samba - May 2017 - Windows 10 spawning thousands of child processes on Samba 4.3.11 server

On Mon, May 22, 2017 at 11:32 PM, Rowland Penny <rpenny at samba.org>
wrote:
> On Mon, 22 May 2017 23:22:32 +0200
> Asbjorn Taugbol via samba <samba at lists.samba.org> wrote:
>
> > I have 10 Windows 10 clients connecting to Ubuntu 16.04 with Samba
> > version 4.3.11-Ubuntu. Each client has one smbd process, but I notice
> > the number of child processes is exploding into 40.000+ the next day
> > after a restart. I reckon this is not normal. Server load is < 0.1
> > but client applications are misbehaving and crashing.
> >
> > The problems started when moving from an old Ubuntu 10.04 to a newer
> > 16.04.
> >
>
> Can you post your smb.conf.
>
> Rowland
>
#
# 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
#
# Some options that are often worth tuning have been included as
# commented-out examples in this file.
#  - When such options are commented with ";", the proposed setting
#    differs from the default Samba behaviour
#  - When commented with "#", the proposed setting is the default
#    behaviour of Samba but the option is considered important
#    enough to be mentioned here
#
# 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, Ubuntu)

# 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

# This will prevent nmbd to search for NetBIOS names through DNS.
   dns proxy = no

#### 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 = yes


# AT 20170521
deadtime = 90

#### Debugging/Accounting ####

# This tells Samba to use a separate log file for each machine
# that connects
   log file = /var/log/samba/log.%m

# Cap the size of the individual log files (in KiB).
   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 = /usr/share/samba/panic-action %d


####### Authentication #######

# Server role. Defines in which mode Samba will operate. Possible
# values are "standalone server", "member server",
"classic primary
# domain controller", "classic backup domain controller",
"active
# directory domain controller".
#
# Most people will want "standalone sever" or "member
server".
# Running as "active directory domain controller" will require first
# running "samba-tool domain provision" to wipe databases and create a
# new domain.
   server role = standalone server

# If you are using encrypted passwords, Samba will need to know what
# password database type you are using.
   passdb backend = tdbsam

   obey pam restrictions = yes

# 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 = yes

# 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\s*\spassword:* %n\n
*Retype\snew\s*\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 = yes

# This option controls how unsuccessful authentication attempts are mapped
# to anonymous connections
   map to guest = bad user

########## Domains ###########

#
# The following settings only takes effect if 'server role = primary
# classic domain controller', 'server role = backup domain
controller'
# or '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
# (this is Samba's default)
#   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

# This allows machine accounts to be created on the domain controller via
the
# SAMR RPC pipe.
# The following assumes a "machines" group exists on the system
; add machine script  = /usr/sbin/useradd -g machines -c "%u machine
account" -d /var/lib/samba -s /bin/false %u

# This allows Unix groups to be created on the domain controller via the
SAMR
# RPC pipe.
; add group script = /usr/sbin/addgroup --force-badname %g

############ 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

# 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

# Setup usershare options to enable non-root users to share folders
# with the net usershare command.

# Maximum number of usershare. 0 (default) means that usershare is disabled.
;   usershare max shares = 100

# Allow users who've been granted usershare privileges to create
# public shares, not just authenticated ones
   usershare allow guests = yes

#======================= Share Definitions ======================
# Un-comment the following (and tweak the other settings below to suit)
# to enable the default home directory shares. This will share each
# user's home directory as \\server\username
;[homes]
;   comment = Home Directories
;   browseable = no

# By default, the home directories are exported read-only. Change the
# next parameter to 'no' if you want to be able to write to them.
;   read only = 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 = 0700

# 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 = 0700

# By default, \\server\username shares can be connected to by anyone
# with access to the samba server.
# Un-comment the following parameter to make sure that only "username"
# can connect to \\server\username
# This might need tweaking when using external authentication schemes
;   valid users = %S

# 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
;   read only = yes

# 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


[administration]
        comment = Administration directory
        path = /home/administration
        write list = @administration, at production
        read only = No
        #oplocks = No
        create mask = 0774
        directory mask = 0775
        hide dot files = yes

[production]
        comment = Production directory
        path = /home/production
        invalid users = administration
        write list = @production
        read only = No
        veto oplock files = /*.wbt/*.spc?/


[printers]
   comment = All Printers
   browseable = no
   path = /var/spool/samba
   printable = yes
   guest ok = no
   read only = yes
   create mask = 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.
# You may need to replace 'lpadmin' with the name of the group your
# admin users are members of.
# Please note that you also need to set appropriate Unix permissions
# to the drivers directory for these users to have write rights in it
;   write list = root, @lpadmin

