1. 25 Sep, 2013 1 commit
  2. 24 Sep, 2013 5 commits
  3. 02 Oct, 2012 1 commit
    • David Howells's avatar
      KEYS: Reduce initial permissions on keys · 96b5c8fe
      David Howells authored
      Reduce the initial permissions on new keys to grant the possessor everything,
      view permission only to the user (so the keys can be seen in /proc/keys) and
      nothing else.
      
      This gives the creator a chance to adjust the permissions mask before other
      processes can access the new key or create a link to it.
      
      To aid with this, keyring_alloc() now takes a permission argument rather than
      setting the permissions itself.
      
      The following permissions are now set:
      
       (1) The user and user-session keyrings grant the user that owns them full
           permissions and grant a possessor everything bar SETATTR.
      
       (2) The process and thread keyrings grant the possessor full permissions but
           only grant the user VIEW.  This permits the user to see them in
           /proc/keys, but not to do anything with them.
      
       (3) Anonymous session keyrings grant the possessor full permissions, but only
           grant the user VIEW and READ.  This means that the user can see them in
           /proc/keys and can list them, but nothing else.  Possibly READ shouldn't
           be provided either.
      
       (4) Named session keyrings grant everything an anonymous session keyring does,
           plus they grant the user LINK permission.  The whole point of named
           session keyrings is that others can also subscribe to them.  Possibly this
           should be a separate permission to LINK.
      
       (5) The temporary session keyring created by call_sbin_request_key() gets the
           same permissions as an anonymous session keyring.
      
       (6) Keys created by add_key() get VIEW, SEARCH, LINK and SETATTR for the
           possessor, plus READ and/or WRITE if the key type supports them.  The used
           only gets VIEW now.
      
       (7) Keys created by request_key() now get the same as those created by
           add_key().
      Reported-by: default avatarLennart Poettering <lennart@poettering.net>
      Reported-by: default avatarStef Walter <stefw@redhat.com>
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      96b5c8fe
  4. 14 Sep, 2012 1 commit
    • Eric W. Biederman's avatar
      userns: Convert security/keys to the new userns infrastructure · 9a56c2db
      Eric W. Biederman authored
      - Replace key_user ->user_ns equality checks with kuid_has_mapping checks.
      - Use from_kuid to generate key descriptions
      - Use kuid_t and kgid_t and the associated helpers instead of uid_t and gid_t
      - Avoid potential problems with file descriptor passing by displaying
        keys in the user namespace of the opener of key status proc files.
      
      Cc: linux-security-module@vger.kernel.org
      Cc: keyrings@linux-nfs.org
      Cc: David Howells <dhowells@redhat.com>
      Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
      9a56c2db
  5. 02 Jul, 2012 1 commit
  6. 24 May, 2012 2 commits
    • Oleg Nesterov's avatar
      keys: kill the dummy key_replace_session_keyring() · dea649b8
      Oleg Nesterov authored
      After the previouse change key_replace_session_keyring() becomes a nop.
      Remove the dummy definition in key.h and update the callers in
      arch/*/kernel/signal.c.
      Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
      Acked-by: default avatarDavid Howells <dhowells@redhat.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Richard Kuo <rkuo@codeaurora.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Alexander Gordeev <agordeev@redhat.com>
      Cc: Chris Zankel <chris@zankel.net>
      Cc: David Smith <dsmith@redhat.com>
      Cc: "Frank Ch. Eigler" <fche@redhat.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Larry Woodman <lwoodman@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Ingo Molnar <mingo@elte.hu>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      dea649b8
    • Oleg Nesterov's avatar
      keys: change keyctl_session_to_parent() to use task_work_add() · 413cd3d9
      Oleg Nesterov authored
      Change keyctl_session_to_parent() to use task_work_add() and move
      key_replace_session_keyring() logic into task_work->func().
      
      Note that we do task_work_cancel() before task_work_add() to ensure that
      only one work can be pending at any time.  This is important, we must not
      allow user-space to abuse the parent's ->task_works list.
      
      The callback, replace_session_keyring(), checks PF_EXITING.  I guess this
      is not really needed but looks better.
      
      As a side effect, this fixes the (unlikely) race.  The callers of
      key_replace_session_keyring() and keyctl_session_to_parent() lack the
      necessary barriers, the parent can miss the request.
      
