From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-8faf.mail.infomaniak.ch (smtp-8faf.mail.infomaniak.ch [83.166.143.175]) (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 9938518754F for ; Mon, 12 Aug 2024 17:06:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=83.166.143.175 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723482415; cv=none; b=Un6fnfdNSlxoPwh6wfK04mXJDMGdf+ZtrN57qd4jfS8c0+Zmbrf45Grh8BBttyVh0YOprgaEl2cOUCqh6dTQY5oHalANpr4TtazJmZTdO3XPCeF11ugde9fNYJaNYS636zetpyXA3TXGk+HCSYqMyjtHCb6+FWSB04B4ho2haSw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723482415; c=relaxed/simple; bh=y3DW0EDeUvsEd3PRWHJDWn5wfZ2vluxQhHQzCiBtq2o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=S/k2aAs0AKpOMGqatBMfbMjgE5iTiB6Xnf4OjeXMHm/Ze+L1hrKIERMc7CGgFST9e5SIrtdLHklFS0F7aTuL2fKZNC94vUki3lFuk7yarOTf5PXWshAcbjgTjKlsU8XFVnIn2euXamkS2/iUjRz1FUbI+qzbvmibabnhVLozGzA= 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=RwvXhpgs; arc=none smtp.client-ip=83.166.143.175 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="RwvXhpgs" Received: from smtp-3-0000.mail.infomaniak.ch (smtp-3-0000.mail.infomaniak.ch [10.4.36.107]) by smtp-4-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4WjLXL4jYhzNnH; Mon, 12 Aug 2024 19:06:42 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=digikod.net; s=20191114; t=1723482402; bh=eWO8y4ow42QS6ibUFWSVvRwzqIRDIPIDZPm7Q1wmqHk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RwvXhpgsPJtvVGxu/D9DhI95TtlBM27OWFiiG9ferYWiEIzhxJ4YMVBVb7LNEBUYz vXmWq3U6Cswes9olhDqR9UX9RKSCiomk/nH6se+TovroxI0hKLpSTRd8NO9a+KQSd3 luEquFwNd6jZY6P7Gpboojb/fg6vdIB5HX9vTrb8= Received: from unknown by smtp-3-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4WjLXK6Hyxz6R3; Mon, 12 Aug 2024 19:06:41 +0200 (CEST) Date: Mon, 12 Aug 2024 19:06:36 +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: <20240812.Inohgai2eenu@digikod.net> References: <2b1ac6822d852ea70dd2dcdf41065076d9ee8028.1722570749.git.fahimitahera@gmail.com> <20240809.uupaip5Iepho@digikod.net> Precedence: bulk X-Mailing-List: linux-security-module@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: X-Infomaniak-Routing: alpha On Fri, Aug 09, 2024 at 12:16:37PM -0600, Tahera Fahimi wrote: > On Fri, Aug 09, 2024 at 04:11:47PM +0200, Mickaël Salaün wrote: > > 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 ? > Right, I will add this check before calling chek_ruleset_scope function. > > > > + 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. > For the second note, I think even if the user provides multiple "a" > (something like "a:a"), It would not have a different effect (for now). > Do you suggest that I change this way of handeling this environment > variable or add documents that mention this note? We should have a stricter approach to only allow zero or one "a" letter. > > > > > + } 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. > I think this happens in check_ruleset_scope function. However, I will > add a condition (abi >=6) to this "if" statement. > > > > + 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 > > > > > > >