#include <ctype.h>
#include <sys/capability.h>
#include <sys/prctl.h>
+#include "grp.h"
#include "macro.h"
-#include "capability.h"
#include "util.h"
#include "log.h"
#include "fileio.h"
+#include "capability.h"
int have_effective_cap(int value) {
- cap_t cap;
+ _cleanup_cap_free_ cap_t cap;
cap_flag_value_t fv;
- int r;
cap = cap_get_proc();
if (!cap)
return -errno;
if (cap_get_flag(cap, value, CAP_EFFECTIVE, &fv) < 0)
- r = -errno;
+ return -errno;
else
- r = fv == CAP_SET;
-
- cap_free(cap);
- return r;
+ return fv == CAP_SET;
}
unsigned long cap_last_cap(void) {
- static __thread unsigned long saved;
- static __thread bool valid = false;
+ 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;
- 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
if (!after_cap)
return -errno;
- if (cap_get_flag(after_cap, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0) {
- cap_free(after_cap);
+ if (cap_get_flag(after_cap, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0)
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);
r = -errno;
goto finish;
}
- v = i;
+ v = (cap_value_t) i;
/* Also drop it from the inheritable set, so
* that anything we exec() loses the
r = 0;
finish:
- if (temp_cap)
- cap_free(temp_cap);
-
- if (after_cap) {
- cap_set_proc(after_cap);
- cap_free(after_cap);
- }
+ if (cap_set_proc(after_cap) < 0)
+ return -errno;
return r;
}
return r;
}
+
+int drop_privileges(uid_t uid, gid_t gid, uint64_t keep_capabilities) {
+ _cleanup_cap_free_ cap_t d = NULL;
+ unsigned i, j = 0;
+ int r;
+
+ /* Unfortunately we cannot leave privilege dropping to PID 1
+ * here, since we want to run as user but want to keep some
+ * capabilities. Since file capabilities have been introduced
+ * this cannot be done across exec() anymore, unless our
+ * binary has the capability configured in the file system,
+ * which we want to avoid. */
+
+ if (setresgid(gid, gid, gid) < 0)
+ return log_error_errno(errno, "Failed to change group ID: %m");
+
+ if (setgroups(0, NULL) < 0)
+ return log_error_errno(errno, "Failed to drop auxiliary groups list: %m");
+
+ /* 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)
+ return log_error_errno(errno, "Failed to change user ID: %m");
+
+ 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)
+ 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) {
+ cap_value_t bits[log2u64(keep_capabilities)];
+
+ for (i = 0; i < ELEMENTSOF(bits); i++)
+ if (keep_capabilities & (1ULL << i))
+ bits[j++] = i;
+ assert((keep_capabilities & (~1ULL << i)) == 0);
+
+ 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_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");
+ }
+
+ 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;
+}
~ianmdlvl / elogind.git / blobdiff