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AJvYcCVA1B8fibhuOa9MGCMc79B8P4vXkDYgOqIyDCe83v/Y1KIn2XzL3N5pC4tT8EpFiLm8dv8suPjHmqSj1mSBp2DNNum+Yril@vger.kernel.org, AJvYcCW1pqCc655k5hVo5QcPJEJ/BDCY9zUCveHLh93wTLltmx6BSWAOV59mQgyJerQjtESfuNPvpBAIkd1EVag=@vger.kernel.org, AJvYcCW2nYHhm7spGI0e7EFT4Ic77/8/6JvztFg7sPBqdw8bpRK3oakI65EmcQcluhWUFjMyIKShSOl+@vger.kernel.org X-Gm-Message-State: AOJu0YzllZa8V/j+BDk/CS4DEwRlGBhnkbjQAlWjTYyh4tDyyfDlr5xJ kPnX3cpTrb94Ou3OLvwsfkqb7hDMdy0p6YCcDneKpcpG5/dq5FGlLUI94EA+ X-Google-Smtp-Source: AGHT+IF/swT4/QCQUaShc+LWLrYgsQ803/PfQesWXvFDsSqr4DHMuf7CQ8p1bPaggbUhXEZiXo2vvw== X-Received: by 2002:a05:6870:ab13:b0:260:e678:b653 with SMTP id 586e51a60fabf-277d06c890emr17533784fac.42.1725495269915; Wed, 04 Sep 2024 17:14:29 -0700 (PDT) Received: from tahera-OptiPlex-5000.tail3bf47f.ts.net ([136.159.49.123]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-71778534921sm2159781b3a.76.2024.09.04.17.14.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Sep 2024 17:14:29 -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 v11 7/8] sample/landlock: Add support abstract UNIX socket restriction Date: Wed, 4 Sep 2024 18:14:01 -0600 Message-Id: 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 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 --- 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(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index e8223c3e781a..18d072c23a23 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 +187,45 @@ 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 " " [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) {