From 98bb285648a68c89820fe7415737ee97da74ec69 Mon Sep 17 00:00:00 2001

From: Michal Sekletar <msekleta@redhat.com>

Date: Thu, 24 Jul 2014 10:40:28 +0200

Subject: [PATCH] socket: introduce SELinuxContextFromNet option

This makes possible to spawn service instances triggered by socket with

MLS/MCS SELinux labels which are created based on information provided by

connected peer.

Implementation of label_get_child_mls_label derived from xinetd.

Reviewed-by: Paul Moore <pmoore@redhat.com>

Resolves: #1113790

---

 man/systemd.socket.xml                |  26 ++++++++

 src/core/execute.c                    |  30 +++++++--

 src/core/execute.h                    |   1 +

 src/core/load-fragment-gperf.gperf.m4 |   1 +

 src/core/mount.c                      |   1 +

 src/core/service.c                    |   4 +-

 src/core/service.h                    |   3 +-

 src/core/socket.c                     |  16 +++--

 src/core/socket.h                     |   2 +

 src/core/swap.c                       |   1 +

 src/shared/label.c                    | 113 ++++++++++++++++++++++++++++++++++

 src/shared/label.h                    |   2 +

 12 files changed, 189 insertions(+), 11 deletions(-)

diff --git a/man/systemd.socket.xml b/man/systemd.socket.xml

index d146b3b..75ba15f 100644

--- a/man/systemd.socket.xml

+++ b/man/systemd.socket.xml

@@ -585,6 +585,32 @@

                         </varlistentry>

                         <varlistentry>

+                          <term><varname>SELinuxContextFromNet=</varname></term>

+                                 <listitem><para>Takes a boolean

+                                 argument. When true systemd will attempt

+                                 to figure out the SELinux label used

+                                 for the instantiated service from the

+                                 information handed by the peer over the

+                                 network. Note that only the security

+                                 level is used from the information

+                                 provided by the peer. Other parts of

+                                 the resulting SELinux context originate

+                                 from either the target binary that is

+                                 effectively triggered by socket unit

+                                 are taken from the value of the

+                                 <varname>SELinuxContext=</varname>

+                                 option.This configuration option only

+                                 affects sockets with

+                                 <varname>Accept=</varname> mode set to

+                                 <literal>true</literal>. Also note that

+                                 this option is useful only when

+                                 MLS/MCS SELinux policy is

+                                 deployed. Defaults to

+                                 <literal>false</literal>.

+                                 </para></listitem>

+                        </varlistentry>

+

+                        <varlistentry>

                                 <term><varname>PipeSize=</varname></term>

                                 <listitem><para>Takes an integer

                                 value. Controls the pipe buffer size

diff --git a/src/core/execute.c b/src/core/execute.c

index a20301d..0894156 100644

--- a/src/core/execute.c

+++ b/src/core/execute.c

@@ -73,6 +73,7 @@

 #include "unit.h"

 #include "async.h"

 #include "selinux-util.h"

+#include "label.h"

 #define IDLE_TIMEOUT_USEC (5*USEC_PER_SEC)

 #define IDLE_TIMEOUT2_USEC (1*USEC_PER_SEC)

@@ -1038,6 +1039,7 @@ int exec_spawn(ExecCommand *command,

                bool apply_chroot,

                bool apply_tty_stdin,

                bool confirm_spawn,

+               bool selinux_context_net,

                CGroupControllerMask cgroup_supported,

                const char *cgroup_path,

                const char *unit_id,

@@ -1473,11 +1475,29 @@ int exec_spawn(ExecCommand *command,

                                 }

                         }

 #ifdef HAVE_SELINUX

-                        if (context->selinux_context && use_selinux()) {

-                                err = setexeccon(context->selinux_context);

-                                if (err < 0 && !context->selinux_context_ignore) {

-                                        r = EXIT_SELINUX_CONTEXT;

-                                        goto fail_child;

