src/test/test-capability.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <netinet/in.h>
   4 #include <pwd.h>
   5 #include <sys/prctl.h>
   6 #include <sys/socket.h>
   7 #include <sys/wait.h>
   8 #include <unistd.h>
   9
  10 #define TEST_CAPABILITY_C
  11
  12 #include "alloc-util.h"
  13 #include "capability-util.h"
  14 #include "errno-util.h"
  15 #include "fd-util.h"
  16 #include "fileio.h"
  17 #include "macro.h"
  18 #include "missing_prctl.h"
  19 #include "parse-util.h"
  20 #include "string-util.h"
  21 #include "tests.h"
  22
  23 static uid_t test_uid = -1;
  24 static gid_t test_gid = -1;
  25
  26 #if HAS_FEATURE_ADDRESS_SANITIZER
  27 /* Keep CAP_SYS_PTRACE when running under Address Sanitizer */
  28 static const uint64_t test_flags = UINT64_C(1) << CAP_SYS_PTRACE;
  29 #else
  30 /* We keep CAP_DAC_OVERRIDE to avoid errors with gcov when doing test coverage */
  31 static const uint64_t test_flags = UINT64_C(1) << CAP_DAC_OVERRIDE;
  32 #endif
  33
  34 /* verify cap_last_cap() against /proc/sys/kernel/cap_last_cap */
  35 static void test_last_cap_file(void) {
  36         _cleanup_free_ char *content = NULL;
  37         unsigned long val = 0;
  38         int r;
  39
  40         r = read_one_line_file("/proc/sys/kernel/cap_last_cap", &content);
  41         if (r == -ENOENT || ERRNO_IS_PRIVILEGE(r)) /* kernel pre 3.2 or no access */
  42                 return;
  43         assert_se(r >= 0);
  44
  45         r = safe_atolu(content, &val);
  46         assert_se(r >= 0);
  47         assert_se(val != 0);
  48         assert_se(val == cap_last_cap());
  49 }
  50
  51 /* verify cap_last_cap() against syscall probing */
  52 static void test_last_cap_probe(void) {
  53         unsigned long p = (unsigned long)CAP_LAST_CAP;
  54
  55         if (prctl(PR_CAPBSET_READ, p) < 0) {
  56                 for (p--; p > 0; p --)
  57                         if (prctl(PR_CAPBSET_READ, p) >= 0)
  58                                 break;
  59         } else {
  60                 for (;; p++)
  61                         if (prctl(PR_CAPBSET_READ, p+1) < 0)
  62                                 break;
  63         }
  64
  65         assert_se(p != 0);
  66         assert_se(p == cap_last_cap());
  67 }
  68
  69 static void fork_test(void (*test_func)(void)) {
  70         pid_t pid = 0;
  71
  72         pid = fork();
  73         assert_se(pid >= 0);
  74         if (pid == 0) {
  75                 test_func();
  76                 exit(EXIT_SUCCESS);
  77         } else if (pid > 0) {
  78                 int status;
  79
  80                 assert_se(waitpid(pid, &status, 0) > 0);
  81                 assert_se(WIFEXITED(status) && WEXITSTATUS(status) == 0);
  82         }
  83 }
  84
  85 static void show_capabilities(void) {
  86         cap_t caps;
  87         char *text;
  88
  89         caps = cap_get_proc();
  90         assert_se(caps);
  91
  92         text = cap_to_text(caps, NULL);
  93         assert_se(text);
  94
  95         log_info("Capabilities:%s", text);
  96         cap_free(caps);
  97         cap_free(text);
  98 }
  99
 100 static int setup_tests(bool *run_ambient) {
 101         struct passwd *nobody;
 102         int r;
 103
 104         nobody = getpwnam(NOBODY_USER_NAME);
 105         if (!nobody)
 106                 return log_error_errno(SYNTHETIC_ERRNO(ENOENT), "Could not find nobody user: %m");
 107
 108         test_uid = nobody->pw_uid;
 109         test_gid = nobody->pw_gid;
 110
 111         *run_ambient = false;
 112
 113         r = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0);
 114
 115         /* There's support for PR_CAP_AMBIENT if the prctl() call
 116          * succeeded or error code was something else than EINVAL. The
 117          * EINVAL check should be good enough to rule out false
 118          * positives. */
 119
 120         if (r >= 0 || errno != EINVAL)
 121                 *run_ambient = true;
 122
 123         return 0;
 124 }
 125
 126 static void test_drop_privileges_keep_net_raw(void) {
 127         int sock;
 128
 129         sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
 130         assert_se(sock >= 0);
 131         safe_close(sock);
 132
 133         assert_se(drop_privileges(test_uid, test_gid, test_flags | (1ULL << CAP_NET_RAW)) >= 0);
 134         assert_se(getuid() == test_uid);
 135         assert_se(getgid() == test_gid);
 136         show_capabilities();
 137
 138         sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
 139         assert_se(sock >= 0);
 140         safe_close(sock);
 141 }
 142
 143 static void test_drop_privileges_dontkeep_net_raw(void) {
 144         int sock;
