From e9a201d25be662218e5ea250a32c3b093a66f75b Mon Sep 17 00:00:00 2001 From: Chris Lindee Date: Wed, 26 Jan 2022 20:56:15 -0600 Subject: [PATCH] [Draft] pam_zfs_key: Add SELinux policy for PAM module Provide a policy that allows pam_zfs_key to work on an SELinux protected system without giving excessive access to the PAM module. This way, any exploited application using PAM remains unable to destroy datasets or do anything similarly damaging. Alas, libzfs opens the device with both read & write permissions, so any policy that doesn't label the /dev/zfs device specially could open up other devices to be exploited. Unfortunately, relabeling the device has the potential to impact existing systems, so it is not part of this commit. --- config/user-pam-sepolicy.m4 | 24 +++++ config/user.m4 | 1 + configure.ac | 1 + contrib/pam_zfs_key/Makefile.am | 6 ++ contrib/pam_zfs_key/selinux/.gitignore | 2 + contrib/pam_zfs_key/selinux/Makefile.am | 16 +++ .../selinux/pam_zfs_key-selinux.spec | 69 ++++++++++++ contrib/pam_zfs_key/selinux/pam_zfs_key.fc | 1 + contrib/pam_zfs_key/selinux/pam_zfs_key.if | 101 ++++++++++++++++++ contrib/pam_zfs_key/selinux/pam_zfs_key.te | 17 +++ 10 files changed, 238 insertions(+) create mode 100644 config/user-pam-sepolicy.m4 create mode 100644 contrib/pam_zfs_key/selinux/.gitignore create mode 100644 contrib/pam_zfs_key/selinux/Makefile.am create mode 100644 contrib/pam_zfs_key/selinux/pam_zfs_key-selinux.spec create mode 100644 contrib/pam_zfs_key/selinux/pam_zfs_key.fc create mode 100644 contrib/pam_zfs_key/selinux/pam_zfs_key.if create mode 100644 contrib/pam_zfs_key/selinux/pam_zfs_key.te diff --git a/config/user-pam-sepolicy.m4 b/config/user-pam-sepolicy.m4 new file mode 100644 index 000000000000..f200e88e1792 --- /dev/null +++ b/config/user-pam-sepolicy.m4 @@ -0,0 +1,24 @@ +AC_DEFUN([ZFS_AC_CONFIG_USER_PAM_SELINUX], [ + AC_ARG_WITH([pam-selinux], + AS_HELP_STRING([--with-pam-selinux=@<:@/usr/share/selinux/devel@:>@], + [build pam_zfs_key module SELinux policy [[default: check]]]), + [ + AS_IF([test "x$with_pam_selinux" = xyes], + with_pam_selinux=/usr/share/selinux/devel) + ], + [with_pam_selinux=no]) + + AS_IF([test "x$with_pam_selinux" != "xno"], [ + AS_IF([test -f "$with_pam_selinux/Makefile"], + [selinux_makefile="$with_pam_selinux/Makefile"], + [ + AC_MSG_FAILURE([ + *** SELinux policy development tools missing. + ]) + with_pam_selinux=no + ] + ) + ]) + AC_SUBST(selinux_makefile) + AM_CONDITIONAL([WITH_PAM_SELINUX], [test "x$with_pam_selinux" != xno]) +]) diff --git a/config/user.m4 b/config/user.m4 index f450af47e04d..ecfe490070bf 100644 --- a/config/user.m4 +++ b/config/user.m4 @@ -26,6 +26,7 @@ AC_DEFUN([ZFS_AC_CONFIG_USER], [ ZFS_AC_CONFIG_USER_AIO_H ZFS_AC_CONFIG_USER_CLOCK_GETTIME ZFS_AC_CONFIG_USER_PAM + ZFS_AC_CONFIG_USER_PAM_SELINUX ZFS_AC_CONFIG_USER_RUNSTATEDIR ZFS_AC_CONFIG_USER_MAKEDEV_IN_SYSMACROS ZFS_AC_CONFIG_USER_MAKEDEV_IN_MKDEV diff --git a/configure.ac b/configure.ac index 990958bafa1e..555b0b7de3d8 100644 --- a/configure.ac +++ b/configure.ac @@ -101,6 +101,7 @@ AC_CONFIG_FILES([ contrib/initramfs/scripts/Makefile contrib/initramfs/scripts/local-top/Makefile contrib/pam_zfs_key/Makefile + contrib/pam_zfs_key/selinux/Makefile contrib/pyzfs/Makefile contrib/pyzfs/setup.py contrib/zcp/Makefile diff --git a/contrib/pam_zfs_key/Makefile.am b/contrib/pam_zfs_key/Makefile.am index f0f2550afccb..db30d0ca33f1 100644 --- a/contrib/pam_zfs_key/Makefile.am +++ b/contrib/pam_zfs_key/Makefile.am @@ -17,3 +17,9 @@ pam_zfs_key_la_LDFLAGS = -version-info 1:0:0 -avoid-version -module -shared pam_zfs_key_la_LIBADD += -lpam $(LIBCRYPTO_LIBS) dist_pamconfigs_DATA = zfs_key + +if WITH_PAM_SELINUX +SUBDIRS = selinux +endif + +DIST_SUBDIRS = selinux diff --git a/contrib/pam_zfs_key/selinux/.gitignore b/contrib/pam_zfs_key/selinux/.gitignore new file mode 100644 index 000000000000..823eb56ce055 --- /dev/null +++ b/contrib/pam_zfs_key/selinux/.gitignore @@ -0,0 +1,2 @@ +/*.pp +/tmp/ diff --git a/contrib/pam_zfs_key/selinux/Makefile.am b/contrib/pam_zfs_key/selinux/Makefile.am new file mode 100644 index 000000000000..f75977b2cdf8 --- /dev/null +++ b/contrib/pam_zfs_key/selinux/Makefile.am @@ -0,0 +1,16 @@ + +if WITH_PAM_SELINUX + +refpoldir = $(datadir)/selinux/packages +refpol_DATA = pam_zfs_key.pp + +refpolifdir = $(datadir)/selinux/devel/include/contrib +refpolif_DATA = pam_zfs_key.if + +pam_zfs_key.pp: pam_zfs_key.te pam_zfs_key.fc pam_zfs_key.if + $(MAKE) -f $(selinux_makefile) $@ + +clean-local: + rm -f *.tc *.pp + +endif diff --git a/contrib/pam_zfs_key/selinux/pam_zfs_key-selinux.spec b/contrib/pam_zfs_key/selinux/pam_zfs_key-selinux.spec new file mode 100644 index 000000000000..db6f5d28dfca --- /dev/null +++ b/contrib/pam_zfs_key/selinux/pam_zfs_key-selinux.spec @@ -0,0 +1,69 @@ + +%define relabel_files() \ +restorecon -R /usr/lib64/security/pam_zfs_key.so; \ +restorecon -R /dev/zfs; \ +restorecon -R /var/run/pam_zfs_key; \ + +%define selinux_policyver 34.23-1 + +Name: @PACKAGE@ +Version: @VERSION@ +Release: @RELEASE@%{?dist} +Summary: SELinux policy module for pam_zfs_key + +Name: pam_zfs_key-selinux +Version: 1.0 +Release: 1%{?dist} + + +License: @ZFS_META_LICENSE@ +URL: https://github.com/openzfs/zfs +Source0: pam_zfs_key.pp +Source1: pam_zfs_key.if + + +Requires: policycoreutils, libselinux-utils +Requires(post): selinux-policy-base >= %{selinux_policyver}, policycoreutils +Requires(postun): policycoreutils +BuildArch: noarch + +%description +This package installs and sets up the SELinux policy security module for +pam_zfs_key. + +%install +install -d %{buildroot}%{_datadir}/selinux/packages +install -m 644 %{SOURCE0} %{buildroot}%{_datadir}/selinux/packages +install -d %{buildroot}%{_datadir}/selinux/devel/include/contrib +install -m 644 %{SOURCE1} %{buildroot}%{_datadir}/selinux/devel/include/contrib/ +install -d %{buildroot}/etc/selinux/targeted/contexts/users/ + + +%post +semodule -n -i %{_datadir}/selinux/packages/pam_zfs_key.pp +if /usr/sbin/selinuxenabled ; then + /usr/sbin/load_policy + %relabel_files + +fi; +exit 0 + +%postun +if [ $1 -eq 0 ]; then + semodule -n -r pam_zfs_key + if /usr/sbin/selinuxenabled ; then + /usr/sbin/load_policy + %relabel_files + + fi; +fi; +exit 0 + +%files +%attr(0600,root,root) %{_datadir}/selinux/packages/pam_zfs_key.pp +%{_datadir}/selinux/devel/include/contrib/pam_zfs_key.if + + +%changelog +* Thu Jan 13 2022 YOUR NAME 1.0-1 +- Initial version diff --git a/contrib/pam_zfs_key/selinux/pam_zfs_key.fc b/contrib/pam_zfs_key/selinux/pam_zfs_key.fc new file mode 100644 index 000000000000..c42434a5b693 --- /dev/null +++ b/contrib/pam_zfs_key/selinux/pam_zfs_key.fc @@ -0,0 +1 @@ +/var/run/pam_zfs_key(/.