Add a new type of eBPF program used by Landlock rules.
This new BPF program type will be registered with the Landlock LSM
initialization.
Add an initial Landlock Kconfig.
Changes since v5:
* rename file hooks.c to init.c
* fix spelling
Changes since v4:
* merge a minimal (not enabled) LSM code and Kconfig in this commit
Changes since v3:
* split commit
* revamp the landlock_context:
* add arch, syscall_nr and syscall_cmd (ioctl, fcntl…) to be able to
cross-check action with the event type
* replace args array with dedicated fields to ease the addition of new
fields
Signed-off-by: Mickaël Salaün <m...@digikod.net>
Cc: Alexei Starovoitov <a...@kernel.org>
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Daniel Borkmann <dan...@iogearbox.net>
Cc: David S. Miller <da...@davemloft.net>
Cc: James Morris <james.l.mor...@oracle.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Serge E. Hallyn <se...@hallyn.com>
---
include/linux/landlock.h | 23 ++++++++
include/uapi/linux/bpf.h | 105 +++++++++++++++++++++++++++++++++++
security/Kconfig | 1 +
security/Makefile | 2 +
security/landlock/Kconfig | 18 ++++++
security/landlock/Makefile | 3 +
security/landlock/common.h | 25 +++++++++
security/landlock/init.c | 123 +++++++++++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 105 +++++++++++++++++++++++++++++++++++
9 files changed, 405 insertions(+)
create mode 100644 include/linux/landlock.h
create mode 100644 security/landlock/Kconfig
create mode 100644 security/landlock/Makefile
create mode 100644 security/landlock/common.h
create mode 100644 security/landlock/init.c
diff --git a/include/linux/landlock.h b/include/linux/landlock.h
new file mode 100644
index 000000000000..53013dc374fe
--- /dev/null
+++ b/include/linux/landlock.h
@@ -0,0 +1,23 @@
+/*
+ * Landlock LSM - public kernel headers
+ *
+ * Copyright © 2017 Mickaël Salaün <m...@digikod.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _LINUX_LANDLOCK_H
+#define _LINUX_LANDLOCK_H
+#ifdef CONFIG_SECURITY_LANDLOCK
+
+/*
+ * This is not intended for the UAPI headers. Each userland software should use
+ * a static minimal version for the required features as explained in the
+ * documentation.
+ */
+#define LANDLOCK_VERSION 1
+
+#endif /* CONFIG_SECURITY_LANDLOCK */
+#endif /* _LINUX_LANDLOCK_H */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 0eb71ab9b4fd..619b1f8707cc 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -114,6 +114,7 @@ enum bpf_prog_type {
BPF_PROG_TYPE_LWT_IN,
BPF_PROG_TYPE_LWT_OUT,
BPF_PROG_TYPE_LWT_XMIT,
+ BPF_PROG_TYPE_LANDLOCK,
};
enum bpf_attach_type {
@@ -661,4 +662,108 @@ struct xdp_md {
__u32 data_end;
};
+/**
+ * enum landlock_subtype_event - event occurring when an action is performed on
+ * a particular kernel object
+ *
+ * An event is a policy decision point which exposes the same context type
+ * (especially the same arg[0-9] field types) for each rule execution.
+ *
+ * @LANDLOCK_SUBTYPE_EVENT_UNSPEC: invalid value
+ * @LANDLOCK_SUBTYPE_EVENT_FS: generic filesystem event
+ */
+enum landlock_subtype_event {
+ LANDLOCK_SUBTYPE_EVENT_UNSPEC,
+ LANDLOCK_SUBTYPE_EVENT_FS,
+};
+#define _LANDLOCK_SUBTYPE_EVENT_LAST LANDLOCK_SUBTYPE_EVENT_FS
+
+/**
+ * DOC: landlock_subtype_access
+ *
+ * eBPF context and functions allowed for a rule
+ *
+ * - LANDLOCK_SUBTYPE_ABILITY_WRITE: allows to directly send notification to
+ * userland (e.g. through a map), which may leaks sensitive information
+ * - LANDLOCK_SUBTYPE_ABILITY_DEBUG: allows to do debug actions (e.g. writing
+ * logs), which may be dangerous and should only be used for rule testing
+ */
+#define LANDLOCK_SUBTYPE_ABILITY_WRITE (1ULL << 0)
+#define LANDLOCK_SUBTYPE_ABILITY_DEBUG (1ULL << 1)
+#define _LANDLOCK_SUBTYPE_ABILITY_NB 2
+#define _LANDLOCK_SUBTYPE_ABILITY_MASK ((1ULL <<
_LANDLOCK_SUBTYPE_ABILITY_NB) - 1)
+
+/*
+ * Future options for a Landlock rule (e.g. run even if a previous rule denied
+ * an action).
