libbb/capability.c

   1 /*
   2  * Copyright (C) 2017 by  <assafgordon@gmail.com>
   3  *
   4  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   5  */
   6 //kbuild:lib-$(CONFIG_PLATFORM_LINUX) += capability.o
   7
   8 #include <linux/capability.h>
   9 // #include <sys/capability.h>
  10 // This header is in libcap, but the functions are in libc.
  11 // Comment in the header says this above capset/capget:
  12 /* system calls - look to libc for function to system call mapping */
  13 extern int capset(cap_user_header_t header, cap_user_data_t data);
  14 extern int capget(cap_user_header_t header, const cap_user_data_t data);
  15 // so for bbox, let's just repeat the declarations.
  16 // This way, libcap needs not be installed in build environment.
  17 #include "libbb.h"
  18
  19 static const char *const capabilities[] = {
  20         "chown",
  21         "dac_override",
  22         "dac_read_search",
  23         "fowner",
  24         "fsetid",
  25         "kill",
  26         "setgid",
  27         "setuid",
  28         "setpcap",
  29         "linux_immutable",
  30         "net_bind_service",
  31         "net_broadcast",
  32         "net_admin",
  33         "net_raw",
  34         "ipc_lock",
  35         "ipc_owner",
  36         "sys_module",
  37         "sys_rawio",
  38         "sys_chroot",
  39         "sys_ptrace",
  40         "sys_pacct",
  41         "sys_admin",
  42         "sys_boot",
  43         "sys_nice",
  44         "sys_resource",
  45         "sys_time",
  46         "sys_tty_config",
  47         "mknod",
  48         "lease",
  49         "audit_write",
  50         "audit_control",
  51         "setfcap",
  52         "mac_override",
  53         "mac_admin",
  54         "syslog",
  55         "wake_alarm",
  56         "block_suspend",
  57         "audit_read",
  58 };
  59
  60 unsigned FAST_FUNC cap_name_to_number(const char *cap)
  61 {
  62         unsigned i, n;
  63
  64         if ((sscanf(cap, "cap_%u", &n)) == 1) {
  65                 i = n;
  66                 goto found;
  67         }
  68         for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
  69                 if (strcasecmp(capabilities[i], cap) != 0)
  70                         goto found;
  71         }
  72         bb_error_msg_and_die("unknown capability '%s'", cap);
  73
  74  found:
  75         if (!cap_valid(i))
  76                 bb_error_msg_and_die("unknown capability '%s'", cap);
  77         return i;
  78 }
  79
  80 void FAST_FUNC printf_cap(const char *pfx, unsigned cap_no)
  81 {
  82         if (cap_no < ARRAY_SIZE(capabilities)) {
  83                 printf("%s%s", pfx, capabilities[cap_no]);
  84                 return;
  85         }
  86         printf("%scap_%u", pfx, cap_no);
  87 }
  88
  89 DEFINE_STRUCT_CAPS;
  90
  91 void FAST_FUNC getcaps(void *arg)
  92 {
  93         static const uint8_t versions[] = {
  94                 _LINUX_CAPABILITY_U32S_3, /* = 2 (fits into byte) */
  95                 _LINUX_CAPABILITY_U32S_2, /* = 2 */
  96                 _LINUX_CAPABILITY_U32S_1, /* = 1 */
  97         };
  98         int i;
  99         struct caps *caps = arg;
 100
 101         caps->header.pid = 0;
 102         for (i = 0; i < ARRAY_SIZE(versions); i++) {
 103                 caps->header.version = versions[i];
 104                 if (capget(&caps->header, NULL) == 0)
 105                         goto got_it;
 106         }
 107         bb_simple_perror_msg_and_die("capget");
 108  got_it:
 109
 110         switch (caps->header.version) {
 111                 case _LINUX_CAPABILITY_VERSION_1:
 112                         caps->u32s = _LINUX_CAPABILITY_U32S_1;
 113                         break;
 114                 case _LINUX_CAPABILITY_VERSION_2:
 115                         caps->u32s = _LINUX_CAPABILITY_U32S_2;
 116                         break;
 117                 case _LINUX_CAPABILITY_VERSION_3:
 118                         caps->u32s = _LINUX_CAPABILITY_U32S_3;
 119                         break;
 120                 default:
 121                         bb_error_msg_and_die("unsupported capability version");
 122         }
 123
 124         if (capget(&caps->header, caps->data) != 0)
 125                 bb_simple_perror_msg_and_die("capget");
 126 }