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) + +/* + * 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. 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) + + +/** + * 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; +}; + #endif /* _UAPI__LINUX_BPF_H__ */ diff --git a/security/Kconfig b/security/Kconfig index e8e449444e65..2dd023c90bcd 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -211,6 +211,7 @@ 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..c82cbd3fb640 --- /dev/null +++ b/security/landlock/common.h @@ -0,0 +1,21 @@ +/* + * Landlock LSM - private headers + * + * Copyright © 2016-2017 Mickaël Salaün <mic@xxxxxxxxxxx> + * + * 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 + +/* + * This is not intended for the UAPI headers. Each userland software should use + * a static minimal ABI for the required features as explained in the + * documentation. + */ +#define LANDLOCK_ABI 1 + +#endif /* _SECURITY_LANDLOCK_COMMON_H */ diff --git a/security/landlock/init.c b/security/landlock/init.c new file mode 100644 index 000000000000..c7922a91aa57 --- /dev/null +++ b/security/landlock/init.c @@ -0,0 +1,98 @@ +/* + * Landlock LSM - init + * + * Copyright © 2016-2017 Mickaël Salaün <mic@xxxxxxxxxxx> + * + * 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 "common.h" /* LANDLOCK_* */ + + +static inline bool bpf_landlock_is_valid_access(int off, int size, + enum bpf_access_type type, struct bpf_insn_access_aux *info, + const 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( + const 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; + } + + /* check Landlock ABI compatibility */ + if (!prog_subtype->landlock_rule.abi || + prog_subtype->landlock_rule.abi > LANDLOCK_ABI) + return false; + /* check if the rule's event, ability and option make sense */ + 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; + + /* the ability to debug requires global CAP_SYS_ADMIN */ + 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, + 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; + case BPF_FUNC_trace_printk: + return bpf_get_trace_printk_proto(); + default: + break; + } + } + return NULL; +} + +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, +}; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 2c0dc9d58ea0..e83bdecf9d27 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/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 { @@ -868,4 +869,100 @@ 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) + +/* + * 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. 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) + + +/** + * 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; +}; + #endif /* _UAPI__LINUX_BPF_H__ */ -- 2.14.1 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
