linux-kernel - [PATCH v7 3/4] samples/landlock: Support abstract unix socket restriction

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Message-Id: <4f533a80d56d9f57d50a87d55101cfdeb03404c3.1721269836.git.fahimitahera@gmail.com>
Date: Wed, 17 Jul 2024 22:15:21 -0600
From: Tahera Fahimi <fahimitahera@...il.com>
To: mic@...ikod.net,
	gnoack@...gle.com,
	paul@...l-moore.com,
	jmorris@...ei.org,
	serge@...lyn.com,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bjorn3_gh@...tonmail.com,
	jannh@...gle.com,
	outreachy@...ts.linux.dev,
	netdev@...r.kernel.org
Cc: Tahera Fahimi <fahimitahera@...il.com>
Subject: [PATCH v7 3/4] samples/landlock: Support abstract unix socket restriction

- 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 to LANDLOCK_ABI_LAST to 6.

Signed-off-by: Tahera Fahimi <fahimitahera@...il.com>
---
 samples/landlock/sandboxer.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index e8223c3e781a..d280616585d4 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>
@@ -55,6 +56,7 @@ 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)
@@ -208,7 +210,7 @@ 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)
 {
@@ -216,6 +218,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
 	char *const *cmd_argv;
 	int ruleset_fd, abi;
 	char *env_port_name;
+	char *env_scoped_name;
 	__u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ,
 	      access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE;
 
@@ -223,14 +226,15 @@ 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 +255,18 @@ 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 allowed restriction 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",
@@ -326,7 +333,10 @@ 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 IPC scoping mechanism for ABI < 6 */
+		ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET;
 		fprintf(stderr,
 			"Hint: You should update the running kernel "
 			"to leverage Landlock features "
@@ -357,7 +367,10 @@ int main(const int argc, char *const argv[], char *const *const envp)
 		ruleset_attr.handled_access_net &=
 			~LANDLOCK_ACCESS_NET_CONNECT_TCP;
 	}
-
+	/* Removes IPC scoping attribute if not supported by a user. */
+	env_scoped_name = getenv(ENV_SCOPED_NAME);
+	if (!env_scoped_name)
+		ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET;
 	ruleset_fd =
 		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
 	if (ruleset_fd < 0) {
-- 
2.34.1