From 16115b0a7b7cdf08fb38084d857d572d8a9088dc 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>

---

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

 src/core/execute.c                    |  29 +++++++--

 src/core/execute.h                    |   1 +

 src/core/load-fragment-gperf.gperf.m4 |   3 +

 src/core/service.c                    |   4 +-

 src/core/service.h                    |   3 +-

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

 src/core/socket.h                     |   2 +

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

 src/shared/label.h                    |   2 +

 10 files changed, 187 insertions(+), 12 deletions(-)

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

index 7a63348caf..dad0267467 100644

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

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

@@ -676,6 +676,32 @@

                         </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 a size in

                                 bytes. Controls the pipe buffer size

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

index db755777c1..8c9dfde00a 100644

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

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

@@ -84,6 +84,7 @@

 #include "mkdir.h"

 #include "apparmor-util.h"

 #include "bus-kernel.h"

+#include "label.h"

 #ifdef HAVE_SECCOMP

 #include "seccomp-util.h"

@@ -1665,11 +1666,29 @@ static int exec_child(ExecCommand *command,

 #endif

 #ifdef HAVE_SELINUX

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

-                        err = setexeccon(context->selinux_context);

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

-                                *error = EXIT_SELINUX_CONTEXT;

-                                return err;

+                if (use_selinux()) {

+                        if (context->selinux_context) {

+                                err = setexeccon(context->selinux_context);

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

+                                        *error = EXIT_SELINUX_CONTEXT;

+                                        return err;

+                                }

+                        }

+

+                        if (params->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) {

+                                        *error = EXIT_SELINUX_CONTEXT;

+                                        return err;

+                                }

+

+                                err = setexeccon(label);

+                                if (err < 0) {

+                                        *error = EXIT_SELINUX_CONTEXT;

+                                        return err;

+                                }

                         }

                 }

 #endif

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

index 9c1f249cd4..6f35736eda 100644

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

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

@@ -204,6 +204,7 @@ struct ExecParameters {

         bool apply_chroot;

         bool apply_tty_stdin;

         bool confirm_spawn;

+        bool selinux_context_net;

         CGroupControllerMask cgroup_supported;

         const char *cgroup_path;

         const char *runtime_prefix;

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

index e764d68ce4..050c5d819f 100644

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

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

@@ -265,6 +265,9 @@ Socket.SmackLabelIPOut,          config_parse_string,                0,

 `Socket.SmackLabel,              config_parse_warn_compat,           0,                             0

 Socket.SmackLabelIPIn,           config_parse_warn_compat,           0,                             0

 Socket.SmackLabelIPOut,          config_parse_warn_compat,           0,                             0')

+m4_ifdef(`HAVE_SELINUX',

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

+`Socket.SELinuxContextFromNet,   config_parse_warn_compat,           0,                             0')

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

index 3f6595c5c8..395e0ca8c6 100644

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

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

@@ -901,6 +901,7 @@ static int service_spawn(

                 .apply_chroot      = apply_chroot,

                 .apply_tty_stdin   = apply_tty_stdin,

                 .bus_endpoint_fd   = -1,

+                .selinux_context_net = s->socket_fd_selinux_context_net

         };

         assert(s);

@@ -2748,7 +2749,7 @@ static void service_bus_name_owner_change(

         }

 }

-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) {

         _cleanup_free_ char *peer = NULL;

         int r;

@@ -2786,6 +2787,7 @@ int service_set_socket_fd(Service *s, int fd, Socket *sock) {

         }

         s->socket_fd = fd;

+        s->socket_fd_selinux_context_net = selinux_context_net;

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

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

index ad0b3b381e..0db0c4d64c 100644

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

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

@@ -161,6 +161,7 @@ struct Service {

         pid_t main_pid, control_pid;

         int socket_fd;

+        bool socket_fd_selinux_context_net;

         int bus_endpoint_fd;

@@ -205,7 +206,7 @@ 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 68e21e60ac..00d5fd1192 100644

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

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

@@ -489,7 +489,8 @@ static void socket_dump(Unit *u, FILE *f, const char *prefix) {

                 "%sPassCredentials: %s\n"

                 "%sPassSecurity: %s\n"

                 "%sTCPCongestion: %s\n"

-                "%sRemoveOnStop: %s\n",

+                "%sRemoveOnStop: %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),

@@ -504,7 +505,8 @@ static void socket_dump(Unit *u, FILE *f, const char *prefix) {

                 prefix, yes_no(s->pass_cred),

                 prefix, yes_no(s->pass_sec),

                 prefix, strna(s->tcp_congestion),

-                prefix, yes_no(s->remove_on_stop));

+                prefix, yes_no(s->remove_on_stop),

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

         if (s->control_pid > 0)

                 fprintf(f,

@@ -1128,8 +1130,12 @@ static int socket_open_fds(Socket *s) {

                         continue;

                 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) {

                                 r = socket_instantiate_service(s);

                                 if (r < 0)

@@ -1821,7 +1827,7 @@ static void socket_enter_running(Socket *s, int cfd) {

                 unit_choose_id(UNIT(service), 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 eede70564a..a2e08998c0 100644

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

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

@@ -165,6 +165,8 @@ struct Socket {

         char *smack_ip_in;

         char *smack_ip_out;

+        bool selinux_context_from_net;

+

         char *user, *group;

 };

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

index 25a8b361b7..02b41f02d8 100644

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

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

@@ -31,6 +31,7 @@

 #ifdef HAVE_SELINUX

 #include <selinux/selinux.h>

 #include <selinux/label.h>

+#include <selinux/context.h>

 #endif

 #include "label.h"

@@ -41,6 +42,12 @@

 #include "smack-util.h"

 #ifdef HAVE_SELINUX

+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;

 #endif

@@ -243,6 +250,112 @@ 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 cb2ec79eea..ce1e5c3f57 100644

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

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

@@ -40,6 +40,8 @@ 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);