[Pkg-samba-maint] Bug#814287: Recent security fix for symlinks renders root filesystem exports unusable
Petr Vandrovec
petr at vmware.com
Tue Feb 9 22:27:54 UTC 2016
Package: samba
Version: 2:4.3.3+dfsg-1+b1
Severity: important
Since I updated samba package to latest version, I cannot access my exports:
==
> net use w: \\petr-dev3\rootfs\bhavesh\home\petr <password> /user:petr
System error 5 has occurred.
Access is denied.
==
It seems to me that there is a thinko in how export of '/' directory is
handled, ending up with:
check_reduced_name: Bad access attempt: bhavesh/home/petr is a symlink
outside the share path
conn_rootdir =/
resolved_name=/bhavesh/home/petr
despite there being no symlinks involved, and /bhavesh/home/petr being
inside / space.
For now I've worked around the problem by setting
follow symlinks = yes
wide links = yes
allow insecure wide links = yes
but I do not think I should be forced to enable 'follow symlinks' to use
symlink-less share.
Petr
-------------- next part --------------
[2016/02/09 13:11:33.139038, 5, pid=17936, effective(0, 0), real(0, 0)] ../source3/auth/token_util.c:639(debug_unix_user_token)
UNIX token of user 884
Primary group is 201 and contains 20 supplementary groups
Group[ 0]: 201
Group[ 1]: 0
Group[ 2]: 4
Group[ 3]: 5
Group[ 4]: 6
Group[ 5]: 7
Group[ 6]: 15
Group[ 7]: 20
Group[ 8]: 24
Group[ 9]: 25
Group[ 10]: 26
Group[ 11]: 27
Group[ 12]: 29
Group[ 13]: 44
Group[ 14]: 46
Group[ 15]: 50
Group[ 16]: 118
Group[ 17]: 1010
Group[ 18]: 1031
Group[ 19]: 104310
[2016/02/09 13:11:33.139074, 5, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/uid.c:363(change_to_user_internal)
Impersonated user: uid=(884,884), gid=(0,201)
[2016/02/09 13:11:33.139081, 4, pid=17936, effective(884, 201), real(884, 0), class=vfs] ../source3/smbd/vfs.c:844(vfs_ChDir)
vfs_ChDir to /
[2016/02/09 13:11:33.139093, 4, pid=17936, effective(884, 201), real(884, 0), class=vfs] ../source3/smbd/vfs.c:855(vfs_ChDir)
vfs_ChDir got /
[2016/02/09 13:11:33.139102, 10, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/smb2_create.c:501(smbd_smb2_create_send)
smbd_smb2_create: name[bhavesh\home\petr]
[2016/02/09 13:11:33.139110, 10, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/smb2_create.c:932(smbd_smb2_create_send)
smbd_smb2_create_send: open execution phase
[2016/02/09 13:11:33.139121, 5, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/filename.c:257(unix_convert)
unix_convert called on file "bhavesh/home/petr"
[2016/02/09 13:11:33.139129, 10, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/statcache.c:244(stat_cache_lookup)
stat_cache_lookup: lookup failed for name [BHAVESH/HOME/PETR]
[2016/02/09 13:11:33.139136, 10, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/statcache.c:244(stat_cache_lookup)
stat_cache_lookup: lookup failed for name [BHAVESH/HOME]
[2016/02/09 13:11:33.139141, 10, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/statcache.c:244(stat_cache_lookup)
stat_cache_lookup: lookup failed for name [BHAVESH]
[2016/02/09 13:11:33.139148, 5, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/filename.c:449(unix_convert)
