Twórcy SuSE Linuksa znaleźli błąd we wszystkich wersjach Samby od 2.0.x do 2.2.7a włącznie. Dzięki niemu dowolna osoba może zmusić smbd do wykonania podstawionego kawałka kodu, a przez to uzyskać prawa administratora na atakowanej maszynie.
Nowa wersja, którą można skopiować ze stron projektu, nie ma już tego błędu. Jednak mimo wszystko zalecane jest zamknięcie nieznanym hostom dostępu do portów 139 i 445.
Date: Sat, 15 Mar 2003 08:13:20 -0600 (CST) From: "Gerald (Jerry) Carter"
To: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: [SECURITY] Samba 2.2.8 available for download -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 This release provides an important security fix outlined in the release notes that follow. This is the latest stable release of Samba and the version that all production Samba servers should be running for all current bug-fixes. The source code can be downloaded from : http://download.samba.org/samba/ftp/ in the file samba-2.2.8.tar.gz or samba-2.2.8.tar.bz2. The uncompressed tarball has been signed using the Samba Distribution Key (available in the same directory). Binary packages will be released shortly for major platforms and can be found at http://download.samba.org/samba/ftp/Binary_Packages/ As always, all bugs are our responsibility. --Sincerely The Samba Team **************************************** * IMPORTANT: Security bugfix for Samba * **************************************** Summary - ------- The SuSE security audit team, in particular Sebastian Krahmer , has found a flaw in the Samba main smbd code which could allow an external attacker to remotely and anonymously gain Super User (root) privileges on a server running a Samba server. This flaw exists in previous versions of Samba from 2.0.x to 2.2.7a inclusive. This is a serious problem and all sites should either upgrade to Samba 2.2.8 immediately or prohibit access to TCP ports 139 and 445. Advice created by Andrew Tridgell, the leader of the Samba Team, on how to protect an unpatched Samba server is given at the end of this section. The SMB/CIFS protocol implemented by Samba is vulnerable to many attacks, even without specific security holes. The TCP ports 139 and the new port 445 (used by Win2k and the Samba 3.0 alpha code in particular) should never be exposed to untrusted networks. Description - ----------- A buffer overrun condition exists in the SMB/CIFS packet fragment re-assembly code in smbd which would allow an attacker to cause smbd to overwrite arbitrary areas of memory in its own process address space. This could allow a skilled attacker to inject binary specific exploit code into smbd. This version of Samba adds explicit overrun and overflow checks on fragment re-assembly of SMB/CIFS packets to ensure that only valid re-assembly is performed by smbd. In addition, the same checks have been added to the re-assembly functions in the client code, making it safe for use in other services. Credit - ------ This security flaw was discovered and reported to the Samba Team by Sebastian Krahmer of the SuSE Security Audit Team. The fix was prepared by Jeremy Allison and reviewed by engineers from the Samba Team, SuSE, HP, SGI, Apple, and the Linux vendor engineers on the Linux Vendor security mailing list. The Samba Team would like to thank SuSE and Sebastian Krahmer for their excellent auditing work and for drawing attention to this flaw. Patch Availability - ----------------- As this is a security issue, patches for this flaw specific to earlier versions of Samba will be posted on the email@example.com mailing list as requested. ************************************ Protecting an unpatched Samba server ************************************ Samba Team, March 2003 This is a note on how to provide your Samba server some protection against the recently discovered remote security hole if you are unable to upgrade to the fixed version immediately. Even if you do upgrade you might like to think about the suggestions in this note to provide you with additional levels of protection. Using host based protection --------------------------- In many installations of Samba the greatest threat comes for outside your immediate network. By default Samba will accept connections from any host, which means that if you run an insecure version of Samba on a host that is directly connected to the Internet you can be especially vulnerable. One of the simplest fixes in this case is to use the 'hosts allow' and 'hosts deny' options in