+ */
+#define _LANDLOCK_SUBTYPE_OPTION_NB 0
+#define _LANDLOCK_SUBTYPE_OPTION_MASK ((1ULL <<
_LANDLOCK_SUBTYPE_OPTION_NB) - 1)
+
+/*
+ * Status visible in the @status field of a context (e.g. already called in
+ * this syscall session, with same args...).
+ *
+ * The @status field exposed to a rule shall depend on the rule version.
+ */
+#define _LANDLOCK_SUBTYPE_STATUS_NB 0
+#define _LANDLOCK_SUBTYPE_STATUS_MASK ((1ULL <<
_LANDLOCK_SUBTYPE_STATUS_NB) - 1)
+
+/**
+ * DOC: landlock_action_fs
+ *
+ * - %LANDLOCK_ACTION_FS_EXEC: execute a file or walk through a directory
+ * - %LANDLOCK_ACTION_FS_WRITE: modify a file or a directory view (which
+ * include mount actions)
+ * - %LANDLOCK_ACTION_FS_READ: read a file or a directory
+ * - %LANDLOCK_ACTION_FS_NEW: create a file or a directory
+ * - %LANDLOCK_ACTION_FS_GET: open or receive a file
+ * - %LANDLOCK_ACTION_FS_REMOVE: unlink a file or remove a directory
+ *
+ * Each of the following actions are specific to syscall multiplexers. They
+ * fill the syscall_cmd field from &struct landlock_context with their custom
+ * command.
+ *
+ * - %LANDLOCK_ACTION_FS_IOCTL: ioctl command
+ * - %LANDLOCK_ACTION_FS_LOCK: flock or fcntl lock command
+ * - %LANDLOCK_ACTION_FS_FCNTL: fcntl command
+ */
+#define LANDLOCK_ACTION_FS_EXEC (1ULL << 0)
+#define LANDLOCK_ACTION_FS_WRITE (1ULL << 1)
+#define LANDLOCK_ACTION_FS_READ (1ULL << 2)
+#define LANDLOCK_ACTION_FS_NEW (1ULL << 3)
+#define LANDLOCK_ACTION_FS_GET (1ULL << 4)
+#define LANDLOCK_ACTION_FS_REMOVE (1ULL << 5)
+#define LANDLOCK_ACTION_FS_IOCTL (1ULL << 6)
+#define LANDLOCK_ACTION_FS_LOCK (1ULL << 7)
+#define LANDLOCK_ACTION_FS_FCNTL (1ULL << 8)
+#define _LANDLOCK_ACTION_FS_NB 9
+#define _LANDLOCK_ACTION_FS_MASK ((1ULL <<
_LANDLOCK_ACTION_FS_NB) - 1)
+
+
+/**
+ * struct landlock_context - context accessible to a Landlock rule
+ *
+ * @status: bitfield for future use (LANDLOCK_SUBTYPE_STATUS_*)
+ * @arch: indicates system call convention as an AUDIT_ARCH_* value
+ * as defined in <linux/audit.h>
+ * @syscall_nr: the system call number called by the current process (may be
+ * useful to debug: find out from which syscall this request came
+ * from)
+ * @syscall_cmd: contains the command used by a multiplexer syscall (e.g.
