| Message ID | 5f7ad85243b78427242275b93481cfc7c127764b.1725494372.git.fahimitahera@gmail.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | Landlock: Add abstract UNIX socket restriction | expand |
On Wed, Sep 04, 2024 at 06:13:55PM -0600, Tahera Fahimi wrote: > This patch introduces a new "scoped" attribute to the > landlock_ruleset_attr that can specify > "LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET" to scope abstract UNIX sockets > from connecting to a process outside of the same Landlock domain. It > implements two hooks, unix_stream_connect and unix_may_send to enforce > this restriction. > > Closes: https://github.com/landlock-lsm/linux/issues/7 > Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> > diff --git a/security/landlock/task.c b/security/landlock/task.c > index 849f5123610b..b9390445d242 100644 > --- a/security/landlock/task.c > +++ b/security/landlock/task.c > +static int hook_unix_stream_connect(struct sock *const sock, > + struct sock *const other, > + struct sock *const newsk) > +{ > + const struct landlock_ruleset *const dom = > + landlock_get_current_domain(); > + > + /* quick return for non-sandboxed processes */ > + if (!dom) > + return 0; > + > + if (is_abstract_socket(other) && sock_is_scoped(other, dom)) > + return -EPERM; I was wondering if it would make more sense to return -EACCES here. EACCES is usually related to file permission, but send(2)/sendto(2) don't return EPERM according to man pages. Well, according to the kernel code they can return EPERM so I think we are good with EPERM. It looks like other LSMs always use EACCES though... > + > + return 0; > +} > + > +static int hook_unix_may_send(struct socket *const sock, > + struct socket *const other) > +{ > + const struct landlock_ruleset *const dom = > + landlock_get_current_domain(); > + > + if (!dom) > + return 0; > + > + if (is_abstract_socket(other->sk)) { > + /* > + * Checks if this datagram socket was already allowed to > + * be connected to other. > + */ > + if (unix_peer(sock->sk) == other->sk) > + return 0; > + > + if (sock_is_scoped(other->sk, dom)) > + return -EPERM; ditto
On Wed, Sep 04, 2024 at 06:13:55PM -0600, Tahera Fahimi wrote: > This patch introduces a new "scoped" attribute to the > landlock_ruleset_attr that can specify > "LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET" to scope abstract UNIX sockets > from connecting to a process outside of the same Landlock domain. It > implements two hooks, unix_stream_connect and unix_may_send to enforce > this restriction. > > Closes: https://github.com/landlock-lsm/linux/issues/7 > Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> > > --- > v11: > - For a connected abstract datagram socket, the hook_unix_may_send > allows the socket to send a data. (it is treated as a connected stream > socket) > - Minor comment revision. > v10: > - Minor code improvement based on reviews on v9. > v9: > - Editting inline comments. > - Major refactoring in domain_is_scoped() and is_abstract_socket > v8: > - Code refactoring (improve code readability, renaming variable, etc.) > based on reviews by Mickaël Salaün on version 7. > - Adding warn_on_once to check (impossible) inconsistencies. > - Adding inline comments. > - Adding check_unix_address_format to check if the scoping socket is an > abstract UNIX sockets. > v7: > - Using socket's file credentials for both connected(STREAM) and > non-connected(DGRAM) sockets. > - Adding "domain_sock_scope" instead of the domain scoping mechanism > used in ptrace ensures that if a server's domain is accessible from > the client's domain (where the client is more privileged than the > server), the client can connect to the server in all edge cases. > - Removing debug codes. > v6: > - Removing curr_ruleset from landlock_hierarchy, and switching back to > use the same domain scoping as ptrace. > - code clean up. > v5: > - Renaming "LANDLOCK_*_ACCESS_SCOPE" to "LANDLOCK_*_SCOPE" > - Adding curr_ruleset to hierarachy_ruleset structure to have access > from landlock_hierarchy to its respective landlock_ruleset. > - Using curr_ruleset to check if a domain is scoped while walking in the > hierarchy of domains. > - Modifying inline comments. > v4: > - Rebased on Günther's