From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-190f.mail.infomaniak.ch (smtp-190f.mail.infomaniak.ch [185.125.25.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CDB54195805 for ; Fri, 9 Aug 2024 14:11:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.125.25.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723212720; cv=none; b=FLIhfsPLMpL/NCsgP/WarMjCiRxa79t50R3iY4V9Pw5/Sw8XgDM5GajONYcjptkFeswAblMmjoyPKmpAf3ElKyukcUn6sLTtQ08rB6vjPrNgmIZQkRgyve3kUW9DkiNJzmBcqaPO8EZK1zAaHnhl5Rn/YsCN12IVwGvgLpXNp1E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723212720; c=relaxed/simple; bh=d2qpUjqP+5ygwVuOs3eMSo1YBavpbn1nxLoDr7z9oQQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=vAnFKRgGxPExZ9/BWTIN82hNnRQ9UNOMnairU/Pd8bwVtjmTNyF4Q+bQMYy5Q26p/VeWRr1yoPcZggfNGgM9ZqYM9nZM7AItb1WSGH2E4NafhnSaLDIi7jcHcNR+A/rtHcmYuR3aB6V90zwI5S6HV7WR9XrIcKhEroBdvT0c980= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net; spf=pass smtp.mailfrom=digikod.net; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b=sc5OSfc5; arc=none smtp.client-ip=185.125.25.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=digikod.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=digikod.net header.i=@digikod.net header.b="sc5OSfc5" Received: from smtp-4-0000.mail.infomaniak.ch (smtp-4-0000.mail.infomaniak.ch [10.7.10.107]) by smtp-4-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4WgQp1604fz6mf; Fri, 9 Aug 2024 16:11:53 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=digikod.net; s=20191114; t=1723212713; bh=alrcssf8lb4SOpOwA57ksV7R442dpGsapRV5pmoJxog=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sc5OSfc5KsTDO1QTM/8FIt51I2Z/1wYzmExzou+RihNNlqeUQTXutqdLOS+ddmfaM +GRwOTBFHjSV75JIBcPY2A+YiHII82jaUvTTJ5sd4PVaiToV60143MSlkbRdMAuS6f 8J+cd4wWBauEEYAtULmiIbZ5ea/jOrdnQWmDGquk= Received: from unknown by smtp-4-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4WgQp03lQBzqHV; Fri, 9 Aug 2024 16:11:52 +0200 (CEST) Date: Fri, 9 Aug 2024 16:11:47 +0200 From: =?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?= To: Tahera Fahimi Cc: outreachy@lists.linux.dev, 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 Subject: Re: [PATCH v8 3/4] sample/Landlock: Support abstract unix socket restriction Message-ID: <20240809.uupaip5Iepho@digikod.net> References: <2b1ac6822d852ea70dd2dcdf41065076d9ee8028.1722570749.git.fahimitahera@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2b1ac6822d852ea70dd2dcdf41065076d9ee8028.1722570749.git.fahimitahera@gmail.com> X-Infomaniak-Routing: alpha On Thu, Aug 01, 2024 at 10:02:35PM -0600, Tahera Fahimi wrote: > 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; Why always removing the suported scope? What happen if ABI < 6 ? > + 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; There are two issues here: 1. this would not work for ABI < 6 2. "a" can be repeated several times, which should probably not be allowed because we don't want to support this unspecified/undocumented behavior. > + } 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)) { You should use the same pattern as for TCP access rigths: if the environment variable is not set then remove the ruleset's scopes. > + perror("Unsupported IPC scoping requested"); > + return 1; > + } > + > ruleset_fd = > landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); > if (ruleset_fd < 0) { > -- > 2.34.1 > >