      Now we can remove task_struct->replacement_session_keyring and related
      code.
      Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
      Acked-by: default avatarDavid Howells <dhowells@redhat.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Richard Kuo <rkuo@codeaurora.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Alexander Gordeev <agordeev@redhat.com>
      Cc: Chris Zankel <chris@zankel.net>
      Cc: David Smith <dsmith@redhat.com>
      Cc: "Frank Ch. Eigler" <fche@redhat.com>
      Cc: Geert Uytterhoeven <geert@linux-m68k.org>
      Cc: Larry Woodman <lwoodman@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Ingo Molnar <mingo@elte.hu>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
      413cd3d9
  7. 15 May, 2012 1 commit
  8. 11 May, 2012 3 commits
    • David Howells's avatar
      KEYS: Add invalidation support · fd75815f
      David Howells authored
      Add support for invalidating a key - which renders it immediately invisible to
      further searches and causes the garbage collector to immediately wake up,
      remove it from keyrings and then destroy it when it's no longer referenced.
      
      It's better not to do this with keyctl_revoke() as that marks the key to start
      returning -EKEYREVOKED to searches when what is actually desired is to have the
      key refetched.
      
      To invalidate a key the caller must be granted SEARCH permission by the key.
      This may be too strict.  It may be better to also permit invalidation if the
      caller has any of READ, WRITE or SETATTR permission.
      
      The primary use for this is to evict keys that are cached in special keyrings,
      such as the DNS resolver or an ID mapper.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      fd75815f
    • David Howells's avatar
      KEYS: Do LRU discard in full keyrings · 31d5a79d
      David Howells authored
      Do an LRU discard in keyrings that are full rather than returning ENFILE.  To
      perform this, a time_t is added to the key struct and updated by the creation
      of a link to a key and by a key being found as the result of a search.  At the
      completion of a successful search, the keyrings in the path between the root of
      the search and the first found link to it also have their last-used times
      updated.
      
      Note that discarding a link to a key from a keyring does not necessarily
      destroy the key as there may be references held by other places.
      
      An alternate discard method that might suffice is to perform FIFO discard from
      the keyring, using the spare 2-byte hole in the keylist header as the index of
      the next link to be discarded.
      
      This is useful when using a keyring as a cache for DNS results or foreign
      filesystem IDs.
      
      
      This can be tested by the following.  As root do:
      
      	echo 1000 >/proc/sys/kernel/keys/root_maxkeys
      
      	kr=`keyctl newring foo @s`
      	for ((i=0; i<2000; i++)); do keyctl add user a$i a $kr; done
      
      Without this patch ENFILE should be reported when the keyring fills up.  With
      this patch, the keyring discards keys in an LRU fashion.  Note that the stored
      LRU time has a granularity of 1s.
      
      After doing this, /proc/key-users can be observed and should show that most of
      the 2000 keys have been discarded:
      
      	[root@andromeda ~]# cat /proc/key-users
      	    0:   517 516/516 513/1000 5249/20000
      
      The "513/1000" here is the number of quota-accounted keys present for this user
      out of the maximum permitted.
      
      In /proc/keys, the keyring shows the number of keys it has and the number of
      slots it has allocated:
      
      	[root@andromeda ~]# grep foo /proc/keys
      	200c64c4 I--Q--     1 perm 3b3f0000     0     0 keyring   foo: 509/509
      
      The maximum is (PAGE_SIZE - header) / key pointer size.  That's typically 509
      on a 64-bit system and 1020 on a 32-bit system.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      31d5a79d
    • David Howells's avatar
      KEYS: Perform RCU synchronisation on keys prior to key destruction · 65d87fe6
      David Howells authored
      Make the keys garbage collector invoke synchronize_rcu() prior to destroying
      keys with a zero usage count.  This means that a key can be examined under the
      RCU read lock in the safe knowledge that it won't get deallocated until after
      the lock is released - even if its usage count becomes zero whilst we're
      looking at it.
      
      This is useful in keyring search vs key link.  Consider a keyring containing a
      link to a key.  That link can be replaced in-place in the keyring without
      requiring an RCU copy-and-replace on the keyring contents without breaking a
      search underway on that keyring when the displaced key is released, provided
      the key is actually destroyed only after the RCU read lock held by the search
      algorithm is released.
      