Patch: > https://lore.kernel.org/all/20240610082115.1693267-1-gnoack@google.com/ > so there is no need for "LANDLOCK_SHIFT_ACCESS_SCOPE", then it is > removed. > - Adding get_scope_accesses function to check all scoped access masks in > a ruleset. > - Using socket's file credentials instead of credentials stored in > peer_cred for datagram sockets. (see discussion in [1]) > - Modifying inline comments. > V3: > - Improving commit description. > - Introducing "scoped" attribute to landlock_ruleset_attr for IPC > scoping purpose, and adding related functions. > - Changing structure of ruleset based on "scoped". > - Removing rcu lock and using unix_sk lock instead. > - Introducing scoping for datagram sockets in unix_may_send. > V2: > - Removing wrapper functions > > [1]https://lore.kernel.org/all/20240610.Aifee5ingugh@digikod.net/ > --- > include/uapi/linux/landlock.h | 28 ++++ > security/landlock/limits.h | 3 + > security/landlock/ruleset.c | 7 +- > security/landlock/ruleset.h | 24 +++- > security/landlock/syscalls.c | 17 ++- > security/landlock/task.c | 136 +++++++++++++++++++ > tools/testing/selftests/landlock/base_test.c | 2 +- > 7 files changed, 208 insertions(+), 9 deletions(-) > > diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h > index 2c8dbc74b955..dfd48d722834 100644 > --- a/include/uapi/linux/landlock.h > +++ b/include/uapi/linux/landlock.h > @@ -44,6 +44,12 @@ struct landlock_ruleset_attr { > * flags`_). > */ > __u64 handled_access_net; > + /** > + * @scoped: Bitmask of scopes (cf. `Scope flags`_) > + * restricting a Landlock domain from accessing outside > + * resources(e.g. IPCs). > + */ > + __u64 scoped; > }; > > /* > @@ -274,4 +280,26 @@ struct landlock_net_port_attr { > #define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0) > #define LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1) > /* clang-format on */ > + > +/** > + * DOC: scope > + * > + * Scope flags > + * ~~~~~~~~~~~ > + * > + * These flags enable to restrict a sandboxed process from a set of IPC > + * actions. Setting a flag for a ruleset will isolate the Landlock domain > + * to forbid connections to resources outside the domain. > + * > + * IPCs with scoped actions: > + * > + * - %LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET: Restrict a sandboxed process > + * from connecting to an abstract unix socket created by a process > + * outside the related Landlock domain (e.g. a parent domain or a > + * non-sandboxed process). > + */ > +/* clang-format off */ > +#define LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET (1ULL << 0) Thinking more about it, it makes more sense to rename it to LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET (s/SCOPED/SCOPE/) because it express a scope (not a "scoped") and it allign with the current LANDLOCK_ACCESS_* and other internal variables such as LANDLOCK_LAST_SCOPE... However, it still makes sense to keep the "scoped" ruleset's field, which is pretty similar to the "handled_*" semantic: it describes what will be *scoped* by the ruleset. > +/* clang-format on*/ > + > #endif /* _UAPI_LINUX_LANDLOCK_H */ > diff --git a/security/landlock/limits.h b/security/landlock/limits.h > index 4eb643077a2a..eb01d0fb2165 100644 > --- a/security/landlock/limits.h > +++ b/security/landlock/limits.h > @@ -26,6 +26,9 @@ > #define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET << 1) - 1) > #define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET) > > +#define LANDLOCK_LAST_SCOPE LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET > +#define LANDLOCK_MASK_SCOPE ((LANDLOCK_LAST_SCOPE << 1) - 1) > +#define LANDLOCK_NUM_SCOPE __const_hweight64(LANDLOCK_MASK_SCOPE) > /* clang-format on */
