Only server which map unknown users to guest will allow
access using a non-null NTLMv2_Response.
For Samba it's the "map to guest = bad user" option.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=11913
Signed-off-by: Stefan Metzmacher <metze@samba.org>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Only server which map unknown users to guest will allow
access using a non-null NTChallengeResponse.
For Samba it's the "map to guest = bad user" option.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=11913
Signed-off-by: Stefan Metzmacher <metze@samba.org>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Only server which map unknown users to guest will allow
access using a non-null LMChallengeResponse.
For Samba it's the "map to guest = bad user" option.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=11913
Signed-off-by: Stefan Metzmacher <metze@samba.org>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>
See [MS-NLMP] 3.2.5.1.2 Server Receives an AUTHENTICATE_MESSAGE from the Client:
...
Set NullSession to FALSE
If (AUTHENTICATE_MESSAGE.UserNameLen == 0 AND
AUTHENTICATE_MESSAGE.NtChallengeResponse.Length == 0 AND
(AUTHENTICATE_MESSAGE.LmChallengeResponse == Z(1)
OR
AUTHENTICATE_MESSAGE.LmChallengeResponse.Length == 0))
-- Special case: client requested anonymous authentication
Set NullSession to TRUE
...
Only server which map unknown users to guest will allow
access using a non-null NTChallengeResponse.
For Samba it's the "map to guest = bad user" option.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=11913
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Merge first patchbomb from Andrew Morton:
- a few minor cifs fixes
- dma-debug upadtes
- ocfs2
- slab
- about half of MM
- procfs
- kernel/exit.c
- panic.c tweaks
- printk upates
- lib/ updates
- checkpatch updates
- fs/binfmt updates
- the drivers/rtc tree
- nilfs
- kmod fixes
- more kernel/exit.c
- various other misc tweaks and fixes
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits)
exit: pidns: fix/update the comments in zap_pid_ns_processes()
exit: pidns: alloc_pid() leaks pid_namespace if child_reaper is exiting
exit: exit_notify: re-use "dead" list to autoreap current
exit: reparent: call forget_original_parent() under tasklist_lock
exit: reparent: avoid find_new_reaper() if no children
exit: reparent: introduce find_alive_thread()
exit: reparent: introduce find_child_reaper()
exit: reparent: document the ->has_child_subreaper checks
exit: reparent: s/while_each_thread/for_each_thread/ in find_new_reaper()
exit: reparent: fix the cross-namespace PR_SET_CHILD_SUBREAPER reparenting
exit: reparent: fix the dead-parent PR_SET_CHILD_SUBREAPER reparenting
exit: proc: don't try to flush /proc/tgid/task/tgid
exit: release_task: fix the comment about group leader accounting
exit: wait: drop tasklist_lock before psig->c* accounting
exit: wait: don't use zombie->real_parent
exit: wait: cleanup the ptrace_reparented() checks
usermodehelper: kill the kmod_thread_locker logic
usermodehelper: don't use CLONE_VFORK for ____call_usermodehelper()
fs/hfs/catalog.c: fix comparison bug in hfs_cat_keycmp
nilfs2: fix the nilfs_iget() vs. nilfs_new_inode() races
...
Replace all __constant_foo to foo() except in smb2status.h (1700 lines to
update).
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Steve French <sfrench@samba.org>
Cc: Jeff Layton <jlayton@poochiereds.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A user complained that they were unable to login to their cifs share
after a kernel update. From the wiretrace we can see that the server
returns different UIDs as response to NTLMSSP_NEGOTIATE and NTLMSSP_AUTH
phases.
With changes in the authentication code, we no longer set the
cifs_sess->Suid returned in response to the NTLM_AUTH phase and continue
to use the UID sent in response to the NTLMSSP_NEGOTIATE phase. This
results in the server denying access to the user when the user attempts
to do a tcon connect.
See https://bugzilla.redhat.com/show_bug.cgi?id=1163927
A test kernel containing patch was tested successfully by the user.
Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Steve French <steve.french@primarydata.com>
cifs provides two dummy functions 'sess_auth_lanman' and
'sess_auth_kerberos' for the case in which the respective
features are not defined. However, the caller is also under
an #ifdef, so we just get warnings about unused code:
fs/cifs/sess.c:1109:1: warning: 'sess_auth_kerberos' defined but not used [-Wunused-function]
sess_auth_kerberos(struct sess_data *sess_data)
Removing the dead functions gets rid of the warnings without
any downsides that I can see.
(Yalin Wang reported the identical problem and fix so added him)
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Yalin Wang <yalin.wang@sonymobile.com>
Signed-off-by: Steve French <smfrench@gmail.com>
When kzalloc fails, we will end up doing NULL pointer derefrence
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@samsung.com>
Signed-off-by: Steve French <smfrench@gmail.com>
The recent session setup patch set
(cifs-Separate-rawntlmssp-auth-from-CIFS_SessSetup.patch)
had introduced a trivial sparse build warning.
