util-linux/setpriv.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * setpriv implementation for busybox based on linux-utils-ng 2.29
   4  *
   5  * Copyright (C) 2017 by  <assafgordon@gmail.com>
   6  *
   7  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8  */
   9 //config:config SETPRIV
  10 //config:       bool "setpriv (3.4 kb)"
  11 //config:       default y
  12 //config:       select PLATFORM_LINUX
  13 //config:       select LONG_OPTS
  14 //config:       help
  15 //config:       Run a program with different Linux privilege settings.
  16 //config:       Requires kernel >= 3.5
  17 //config:
  18 //config:config FEATURE_SETPRIV_DUMP
  19 //config:       bool "Support dumping current privilege state"
  20 //config:       default y
  21 //config:       depends on SETPRIV
  22 //config:       help
  23 //config:       Enables the "--dump" switch to print out the current privilege
  24 //config:       state. This is helpful for diagnosing problems.
  25 //config:
  26 //config:config FEATURE_SETPRIV_CAPABILITIES
  27 //config:       bool "Support capabilities"
  28 //config:       default y
  29 //config:       depends on SETPRIV
  30 //config:       help
  31 //config:       Capabilities can be used to grant processes additional rights
  32 //config:       without the necessity to always execute as the root user.
  33 //config:       Enabling this option enables "--dump" to show information on
  34 //config:       capabilities.
  35 //config:
  36 //config:config FEATURE_SETPRIV_CAPABILITY_NAMES
  37 //config:       bool "Support capability names"
  38 //config:       default y
  39 //config:       depends on SETPRIV && FEATURE_SETPRIV_CAPABILITIES
  40 //config:       help
  41 //config:       Capabilities can be either referenced via a human-readble name,
  42 //config:       e.g. "net_admin", or using their index, e.g. "cap_12". Enabling
  43 //config:       this option allows using the human-readable names in addition to
  44 //config:       the index-based names.
  45
  46 //applet:IF_SETPRIV(APPLET(setpriv, BB_DIR_BIN, BB_SUID_DROP))
  47
  48 //kbuild:lib-$(CONFIG_SETPRIV) += setpriv.o
  49
  50 //usage:#define setpriv_trivial_usage
  51 //usage:        "[OPTIONS] PROG [ARGS]"
  52 //usage:#define setpriv_full_usage "\n\n"
  53 //usage:       "Run PROG with different privilege settings\n"
  54 //usage:        IF_FEATURE_SETPRIV_DUMP(
  55 //usage:     "\n-d,--dump               Show current capabilities"
  56 //usage:        )
  57 //usage:     "\n--nnp,--no-new-privs    Ignore setuid/setgid bits and file capabilities"
  58 //usage:        IF_FEATURE_SETPRIV_CAPABILITIES(
  59 //usage:     "\n--inh-caps CAP,CAP      Set inheritable capabilities"
  60 //usage:     "\n--ambient-caps CAP,CAP  Set ambient capabilities"
  61 //usage:        )
  62
  63 //setpriv from util-linux 2.28:
  64 // -d, --dump               show current state (and do not exec anything)
  65 // --nnp, --no-new-privs    disallow granting new privileges
  66 // --inh-caps <caps,...>    set inheritable capabilities
  67 // --bounding-set <caps>    set capability bounding set
  68 // --ruid <uid>             set real uid
  69 // --euid <uid>             set effective uid
  70 // --rgid <gid>             set real gid
  71 // --egid <gid>             set effective gid
  72 // --reuid <uid>            set real and effective uid
  73 // --regid <gid>            set real and effective gid
  74 // --clear-groups           clear supplementary groups
  75 // --keep-groups            keep supplementary groups
  76 // --groups <group,...>     set supplementary groups
  77 // --securebits <bits>      set securebits
  78 // --selinux-label <label>  set SELinux label
  79 // --apparmor-profile <pr>  set AppArmor profile
  80
  81 #if ENABLE_FEATURE_SETPRIV_CAPABILITIES
  82 #include <linux/capability.h>
  83 // #include <sys/capability.h>
  84 // This header is in libcap, but the functions are in libc.
  85 // Comment in the header says this above capset/capget:
  86 /* system calls - look to libc for function to system call mapping */
  87 extern int capset(cap_user_header_t header, cap_user_data_t data);
  88 extern int capget(cap_user_header_t header, const cap_user_data_t data);
  89 // so for bbox, let's just repeat the declarations.
  90 // This way, libcap needs not be installed in build environment.