On Fri, Sep 13, 2024 at 03:32:59PM +0200, Mickaël Salaün wrote: > On Wed, Sep 04, 2024 at 06:13:55PM -0600, Tahera Fahimi wrote: > > This patch introduces a new "scoped" attribute to the > > landlock_ruleset_attr that can specify > > "LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET" to scope abstract UNIX sockets > > from connecting to a process outside of the same Landlock domain. It > > implements two hooks, unix_stream_connect and unix_may_send to enforce > > this restriction. > > > > Closes: https://github.com/landlock-lsm/linux/issues/7 > > Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> > > > > --- > > v11: > > - For a connected abstract datagram socket, the hook_unix_may_send > > allows the socket to send a data. (it is treated as a connected stream > > socket) > > - Minor comment revision. > > v10: > > - Minor code improvement based on reviews on v9. > > v9: > > - Editting inline comments. > > - Major refactoring in domain_is_scoped() and is_abstract_socket > > v8: > > - Code refactoring (improve code readability, renaming variable, etc.) > > based on reviews by Mickaël Salaün on version 7. > > - Adding warn_on_once to check (impossible) inconsistencies. > > - Adding inline comments. > > - Adding check_unix_address_format to check if the scoping socket is an > > abstract UNIX sockets. > > v7: > > - Using socket's file credentials for both connected(STREAM) and > > non-connected(DGRAM) sockets. > > - Adding "domain_sock_scope" instead of the domain scoping mechanism > > used in ptrace ensures that if a server's domain is accessible from > > the client's domain (where the client is more privileged than the > > server), the client can connect to the server in all edge cases. > > - Removing debug codes. > > v6: > > - Removing curr_ruleset from landlock_hierarchy, and switching back to > > use the same domain scoping as ptrace. > > - code clean up. > > v5: > > - Renaming "LANDLOCK_*_ACCESS_SCOPE" to "LANDLOCK_*_SCOPE" > > - Adding curr_ruleset to hierarachy_ruleset structure to have access > > from landlock_hierarchy to its respective landlock_ruleset. > > - Using curr_ruleset to check if a domain is scoped while walking in the > > hierarchy of domains. > > - Modifying inline comments. > > v4: > > - Rebased on Günther's Patch: > > https://lore.kernel.org/all/20240610082115.1693267-1-gnoack@google.com/ > > so there is no need for "LANDLOCK_SHIFT_ACCESS_SCOPE", then it is > > removed. > > - Adding get_scope_accesses function to check all scoped access masks in > > a ruleset. > > - Using socket's file credentials instead of credentials stored in > > peer_cred for datagram sockets. (see discussion in [1]) > > - Modifying inline comments. > > V3: > > - Improving commit description. > > - Introducing "scoped" attribute to landlock_ruleset_attr for IPC > > scoping purpose, and adding related functions. > > - Changing structure of ruleset based on "scoped". > > - Removing rcu lock and using unix_sk lock instead. > > - Introducing scoping for datagram sockets in unix_may_send. > > V2: > > - Removing wrapper functions > > > > [1]https://lore.kernel.org/all/20240610.Aifee5ingugh@digikod.net/ > > --- > > include/uapi/linux/landlock.h | 28 ++++ > > security/landlock/limits.h | 3 + > > security/landlock/ruleset.c | 7 +- > > security/landlock/ruleset.h | 24 +++- > > security/landlock/syscalls.c | 17 ++- > > security/landlock/task.c | 136 +++++++++++++++++++ > > tools/testing/selftests/landlock/base_test.c | 2 +- > > 7 files changed, 208 insertions(+), 9 deletions(-) > > > > diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h > > index 2c8dbc74b955..dfd48d722834 100644 > > --- a/include/uapi/linux/landlock.h > > +++ b/include/uapi/linux/landlock.h > > @@ -44,6 +44,12 @@ struct landlock_ruleset_attr { > > * flags`_). > > */ > > __u64 handled_access_net; > > + /** > > + * @scoped: Bitmask of scopes (cf. `Scope flags`_) > > + * restricting a Landlock domain from accessing outside > > + * resources(e.g. IPCs). > > + */ > > + __u64 scoped; > > }; > > > > /* > > @@ -274,4 +280,26 @@ struct landlock_net_port_attr { > > #define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0) > > #define LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1) > > /* clang-format on */ > > + > > +/** > > + * DOC: scope > > + * > > + * Scope flags > > + * ~~~~~~~~~~~ > > + * > > + * These flags enable to restrict a sandboxed process from a set of IPC > > + * actions. Setting a flag for a ruleset will isolate the Landlock domain > > + * to forbid connections to resources outside the domain. > > + * > > + * IPCs with scoped actions: > > + * > > + * - %LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET: Restrict a sandboxed process > > + * from connecting to an abstract unix socket