mode(optarg, PROG_NAME);
> +			break;
> +		case 'c':
> +			args.crash_after = get_crash_after(optarg, PROG_NAME);
> +			break;
> +		case 's':
> +			args.signal_from = get_signal_from(optarg, PROG_NAME);
> +			break;
> +		case 'n':
> +			args.counter = get_counter(optarg, PROG_NAME);
> +			args.has_counter = true;
> +			break;
> +		case 'C':
> +			args.has_change_priv = true;
> +			break;
> +		case 'a':
> +			args.ip = get_ip(optarg, PROG_NAME);
> +			args.has_ip = true;
> +			break;
> +		case 'p':
> +			args.port = get_port(optarg, PROG_NAME);
> +			args.has_port = true;
> +			break;
> +		case 't':
> +			args.timeout = get_timeout(optarg, PROG_NAME);
> +			args.has_timeout = true;
> +			break;
> +		default:
> +			usage(PROG_NAME);
> +			return EXIT_FAILURE;
> +		}
> +	}
> +
> +	check_args(&args, PROG_NAME);
> +
> +	if (args.mode == MODE_CRASH) {
> +		do_crash(args.crash_after, args.signal_from, args.counter,
> +			 args.has_change_priv);
> +	} else if (args.mode == MODE_SERVER_CRASH) {
> +		do_server(args.ip, args.port, args.timeout);
> +		do_crash(args.crash_after, args.signal_from, args.counter,
> +			 false);
> +	} else if (args.mode == MODE_CLIENT) {
> +		do_client(args.ip, args.port, args.timeout);
> +	}
> +
> +	return EXIT_SUCCESS;
> +}
> diff --git a/tools/testing/selftests/brute/test.sh b/tools/testing/selftests/brute/test.sh
> new file mode 100755
> index 000000000000..f53f26ae5b96
> --- /dev/null
> +++ b/tools/testing/selftests/brute/test.sh
> @@ -0,0 +1,226 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +
> +TCID="test.sh"
> +
> +KSFT_PASS=0
> +KSFT_FAIL=1
> +KSFT_SKIP=4
> +
> +errno=$KSFT_PASS
> +
> +check_root()
> +{
> +	local uid=$(id -u)
> +	if [ $uid -ne 0 ]; then
> +		echo $TCID: must be run as root >&2
> +		exit $KSFT_SKIP
> +	fi
> +}
> +
> +count_fork_matches()
> +{
> +	dmesg | grep "brute: Fork brute force attack detected" | wc -l

This may be unstable if the dmesg scrolls past, etc. See how
lkdtm/run.sh handles this with a temp file and "comm".

> +}
> +
> +assert_equal()
> +{
> +	local val1=$1
> +	local val2=$2
> +
> +	if [ $val1 -eq $val2 ]; then
> +		echo "$TCID: $message [PASS]"
> +	else
> +		echo "$TCID: $message [FAIL]"
> +		errno=$KSFT_FAIL
> +	fi
> +}
> +
> +test_fork_user()
> +{
> +	COUNTER=20
> +
> +	old_count=$(count_fork_matches)
> +	./exec test -m crash -c fork -s user -n $COUNTER
> +	new_count=$(count_fork_matches)
> +
> +	message="Fork attack (user signals, no bounds crossed)"
> +	assert_equal $old_count $new_count
> +}
> +
> +test_fork_kernel()
> +{
> +	old_count=$(count_fork_matches)
> +	./exec test -m crash -c fork -s kernel -n $COUNTER
> +	new_count=$(count_fork_matches)
> +
> +	message="Fork attack (kernel signals, no bounds crossed)"
> +	assert_equal $old_count $new_count
> +}
> +
> +count_exec_matches()
> +{
> +	dmesg | grep "brute: Exec brute force attack detected" | wc -l
> +}
> +
> +test_exec_user()
> +{
> +	old_count=$(count_exec_matches)
> +	./test -m crash -c exec -s user -n $COUNTER
> +	new_count=$(count_exec_matches)
> +
> +	message="Exec attack (user signals, no bounds crossed)"
> +	assert_equal $old_count $new_count
> +}
> +
> +test_exec_kernel()
> +{
> +	old_count=$(count_exec_matches)
> +	./test -m crash -c exec -s kernel -n $COUNTER
> +	new_count=$(count_exec_matches)
> +
> +	message="Exec attack (kernel signals, no bounds crossed)"
> +	assert_equal $old_count $new_count
> +}
> +
> +assert_not_equal()
> +{
> +	local val1=$1
> +	local val2=$2
> +
> +	if [ $val1 -ne $val2 ]; then
> +		echo $TCID: $message [PASS]
> +	else
> +		echo $TCID: $message [FAIL]
> +		errno=$KSFT_FAIL
> +	fi
> +}
> +
> +test_fork_kernel_setuid()
> +{
> +	old_count=$(count_fork_matches)
> +	chmod u+s test
> +	./exec test -m crash -c fork -s kernel -n $COUNTER
