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Subject[RFC v4 2/2] WhiteEgret: Add an example of user application.
Date
A user application is required to use WhiteEgret.
This RFC provides a sample user application program.

Usage
sample-we-user <exe> <interpreter exe> <script>

This sample user application always returns "not permit"
for the executable specified by the argument <exe>,
otherwise always returns "permit". Set the absolute path
of an executable to be blocked for <exe>.

If the process of <interpreter exe> opening <script>, WhiteEgret
denies the execution request of the script. If the process opens
the other file, WhiteEgret allows the execution request.

Example
sample-we-user /bin/df /bin/perl /tmp/test.pl

Then every executions of /bin/df are blocked.
The other commands can be issued normally.

If the process family of /bin/perl requests to open
/tmp/test.pl, WhiteEgret denies the request. If the
process family requests to open other file, it is
permitted.

How to build
To build this sample user application, please set option
CONFIG_SAMPLE_WHITEEGRET=y. To enable to control for script
execution, also set SECURITY_WHITEEGRET_INTERPRETER=y,
CONFIG_SECURITY_WHITEEGRET_HOOK_READ_OPEN=y and
CONFIG_SECURITY_WHITEEGRET_CHECK_LIVING_TASK=y.

Remark
This sample user application does not use a whitelist.
The reason why this sample user application adopts
blacklist-like approach is to avoid a host to become
uncontrollable. Namely, if this sample provides a sample
whitelist and it misses indispensable executable components
for a host, the host cannot run or stop normally.
Because indispensable executable components depend on
each environment, we decide not to provide a whitelisting-type
sample user application.

Signed-off-by: Shinya Takumi <shinya1.takumi@toshiba.co.jp>
---
samples/Kconfig | 6 ++
samples/Makefile | 2 +-
samples/whiteegret/Makefile | 14 +++
samples/whiteegret/checkwl.c | 215 +++++++++++++++++++++++++++++++++++++++++++
samples/whiteegret/checkwl.h | 33 +++++++
samples/whiteegret/main.c | 119 ++++++++++++++++++++++++
6 files changed, 388 insertions(+), 1 deletion(-)
create mode 100644 samples/whiteegret/Makefile
create mode 100644 samples/whiteegret/checkwl.c
create mode 100644 samples/whiteegret/checkwl.h
create mode 100644 samples/whiteegret/main.c

diff --git a/samples/Kconfig b/samples/Kconfig
index ad1ec701..03a89c0 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -153,4 +153,10 @@ config SAMPLE_STATX
help
Build example userspace program to use the new extended-stat syscall.