Signed-off-by: Steve French <smfrench@gmail.com>
Cc: Sachin Prabhu <sprabhu@redhat.com>
Separate rawntlmssp authentication from CIFS_SessSetup(). Also cleanup
CIFS_SessSetup() since we no longer do any auth within it.
Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Reviewed-by: Shirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: Steve French <smfrench@gmail.com>
In preparation for splitting CIFS_SessSetup() into smaller more
manageable chunks, we first add helper functions.
We then proceed to split out lanman auth out of CIFS_SessSetup()
Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Reviewed-by: Shirish Pargaonkar <spargaonkar@suse.com>
Signed-off-by: Steve French <smfrench@gmail.com>
This allows users to use LANMAN authentication on servers which support
unencapsulated authentication.
The patch fixes a regression where users using plaintext authentication
were no longer able to do so because of changed bought in by patch
3f618223dchttps://bugzilla.redhat.com/show_bug.cgi?id=1011621
Reported-by: Panos Kavalagios <Panagiotis.Kavalagios@eurodyn.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Currently, we try to ensure that we use vcnum of 0 on the first
established session on a connection and then try to use a different
vcnum on each session after that.
This is a little odd, since there's no real reason to use a different
vcnum for each SMB session. I can only assume there was some confusion
between SMB sessions and VCs. That's somewhat understandable since they
both get created during SESSION_SETUP, but the documentation indicates
that they are really orthogonal. The comment on max_vcs in particular
looks quite misguided. An SMB session is already uniquely identified
by the SMB UID value -- there's no need to again uniquely ID with a
VC.
Furthermore, a vcnum of 0 is a cue to the server that it should release
any resources that were previously held by the client. This sounds like
a good thing, until you consider that:
a) it totally ignores the fact that other programs on the box (e.g.
smbclient) might have connections established to the server. Using a
vcnum of 0 causes them to get kicked off.
b) it causes problems with NAT. If several clients are connected to the
same server via the same NAT'ed address, whenever one connects to the
server it kicks off all the others, which then reconnect and kick off
the first one...ad nauseum.
I don't see any reason to ignore the advice in "Implementing CIFS" which
has a comprehensive treatment of virtual circuits. In there, it states
"...and contrary to the specs the client should always use a VcNumber of
one, never zero."
Have the client just use a hardcoded vcnum of 1, and stop abusing the
special behavior of vcnum 0.
Reported-by: Sauron99@gmx.de <sauron99@gmx.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Add a variable specific to NTLMSSP authentication to determine
whether to exchange keys during negotiation and authentication phases.
Since session key for smb1 is per smb connection, once a very first
sesion is established, there is no need for key exchange during
subsequent session setups. As a result, smb1 session setup code sets this
variable as false.
Since session key for smb2 and smb3 is per smb connection, we need to
exchange keys to generate session key for every sesion being established.
As a result, smb2/3 session setup code sets this variable as true.
Acked-by: Jeff Layton <jlayton@samba.org>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Move the post (successful) session setup code to respective dialect routines.
For smb1, session key is per smb connection.
For smb2/smb3, session key is per smb session.
If client and server do not require signing, free session key for smb1/2/3.
If client and server require signing
smb1 - Copy (kmemdup) session key for the first session to connection.
Free session key of that and subsequent sessions on this connection.
smb2 - For every session, keep the session key and free it when the
session is being shutdown.
smb3 - For every session, generate the smb3 signing key using the session key
and then free the session key.
There are two unrelated line formatting changes as well.
Reviewed-by: Jeff Layton <jlayton@samba.org>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>
The max string length definitions for user name, domain name, password,
and share name have been moved into their own header file in uapi so the
mount helper can use autoconf to define them instead of keeping the
kernel side and userland side definitions in sync manually. The names
have also been standardized with a "CIFS" prefix and "LEN" suffix.
Signed-off-by: Scott Lovenberg <scott.lovenberg@gmail.com>
Reviewed-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Steve French <smfrench@gmail.com>
For cifs_set_cifscreds() in "fs/cifs/connect.c", 'desc' buffer length
is 'CIFSCREDS_DESC_SIZE' (56 is less than 256), and 'ses->domainName'
length may be "255 + '\0'".
The related sprintf() may cause memory overflow, so need extend related
buffer enough to hold all things.
It is also necessary to be sure of 'ses->domainName' must be less than
256, and define the related macro instead of hard code number '256'.
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Reviewed-by: Scott Lovenberg <scott.lovenberg@gmail.com>
CC: <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Now that we track what sort of NEGOTIATE response was received, stop
mandating that every session on a socket use the same type of auth.