> +	chmod u-s test
> +	new_count=$(count_fork_matches)
> +
> +	message="Fork attack (kernel signals, setuid binary)"
> +	assert_not_equal $old_count $new_count
> +}
> +
> +test_exec_kernel_setuid()
> +{
> +	old_count=$(count_exec_matches)
> +	chmod u+s test
> +	./test -m crash -c exec -s kernel -n $COUNTER
> +	chmod u-s test
> +	new_count=$(count_exec_matches)
> +
> +	message="Exec attack (kernel signals, setuid binary)"
> +	assert_not_equal $old_count $new_count
> +}
> +
> +test_fork_kernel_change_priv()
> +{
> +	old_count=$(count_fork_matches)
> +	./exec test -m crash -c fork -s kernel -n $COUNTER -C
> +	new_count=$(count_fork_matches)
> +
> +	message="Fork attack (kernel signals, change privileges)"
> +	assert_not_equal $old_count $new_count
> +}
> +
> +test_exec_kernel_change_priv()
> +{
> +	old_count=$(count_exec_matches)
> +	./test -m crash -c exec -s kernel -n $COUNTER -C
> +	new_count=$(count_exec_matches)
> +
> +	message="Exec attack (kernel signals, change privileges)"
> +	assert_not_equal $old_count $new_count
> +}
> +
> +network_ns_setup()
> +{
> +	local vnet_name=$1
> +	local veth_name=$2
> +	local ip_src=$3
> +	local ip_dst=$4
> +
> +	ip netns add $vnet_name
> +	ip link set $veth_name netns $vnet_name
> +	ip -n $vnet_name addr add $ip_src/24 dev $veth_name
> +	ip -n $vnet_name link set $veth_name up
> +	ip -n $vnet_name route add $ip_dst/24 dev $veth_name
> +}
> +
> +network_setup()
> +{
> +	VETH0_NAME=veth0
> +	VNET0_NAME=vnet0
> +	VNET0_IP=10.0.1.0
> +	VETH1_NAME=veth1
> +	VNET1_NAME=vnet1
> +	VNET1_IP=10.0.2.0
> +
> +	ip link add $VETH0_NAME type veth peer name $VETH1_NAME
> +	network_ns_setup $VNET0_NAME $VETH0_NAME $VNET0_IP $VNET1_IP
> +	network_ns_setup $VNET1_NAME $VETH1_NAME $VNET1_IP $VNET0_IP
> +}
> +
> +test_fork_kernel_network_to_local()
> +{
> +	INADDR_ANY=0.0.0.0
> +	PORT=65535
> +	TIMEOUT=5
> +
> +	old_count=$(count_fork_matches)
> +	ip netns exec $VNET0_NAME ./exec test -m server_crash -a $INADDR_ANY \
> +		-p $PORT -t $TIMEOUT -c fork -s kernel -n $COUNTER &
> +	sleep 1
> +	ip netns exec $VNET1_NAME ./test -m client -a $VNET0_IP -p $PORT \
> +		-t $TIMEOUT
> +	sleep 1
> +	new_count=$(count_fork_matches)
> +
> +	message="Fork attack (kernel signals, network to local)"
> +	assert_not_equal $old_count $new_count
> +}
> +
> +test_exec_kernel_network_to_local()
> +{
> +	old_count=$(count_exec_matches)
> +	ip netns exec $VNET0_NAME ./test -m server_crash -a $INADDR_ANY \
> +		-p $PORT -t $TIMEOUT -c exec -s kernel -n $COUNTER &
> +	sleep 1
> +	ip netns exec $VNET1_NAME ./test -m client -a $VNET0_IP -p $PORT \
> +		-t $TIMEOUT
> +	sleep 1
> +	new_count=$(count_exec_matches)
> +
> +	message="Exec attack (kernel signals, network to local)"
> +	assert_not_equal $old_count $new_count
> +}
> +
> +network_cleanup()
> +{
> +	ip netns del $VNET0_NAME >/dev/null 2>&1
> +	ip netns del $VNET1_NAME >/dev/null 2>&1
> +	ip link delete $VETH0_NAME >/dev/null 2>&1
> +	ip link delete $VETH1_NAME >/dev/null 2>&1
> +}
> +
> +check_root
> +test_fork_user
> +test_fork_kernel
> +test_exec_user
> +test_exec_kernel
> +test_fork_kernel_setuid
> +test_exec_kernel_setuid
> +test_fork_kernel_change_priv
> +test_exec_kernel_change_priv
> +network_setup
> +test_fork_kernel_network_to_local
> +test_exec_kernel_network_to_local
> +network_cleanup
> +exit $errno
> --
> 2.25.1
>
John Wood March 20, 2021, 3:49 p.m. UTC | #2 
On Wed, Mar 17, 2021 at 09:08:17PM -0700, Kees Cook wrote:
> On Sun, Mar 07, 2021 at 12:30:29PM +0100, John Wood wrote:
> > +
> > +count_fork_matches()
> > +{
> > +	dmesg | grep "brute: Fork brute force attack detected" | wc -l
>
> This may be unstable if the dmesg scrolls past, etc. See how
> lkdtm/run.sh handles this with a temp file and "comm".