  91 #endif
  92 #include <sys/prctl.h>
  93 #include "libbb.h"
  94
  95 #ifndef PR_CAPBSET_READ
  96 #define PR_CAPBSET_READ 23
  97 #endif
  98
  99 #ifndef PR_SET_NO_NEW_PRIVS
 100 #define PR_SET_NO_NEW_PRIVS 38
 101 #endif
 102
 103 #ifndef PR_GET_NO_NEW_PRIVS
 104 #define PR_GET_NO_NEW_PRIVS 39
 105 #endif
 106
 107 #ifndef PR_CAP_AMBIENT
 108 #define PR_CAP_AMBIENT 47
 109 #define PR_CAP_AMBIENT_IS_SET 1
 110 #define PR_CAP_AMBIENT_RAISE 2
 111 #define PR_CAP_AMBIENT_LOWER 3
 112 #endif
 113
 114 enum {
 115         IF_FEATURE_SETPRIV_DUMP(OPTBIT_DUMP,)
 116         IF_FEATURE_SETPRIV_CAPABILITIES(OPTBIT_INH,)
 117         IF_FEATURE_SETPRIV_CAPABILITIES(OPTBIT_AMB,)
 118         OPTBIT_NNP,
 119
 120         IF_FEATURE_SETPRIV_DUMP(OPT_DUMP = (1 << OPTBIT_DUMP),)
 121         IF_FEATURE_SETPRIV_CAPABILITIES(OPT_INH  = (1 << OPTBIT_INH),)
 122         IF_FEATURE_SETPRIV_CAPABILITIES(OPT_AMB  = (1 << OPTBIT_AMB),)
 123         OPT_NNP  = (1 << OPTBIT_NNP),
 124 };
 125
 126 #if ENABLE_FEATURE_SETPRIV_CAPABILITIES
 127 DEFINE_STRUCT_CAPS;
 128
 129 static unsigned parse_cap(const char *cap)
 130 {
 131         switch (cap[0]) {
 132         case '-':
 133                 break;
 134         case '+':
 135                 break;
 136         default:
 137                 bb_error_msg_and_die("invalid capability '%s'", cap);
 138                 break;
 139         }
 140
 141         cap++;
 142         return cap_name_to_number(cap);
 143 }
 144
 145 static void set_inh_caps(char *capstring)
 146 {
 147         struct caps caps;
 148
 149         getcaps(&caps);
 150
 151         capstring = strtok(capstring, ",");
 152         while (capstring) {
 153                 unsigned cap;
 154
 155                 cap = parse_cap(capstring);
 156                 if (CAP_TO_INDEX(cap) >= caps.u32s)
 157                         bb_error_msg_and_die("invalid capability '%s'", capstring);
 158
 159                 if (capstring[0] == '+')
 160                         caps.data[CAP_TO_INDEX(cap)].inheritable |= CAP_TO_MASK(cap);
 161                 else
 162                         caps.data[CAP_TO_INDEX(cap)].inheritable &= ~CAP_TO_MASK(cap);
 163                 capstring = strtok(NULL, ",");
 164         }
 165
 166         if (capset(&caps.header, caps.data) != 0)
 167                 bb_perror_msg_and_die("capset");
 168 }
 169
 170 static void set_ambient_caps(char *string)
 171 {
 172         char *cap;
 173
 174         cap = strtok(string, ",");
 175         while (cap) {
 176                 unsigned idx;
 177
 178                 idx = parse_cap(cap);
 179                 if (cap[0] == '+') {
 180                         if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, idx, 0, 0) < 0)
 181                                 bb_perror_msg("cap_ambient_raise");
 182                 } else {
 183                         if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_LOWER, idx, 0, 0) < 0)
 184                                 bb_perror_msg("cap_ambient_lower");
 185                 }
 186                 cap = strtok(NULL, ",");
 187         }
 188 }
 189 #endif /* FEATURE_SETPRIV_CAPABILITIES */
 190
 191 #if ENABLE_FEATURE_SETPRIV_DUMP
 192 # if !ENABLE_FEATURE_SETPRIV_CAPABILITY_NAMES
 193 #  define printf_cap(pfx, cap_no) printf("%scap_%u", (pfx), (cap_no))
 194 # endif
 195
 196 static int dump(void)
 197 {
 198         IF_FEATURE_SETPRIV_CAPABILITIES(struct caps caps;)
 199         const char *fmt;
 200         uid_t ruid, euid, suid;
 201         gid_t rgid, egid, sgid;
 202         gid_t *gids;
 203         int i, ngids, nnp;
 204
 205         getresuid(&ruid, &euid, &suid); /* never fails in Linux */
 206         getresgid(&rgid, &egid, &sgid); /* never fails in Linux */
 207         ngids = 0;
 208         gids = bb_getgroups(&ngids, NULL); /* never fails in Linux */
 209
 210         nnp = prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0);
 211         if (nnp < 0)
 212                 bb_perror_msg_and_die("prctl: %s", "GET_NO_NEW_PRIVS");
 213
 214         printf("uid: %u\n", (unsigned)ruid);
 215         printf("euid: %u\n", (unsigned)euid);
 216         printf("gid: %u\n", (unsigned)rgid);
 217         printf("egid: %u\n", (unsigned)egid);
 218
 219         printf("Supplementary groups: ");
 220         if (ngids == 0) {
 221                 printf("[none]");
 222         } else {