+                        if (use_selinux()) {

+                                if (context->selinux_context) {

+                                        err = setexeccon(context->selinux_context);

+                                        if (err < 0 && !context->selinux_context_ignore) {

+                                                r = EXIT_SELINUX_CONTEXT;

+                                                goto fail_child;

+                                        }

+                                }

+

+                                if (selinux_context_net && socket_fd >= 0) {

+                                        _cleanup_free_ char *label = NULL;

+

+                                        err = label_get_child_mls_label(socket_fd, command->path, &label);

+                                        if (err < 0) {

+                                                r = EXIT_SELINUX_CONTEXT;

+                                                goto fail_child;

+                                        }

+

+                                        err = setexeccon(label);

+                                        if (err < 0) {

+                                                r = EXIT_SELINUX_CONTEXT;

+                                                goto fail_child;

+                                        }

                                 }

                         }

 #endif

diff --git a/src/core/execute.h b/src/core/execute.h

index 2452126..5055890 100644

--- a/src/core/execute.h

+++ b/src/core/execute.h

@@ -174,6 +174,7 @@ int exec_spawn(ExecCommand *command,

                bool apply_chroot,

                bool apply_tty_stdin,

                bool confirm_spawn,

+               bool selinux_context_net,

                CGroupControllerMask cgroup_mask,

                const char *cgroup_path,

                const char *unit_id,

diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4

index 759fbd8..ee7cd5d 100644

--- a/src/core/load-fragment-gperf.gperf.m4

+++ b/src/core/load-fragment-gperf.gperf.m4

@@ -221,6 +221,7 @@ Socket.Service,                  config_parse_socket_service,        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)

+Socket.SELinuxContextFromNet,    config_parse_bool,                  0,                             offsetof(Socket, selinux_context_from_net),

 EXEC_CONTEXT_CONFIG_ITEMS(Socket)m4_dnl

 CGROUP_CONTEXT_CONFIG_ITEMS(Socket)m4_dnl

 KILL_CONTEXT_CONFIG_ITEMS(Socket)m4_dnl

diff --git a/src/core/mount.c b/src/core/mount.c

index 3672338..bbceb92 100644

--- a/src/core/mount.c

+++ b/src/core/mount.c

@@ -791,6 +791,7 @@ static int mount_spawn(Mount *m, ExecCommand *c, pid_t *_pid) {

                        true,

                        true,

                        UNIT(m)->manager->confirm_spawn,

+                       false,

                        UNIT(m)->manager->cgroup_supported,

                        UNIT(m)->cgroup_path,

                        UNIT(m)->id,

diff --git a/src/core/service.c b/src/core/service.c

index 4366e1b..7ef2b3a 100644

--- a/src/core/service.c

+++ b/src/core/service.c

@@ -1867,6 +1867,7 @@ static int service_spawn(

                        apply_chroot,

                        apply_tty_stdin,

                        UNIT(s)->manager->confirm_spawn,

+                       false,

                        UNIT(s)->manager->cgroup_supported,

                        path,

                        UNIT(s)->id,

@@ -3806,7 +3807,7 @@ static void service_bus_query_pid_done(

         }

 }

-int service_set_socket_fd(Service *s, int fd, Socket *sock) {

+int service_set_socket_fd(Service *s, int fd, Socket *sock, bool selinux_context_net) {

         assert(s);

         assert(fd >= 0);

@@ -3825,6 +3826,7 @@ int service_set_socket_fd(Service *s, int fd, Socket *sock) {

                 return -EAGAIN;

         s->socket_fd = fd;

+        s->socket_fd_selinux_context_net = selinux_context_net;

         s->got_socket_fd = true;

         unit_ref_set(&s->accept_socket, UNIT(sock));

diff --git a/src/core/service.h b/src/core/service.h

index fa4ef2b..24e6b4e 100644

--- a/src/core/service.h

+++ b/src/core/service.h

@@ -156,6 +156,7 @@ struct Service {

         pid_t main_pid, control_pid;

         int socket_fd;