 145
 146         sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
 147         assert_se(sock >= 0);
 148         safe_close(sock);
 149
 150         assert_se(drop_privileges(test_uid, test_gid, test_flags) >= 0);
 151         assert_se(getuid() == test_uid);
 152         assert_se(getgid() == test_gid);
 153         show_capabilities();
 154
 155         sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
 156         assert_se(sock < 0);
 157 }
 158
 159 static void test_drop_privileges_fail(void) {
 160         assert_se(drop_privileges(test_uid, test_gid, test_flags) >= 0);
 161         assert_se(getuid() == test_uid);
 162         assert_se(getgid() == test_gid);
 163
 164         assert_se(drop_privileges(test_uid, test_gid, test_flags) < 0);
 165         assert_se(drop_privileges(0, 0, test_flags) < 0);
 166 }
 167
 168 static void test_drop_privileges(void) {
 169         fork_test(test_drop_privileges_keep_net_raw);
 170         fork_test(test_drop_privileges_dontkeep_net_raw);
 171         fork_test(test_drop_privileges_fail);
 172 }
 173
 174 static void test_have_effective_cap(void) {
 175         assert_se(have_effective_cap(CAP_KILL));
 176         assert_se(have_effective_cap(CAP_CHOWN));
 177
 178         assert_se(drop_privileges(test_uid, test_gid, test_flags | (1ULL << CAP_KILL)) >= 0);
 179         assert_se(getuid() == test_uid);
 180         assert_se(getgid() == test_gid);
 181
 182         assert_se(have_effective_cap(CAP_KILL));
 183         assert_se(!have_effective_cap(CAP_CHOWN));
 184 }
 185
 186 static void test_update_inherited_set(void) {
 187         cap_t caps;
 188         uint64_t set = 0;
 189         cap_flag_value_t fv;
 190
 191         caps = cap_get_proc();
 192         assert_se(caps);
 193
 194         set = (UINT64_C(1) << CAP_CHOWN);
 195
 196         assert_se(!capability_update_inherited_set(caps, set));
 197         assert_se(!cap_get_flag(caps, CAP_CHOWN, CAP_INHERITABLE, &fv));
 198         assert(fv == CAP_SET);
 199
 200         cap_free(caps);
 201 }
 202
 203 static void test_apply_ambient_caps(void) {
 204         cap_t caps;
 205         uint64_t set = 0;
 206         cap_flag_value_t fv;
 207
 208         assert_se(prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_CHOWN, 0, 0) == 0);
 209
 210         set = (UINT64_C(1) << CAP_CHOWN);
 211
 212         assert_se(!capability_ambient_set_apply(set, true));
 213
 214         caps = cap_get_proc();
 215         assert_se(caps);
 216         assert_se(!cap_get_flag(caps, CAP_CHOWN, CAP_INHERITABLE, &fv));
 217         assert_se(fv == CAP_SET);
 218         cap_free(caps);
 219
 220         assert_se(prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_CHOWN, 0, 0) == 1);
 221
 222         assert_se(!capability_ambient_set_apply(0, true));
 223         caps = cap_get_proc();
 224         assert_se(caps);
 225         assert_se(!cap_get_flag(caps, CAP_CHOWN, CAP_INHERITABLE, &fv));
 226         assert_se(fv == CAP_CLEAR);
 227         cap_free(caps);
 228
 229         assert_se(prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_CHOWN, 0, 0) == 0);
 230 }
 231
 232 static void test_ensure_cap_64bit(void) {
 233         _cleanup_free_ char *content = NULL;
 234         unsigned long p = 0;
 235         int r;
 236
 237         r = read_one_line_file("/proc/sys/kernel/cap_last_cap", &content);
 238         if (r == -ENOENT || ERRNO_IS_PRIVILEGE(r)) /* kernel pre 3.2 or no access */
 239                 return;
 240         assert_se(r >= 0);
 241
 242         assert_se(safe_atolu(content, &p) >= 0);
 243
 244         /* If caps don't fit into 64bit anymore, we have a problem, fail the test. */
 245         assert_se(p <= 63);
 246
 247         /* Also check for the header definition */
 248         assert_cc(CAP_LAST_CAP <= 63);
 249 }
 250
 251 int main(int argc, char *argv[]) {
 252         bool run_ambient;
 253
 254         test_setup_logging(LOG_INFO);
 255
 256         test_ensure_cap_64bit();
 257
 258         test_last_cap_file();
 259         test_last_cap_probe();
 260
 261         log_info("have ambient caps: %s", yes_no(ambient_capabilities_supported()));
 262
 263         if (getuid() != 0)
 264                 return log_tests_skipped("not running as root");
 265
 266         if (setup_tests(&run_ambient) < 0)
 267                 return log_tests_skipped("setup failed");
 268
 269         show_capabilities();
 270
 271         test_drop_privileges();
 272         test_update_inherited_set();
 273
 274         fork_test(test_have_effective_cap);
 275
 276         if (run_ambient)
 277                 fork_test(test_apply_ambient_caps);
 278
 279         return 0;
 280 }