(RHSA-2016:0624) Critical: samba3x security update

Samba is an open-source implementation of the Server Message Block (SMB) or
Common Internet File System (CIFS) protocol, which allows PC-compatible machines
to share files, printers, and other information.

Security Fix(es):

• Multiple flaws were found in Samba’s DCE/RPC protocol implementation. A
  remote, authenticated attacker could use these flaws to cause a denial of
  service against the Samba server (high CPU load or a crash) or, possibly,
  execute arbitrary code with the permissions of the user running Samba (root).
  This flaw could also be used to downgrade a secure DCE/RPC connection by a
  man-in-the-middle attacker taking control of an Active Directory (AD) object and
  compromising the security of a Samba Active Directory Domain Controller (DC).
  (CVE-2015-5370)

Note: While Samba packages as shipped in Red Hat Enterprise Linux do not support
running Samba as an AD DC, this flaw applies to all roles Samba implements.

• A protocol flaw, publicly referred to as Badlock, was found in the Security
  Account Manager Remote Protocol (MS-SAMR) and the Local Security Authority
  (Domain Policy) Remote Protocol (MS-LSAD). Any authenticated DCE/RPC connection
  that a client initiates against a server could be used by a man-in-the-middle
  attacker to impersonate the authenticated user against the SAMR or LSA service
  on the server. As a result, the attacker would be able to get read/write access
  to the Security Account Manager database, and use this to reveal all passwords
  or any other potentially sensitive information in that database. (CVE-2016-2118)

• Several flaws were found in Samba’s implementation of NTLMSSP authentication.
  An unauthenticated, man-in-the-middle attacker could use this flaw to clear the
  encryption and integrity flags of a connection, causing data to be transmitted
  in plain text. The attacker could also force the client or server into sending
  data in plain text even if encryption was explicitly requested for that
  connection. (CVE-2016-2110)

• It was discovered that Samba configured as a Domain Controller would establish
  a secure communication channel with a machine using a spoofed computer name. A
  remote attacker able to observe network traffic could use this flaw to obtain
  session-related information about the spoofed machine. (CVE-2016-2111)

• It was found that Samba’s LDAP implementation did not enforce integrity
  protection for LDAP connections. A man-in-the-middle attacker could use this
  flaw to downgrade LDAP connections to use no integrity protection, allowing them
  to hijack such connections. (CVE-2016-2112)

• It was found that Samba did not enable integrity protection for IPC traffic by
  default. A man-in-the-middle attacker could use this flaw to view and modify the
  data sent between a Samba server and a client. (CVE-2016-2115)

Red Hat would like to thank the Samba project for reporting these issues.
Upstream acknowledges Jouni Knuutinen (Synopsis) as the original reporter of
CVE-2015-5370; and Stefan Metzmacher (SerNet) as the original reporter of
CVE-2016-2118, CVE-2016-2110, CVE-2016-2112, and CVE-2016-2115.