[RFC PATCH v2 12/12] samples/landlock: Support socket protocol restrictions
Mikhail Ivanov
ivanov.mikhail1 at huawei-partners.com
Fri May 24 09:30:15 UTC 2024
* Add socket protocol control support in sandboxer demo. It's possible
to allow a sandboxer to create sockets with specified family and type
values. This is controlled with the new LL_SOCKET_CREATE environment
variable. Single token in this variable looks like this:
'FAMILY.TYPE', where FAMILY corresponds to one of the possible socket
family name and TYPE to the possible socket type name (see socket(2)).
Add ENV_TOKEN_INTERNAL_DELIMITER.
* Add parse_socket_protocol() method to parse socket family and type
strings to the appropriate constants. Add CHECK_FAMILY() and
CHECK_TYPE() macroses to prevent copypaste in method.
* Change LANDLOCK_ABI_LAST to 6.
Signed-off-by: Mikhail Ivanov <ivanov.mikhail1 at huawei-partners.com>
---
Changes since v1:
* Refactors get_socket_protocol(). Rename it to parse_socket_protocol().
* Changes LANDLOCK_ABI_LAST to 6 since ioctl patchlist updated it to 5.
* Refactors commit message.
* Formats with clang-format.
* Minor changes.
---
samples/landlock/sandboxer.c | 141 +++++++++++++++++++++++++++++++----
1 file changed, 127 insertions(+), 14 deletions(-)
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index e8223c3e781a..b6afe011e563 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -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>
@@ -55,8 +56,11 @@ 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_SOCKET_CREATE_NAME "LL_SOCKET_CREATE"
#define ENV_DELIMITER ":"
+#define ENV_TOKEN_INTERNAL_DELIMITER "."
+
static int parse_path(char *env_path, const char ***const path_list)
{
int i, num_paths = 0;
@@ -86,6 +90,42 @@ static int parse_path(char *env_path, const char ***const path_list)
/* clang-format on */
+static int parse_socket_protocol(char *strfamily, char *strtype,
+ struct landlock_socket_attr *protocol)
+{
+ protocol->family = -1;
+ protocol->type = -1;
+
+#define CHECK_FAMILY(family_variant) \
+ do { \
+ if (strcmp(strfamily, #family_variant) == 0) { \
+ protocol->family = family_variant; \
+ } \
+ } while (0)
+
+#define CHECK_TYPE(type_variant) \
+ do { \
+ if (strcmp(strtype, #type_variant) == 0) { \
+ protocol->type = type_variant; \
+ } \
+ } while (0)
+
+ CHECK_FAMILY(AF_UNIX);
+ CHECK_FAMILY(AF_INET);
+ CHECK_FAMILY(AF_INET6);
+
+ CHECK_TYPE(SOCK_STREAM);
+ CHECK_TYPE(SOCK_DGRAM);
+
+#undef CHECK_FAMILY
+#undef CHECK_TYPE
+
+ /* Unknown protocol or type. */
+ if (protocol->family == -1 || protocol->type == -1)
+ return 1;
+ return 0;
+}
+
static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,
const __u64 allowed_access)
{
@@ -184,6 +224,61 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
return ret;
}
+static int populate_ruleset_socket(const char *const env_var,
+ const int ruleset_fd,
+ const __u64 allowed_access)
+{
+ int ret = 1;
+ char *env_protocol_name, *strprotocol, *strfamily, *strtype;
+ struct landlock_socket_attr protocol = {
+ .allowed_access = allowed_access,
+ .family = 0,
+ .type = 0,
+ };
+
+ env_protocol_name = getenv(env_var);
+ if (!env_protocol_name)
+ return 0;
+ env_protocol_name = strdup(env_protocol_name);
+ unsetenv(env_var);
+
+ while ((strprotocol = strsep(&env_protocol_name, ENV_DELIMITER))) {
+ strfamily = strsep(&strprotocol, ENV_TOKEN_INTERNAL_DELIMITER);
+ strtype = strsep(&strprotocol, ENV_TOKEN_INTERNAL_DELIMITER);
+
+ if (!strtype) {
+ fprintf(stderr,
+ "Failed to extract socket protocol with "
+ "unspecified type value\n");
+ goto out_free_name;
+ }
+
+ if (parse_socket_protocol(strfamily, strtype, &protocol)) {
+ fprintf(stderr,
+ "Failed to extract socket protocol with "
+ "domain: \"%s\", type: \"%s\"\n"
+ "Sandboxer currently supports AF_UNIX, AF_INET, AF_INET6 "
+ "families and SOCK_STREAM, SOCK_DGRAM types\n",
+ strfamily, strtype);
+ goto out_free_name;
+ }
+
+ if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_SOCKET,
+ &protocol, 0)) {
+ fprintf(stderr,