      This permits __key_link() to replace a key without having to reallocate the key
      payload.  A key gets replaced if a new key being linked into a keyring has the
      same type and description.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Acked-by: default avatarJeff Layton <jlayton@redhat.com>
      65d87fe6
  9. 01 Mar, 2012 1 commit
  10. 19 Jan, 2012 2 commits
  11. 17 Jan, 2012 1 commit
  12. 26 Jul, 2011 1 commit
  13. 19 May, 2011 1 commit
    • Randy Dunlap's avatar
      Create Documentation/security/, · d410fa4e
      Randy Dunlap authored
      move LSM-, credentials-, and keys-related files from Documentation/
        to Documentation/security/,
      add Documentation/security/00-INDEX, and
      update all occurrences of Documentation/<moved_file>
        to Documentation/security/<moved_file>.
      d410fa4e
  14. 17 Mar, 2011 1 commit
    • David Howells's avatar
      KEYS: Improve /proc/keys · 78b7280c
      David Howells authored
      Improve /proc/keys by:
      
       (1) Don't attempt to summarise the payload of a negated key.  It won't have
           one.  To this end, a helper function - key_is_instantiated() has been
           added that allows the caller to find out whether the key is positively
           instantiated (as opposed to being uninstantiated or negatively
           instantiated).
      
       (2) Do show keys that are negative, expired or revoked rather than hiding
           them.  This requires an override flag (no_state_check) to be passed to
           search_my_process_keyrings() and keyring_search_aux() to suppress this
           check.
      
           Without this, keys that are possessed by the caller, but only grant
           permissions to the caller if possessed are skipped as the possession check
           fails.
      
           Keys that are visible due to user, group or other checks are visible with
           or without this patch.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      78b7280c
  15. 08 Mar, 2011 2 commits
  16. 20 Aug, 2010 1 commit
  17. 02 Sep, 2009 2 commits
    • David Howells's avatar
      KEYS: Add a keyctl to install a process's session keyring on its parent [try #6] · ee18d64c
      David Howells authored
      Add a keyctl to install a process's session keyring onto its parent.  This
      replaces the parent's session keyring.  Because the COW credential code does
      not permit one process to change another process's credentials directly, the
      change is deferred until userspace next starts executing again.  Normally this
      will be after a wait*() syscall.
      
      To support this, three new security hooks have been provided:
      cred_alloc_blank() to allocate unset security creds, cred_transfer() to fill in
      the blank security creds and key_session_to_parent() - which asks the LSM if
      the process may replace its parent's session keyring.
      
      The replacement may only happen if the process has the same ownership details
      as its parent, and the process has LINK permission on the session keyring, and
      the session keyring is owned by the process, and the LSM permits it.
      
      Note that this requires alteration to each architecture's notify_resume path.
      This has been done for all arches barring blackfin, m68k* and xtensa, all of
      which need assembly alteration to support TIF_NOTIFY_RESUME.  This allows the
      replacement to be performed at the point the parent process resumes userspace
      execution.
      
      This allows the userspace AFS pioctl emulation to fully emulate newpag() and
      the VIOCSETTOK and VIOCSETTOK2 pioctls, all of which require the ability to
      alter the parent process's PAG membership.  However, since kAFS doesn't use
      PAGs per se, but rather dumps the keys into the session keyring, the session
      keyring of the parent must be replaced if, for example, VIOCSETTOK is passed
      the newpag flag.
      
      This can be tested with the following program:
      
      	#include <stdio.h>
      	#include <stdlib.h>
      	#include <keyutils.h>
      
      	#define KEYCTL_SESSION_TO_PARENT	18
      
      	#define OSERROR(X, S) do { if ((long)(X) == -1) { perror(S); exit(1); } } while(0)
      
      	int main(int argc, char **argv)
      	{
      		key_serial_t keyring, key;
      		long ret;
      
      		keyring = keyctl_join_session_keyring(argv[1]);
      		OSERROR(keyring, "keyctl_join_session_keyring");
      
      		key = add_key("user", "a", "b", 1, keyring);
      		OSERROR(key, "add_key");
      
      		ret = keyctl(KEYCTL_SESSION_TO_PARENT);
      		OSERROR(ret, "KEYCTL_SESSION_TO_PARENT");
      
      		return 0;
      	}
      
      Compiled and linked with -lkeyutils, you should see something like:
      