created by a process > > + * outside the related Landlock domain (e.g. a parent domain or a > > + * non-sandboxed process). > > + */ > > +/* clang-format off */ > > +#define LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET (1ULL << 0) > > Thinking more about it, it makes more sense to rename it to > LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET (s/SCOPED/SCOPE/) because it > express a scope (not a "scoped") and it allign with the current > LANDLOCK_ACCESS_* and other internal variables such as > LANDLOCK_LAST_SCOPE... > > However, it still makes sense to keep the "scoped" ruleset's field, > which is pretty similar to the "handled_*" semantic: it describes what > will be *scoped* by the ruleset. The proposed changes make sense. They are applied in commit [0b365024c726277eb73e461849709605d1819977]/next branch, and look good to me. > > +/* clang-format on*/ > > + > > #endif /* _UAPI_LINUX_LANDLOCK_H */ > > diff --git a/security/landlock/limits.h b/security/landlock/limits.h > > index 4eb643077a2a..eb01d0fb2165 100644 > > --- a/security/landlock/limits.h > > +++ b/security/landlock/limits.h > > @@ -26,6 +26,9 @@ > > #define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET << 1) - 1) > > #define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET) > > > > +#define LANDLOCK_LAST_SCOPE LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET > > +#define LANDLOCK_MASK_SCOPE ((LANDLOCK_LAST_SCOPE << 1) - 1) > > +#define LANDLOCK_NUM_SCOPE __const_hweight64(LANDLOCK_MASK_SCOPE) > > /* clang-format on */
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h index 2c8dbc74b955..dfd48d722834 100644 --- a/include/uapi/linux/landlock.h +++ b/include/uapi/linux/landlock.h @@ -44,6 +44,12 @@ struct landlock_ruleset_attr { * flags`_). */ __u64 handled_access_net; + /** + * @scoped: Bitmask of scopes (cf. `Scope flags`_) + * restricting a Landlock domain from accessing outside + * resources(e.g. IPCs). + */ + __u64 scoped; }; /* @@ -274,4 +280,26 @@ struct landlock_net_port_attr { #define LANDLOCK_ACCESS_NET_BIND_TCP (1ULL << 0) #define LANDLOCK_ACCESS_NET_CONNECT_TCP (1ULL << 1) /* clang-format on */ + +/** + * DOC: scope + * + * Scope flags + * ~~~~~~~~~~~ + * + * These flags enable to restrict a sandboxed process from a set of IPC + * actions. Setting a flag for a ruleset will isolate the Landlock domain + * to forbid connections to resources outside the domain. + * + * IPCs with scoped actions: + * + * - %LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET: Restrict a sandboxed process + * from connecting to an abstract unix socket created by a process + * outside the related Landlock domain (e.g. a parent domain or a + * non-sandboxed process). + */ +/* clang-format off */ +#define LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET (1ULL << 0) +/* clang-format on*/ + #endif /* _UAPI_LINUX_LANDLOCK_H */ diff --git a/security/landlock/limits.h b/security/landlock/limits.h index 4eb643077a2a..eb01d0fb2165 100644 --- a/security/landlock/limits.h +++ b/security/landlock/limits.h @@ -26,6 +26,9 @@ #define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET << 1) - 1) #define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET) +#define LANDLOCK_LAST_SCOPE LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET +#define LANDLOCK_MASK_SCOPE ((LANDLOCK_LAST_SCOPE << 1) - 1) +#define LANDLOCK_NUM_SCOPE __const_hweight64(LANDLOCK_MASK_SCOPE) /* clang-format on */ #endif /* _SECURITY_LANDLOCK_LIMITS_H */ diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c index 6ff232f58618..a93bdbf52fff 100644 --- a/security/landlock/ruleset.c +++ b/security/landlock/ruleset.c @@ -52,12 +52,13 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers) struct landlock_ruleset * landlock_create_ruleset(const access_mask_t fs_access_mask, - const access_mask_t net_access_mask) + const access_mask_t net_access_mask, + const access_mask_t scope_mask) { struct landlock_ruleset *new_ruleset; /* Informs about useless ruleset. */ - if (!fs_access_mask && !net_access_mask) + if (!fs_access_mask && !net_access_mask && !scope_mask) return ERR_PTR(-ENOMSG); new_ruleset = create_ruleset(1); if (IS_ERR(new_ruleset)) @@ -66,6 +67,8 @@ landlock_create_ruleset(const