Dominick Grift <dac.override@xxxxxxxxx> writes: > Stephen Smalley <sds@xxxxxxxxxxxxx> writes: > >> On 2/15/19 10:25 AM, Stephen Smalley wrote: >>> On 2/15/19 10:05 AM, Stephen Smalley wrote: >>>> On 2/15/19 10:03 AM, Stephen Smalley wrote: >>>>> On 2/15/19 10:00 AM, Paul Moore wrote: >>>>>> On Fri, Feb 15, 2019 at 9:51 AM Stephen Smalley >>>>>> <sds@xxxxxxxxxxxxx> wrote: >>>>>>> Add basic MLS policy support to mdp. Declares >>>>>>> two sensitivities and two categories, defines >>>>>>> mls constraints for all permissions requiring >>>>>>> dominance (ala MCS), assigns the system-high >>>>>>> level to initial SID contexts and the default user >>>>>>> level, and assigns system-low level to filesystems. >>>>>>> >>>>>>> Also reworks the fs_use and genfscon rules to only >>>>>>> generate rules for filesystems that are configured >>>>>>> in the kernel. In some cases this depends on a specific >>>>>>> config option for security xattrs, in other cases security >>>>>>> xattrs are unconditionally supported by a given filesystem >>>>>>> if the filesystem is enabled, and in some cases the filesystem >>>>>>> is always enabled in the kernel. Dropped obsolete pseudo >>>>>>> filesystems. >>>>>>> >>>>>>> NB The list of fs_use_* and genfscon rules emitted by mdp >>>>>>> is very incomplete compared to refpolicy or Android sepolicy. >>>>>>> We should probably expand it. >>>>>>> >>>>>>> Usage: >>>>>>> scripts/selinux/mdp/mdp -m policy.conf file_contexts >>>>>>> checkpolicy -M -o policy policy.conf >>>>>>> >>>>>>> Then install the resulting policy and file_contexts as usual. >>>>>>> >>>>>>> Signed-off-by: Stephen Smalley <sds@xxxxxxxxxxxxx> >>>>>>> --- >>>>>>> v3 fixes up the file contexts generation code to also use >>>>>>> SYSTEMLOW and >>>>>>> collapse down to a single fprintf call per line. >>>>>>> scripts/selinux/mdp/mdp.c | 131 >>>>>>> ++++++++++++++++++++++++++++++-------- >>>>>>> 1 file changed, 103 insertions(+), 28 deletions(-) >>>>>> >>>>>> This is great Stephen, thanks for working on this - and rather quickly >>>>>> too! For those who don't follow the GitHub issues, I just opened an >>>>>> issue yesterday mentioning it would be nice to add MLS support to the >>>>>> mdp tool. >>>>>> >>>>>> Are you planning to keep playing with this? I'm asking not because I >>>>>> think it needs more work to be worthwhile, but rather I don't want to >>>>>> merge something that you want to continue working on. If you are >>>>>> happy with this latest patch I think it is okay to merge this into >>>>>> selinux/next, even at this late stage, simply because it is not part >>>>>> of a built kernel, but rather a developer's tool. >>>>> >>>>> No, I think I'm done for now unless you find a problem with >>>>> it. Absent some compelling use case for mdp it is hard to justify >>>>> spending any more time on it. >>>> >>>> Note however that the instructions in >>>> Documentation/admin-guide/LSM/SELinux.rst just say to run >>>> scripts/selinux/install_policy.sh and since that doesn't pass -m to >>>> mdp or -M to checkpolicy, no one will use this support unless they >>>> do it all by hand. >>> >>> FWIW, a Fedora system wouldn't come up cleanly with this policy. >>> Partly appears to be due to systemd having embedded security >>> contexts specific to Fedora/refpolicy into its own configurations >>> and partly due to MLS denials. I don't even know if it would work >>> before this change though... >> >> Couldn't seem to get a mdp-generated policy to boot on Fedora even in >> permissive, before or after this change. I assume it has to do with >> leaking of contexts outside of the policy and/or missing config files >> from the dummy policy (e.g. /etc/selinux/targeted/contexts/ has >> systemd_contexts and other userspace config files that don't exist in >> the mdp policy). More evidence of the irrelevance of mdp... > > Oh, right you need a "dbus_contexts" file probably. DBUS refuses to > start without it, and these day's without dbus no system My dssp2-minimal [1] policy is my alternative to mdp. https://github.com/DefenSec/dssp2-minimal It is not quite as simple as mpd but it think it is decent balance between having something useful and still easy to read. > >> >>> >>>> >>>>> >>>>>> >>>>>>> diff --git a/scripts/selinux/mdp/mdp.c b/scripts/selinux/mdp/mdp.c >>>>>>> index 073fe7537f6c..4223e2fea441 100644 >>>>>>> --- a/scripts/selinux/mdp/mdp.c >>>>>>> +++ b/scripts/selinux/mdp/mdp.c >>>>>>> @@ -33,6 +33,7 @@ >>>>>>> #include <unistd.h> >>>>>>> #include <string.h> >>>>>>> #include <sys/socket.h> >>>>>>> +#include <linux/kconfig.h> >>>>>>> >>>>>>> static void usage(char *name) >>>>>>> { >>>>>>> @@ -95,10 +96,31 @@ int main(int argc, char *argv[]) >>>>>>> } >>>>>>> fprintf(fout, "\n"); >>>>>>> >>>>>>> - /* NOW PRINT OUT MLS STUFF */ >>>>>>> + /* print out mls declarations and constraints */ >>>>>>> if (mls) { >>>>>>> - printf("MLS not yet implemented\n"); >>>>>>> - exit(1); >>>>>>> + fprintf(fout, "sensitivity s0;\n"); >>>>>>> + fprintf(fout, "sensitivity s1;\n"); >>>>>>> + fprintf(fout, "dominance { s0 s1 }\n"); >>>>>>> + fprintf(fout, "category c0;\n"); >>>>>>> + fprintf(fout, "category c1;\n"); >>>>>>> + fprintf(fout, "level s0:c0.c1;\n"); >>>>>>> + fprintf(fout, "level s1:c0.c1;\n"); >>>>>>> +#define SYSTEMLOW "s0" >>>>>>> +#define SYSTEMHIGH "s1:c0.c1" >>>>>>> + for (i = 0; secclass_map[i].name; i++) { >>>>>>> + struct security_class_mapping *map = >>>>>>> &secclass_map[i]; >>>>>>> + >>>>>>> + fprintf(fout, "mlsconstrain %s {\n", >>>>>>> map->name); >>>>>>> + for (j = 0; map->perms[j]; j++) >>>>>>> + fprintf(fout, "\t%s\n", >>>>>>> map->perms[j]); >>>>>>> + /* >>>>>>> + * This requires all subjects and >>>>>>> objects to be >>>>>>> + * single-level (l2 eq h2), and that the >>>>>>> subject >>>>>>> + * level dominate the object level (h1 dom h2) >>>>>>> + * in order to have any permissions to it. >>>>>>> + */ >>>>>>> + fprintf(fout, "} (l2 eq h2 and h1 dom >>>>>>> h2);\n\n"); >>>>>>> + } >>>>>>> } >>>>>>> >>>>>>> /* types, roles, and allows */ >>>>>>> @@ -108,34 +130,87 @@ int main(int argc, char *argv[]) >>>>>>> for (i = 0; secclass_map[i].name; i++) >>>>>>> fprintf(fout, "allow base_t base_t:%s *;\n", >>>>>>> secclass_map[i].name); >>>>>>> - fprintf(fout, "user user_u roles { base_r };\n"); >>>>>>> - fprintf(fout, "\n"); >>>>>>> + fprintf(fout, "user user_u roles { base_r }"); >>>>>>> + if (mls) >>>>>>> + fprintf(fout, " level %s range %s - %s", SYSTEMHIGH, >>>>>>> + SYSTEMLOW, SYSTEMHIGH); >>>>>>> + fprintf(fout, ";\n"); >>>>>>> + >>>>>>> +#define USERROLETYPE "user_u:base_r:base_t" >>>>>>> >>>>>>> /* default sids */ >>>>>>> for (i = 1; i < initial_sid_to_string_len; i++) >>>>>>> - fprintf(fout, "sid %s user_u:base_r:base_t\n", >>>>>>> initial_sid_to_string[i]); >>>>>>> + fprintf(fout, "sid %s " USERROLETYPE "%s\n", >>>>>>> + initial_sid_to_string[i], mls ? ":" >>>>>>> SYSTEMHIGH : ""); >>>>>>> fprintf(fout, "\n"); >>>>>>> >>>>>>> - fprintf(fout, "fs_use_xattr ext2 user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_xattr ext3 user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_xattr ext4 user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_xattr jfs user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_xattr xfs user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_xattr reiserfs >>>>>>> user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_xattr jffs2 