      	[dhowells@andromeda ~]$ keyctl show
      	Session Keyring
      	       -3 --alswrv   4043  4043  keyring: _ses
      	355907932 --alswrv   4043    -1   \_ keyring: _uid.4043
      	[dhowells@andromeda ~]$ /tmp/newpag
      	[dhowells@andromeda ~]$ keyctl show
      	Session Keyring
      	       -3 --alswrv   4043  4043  keyring: _ses
      	1055658746 --alswrv   4043  4043   \_ user: a
      	[dhowells@andromeda ~]$ /tmp/newpag hello
      	[dhowells@andromeda ~]$ keyctl show
      	Session Keyring
      	       -3 --alswrv   4043  4043  keyring: hello
      	340417692 --alswrv   4043  4043   \_ user: a
      
      Where the test program creates a new session keyring, sticks a user key named
      'a' into it and then installs it on its parent.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      ee18d64c
    • David Howells's avatar
      KEYS: Add garbage collection for dead, revoked and expired keys. [try #6] · 5d135440
      David Howells authored
      Add garbage collection for dead, revoked and expired keys.  This involved
      erasing all links to such keys from keyrings that point to them.  At that
      point, the key will be deleted in the normal manner.
      
      Keyrings from which garbage collection occurs are shrunk and their quota
      consumption reduced as appropriate.
      
      Dead keys (for which the key type has been removed) will be garbage collected
      immediately.
      
      Revoked and expired keys will hang around for a number of seconds, as set in
      /proc/sys/kernel/keys/gc_delay before being automatically removed.  The default
      is 5 minutes.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      5d135440
  18. 03 Apr, 2009 1 commit
    • Pekka Enberg's avatar
      kmemtrace, security: fix linux/key.h header file dependencies · aa84442d
      Pekka Enberg authored
      Impact: cleanup
      
      We want to remove percpu.h from rcupdate.h (for upcoming kmemtrace
      changes), but this is not possible currently without breaking the
      build because key.h has an implicit include file dependency on
      rwsem.h:
      
          CC [M]  fs/cifs/cifs_spnego.o
        In file included from include/keys/user-type.h:15,
                         from fs/cifs/cifs_spnego.c:24:
        include/linux/key.h:128: error: field ‘sem’ has incomplete type
        make[2]: *** [fs/cifs/cifs_spnego.o] Error 1
        make[1]: *** [fs/cifs] Error 2
        make: *** [fs] Error 2
      
      Fix it by making the dependency explicit.
      Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
      Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
      LKML-Reference: <1237884886.25315.39.camel@penberg-laptop>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      aa84442d
  19. 13 Nov, 2008 4 commits
    • David Howells's avatar
      CRED: Make execve() take advantage of copy-on-write credentials · a6f76f23
      David Howells authored
      Make execve() take advantage of copy-on-write credentials, allowing it to set
      up the credentials in advance, and then commit the whole lot after the point
      of no return.
      
      This patch and the preceding patches have been tested with the LTP SELinux
      testsuite.
      
      This patch makes several logical sets of alteration:
      
       (1) execve().
      
           The credential bits from struct linux_binprm are, for the most part,
           replaced with a single credentials pointer (bprm->cred).  This means that
           all the creds can be calculated in advance and then applied at the point
           of no return with no possibility of failure.
      
           I would like to replace bprm->cap_effective with:
      
      	cap_isclear(bprm->cap_effective)
      
           but this seems impossible due to special behaviour for processes of pid 1
           (they always retain their parent's capability masks where normally they'd
           be changed - see cap_bprm_set_creds()).
      
           The following sequence of events now happens:
      
           (a) At the start of do_execve, the current task's cred_exec_mutex is
           	 locked to prevent PTRACE_ATTACH from obsoleting the calculation of
           	 creds that we make.
      
           (a) prepare_exec_creds() is then called to make a copy of the current
           	 task's credentials and prepare it.  This copy is then assigned to
           	 bprm->cred.
      
        	 This renders security_bprm_alloc() and security_bprm_free()
           	 unnecessary, and so they've been removed.
      
           (b) The determination of unsafe execution is now performed immediately
           	 after (a) rather than later on in the code.  The result is stored in
           	 bprm->unsafe for future reference.
      
