basic/cap-list: parse/print numerical capabilities

We would refuse to print capabilities which were didn't have a name
for. The kernel adds new capabilities from time to time, most recently
cap_bpf. 'systmectl show -p CapabilityBoundingSet ...' would fail with
"Failed to parse bus message: Invalid argument" because
capability_set_to_string_alloc() would fail with -EINVAL. So let's
print such capabilities in hexadecimal:

CapabilityBoundingSet=cap_chown cap_dac_override cap_dac_read_search
  cap_fowner cap_fsetid cap_kill cap_setgid cap_setuid cap_setpcap
  cap_linux_immutable cap_net_bind_service cap_net_broadcast cap_net_admin
  cap_net_raw cap_ipc_lock cap_ipc_owner 0x10 0x11 0x12 0x13 0x14 0x15 0x16
  0x17 0x18 0x19 0x1a ...

For symmetry, also allow capabilities that we don't know to be specified.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1853736.

(cherry picked from commit 417770f)

src/basic/cap-list.c

@@ -9,6 +9,7 @@
 #include "extract-word.h"
 #include "macro.h"
 #include "parse-util.h"
+#include "stdio-util.h"
 #include "util.h"
 
 static const struct capability_name* lookup_capability(register const char *str, register GPERF_LEN_TYPE len);
@@ -36,7 +37,7 @@ int capability_from_name(const char *name) {
         /* Try to parse numeric capability */
         r = safe_atoi(name, &i);
         if (r >= 0) {
-                if (i >= 0 && (size_t) i < ELEMENTSOF(capability_names))
+                if (i >= 0 && i < 64)
                         return i;
                 else
                         return -EINVAL;
@@ -64,11 +65,14 @@ int capability_set_to_string_alloc(uint64_t set, char **s) {
         for (i = 0; i <= cap_last_cap(); i++)
                 if (set & (UINT64_C(1) << i)) {
                         const char *p;
+                        char buf[2 + 16 + 1];
                         size_t add;
 
                         p = capability_to_name(i);
-                        if (!p)
-                                return -EINVAL;
+                        if (!p) {
+                                xsprintf(buf, "0x%lx", i);
+                                p = buf;
+                        }
 
                         add = strlen(p);
 

src/test/test-cap-list.c

@@ -31,6 +31,8 @@ static void test_cap_list(void) {
         assert_se(capability_from_name("cAp_aUdIt_rEAd") == CAP_AUDIT_READ);
         assert_se(capability_from_name("0") == 0);
         assert_se(capability_from_name("15") == 15);
+        assert_se(capability_from_name("63") == 63);
+        assert_se(capability_from_name("64") == -EINVAL);
         assert_se(capability_from_name("-1") == -EINVAL);
 
         for (i = 0; i < capability_list_length(); i++) {
@@ -65,7 +67,7 @@ static void test_capability_set_one(uint64_t c, const char *t) {
 
         free(t1);
         assert_se(t1 = strjoin("'cap_chown cap_dac_override' \"cap_setgid cap_setuid\"", t,
-                               " hogehoge foobar 12345 3.14 -3 ", t));
+                               " hogehoge foobar 18446744073709551616 3.14 -3 ", t));
         assert_se(capability_set_from_string(t1, &c1) == 0);
         assert_se(c1 == c_masked);
 }