the Samba smb.conf configuration file to only allow access to your server from a specific range of hosts. An example might be: hosts allow = 127.0.0.1 192.168.2.0/24 192.168.3.0/24 hosts deny = 0.0.0.0/0 The above will only allow SMB connections from 'localhost' (your own computer) and from the two private networks 192.168.2 and 192.168.3. All other connections will be refused connections as soon as the client sends its first packet. The refusal will be marked as a 'not listening on called name' error. Using interface protection -------------------------- By default Samba will accept connections on any network interface that it finds on your system. That means if you have a ISDN line or a PPP connection to the Internet then Samba will accept connections on those links. This may not be what you want. You can change this behavior using options like the following: interfaces = eth* lo bind interfaces only = yes that tells Samba to only listen for connections on interfaces with a name starting with 'eth' such as eth0, eth1, plus on the loopback interface called 'lo'. The name you will need to use depends on what OS you are using. In the above I used the common name for ethernet adapters on Linux. If you use the above and someone tries to make a SMB connection to your host over a PPP interface called 'ppp0', they will get a TCP connection refused reply. In that case no Samba code is run at all as the operating system has been told not to pass connections from that interface to any process. Using a firewall ---------------- Many people use a firewall to deny access to services that they don't want exposed outside their network. This can be a very good idea, although I would recommend using it in conjunction with the above methods so that you are protected even if your firewall is not active for some reason. If you are setting up a firewall then you need to know what TCP and UDP ports to allow and block. Samba uses the following: UDP/137 - used by nmbd UDP/138 - used by nmbd TCP/139 - used by smbd TCP/445 - used by smbd The last one is important as many older firewall setups may not be aware of it, given that this port was only added to the protocol in recent years. Using a IPC$ share deny ----------------------- If the above methods are not suitable, then you could also place a more specific deny on the IPC$ share that is used in the recently discovered security hole. This allows you to offer access to other shares while denying access to IPC$ from potentially untrustworthy hosts. To do that you could use: [ipc$] hosts allow = 192.168.115.0/24 127.0.0.1 hosts deny = 0.0.0.0/0 this would tell Samba that IPC$ connections are not allowed from anywhere but the two listed places (localhost and a local subnet). Connections to other shares would still be allowed. As the IPC$ share is the only share that is always accessible anonymously this provides some level of protection against attackers that do not know a username/password for your host. If you use this method then clients will be given a 'access denied' reply when they try to access the IPC$ share. That means that those clients will not be able to browse shares, and may also be unable to access some other resources. I don't recommend this method unless you cannot use one of the other methods listed above for some reason. Upgrading Samba --------------- Of course the best solution is to upgrade Samba to a version where the bug has been fixed. If you wish to also use one of the additional measures above then that would certainly be a good idea. Please check regularly on http://www.samba.org/ for updates and important announcements. **************************************** **************************************** - ----------------------------------------------------------------- Changes since 2.2.7a - -------------------- New Parameters * acl compatibility Additional Changes: See the cvs log for SAMBA_2_2 for more details 1) smbumount lazy patch from Mandrake 2) Check for too many processes *before* the fork. 3) make sure we don't run over the end of 'name' in unix_convert() 4) set umask to 0 before creating socket directory. 5) Fix the LARGE_SMB_OFF_T problems and allow smbd to do the right thing in interactive mode when a log file dir is also specified. 6) Fix delete on close semantics to match W2K. 7) Correctly return access denied on share mode deny when we can't open the file. 8) Always use safe_strcpy not pstrcpy for malloc()'d strings 9) Fixes for HP-UX only having limited POSIX lock range 10) Added uid/gid caching code. Reduces load on winbindd. 