+config SAMPLE_WHITEEGRET
+ bool "Build WhiteEgret sample user application"
+ depends on SECURITY_WHITEEGRET
+ help
+ Build sample userspace application for WhiteEgret LSM module.
+
endif # SAMPLES
diff --git a/samples/Makefile b/samples/Makefile
index bd601c0..d0c53d3 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -3,4 +3,4 @@
obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ livepatch/ \
hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/ \
configfs/ connector/ v4l/ trace_printk/ \
- vfio-mdev/ statx/ qmi/
+ vfio-mdev/ statx/ qmi/ whiteegret/
diff --git a/samples/whiteegret/Makefile b/samples/whiteegret/Makefile
new file mode 100644
index 0000000..77a0164
--- /dev/null
+++ b/samples/whiteegret/Makefile
@@ -0,0 +1,14 @@
+# kbuild trick to avoid linker error. Can be omitted if a module is built.
+obj- := dummy.o
+
+# List of programs to build
+hostprogs-$(CONFIG_SAMPLE_WHITEEGRET) := sample-we-user
+
+sample-we-user-objs := main.o checkwl.o
+
+HOSTCFLAGS += -Wall
+HOSTCFLAGS += -I/usr/local/include
+HOSTCFLAGS += -I$(srctree)/security/whiteegret
+
+# Tell kbuild to always build the programs
+always := $(hostprogs-y)
diff --git a/samples/whiteegret/checkwl.c b/samples/whiteegret/checkwl.c
new file mode 100644
index 0000000..806f2f0
--- /dev/null
+++ b/samples/whiteegret/checkwl.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * WhiteEgret Linux Security Module
+ *
+ * Sample program of user's whitelisting application
+ *
+ * Copyright (C) 2017-2018 Toshiba Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, version 2.
+ */
+
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include "checkwl.h"
+
+/*
+ * The function check_whitelist_exec() set -EACCES to result
+ * only when path to be examined equals to @a not_permit_exe.
+ */
+char not_permit_exe[NOTPERMITEXENAMELENGTH];
+
+/*
+ * The function check_whitelist_exec() store monitoring interpreter
+ * only when path to be examined equals to @a monitor_interpreter.
+ */
+char monitor_interpreter[NOTPERMITEXENAMELENGTH];
+
+/*
+ * The function check_whitelist_terp() set -EACCES to result
+ * only when path to be examined equals to @a not_permit_script.
+ */
+char not_permit_script[NOTPERMITEXENAMELENGTH];
+
+/*
+ * The struct records interpreter process tgid.
+ * This tgid recorded in @a root_terp_proc.
+ */
+struct terp_proc {
+ struct terp_proc *next;
+ pid_t tgid;
+};
+static struct terp_proc *root_terp_proc;
+
+void init_terp_proc(void)
+{
+ root_terp_proc = NULL;
+}
+
+static void register_terp_proc(pid_t tgid)
+{
+ struct terp_proc *proc;
+
+ proc = calloc(1, sizeof(*proc));
+ if (!proc)
+ return;
+
+ proc->tgid = tgid;
+ proc->next = root_terp_proc;
+ root_terp_proc = proc;
+}
+
+static void unregister_terp_proc(pid_t tgid)
+{
+ struct terp_proc *now, *back;
+
+ if (!root_terp_proc)
+ return;
+
+ if (root_terp_proc->tgid == tgid) {
+ root_terp_proc = root_terp_proc->next;
+ return;
+ }
+ for (back = root_terp_proc, now = back->next; now != NULL;
+ back = now, now = now->next) {
+ if (now->tgid == tgid) {
+ back->next = now->next;
+ free(now);
+ break;
+ }
+ }
+}
+
+static struct terp_proc *get_terp_proc(pid_t tgid)
+{
+ struct terp_proc *now;
+
+ for (now = root_terp_proc; now != NULL; now = now->next) {
+ if (now->tgid == tgid)
+ return now;
+ }
+ return NULL;
+}
+
+/**
+ * check_whitelist_exec - Examine whether the executable input to this function
+ * is included in whitelist or not.
+ *
+ * @result: Result of the examination.
+ * 0 if the executble is included in whitelist
+ * -EACCES otherwise ("not included")
+ *
+ * Returns 0 for success, -1 otherwise.
+ */
+int check_whitelist_exec(int *result, struct we_req_user *user)
+{
+ char *path;
+
+ if (result == NULL)
+ return -1;
+
+ *result = WE_EXEC_OK;
+
+ if (user == NULL)
+ return -1;
+
+ path = user->info.path;
+
+ /*
+ * Referring a whitelist is expected at this location.
+ * However, this sample uses not whitelist but blacklist
+ * because of avoiding a host to become uncontrollable.
+ * (not_permit_exe is a blacklist containing only one item.)
+ */
+ if (strncmp(not_permit_exe, path, NOTPERMITEXENAMELENGTH) == 0)
+ *result = -EACCES;
+ /*
+ * Referring a list is monitered a interpreter at this location.
+ * This location registers a tgid of monitering interpreter.
+ * Monitering interpreter is limited reading script.
+ */
+ else if (strncmp(monitor_interpreter, path,
+ NOTPERMITEXENAMELENGTH) == 0)
+ register_terp_proc(user->tgid);
+ return 0;
+}
+
+/**
+ * check_whitelist_terp - Examine whether the script input to this function
+ * is included in whitelist or not, if the process
+ * input to this function is registered in
+ * @root_terp_proc.
+ *
+ * @result: Result of the examination.
+ * 0 if the script is included in whitelist,
+ * or not registered process
+ * -EACCES otherwise ("not included")
+ *
+ * Returns 0 for success, -1 otherwise.
+ */
+int check_whitelist_terp(int *result, struct we_req_user *user)
+{
+ if (result == NULL)
+ return -1;
+
+ *result = WE_EXEC_OK;
+
+ /*
+ * if process reading a file is registered, referring a whitelist
+ * is expected at this location.
