From: "Mickaël Salaün" <mic@digikod.net>
To: linux-kernel@vger.kernel.org
Cc: "Mickaël Salaün" <mic@digikod.net>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Andy Lutomirski" <luto@amacapital.net>,
"Arnd Bergmann" <arnd@arndb.de>,
"Casey Schaufler" <casey@schaufler-ca.com>,
"James Morris" <jmorris@namei.org>,
"Jann Horn" <jannh@google.com>,
"Jonathan Corbet" <corbet@lwn.net>,
"Kees Cook" <keescook@chromium.org>,
"Michael Kerrisk" <mtk.manpages@gmail.com>,
"Mickaël Salaün" <mickael.salaun@ssi.gouv.fr>,
"Serge E . Hallyn" <serge@hallyn.com>,
"Shuah Khan" <shuah@kernel.org>,
"Vincent Dagonneau" <vincent.dagonneau@ssi.gouv.fr>,
kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org,
linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-security-module@vger.kernel.org, x86@kernel.org
Subject: [PATCH v17 09/10] samples/landlock: Add a sandbox manager example
Date: Mon, 11 May 2020 21:21:55 +0200 [thread overview]
Message-ID: <20200511192156.1618284-10-mic@digikod.net> (raw)
In-Reply-To: <20200511192156.1618284-1-mic@digikod.net>
Add a basic sandbox tool to launch a command which can only access a
whitelist of file hierarchies in a read-only or read-write way.
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: James Morris <jmorris@namei.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge E. Hallyn <serge@hallyn.com>
---
Changes since v16:
* Switch syscall attribute pointer and size arguments.
Changes since v15:
* Update access right names.
* Properly assign access right to files according to the new related
syscall restriction.
* Replace "select" with "depends on" HEADERS_INSTALL (suggested by Randy
Dunlap).
Changes since v14:
* Fix Kconfig dependency.
* Remove access rights that may be required for FD-only requests:
mmap, truncate, getattr, lock, chmod, chown, chgrp, ioctl.
* Fix useless hardcoded syscall number.
* Use execvpe().
* Follow symlinks.
* Extend help with common file paths.
* Constify variables.
* Clean up comments.
* Improve error message.
Changes since v11:
* Add back the filesystem sandbox manager and update it to work with the
new Landlock syscall.
Previous changes:
https://lore.kernel.org/lkml/20190721213116.23476-9-mic@digikod.net/
---
samples/Kconfig | 7 ++
samples/Makefile | 1 +
samples/landlock/.gitignore | 1 +
samples/landlock/Makefile | 15 +++
samples/landlock/sandboxer.c | 228 +++++++++++++++++++++++++++++++++++
5 files changed, 252 insertions(+)
create mode 100644 samples/landlock/.gitignore
create mode 100644 samples/landlock/Makefile
create mode 100644 samples/landlock/sandboxer.c
diff --git a/samples/Kconfig b/samples/Kconfig
index 9d236c346de5..5ec43a732b10 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -120,6 +120,13 @@ config SAMPLE_HIDRAW
bool "hidraw sample"
depends on HEADERS_INSTALL
+config SAMPLE_LANDLOCK
+ bool "Build Landlock sample code"
+ depends on HEADERS_INSTALL
+ help
+ Build a simple Landlock sandbox manager able to launch a process
+ restricted by a user-defined filesystem access-control security policy.
