For more information ask please ask me privately via encrypted mail to metze@samba.org sec# 8192R/6A739B025C6B98D4 2015-09-28 [expires: 2016-09-27] Key fingerprint = A3D1 92CE 44EF 4125 17BC ED64 6A73 9B02 5C6B 98D4 uid Stefan Metzmacher <metze@samba.org> ssb 4096R/0DB5F5612869BD56 2015-09-28 ssb 4096R/BFD5085E9D32D974 2015-09-28
TLS related
CVE number requested...
=================================================================================== == Subject: Missing TLS certificate validation allows man in the middle attacks == == CVE ID#: CVE-2016-2113 == == Versions: Samba 4.0.0 to 4.4.0 == == Summary: Man in the middle attacks are possible for client triggered LDAP == connections (with ldaps://) and ncacn_http connections == (with https://). == =================================================================================== =========== Description =========== Samba has support for TLS/SSL for some protocols: ldap and http, but currently certificates are not validated at all. While we have a "tls cafile" option, the configured certificate is not used to validate the server certificate. This applies to ldaps:// connections triggered by tools like: "ldbsearch", "ldbedit" and more. Note that it only applies to the ldb tools when they are built as part of Samba or with Samba extensions installed, which means the Samba builtin LDAP client library is used. It also applies to dcerpc client connections using ncacn_http (with https://), which are only used by the openchange project. Support for ncacn_http was introduced in version 4.2.0. The security patches will introduce a new option called "tls verify peer". Possible values are "no_check", "ca_only", "ca_and_name_if_available", "ca_and_name" and "as_strict_as_possible". If you use the self-signed certificates which are auto-generated by Samba, you won't have a crl file and need to explicitly set "tls verify peer = ca_and_name". =================== New smb.conf option =================== tls verify peer (G) This controls if and how strict the client will verify the peer's certificate and name. Possible values are (in increasing order): no_check, ca_only, ca_and_name_if_available, ca_and_name and as_strict_as_possible. When set to no_check the certificate is not verified at all, which allows trivial man in the middle attacks. When set to ca_only the certificate is verified to be signed from a ca specified in the "tls ca file" option. Setting "tls ca file" to a valid file is required. The certificate lifetime is also verified. If the "tls crl file" option is configured, the certificate is also verified against the ca crl. When set to ca_and_name_if_available all checks from ca_only are performed. In addition, the peer hostname is verified against the certificate's name, if it is provided by the application layer and not given as an ip address string. When set to ca_and_name all checks from ca_and_name_if_available are performed. In addition the peer hostname needs to be provided and even an ip address is checked against the certificate's name. When set to as_strict_as_possible all checks from ca_and_name are performed. In addition the "tls crl file" needs to be configured. Future versions of Samba may implement additional checks. Default: tls verify peer = as_strict_as_possible ================== Patch Availability ================== A patch addressing this defect has been posted to https://www.samba.org/samba/security/ Additionally, Samba 4.4.2, 4.3.8 and 4.2.11 have been issued as security releases to correct the defect. Samba vendors and administrators running affected versions are advised to upgrade or apply the patch as soon as possible. Note that Samba 4.4.1, 4.3.7 and 4.2.10 were privately released to vendors, but had a regression, which is fixed in 4.4.2, 4.3.8 and 4.2.11. ========== Workaround ========== None. ======= Credits ======= This vulnerability was discovered and researched by Stefan Metzmacher of SerNet (https://samba.plus) and the Samba Team (https://www.samba.org). He provides the fixes in collaboration with the Samba Team.
The fixes are in v4-{2,3,4}-{stable,test} and master.
Opening this up to non-vendors.