selinux: split up mac_selinux_have() from mac_selinux_use()

Let's distuingish the cases where our code takes an active role in
selinux management, or just passively reports whatever selinux
properties are set.

mac_selinux_have() now checks whether selinux is around for the passive
stuff, and mac_selinux_use() for the active stuff. The latter checks the
former, plus also checks UID == 0, under the assumption that only when
we run priviliged selinux management really makes sense.

Fixes: #1941

9 files changed, 23 insertions, 12 deletions

diff --git a/src/basic/selinux-util.c b/src/basic/selinux-util.c
index e8ce5cfd96..7e4ae33efe 100644
--- a/src/basic/selinux-util.c
+++ b/src/basic/selinux-util.c
@@ -47,7 +47,7 @@ static struct selabel_handle *label_hnd = NULL;
 #define log_enforcing(...) log_full(security_getenforce() == 1 ? LOG_ERR : LOG_DEBUG, __VA_ARGS__)
 #endif
 
-bool mac_selinux_use(void) {
+bool mac_selinux_have(void) {
 #ifdef HAVE_SELINUX
         if (cached_use < 0)
                 cached_use = is_selinux_enabled() > 0;
@@ -58,6 +58,16 @@ bool mac_selinux_use(void) {
 #endif
 }
 
+bool mac_selinux_use(void) {
+        if (!mac_selinux_have())
+                return false;
+
+        /* Never try to configure SELinux features if we aren't
+         * root */
+
+        return getuid() == 0;
+}
+
 void mac_selinux_retest(void) {
 #ifdef HAVE_SELINUX
         cached_use = -1;
@@ -197,7 +207,7 @@ int mac_selinux_get_create_label_from_exe(const char *exe, char **label) {
         assert(exe);
         assert(label);
 
-        if (!mac_selinux_use())
+        if (!mac_selinux_have())
                 return -EOPNOTSUPP;
 
         r = getcon_raw(&mycon);
@@ -223,7 +233,7 @@ int mac_selinux_get_our_label(char **label) {
         assert(label);
 
 #ifdef HAVE_SELINUX
-        if (!mac_selinux_use())
+        if (!mac_selinux_have())
                 return -EOPNOTSUPP;
 
         r = getcon_raw(label);
@@ -247,7 +257,7 @@ int mac_selinux_get_child_mls_label(int socket_fd, const char *exe, const char *
         assert(exe);
         assert(label);
 
-        if (!mac_selinux_use())
+        if (!mac_selinux_have())
                 return -EOPNOTSUPP;
 
         r = getcon_raw(&mycon);
@@ -302,7 +312,7 @@ char* mac_selinux_free(char *label) {
         if (!label)
                 return NULL;
 
-        if (!mac_selinux_use())
+        if (!mac_selinux_have())
                 return NULL;
 
 
diff --git a/src/basic/selinux-util.h b/src/basic/selinux-util.h
index d19984c5fe..95a2fcdbca 100644
--- a/src/basic/selinux-util.h
+++ b/src/basic/selinux-util.h
@@ -27,6 +27,7 @@
 #include "macro.h"
 
 bool mac_selinux_use(void);
+bool mac_selinux_have(void);
 void mac_selinux_retest(void);
 
 int mac_selinux_init(const char *prefix);
diff --git a/src/journal/journald-native.c b/src/journal/journald-native.c
index 69a685c06f..371df5b37f 100644
--- a/src/journal/journald-native.c
+++ b/src/journal/journald-native.c
@@ -480,7 +480,7 @@ int server_open_native_socket(Server*s) {
                 return log_error_errno(errno, "SO_PASSCRED failed: %m");
 
 #ifdef HAVE_SELINUX
-        if (mac_selinux_use()) {
+        if (mac_selinux_have()) {
                 r = setsockopt(s->native_fd, SOL_SOCKET, SO_PASSSEC, &one, sizeof(one));
                 if (r < 0)
                         log_warning_errno(errno, "SO_PASSSEC failed: %m");
diff --git a/src/journal/journald-server.c b/src/journal/journald-server.c
index 7d11a568aa..eb17f413f2 100644
--- a/src/journal/journald-server.c
+++ b/src/journal/journald-server.c
@@ -707,7 +707,7 @@ static void dispatch_message_real(
                 }
 
