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manager: use target process context to set socket context

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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 16115b0a7b.
16115b0a7b 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);
'''
]
This commit is contained in:
Ted X. Toth 2022-10-13 12:58:26 -07:00 committed by Zbigniew Jędrzejewski-Szmek
parent 8ff92848a6
commit 29dbc62d74
1 changed files with 28 additions and 40 deletions
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68
src/core/socket.c
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@ -1407,52 +1407,40 @@ 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 the label from the network label */
Unit *service;
ExecCommand *c;
const char *exec_context;
_cleanup_free_ char *path = NULL;
r = mac_selinux_get_our_label(ret);
if (r == -EOPNOTSUPP)
goto no_label;
r = socket_load_service_unit(s, -1, &service);
if (r == -ENODATA)
goto no_label;
if (r < 0)
return r;
} else {
/* Otherwise, get it from the executable we are about to start. */
exec_context = SERVICE(service)->exec_context.selinux_context;
if (exec_context) {
char *con;
Unit *service;
ExecCommand *c;
const char *exec_context;
_cleanup_free_ char *path = NULL;
con = strdup(exec_context);
if (!con)
return -ENOMEM;
r = socket_load_service_unit(s, -1, &service);
if (r == -ENODATA)
goto no_label;
if (r < 0)
return r;
exec_context = SERVICE(service)->exec_context.selinux_context;
if (exec_context) {
char *con;
con = strdup(exec_context);
if (!con)
return -ENOMEM;
*ret = TAKE_PTR(con);
return 0;
}
c = SERVICE(service)->exec_command[SERVICE_EXEC_START];
if (!c)
goto no_label;
r = chase_symlinks(c->path, SERVICE(service)->exec_context.root_directory, CHASE_PREFIX_ROOT, &path, NULL);
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;
*ret = TAKE_PTR(con);
return 0;
}
c = SERVICE(service)->exec_command[SERVICE_EXEC_START];
if (!c)
goto no_label;
r = chase_symlinks(c->path, SERVICE(service)->exec_context.root_directory, CHASE_PREFIX_ROOT, &path, NULL);
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;
return r;
no_label: