SMACK: Add configuration options. (v3)

This adds SMACK label configuration options to socket units.

SMACK labels should be applied to most objects on disk well before
execution time, but two items remain that are generated dynamically
at run time that require SMACK labels to be set in order to enforce
MAC on all objects.

Files on disk can be labelled using package management.

For device nodes, simple udev rules are sufficient to add SMACK labels
at boot/insertion time.

Sockets can be created at run time and systemd does just that for
several services. In order to protect FIFO's and UNIX domain sockets,
we must instruct systemd to apply SMACK labels at runtime.

This patch adds the following options:

Smack - applicable to FIFO's.
SmackIpIn/SmackIpOut - applicable to sockets.

No external dependencies are required to support SMACK, as setting
the labels is done using fsetxattr(). The labels can be set on a
kernel that does not have SMACK enabled either, so there is no need
to #ifdef any of this code out.

For more information about SMACK, please see Documentation/Smack.txt
in the kernel source code.

v3 of this patch changes the config options to be CamelCased.

4 files changed, 45 insertions, 0 deletions

diff --git a/src/core/dbus-socket.c b/src/core/dbus-socket.c
index c57cce19fb..095a031612 100644
--- a/src/core/dbus-socket.c
+++ b/src/core/dbus-socket.c
@@ -63,6 +63,9 @@
         "  <property name=\"MessageQueueMaxMessages\" type=\"x\" access=\"read\"/>\n" \
         "  <property name=\"MessageQueueMessageSize\" type=\"x\" access=\"read\"/>\n" \
         "  <property name=\"Result\" type=\"s\" access=\"read\"/>\n"    \
+        "  <property name=\"SmackLabel\" type=\"s\" access=\"read\"/>\n" \
+        "  <property name=\"SmackLabelIPIn\" type=\"s\" access=\"read\"/>\n" \
+        "  <property name=\"SmackLabelIPOut\" type=\"s\" access=\"read\"/>\n" \
         " </interface>\n"                                               \
 
 #define INTROSPECTION                                                   \
@@ -126,6 +129,9 @@ static const BusProperty bus_socket_properties[] = {
         { "MessageQueueMaxMessages", bus_property_append_long, "x", offsetof(Socket, mq_maxmsg)       },
         { "MessageQueueMessageSize", bus_property_append_long, "x", offsetof(Socket, mq_msgsize)      },
         { "Result",         bus_socket_append_socket_result,   "s", offsetof(Socket, result)          },
+        { "SmackLabel",     bus_property_append_string,        "s", offsetof(Socket, smack),          true },
+        { "SmackLabelIPIn", bus_property_append_string,        "s", offsetof(Socket, smack_ip_in),    true },
+        { "SmackLabelIPOut",bus_property_append_string,        "s", offsetof(Socket, smack_ip_out),   true },
         { NULL, }
 };
 
diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4
index 8187cd48c6..0c5ccebd73 100644
--- a/src/core/load-fragment-gperf.gperf.m4
+++ b/src/core/load-fragment-gperf.gperf.m4
@@ -208,6 +208,9 @@ Socket.TCPCongestion,            config_parse_string,                0,
 Socket.MessageQueueMaxMessages,  config_parse_long,                  0,                             offsetof(Socket, mq_maxmsg)
 Socket.MessageQueueMessageSize,  config_parse_long,                  0,                             offsetof(Socket, mq_msgsize)
 Socket.Service,                  config_parse_socket_service,        0,                             0
+Socket.SmackLabel,               config_parse_string,                0,                             offsetof(Socket, smack)
+Socket.SmackLabelIPIn,           config_parse_string,                0,                             offsetof(Socket, smack_ip_in)
+Socket.SmackLabelIPOut,          config_parse_string,                0,                             offsetof(Socket, smack_ip_out)
 EXEC_CONTEXT_CONFIG_ITEMS(Socket)m4_dnl
 KILL_CONTEXT_CONFIG_ITEMS(Socket)m4_dnl
 m4_dnl
diff --git a/src/core/socket.c b/src/core/socket.c
index 71cdf2dfc8..c0959815c1 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -28,6 +28,7 @@
 #include <signal.h>
 #include <arpa/inet.h>
 #include <mqueue.h>
+#include <attr/xattr.h>
 
 #include "unit.h"
 #include "socket.h"
@@ -131,6 +132,10 @@ static void socket_done(Unit *u) {
         free(s->bind_to_device);
         s->bind_to_device = NULL;
 
+        free(s->smack);
+        free(s->smack_ip_in);
+        free(s->smack_ip_out);
+
         unit_unwatch_timer(u, &s->timer_watch);
 }
 
@@ -508,6 +513,21 @@ static void socket_dump(Unit *u, FILE *f, const char *prefix) {
                         "%sMessageQueueMessageSize: %li\n",
                         prefix, s->mq_msgsize);
 
+        if (s->smack)
+                fprintf(f,
+                        "%sSmackLabel: %s\n",
+                        prefix, s->smack);
+
+        if (s->smack_ip_in)
+                fprintf(f,
+                        "%sSmackLabelIPIn: %s\n",
+                        prefix, s->smack_ip_in);
+
+        if (s->smack_ip_out)
+                fprintf(f,
+                        "%sSmackLabelIPOut: %s\n",
+                        prefix, s->smack_ip_out);
+
         LIST_FOREACH(port, p, s->ports) {
 
                 if (p->type == SOCKET_SOCKET) {
@@ -747,6 +767,14 @@ static void socket_apply_socket_options(Socket *s, int fd) {
         if (s->tcp_congestion)
                 if (setsockopt(fd, SOL_TCP, TCP_CONGESTION, s->tcp_congestion, strlen(s->tcp_congestion)+1) < 0)
                         log_warning("TCP_CONGESTION failed: %m");
+
+        if (s->smack_ip_in)
+                if (fsetxattr(fd, "security.SMACK64IPIN", s->smack_ip_in, strlen(s->smack_ip_in), 0) < 0)
+                        log_error("fsetxattr(\"security.SMACK64IPIN\"): %m");
+
+        if (s->smack_ip_out)
+                if (fsetxattr(fd, "security.SMACK64IPOUT", s->smack_ip_out, strlen(s->smack_ip_out), 0) < 0)
+                        log_error("fsetxattr(\"security.SMACK64IPOUT\"): %m");
 }
 
 static void socket_apply_fifo_options(Socket *s, int fd) {
@@ -756,6 +784,10 @@ static void socket_apply_fifo_options(Socket *s, int fd) {
         if (s->pipe_size > 0)
                 if (fcntl(fd, F_SETPIPE_SZ, s->pipe_size) < 0)
                         log_warning("F_SETPIPE_SZ: %m");
+
+        if (s->smack)
+                if (fsetxattr(fd, "security.SMACK64", s->smack, strlen(s->smack), 0) < 0)
+                        log_error("fsetxattr(\"security.SMACK64\"): %m");
 }
 
 static int fifo_address_create(
diff --git a/src/core/socket.h b/src/core/socket.h
index a06b3eae94..f099520dce 100644
--- a/src/core/socket.h
+++ b/src/core/socket.h
@@ -144,6 +144,10 @@ struct Socket {
 
         /* Only for INET6 sockets: issue IPV6_V6ONLY sockopt */
         SocketAddressBindIPv6Only bind_ipv6_only;
+
+        char *smack;
+        char *smack_ip_in;
+        char *smack_ip_out;
 };
 
 /* Called from the service code when collecting fds */