access_mask_t fs_access_mask, landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0); if (net_access_mask) landlock_add_net_access_mask(new_ruleset, net_access_mask, 0); + if (scope_mask) + landlock_add_scope_mask(new_ruleset, scope_mask, 0); return new_ruleset; } diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h index 0f1b5b4c8f6b..a9ac2a0487d1 100644 --- a/security/landlock/ruleset.h +++ b/security/landlock/ruleset.h @@ -35,6 +35,8 @@ typedef u16 access_mask_t; static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS); /* Makes sure all network access rights can be stored. */ static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_NET); +/* Makes sure all scoped rights can be stored. */ +static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_SCOPE); /* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */ static_assert(sizeof(unsigned long) >= sizeof(access_mask_t)); @@ -42,6 +44,7 @@ static_assert(sizeof(unsigned long) >= sizeof(access_mask_t)); struct access_masks { access_mask_t fs : LANDLOCK_NUM_ACCESS_FS; access_mask_t net : LANDLOCK_NUM_ACCESS_NET; + access_mask_t scoped : LANDLOCK_NUM_SCOPE; }; typedef u16 layer_mask_t; @@ -233,7 +236,8 @@ struct landlock_ruleset { struct landlock_ruleset * landlock_create_ruleset(const access_mask_t access_mask_fs, - const access_mask_t access_mask_net); + const access_mask_t access_mask_net, + const access_mask_t scope_mask); void landlock_put_ruleset(struct landlock_ruleset *const ruleset); void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset); @@ -280,6 +284,17 @@ landlock_add_net_access_mask(struct landlock_ruleset *const ruleset, ruleset->access_masks[layer_level].net |= net_mask; } +static inline void +landlock_add_scope_mask(struct landlock_ruleset *const ruleset, + const access_mask_t scope_mask, const u16 layer_level) +{ + access_mask_t scoped_mask = scope_mask & LANDLOCK_MASK_SCOPE; + + /* Should already be checked in sys_landlock_create_ruleset(). */ + WARN_ON_ONCE(scope_mask != scoped_mask); + ruleset->access_masks[layer_level].scoped |= scoped_mask; +} + static inline access_mask_t landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset, const u16 layer_level) @@ -303,6 +318,13 @@ landlock_get_net_access_mask(const struct landlock_ruleset *const ruleset, return ruleset->access_masks[layer_level].net; } +static inline access_mask_t +landlock_get_scope_mask(const struct landlock_ruleset *const ruleset, + const u16 layer_level) +{ + return ruleset->access_masks[layer_level].scoped; +} + bool landlock_unmask_layers(const struct landlock_rule *const rule, const access_mask_t access_request, layer_mask_t (*const layer_masks)[], diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c index ccc8bc6c1584..c67836841e46 100644 --- a/security/landlock/syscalls.c +++ b/security/landlock/syscalls.c @@ -97,8 +97,9 @@ static void build_check_abi(void) */ ruleset_size = sizeof(ruleset_attr.handled_access_fs); ruleset_size += sizeof(ruleset_attr.handled_access_net); + ruleset_size += sizeof(ruleset_attr.scoped); BUILD_BUG_ON(sizeof(ruleset_attr) != ruleset_size); - BUILD_BUG_ON(sizeof(ruleset_attr) != 16); + BUILD_BUG_ON(sizeof(ruleset_attr) != 24); path_beneath_size = sizeof(path_beneath_attr.allowed_access); path_beneath_size += sizeof(path_beneath_attr.parent_fd); @@ -149,7 +150,7 @@ static const struct file_operations ruleset_fops = { .write = fop_dummy_write, }; -#define LANDLOCK_ABI_VERSION 5 +#define LANDLOCK_ABI_VERSION 6 /** * sys_landlock_create_ruleset - Create a new ruleset @@ -170,8 +171,9 @@ static const struct file_operations ruleset_fops = { * Possible returned errors are: * * - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time; - * - %EINVAL: unknown @flags, or unknown access, or too small @size; - * - %E2BIG or %EFAULT: @attr or @size inconsistencies; + * - %EINVAL: unknown @flags, or unknown access, or unknown scope, or too small @size; + * - %E2BIG: @attr or @size inconsistencies; + * - %EFAULT: @attr or @size inconsistencies; * - %ENOMSG: empty &landlock_ruleset_attr.handled_access_fs. */ SYSCALL_DEFINE3(landlock_create_ruleset, @@ -213,9 +215,14 @@ SYSCALL_DEFINE3(landlock_create_ruleset, LANDLOCK_MASK_ACCESS_NET) return -EINVAL; + /* Checks IPC scoping