Thanks, I will correct this for the next version.

John Wood
diff mbox series

Patch

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 6c575cf34a71..d4cf9e1c0a6d 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -2,6 +2,7 @@ 
 TARGETS = arm64
 TARGETS += bpf
 TARGETS += breakpoints
+TARGETS += brute
 TARGETS += capabilities
 TARGETS += cgroup
 TARGETS += clone3
diff --git a/tools/testing/selftests/brute/.gitignore b/tools/testing/selftests/brute/.gitignore
new file mode 100644
index 000000000000..1ccc45251a1b
--- /dev/null
+++ b/tools/testing/selftests/brute/.gitignore
@@ -0,0 +1,2 @@ 
+exec
+test
diff --git a/tools/testing/selftests/brute/Makefile b/tools/testing/selftests/brute/Makefile
new file mode 100644
index 000000000000..52662d0b484c
--- /dev/null
+++ b/tools/testing/selftests/brute/Makefile
@@ -0,0 +1,5 @@ 
+# SPDX-License-Identifier: GPL-2.0
+CFLAGS += -Wall -O2
+TEST_PROGS := test.sh
+TEST_GEN_FILES := exec test
+include ../lib.mk
diff --git a/tools/testing/selftests/brute/config b/tools/testing/selftests/brute/config
new file mode 100644
index 000000000000..3587b7bf6c23
--- /dev/null
+++ b/tools/testing/selftests/brute/config
@@ -0,0 +1 @@ 
+CONFIG_SECURITY_FORK_BRUTE=y
diff --git a/tools/testing/selftests/brute/exec.c b/tools/testing/selftests/brute/exec.c
new file mode 100644
index 000000000000..1bbe72f6e4bd
--- /dev/null
+++ b/tools/testing/selftests/brute/exec.c
@@ -0,0 +1,44 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <libgen.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static __attribute__((noreturn)) void error_failure(const char *message)
+{
+	perror(message);
+	exit(EXIT_FAILURE);
+}
+
+#define PROG_NAME basename(argv[0])
+
+int main(int argc, char **argv)
+{
+	pid_t pid;
+	int status;
+
+	if (argc < 2) {
+		printf("Usage: %s <EXECUTABLE>\n", PROG_NAME);
+		exit(EXIT_FAILURE);
+	}
+
+	pid = fork();
+	if (pid < 0)
+		error_failure("fork");
+
+	/* Child process */
+	if (!pid) {
+		execve(argv[1], &argv[1], NULL);
+		error_failure("execve");
+	}
+
+	/* Parent process */
+	pid = waitpid(pid, &status, 0);
+	if (pid < 0)
+		error_failure("waitpid");
+
+	return EXIT_SUCCESS;
+}
diff --git a/tools/testing/selftests/brute/test.c b/tools/testing/selftests/brute/test.c
new file mode 100644
index 000000000000..44c32f446dca
--- /dev/null
+++ b/tools/testing/selftests/brute/test.c
@@ -0,0 +1,507 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <libgen.h>
+#include <pwd.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static const char *message = "message";
+
+enum mode {
+	MODE_NONE,
+	MODE_CRASH,
+	MODE_SERVER_CRASH,
+	MODE_CLIENT,
+};
+
+enum crash_after {
+	CRASH_AFTER_NONE,
+	CRASH_AFTER_FORK,
+	CRASH_AFTER_EXEC,
+};
+
+enum signal_from {
+	SIGNAL_FROM_NONE,
+	SIGNAL_FROM_USER,
+	SIGNAL_FROM_KERNEL,
+};
+
+struct args {
+	uint32_t ip;
+	uint16_t port;
+	int counter;
+	long timeout;
+	enum mode mode;
+	enum crash_after crash_after;
+	enum signal_from signal_from;
+	unsigned char has_counter : 1;
+	unsigned char has_change_priv : 1;
+	unsigned char has_ip : 1;
+	unsigned char has_port : 1;
+	unsigned char has_timeout : 1;
+};
+
+#define OPT_STRING "hm:c:s:n:Ca:p:t:"
+
+static void usage(const char *prog)
+{