Push that decision out into the session setup code, and make the sectype
a per-session property. This should allow us to mix multiple sectypes on
a socket as long as they are compatible with the NEGOTIATE response.
With this too, we can now eliminate the ses->secFlg field since that
info is redundant and harder to work with than a securityEnum.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>
Currently, we determine this according to flags in the sec_mode, flags
in the global_secflags and via other methods. That makes the semantics
very hard to follow and there are corner cases where we don't handle
this correctly.
Add a new bool to the TCP_Server_Info that acts as a simple flag to tell
us whether signing is enabled on this connection or not, and fix up the
places that need to determine this to use that flag.
This is a bit weird for the SMB2 case, where signing is per-session.
SMB2 needs work in this area already though. The existing SMB2 code has
similar logic to what we're using here, so there should be no real
change in behavior. These changes should make it easier to implement
per-session signing in the future though.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>
This field is completely unused:
CIFS_SES_W9X is completely unused. CIFS_SES_LANMAN and CIFS_SES_OS2
are set but never checked. CIFS_SES_NT4 is checked, but never set.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>
These look pretty cargo-culty to me, but let's be certain. Leave
them in place for now. Pop a WARN if it ever does happen. Also,
move to a more standard idiom for setting the "server" pointer.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>
...rc is always set to 0.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>
It's not obvious from reading the macro names that these macros
are for debugging. Convert the names to a single more typical
kernel style cifs_dbg macro.
cERROR(1, ...) -> cifs_dbg(VFS, ...)
cFYI(1, ...) -> cifs_dbg(FYI, ...)
cFYI(DBG2, ...) -> cifs_dbg(NOISY, ...)
Move the terminating format newline from the macro to the call site.
Add CONFIG_CIFS_DEBUG function cifs_vfs_err to emit the
"CIFS VFS: " prefix for VFS messages.
Size is reduced ~ 1% when CONFIG_CIFS_DEBUG is set (default y)
$ size fs/cifs/cifs.ko*
text data bss dec hex filename
265245 2525 132 267902 4167e fs/cifs/cifs.ko.new
268359 2525 132 271016 422a8 fs/cifs/cifs.ko.old
Other miscellaneous changes around these conversions:
o Miscellaneous typo fixes
o Add terminating \n's to almost all formats and remove them
from the macros to be more kernel style like. A few formats
previously had defective \n's
o Remove unnecessary OOM messages as kmalloc() calls dump_stack
o Coalesce formats to make grep easier,
added missing spaces when coalescing formats
o Use %s, __func__ instead of embedded function name
o Removed unnecessary "cifs: " prefixes
o Convert kzalloc with multiply to kcalloc
o Remove unused cifswarn macro
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
This replaces calls to kmalloc followed by memcpy with a single call to
kmemdup. This was found via make coccicheck.
Signed-off-by: Silviu-Mihai Popescu <silviupopescu1990@gmail.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Calling key_revoke here isn't ideal as further requests for the key will
end up returning -EKEYREVOKED until it gets purged from the cache. What we
really intend here is to force a new upcall on the next request_key.
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
For null user mounts, do not invoke string length function
during session setup.
Cc: <stable@kernel.org
Reported-and-Tested-by: Chris Clayton <chris2553@googlemail.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>
We should check that we're not copying memory from beyond the end of the
blob.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
to reflect the unicode encoding used by CIFS protocol.
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Acked-by: Jeff Layton <jlayton@samba.org>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Re-posting a patch originally posted by Oskar Liljeblad after
rebasing on 3.2.
Modify cifs to assume that the supplied password is encoded according
to iocharset. Before this patch passwords would be treated as
raw 8-bit data, which made authentication with Unicode passwords impossible
(at least passwords with characters > 0xFF).
The previous code would as a side effect accept passwords encoded with
ISO 8859-1, since Unicode < 0x100 basically is ISO 8859-1. Software which
relies on that will no longer support password chars > 0x7F unless it also
uses iocharset=iso8859-1. (mount.cifs does not care about the encoding so
it will work as expected.)
Signed-off-by: Oskar Liljeblad <oskar@osk.mine.nu>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Tested-by: A <nimbus1_03087@yahoo.com>
Signed-off-by: Steve French <smfrench@gmail.com>
server->maxBuf is the maximum SMB size (including header) that the
server can handle. CIFSMaxBufSize is the maximum amount of data (sans
header) that the client can handle. Currently maxBuf is being capped at
CIFSMaxBufSize + the max headers size, and the two values are used
somewhat interchangeably in the code.
This makes little sense as these two values are not related at all.
Separate them and make sure the code uses the right values in the right
places.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Currently, we mirror the same size back to the server that it sends us.