 #ifdef HAVE_SELINUX
-                if (mac_selinux_use()) {
+                if (mac_selinux_have()) {
                         if (label) {
                                 x = alloca(strlen("_SELINUX_CONTEXT=") + label_len + 1);
 
diff --git a/src/journal/journald-stream.c b/src/journal/journald-stream.c
index 07a0f1bf41..131fcdac42 100644
--- a/src/journal/journald-stream.c
+++ b/src/journal/journald-stream.c
@@ -493,7 +493,7 @@ static int stdout_stream_install(Server *s, int fd, StdoutStream **ret) {
         if (r < 0)
                 return log_error_errno(r, "Failed to determine peer credentials: %m");
 
-        if (mac_selinux_use()) {
+        if (mac_selinux_have()) {
                 r = getpeersec(fd, &stream->label);
                 if (r < 0 && r != -EOPNOTSUPP)
                         (void) log_warning_errno(r, "Failed to determine peer security context: %m");
diff --git a/src/journal/journald-syslog.c b/src/journal/journald-syslog.c
index f3ac1a7ae0..cfc50d889b 100644
--- a/src/journal/journald-syslog.c
+++ b/src/journal/journald-syslog.c
@@ -415,7 +415,7 @@ int server_open_syslog_socket(Server *s) {
                 return log_error_errno(errno, "SO_PASSCRED failed: %m");
 
 #ifdef HAVE_SELINUX
-        if (mac_selinux_use()) {
+        if (mac_selinux_have()) {
                 r = setsockopt(s->syslog_fd, SOL_SOCKET, SO_PASSSEC, &one, sizeof(one));
                 if (r < 0)
                         log_warning_errno(errno, "SO_PASSSEC failed: %m");
diff --git a/src/libsystemd/sd-bus/bus-socket.c b/src/libsystemd/sd-bus/bus-socket.c
index 25873dea1e..1df571ac92 100644
--- a/src/libsystemd/sd-bus/bus-socket.c
+++ b/src/libsystemd/sd-bus/bus-socket.c
@@ -609,7 +609,7 @@ static void bus_get_peercred(sd_bus *b) {
         b->ucred_valid = getpeercred(b->input_fd, &b->ucred) >= 0;
 
         /* Get the SELinux context of the peer */
-        if (mac_selinux_use()) {
+        if (mac_selinux_have()) {
                 r = getpeersec(b->input_fd, &b->label);
                 if (r < 0 && r != -EOPNOTSUPP)
                         log_debug_errno(r, "Failed to determine peer security context: %m");
diff --git a/src/shared/condition.c b/src/shared/condition.c
index a69719116c..14d18429b6 100644
--- a/src/shared/condition.c
+++ b/src/shared/condition.c
@@ -231,7 +231,7 @@ static int condition_test_security(Condition *c) {
         assert(c->type == CONDITION_SECURITY);
 
         if (streq(c->parameter, "selinux"))
-                return mac_selinux_use();
+                return mac_selinux_have();
         if (streq(c->parameter, "smack"))
                 return mac_smack_use();
         if (streq(c->parameter, "apparmor"))
diff --git a/src/test/test-condition.c b/src/test/test-condition.c
index f224c6cdd8..8903d10db7 100644
--- a/src/test/test-condition.c
+++ b/src/test/test-condition.c
@@ -203,7 +203,7 @@ static void test_condition_test_security(void) {
         condition_free(condition);
 
         condition = condition_new(CONDITION_SECURITY, "selinux", false, true);
-        assert_se(condition_test(condition) != mac_selinux_use());
+        assert_se(condition_test(condition) != mac_selinux_have());
         condition_free(condition);
 
         condition = condition_new(CONDITION_SECURITY, "ima", false, false);