           (c) prepare_binprm() is called, possibly multiple times.
      
           	 (i) This applies the result of set[ug]id binaries to the new creds
           	     attached to bprm->cred.  Personality bit clearance is recorded,
           	     but now deferred on the basis that the exec procedure may yet
           	     fail.
      
               (ii) This then calls the new security_bprm_set_creds().  This should
      	     calculate the new LSM and capability credentials into *bprm->cred.
      
      	     This folds together security_bprm_set() and parts of
      	     security_bprm_apply_creds() (these two have been removed).
      	     Anything that might fail must be done at this point.
      
               (iii) bprm->cred_prepared is set to 1.
      
      	     bprm->cred_prepared is 0 on the first pass of the security
      	     calculations, and 1 on all subsequent passes.  This allows SELinux
      	     in (ii) to base its calculations only on the initial script and
      	     not on the interpreter.
      
           (d) flush_old_exec() is called to commit the task to execution.  This
           	 performs the following steps with regard to credentials:
      
      	 (i) Clear pdeath_signal and set dumpable on certain circumstances that
      	     may not be covered by commit_creds().
      
               (ii) Clear any bits in current->personality that were deferred from
                   (c.i).
      
           (e) install_exec_creds() [compute_creds() as was] is called to install the
           	 new credentials.  This performs the following steps with regard to
           	 credentials:
      
               (i) Calls security_bprm_committing_creds() to apply any security
                   requirements, such as flushing unauthorised files in SELinux, that
                   must be done before the credentials are changed.
      
      	     This is made up of bits of security_bprm_apply_creds() and
      	     security_bprm_post_apply_creds(), both of which have been removed.
      	     This function is not allowed to fail; anything that might fail
      	     must have been done in (c.ii).
      
               (ii) Calls commit_creds() to apply the new credentials in a single
                   assignment (more or less).  Possibly pdeath_signal and dumpable
                   should be part of struct creds.
      
      	 (iii) Unlocks the task's cred_replace_mutex, thus allowing
      	     PTRACE_ATTACH to take place.
      
               (iv) Clears The bprm->cred pointer as the credentials it was holding
                   are now immutable.
      
               (v) Calls security_bprm_committed_creds() to apply any security
                   alterations that must be done after the creds have been changed.
                   SELinux uses this to flush signals and signal handlers.
      
           (f) If an error occurs before (d.i), bprm_free() will call abort_creds()
           	 to destroy the proposed new credentials and will then unlock
           	 cred_replace_mutex.  No changes to the credentials will have been
           	 made.
      
       (2) LSM interface.
      
           A number of functions have been changed, added or removed:
      
           (*) security_bprm_alloc(), ->bprm_alloc_security()
           (*) security_bprm_free(), ->bprm_free_security()
      
           	 Removed in favour of preparing new credentials and modifying those.
      
           (*) security_bprm_apply_creds(), ->bprm_apply_creds()
           (*) security_bprm_post_apply_creds(), ->bprm_post_apply_creds()
      
           	 Removed; split between security_bprm_set_creds(),
           	 security_bprm_committing_creds() and security_bprm_committed_creds().
      
           (*) security_bprm_set(), ->bprm_set_security()
      
           	 Removed; folded into security_bprm_set_creds().
      
           (*) security_bprm_set_creds(), ->bprm_set_creds()
      
           	 New.  The new credentials in bprm->creds should be checked and set up
           	 as appropriate.  bprm->cred_prepared is 0 on the first call, 1 on the
           	 second and subsequent calls.
      
           (*) security_bprm_committing_creds(), ->bprm_committing_creds()
           (*) security_bprm_committed_creds(), ->bprm_committed_creds()
      
           	 New.  Apply the security effects of the new credentials.  This
           	 includes closing unauthorised files in SELinux.  This function may not
           	 fail.  When the former is called, the creds haven't yet been applied
           	 to the process; when the latter is called, they have.
      
       	 The former may access bprm->cred, the latter may not.
      
       (3) SELinux.
      
           SELinux has a number of changes, in addition to those to support the LSM
           interface changes mentioned above:
      
           (a) The bprm_security_struct struct has been removed in favour of using
           	 the credentials-under-construction approach.
      