+        bool socket_fd_selinux_context_net;

         int fsck_passno;

@@ -204,7 +205,7 @@ extern const UnitVTable service_vtable;

 struct Socket;

-int service_set_socket_fd(Service *s, int fd, struct Socket *socket);

+int service_set_socket_fd(Service *s, int fd, struct Socket *socket, bool selinux_context_net);

 const char* service_state_to_string(ServiceState i) _const_;

 ServiceState service_state_from_string(const char *s) _pure_;

diff --git a/src/core/socket.c b/src/core/socket.c

index 32e0d35..35fc204 100644

--- a/src/core/socket.c

+++ b/src/core/socket.c

@@ -431,7 +431,8 @@ static void socket_dump(Unit *u, FILE *f, const char *prefix) {

                 "%sBroadcast: %s\n"

                 "%sPassCredentials: %s\n"

                 "%sPassSecurity: %s\n"

-                "%sTCPCongestion: %s\n",

+                "%sTCPCongestion: %s\n"

+                "%sSELinuxContextFromNet: %s\n",

                 prefix, socket_state_to_string(s->state),

                 prefix, socket_result_to_string(s->result),

                 prefix, socket_address_bind_ipv6_only_to_string(s->bind_ipv6_only),

@@ -444,7 +445,8 @@ static void socket_dump(Unit *u, FILE *f, const char *prefix) {

                 prefix, yes_no(s->broadcast),

                 prefix, yes_no(s->pass_cred),

                 prefix, yes_no(s->pass_sec),

-                prefix, strna(s->tcp_congestion));

+                prefix, strna(s->tcp_congestion),

+                prefix, yes_no(s->selinux_context_from_net));

         if (s->control_pid > 0)

                 fprintf(f,

@@ -994,7 +996,12 @@ static int socket_open_fds(Socket *s) {

                 if (p->type == SOCKET_SOCKET) {

-                        if (!know_label) {

+                        if (!know_label && s->selinux_context_from_net) {

+                                r = label_get_our_label(&label);

+                                if (r < 0)

+                                        return r;

+                                know_label = true;

+                        } else if (!know_label) {

                                 if ((r = socket_instantiate_service(s)) < 0)

                                         return r;

@@ -1227,6 +1234,7 @@ static int socket_spawn(Socket *s, ExecCommand *c, pid_t *_pid) {

                        true,

                        true,

                        UNIT(s)->manager->confirm_spawn,

+                       s->selinux_context_from_net,

                        UNIT(s)->manager->cgroup_supported,

                        UNIT(s)->cgroup_path,

                        UNIT(s)->id,

@@ -1666,7 +1674,7 @@ static void socket_enter_running(Socket *s, int cfd) {

                 unit_choose_id(UNIT(service), name);

                 free(name);

-                r = service_set_socket_fd(service, cfd, s);

+                r = service_set_socket_fd(service, cfd, s, s->selinux_context_from_net);

                 if (r < 0)

                         goto fail;

diff --git a/src/core/socket.h b/src/core/socket.h

index 6a24883..ddddf4c 100644

--- a/src/core/socket.h

+++ b/src/core/socket.h

@@ -154,6 +154,8 @@ struct Socket {

         char *smack_ip_in;

         char *smack_ip_out;

+        bool selinux_context_from_net;

+

         char *user;

         char *group;

 };

diff --git a/src/core/swap.c b/src/core/swap.c

index 727bb95..b72034f 100644

--- a/src/core/swap.c

+++ b/src/core/swap.c

@@ -589,6 +589,7 @@ static int swap_spawn(Swap *s, ExecCommand *c, pid_t *_pid) {

