Samba, ACL and read only flag
Douglas K. Fischer
skeet at Bridgewater.EDU
Tue Dec 8 18:51:54 GMT 1998
> Date: Tue, 8 Dec 1998 11:10:44 +0100
> From: Axel Thimm <Axel.Thimm at physik.fu-berlin.de>
> To: samba at samba.org
> Subject: Samba, ACL and read only flag
> Message-ID: <19981208111044.A25533 at physik.fu-berlin.de>
>
> I have a problem with ACL, when a non owner tries to access a file, to which
> he otherwise has full access over (DEC Unix) ACLs. He can read it, but it is
> write protected (checked with smbclient). We are using samba-1.9.18p7.
>
> I browsed the archives and saw that someone had reported this in August (with
> Solaris ACLs) and mentioned a fast fix. So my question is whether this has
> been fixed, and if yes, whether a 1.9.18x version of Samba deals nicely with
> it? (We wouldn't like to switch to 2.0 beta, due to our production
> environment).
Hallo Axel,
Yes, we found a quick fix for Solaris ACLs and the read-only flag. I do
not know how well our fix would apply to DEC UNIX as I am unfamiliar with
it. Our fix makes use of the access() function in Solaris. To the best of
our knowledge (we use them extensively and have not had a single problem
with them once this fix was implemented), Solaris ACLs appear to work
fully under Samba with the mear exception of the dos_mode() function in
server.c. This function is responsible for the mapping between UNIX and
DOS permissions on a file.
I have included the diff patch for our fix below (taken against
1.9.18p10), as well as the man page for access() in Solaris. In order for
such a fix to work for you, you will need to find the same or a similar
function in DUNIX that will perform like access().
The same goes for anyone else wanting to use this type of ACL fix on any
other platform than Solaris (2.5 or greater, SPARC and x86). This fix will
likely NOT work for you as-is: you will need to make some OS-specific
changes.
[ Then again, maybe every UNIX has an access() function that works like
the one in Solaris... :-) ]
BTW, changes between the 1.9.18 series and 2.0 make the above fix
obsolete, i.e. the read-only ACL problem should not exist in 2.0. Unless
you really don't want to move forward to 2.0, upgrading's the best bet.
Cheers
Douglas
----------------------------------------------------------------------
Douglas K. Fischer DFischer at Bridgewater.EDU (540) 828 - 5343
Network Systems Engineer C. E. Shull Information Technology Center
College Box 36 Bridgewater College Bridgewater, VA 22812
----------------------------------------------------------------------
===== cut here for diff patch =====
*** server.orig Wed Aug 19 19:41:23 1998
--- server.c Mon Nov 2 09:41:40 1998
***************
*** 197,202 ****
--- 197,203 ----
if (!((sbuf->st_mode & S_IWOTH) ||
Connections[cnum].admin_user ||
((sbuf->st_mode & S_IWUSR) && current_user.uid==sbuf->st_uid) ||
+ (access(path,W_OK) == 0) ||
((sbuf->st_mode & S_IWGRP) &&
in_group(sbuf->st_gid,current_user.gid,
current_user.ngroups,current_user.igroups))))
===== cut here for diff patch =====
===== cut here for Solaris 2.6 access() man page =====
System Calls access(2)
NAME
access - determine accessibility of a file
SYNOPSIS
#include <unistd.h>
int access(const char *path, int amode);
DESCRIPTION
The access() function checks the file named by the pathname
pointed to by the path argument for accessibility according
to the bit pattern contained in amode, using the real user
ID in place of the effective user ID and the real group ID
in place of the effective group ID. This allows a setuid
process to verify that the user running it would have had
permission to access this file.
The value of amode is either the bitwise inclusive OR of the
access permissions to be checked (R_OK, W_OK, X_OK) or the
existence test, F_OK.
These constants are defined in <unistd.h> as follows:
R_OK Test for read permission.
W_OK Test for write permission.
X_OK Test for execute or search permission.
F_OK Check existence of file
See intro(2) for additional information about "File Access
Permission".
If any access permissions are to be checked, each will be
checked individually, as described in intro(2). If the pro-
cess has appropriate privileges, an implementation may indi-
cate success for X_OK even if none of the execute file per-
mission bits are set.
RETURN VALUES
If the requested access is permitted, access() succeeds and
returns 0. Otherwise, -1 is returned and errno is set to
indicate the error.
ERRORS
The access() function will fail if:
EACCES Permission bits of the file mode do not per-
mit the requested access, or search permis-
sion is denied on a component of the path
prefix.
SunOS 5.6 Last change: 28 Dec 1996 1
System Calls access(2)
EFAULT path points to an illegal address.
EINTR A signal was caught during the access() func-
tion.
ELOOP Too many symbolic links were encountered in
resolving path.
EMULTIHOP Components of path require hopping to multi-
ple remote machines.
ENAMETOOLONG The length of the path argument exceeds
PATH_MAX, or a pathname component is longer
than NAME_MAX while {_POSIX_NO_TRUNC} is in
effect.
ENOENT A component of path does not name an existing
file or path is an empty string.
ENOLINK path points to a remote machine and the link
to that machine is no longer active.
ENOTDIR A component of the path prefix is not a
directory.
EROFS Write access is requested for a file on a
read-only file system.
The access() function may fail if:
EINVAL The value of the amode argument is invalid.
ENAMETOOLONG Pathname resolution of a symbolic link pro-
duced an intermediate result whose length
exceeds PATH_MAX.
ETXTBSY Write access is requested for a pure pro-
cedure (shared text) file that is being exe-
cuted.
USAGE
Additional values of amode other than the set defined in the
description may be valid, for example, if a system has
extended access controls.
SunOS 5.6 Last change: 28 Dec 1996 2
System Calls access(2)
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________
| ATTRIBUTE TYPE| ATTRIBUTE VALUE |
|____________________________________
| MT-Level | Async-Signal-Safe|
|_______________|___________________|
SEE ALSO
intro(2), chmod(2), stat(2), attributes(5)
SunOS 5.6 Last change: 28 Dec 1996 3
===== cut here for Solaris 2.6 access() man page =====
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