+
config SAMPLE_PIDFD
bool "pidfd sample"
depends on HEADERS_INSTALL
diff --git a/samples/Makefile b/samples/Makefile
index f8f847b4f61f..61a2bd216f53 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_SAMPLE_KDB) += kdb/
obj-$(CONFIG_SAMPLE_KFIFO) += kfifo/
obj-$(CONFIG_SAMPLE_KOBJECT) += kobject/
obj-$(CONFIG_SAMPLE_KPROBES) += kprobes/
+subdir-$(CONFIG_SAMPLE_LANDLOCK) += landlock
obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch/
subdir-$(CONFIG_SAMPLE_PIDFD) += pidfd
obj-$(CONFIG_SAMPLE_QMI_CLIENT) += qmi/
diff --git a/samples/landlock/.gitignore b/samples/landlock/.gitignore
new file mode 100644
index 000000000000..f43668b2d318
--- /dev/null
+++ b/samples/landlock/.gitignore
@@ -0,0 +1 @@
+/sandboxer
diff --git a/samples/landlock/Makefile b/samples/landlock/Makefile
new file mode 100644
index 000000000000..9dfb571641ba
--- /dev/null
+++ b/samples/landlock/Makefile
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: BSD-3-Clause
+
+hostprogs-y := sandboxer
+
+always := $(hostprogs-y)
+
+KBUILD_HOSTCFLAGS += -I$(objtree)/usr/include
+
+.PHONY: all clean
+
+all:
+ $(MAKE) -C ../.. samples/landlock/
+
+clean:
+ $(MAKE) -C ../.. M=samples/landlock/ clean
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
new file mode 100644
index 000000000000..e0059706c11f
--- /dev/null
+++ b/samples/landlock/sandboxer.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: BSD-3-Clause
+/*
+ * Simple Landlock sandbox manager able to launch a process restricted by a
+ * user-defined filesystem access-control security policy.
+ *
+ * Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net>
+ * Copyright © 2020 ANSSI
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/landlock.h>
+#include <linux/prctl.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <sys/stat.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#ifndef landlock
+static inline int landlock(const unsigned int command,
+ const unsigned int options, void *const attr_ptr,
+ const size_t attr_size)
+{
+ errno = 0;
+ return syscall(__NR_landlock, command, options, attr_ptr, attr_size,
+ NULL, 0);
+}
+#endif
+
+#define ENV_FS_RO_NAME "LL_FS_RO"
+#define ENV_FS_RW_NAME "LL_FS_RW"
+#define ENV_PATH_TOKEN ":"
+
+static int parse_path(char *env_path, const char ***const path_list)
+{
+ int i, path_nb = 0;
+
+ if (env_path) {
+ path_nb++;
+ for (i = 0; env_path[i]; i++) {
+ if (env_path[i] == ENV_PATH_TOKEN[0])
+ path_nb++;
+ }
+ }
+ *path_list = malloc(path_nb * sizeof(**path_list));
+ for (i = 0; i < path_nb; i++)
+ (*path_list)[i] = strsep(&env_path, ENV_PATH_TOKEN);
+
+ return path_nb;
+}
+
+#define ACCESS_FILE ( \
+ LANDLOCK_ACCESS_FS_EXECUTE | \
+ LANDLOCK_ACCESS_FS_WRITE_FILE | \
+ LANDLOCK_ACCESS_FS_READ_FILE)
+
+static int populate_ruleset(
+ const struct landlock_attr_features *const attr_features,
+ const char *const env_var, const int ruleset_fd,
+ const __u64 allowed_access)
+{
+ int path_nb, i;
+ char *env_path_name;
+ const char **path_list = NULL;
+ struct landlock_attr_path_beneath path_beneath = {
+ .ruleset_fd = ruleset_fd,
+ .parent_fd = -1,
+ };
+
+ env_path_name = getenv(env_var);
+ if (!env_path_name) {
+ fprintf(stderr, "Missing environment variable %s\n", env_var);
+ return 1;
+ }
+ env_path_name = strdup(env_path_name);
+ unsetenv(env_var);
+ path_nb = parse_path(env_path_name, &path_list);
+ if (path_nb == 1 && path_list[0][0] == '\0') {
+ fprintf(stderr, "Missing path in %s\n", env_var);
+ goto err_free_name;
+ }
+
+ for (i = 0; i < path_nb; i++) {
+ struct stat statbuf;
+
+ path_beneath.parent_fd = open(path_list[i], O_PATH |
+ O_CLOEXEC);
+ if (path_beneath.parent_fd < 0) {
+ fprintf(stderr, "Failed to open \"%s\": %s\n",
+ path_list[i],
+ strerror(errno));
+ goto err_free_name;
+ }
+ if (fstat(path_beneath.parent_fd, &statbuf)) {
+ close(path_beneath.parent_fd);
+ goto err_free_name;
+ }
+ /* Follows a best-effort approach. */
+ path_beneath.allowed_access = allowed_access &
+ attr_features->access_fs;
+ if (!S_ISDIR(statbuf.st_mode))
+ path_beneath.allowed_access &= ACCESS_FILE;
+ if (landlock(LANDLOCK_CMD_ADD_RULE,
+ LANDLOCK_OPT_ADD_RULE_PATH_BENEATH,
+ &path_beneath, sizeof(path_beneath))) {
+ fprintf(stderr, "Failed to update the ruleset with \"%s\": %s\n",
+ path_list[i], strerror(errno));
+ close(path_beneath.parent_fd);
+ goto err_free_name;
+ }
+ close(path_beneath.parent_fd);
+ }
+ free(env_path_name);
+ return 0;
+
+err_free_name:
+ free(env_path_name);
+ return 1;
+}
+
+#define ACCESS_FS_ROUGHLY_READ ( \
+ LANDLOCK_ACCESS_FS_EXECUTE | \
+ LANDLOCK_ACCESS_FS_READ_FILE | \
+ LANDLOCK_ACCESS_FS_READ_DIR | \
+ LANDLOCK_ACCESS_FS_CHROOT)
+
+#define ACCESS_FS_ROUGHLY_WRITE ( \
+ LANDLOCK_ACCESS_FS_WRITE_FILE | \
+ LANDLOCK_ACCESS_FS_REMOVE_DIR | \
+ LANDLOCK_ACCESS_FS_REMOVE_FILE | \
+ LANDLOCK_ACCESS_FS_MAKE_CHAR | \
+ LANDLOCK_ACCESS_FS_MAKE_DIR | \
+ LANDLOCK_ACCESS_FS_MAKE_REG | \
+ LANDLOCK_ACCESS_FS_MAKE_SOCK | \
+ LANDLOCK_ACCESS_FS_MAKE_FIFO | \
+ LANDLOCK_ACCESS_FS_MAKE_BLOCK | \
+ LANDLOCK_ACCESS_FS_MAKE_SYM)
+
+int main(const int argc, char *const argv[], char *const *const envp)
+{
+ const char *cmd_path;
+ char *const *cmd_argv;
+ int ruleset_fd;
+ struct landlock_attr_features attr_features;
+ struct landlock_attr_ruleset ruleset = {
+ .handled_access_fs = ACCESS_FS_ROUGHLY_READ |
+ ACCESS_FS_ROUGHLY_WRITE,
+ };
+ struct landlock_attr_enforce attr_enforce = {};
+
+ if (argc < 2) {
+ fprintf(stderr, "usage: %s=\"...\" %s=\"...\" %s <cmd> [args]...\n\n",
+ ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
+ fprintf(stderr, "Launch a command in a restricted environment.\n\n");
+ fprintf(stderr, "Environment variables containing paths, each separated by a colon:\n");
+ fprintf(stderr, "* %s: list of paths allowed to be used in a read-only way.\n",
+ ENV_FS_RO_NAME);
+ fprintf(stderr, "* %s: list of paths allowed to be used in a read-write way.\n",
+ ENV_FS_RO_NAME);
+ fprintf(stderr, "\nexample:\n"
+ "%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "
+ "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
+ "%s bash -i\n",
+ ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
+ return 1;
+ }
+
+ if (landlock(LANDLOCK_CMD_GET_FEATURES, LANDLOCK_OPT_GET_FEATURES,
+ &attr_features, sizeof(attr_features))) {
+ perror("Failed to probe the Landlock supported features");
+ switch (errno) {
+ case ENOSYS:
+ fprintf(stderr, "Hint: this kernel does not support Landlock.\n");
+ break;
+ case ENOPKG:
+ fprintf(stderr, "Hint: Landlock is currently disabled. It can be enabled in the kernel configuration or at boot with the \"lsm=landlock\" parameter.\n");
+ break;
+ }
+ return 1;