That makes little sense. Instead we should be sending the server the
maximum buffer size that we can handle -- CIFSMaxBufSize minus the
4 byte RFC1001 header.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
When using NTLMSSP authentication mechanism, if server mandates
signing, keep the flags in type 3 messages of the NTLMSSP exchange
same as in type 1 messages (i.e. keep the indicated capabilities same).
Some of the servers such as Samba, expect the flags such as
Negotiate_Key_Exchange in type 3 message of NTLMSSP exchange as well.
Some servers like Windows do not.
https://bugzilla.samba.org/show_bug.cgi?id=8212
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
This is the same patch as originally posted, just with some merge
conflicts fixed up...
Currently, the ByteCount is usually converted to host-endian on receive.
This is confusing however, as we need to keep two sets of routines for
accessing it, and keep track of when to use each routine. Munging
received packets like this also limits when the signature can be
calulated.
Simplify the code by keeping the received ByteCount in little-endian
format. This allows us to eliminate a set of routines for accessing it
and we can now drop the *_le suffixes from the accessor functions since
that's now implied.
While we're at it, switch all of the places that read the ByteCount
directly to use the get_bcc inline which should also clean up some
unaligned accesses.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
There is one big endian field in the cifs protocol, the RFC1001
length, which cifs code (unlike in the smb2 code) had been handling as
u32 until the last possible moment, when it was converted to be32 (its
native form) before sending on the wire. To remove the last sparse
endian warning, and to make this consistent with the smb2
implementation (which always treats the fields in their
native size and endianness), convert all uses of smb_buf_length to
be32.
This version incorporates Christoph's comment about
using be32_add_cpu, and fixes a typo in the second
version of the patch.
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>
local cifs functions (repost)
Using kernel crypto APIs for DES encryption during LM and NT hash generation
instead of local functions within cifs.
Source file smbdes.c is deleted sans four functions, one of which
uses ecb des functionality provided by kernel crypto APIs.
Remove function SMBOWFencrypt.
Add return codes to various functions such as calc_lanman_hash,
SMBencrypt, and SMBNTencrypt. Includes fix noticed by Dan Carpenter.
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
CC: Dan Carpenter <error27@gmail.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
It's possible that when we go to decode the string area in the
SESSION_SETUP response, that bytes_remaining will be 0. Decrementing it at
that point will mean that it can go "negative" and wrap. Check for a
bytes_remaining value of 0, and don't try to decode the string area if
that's the case.
Cc: stable@kernel.org
Reported-and-Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The buffer length checks in this function depend on this value being a
signed data type, but 690c522fa converted it to an unsigned type.
Also, eliminate a problem with the null termination check in the same
function. cifs_strndup_from_ucs handles that situation correctly
already, and the existing check could potentially lead to a buffer
overrun since it increments bleft without checking to see whether it
falls off the end of the buffer.
Cc: stable@kernel.org
Reported-and-Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
make modules C=2 M=fs/cifs CF=-D__CHECK_ENDIAN__
Found for example:
CHECK fs/cifs/cifssmb.c
fs/cifs/cifssmb.c:728:22: warning: incorrect type in assignment (different base types)
fs/cifs/cifssmb.c:728:22: expected unsigned short [unsigned] [usertype] Tid
fs/cifs/cifssmb.c:728:22: got restricted __le16 [usertype] <noident>
fs/cifs/cifssmb.c:1883:45: warning: incorrect type in assignment (different base types)
fs/cifs/cifssmb.c:1883:45: expected long long [signed] [usertype] fl_start
fs/cifs/cifssmb.c:1883:45: got restricted __le64 [usertype] start
fs/cifs/cifssmb.c:1884:54: warning: restricted __le64 degrades to integer
fs/cifs/cifssmb.c:1885:58: warning: restricted __le64 degrades to integer
fs/cifs/cifssmb.c:1886:43: warning: incorrect type in assignment (different base types)
fs/cifs/cifssmb.c:1886:43: expected unsigned int [unsigned] fl_pid
fs/cifs/cifssmb.c:1886:43: got restricted __le32 [usertype] pid
In checking new smb2 code for missing endian conversions, I noticed
some endian errors had crept in over the last few releases into the
cifs code (symlink, ntlmssp, posix lock, and also a less problematic warning
in fscache). A followon patch will address a few smb2 endian
problems.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
We artificially limited the user name to 32 bytes, but modern servers handle
larger. Set the maximum length to a reasonable 256, and make the user name
string dynamically allocated rather than a fixed size in session structure.
Also clean up old checkpatch warning.
Signed-off-by: Steve French <sfrench@us.ibm.com>
LANMAN response length was changed to 16 bytes instead of 24 bytes.
Revert it back to 24 bytes.
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
CC: stable@kernel.org
Signed-off-by: Steve French <sfrench@us.ibm.com>
Stefan Metzmacher