user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_xattr gfs2 user_u:base_r:base_t;\n"); >>>>>>> - >>>>>>> - fprintf(fout, "fs_use_task eventpollfs >>>>>>> user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_task pipefs user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_task sockfs user_u:base_r:base_t;\n"); >>>>>>> - >>>>>>> - fprintf(fout, "fs_use_trans mqueue user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_trans devpts user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_trans hugetlbfs >>>>>>> user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_trans tmpfs user_u:base_r:base_t;\n"); >>>>>>> - fprintf(fout, "fs_use_trans shm user_u:base_r:base_t;\n"); >>>>>>> - >>>>>>> - fprintf(fout, "genfscon proc / user_u:base_r:base_t\n"); >>>>>>> +#define FS_USE(behavior, fstype) \ >>>>>>> + fprintf(fout, "fs_use_%s %s " USERROLETYPE "%s;\n", \ >>>>>>> + behavior, fstype, mls ? ":" SYSTEMLOW : "") >>>>>>> + >>>>>>> + /* >>>>>>> + * Filesystems whose inode labels can be fetched via getxattr. >>>>>>> + */ >>>>>>> +#ifdef CONFIG_EXT2_FS_SECURITY >>>>>>> + FS_USE("xattr", "ext2"); >>>>>>> +#endif >>>>>>> +#ifdef CONFIG_EXT3_FS_SECURITY >>>>>>> + FS_USE("xattr", "ext3"); >>>>>>> +#endif >>>>>>> +#ifdef CONFIG_EXT4_FS_SECURITY >>>>>>> + FS_USE("xattr", "ext4"); >>>>>>> +#endif >>>>>>> +#ifdef CONFIG_JFS_SECURITY >>>>>>> + FS_USE("xattr", "jfs"); >>>>>>> +#endif >>>>>>> +#ifdef CONFIG_REISERFS_FS_SECURITY >>>>>>> + FS_USE("xattr", "reiserfs"); >>>>>>> +#endif >>>>>>> +#ifdef CONFIG_JFFS2_FS_SECURITY >>>>>>> + FS_USE("xattr", "jffs2"); >>>>>>> +#endif >>>>>>> +#ifdef CONFIG_XFS_FS >>>>>>> + FS_USE("xattr", "xfs"); >>>>>>> +#endif >>>>>>> +#ifdef CONFIG_GFS2_FS >>>>>>> + FS_USE("xattr", "gfs2"); >>>>>>> +#endif >>>>>>> + >>>>>>> + /* >>>>>>> + * Filesystems whose inodes are labeled from allocating task. >>>>>>> + */ >>>>>>> + FS_USE("task", "pipefs"); >>>>>>> + FS_USE("task", "sockfs"); >>>>>>> +#ifdef CONFIG_POSIX_MQUEUE >>>>>>> + FS_USE("task", "mqueue"); >>>>>>> +#endif >>>>>>> + >>>>>>> + /* >>>>>>> + * Filesystems whose inode labels are computed from both >>>>>>> + * the allocating task and the superblock label. >>>>>>> + */ >>>>>>> +#ifdef CONFIG_UNIX98_PTYS >>>>>>> + FS_USE("trans", "devpts"); >>>>>>> +#endif >>>>>>> +#ifdef CONFIG_HUGETLBFS >>>>>>> + FS_USE("trans", "hugetlbfs"); >>>>>>> +#endif >>>>>>> +#ifdef CONFIG_TMPFS >>>>>>> + FS_USE("trans", "tmpfs"); >>>>>>> +#endif >>>>>>> + >>>>>>> + >>>>>>> +#define GENFSCON(fstype, prefix) \ >>>>>>> + fprintf(fout, "genfscon %s %s " USERROLETYPE "%s\n", \ >>>>>>> + fstype, prefix, mls ? ":" SYSTEMLOW : "") >>>>>>> + >>>>>>> + /* >>>>>>> + * Filesystems whose inodes are labeled from path prefix match >>>>>>> + * relative to the filesystem root. Depending on the >>>>>>> filesystem, >>>>>>> + * only a single label for all inodes may be supported. >>>>>>> + */ >>>>>>> + GENFSCON("proc", "/"); >>>>>>> + GENFSCON("selinuxfs", "/"); >>>>>>> >>>>>>> fclose(fout); >>>>>>> >>>>>>> @@ -144,8 +219,8 @@ int main(int argc, char *argv[]) >>>>>>> printf("Wrote policy, but cannot open %s for >>>>>>> writing\n", ctxout); >>>>>>> usage(argv[0]); >>>>>>> } >>>>>>> - fprintf(fout, "/ user_u:base_r:base_t\n"); >>>>>>> - fprintf(fout, "/.* user_u:base_r:base_t\n"); >>>>>>> + fprintf(fout, "/ " USERROLETYPE "%s\n", mls ? ":" >>>>>>> SYSTEMLOW : ""); >>>>>>> + fprintf(fout, "/.* " USERROLETYPE "%s\n", mls ? ":" >>>>>>> SYSTEMLOW : ""); >>>>>>> fclose(fout); >>>>>>> >>>>>>> return 0; >>>>>>> -- >>>>>>> 2.20.1 >>>>>>> >>>>>> >>>>>> >>>>> >>>> >>> >> -- Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02 https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02 Dominick Grift
