On 24/08/2017 04:28, Alexei Starovoitov wrote: > On Mon, Aug 21, 2017 at 02:09:26AM +0200, Mickaël Salaün 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. >> >> Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> >> Cc: Alexei Starovoitov <ast@xxxxxxxxxx> >> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> >> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx> >> Cc: David S. Miller <davem@xxxxxxxxxxxxx> >> Cc: James Morris <james.l.morris@xxxxxxxxxx> >> Cc: Kees Cook <keescook@xxxxxxxxxxxx> >> Cc: Serge E. Hallyn <serge@xxxxxxxxxx> >> --- >> >> Changes since v6: >> * add 3 more sub-events: IOCTL, LOCK, FCNTL >> https://lkml.kernel.org/r/2fbc99a6-f190-f335-bd14-04bdeed35571@xxxxxxxxxxx >> * rename LANDLOCK_VERSION to LANDLOCK_ABI to better reflect its purpose, >> and move it from landlock.h to common.h >> * rename BPF_PROG_TYPE_LANDLOCK to BPF_PROG_TYPE_LANDLOCK_RULE: an eBPF >> program could be used for something else than a rule >> * simplify struct landlock_context by removing the arch and syscall_nr fields >> * remove all eBPF map functions call, remove ABILITY_WRITE >> * refactor bpf_landlock_func_proto() (suggested by Kees Cook) >> * constify pointers >> * fix doc inclusion >> >> 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 >> --- >> include/linux/bpf_types.h | 3 ++ >> include/uapi/linux/bpf.h | 97 +++++++++++++++++++++++++++++++++++++++++ >> security/Kconfig | 1 + >> security/Makefile | 2 + >> security/landlock/Kconfig | 18 ++++++++ >> security/landlock/Makefile | 3 ++ >> security/landlock/common.h | 21 +++++++++ >> security/landlock/init.c | 98 ++++++++++++++++++++++++++++++++++++++++++ >> tools/include/uapi/linux/bpf.h | 97 +++++++++++++++++++++++++++++++++++++++++ >> 9 files changed, 340 insertions(+) >> 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/bpf_types.h b/include/linux/bpf_types.h >> index 6f1a567667b8..8bac93970a47 100644 >> --- a/include/linux/bpf_types.h >> +++ b/include/linux/bpf_types.h >> @@ -18,6 +18,9 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe_prog_ops) >> BPF_PROG_TYPE(BPF_PROG_TYPE_TRACEPOINT, tracepoint_prog_ops) >> BPF_PROG_TYPE(BPF_PROG_TYPE_PERF_EVENT, perf_event_prog_ops) >> #endif >> +#ifdef CONFIG_SECURITY_LANDLOCK >> +BPF_PROG_TYPE(BPF_PROG_TYPE_LANDLOCK_RULE, bpf_landlock_ops) >> +#endif >> >> BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops) >> BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops) >> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h >> index 8541ab85e432..20da634da941 100644 >> --- a/include/uapi/linux/bpf.h >> +++ b/include/uapi/linux/bpf.h >> @@ -129,6 +129,7 @@ enum bpf_prog_type { >> BPF_PROG_TYPE_LWT_XMIT, >> BPF_PROG_TYPE_SOCK_OPS, >> BPF_PROG_TYPE_SK_SKB, >> + BPF_PROG_TYPE_LANDLOCK_RULE, >> }; >> >> enum bpf_attach_type { >> @@ -879,4 +880,100 @@ enum { >> #define TCP_BPF_IW 1001 /* Set TCP initial congestion window */ >> #define TCP_BPF_SNDCWND_CLAMP 1002 /* Set sndcwnd_clamp */ >> >> +/** >> + * 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 >> + * @LANDLOCK_SUBTYPE_EVENT_FS_IOCTL: custom IOCTL sub-event >> + * @LANDLOCK_SUBTYPE_EVENT_FS_LOCK: custom LOCK sub-event >> + * @LANDLOCK_SUBTYPE_EVENT_FS_FCNTL: custom FCNTL sub-event >> + */ >> +enum landlock_subtype_event { >> + LANDLOCK_SUBTYPE_EVENT_UNSPEC, >> + LANDLOCK_SUBTYPE_EVENT_FS, >> + LANDLOCK_SUBTYPE_EVENT_FS_IOCTL, >> + LANDLOCK_SUBTYPE_EVENT_FS_LOCK, >> + LANDLOCK_SUBTYPE_EVENT_FS_FCNTL, >> +}; >> +#define _LANDLOCK_SUBTYPE_EVENT_LAST LANDLOCK_SUBTYPE_EVENT_FS_FCNTL >> + >> +/** >> + * DOC: landlock_subtype_ability >> + * >> + * eBPF context and functions allowed for a rule >> + * >> + * - 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_DEBUG (1ULL << 0) >> +#define _LANDLOCK_SUBTYPE_ABILITY_NB 1 >> +#define _LANDLOCK_SUBTYPE_ABILITY_MASK ((1ULL << _LANDLOCK_SUBTYPE_ABILITY_NB) - 1) > > can you move the last two macros out of uapi? > There is really no need for the implementation details to > leak into uapi. Right, I'll move them. > >> + >> +/* >> + * 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) > > same here > >> + >> +/* >> + * 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) > > and here > >> + >> +/** >> + * 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. Each of >> + * them trigger a dedicated Landlock event where their command can be read. >> + * >> + * - %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) > > and here > >> + >> + >> +/** >> + * struct landlock_context - context accessible to a Landlock rule >> + * >> + * @status: bitfield for future use (LANDLOCK_SUBTYPE_STATUS_*) >> + * @event: event type (&enum landlock_subtype_event) >> + * @arg1: event's first optional argument >> + * @arg2: event's second optional argument >> + */ >> +struct landlock_context { >> + __u64 status; >> + __u64 event; >> + __u64 arg1; >> + __u64 arg2; >> +}; > > looking at all the uapi additions.. probably worth moving them > into separate .h like we did with bpf_perf_event.h > How about include/uapi/linux/landlock.h ? > It can include bpf.h first thing and then the rest of > landlock related bits. > so all, but BPF_PROG_TYPE_LANDLOCK_RULE will go there. Sounds good. > >> +++ 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 > > all new features need to start with default n OK > >> +static inline const struct bpf_func_proto *bpf_landlock_func_proto( >> + enum bpf_func_id func_id, >> + const union bpf_prog_subtype *prog_subtype) >> +{ >> + /* generic functions */ >> + if (prog_subtype->landlock_rule.ability & >> + LANDLOCK_SUBTYPE_ABILITY_DEBUG) { >> + switch (func_id) { >> + case BPF_FUNC_get_current_comm: >> + return &bpf_get_current_comm_proto; >> + case BPF_FUNC_get_current_pid_tgid: >> + return &bpf_get_current_pid_tgid_proto; >> + case BPF_FUNC_get_current_uid_gid: >> + return &bpf_get_current_uid_gid_proto; > > why current_*() helpers are 'debug' only? This helpers should not be needed for access control. It sounds like a really bad idea to rely on a command name, a PID or even the UID, especially for a kind of hierarchy-based access control like Landlock. I want to avoid people from using these features except for debug purposes. This could be changed in the future if there is a legitimate use case of some of these features, though.
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