+ "Failed to update the ruleset with "
+ "family \"%s\" and type \"%s\": %s\n",
+ strfamily, strtype, strerror(errno));
+ goto out_free_name;
+ }
+ }
+ ret = 0;
+
+out_free_name:
+ free(env_protocol_name);
+ return ret;
+}
+
/* clang-format off */
#define ACCESS_FS_ROUGHLY_READ ( \
@@ -208,14 +303,14 @@ 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)
{
const char *cmd_path;
char *const *cmd_argv;
int ruleset_fd, abi;
- char *env_port_name;
+ char *env_optional_name;
__u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ,
access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE;
@@ -223,18 +318,19 @@ 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,
+ .handled_access_socket = LANDLOCK_ACCESS_SOCKET_CREATE,
};
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_SOCKET_CREATE_NAME, argv[0]);
fprintf(stderr,
"Execute a command in a restricted environment.\n\n");
fprintf(stderr,
- "Environment variables containing paths and ports "
+ "Environment variables containing paths, ports and protocols "
"each separated by a colon:\n");
fprintf(stderr,
"* %s: list of paths allowed to be used in a read-only way.\n",
@@ -243,7 +339,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
"* %s: list of paths allowed to be used in a read-write way.\n\n",
ENV_FS_RW_NAME);
fprintf(stderr,
- "Environment variables containing ports are optional "
+ "Environment variables containing ports or protocols are optional "
"and could be skipped.\n");
fprintf(stderr,
"* %s: list of ports allowed to bind (server).\n",
@@ -251,22 +347,25 @@ 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 socket protocols allowed to be created.\n",
+ ENV_SOCKET_CREATE_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=\"AF_INET6.SOCK_DGRAM:AF_UNIX.SOCK_STREAM\" "
"%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_SOCKET_CREATE_NAME, argv[0]);
fprintf(stderr,
"This sandboxer can use Landlock features "
"up to ABI version %d.\n",
LANDLOCK_ABI_LAST);
return 1;
}
-
abi = landlock_create_ruleset(NULL, 0, LANDLOCK_CREATE_RULESET_VERSION);
if (abi < 0) {
const int err = errno;
@@ -326,7 +425,11 @@ int main(const int argc, char *const argv[], char *const *const envp)
case 4:
/* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */
ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV;
-
+ __attribute__((fallthrough));
+ case 5:
+ /* Removes socket support for ABI < 6 */
+ ruleset_attr.handled_access_socket &=
+ ~LANDLOCK_ACCESS_SOCKET_CREATE;
fprintf(stderr,
"Hint: You should update the running kernel "
"to leverage Landlock features "
@@ -346,18 +449,23 @@ int main(const int argc, char *const argv[], char *const *const envp)
access_fs_rw &= ruleset_attr.handled_access_fs;
/* Removes bind access attribute if not supported by a user. */
- env_port_name = getenv(ENV_TCP_BIND_NAME);
- if (!env_port_name) {
+ env_optional_name = getenv(ENV_TCP_BIND_NAME);
+ if (!env_optional_name) {
ruleset_attr.handled_access_net &=
~LANDLOCK_ACCESS_NET_BIND_TCP;
}
/* Removes connect access attribute if not supported by a user. */
- env_port_name = getenv(ENV_TCP_CONNECT_NAME);
- if (!env_port_name) {
+ env_optional_name = getenv(ENV_TCP_CONNECT_NAME);
+ if (!env_optional_name) {
ruleset_attr.handled_access_net &=
~LANDLOCK_ACCESS_NET_CONNECT_TCP;
}
-
+ /* Removes socket create access attribute if not supported by a user. */
+ env_optional_name = getenv(ENV_SOCKET_CREATE_NAME);
+ if (!env_optional_name) {
+ ruleset_attr.handled_access_socket &=
+ ~LANDLOCK_ACCESS_SOCKET_CREATE;
+ }
ruleset_fd =
landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
if (ruleset_fd < 0) {
@@ -381,6 +489,11 @@ int main(const int argc, char *const argv[], char *const *const envp)
goto err_close_ruleset;
}
+ if (populate_ruleset_socket(ENV_SOCKET_CREATE_NAME, ruleset_fd,
+ LANDLOCK_ACCESS_SOCKET_CREATE)) {
+ goto err_close_ruleset;
+ }
+
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
perror("Failed to restrict privileges");
goto err_close_ruleset;
--
2.34.1
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