+	printf("Usage: %s <OPTIONS>\n", prog);
+	printf("OPTIONS:\n");
+	printf("  -h: Show this help and exit. Optional.\n");
+	printf("  -m (crash | server_crash | client): Mode. Required.\n");
+	printf("Options for crash mode:\n");
+	printf("  -c (fork | exec): Crash after. Optional.\n");
+	printf("  -s (user | kernel): Signal from. Required.\n");
+	printf("  -n counter: Number of crashes.\n");
+	printf("              Required if the option -c is used.\n");
+	printf("              Not used without the option -c.\n");
+	printf("              Range from 1 to INT_MAX.\n");
+	printf("  -C: Change privileges before crash. Optional.\n");
+	printf("Options for server_crash mode:\n");
+	printf("  -a ip: Ip v4 address to accept. Required.\n");
+	printf("  -p port: Port number. Required.\n");
+	printf("           Range from 1 to UINT16_MAX.\n");
+	printf("  -t secs: Accept timeout. Required.\n");
+	printf("           Range from 1 to LONG_MAX.\n");
+	printf("  -c (fork | exec): Crash after. Required.\n");
+	printf("  -s (user | kernel): Signal from. Required.\n");
+	printf("  -n counter: Number of crashes. Required.\n");
+	printf("              Range from 1 to INT_MAX.\n");
+	printf("Options for client mode:\n");
+	printf("  -a ip: Ip v4 address to connect. Required.\n");
+	printf("  -p port: Port number. Required.\n");
+	printf("           Range from 1 to UINT16_MAX.\n");
+	printf("  -t secs: Connect timeout. Required.\n");
+	printf("           Range from 1 to LONG_MAX.\n");
+}
+
+static __attribute__((noreturn)) void info_failure(const char *message,
+						   const char *prog)
+{
+	printf("%s\n", message);
+	usage(prog);
+	exit(EXIT_FAILURE);
+}
+
+static enum mode get_mode(const char *text, const char *prog)
+{
+	if (!strcmp(text, "crash"))
+		return MODE_CRASH;
+
+	if (!strcmp(text, "server_crash"))
+		return MODE_SERVER_CRASH;
+
+	if (!strcmp(text, "client"))
+		return MODE_CLIENT;
+
+	info_failure("Invalid mode option [-m].", prog);
+}
+
+static enum crash_after get_crash_after(const char *text, const char *prog)
+{
+	if (!strcmp(text, "fork"))
+		return CRASH_AFTER_FORK;
+
+	if (!strcmp(text, "exec"))
+		return CRASH_AFTER_EXEC;
+
+	info_failure("Invalid crash after option [-c].", prog);
+}
+
+static enum signal_from get_signal_from(const char *text, const char *prog)
+{
+	if (!strcmp(text, "user"))
+		return SIGNAL_FROM_USER;
+
+	if (!strcmp(text, "kernel"))
+		return SIGNAL_FROM_KERNEL;
+
+	info_failure("Invalid signal from option [-s]", prog);
+}
+
+static int get_counter(const char *text, const char *prog)
+{
+	int counter;
+
+	counter = atoi(text);
+	if (counter > 0)
+		return counter;
+
+	info_failure("Invalid counter option [-n].", prog);
+}
+
+static __attribute__((noreturn)) void error_failure(const char *message)
+{
+	perror(message);
+	exit(EXIT_FAILURE);
+}
+
+static uint32_t get_ip(const char *text, const char *prog)
+{
+	int ret;
+	uint32_t ip;
+
+	ret = inet_pton(AF_INET, text, &ip);
+	if (!ret)
+		info_failure("Invalid ip option [-a].", prog);
+	else if (ret < 0)
+		error_failure("inet_pton");
+
+	return ip;
+}
+
+static uint16_t get_port(const char *text, const char *prog)
+{
+	long port;
+
+	port = atol(text);
+	if ((port > 0) && (port <= UINT16_MAX))
+		return htons(port);
