Extract looping over /proc/cmdline into a shared function

[elogind.git] / src / shared / capability.c

diff --git a/src/shared/capability.c b/src/shared/capability.c
index b2cd9ed75e8ab0d6efe9ebc1d8c7f522ae85a640..f8ee1c6838b63d00d1ad259c95b16dbd79e6e084 100644 (file)
--- a/src/shared/capability.c
+++ b/src/shared/capability.c
@@ -34,27 +34,25 @@
 #include "capability.h"
 #include "util.h"
 #include "log.h"
+#include "fileio.h"
 
 int have_effective_cap(int value) {
-        cap_t cap;
+        _cleanup_cap_free_ cap_t cap;
         cap_flag_value_t fv;
-        int r;
 
-        if (!(cap = cap_get_proc()))
+        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;
         unsigned long p;
 
         if (valid)
@@ -84,3 +82,132 @@ unsigned long cap_last_cap(void) {
 
         return p;
 }
+
+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;
+        cap_flag_value_t fv;
+        int r;
+
+        /* If we are run as PID 1 we will lack CAP_SETPCAP by default
+         * in the effective set (yes, the kernel drops that when
+         * executing init!), so get it back temporarily so that we can
+         * call PR_CAPBSET_DROP. */
+
+        after_cap = cap_get_proc();
+        if (!after_cap)
+                return -errno;
+
+        if (cap_get_flag(after_cap, CAP_SETPCAP, CAP_EFFECTIVE, &fv) < 0)
+                return -errno;
+
+        if (fv != CAP_SET) {
+                static const cap_value_t v = CAP_SETPCAP;
+
+                temp_cap = cap_dup(after_cap);
+                if (!temp_cap) {
+                        r = -errno;
+                        goto finish;
+                }
+
+                if (cap_set_flag(temp_cap, CAP_EFFECTIVE, 1, &v, CAP_SET) < 0) {
+                        r = -errno;
+                        goto finish;
+                }
+
+                if (cap_set_proc(temp_cap) < 0) {
+                        r = -errno;
+                        goto finish;
+                }
+        }
+
+        for (i = 0; i <= cap_last_cap(); i++) {
+
+                if (drop & ((uint64_t) 1ULL << (uint64_t) i)) {
+                        cap_value_t v;
+
+                        /* Drop it from the bounding set */
+                        if (prctl(PR_CAPBSET_DROP, i) < 0) {
+                                r = -errno;
+                                goto finish;
+                        }
+                        v = (cap_value_t) i;
+
+                        /* Also drop it from the inheritable set, so
+                         * that anything we exec() loses the
+                         * capability for good. */
+                        if (cap_set_flag(after_cap, CAP_INHERITABLE, 1, &v, CAP_CLEAR) < 0) {
+                                r = -errno;
+                                goto finish;
+                        }
+
+                        /* If we shall apply this right now drop it
+                         * also from our own capability sets. */
+                        if (right_now) {
+                                if (cap_set_flag(after_cap, CAP_PERMITTED, 1, &v, CAP_CLEAR) < 0 ||
+                                    cap_set_flag(after_cap, CAP_EFFECTIVE, 1, &v, CAP_CLEAR) < 0) {
+                                        r = -errno;
+                                        goto finish;
+                                }
+                        }
+                }
+        }
+
+        r = 0;
+
+finish:
+        cap_set_proc(after_cap);
+
+        return r;
+}
+
+static int drop_from_file(const char *fn, uint64_t drop) {
+        int r, k;
+        uint32_t hi, lo;
+        uint64_t current, after;
+        char *p;
+
+        r = read_one_line_file(fn, &p);
+        if (r < 0)
+                return r;
+
+        assert_cc(sizeof(hi) == sizeof(unsigned));
+        assert_cc(sizeof(lo) == sizeof(unsigned));
+
+        k = sscanf(p, "%u %u", &lo, &hi);
+        free(p);
+
+        if (k != 2)
+                return -EIO;
+
+        current = (uint64_t) lo | ((uint64_t) hi << 32ULL);
+        after = current & ~drop;
+
+        if (current == after)
+                return 0;
+
+        lo = (unsigned) (after & 0xFFFFFFFFULL);
+        hi = (unsigned) ((after >> 32ULL) & 0xFFFFFFFFULL);
+
+        if (asprintf(&p, "%u %u", lo, hi) < 0)
+                return -ENOMEM;
+
+        r = write_string_file(fn, p);
+        free(p);
+
+        return r;
+}
+
+int capability_bounding_set_drop_usermode(uint64_t drop) {
+        int r;
+
+        r = drop_from_file("/proc/sys/kernel/usermodehelper/inheritable", drop);
+        if (r < 0)
+                return r;
+
+        r = drop_from_file("/proc/sys/kernel/usermodehelper/bset", drop);
+        if (r < 0)
+                return r;
+
+        return r;
+}