11) Removed extra copy of server name in the printername field (it was mangling the the name to be \server\serverprinter 12) Fix dumb perror used without errno being set. 13) Do retries correctly if the connection to the DC has failed. 14) Correctly check for inet_addr fail. 15) Ensure we use getgrnam() unless BROKEN_GETGRNAM is defined. 16) Fix for missing if (setting_acls) on default perms. 17) Fix to cache the sidtype 18) fix printer settings on Solaris (big-endian) print servers. ASCII -> UNICODE conversion bug. 19) Small fix check correct error return. 20) Ensure space_avail is unsigned. 21) patch to check for a valid [f]chmod_acl function pointer before calling it. Fixes seg fault in audit VFS module 22) When checking is_locked() new WRITE locks conflict with existing READ locks even if the context is the same. 23) Merge off-by-one crash fixes from HEAD 24) Move off-by-one buggy malloc()/safe_strcpy() combination to strdup() instead. 25) Merge from HEAD. Use pstrcpy not safe_strcpy. 26) Fix to allow blocking lock notification to be done rapidly (no wait for smb -> smb lock release). Adds new PENDING_LOCK type to lockdb (does not interfere with existing locks). 27) Doxygen cleanups for code documentation 28) limit the unix domain sockets used by winbindd by adding a "last_access" field to winbindd connections, and will close the oldest idle connection once the number of open connections goes over WINBINDD_MAX_SIMULTANEOUS_CLIENTS (defined in local.h as 200 currently) 29) Fix a couple of string handling errors in smbd/dir.c that would cause smbd to crash 30) Fix seg fault in smbpasswd when specifying the new password as a command line argument 31) Correct 64-but file sizes issues with smbtar and smbclient 32) Add batch mode option to pdbedit 33) Add protection in nmbd against malformed reply packets 34) Fix bug with sendfile profiling support in smbstatus output 35) Correct bug in "hide unreadable" smb.conf parameter that resulted in incorrect directory listings 36) Fix bug in group enumeration in winbindd 37) Correct build issues with libsmbclient on Solaris 38) Fix memory leak and bad pointer dereference in password changing code in smbd 39) Fix for changing attributes on a file truncate 40) Ensure smbd process count never gets to -1 if limiting number of processes 41) Ensure we return disk full by default on short writes 42) Don't delete jobs submitted after the lpq time 43) Fix reference count bug where smbds would not terminate with no open resources 44) Performance fix when using quota support on HP-UX 45) Fixes for --with-ldapsam * Default to port 389 when "ldap ssl != on" * add support for rebinding to the master directory server for password changes when "ldap server" points to a read-only slave 46) Add -W and -X command line flags to smbpasswd for extracting and setting the machine/domain SID in secrets.tdb. See the smbpasswd(8) man page for details. 47) Added (c) Luke Howard to winbind_nss_solaris.c for coded obtained from PADL's nss_ldap library. 48) Fix bug in samr_dispinfo query in winbindd 49) Fix segfault in NTLMSSP password changing code for guest connections 50) Correct pstring/fstring mismatches 51) Send level II oplock break requests synchronously to prevent condition where one smbd would continually lock a share entry in locking.tdb 52) Miscellaneous cleanups for tdb error conditions and appending data in a record 53) Implement correct open file truncate semantics with DOS attributes 54) Enforce wide links = no on files as well as directories 55) Include shared library checks for Stratus VOS 56) Include support for CUPS printer classes and logging the remote client name 57) Include "WinXP" (Windows XP) and "Win2K3" (Windows .NET) values for %a 58) Increase the max PDU size to deal with some troublesome printer drivers and Windows NT 4.0 clients 59) increment the process counter immediately after the fork (not just when we receive the first smb packet) 60) Ensure rename sets errno correctly 61) Unify ACL code (back-port from 3.0) 62) Fix some further issues around off_t and large offsets -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.0 (GNU/Linux) Comment: For info see http://quantumlab.net/pine_privacy_guard/ iD8DBQE+czUBIR7qMdg1EfYRAtw3AJ0aOssqot9nSJPrtdciVxb/Q2DxTQCgtHEA VK0cv2KDuqWWoLesbW1tQpM= =GIxq -----END PGP SIGNATURE-----
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