+
+	info_failure("Invalid port option [-p].", prog);
+}
+
+static long get_timeout(const char *text, const char *prog)
+{
+	long timeout;
+
+	timeout = atol(text);
+	if (timeout > 0)
+		return timeout;
+
+	info_failure("Invalid timeout option [-t].", prog);
+}
+
+static void check_args(const struct args *args, const char *prog)
+{
+	if (args->mode == MODE_CRASH && args->crash_after != CRASH_AFTER_NONE &&
+	    args->signal_from != SIGNAL_FROM_NONE && args->has_counter &&
+	    !args->has_ip && !args->has_port && !args->has_timeout)
+		return;
+
+	if (args->mode == MODE_CRASH && args->signal_from != SIGNAL_FROM_NONE &&
+	    args->crash_after == CRASH_AFTER_NONE && !args->has_counter &&
+	    !args->has_ip && !args->has_port && !args->has_timeout)
+		return;
+
+	if (args->mode == MODE_SERVER_CRASH && args->has_ip && args->has_port &&
+	    args->has_timeout && args->crash_after != CRASH_AFTER_NONE &&
+	    args->signal_from != SIGNAL_FROM_NONE && args->has_counter &&
+	    !args->has_change_priv)
+		return;
+
+	if (args->mode == MODE_CLIENT && args->has_ip && args->has_port &&
+	    args->has_timeout && args->crash_after == CRASH_AFTER_NONE &&
+	    args->signal_from == SIGNAL_FROM_NONE && !args->has_counter &&
+	    !args->has_change_priv)
+		return;
+
+	info_failure("Invalid use of options.", prog);
+}
+
+static uid_t get_non_root_uid(void)
+{
+	struct passwd *pwent;
+	uid_t uid;
+
+	while (true) {
+		errno = 0;
+		pwent = getpwent();
+		if (!pwent) {
+			if (errno) {
+				perror("getpwent");
+				endpwent();
+				exit(EXIT_FAILURE);
+			}
+			break;
+		}
+
+		if (pwent->pw_uid) {
+			uid = pwent->pw_uid;
+			endpwent();
+			return uid;
+		}
+	}
+
+	endpwent();
+	printf("A user different of root is needed.\n");
+	exit(EXIT_FAILURE);
+}
+
+static inline void do_sigsegv(void)
+{
+	int *p = NULL;
+	*p = 0;
+}
+
+static void do_sigkill(void)
+{
+	int ret;
+
+	ret = kill(getpid(), SIGKILL);
+	if (ret)
+		error_failure("kill");
+}
+
+static void crash(enum signal_from signal_from, bool change_priv)
+{
+	int ret;
+
+	if (change_priv) {
+		ret = setuid(get_non_root_uid());
+		if (ret)
+			error_failure("setuid");
+	}
+
+	if (signal_from == SIGNAL_FROM_KERNEL)
+		do_sigsegv();
+
+	do_sigkill();
+}
+
+static void execve_crash(char *const argv[])
+{
+	execve(argv[0], argv, NULL);
+	error_failure("execve");
+}
+
+static void exec_crash_user(void)
+{
+	char *const argv[] = {
+		"./test", "-m", "crash", "-s", "user", NULL,
+	};
+
+	execve_crash(argv);
+}
+
+static void exec_crash_user_change_priv(void)
+{
+	char *const argv[] = {
+		"./test", "-m", "crash", "-s", "user", "-C", NULL,
+	};
+
+	execve_crash(argv);
+}
+
+static void exec_crash_kernel(void)
+{
+	char *const argv[] = {
+		"./test", "-m", "crash", "-s", "kernel", NULL,
+	};
+
+	execve_crash(argv);
+}
+
+static void exec_crash_kernel_change_priv(void)
+{
+	char *const argv[] = {
+		"./test", "-m", "crash", "-s", "kernel", "-C", NULL,
+	};
+
+	execve_crash(argv);
+}
+
+static void exec_crash(enum signal_from signal_from, bool change_priv)
+{
+	if (signal_from == SIGNAL_FROM_USER && !change_priv)
+		exec_crash_user();
+	if (signal_from == SIGNAL_FROM_USER && change_priv)
+		exec_crash_user_change_priv();