+ * ioctl, fcntl, flock)
+ * @event: event type (&enum landlock_subtype_event)
+ * @arg1: event's first optional argument
+ * @arg2: event's second optional argument
+ */
+struct landlock_context {
+ __u64 status;
+ __u32 arch;
+ __u32 syscall_nr;
+ __u32 syscall_cmd;
+ __u32 event;
+ __u64 arg1;
+ __u64 arg2;
+};
+
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/security/Kconfig b/security/Kconfig
index d900f47eaa68..fb9eb0ac1ee4 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -199,6 +199,7 @@ source security/tomoyo/Kconfig
source security/apparmor/Kconfig
source security/loadpin/Kconfig
source security/yama/Kconfig
+source security/landlock/Kconfig
source security/integrity/Kconfig
diff --git a/security/Makefile b/security/Makefile
index f2d71cdb8e19..3fdc2f19dc48 100644
--- a/security/Makefile
+++ b/security/Makefile
@@ -9,6 +9,7 @@ subdir-$(CONFIG_SECURITY_TOMOYO) += tomoyo
subdir-$(CONFIG_SECURITY_APPARMOR) += apparmor
subdir-$(CONFIG_SECURITY_YAMA) += yama
subdir-$(CONFIG_SECURITY_LOADPIN) += loadpin
+subdir-$(CONFIG_SECURITY_LANDLOCK) += landlock
# always enable default capabilities
obj-y += commoncap.o
@@ -24,6 +25,7 @@ obj-$(CONFIG_SECURITY_TOMOYO) += tomoyo/
obj-$(CONFIG_SECURITY_APPARMOR) += apparmor/
obj-$(CONFIG_SECURITY_YAMA) += yama/
obj-$(CONFIG_SECURITY_LOADPIN) += loadpin/
+obj-$(CONFIG_SECURITY_LANDLOCK) += landlock/
obj-$(CONFIG_CGROUP_DEVICE) += device_cgroup.o
# Object integrity file lists
diff --git a/security/landlock/Kconfig b/security/landlock/Kconfig
new file mode 100644
index 000000000000..aa5808e116f1
--- /dev/null
+++ b/security/landlock/Kconfig
@@ -0,0 +1,18 @@
+config SECURITY_LANDLOCK
+ bool "Landlock sandbox support"
+ depends on SECURITY
+ depends on BPF_SYSCALL
+ depends on SECCOMP_FILTER
+ default y
+ help
+ Landlock is a stackable LSM which allows to load a security policy to
+ restrict processes (i.e. create a sandbox). The policy is a list of
+ stacked eBPF programs, called rules, dedicated to restrict access to
+ a type of kernel object (e.g. file).
+
+ You need to enable seccomp filter to apply a security policy to a
+ process hierarchy (e.g. application with built-in sandboxing).
+
+ See Documentation/security/landlock/ for further information.
+
+ If you are unsure how to answer this question, answer Y.
diff --git a/security/landlock/Makefile b/security/landlock/Makefile
new file mode 100644
index 000000000000..7205f9a7a2ee
--- /dev/null
+++ b/security/landlock/Makefile
@@ -0,0 +1,3 @@
+obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
+
+landlock-y := init.o
diff --git a/security/landlock/common.h b/security/landlock/common.h
new file mode 100644
index 000000000000..a2483405349f
--- /dev/null
+++ b/security/landlock/common.h
@@ -0,0 +1,25 @@
+/*
+ * Landlock LSM - private headers
+ *
+ * Copyright © 2017 Mickaël Salaün <m...@digikod.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef _SECURITY_LANDLOCK_COMMON_H
+#define _SECURITY_LANDLOCK_COMMON_H
+
+/**
+ * get_index - get an index for the rules of struct landlock_events
+ *
+ * @event: a Landlock event type
+ */
+static inline int get_index(enum landlock_subtype_event event)
+{
+ /* event ID > 0 for loaded programs */
+ return event - 1;
+}
+
+#endif /* _SECURITY_LANDLOCK_COMMON_H */
diff --git a/security/landlock/init.c b/security/landlock/init.c
new file mode 100644
index 000000000000..0a97026f1c07
--- /dev/null
+++ b/security/landlock/init.c
@@ -0,0 +1,123 @@
+/*
+ * Landlock LSM - init
+ *
+ * Copyright © 2017 Mickaël Salaün <m...@digikod.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/bpf.h> /* enum bpf_access_type */
+#include <linux/capability.h> /* capable */
