On Wed, Feb 19, 2020 at 06:03:02PM +0000, Richard Haines wrote:
> I've been building selinux-testsuite tests for various filesystems and
> have come across an unlabeled issue when testing. Stephen thinks that
> this is a bug sometimes seen with labeled NFS, where the top-level
> mounted directory shows up with unlabeled_t initially, then later gets
> refreshed to a valid context.
>
> I've put together a test script, policy module and mount prog to
> facilitate debugging this issue. I've set out how I tested this on a
> Fedora 31 system below, if any problems let me know.
Thanks! Adding the nfs group to the cc.
I seem to recall a report of a similar bug in the Red Hat bugzilla, that
I spent a little time investigating and couldn't pin down. I'll see if
I can dig that up.
--b.
>
> The nfs.sh script:
> MOUNT=`stat --print %m .`
> TESTDIR=`pwd`
> systemctl start nfs-server
> exportfs -orw,no_root_squash,security_label localhost:$MOUNT
> mkdir -p /mnt/selinux-testsuite
> runcon -t test_nfs_unlabeled_bug ./mount -f nfs4 -s localhost:$TESTDIR
> -t /mnt/selinux-testsuite -o
> "nfsvers=4.2,proto=tcp,clientaddr=127.0.0.1,addr=127.0.0.1" -v
> umount /mnt/selinux-testsuite
> exportfs -u localhost:$MOUNT
> systemctl stop nfs-server
>
> Install mount.c, unlabeled_bug.te and nfs.sh
>
> Build mount prog:
> cc mount.c -o mount -Wall
> Then:
> chcon -t bin_t ./mount
>
> Build policy module and install:
> make -f /usr/share/selinux/devel/Makefile unlabeled_bug.pp
> semodule -i unlabeled_bug.pp
>
> Clean audit log:
> > /var/log/audit/audit.log
>
> run ./nfs.sh
>
> Check audit log:
> audit2allow -p /etc/selinux/targeted/policy/policy.31 <
> /var/log/audit/audit.log
>
> Should see:
> #============= test_nfs_unlabeled_bug ==============
> allow test_nfs_unlabeled_bug unlabeled_t:dir search;
>
> Once done:
> semodule -r unlabeled_bug
> /* cc mount.c -o mount -Wall */
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <unistd.h>
> #include <errno.h>
> #include <stdbool.h>
> #include <sys/mount.h>
>
> static void print_usage(char *progname)
> {
> fprintf(stderr,
> "usage: %s [-s src] -t tgt [-f fs_type] [-o options]\n"
> "Where:\n\t"
> "-s Source path\n\t"
> "-t Target path\n\t"
> "-f Filesystem type\n\t"
> "-o Options list (comma separated list)\n\t"
> "-v Print information.\n", progname);
> exit(-1);
> }
>
> int main(int argc, char *argv[])
> {
> int opt, result, save_err, flags = 0;
> char *src = NULL, *tgt = NULL, *fs_type = NULL, *opts = NULL;
> bool verbose = false;
>
> while ((opt = getopt(argc, argv, "s:t:f:o:v")) != -1) {
> switch (opt) {
> case 's':
> src = optarg;
> break;
> case 't':
> tgt = optarg;
> break;
> case 'f':
> fs_type = optarg;
> break;
> case 'o':
> opts = optarg;
> break;
> case 'v':
> verbose = true;
> break;
> default:
> print_usage(argv[0]);
> }
> }
>
> if (!tgt)
> print_usage(argv[0]);
>
> if (verbose)
> printf("Mounting\n\tsrc: %s\n\ttgt: %s\n\tfs_type: %s flags: 0x%x\n\topts: %s\n",
> src, tgt, fs_type, flags, opts);
>
> result = mount(src, tgt, fs_type, flags, opts);
> save_err = errno;
> if (result < 0) {
> fprintf(stderr, "Failed mount(2): %s\n", strerror(errno));
> return save_err;
> }
>
> return 0;
> }
>
> policy_module(unlabeled_bug, 1.0)
>
> require {
> role unconfined_r;
> type bin_t,user_devpts_t,nfs_t,kernel_t;
> class file { entrypoint execute read };
> class capability { sys_admin };
> class system { module_request };
> class chr_file { append getattr read write };
> class dir { search };
> class filesystem { mount };
> }
>
> #============= test_nfs_unlabeled_bug ==============
> type test_nfs_unlabeled_bug;
> role unconfined_r types test_nfs_unlabeled_bug;
> files_type(test_nfs_unlabeled_bug)
> domain_type(test_nfs_unlabeled_bug)
> allow test_nfs_unlabeled_bug bin_t:file { entrypoint execute read };
> files_mounton_default(test_nfs_unlabeled_bug)
> allow test_nfs_unlabeled_bug bin_t:file map;
> allow test_nfs_unlabeled_bug default_t:dir mounton;
> allow test_nfs_unlabeled_bug self:capability sys_admin;
> allow test_nfs_unlabeled_bug kernel_t:system module_request;
> allow test_nfs_unlabeled_bug nfs_t:dir search;
> allow test_nfs_unlabeled_bug nfs_t:filesystem mount;
> allow test_nfs_unlabeled_bug user_devpts_t:chr_file { append getattr read write };
>
> #allow test_nfs_unlabeled_bug unlabeled_t:dir search;
>