 223                 fmt = ",%u" + 1;
 224                 for (i = 0; i < ngids; i++) {
 225                         printf(fmt, (unsigned)gids[i]);
 226                         fmt = ",%u";
 227                 }
 228         }
 229         printf("\nno_new_privs: %d\n", nnp);
 230
 231 # if ENABLE_FEATURE_SETPRIV_CAPABILITIES
 232         getcaps(&caps);
 233         printf("Inheritable capabilities: ");
 234         fmt = "";
 235         for (i = 0; cap_valid(i); i++) {
 236                 unsigned idx = CAP_TO_INDEX(i);
 237                 if (idx >= caps.u32s) {
 238                         printf("\nindex: %u u32s: %u capability: %u\n", idx, caps.u32s, i);
 239                         bb_error_msg_and_die("unsupported capability");
 240                 }
 241                 if (caps.data[idx].inheritable & CAP_TO_MASK(i)) {
 242                         printf_cap(fmt, i);
 243                         fmt = ",";
 244                 }
 245         }
 246         if (!fmt[0])
 247                 printf("[none]");
 248
 249         printf("\nAmbient capabilities: ");
 250         fmt = "";
 251         for (i = 0; cap_valid(i); i++) {
 252                 int ret = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, (unsigned long) i, 0UL, 0UL);
 253                 if (ret < 0)
 254                         bb_perror_msg_and_die("prctl: %s", "CAP_AMBIENT_IS_SET");
 255                 if (ret) {
 256                         printf_cap(fmt, i);
 257                         fmt = ",";
 258                 }
 259         }
 260         if (i == 0)
 261                 printf("[unsupported]");
 262         else if (!fmt[0])
 263                 printf("[none]");
 264
 265         printf("\nCapability bounding set: ");
 266         fmt = "";
 267         for (i = 0; cap_valid(i); i++) {
 268                 int ret = prctl(PR_CAPBSET_READ, (unsigned long) i, 0UL, 0UL, 0UL);
 269                 if (ret < 0)
 270                         bb_perror_msg_and_die("prctl: %s", "CAPBSET_READ");
 271                 if (ret) {
 272                         printf_cap(fmt, i);
 273                         fmt = ",";
 274                 }
 275         }
 276         if (!fmt[0])
 277                 printf("[none]");
 278         bb_putchar('\n');
 279 # endif
 280
 281         if (ENABLE_FEATURE_CLEAN_UP)
 282                 free(gids);
 283
 284         return EXIT_SUCCESS;
 285 }
 286 #endif /* FEATURE_SETPRIV_DUMP */
 287
 288 int setpriv_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 289 int setpriv_main(int argc UNUSED_PARAM, char **argv)
 290 {
 291         static const char setpriv_longopts[] ALIGN1 =
 292                 IF_FEATURE_SETPRIV_DUMP(
 293                 "dump\0"         No_argument            "d"
 294                 )
 295                 "nnp\0"          No_argument            "\xff"
 296                 "no-new-privs\0" No_argument            "\xff"
 297                 IF_FEATURE_SETPRIV_CAPABILITIES(
 298                 "inh-caps\0"     Required_argument      "\xfe"
 299                 "ambient-caps\0" Required_argument      "\xfd"
 300                 )
 301                 ;
 302         int opts;
 303         IF_FEATURE_SETPRIV_CAPABILITIES(char *inh_caps, *ambient_caps;)
 304
 305         opts = getopt32long(argv, "+"
 306                 IF_FEATURE_SETPRIV_DUMP("d")
 307                 IF_FEATURE_SETPRIV_CAPABILITIES("\xfe:\xfd:"),
 308                 setpriv_longopts
 309                 IF_FEATURE_SETPRIV_CAPABILITIES(, &inh_caps, &ambient_caps)
 310         );
 311         argv += optind;
 312
 313 #if ENABLE_FEATURE_SETPRIV_DUMP
 314         if (opts & OPT_DUMP) {
 315                 if (argv[0] || (opts - OPT_DUMP) != 0)
 316                         bb_show_usage();
 317                 return dump();
 318         }
 319 #endif
 320         if (opts & OPT_NNP) {
 321                 if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0))
 322                         bb_perror_msg_and_die("prctl: %s", "SET_NO_NEW_PRIVS");
 323         }
 324
 325 #if ENABLE_FEATURE_SETPRIV_CAPABILITIES
 326         if (opts & OPT_INH)
 327                 set_inh_caps(inh_caps);
 328         if (opts & OPT_AMB)
 329                 set_ambient_caps(ambient_caps);
 330 #endif
 331
 332         if (!argv[0])
 333                 bb_show_usage();
 334         BB_EXECVP_or_die(argv);
 335 }