+ * However, this sample uses not whitelist but blacklist
+ * because of avoiding a host to become uncontrollable.
+ * (not_permit_script is a blacklist containing only one item.)
+ */
+ if (get_terp_proc(user->tgid)) {
+ if (strncmp(not_permit_script, user->info.path,
+ NOTPERMITEXENAMELENGTH) == 0)
+ *result = -EACCES;
+ }
+ return 0;
+}
+
+/**
+ * check_fork_terp - Register the child process to @root_terp_proc,
+ * if the parent process already has registerd to
+ * @root_terp_proc.
+ *
+ * Returns Allways 0.
+ */
+int check_fork_terp(int *result, struct we_req_user *user)
+{
+ if (result == NULL)
+ return -1;
+
+ *result = WE_EXEC_OK;
+ /*
+ * A child process of a interpreter has possibilities interpreter.
+ * This location registers a tgid of child process case of
+ * interpreter.
+ */
+ if (get_terp_proc(user->ppid))
+ register_terp_proc(user->tgid);
+ return 0;
+}
+
+/**
+ * check_exit_terp - Unregister the process form @root_terp_proc,
+ * case of matching @root_terp_proc.
+ *
+ * @result: Allways 0.
+ */
+int check_exit_terp(int *result, struct we_req_user *user)
+{
+ if (result == NULL)
+ return -1;
+
+ *result = WE_EXEC_OK;
+ /*
+ * This location unregisters exit process with interpreter.
+ */
+ unregister_terp_proc(user->tgid);
+ return 0;
+}
diff --git a/samples/whiteegret/checkwl.h b/samples/whiteegret/checkwl.h
new file mode 100644
index 0000000..14e1509
--- /dev/null
+++ b/samples/whiteegret/checkwl.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * WhiteEgret Linux Security Module
+ *
+ * Sample program of user's whitelisting application
+ *
+ * Copyright (C) 2017-2018 Toshiba Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, version 2.
+ */
+
+#ifndef _CHECKWL_H
+#define _CHECKWL_H
+
+#include <sys/types.h>
+#include "we_fs_common.h"
+
+/* byte length of absolute path of file not to permit execution */
+#define NOTPERMITEXENAMELENGTH 1024
+
+extern char not_permit_exe[NOTPERMITEXENAMELENGTH];
+extern char monitor_interpreter[NOTPERMITEXENAMELENGTH];
+extern char not_permit_script[NOTPERMITEXENAMELENGTH];
+
+void init_terp_proc(void);
+int check_whitelist_exec(int *result, struct we_req_user *user);
+int check_whitelist_terp(int *result, struct we_req_user *user);
+int check_fork_terp(int *result, struct we_req_user *user);
+int check_exit_terp(int *result, struct we_req_user *user);
+
+#endif
diff --git a/samples/whiteegret/main.c b/samples/whiteegret/main.c
new file mode 100644
index 0000000..20880df
--- /dev/null
+++ b/samples/whiteegret/main.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * WhiteEgret Linux Security Module
+ *
+ * Sample program of user's whitelisting application
+ *
+ * Copyright (C) 2017-2018 Toshiba Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, version 2.
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/epoll.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include "checkwl.h"
+
+#include <stdlib.h>
+#include "we_fs_common.h"
+
+#define MAXWAITFROMKER 10
+
+static void sigint_catch(int sig)
+{
+}
+
+static void print_usage(void)
+{
+ fprintf(stderr, "Usage: sample-we-user <executable file name> ");
+ fprintf(stderr, "<interpreter file name> <script file name>\n");
+ fprintf(stderr, "executable file name: absolute path of executable ");
+ fprintf(stderr, "not to permit execution.\n");
+ fprintf(stderr, "interpreter file name: absolute path of");
+ fprintf(stderr, "interpreter monitoring script read.\n");
+ fprintf(stderr, "script file name: absolute path of script file");
+ fprintf(stderr, "not to permit reading(execution).\n");
+ fprintf(stderr, "If you want to use controling script file, ");
+ fprintf(stderr, "you enable WhiteEgret Kernel option ");
+ fprintf(stderr, "CONFIG_SECURITY_WHITEEGRET_INTERPRETER.\n");
+}
+
+static int check_whitelist(int *result, struct we_req_user *user)
+{
+ int ret;
+
+ switch (user->cmd) {
+ case CONTROL_EXEC:
+ ret = check_whitelist_exec(result, user);
+ break;
+ case CONTROL_READ:
+ ret = check_whitelist_terp(result, user);
+ break;
+ case CONTROL_FORK:
+ ret = check_fork_terp(result, user);
+ break;
+ case CONTROL_EXIT:
+ ret = check_exit_terp(result, user);
+ break;
+ }
+ return ret;
+}
+
+int main(int argc, char *argv[])
+{
+ int fd;
+ struct we_req_user *user;
+ struct we_ack ack;
+ char buf[1024];
+ int ret;
+
+ if (argc < 4) {
+ print_usage();
+ return -1;
+ }
+
+ init_terp_proc();
+ snprintf(not_permit_exe, NOTPERMITEXENAMELENGTH, "%s", argv[1]);
+ snprintf(monitor_interpreter, NOTPERMITEXENAMELENGTH, "%s", argv[2]);
+ snprintf(not_permit_script, NOTPERMITEXENAMELENGTH, "%s", argv[3]);
+
+ signal(SIGINT, sigint_catch);
+
+ if (daemon(0, 0) < 0) {
+ perror("daemon");
+ exit(EXIT_FAILURE);
+ }
+
+ fd = open(WE_DEV_PATH, O_RDWR, 0);
+ if (fd < 0) {
+ perror(WE_DEV_PATH);
+ exit(EXIT_FAILURE);
+ }
+ user = (struct we_req_user *)((void *)buf);
+
+ while (1) {
+ ret = read(fd, (char *)user, 1024);
+ if (ret < 0) {
+ perror("read");
+ continue;
+ }
+
+ ack.tgid = user->tgid;
+ check_whitelist(&ack.permit, user);
+
+ ret = write(fd, (char *)&ack, sizeof(ack));
+ }
+
+ close(fd);
+
+ return 0;
+}
--
2.7.4
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