[PATCH net-next v6 02/11] bpf,landlock: Define an eBPF program type for Landlock
From: mic@digikod.net (Mickaël Salaün)
Date: 2017-04-16 21:58:48
Also in:
linux-api, lkml, netdev
On 29/03/2017 01:46, Micka?l Sala?n wrote:
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: Micka?l Sala?n <mic@digikod.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: James Morris <redacted>
Cc: Kees Cook <redacted>
Cc: Serge E. Hallyn <serge@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[...]
quoted hunk ↗ jump to hunk
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_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;
+};
I plan to simplify and make the FS event more generic for the IOCTL,
LOCK or FCNTL actions. The action flags for the
LANDLOCK_SUBTYPE_EVENT_FS event will remain the same but the syscall_cmd
field will be removed from struct landlock_context. Instead, one of
three dedicated events will be triggered in addition to one of this
three multiplexed actions.
The aim is to trigger the LANDLOCK_SUBTYPE_EVENT_FS for all file system
events (still including IOCTL/LOCK/FCNTL actions). This should avoid a
developer/user to forget such actions. However, when this kind of action
is triggered, a LANDLOCK_SUBTYPE_EVENT_FS_{IOCTL,LOCK,FCNTL} event will
follow. This enable to simplify the struct landlock_context while still
having it as generic as possible. The difference will be that the arg2
field for one of the LANDLOCK_SUBTYPE_EVENT_FS_{IOCTL,LOCK,FCNTL} events
will contain a custom IOCTL, LOCK or FCNTL command (currently in the
syscall_cmd field) instead of a LANDLOCK_ACTION_FS_* value. The same
logic could be used to tighten other actions in the future.
The HOOK_NEW_FS_CMD(...) from [04/11]:security/landlock/hooks_fs.c will
be replaced with dedicated calls.
I also plan to remove the arch and syscall_nr fields. This will make
struct landlock_context even more simple and arch-independent.
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