unix_convert begin: name = bhavesh/home/petr, dirpath = , start = bhavesh/home/petr
[2016/02/09 13:11:33.139158, 5, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/statcache.c:143(stat_cache_add)
stat_cache_add: Added entry (56549fbbc990:size 11) BHAVESH/HOME/PETR -> bhavesh/home/petr
[2016/02/09 13:11:33.139164, 5, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/filename.c:472(unix_convert)
conversion of base_name finished bhavesh/home/petr -> bhavesh/home/petr
[2016/02/09 13:11:33.139171, 10, pid=17936, effective(884, 201), real(884, 0), class=vfs] ../source3/smbd/vfs.c:1147(check_reduced_name)
check_reduced_name [bhavesh/home/petr] [/]
[2016/02/09 13:11:33.139182, 10, pid=17936, effective(884, 201), real(884, 0), class=vfs] ../source3/smbd/vfs.c:1207(check_reduced_name)
check_reduced_name realpath [bhavesh/home/petr] -> [/bhavesh/home/petr]
[2016/02/09 13:11:33.139189, 2, pid=17936, effective(884, 201), real(884, 0), class=vfs] ../source3/smbd/vfs.c:1240(check_reduced_name)
check_reduced_name: Bad access attempt: bhavesh/home/petr is a symlink outside the share path
conn_rootdir =/
resolved_name=/bhavesh/home/petr
[2016/02/09 13:11:33.139198, 5, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/filename.c:1078(check_name)
check_name: name bhavesh/home/petr failed with NT_STATUS_ACCESS_DENIED
[2016/02/09 13:11:33.139204, 3, pid=17936, effective(884, 201), real(884, 0)] ../source3/smbd/filename.c:1431(filename_convert_internal)
filename_convert_internal: check_name failed for name bhavesh/home/petr with NT_STATUS_ACCESS_DENIED
petr-dev3:/bhavesh/home/petr/debian/samba-4.3.3+dfsg$ ls -lad /
drwxr-xr-x 84 root root 4096 Aug 10 2015 /
petr-dev3:/bhavesh/home/petr/debian/samba-4.3.3+dfsg$ ls -lad /bhavesh
drwxr-xr-x 13 root root 4096 Jan 6 2014 /bhavesh
petr-dev3:/bhavesh/home/petr/debian/samba-4.3.3+dfsg$ ls -lad /bhavesh/home
drwxr-sr-x 3 petr mts 4096 Dec 7 12:15 /bhavesh/home
petr-dev3:/bhavesh/home/petr/debian/samba-4.3.3+dfsg$ ls -lad /bhavesh/home/petr
drwxr-sr-x 86 petr mts 12288 Feb 1 22:41 /bhavesh/home/petr
-------------- next part --------------
#
# Sample configuration file for the Samba suite for Debian GNU/Linux.
#
#
# This is the main Samba configuration file. You should read the
# smb.conf(5) manual page in order to understand the options listed
# here. Samba has a huge number of configurable options most of which
# are not shown in this example
#
# Any line which starts with a ; (semi-colon) or a # (hash)
# is a comment and is ignored. In this example we will use a #
# for commentary and a ; for parts of the config file that you
# may wish to enable
#
# NOTE: Whenever you modify this file you should run the command
# "testparm" to check that you have not made any basic syntactic
# errors.
#
#======================= Global Settings =======================
[global]
## Browsing/Identification ###
# Change this to the workgroup/NT-domain name your Samba server will part of
workgroup = WORKGROUP
# server string is the equivalent of the NT Description field
server string = %h server (Samba %v)
