systemd/SOURCES/0847-manager-use-target-process-context-to-set-socket-con.patch

From 3f90090e70a5fa81bced17792fe08d9c46324da9 Mon Sep 17 00:00:00 2001
From: "Ted X. Toth" <txtoth@flycast.org>
Date: Thu, 13 Oct 2022 12:58:26 -0700
Subject: [PATCH] manager: use target process context to set socket context

Use target process context to set socket context when using SELinuxContextFromNet
not systemd's context. Currently when using the SELinuxContextFromNet option for
a socket activated services, systemd calls getcon_raw which returns init_t and
uses the resulting context to compute the context to be passed to the
setsockcreatecon call. A socket of type init_t is created and listened on and
this means that SELinux policy cannot be written to control which processes
(SELinux types) can connect to the socket since the ref policy allows all
'types' to connect to sockets of the type init_t. When security accessors see
that any process can connect to a socket this raises serious concerns. I have
spoken with SELinux contributors in person and on the mailing list and the
consensus is that the best solution is to use the target executables context
when computing the sockets context in all cases.

[zjs review/comment:

This removes the branch that was added in 16115b0a7b7cdf08fb38084d857d572d8a9088dc.
16115b0a7b7cdf08fb38084d857d572d8a9088dc did two things: it had the branch here
in 'socket_determine_selinux_label()' and a code in 'exec_child()' to call
'label_get_child_mls_label(socket_fd, command->path, &label)'.

Before this patch, the flow was:
'''
mac_selinux_get_child_mls_label:
  peercon = getpeercon_raw(socket_fd);
  if (!exec_label)
     exec_label = getfilecon_raw(exe);

socket_open_fds:
  if (params->selinux_context_net)                 #
     label = mac_selinux_get_our_label();          #  this part is removed
  else                                             #
     label = mac_selinux_get_create_label_from_exe(path);
  socket_address_listen_in_cgroup(s, &p->address, label);

exec_child():
   exec_context = mac_selinux_get_child_mls_label(fd, executable, context->selinux_context);
   setexeccon(exec_context);
'''
]

(cherry picked from commit 29dbc62d74f7b7881dc3136e68e03a03ea055b36)

Resolves: #2136738
---
 src/core/socket.c | 58 ++++++++++++++++++++---------------------------
 1 file changed, 24 insertions(+), 34 deletions(-)

diff --git a/src/core/socket.c b/src/core/socket.c
index d1ca0a07c5..8aa5463b25 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -1434,47 +1434,37 @@ static int socket_determine_selinux_label(Socket *s, char **ret) {
         assert(s);
         assert(ret);
 
-        if (s->selinux_context_from_net) {
-                /* If this is requested, get label from the network label */
-
-                r = mac_selinux_get_our_label(ret);
-                if (r == -EOPNOTSUPP)
-                        goto no_label;
-
-        } else {
-                /* Otherwise, get it from the executable we are about to start */
-                r = socket_instantiate_service(s);
-                if (r < 0)
-                        return r;
+        r = socket_instantiate_service(s);
+        if (r < 0)
+                return r;
 
-                if (!UNIT_ISSET(s->service))
-                        goto no_label;
-                service = SERVICE(UNIT_DEREF(s->service));
+        if (!UNIT_ISSET(s->service))
+                goto no_label;
+        service = SERVICE(UNIT_DEREF(s->service));
 
-                exec_context = service->exec_context.selinux_context;
-                if (exec_context) {
-                        char *con;
+        exec_context = service->exec_context.selinux_context;
+        if (exec_context) {
+                char *con;
 
-                        con = strdup(exec_context);
-                        if (!con)
-                                return -ENOMEM;
+                con = strdup(exec_context);
+                if (!con)
+                        return -ENOMEM;
 
-                        *ret = TAKE_PTR(con);
-                        return 0;
-                }
+                *ret = TAKE_PTR(con);
+                return 0;
+        }
 
-                c = service->exec_command[SERVICE_EXEC_START];
-                if (!c)
-                        goto no_label;
+        c = service->exec_command[SERVICE_EXEC_START];
+        if (!c)
+                goto no_label;
 
-                r = chase_symlinks(c->path, service->exec_context.root_directory, CHASE_PREFIX_ROOT, &path);
-                if (r < 0)
-                        goto no_label;
+        r = chase_symlinks(c->path, service->exec_context.root_directory, CHASE_PREFIX_ROOT, &path);
+        if (r < 0)
+                goto no_label;
 
-                r = mac_selinux_get_create_label_from_exe(path, ret);
-                if (IN_SET(r, -EPERM, -EOPNOTSUPP))
-                        goto no_label;
-        }
+        r = mac_selinux_get_create_label_from_exe(path, ret);
+        if (IN_SET(r, -EPERM, -EOPNOTSUPP))
+                goto no_label;
 
         return r;