On Mon, 22 May 2017 23:39:26 +0200
Asbjorn Taugbol <asbjornt at gmail.com> wrote:

OK, this is your actual smb.conf:

[global]
   workgroup = WORKGROUP
   server string = %h server (Samba, Ubuntu)
   dns proxy = no
   deadtime = 90
   log file = /var/log/samba/log.%m
   max log size = 1000
   syslog = 0
   panic action = /usr/share/samba/panic-action %d
   server role = standalone server
   obey pam restrictions = yes
   unix password sync = yes
   passwd program = /usr/bin/passwd %u
   passwd chat = *Enter\snew\s*\spassword:* %n\n*Retype\snew\s*\spassword:* %n\n
*password\supdated\ssuccessfully* .
   pam password change = yes
   map to guest = bad user
   usershare allow guests = yes

[administration]
        comment = Administration directory
        path = /home/administration
        write list = @administration, at production
        read only = No
        create mask = 0774
        directory mask = 0775
        hide dot files = yes

[production]
        comment = Production directory
        path = /home/production
        invalid users = administration
        write list = @production
        read only = No
        veto oplock files = /*.wbt/*.spc?/


[printers]
   comment = All Printers
   browseable = no
   path = /var/spool/samba
   printable = yes
   guest ok = no
   read only = yes
   create mask = 0700

[print$]
   comment = Printer Drivers
   path = /var/lib/samba/printers
   browseable = yes
   read only = yes
   guest ok = no

There doesn't seem to be anything wrong there, but you could try
turning off guest access by commenting this line:

map to guest = bad user

Rowland

Did you TV/Radio broke??  ;-) 

This really smells like some malware/cryptoware. 
Seen this ones on a network, and that was a cypto trying to write to shares. 
And they to that really really fast. 

Increast the samba debug logs and track if this is client related. 
That where i would start. 


Greetz, 

Louis


> -----Oorspronkelijk bericht-----
> Van: samba [mailto:samba-bounces at lists.samba.org] Namens 
> Rowland Penny via samba
> Verzonden: dinsdag 23 mei 2017 7:57
> Aan: samba at lists.samba.org
> Onderwerp: Re: [Samba] Windows 10 spawning thousands of child 
> processes on Samba 4.3.11 server
> 
> On Mon, 22 May 2017 23:39:26 +0200
> Asbjorn Taugbol <asbjornt at gmail.com> wrote:
> 
> OK, this is your actual smb.conf:
> 
> [global]
>    workgroup = WORKGROUP
>    server string = %h server (Samba, Ubuntu)
>    dns proxy = no
>    deadtime = 90
>    log file = /var/log/samba/log.%m
>    max log size = 1000
>    syslog = 0
>    panic action = /usr/share/samba/panic-action %d
>    server role = standalone server
>    obey pam restrictions = yes
>    unix password sync = yes
>    passwd program = /usr/bin/passwd %u
>    passwd chat = *Enter\snew\s*\spassword:* 
> %n\n*Retype\snew\s*\spassword:* %n\n 
> *password\supdated\ssuccessfully* .
>    pam password change = yes
>    map to guest = bad user
>    usershare allow guests = yes
> 
> [administration]
>         comment = Administration directory
>         path = /home/administration
>         write list = @administration, at production
>         read only = No
>         create mask = 0774
>         directory mask = 0775
>         hide dot files = yes
> 
> [production]
>         comment = Production directory
>         path = /home/production
>         invalid users = administration
>         write list = @production
>         read only = No
>         veto oplock files = /*.wbt/*.spc?/
> 
> 
> [printers]
>    comment = All Printers
>    browseable = no
>    path = /var/spool/samba
>    printable = yes
>    guest ok = no
>    read only = yes
>    create mask = 0700
> 
> [print$]
>    comment = Printer Drivers
>    path = /var/lib/samba/printers
>    browseable = yes
>    read only = yes
>    guest ok = no
> 
> There doesn't seem to be anything wrong there, but you could 
> try turning off guest access by commenting this line:
> 
> map to guest = bad user
> 
> Rowland
> 
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> 
>

On Tue, 23 May 2017 08:44:42 +0200
"L.P.H. van Belle via samba" <samba at lists.samba.org> wrote:
> Did you TV/Radio broke??  ;-) 
> 
> This really smells like some malware/cryptoware. 
> Seen this ones on a network, and that was a cypto trying to write to
> shares. And they to that really really fast. 
> 
> Increast the samba debug logs and track if this is client related. 
> That where i would start. 
> 
They were my thoughts, the connections are from guest by the look of
them and removing 'map to guest = Bad User' would reset it to 'map
to
guest = Never' and the connections would be dropped.

I think the OP needs to start looking at their clients ;-)

Rowland