content (and 32-bits cast). */ + if ((ruleset_attr.scoped | LANDLOCK_MASK_SCOPE) != LANDLOCK_MASK_SCOPE) + return -EINVAL; + /* Checks arguments and transforms to kernel struct. */ ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs, - ruleset_attr.handled_access_net); + ruleset_attr.handled_access_net, + ruleset_attr.scoped); if (IS_ERR(ruleset)) return PTR_ERR(ruleset); diff --git a/security/landlock/task.c b/security/landlock/task.c index 849f5123610b..b9390445d242 100644 --- a/security/landlock/task.c +++ b/security/landlock/task.c @@ -13,6 +13,8 @@ #include <linux/lsm_hooks.h> #include <linux/rcupdate.h> #include <linux/sched.h> +#include <net/af_unix.h> +#include <net/sock.h> #include "common.h" #include "cred.h" @@ -108,9 +110,143 @@ static int hook_ptrace_traceme(struct task_struct *const parent) return task_ptrace(parent, current); } +/** + * domain_is_scoped - Checks if the client domain is scoped in the same + * domain as the server. + * + * @client: IPC sender domain. + * @server: IPC receiver domain. + * @scope: The scope restriction criteria. + * + * Returns: True if the @client domain is scoped to access the @server, + * unless the @server is also scoped in the same domain as @client. + */ +static bool domain_is_scoped(const struct landlock_ruleset *const client, + const struct landlock_ruleset *const server, + access_mask_t scope) +{ + int client_layer, server_layer; + struct landlock_hierarchy *client_walker, *server_walker; + + /* Quick return if client has no domain */ + if (WARN_ON_ONCE(!client)) + return false; + + client_layer = client->num_layers - 1; + client_walker = client->hierarchy; + /* + * client_layer must be a signed integer with greater capacity + * than client->num_layers to ensure the following loop stops. + */ + BUILD_BUG_ON(sizeof(client_layer) > sizeof(client->num_layers)); + + server_layer = server ? (server->num_layers - 1) : -1; + server_walker = server ? server->hierarchy : NULL; + + /* + * Walks client's parent domains down to the same hierarchy level + * as the server's domain, and checks that none of these client's + * parent domains are scoped. + */ + for (; client_layer > server_layer; client_layer--) { + if (landlock_get_scope_mask(client, client_layer) & scope) + return true; + client_walker = client_walker->parent; + } + /* + * Walks server's parent domains down to the same hierarchy level as + * the client's domain. + */ + for (; server_layer > client_layer; server_layer--) + server_walker = server_walker->parent; + + for (; client_layer >= 0; client_layer--) { + if (landlock_get_scope_mask(client, client_layer) & scope) { + /* + * Client and server are at the same level in the + * hierarchy. If the client is scoped, the request is + * only allowed if this domain is also a server's + * ancestor. + */ + return server_walker != client_walker; + } + client_walker = client_walker->parent; + server_walker = server_walker->parent; + } + return false; +} + +static bool sock_is_scoped(struct sock *const other, + const struct landlock_ruleset *const domain) +{ + const struct landlock_ruleset *dom_other; + + /* the credentials will not change */ + lockdep_assert_held(&unix_sk(other)->lock); + dom_other = landlock_cred(other->sk_socket->file->f_cred)->domain; + return domain_is_scoped(domain, dom_other, + LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET); +} + +static bool is_abstract_socket(struct sock *const sock) +{ + struct unix_address *addr = unix_sk(sock)->addr; + + if (!addr) + return false; + + if (addr->len >= offsetof(struct sockaddr_un, sun_path) + 1 && + addr->name[0].sun_path[0] == '\0') + return true; + + return false; +} + +static int hook_unix_stream_connect(struct sock *const sock, + struct sock *const other, + struct sock *const newsk) +{ + const struct landlock_ruleset *const dom = + landlock_get_current_domain(); + + /* quick return for non-sandboxed processes */ + if (!dom) + return 0; + + if (is_abstract_socket(other) && sock_is_scoped(other, dom)) + return -EPERM; + + return 0; +} + +static int hook_unix_may_send(struct socket *const sock, + struct socket *const other) +{ + const struct landlock_ruleset *const dom = + landlock_get_current_domain(); + + if (!dom) + return 0; + + if (is_abstract_socket(other->sk)) { + /* + * Checks if this datagram socket was already allowed to + * be connected to other. + */ + if (unix_peer(sock->sk) == other->sk) + return 0; + + if (sock_is_scoped(other->sk, dom)) + return -EPERM; + } + return 0; +} + static struct security_hook_list landlock_hooks[] __ro_after_init = { LSM_HOOK_INIT(ptrace_access_check, hook_ptrace_access_check), LSM_HOOK_INIT(ptrace_traceme, hook_ptrace_traceme), + LSM_HOOK_INIT(unix_stream_connect, hook_unix_stream_connect), + LSM_HOOK_INIT(unix_may_send, hook_unix_may_send), }; __init void landlock_add_task_hooks(void) diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c index 3b26bf3cf5b9..1bc16fde2e8a 100644 --- a/tools/testing/selftests/landlock/base_test.c +++ b/tools/testing/selftests/landlock/base_test.c @@ -76,7 +76,7 @@ TEST(abi_version) const struct landlock_ruleset_attr ruleset_attr = { .handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE, }; - ASSERT_EQ(5, landlock_create_ruleset(NULL, 0, + ASSERT_EQ(6, landlock_create_ruleset(NULL, 0, LANDLOCK_CREATE_RULESET_VERSION)); ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
This patch introduces a new "scoped" attribute to the landlock_ruleset_attr that can specify "LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET" to scope abstract UNIX sockets from connecting to a process outside of the same Landlock domain. It implements two hooks, unix_stream_connect and unix_may_send to enforce this restriction. Closes: https://github.com/landlock-lsm/linux/issues/7 Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> --- v11: - For a connected abstract datagram socket, the hook_unix_may_send allows the socket to send a data. (it is treated as a connected stream socket) - Minor comment revision. v10: - Minor code improvement based on reviews on v9. v9: - Editting inline comments. - Major refactoring in domain_is_scoped() and is_abstract_socket v8: - Code refactoring (improve code readability, renaming variable, etc.) based on reviews by Mickaël Salaün on version 7. - Adding warn_on_once to check (impossible) inconsistencies. - Adding inline comments. - Adding check_unix_address_format to check if the scoping socket is an abstract UNIX sockets. v7: - Using socket's file credentials for both connected(STREAM) and non-connected(DGRAM) sockets. - Adding "domain_sock_scope" instead of the domain scoping mechanism used in ptrace ensures that if a server's domain is accessible from the client's domain (where the client is more privileged than the server), the client can connect to the server in all edge cases. - Removing debug codes. v6: - Removing curr_ruleset from landlock_hierarchy, and switching back to use the same domain scoping as ptrace. - code clean up. v5: - Renaming "LANDLOCK_*_ACCESS_SCOPE" to "LANDLOCK_*_SCOPE" - Adding curr_ruleset to hierarachy_ruleset structure to have access from landlock_hierarchy to its respective landlock_ruleset. - Using curr_ruleset to check if a domain is scoped while walking in the hierarchy of domains. - Modifying inline comments. v4: - Rebased on Günther's Patch: https://lore.kernel.org/all/20240610082115.1693267-1-gnoack@google.com/ so there is no need for "LANDLOCK_SHIFT_ACCESS_SCOPE", then it is removed. - Adding get_scope_accesses function to check all scoped access masks in a ruleset. - Using socket's file credentials instead of credentials stored in peer_cred for datagram sockets. (see discussion in [1]) - Modifying inline comments. V3: - Improving commit description. - Introducing "scoped" attribute to landlock_ruleset_attr for IPC scoping purpose, and adding related functions. - Changing structure of ruleset based on "scoped". - Removing rcu lock and using unix_sk lock instead. - Introducing scoping for datagram sockets in unix_may_send. V2: - Removing wrapper functions [1]https://lore.kernel.org/all/20240610.Aifee5ingugh@digikod.net/ --- include/uapi/linux/landlock.h | 28 ++++ security/landlock/limits.h | 3 + security/landlock/ruleset.c | 7 +- security/landlock/ruleset.h | 24 +++- security/landlock/syscalls.c | 17 ++- security/landlock/task.c | 136 +++++++++++++++++++ tools/testing/selftests/landlock/base_test.c | 2 +- 7 files changed, 208 insertions(+), 9 deletions(-)