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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <netinet/in.h>
#include <pwd.h>
#include <sys/capability.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
#include "alloc-util.h"
#include "capability-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "macro.h"
#include "parse-util.h"
#include "tests.h"
#include "util.h"
static uid_t test_uid = -1;
static gid_t test_gid = -1;
#if HAS_FEATURE_ADDRESS_SANITIZER
/* Keep CAP_SYS_PTRACE when running under Address Sanitizer */
static const uint64_t test_flags = UINT64_C(1) << CAP_SYS_PTRACE;
#else
/* We keep CAP_DAC_OVERRIDE to avoid errors with gcov when doing test coverage */
static const uint64_t test_flags = UINT64_C(1) << CAP_DAC_OVERRIDE;
#endif
/* verify cap_last_cap() against /proc/sys/kernel/cap_last_cap */
static void test_last_cap_file(void) {
_cleanup_free_ char *content = NULL;
unsigned long val = 0;
int r;
r = read_one_line_file("/proc/sys/kernel/cap_last_cap", &content);
assert_se(r >= 0);
r = safe_atolu(content, &val);
assert_se(r >= 0);
assert_se(val != 0);
assert_se(val == cap_last_cap());
}
/* verify cap_last_cap() against syscall probing */
static void test_last_cap_probe(void) {
unsigned long p = (unsigned long)CAP_LAST_CAP;
if (prctl(PR_CAPBSET_READ, p) < 0) {
for (p--; p > 0; p --)
if (prctl(PR_CAPBSET_READ, p) >= 0)
break;
} else {
for (;; p++)
if (prctl(PR_CAPBSET_READ, p+1) < 0)
break;
}
assert_se(p != 0);
assert_se(p == cap_last_cap());
}
static void fork_test(void (*test_func)(void)) {
pid_t pid = 0;
pid = fork();
assert_se(pid >= 0);
if (pid == 0) {
test_func();
exit(EXIT_SUCCESS);
} else if (pid > 0) {
int status;
assert_se(waitpid(pid, &status, 0) > 0);
assert_se(WIFEXITED(status) && WEXITSTATUS(status) == 0);
}
}
static void show_capabilities(void) {
cap_t caps;
char *text;
caps = cap_get_proc();
assert_se(caps);
text = cap_to_text(caps, NULL);
assert_se(text);
log_info("Capabilities:%s", text);
cap_free(caps);
cap_free(text);
}
static int setup_tests(bool *run_ambient) {
struct passwd *nobody;
int r;
nobody = getpwnam(NOBODY_USER_NAME);
if (!nobody)
return log_error_errno(errno, "Could not find nobody user: %m");
test_uid = nobody->pw_uid;
test_gid = nobody->pw_gid;
*run_ambient = false;
r = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0);
/* There's support for PR_CAP_AMBIENT if the prctl() call
* succeeded or error code was something else than EINVAL. The
* EINVAL check should be good enough to rule out false
* positives. */
if (r >= 0 || errno != EINVAL)
*run_ambient = true;
return 0;
}
static void test_drop_privileges_keep_net_raw(void) {
int sock;
sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
assert_se(sock >= 0);
safe_close(sock);
assert_se(drop_privileges(test_uid, test_gid, test_flags | (1ULL << CAP_NET_RAW)) >= 0);
assert_se(getuid() == test_uid);
assert_se(getgid() == test_gid);
show_capabilities();
sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
assert_se(sock >= 0);
safe_close(sock);
}
static void test_drop_privileges_dontkeep_net_raw(void) {
int sock;
sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
assert_se(sock >= 0);
safe_close(sock);
assert_se(drop_privileges(test_uid, test_gid, test_flags) >= 0);
assert_se(getuid() == test_uid);
assert_se(getgid() == test_gid);
show_capabilities();
sock = socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
assert_se(sock < 0);
}
static void test_drop_privileges_fail(void) {
assert_se(drop_privileges(test_uid, test_gid, test_flags) >= 0);
assert_se(getuid() == test_uid);
assert_se(getgid() == test_gid);
assert_se(drop_privileges(test_uid, test_gid, test_flags) < 0);
assert_se(drop_privileges(0, 0, test_flags) < 0);
}
static void test_drop_privileges(void) {
fork_test(test_drop_privileges_keep_net_raw);
fork_test(test_drop_privileges_dontkeep_net_raw);
fork_test(test_drop_privileges_fail);
}
static void test_have_effective_cap(void) {
assert_se(have_effective_cap(CAP_KILL));
assert_se(have_effective_cap(CAP_CHOWN));
assert_se(drop_privileges(test_uid, test_gid, test_flags | (1ULL << CAP_KILL)) >= 0);
assert_se(getuid() == test_uid);
assert_se(getgid() == test_gid);
assert_se(have_effective_cap(CAP_KILL));
assert_se(!have_effective_cap(CAP_CHOWN));
}
static void test_update_inherited_set(void) {
cap_t caps;
uint64_t set = 0;
cap_flag_value_t fv;
caps = cap_get_proc();
assert_se(caps);
set = (UINT64_C(1) << CAP_CHOWN);
assert_se(!capability_update_inherited_set(caps, set));
assert_se(!cap_get_flag(caps, CAP_CHOWN, CAP_INHERITABLE, &fv));
assert(fv == CAP_SET);
cap_free(caps);
}
static void test_set_ambient_caps(void) {
cap_t caps;
uint64_t set = 0;
cap_flag_value_t fv;
assert_se(prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_CHOWN, 0, 0) == 0);
set = (UINT64_C(1) << CAP_CHOWN);
assert_se(!capability_ambient_set_apply(set, true));
caps = cap_get_proc();
assert_se(!cap_get_flag(caps, CAP_CHOWN, CAP_INHERITABLE, &fv));
assert(fv == CAP_SET);
cap_free(caps);
assert_se(prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_CHOWN, 0, 0) == 1);
}
int main(int argc, char *argv[]) {
bool run_ambient;
test_setup_logging(LOG_INFO);
test_last_cap_file();
test_last_cap_probe();
log_info("have ambient caps: %s", yes_no(ambient_capabilities_supported()));
if (getuid() != 0)
return log_tests_skipped("not running as root");
if (setup_tests(&run_ambient) < 0)
return log_tests_skipped("setup failed");
show_capabilities();
test_drop_privileges();
test_update_inherited_set();
fork_test(test_have_effective_cap);
if (run_ambient)
fork_test(test_set_ambient_caps);
return 0;
}
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