# Windows Internet Name Serving Support Section:
# WINS Support - Tells the NMBD component of Samba to enable its WINS Server
; wins support = no
# WINS Server - Tells the NMBD components of Samba to be a WINS Client
# Note: Samba can be either a WINS Server, or a WINS Client, but NOT both
; wins server = w.x.y.z
# If we receive WINS server info from DHCP, override the options above.
include = /etc/samba/dhcp.conf
# This will prevent nmbd to search for NetBIOS names through DNS.
dns proxy = no
# What naming service and in what order should we use to resolve host names
# to IP addresses
; name resolve order = lmhosts host wins bcast
#### Networking ####
# The specific set of interfaces / networks to bind to
# This can be either the interface name or an IP address/netmask;
# interface names are normally preferred
; interfaces = 127.0.0.0/8 eth0
# Only bind to the named interfaces and/or networks; you must use the
# 'interfaces' option above to use this.
# It is recommended that you enable this feature if your Samba machine is
# not protected by a firewall or is a firewall itself. However, this
# option cannot handle dynamic or non-broadcast interfaces correctly.
; bind interfaces only = true
#### Debugging/Accounting ####
# This tells Samba to use a separate log file for each machine
# that connects
log file = /var/log/samba/log.%m
log level = 99
# Put a capping on the size of the log files (in Kb).
max log size = 1000
# If you want Samba to only log through syslog then set the following
# parameter to 'yes'.
; syslog only = no
# We want Samba to log a minimum amount of information to syslog. Everything
# should go to /var/log/samba/log.{smbd,nmbd} instead. If you want to log
# through syslog you should set the following parameter to something higher.
syslog = 0
# Do something sensible when Samba crashes: mail the admin a backtrace
panic action = /bin/sleep 1
####### Authentication #######
# "security = user" is always a good idea. This will require a Unix account
# in this server for every user accessing the server. See
# /usr/share/doc/samba-doc/htmldocs/Samba-HOWTO-Collection/ServerType.html
# in the samba-doc package for details.
; security = user
# You may wish to use password encryption. See the section on
# 'encrypt passwords' in the smb.conf(5) manpage before enabling.
encrypt passwords = true
# If you are using encrypted passwords, Samba will need to know what
# password database type you are using.
passdb backend = tdbsam
obey pam restrictions = no
; guest account = nobody
invalid users =
# This boolean parameter controls whether Samba attempts to sync the Unix
# password with the SMB password when the encrypted SMB password in the
# passdb is changed.
; unix password sync = no
# For Unix password sync to work on a Debian GNU/Linux system, the following
# parameters must be set (thanks to Ian Kahan <<kahan at informatik.tu-muenchen.de> for
# sending the correct chat script for the passwd program in Debian Sarge).
passwd program = /usr/bin/passwd %u
passwd chat = *Enter\snew\sUNIX\spassword:* %n\n *Retype\snew\sUNIX\spassword:* %n\n *password\supdated\ssuccessfully* .
# This boolean controls whether PAM will be used for password changes
# when requested by an SMB client instead of the program listed in
# 'passwd program'. The default is 'no'.
; pam password change = no
client plaintext auth = yes
client use plaintext auth = yes
########## Domains ###########
# Is this machine able to authenticate users. Both PDC and BDC
# must have this setting enabled. If you are the BDC you must
# change the 'domain master' setting to no
#
; domain logons = yes
#
# The following setting only takes effect if 'domain logons' is set
# It specifies the location of the user's profile directory
# from the client point of view)
# The following required a [profiles] share to be setup on the
# samba server (see below)
; logon path = \\%N\profiles\%U
# Another common choice is storing the profile in the user's home directory
; logon path = \\%N\%U\profile
# The following setting only takes effect if 'domain logons' is set
# It specifies the location of a user's home directory (from the client
# point of view)
; logon drive = H:
