From 7f6c10626d7ece170bf5d85dd933b6382f636fa8 Mon Sep 17 00:00:00 2001
From: Stefano Brivio <sbrivio@redhat.com>
Date: Thu, 14 Nov 2024 23:41:52 +0100
Subject: [PATCH] selinux: Use auth_read_passwd() interface for all our
getpwnam() needs
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If passt or pasta are started as root, we need to read the passwd file
(be it /etc/passwd or whatever sssd provides) to find out UID and GID
of 'nobody' so that we can switch to it.
Instead of a bunch of allow rules for passwd_file_t and sssd macros,
use the more convenient auth_read_passwd() interface which should
cover our usage of getpwnam().
The existing rules weren't actually enough:
# strace -e openat passt -f
[...]
Started as root, will change to nobody.
openat(AT_FDCWD, "/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = 4
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 4
openat(AT_FDCWD, "/lib64/libnss_sss.so.2", O_RDONLY|O_CLOEXEC) = 4
openat(AT_FDCWD, "/var/lib/sss/mc/passwd", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
openat(AT_FDCWD, "/var/lib/sss/mc/passwd", O_RDONLY|O_CLOEXEC) = -1 EACCES (Permission denied)
openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 4
with corresponding SELinux warnings logged in audit.log.
Reported-by: Minxi Hou <mhou@redhat.com>
Analysed-by: Miloš Malik <mmalik@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
contrib/selinux/passt.te | 5 +----
contrib/selinux/pasta.te | 9 +--------
2 files changed, 2 insertions(+), 12 deletions(-)
diff --git a/contrib/selinux/passt.te b/contrib/selinux/passt.te
index 80bf780..c6cea34 100644
--- a/contrib/selinux/passt.te
+++ b/contrib/selinux/passt.te
@@ -47,8 +47,6 @@ require {
type port_t;
type http_port_t;
- type passwd_file_t;
-
class netlink_route_socket { bind create nlmsg_read };
type sysctl_net_t;
@@ -96,8 +94,7 @@ allow passt_t self:capability { sys_tty_config setpcap net_bind_service setuid s
allow passt_t self:cap_userns { setpcap sys_admin sys_ptrace };
allow passt_t self:user_namespace create;
-allow passt_t passwd_file_t:file read_file_perms;
-sssd_search_lib(passt_t)
+auth_read_passwd(passt_t)
allow passt_t proc_net_t:file read;
allow passt_t net_conf_t:file { open read };
diff --git a/contrib/selinux/pasta.te b/contrib/selinux/pasta.te
index 310383c..69be081 100644
--- a/contrib/selinux/pasta.te
+++ b/contrib/selinux/pasta.te
@@ -68,9 +68,6 @@ require {
type system_dbusd_t;
type systemd_hostnamed_t;
type systemd_systemctl_exec_t;
- type passwd_file_t;
- type sssd_public_t;
- type sssd_var_lib_t;
class dbus send_msg;
class system module_request;
class system status;
@@ -115,8 +112,7 @@ allow pasta_t self:capability { setpcap net_bind_service sys_tty_config dac_read
allow pasta_t self:cap_userns { setpcap sys_admin sys_ptrace net_admin net_bind_service };
allow pasta_t self:user_namespace create;
-allow pasta_t passwd_file_t:file read_file_perms;
-sssd_search_lib(pasta_t)
+auth_read_passwd(pasta_t)
domain_auto_trans(pasta_t, bin_t, unconfined_t);
domain_auto_trans(pasta_t, shell_exec_t, unconfined_t);
@@ -178,12 +174,9 @@ allow pasta_t init_t:system status;
allow pasta_t unconfined_t:dir search;
allow pasta_t unconfined_t:file read;
allow pasta_t unconfined_t:lnk_file read;
-allow pasta_t passwd_file_t:file { getattr open read };
allow pasta_t self:process { setpgid setcap };
allow pasta_t shell_exec_t:file { execute execute_no_trans map };
-allow pasta_t sssd_var_lib_t:dir search;
-allow pasta_t sssd_public_t:dir search;
allow pasta_t hostname_exec_t:file { execute execute_no_trans getattr open read map };
allow pasta_t system_dbusd_t:unix_stream_socket connectto;
allow pasta_t system_dbusd_t:dbus send_msg;