@@ -14,6 +14,7 @@
#include <fcntl.h>
#include <linux/landlock.h>
#include <linux/prctl.h>
+#include <linux/socket.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
@@ -22,6 +23,7 @@
#include <sys/stat.h>
#include <sys/syscall.h>
#include <unistd.h>
+#include <stdbool.h>
#ifndef landlock_create_ruleset
static inline int
@@ -55,6 +57,7 @@ static inline int landlock_restrict_self(const int ruleset_fd,
#define ENV_FS_RW_NAME "LL_FS_RW"
#define ENV_TCP_BIND_NAME "LL_TCP_BIND"
#define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT"
+#define ENV_SCOPED_NAME "LL_SCOPED"
#define ENV_DELIMITER ":"
static int parse_path(char *env_path, const char ***const path_list)
@@ -184,6 +187,45 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
return ret;
}
+static bool check_ruleset_scope(const char *const env_var,
+ struct landlock_ruleset_attr *ruleset_attr)
+{
+ bool abstract_scoping = false;
+ bool ret = true;
+ char *env_type_scope, *env_type_scope_next, *ipc_scoping_name;
+
+ /* scoping is not supported by Landlock ABI */
+ if (!(ruleset_attr->scoped & LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET))
+ return ret;
+
+ env_type_scope = getenv(env_var);
+ /* scoping is not supported by the user */
+ if (!env_type_scope || strcmp("", env_type_scope) == 0) {
+ ruleset_attr->scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET;
+ return ret;
+ }
+
+ env_type_scope = strdup(env_type_scope);
+ unsetenv(env_var);
+ env_type_scope_next = env_type_scope;
+ while ((ipc_scoping_name =
+ strsep(&env_type_scope_next, ENV_DELIMITER))) {
+ if (strcmp("a", ipc_scoping_name) == 0 && !abstract_scoping) {
+ abstract_scoping = true;
+ } else {
+ fprintf(stderr, "Unsupported scoping \"%s\"\n",
+ ipc_scoping_name);
+ ret = false;
+ goto out_free_name;
+ }
+ }
+ if (!abstract_scoping)
+ ruleset_attr->scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET;
+out_free_name:
+ free(env_type_scope);
+ return ret;
+}
+
/* clang-format off */
#define ACCESS_FS_ROUGHLY_READ ( \
@@ -208,7 +250,7 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
/* clang-format on */
-#define LANDLOCK_ABI_LAST 5
+#define LANDLOCK_ABI_LAST 6
int main(const int argc, char *const argv[], char *const *const envp)
{
@@ -223,14 +265,15 @@ int main(const int argc, char *const argv[], char *const *const envp)
.handled_access_fs = access_fs_rw,
.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
LANDLOCK_ACCESS_NET_CONNECT_TCP,
+ .scoped = LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET,
};
if (argc < 2) {
fprintf(stderr,
- "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\"%s "
+ "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s "
"<cmd> [args]...\n\n",
ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
- ENV_TCP_CONNECT_NAME, argv[0]);
+ ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]);
fprintf(stderr,
"Execute a command in a restricted environment.\n\n");
fprintf(stderr,
@@ -251,15 +294,18 @@ int main(const int argc, char *const argv[], char *const *const envp)
fprintf(stderr,
"* %s: list of ports allowed to connect (client).\n",
ENV_TCP_CONNECT_NAME);
+ fprintf(stderr, "* %s: list of restrictions on IPCs.\n",
+ ENV_SCOPED_NAME);
fprintf(stderr,
"\nexample:\n"
"%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" "
"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
"%s=\"9418\" "
"%s=\"80:443\" "
+ "%s=\"a\" "
"%s bash -i\n\n",
ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
- ENV_TCP_CONNECT_NAME, argv[0]);
+ ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]);
fprintf(stderr,
"This sandboxer can use Landlock features "
"up to ABI version %d.\n",
@@ -327,6 +373,10 @@ int main(const int argc, char *const argv[], char *const *const envp)
/* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */
ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV;
+ __attribute__((fallthrough));
+ case 5:
+ /* Removes LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET for ABI < 6 */
+ ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET;
fprintf(stderr,
"Hint: You should update the running kernel "
"to leverage Landlock features "
@@ -358,6 +408,9 @@ int main(const int argc, char *const argv[], char *const *const envp)
~LANDLOCK_ACCESS_NET_CONNECT_TCP;
}
+ if (!check_ruleset_scope(ENV_SCOPED_NAME, &ruleset_attr))
+ return 1;
+
ruleset_fd =
landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
if (ruleset_fd < 0) {
A sandboxer can receive the character "a" as input from the environment variable LL_SCOPE to restrict the abstract UNIX sockets from connecting to a process outside its scoped domain. Example ======= Create an abstract UNIX socket to listen with socat(1): socat abstract-listen:mysocket - Create a sandboxed shell and pass the character "a" to LL_SCOPED: LL_FS_RO=/ LL_FS_RW=. LL_SCOPED="a" ./sandboxer /bin/bash Note that any other form of input(e.g. "a:a", "aa", etc) is not acceptable. If the sandboxed process tries to connect to the listening socket with command "socat - abstract-connect:mysocket", the connection will fail. Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> --- v11: - Change implementation of check_ruleset_scope function to make it less bug prone. - Imptovement on the commit description. v10: - Minor improvement in code based on v9. v9: - Add a restrict approach on input of LL_SCOPED, so it only allows zero or one "a" to be the input. v8: - Adding check_ruleset_scope function to parse the scope environment variable and update the landlock attribute based on the restriction provided by the user. - Adding Mickaël Salaün reviews on version 7. v7: - Adding IPC scoping to the sandbox demo by defining a new "LL_SCOPED" environment variable. "LL_SCOPED" gets value "a" to restrict abstract unix sockets. - Change LANDLOCK_ABI_LAST to 6. --- samples/landlock/sandboxer.c | 61 +++++++++++++++++++++++++++++++++--- 1 file changed, 57 insertions(+), 4 deletions(-)