           (c) flush_unauthorized_files() now takes a cred pointer and passes it on
           	 to inode_has_perm(), file_has_perm() and dentry_open().
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Acked-by: default avatarJames Morris <jmorris@namei.org>
      Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      a6f76f23
    • David Howells's avatar
      CRED: Inaugurate COW credentials · d84f4f99
      David Howells authored
      Inaugurate copy-on-write credentials management.  This uses RCU to manage the
      credentials pointer in the task_struct with respect to accesses by other tasks.
      A process may only modify its own credentials, and so does not need locking to
      access or modify its own credentials.
      
      A mutex (cred_replace_mutex) is added to the task_struct to control the effect
      of PTRACE_ATTACHED on credential calculations, particularly with respect to
      execve().
      
      With this patch, the contents of an active credentials struct may not be
      changed directly; rather a new set of credentials must be prepared, modified
      and committed using something like the following sequence of events:
      
      	struct cred *new = prepare_creds();
      	int ret = blah(new);
      	if (ret < 0) {
      		abort_creds(new);
      		return ret;
      	}
      	return commit_creds(new);
      
      There are some exceptions to this rule: the keyrings pointed to by the active
      credentials may be instantiated - keyrings violate the COW rule as managing
      COW keyrings is tricky, given that it is possible for a task to directly alter
      the keys in a keyring in use by another task.
      
      To help enforce this, various pointers to sets of credentials, such as those in
      the task_struct, are declared const.  The purpose of this is compile-time
      discouragement of altering credentials through those pointers.  Once a set of
      credentials has been made public through one of these pointers, it may not be
      modified, except under special circumstances:
      
        (1) Its reference count may incremented and decremented.
      
        (2) The keyrings to which it points may be modified, but not replaced.
      
      The only safe way to modify anything else is to create a replacement and commit
      using the functions described in Documentation/credentials.txt (which will be
      added by a later patch).
      
      This patch and the preceding patches have been tested with the LTP SELinux
      testsuite.
      
      This patch makes several logical sets of alteration:
      
       (1) execve().
      
           This now prepares and commits credentials in various places in the
           security code rather than altering the current creds directly.
      
       (2) Temporary credential overrides.
      
           do_coredump() and sys_faccessat() now prepare their own credentials and
           temporarily override the ones currently on the acting thread, whilst
           preventing interference from other threads by holding cred_replace_mutex
           on the thread being dumped.
      
           This will be replaced in a future patch by something that hands down the
           credentials directly to the functions being called, rather than altering
           the task's objective credentials.
      
       (3) LSM interface.
      
           A number of functions have been changed, added or removed:
      
           (*) security_capset_check(), ->capset_check()
           (*) security_capset_set(), ->capset_set()
      
           	 Removed in favour of security_capset().
      
           (*) security_capset(), ->capset()
      
           	 New.  This is passed a pointer to the new creds, a pointer to the old
           	 creds and the proposed capability sets.  It should fill in the new
           	 creds or return an error.  All pointers, barring the pointer to the
           	 new creds, are now const.
      
           (*) security_bprm_apply_creds(), ->bprm_apply_creds()
      
           	 Changed; now returns a value, which will cause the process to be
           	 killed if it's an error.
      
           (*) security_task_alloc(), ->task_alloc_security()
      
           	 Removed in favour of security_prepare_creds().
      
           (*) security_cred_free(), ->cred_free()
      
           	 New.  Free security data attached to cred->security.
      
           (*) security_prepare_creds(), ->cred_prepare()
      
           	 New. Duplicate any security data attached to cred->security.
      
           (*) security_commit_creds(), ->cred_commit()
      
           	 New. Apply any security effects for the upcoming installation of new
           	 security by commit_creds().
      
           (*) security_task_post_setuid(), ->task_post_setuid()
      
           	 Removed in favour of security_task_fix_setuid().
      
           (*) security_task_fix_setuid(), ->task_fix_setuid()
      
           	 Fix up the proposed new credentials for setuid().  This is used by
           	 cap_set_fix_setuid() to implicitly adjust capabilities in line with
           	 setuid() changes.  Changes are made to the new credentials, rather
           	 than the task itself as in security_task_post_setuid().
      
           (*) security_task_reparent_to_init(), ->task_reparent_to_init()
      
           	 Removed.  Instead the task being reparented to init is referred
           	 directly to init's credentials.
      