                        true,

                        true,

                        UNIT(s)->manager->confirm_spawn,

+                       false,

                        UNIT(s)->manager->cgroup_supported,

                        UNIT(s)->cgroup_path,

                        UNIT(s)->id,

diff --git a/src/shared/label.c b/src/shared/label.c

index fde39f2..4dab93e 100644

--- a/src/shared/label.c

+++ b/src/shared/label.c

@@ -38,6 +38,13 @@

 #include "selinux-util.h"

 #include <selinux/selinux.h>

 #include <selinux/label.h>

+#include <selinux/context.h>

+

+define_trivial_cleanup_func(security_context_t, freecon);

+define_trivial_cleanup_func(context_t, context_free);

+

+#define _cleanup_security_context_free_ _cleanup_(freeconp)

+#define _cleanup_context_free_ _cleanup_(context_freep)

 static struct selabel_handle *label_hnd = NULL;

@@ -180,6 +187,112 @@ fail:

         return r;

 }

+int label_get_our_label(char **label) {

+        int r = -EOPNOTSUPP;

+        char *l = NULL;

+

+#ifdef HAVE_SELINUX

+        r = getcon(&l);

+        if (r < 0)

+                return r;

+

+        *label = l;

+#endif

+

+        return r;

+}

+

+int label_get_child_mls_label(int socket_fd, const char *exe, char **label) {

+        int r = -EOPNOTSUPP;

+

+#ifdef HAVE_SELINUX

+

+        _cleanup_security_context_free_ security_context_t mycon = NULL, peercon = NULL, fcon = NULL, ret = NULL;

+        _cleanup_context_free_ context_t pcon = NULL, bcon = NULL;

+        security_class_t sclass;

+

+        const char *range = NULL;

+

+        assert(socket_fd >= 0);

+        assert(exe);

+        assert(label);

+

+        r = getcon(&mycon);

+        if (r < 0) {

+                r = -EINVAL;

+                goto out;

+        }

+

+        r = getpeercon(socket_fd, &peercon);

+        if (r < 0) {

+                r = -EINVAL;

+                goto out;

+        }

+

+        r = getexeccon(&fcon);

+        if (r < 0) {

+                r = -EINVAL;

+                goto out;

+        }

+

+        if (!fcon) {

+                /* If there is no context set for next exec let's use context

+                   of target executable */

+                r = getfilecon(exe, &fcon);

+                if (r < 0) {

+                        r = -errno;

+                        goto out;

+                }

+        }

+

+        bcon = context_new(mycon);

+        if (!bcon) {

+                r = -ENOMEM;

+                goto out;

+        }

+

+        pcon = context_new(peercon);

+        if (!pcon) {

+                r = -ENOMEM;

+                goto out;

+        }

+

+        range = context_range_get(pcon);

+        if (!range) {

+                r = -errno;

+                goto out;

+        }

+

+        r = context_range_set(bcon, range);

+        if (r) {

+                r = -errno;

+                goto out;

+        }

+

+        freecon(mycon);

+        mycon = context_str(bcon);

+        if (!mycon) {

+                r = -errno;

+                goto out;

+        }

+

+        sclass = string_to_security_class("process");

+        r = security_compute_create(mycon, fcon, sclass, &ret;;

+        if (r < 0) {

+                r = -EINVAL;

+                goto out;

+        }

+

+        *label = ret;

+        r = 0;

+

+out:

+        if (r < 0 && security_getenforce() == 1)

+                return r;

+#endif

+        return r;

+}

+

 int label_context_set(const char *path, mode_t mode) {

         int r = 0;

diff --git a/src/shared/label.h b/src/shared/label.h

index 09e15e3..d8a281c 100644

--- a/src/shared/label.h

+++ b/src/shared/label.h

@@ -39,6 +39,8 @@ void label_context_clear(void);

 void label_free(const char *label);

 int label_get_create_label_from_exe(const char *exe, char **label);

+int label_get_our_label(char **label);

+int label_get_child_mls_label(int socket_fd, const char *exec, char **label);

 int label_mkdir(const char *path, mode_t mode);