+	if (signal_from == SIGNAL_FROM_KERNEL && !change_priv)
+		exec_crash_kernel();
+	if (signal_from == SIGNAL_FROM_KERNEL && change_priv)
+		exec_crash_kernel_change_priv();
+}
+
+static void do_crash(enum crash_after crash_after, enum signal_from signal_from,
+		     int counter, bool change_priv)
+{
+	pid_t pid;
+	int status;
+
+	if (crash_after == CRASH_AFTER_NONE)
+		crash(signal_from, change_priv);
+
+	while (counter > 0) {
+		pid = fork();
+		if (pid < 0)
+			error_failure("fork");
+
+		/* Child process */
+		if (!pid) {
+			if (crash_after == CRASH_AFTER_FORK)
+				crash(signal_from, change_priv);
+
+			exec_crash(signal_from, change_priv);
+		}
+
+		/* Parent process */
+		counter -= 1;
+		pid = waitpid(pid, &status, 0);
+		if (pid < 0)
+			error_failure("waitpid");
+	}
+}
+
+static __attribute__((noreturn)) void error_close_failure(const char *message,
+							  int fd)
+{
+	perror(message);
+	close(fd);
+	exit(EXIT_FAILURE);
+}
+
+static void do_server(uint32_t ip, uint16_t port, long accept_timeout)
+{
+	int sockfd;
+	int ret;
+	struct sockaddr_in address;
+	struct timeval timeout;
+	int newsockfd;
+
+	sockfd = socket(AF_INET, SOCK_STREAM, 0);
+	if (sockfd < 0)
+		error_failure("socket");
+
+	address.sin_family = AF_INET;
+	address.sin_addr.s_addr = ip;
+	address.sin_port = port;
+
+	ret = bind(sockfd, (const struct sockaddr *)&address, sizeof(address));
+	if (ret)
+		error_close_failure("bind", sockfd);
+
+	ret = listen(sockfd, 1);
+	if (ret)
+		error_close_failure("listen", sockfd);
+
+	timeout.tv_sec = accept_timeout;
+	timeout.tv_usec = 0;
+	ret = setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO,
+			 (const struct timeval *)&timeout, sizeof(timeout));
+	if (ret)
+		error_close_failure("setsockopt", sockfd);
+
+	newsockfd = accept(sockfd, NULL, NULL);
+	if (newsockfd < 0)
+		error_close_failure("accept", sockfd);
+
+	close(sockfd);
+	close(newsockfd);
+}
+
+static void do_client(uint32_t ip, uint16_t port, long connect_timeout)
+{
+	int sockfd;
+	int ret;
+	struct timeval timeout;
+	struct sockaddr_in address;
+
+	sockfd = socket(AF_INET, SOCK_STREAM, 0);
+	if (sockfd < 0)
+		error_failure("socket");
+
+	timeout.tv_sec = connect_timeout;
+	timeout.tv_usec = 0;
+	ret = setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO,
+			 (const struct timeval *)&timeout, sizeof(timeout));
+	if (ret)
+		error_close_failure("setsockopt", sockfd);
+
+	address.sin_family = AF_INET;
+	address.sin_addr.s_addr = ip;
+	address.sin_port = port;
+
+	ret = connect(sockfd, (const struct sockaddr *)&address,
+		      sizeof(address));
+	if (ret)
+		error_close_failure("connect", sockfd);
+
+	ret = write(sockfd, message, strlen(message));
+	if (ret < 0)
+		error_close_failure("write", sockfd);
+
+	close(sockfd);
+}
+
+#define PROG_NAME basename(argv[0])
+
+int main(int argc, char **argv)
+{
+	int opt;
+	struct args args = {
+		.mode = MODE_NONE,
+		.crash_after = CRASH_AFTER_NONE,
+		.signal_from = SIGNAL_FROM_NONE,
+		.has_counter = false,
+		.has_change_priv = false,
+		.has_ip = false,
+		.has_port = false,
+		.has_timeout = false,
+	};
+
+	while ((opt = getopt(argc, argv, OPT_STRING)) != -1) {
+		switch (opt) {
+		case 'h':
+			usage(PROG_NAME);
+			return EXIT_SUCCESS;