      	 NOTE!  This results in the loss of some state: SELinux's osid no
      	 longer records the sid of the thread that forked it.
      
           (*) security_key_alloc(), ->key_alloc()
           (*) security_key_permission(), ->key_permission()
      
           	 Changed.  These now take cred pointers rather than task pointers to
           	 refer to the security context.
      
       (4) sys_capset().
      
           This has been simplified and uses less locking.  The LSM functions it
           calls have been merged.
      
       (5) reparent_to_kthreadd().
      
           This gives the current thread the same credentials as init by simply using
           commit_thread() to point that way.
      
       (6) __sigqueue_alloc() and switch_uid()
      
           __sigqueue_alloc() can't stop the target task from changing its creds
           beneath it, so this function gets a reference to the currently applicable
           user_struct which it then passes into the sigqueue struct it returns if
           successful.
      
           switch_uid() is now called from commit_creds(), and possibly should be
           folded into that.  commit_creds() should take care of protecting
           __sigqueue_alloc().
      
       (7) [sg]et[ug]id() and co and [sg]et_current_groups.
      
           The set functions now all use prepare_creds(), commit_creds() and
           abort_creds() to build and check a new set of credentials before applying
           it.
      
           security_task_set[ug]id() is called inside the prepared section.  This
           guarantees that nothing else will affect the creds until we've finished.
      
           The calling of set_dumpable() has been moved into commit_creds().
      
           Much of the functionality of set_user() has been moved into
           commit_creds().
      
           The get functions all simply access the data directly.
      
       (8) security_task_prctl() and cap_task_prctl().
      
           security_task_prctl() has been modified to return -ENOSYS if it doesn't
           want to handle a function, or otherwise return the return value directly
           rather than through an argument.
      
           Additionally, cap_task_prctl() now prepares a new set of credentials, even
           if it doesn't end up using it.
      
       (9) Keyrings.
      
           A number of changes have been made to the keyrings code:
      
           (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have
           	 all been dropped and built in to the credentials functions directly.
           	 They may want separating out again later.
      
           (b) key_alloc() and search_process_keyrings() now take a cred pointer
           	 rather than a task pointer to specify the security context.
      
           (c) copy_creds() gives a new thread within the same thread group a new
           	 thread keyring if its parent had one, otherwise it discards the thread
           	 keyring.
      
           (d) The authorisation key now points directly to the credentials to extend
           	 the search into rather pointing to the task that carries them.
      
           (e) Installing thread, process or session keyrings causes a new set of
           	 credentials to be created, even though it's not strictly necessary for
           	 process or session keyrings (they're shared).
      
      (10) Usermode helper.
      
           The usermode helper code now carries a cred struct pointer in its
           subprocess_info struct instead of a new session keyring pointer.  This set
           of credentials is derived from init_cred and installed on the new process
           after it has been cloned.
      
           call_usermodehelper_setup() allocates the new credentials and
           call_usermodehelper_freeinfo() discards them if they haven't been used.  A
           special cred function (prepare_usermodeinfo_creds()) is provided
           specifically for call_usermodehelper_setup() to call.
      
           call_usermodehelper_setkeys() adjusts the credentials to sport the
           supplied keyring as the new session keyring.
      
      (11) SELinux.
      
           SELinux has a number of changes, in addition to those to support the LSM
           interface changes mentioned above:
      
           (a) selinux_setprocattr() no longer does its check for whether the
           	 current ptracer can access processes with the new SID inside the lock
           	 that covers getting the ptracer's SID.  Whilst this lock ensures that
           	 the check is done with the ptracer pinned, the result is only valid
           	 until the lock is released, so there's no point doing it inside the
           	 lock.
      
      (12) is_single_threaded().
      
           This function has been extracted from selinux_setprocattr() and put into
           a file of its own in the lib/ directory as join_session_keyring() now
           wants to use it too.
      
           The code in SELinux just checked to see whether a task shared mm_structs
           with other tasks (CLONE_VM), but that isn't good enough.  We really want
           to know if they're part of the same thread group (CLONE_THREAD).
      
      (13) nfsd.
      