+#include <linux/landlock.h> /* LANDLOCK_VERSION */
+
+
+static inline bool bpf_landlock_is_valid_access(int off, int size,
+ enum bpf_access_type type, enum bpf_reg_type *reg_type,
+ union bpf_prog_subtype *prog_subtype)
+{
+ if (WARN_ON(!prog_subtype))
+ return false;
+
+ switch (prog_subtype->landlock_rule.event) {
+ case LANDLOCK_SUBTYPE_EVENT_FS:
+ case LANDLOCK_SUBTYPE_EVENT_UNSPEC:
+ default:
+ return false;
+ }
+}
+
+static inline bool bpf_landlock_is_valid_subtype(
+ union bpf_prog_subtype *prog_subtype)
+{
+ if (WARN_ON(!prog_subtype))
+ return false;
+
+ switch (prog_subtype->landlock_rule.event) {
+ case LANDLOCK_SUBTYPE_EVENT_FS:
+ break;
+ case LANDLOCK_SUBTYPE_EVENT_UNSPEC:
+ default:
+ return false;
+ }
+
+ if (!prog_subtype->landlock_rule.version ||
+ prog_subtype->landlock_rule.version > LANDLOCK_VERSION)
+ return false;
+ if (!prog_subtype->landlock_rule.event ||
+ prog_subtype->landlock_rule.event >
_LANDLOCK_SUBTYPE_EVENT_LAST)
+ return false;
+ if (prog_subtype->landlock_rule.ability &
~_LANDLOCK_SUBTYPE_ABILITY_MASK)
+ return false;
+ if (prog_subtype->landlock_rule.option & ~_LANDLOCK_SUBTYPE_OPTION_MASK)
+ return false;
+
+ /* check ability flags */
+ if (prog_subtype->landlock_rule.ability &
LANDLOCK_SUBTYPE_ABILITY_WRITE &&
+ !capable(CAP_SYS_ADMIN))
+ return false;
+ if (prog_subtype->landlock_rule.ability &
LANDLOCK_SUBTYPE_ABILITY_DEBUG &&
+ !capable(CAP_SYS_ADMIN))
+ return false;
+
+ return true;
+}
+
+static inline const struct bpf_func_proto *bpf_landlock_func_proto(
+ enum bpf_func_id func_id, union bpf_prog_subtype *prog_subtype)
+{
+ bool event_fs = (prog_subtype->landlock_rule.event ==
+ LANDLOCK_SUBTYPE_EVENT_FS);
+ bool ability_write = !!(prog_subtype->landlock_rule.ability &
+ LANDLOCK_SUBTYPE_ABILITY_WRITE);
+ bool ability_debug = !!(prog_subtype->landlock_rule.ability &
+ LANDLOCK_SUBTYPE_ABILITY_DEBUG);
+
+ switch (func_id) {
+ case BPF_FUNC_map_lookup_elem:
+ return &bpf_map_lookup_elem_proto;
+
+ /* ability_write */
+ case BPF_FUNC_map_delete_elem:
+ if (ability_write)
+ return &bpf_map_delete_elem_proto;
+ return NULL;
+ case BPF_FUNC_map_update_elem:
+ if (ability_write)
+ return &bpf_map_update_elem_proto;
+ return NULL;
+
+ /* ability_debug */
+ case BPF_FUNC_get_current_comm:
+ if (ability_debug)
+ return &bpf_get_current_comm_proto;
+ return NULL;
+ case BPF_FUNC_get_current_pid_tgid:
+ if (ability_debug)
+ return &bpf_get_current_pid_tgid_proto;
+ return NULL;
+ case BPF_FUNC_get_current_uid_gid:
+ if (ability_debug)
+ return &bpf_get_current_uid_gid_proto;
+ return NULL;
+ case BPF_FUNC_trace_printk:
+ if (ability_debug)
+ return bpf_get_trace_printk_proto();
+ return NULL;
+
+ default:
+ return NULL;
+ }
+}
+
+static const struct bpf_verifier_ops bpf_landlock_ops = {
+ .get_func_proto = bpf_landlock_func_proto,
+ .is_valid_access = bpf_landlock_is_valid_access,
+ .is_valid_subtype = bpf_landlock_is_valid_subtype,
+};
+
+static struct bpf_prog_type_list bpf_landlock_type __ro_after_init = {
+ .ops = &bpf_landlock_ops,
+ .type = BPF_PROG_TYPE_LANDLOCK,
+};
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 725c9a7d3dd9..cdb13134f522 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -114,6 +114,7 @@ enum bpf_prog_type {
BPF_PROG_TYPE_LWT_IN,
BPF_PROG_TYPE_LWT_OUT,
BPF_PROG_TYPE_LWT_XMIT,
+ BPF_PROG_TYPE_LANDLOCK,
};
enum bpf_attach_type {
@@ -649,4 +650,108 @@ struct xdp_md {
__u32 data_end;
};
+/**
+ * enum landlock_subtype_event - event occurring when an action is performed on
+ * a particular kernel object
+ *
+ * An event is a policy decision point which exposes the same context type
+ * (especially the same arg[0-9] field types) for each rule execution.
