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AJvYcCWJLr6heK+ZDJNG22NSa0l06SWeEnJPxahDvti42RMHkDvXG1g6y/GursPI9chO/Rs48Pt/4gFVTCoILGX+X0UlmVI2qJ3jLn7lrDNbD7Q/fya+8eW3JL/vD57FpsRw8gqPoHRyohcHE9bzmWlpeOyHFCFGfYU4Uo2zGYwcf7zQsvPfY9gmLXBi2Ck6 X-Gm-Message-State: AOJu0YyThuP8d+TE6PMt6qA964F4CUf/Yam9ar0boHK/hajfIrpQLrxw P94G59dPuERHi0Q84spZ59mHsS2eyqhZ4and2lR6XJJbbPwCTYTU X-Google-Smtp-Source: AGHT+IEYDNYKInMS3sjYGMrrwrb6W3AgsMv3z/oTq4RwfulLbbgIBY6gjz5fOXBjO9sspRWBr7e5bg== X-Received: by 2002:a05:6a21:38d:b0:1af:66aa:7fc7 with SMTP id adf61e73a8af0-1c6995795c3mr1987577637.3.1722571391105; Thu, 01 Aug 2024 21:03:11 -0700 (PDT) Received: from tahera-OptiPlex-5000.tail3bf47f.ts.net ([136.159.49.123]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7106ec41465sm542099b3a.60.2024.08.01.21.03.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Aug 2024 21:03:10 -0700 (PDT) From: Tahera Fahimi To: outreachy@lists.linux.dev Cc: mic@digikod.net, gnoack@google.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, bjorn3_gh@protonmail.com, jannh@google.com, netdev@vger.kernel.org, Tahera Fahimi Subject: [PATCH v8 3/4] sample/Landlock: Support abstract unix socket restriction Date: Thu, 1 Aug 2024 22:02:35 -0600 Message-Id: <2b1ac6822d852ea70dd2dcdf41065076d9ee8028.1722570749.git.fahimitahera@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 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 --- 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 | 56 +++++++++++++++++++++++++++++++++--- 1 file changed, 52 insertions(+), 4 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index e8223c3e781a..98132fd823ad 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include #include @@ -22,6 +23,7 @@ #include #include #include +#include #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 +187,38 @@ 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 ret = true; + char *env_type_scope, *env_type_scope_next, *ipc_scoping_name; + + ruleset_attr->scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; + env_type_scope = getenv(env_var); + /* scoping is not supported by the user */ + if (!env_type_scope) + return true; + 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) { + ruleset_attr->scoped |= + LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; + } else { + fprintf(stderr, "Unsupported scoping \"%s\"\n", + ipc_scoping_name); + ret = false; + goto out_free_name; + } + } +out_free_name: + free(env_type_scope); + return ret; +} + /* clang-format off */ #define ACCESS_FS_ROUGHLY_READ ( \ @@ -208,7 +243,7 @@ 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 +258,15 @@ 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 " " [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 +287,18 @@ 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 +366,10 @@ 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 +401,11 @@ 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)) { + perror("Unsupported IPC scoping requested"); + return 1; + } + ruleset_fd = landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); if (ruleset_fd < 0) {