+ }
+ /* Follows a best-effort approach. */
+ ruleset.handled_access_fs &= attr_features.access_fs;
+ ruleset_fd = landlock(LANDLOCK_CMD_CREATE_RULESET,
+ LANDLOCK_OPT_CREATE_RULESET, &ruleset,
+ sizeof(ruleset));
+ if (ruleset_fd < 0) {
+ perror("Failed to create a ruleset");
+ return 1;
+ }
+ if (populate_ruleset(&attr_features, ENV_FS_RO_NAME, ruleset_fd,
+ ACCESS_FS_ROUGHLY_READ)) {
+ goto err_close_ruleset;
+ }
+ if (populate_ruleset(&attr_features, ENV_FS_RW_NAME, ruleset_fd,
+ ACCESS_FS_ROUGHLY_READ |
+ ACCESS_FS_ROUGHLY_WRITE)) {
+ goto err_close_ruleset;
+ }
+ if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
+ perror("Failed to restrict privileges");
+ goto err_close_ruleset;
+ }
+ attr_enforce.ruleset_fd = ruleset_fd;
+ if (landlock(LANDLOCK_CMD_ENFORCE_RULESET,
+ LANDLOCK_OPT_ENFORCE_RULESET, &attr_enforce,
+ sizeof(attr_enforce))) {
+ perror("Failed to enforce ruleset");
+ goto err_close_ruleset;
+ }
+ close(ruleset_fd);
+
+ cmd_path = argv[1];
+ cmd_argv = argv + 1;
+ execvpe(cmd_path, cmd_argv, envp);
+ fprintf(stderr, "Failed to execute \"%s\": %s\n", cmd_path,
+ strerror(errno));
+ fprintf(stderr, "Hint: access to the binary, the interpreter or shared libraries may be denied.\n");
+ return 1;
+
+err_close_ruleset:
+ close(ruleset_fd);
+ return 1;
+}
--
2.26.2
next prev parent reply other threads:[~2020-05-11 19:23 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-11 19:21 [PATCH v17 00/10] Landlock LSM Mickaël Salaün
2020-05-11 19:21 ` [PATCH v17 01/10] landlock: Add object management Mickaël Salaün
2020-05-11 19:21 ` [PATCH v17 02/10] landlock: Add ruleset and domain management Mickaël Salaün
2020-05-14 3:09 ` James Morris
2020-05-14 10:27 ` Mickaël Salaün
2020-05-11 19:21 ` [PATCH v17 03/10] landlock: Set up the security framework and manage credentials Mickaël Salaün
2020-05-11 19:21 ` [PATCH v17 04/10] landlock: Add ptrace restrictions Mickaël Salaün
2020-05-11 19:21 ` [PATCH v17 05/10] fs,landlock: Support filesystem access-control Mickaël Salaün
2020-05-14 3:37 ` James Morris
2020-05-14 10:39 ` Mickaël Salaün
2020-05-14 15:58 ` Casey Schaufler
2020-05-14 18:46 ` Mickaël Salaün
2020-05-14 17:31 ` James Morris
2020-05-14 18:49 ` Mickaël Salaün
2020-05-14 19:37 ` James Morris
2020-05-11 19:21 ` [PATCH v17 06/10] landlock: Add syscall implementation Mickaël Salaün
2020-05-11 19:21 ` [PATCH v17 07/10] arch: Wire up landlock() syscall Mickaël Salaün
2020-05-11 19:21 ` [PATCH v17 08/10] selftests/landlock: Add initial tests Mickaël Salaün
2020-05-11 19:21 ` Mickaël Salaün [this message]
2020-05-11 19:21 ` [PATCH v17 10/10] landlock: Add user and kernel documentation Mickaël Salaün
2020-05-11 21:54 ` [PATCH v17 00/10] Landlock LSM Mickaël Salaün
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200511192156.1618284-10-mic@digikod.net \
--to=mic@digikod.net \
--cc=arnd@arndb.de \
--cc=casey@schaufler-ca.com \
--cc=corbet@lwn.net \
--cc=jannh@google.com \
--cc=jmorris@namei.org \
--cc=keescook@chromium.org \
--cc=kernel-hardening@lists.openwall.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=mickael.salaun@ssi.gouv.fr \
--cc=mtk.manpages@gmail.com \
--cc=serge@hallyn.com \
--cc=shuah@kernel.org \
--cc=vincent.dagonneau@ssi.gouv.fr \
--cc=viro@zeniv.linux.org.uk \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).