busybox/libbb/capability.c

/*
 * Copyright (C) 2017 by  <assafgordon@gmail.com>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
//kbuild:lib-$(CONFIG_FEATURE_SETPRIV_CAPABILITIES) += capability.o
//kbuild:lib-$(CONFIG_RUN_INIT) += capability.o

#include <linux/capability.h>
// #include <sys/capability.h>
// This header is in libcap, but the functions are in libc.
// Comment in the header says this above capset/capget:
/* system calls - look to libc for function to system call mapping */
extern int capset(cap_user_header_t header, cap_user_data_t data);
extern int capget(cap_user_header_t header, const cap_user_data_t data);
// so for bbox, let's just repeat the declarations.
// This way, libcap needs not be installed in build environment.
#include "libbb.h"

static const char *const capabilities[] ALIGN_PTR = {
	"chown",
	"dac_override",
	"dac_read_search",
	"fowner",
	"fsetid",
	"kill",
	"setgid",
	"setuid",
	"setpcap",
	"linux_immutable",
	"net_bind_service",
	"net_broadcast",
	"net_admin",
	"net_raw",
	"ipc_lock",
	"ipc_owner",
	"sys_module",
	"sys_rawio",
	"sys_chroot",
	"sys_ptrace",
	"sys_pacct",
	"sys_admin",
	"sys_boot",
	"sys_nice",
	"sys_resource",
	"sys_time",
	"sys_tty_config",
	"mknod",
	"lease",
	"audit_write",
	"audit_control",
	"setfcap",
	"mac_override",
	"mac_admin",
	"syslog",
	"wake_alarm",
	"block_suspend",
	"audit_read",
};

unsigned FAST_FUNC cap_name_to_number(const char *cap)
{
	unsigned i, n;

	if ((sscanf(cap, "cap_%u", &n)) == 1) {
		i = n;
		goto found;
	}
	for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
		if (strcasecmp(capabilities[i], cap) == 0)
			goto found;
	}
	bb_error_msg_and_die("unknown capability '%s'", cap);

 found:
	if (!cap_valid(i))
		bb_error_msg_and_die("unknown capability '%s'", cap);
	return i;
}

void FAST_FUNC printf_cap(const char *pfx, unsigned cap_no)
{
	if (cap_no < ARRAY_SIZE(capabilities)) {
		printf("%s%s", pfx, capabilities[cap_no]);
		return;
	}
	printf("%scap_%u", pfx, cap_no);
}

DEFINE_STRUCT_CAPS;

void FAST_FUNC getcaps(void *arg)
{
	static const uint8_t versions[] = {
		_LINUX_CAPABILITY_U32S_3, /* = 2 (fits into byte) */
		_LINUX_CAPABILITY_U32S_2, /* = 2 */
		_LINUX_CAPABILITY_U32S_1, /* = 1 */
	};
	int i;
	struct caps *caps = arg;

	caps->header.pid = 0;
	for (i = 0; i < ARRAY_SIZE(versions); i++) {
		caps->header.version = versions[i];
		if (capget(&caps->header, NULL) == 0)
			goto got_it;
	}
	bb_simple_perror_msg_and_die("capget");
 got_it:

	switch (caps->header.version) {
		case _LINUX_CAPABILITY_VERSION_1:
			caps->u32s = _LINUX_CAPABILITY_U32S_1;
			break;
		case _LINUX_CAPABILITY_VERSION_2:
			caps->u32s = _LINUX_CAPABILITY_U32S_2;
			break;
		case _LINUX_CAPABILITY_VERSION_3:
			caps->u32s = _LINUX_CAPABILITY_U32S_3;
			break;
		default:
			bb_simple_error_msg_and_die("unsupported capability version");
	}

	if (capget(&caps->header, caps->data) != 0)
		bb_simple_perror_msg_and_die("capget");
}