*)? gen_context(system_u:object_r:pam_var_run_t,s0) diff --git a/contrib/pam_zfs_key/selinux/pam_zfs_key.if b/contrib/pam_zfs_key/selinux/pam_zfs_key.if new file mode 100644 index 000000000000..e3eb9e533735 --- /dev/null +++ b/contrib/pam_zfs_key/selinux/pam_zfs_key.if @@ -0,0 +1,101 @@ + +## policy for pam_zfs_key + +######################################## +## +## Allow domain to query datasets on ZFS. +## +## +## +## Domain allowed access. +## +## +# +interface(`pam_zfs_key_query',` + gen_require(` + type device_t; + ') + + dnl Using ifdef() keeps `sepolgen-ifgen' from complaining + define(`ZFS_IOC') + ifdef(`ZFS_IOC', ` + define(`ZFS_IOC_POOL_STATS', `0x5a05') + define(`ZFS_IOC_OBJSET_STATS', `0x5a12') + define(`ZFS_IOC_POOL_GET_PROPS', `0x5a27') + define(`ZFS_IOC_LOAD_KEY', `0x5a49') + define(`ZFS_IOC_UNLOAD_KEY', `0x5a4a') + define(`ZFS_IOC_CHANGE_KEY', `0x5a4b') + ') + + allow $1 device_t:chr_file { open ioctl }; + allowxperm $1 device_t:chr_file ioctl ZFS_IOC_OBJSET_STATS; + + # While /dev/zfs does not support read() or write(), libzfs opens it with + # O_RDWR, meaning we need these permissions. Remove these if ZFS changes + # to using the Linux specialization O_PATH (or O_EXEC). + allow $1 device_t:chr_file { read write }; +') + +######################################## +## +## Allow domain to open and close a session on the pam_zfs_key PAM module. +## +## +## +## Domain allowed access. +## +## +# +interface(`pam_zfs_key_session',` + gen_require(` + type device_t; + type fs_t; + type pam_var_run_t; + type user_home_dir_t; + ') + + files_pid_filetrans($1, pam_var_run_t, dir, "pam_zfs_key") + + pam_zfs_key_query($1) + allowxperm $1 device_t:chr_file ioctl { ZFS_IOC_LOAD_KEY ZFS_IOC_UNLOAD_KEY }; + + # The zfs_open() function returns both a zfs handle and a zpool handle for + # its containing pool; as part of the zpool fetching, the function grabs + # the pool stats. Despite marking the pool as unavailable, the library + # will still query the pool properties to check for read-only status. + dontauditxperm $1 device_t:chr_file ioctl ZFS_IOC_POOL_STATS; + + # Needed to determine if the zpool is read-only (if so, the dataset must be + # mounted read-only too). + allowxperm $1 device_t:chr_file ioctl ZFS_IOC_POOL_GET_PROPS; + + allow $1 fs_t:filesystem { mount unmount }; + allow $1 user_home_dir_t:dir mounton; +') + +######################################## +## +## Allow domain to change password on the pam_zfs_key PAM module. +## +## +## +## Domain allowed access. +## +## +# +interface(`pam_zfs_key_password',` + gen_require(` + type device_t; + ') + + pam_zfs_key_query($1) + + # The zfs_open() function returns both a zfs handle and a zpool handle for + # its containing pool; as part of the zpool fetching, the function grabs + # the pool stats. The zpool information does not appear to be used when + # changing the key, but cannot be skipped easily, so silence the denial. + dontauditxperm $1 device_t:chr_file ioctl ZFS_IOC_POOL_STATS; + + auditallowxperm $1 device_t:chr_file ioctl ZFS_IOC_CHANGE_KEY; + allowxperm $1 device_t:chr_file ioctl ZFS_IOC_CHANGE_KEY; +') diff --git a/contrib/pam_zfs_key/selinux/pam_zfs_key.te b/contrib/pam_zfs_key/selinux/pam_zfs_key.te new file mode 100644 index 000000000000..04d745803183 --- /dev/null +++ b/contrib/pam_zfs_key/selinux/pam_zfs_key.te @@ -0,0 +1,17 @@ +policy_module(pam_zfs_key, 1.0.0) + +######################################## +# +# pam_zfs_key local policy +# + +gen_require(` + type local_login_t; + type sshd_t; + + type passwd_t; +') +pam_zfs_key_session(local_login_t) +pam_zfs_key_session(sshd_t) + +pam_zfs_key_password(passwd_t)