+		case 'm':
+			args.mode = get_mode(optarg, PROG_NAME);
+			break;
+		case 'c':
+			args.crash_after = get_crash_after(optarg, PROG_NAME);
+			break;
+		case 's':
+			args.signal_from = get_signal_from(optarg, PROG_NAME);
+			break;
+		case 'n':
+			args.counter = get_counter(optarg, PROG_NAME);
+			args.has_counter = true;
+			break;
+		case 'C':
+			args.has_change_priv = true;
+			break;
+		case 'a':
+			args.ip = get_ip(optarg, PROG_NAME);
+			args.has_ip = true;
+			break;
+		case 'p':
+			args.port = get_port(optarg, PROG_NAME);
+			args.has_port = true;
+			break;
+		case 't':
+			args.timeout = get_timeout(optarg, PROG_NAME);
+			args.has_timeout = true;
+			break;
+		default:
+			usage(PROG_NAME);
+			return EXIT_FAILURE;
+		}
+	}
+
+	check_args(&args, PROG_NAME);
+
+	if (args.mode == MODE_CRASH) {
+		do_crash(args.crash_after, args.signal_from, args.counter,
+			 args.has_change_priv);
+	} else if (args.mode == MODE_SERVER_CRASH) {
+		do_server(args.ip, args.port, args.timeout);
+		do_crash(args.crash_after, args.signal_from, args.counter,
+			 false);
+	} else if (args.mode == MODE_CLIENT) {
+		do_client(args.ip, args.port, args.timeout);
+	}
+
+	return EXIT_SUCCESS;
+}
diff --git a/tools/testing/selftests/brute/test.sh b/tools/testing/selftests/brute/test.sh
new file mode 100755
index 000000000000..f53f26ae5b96
--- /dev/null
+++ b/tools/testing/selftests/brute/test.sh
@@ -0,0 +1,226 @@ 
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+TCID="test.sh"
+
+KSFT_PASS=0
+KSFT_FAIL=1
+KSFT_SKIP=4
+
+errno=$KSFT_PASS
+
+check_root()
+{
+	local uid=$(id -u)
+	if [ $uid -ne 0 ]; then
+		echo $TCID: must be run as root >&2
+		exit $KSFT_SKIP
+	fi
+}
+
+count_fork_matches()
+{
+	dmesg | grep "brute: Fork brute force attack detected" | wc -l
+}
+
+assert_equal()
+{
+	local val1=$1
+	local val2=$2
+
+	if [ $val1 -eq $val2 ]; then
+		echo "$TCID: $message [PASS]"
+	else
+		echo "$TCID: $message [FAIL]"
+		errno=$KSFT_FAIL
+	fi
+}
+
+test_fork_user()
+{
+	COUNTER=20
+
+	old_count=$(count_fork_matches)
+	./exec test -m crash -c fork -s user -n $COUNTER
+	new_count=$(count_fork_matches)
+
+	message="Fork attack (user signals, no bounds crossed)"
+	assert_equal $old_count $new_count
+}
+
+test_fork_kernel()
+{
+	old_count=$(count_fork_matches)
+	./exec test -m crash -c fork -s kernel -n $COUNTER
+	new_count=$(count_fork_matches)
+
+	message="Fork attack (kernel signals, no bounds crossed)"
+	assert_equal $old_count $new_count
+}
+
+count_exec_matches()
+{
+	dmesg | grep "brute: Exec brute force attack detected" | wc -l
+}
+
+test_exec_user()
+{
+	old_count=$(count_exec_matches)
+	./test -m crash -c exec -s user -n $COUNTER
+	new_count=$(count_exec_matches)
+
+	message="Exec attack (user signals, no bounds crossed)"
+	assert_equal $old_count $new_count
+}
+
+test_exec_kernel()
+{
+	old_count=$(count_exec_matches)
+	./test -m crash -c exec -s kernel -n $COUNTER
+	new_count=$(count_exec_matches)
+
+	message="Exec attack (kernel signals, no bounds crossed)"
+	assert_equal $old_count $new_count
+}
+
+assert_not_equal()
+{
+	local val1=$1
+	local val2=$2
+
+	if [ $val1 -ne $val2 ]; then
+		echo $TCID: $message [PASS]
+	else
+		echo $TCID: $message [FAIL]