+ *
+ * @LANDLOCK_SUBTYPE_EVENT_UNSPEC: invalid value
+ * @LANDLOCK_SUBTYPE_EVENT_FS: generic filesystem event
+ */
+enum landlock_subtype_event {
+ LANDLOCK_SUBTYPE_EVENT_UNSPEC,
+ LANDLOCK_SUBTYPE_EVENT_FS,
+};
+#define _LANDLOCK_SUBTYPE_EVENT_LAST LANDLOCK_SUBTYPE_EVENT_FS
+
+/**
+ * DOC: landlock_subtype_access
+ *
+ * eBPF context and functions allowed for a rule
+ *
+ * - LANDLOCK_SUBTYPE_ABILITY_WRITE: allows to directly send notification to
+ * userland (e.g. through a map), which may leaks sensitive information
+ * - LANDLOCK_SUBTYPE_ABILITY_DEBUG: allows to do debug actions (e.g. writing
+ * logs), which may be dangerous and should only be used for rule testing
+ */
+#define LANDLOCK_SUBTYPE_ABILITY_WRITE (1ULL << 0)
+#define LANDLOCK_SUBTYPE_ABILITY_DEBUG (1ULL << 1)
+#define _LANDLOCK_SUBTYPE_ABILITY_NB 2
+#define _LANDLOCK_SUBTYPE_ABILITY_MASK ((1ULL <<
_LANDLOCK_SUBTYPE_ABILITY_NB) - 1)
+
+/*
+ * Future options for a Landlock rule (e.g. run even if a previous rule denied
+ * an action).
+ */
+#define _LANDLOCK_SUBTYPE_OPTION_NB 0
+#define _LANDLOCK_SUBTYPE_OPTION_MASK ((1ULL <<
_LANDLOCK_SUBTYPE_OPTION_NB) - 1)
+
+/*
+ * Status visible in the @status field of a context (e.g. already called in
+ * this syscall session, with same args...).
+ *
+ * The @status field exposed to a rule shall depend on the rule version.
+ */
+#define _LANDLOCK_SUBTYPE_STATUS_NB 0
+#define _LANDLOCK_SUBTYPE_STATUS_MASK ((1ULL <<
_LANDLOCK_SUBTYPE_STATUS_NB) - 1)
+
+/**
+ * DOC: landlock_action_fs
+ *
+ * - %LANDLOCK_ACTION_FS_EXEC: execute a file or walk through a directory
+ * - %LANDLOCK_ACTION_FS_WRITE: modify a file or a directory view (which
+ * include mount actions)
+ * - %LANDLOCK_ACTION_FS_READ: read a file or a directory
+ * - %LANDLOCK_ACTION_FS_NEW: create a file or a directory
+ * - %LANDLOCK_ACTION_FS_GET: open or receive a file
+ * - %LANDLOCK_ACTION_FS_REMOVE: unlink a file or remove a directory
+ *
+ * Each of the following actions are specific to syscall multiplexers. They
+ * fill the syscall_cmd field from &struct landlock_context with their custom
+ * command.
+ *
+ * - %LANDLOCK_ACTION_FS_IOCTL: ioctl command
+ * - %LANDLOCK_ACTION_FS_LOCK: flock or fcntl lock command
+ * - %LANDLOCK_ACTION_FS_FCNTL: fcntl command
+ */
+#define LANDLOCK_ACTION_FS_EXEC (1ULL << 0)
+#define LANDLOCK_ACTION_FS_WRITE (1ULL << 1)
+#define LANDLOCK_ACTION_FS_READ (1ULL << 2)
+#define LANDLOCK_ACTION_FS_NEW (1ULL << 3)
+#define LANDLOCK_ACTION_FS_GET (1ULL << 4)
+#define LANDLOCK_ACTION_FS_REMOVE (1ULL << 5)
+#define LANDLOCK_ACTION_FS_IOCTL (1ULL << 6)
+#define LANDLOCK_ACTION_FS_LOCK (1ULL << 7)
+#define LANDLOCK_ACTION_FS_FCNTL (1ULL << 8)
+#define _LANDLOCK_ACTION_FS_NB 9
+#define _LANDLOCK_ACTION_FS_MASK ((1ULL <<
_LANDLOCK_ACTION_FS_NB) - 1)
+
+
+/**
+ * struct landlock_context - context accessible to a Landlock rule
+ *
+ * @status: bitfield for future use (LANDLOCK_SUBTYPE_STATUS_*)
+ * @arch: indicates system call convention as an AUDIT_ARCH_* value
+ * as defined in <linux/audit.h>
+ * @syscall_nr: the system call number called by the current process (may be
+ * useful to debug: find out from which syscall this request came
+ * from)
+ * @syscall_cmd: contains the command used by a multiplexer syscall (e.g.
+ * ioctl, fcntl, flock)
+ * @event: event type (&enum landlock_subtype_event)
+ * @arg1: event's first optional argument
+ * @arg2: event's second optional argument
+ */
+struct landlock_context {
+ __u64 status;
+ __u32 arch;
+ __u32 syscall_nr;
+ __u32 syscall_cmd;
+ __u32 event;
+ __u64 arg1;
+ __u64 arg2;
+};
+
#endif /* _UAPI__LINUX_BPF_H__ */
--
2.11.0