           The NFS server daemon now has to use the COW credentials to set the
           credentials it is going to use.  It really needs to pass the credentials
           down to the functions it calls, but it can't do that until other patches
           in this series have been applied.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Acked-by: default avatarJames Morris <jmorris@namei.org>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      d84f4f99
    • David Howells's avatar
      CRED: Separate per-task-group keyrings from signal_struct · bb952bb9
      David Howells authored
      Separate per-task-group keyrings from signal_struct and dangle their anchor
      from the cred struct rather than the signal_struct.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Reviewed-by: default avatarJames Morris <jmorris@namei.org>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      bb952bb9
    • David Howells's avatar
      KEYS: Alter use of key instantiation link-to-keyring argument · 8bbf4976
      David Howells authored
      Alter the use of the key instantiation and negation functions' link-to-keyring
      arguments.  Currently this specifies a keyring in the target process to link
      the key into, creating the keyring if it doesn't exist.  This, however, can be
      a problem for copy-on-write credentials as it means that the instantiating
      process can alter the credentials of the requesting process.
      
      This patch alters the behaviour such that:
      
       (1) If keyctl_instantiate_key() or keyctl_negate_key() are given a specific
           keyring by ID (ringid >= 0), then that keyring will be used.
      
       (2) If keyctl_instantiate_key() or keyctl_negate_key() are given one of the
           special constants that refer to the requesting process's keyrings
           (KEY_SPEC_*_KEYRING, all <= 0), then:
      
           (a) If sys_request_key() was given a keyring to use (destringid) then the
           	 key will be attached to that keyring.
      
           (b) If sys_request_key() was given a NULL keyring, then the key being
           	 instantiated will be attached to the default keyring as set by
           	 keyctl_set_reqkey_keyring().
      
       (3) No extra link will be made.
      
      Decision point (1) follows current behaviour, and allows those instantiators
      who've searched for a specifically named keyring in the requestor's keyring so
      as to partition the keys by type to still have their named keyrings.
      
      Decision point (2) allows the requestor to make sure that the key or keys that
      get produced by request_key() go where they want, whilst allowing the
      instantiator to request that the key is retained.  This is mainly useful for
      situations where the instantiator makes a secondary request, the key for which
      should be retained by the initial requestor:
      
      	+-----------+        +--------------+        +--------------+
      	|           |        |              |        |              |
      	| Requestor |------->| Instantiator |------->| Instantiator |
      	|           |        |              |        |              |
      	+-----------+        +--------------+        +--------------+
      	           request_key()           request_key()
      
      This might be useful, for example, in Kerberos, where the requestor requests a
      ticket, and then the ticket instantiator requests the TGT, which someone else
      then has to go and fetch.  The TGT, however, should be retained in the
      keyrings of the requestor, not the first instantiator.  To make this explict
      an extra special keyring constant is also added.
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Reviewed-by: default avatarJames Morris <jmorris@namei.org>
      Signed-off-by: default avatarJames Morris <jmorris@namei.org>
      8bbf4976
  20. 12 Oct, 2008 1 commit
  21. 29 Apr, 2008 5 commits
  22. 09 Jan, 2008 1 commit
  23. 17 Oct, 2007 1 commit
    • David Howells's avatar
      KEYS: Make request_key() and co fundamentally asynchronous · 76181c13
      David Howells authored
      Make request_key() and co fundamentally asynchronous to make it easier for
      NFS to make use of them.  There are now accessor functions that do
      asynchronous constructions, a wait function to wait for construction to
      complete, and a completion function for the key type to indicate completion
      of construction.
      
      Note that the construction queue is now gone.  Instead, keys under
      construction are linked in to the appropriate keyring in advance, and that
      anyone encountering one must wait for it to be complete before they can use
      it.  This is done automatically for userspace.
      
      The following auxiliary changes are also made:
      
       (1) Key type implementation stuff is split from linux/key.h into
           linux/key-type.h.
      
       (2) AF_RXRPC provides a way to allocate null rxrpc-type keys so that AFS does
           not need to call key_instantiate_and_link() directly.
      
       (3) Adjust the debugging macros so that they're -Wformat checked even if
           they are disabled, and make it so they can be enabled simply by defining
           __KDEBUG to be consistent with other code of mine.
      
       (3) Documentation.
      
      [alan@lxorguk.ukuu.org.uk: keys: missing word in documentation]
      Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
      Signed-off-by: default avatarAlan Cox <alan@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      76181c13