+		errno=$KSFT_FAIL
+	fi
+}
+
+test_fork_kernel_setuid()
+{
+	old_count=$(count_fork_matches)
+	chmod u+s test
+	./exec test -m crash -c fork -s kernel -n $COUNTER
+	chmod u-s test
+	new_count=$(count_fork_matches)
+
+	message="Fork attack (kernel signals, setuid binary)"
+	assert_not_equal $old_count $new_count
+}
+
+test_exec_kernel_setuid()
+{
+	old_count=$(count_exec_matches)
+	chmod u+s test
+	./test -m crash -c exec -s kernel -n $COUNTER
+	chmod u-s test
+	new_count=$(count_exec_matches)
+
+	message="Exec attack (kernel signals, setuid binary)"
+	assert_not_equal $old_count $new_count
+}
+
+test_fork_kernel_change_priv()
+{
+	old_count=$(count_fork_matches)
+	./exec test -m crash -c fork -s kernel -n $COUNTER -C
+	new_count=$(count_fork_matches)
+
+	message="Fork attack (kernel signals, change privileges)"
+	assert_not_equal $old_count $new_count
+}
+
+test_exec_kernel_change_priv()
+{
+	old_count=$(count_exec_matches)
+	./test -m crash -c exec -s kernel -n $COUNTER -C
+	new_count=$(count_exec_matches)
+
+	message="Exec attack (kernel signals, change privileges)"
+	assert_not_equal $old_count $new_count
+}
+
+network_ns_setup()
+{
+	local vnet_name=$1
+	local veth_name=$2
+	local ip_src=$3
+	local ip_dst=$4
+
+	ip netns add $vnet_name
+	ip link set $veth_name netns $vnet_name
+	ip -n $vnet_name addr add $ip_src/24 dev $veth_name
+	ip -n $vnet_name link set $veth_name up
+	ip -n $vnet_name route add $ip_dst/24 dev $veth_name
+}
+
+network_setup()
+{
+	VETH0_NAME=veth0
+	VNET0_NAME=vnet0
+	VNET0_IP=10.0.1.0
+	VETH1_NAME=veth1
+	VNET1_NAME=vnet1
+	VNET1_IP=10.0.2.0
+
+	ip link add $VETH0_NAME type veth peer name $VETH1_NAME
+	network_ns_setup $VNET0_NAME $VETH0_NAME $VNET0_IP $VNET1_IP
+	network_ns_setup $VNET1_NAME $VETH1_NAME $VNET1_IP $VNET0_IP
+}
+
+test_fork_kernel_network_to_local()
+{
+	INADDR_ANY=0.0.0.0
+	PORT=65535
+	TIMEOUT=5
+
+	old_count=$(count_fork_matches)
+	ip netns exec $VNET0_NAME ./exec test -m server_crash -a $INADDR_ANY \
+		-p $PORT -t $TIMEOUT -c fork -s kernel -n $COUNTER &
+	sleep 1
+	ip netns exec $VNET1_NAME ./test -m client -a $VNET0_IP -p $PORT \
+		-t $TIMEOUT
+	sleep 1
+	new_count=$(count_fork_matches)
+
+	message="Fork attack (kernel signals, network to local)"
+	assert_not_equal $old_count $new_count
+}
+
+test_exec_kernel_network_to_local()
+{
+	old_count=$(count_exec_matches)
+	ip netns exec $VNET0_NAME ./test -m server_crash -a $INADDR_ANY \
+		-p $PORT -t $TIMEOUT -c exec -s kernel -n $COUNTER &
+	sleep 1
+	ip netns exec $VNET1_NAME ./test -m client -a $VNET0_IP -p $PORT \
+		-t $TIMEOUT
+	sleep 1
+	new_count=$(count_exec_matches)
+
+	message="Exec attack (kernel signals, network to local)"
+	assert_not_equal $old_count $new_count
+}
+
+network_cleanup()
+{
+	ip netns del $VNET0_NAME >/dev/null 2>&1
+	ip netns del $VNET1_NAME >/dev/null 2>&1
+	ip link delete $VETH0_NAME >/dev/null 2>&1
+	ip link delete $VETH1_NAME >/dev/null 2>&1
+}
+
+check_root
+test_fork_user
+test_fork_kernel
+test_exec_user
+test_exec_kernel
+test_fork_kernel_setuid
+test_exec_kernel_setuid
+test_fork_kernel_change_priv
+test_exec_kernel_change_priv
+network_setup
+test_fork_kernel_network_to_local
+test_exec_kernel_network_to_local
+network_cleanup
+exit $errno