; logon home = \\%N\%U
# The following setting only takes effect if 'domain logons' is set
# It specifies the script to run during logon. The script must be stored
# in the [netlogon] share
# NOTE: Must be store in 'DOS' file format convention
; logon script = logon.cmd
# This allows Unix users to be created on the domain controller via the SAMR
# RPC pipe. The example command creates a user account with a disabled Unix
# password; please adapt to your needs
; add user script = /usr/sbin/adduser --quiet --disabled-password --gecos "" %u
########## Printing ##########
# If you want to automatically load your printer list rather
# than setting them up individually then you'll need this
; load printers = yes
# lpr(ng) printing. You may wish to override the location of the
# printcap file
; printing = bsd
; printcap name = /etc/printcap
# CUPS printing. See also the cupsaddsmb(8) manpage in the
# cupsys-client package.
; printing = cups
; printcap name = cups
# When using [print$], root is implicitly a 'printer admin', but you can
# also give this right to other users to add drivers and set printer
# properties
; printer admin = @ntadmin
############ Misc ############
# Using the following line enables you to customise your configuration
# on a per machine basis. The %m gets replaced with the netbios name
# of the machine that is connecting
; include = /home/samba/etc/smb.conf.%m
# Most people will find that this option gives better performance.
# See smb.conf(5) and /usr/share/doc/samba-doc/htmldocs/speed.html
# for details
# You may want to add the following on a Linux system:
# SO_RCVBUF=8192 SO_SNDBUF=8192
socket options = TCP_NODELAY
# The following parameter is useful only if you have the linpopup package
# installed. The samba maintainer and the linpopup maintainer are
# working to ease installation and configuration of linpopup and samba.
; message command = /bin/sh -c '/usr/bin/linpopup "%f" "%m" %s; rm %s' &
# Domain Master specifies Samba to be the Domain Master Browser. If this
# machine will be configured as a BDC (a secondary logon server), you
# must set this to 'no'; otherwise, the default behavior is recommended.
; domain master = auto
# Some defaults for winbind (make sure you're not using the ranges
# for something else.)
; idmap uid = 10000-20000
; idmap gid = 10000-20000
; template shell = /bin/bash
#======================= Share Definitions =======================
acl allow execute always = True
[homes]
comment = Home Directories
browseable = no
# By default, the home directories are exported read-only. Change next
# parameter to 'yes' if you want to be able to write to them.
writable = yes
# File creation mask is set to 0700 for security reasons. If you want to
# create files with group=rw permissions, set next parameter to 0775.
create mask = 0775
# Directory creation mask is set to 0700 for security reasons. If you want to
# create dirs. with group=rw permissions, set next parameter to 0775.
directory mask = 0775
# Un-comment the following and create the netlogon directory for Domain Logons
# (you need to configure Samba to act as a domain controller too.)
;[netlogon]
; comment = Network Logon Service
; path = /home/samba/netlogon
; guest ok = yes
; writable = no
; share modes = no
# Un-comment the following and create the profiles directory to store
# users profiles (see the "logon path" option above)
# (you need to configure Samba to act as a domain controller too.)
# The path below should be writable by all users so that their
# profile directory may be created the first time they log on
;[profiles]
; comment = Users profiles
; path = /home/samba/profiles
; guest ok = no
; browseable = no
; create mask = 0600
; directory mask = 0700
[printers]
comment = All Printers
browseable = no
path = /var/spool/samba
printable = yes
public = no
writable = no
create mode = 0700
# Windows clients look for this share name as a source of downloadable
# printer drivers
[print$]
comment = Printer Drivers
path = /var/lib/samba/printers
browseable = yes
read only = yes
guest ok = no
# Uncomment to allow remote administration of Windows print drivers.
# Replace 'ntadmin' with the name of the group your admin users are
# members of.
; write list = root, @ntadmin
# A sample share for sharing your CD-ROM with others.
;[cdrom]
; comment = Samba server's CD-ROM
; writable = no
; locking = no
; path = /cdrom
; public = yes
[rootfs]
comment = Root FS
writeable = yes
locking = yes
path = /
# The next two parameters show how to auto-mount a CD-ROM when the
# cdrom share is accesed. For this to work /etc/fstab must contain
# an entry like this:
#
# /dev/scd0 /cdrom iso9660 defaults,noauto,ro,user 0 0
#
# The CD-ROM gets unmounted automatically after the connection to the
#
# If you don't want to use auto-mounting/unmounting make sure the CD
# is mounted on /cdrom
#
; preexec = /bin/mount /cdrom
; postexec = /bin/umount /cdrom
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