unsigned long cap_last_cap(void) {
static thread_local unsigned long saved;
static thread_local bool valid = false;
+ _cleanup_free_ char *content = NULL;
unsigned long p;
+ int r;
if (valid)
return saved;
+ /* available since linux-3.2 */
+ r = read_one_line_file("/proc/sys/kernel/cap_last_cap", &content);
+ if (r >= 0) {
+ r = safe_atolu(content, &p);
+ if (r >= 0) {
+ saved = p;
+ valid = true;
+ return p;
+ }
+ }
+
+ /* fall back to syscall-probing for pre linux-3.2 */
p = (unsigned long) CAP_LAST_CAP;
if (prctl(PR_CAPBSET_READ, p) < 0) {
}
int capability_bounding_set_drop(uint64_t drop, bool right_now) {
- unsigned long i;
- _cleanup_cap_free_ cap_t after_cap = NULL, temp_cap = NULL;
+ _cleanup_cap_free_ cap_t after_cap = NULL;
cap_flag_value_t fv;
+ unsigned long i;
int r;
/* If we are run as PID 1 we will lack CAP_SETPCAP by default
return -errno;
if (fv != CAP_SET) {
+ _cleanup_cap_free_ cap_t temp_cap = NULL;
static const cap_value_t v = CAP_SETPCAP;
temp_cap = cap_dup(after_cap);
}
int drop_privileges(uid_t uid, gid_t gid, uint64_t keep_capabilities) {
-
_cleanup_cap_free_ cap_t d = NULL;
- cap_value_t bits[sizeof(keep_capabilities)*8];
unsigned i, j = 0;
int r;
* binary has the capability configured in the file system,
* which we want to avoid. */
- if (setresgid(gid, gid, gid) < 0) {
- log_error("Failed change group ID: %m");
- return -errno;
- }
+ if (setresgid(gid, gid, gid) < 0)
+ return log_error_errno(errno, "Failed to change group ID: %m");
- if (setgroups(0, NULL) < 0) {
- log_error("Failed to drop auxiliary groups list: %m");
- return -errno;
- }
+ if (setgroups(0, NULL) < 0)
+ return log_error_errno(errno, "Failed to drop auxiliary groups list: %m");
- if (prctl(PR_SET_KEEPCAPS, 1) < 0) {
- log_error("Failed to enable keep capabilities flag: %m");
- return -errno;
- }
+ /* Ensure we keep the permitted caps across the setresuid() */
+ if (prctl(PR_SET_KEEPCAPS, 1) < 0)
+ return log_error_errno(errno, "Failed to enable keep capabilities flag: %m");
r = setresuid(uid, uid, uid);
- if (r < 0) {
- log_error("Failed change user ID: %m");
- return -errno;
- }
+ if (r < 0)
+ return log_error_errno(errno, "Failed to change user ID: %m");
- if (prctl(PR_SET_KEEPCAPS, 0) < 0) {
- log_error("Failed to disable keep capabilities flag: %m");
- return -errno;
- }
+ if (prctl(PR_SET_KEEPCAPS, 0) < 0)
+ return log_error_errno(errno, "Failed to disable keep capabilities flag: %m");
+ /* Drop all caps from the bounding set, except the ones we want */
r = capability_bounding_set_drop(~keep_capabilities, true);
- if (r < 0) {
- log_error("Failed to drop capabilities: %s", strerror(-r));
- return r;
- }
+ if (r < 0)
+ return log_error_errno(r, "Failed to drop capabilities: %m");
+ /* Now upgrade the permitted caps we still kept to effective caps */
d = cap_init();
if (!d)
return log_oom();
if (keep_capabilities) {
- for (i = 0; i < sizeof(keep_capabilities)*8; i++)
+ cap_value_t bits[u64log2(keep_capabilities) + 1];
+
+ for (i = 0; i < ELEMENTSOF(bits); i++)
if (keep_capabilities & (1ULL << i))
bits[j++] = i;
+ /* use enough bits */
+ assert(i == 64 || (keep_capabilities >> i) == 0);
+ /* don't use too many bits */
+ assert(keep_capabilities & (1ULL << (i - 1)));
+
if (cap_set_flag(d, CAP_EFFECTIVE, j, bits, CAP_SET) < 0 ||
cap_set_flag(d, CAP_PERMITTED, j, bits, CAP_SET) < 0) {
- log_error("Failed to enable capabilities bits: %m");
+ log_error_errno(errno, "Failed to enable capabilities bits: %m");
return -errno;
}
+
+ if (cap_set_proc(d) < 0)
+ return log_error_errno(errno, "Failed to increase capabilities: %m");
}
- if (cap_set_proc(d) < 0) {
- log_error("Failed to increase capabilities: %m");
+ return 0;
+}
+
+int drop_capability(cap_value_t cv) {
+ _cleanup_cap_free_ cap_t tmp_cap = NULL;
+
+ tmp_cap = cap_get_proc();
+ if (!tmp_cap)
+ return -errno;
+
+ if ((cap_set_flag(tmp_cap, CAP_INHERITABLE, 1, &cv, CAP_CLEAR) < 0) ||
+ (cap_set_flag(tmp_cap, CAP_PERMITTED, 1, &cv, CAP_CLEAR) < 0) ||
+ (cap_set_flag(tmp_cap, CAP_EFFECTIVE, 1, &cv, CAP_CLEAR) < 0))
+ return -errno;
+
+ if (cap_set_proc(tmp_cap) < 0)
return -errno;
- }
return 0;
}