From 2db6ad194de08ee20bd2ad04493bb21245982005 Mon Sep 17 00:00:00 2001 From: Stefan Metzmacher Date: Thu, 24 Nov 2016 09:12:59 +0100 Subject: [PATCH 1/2] CVE-2016-2124: s4:libcli/sesssetup: don't fallback to non spnego authentication if we require kerberos We should not send NTLM[v2] data on the wire if the user asked for kerberos only. BUG: https://bugzilla.samba.org/show_bug.cgi?id=12444 Signed-off-by: Stefan Metzmacher --- source4/libcli/smb_composite/sesssetup.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/source4/libcli/smb_composite/sesssetup.c b/source4/libcli/smb_composite/sesssetup.c index 6ee4929e8d7..a0a1f4baa56 100644 --- a/source4/libcli/smb_composite/sesssetup.c +++ b/source4/libcli/smb_composite/sesssetup.c @@ -620,6 +620,8 @@ struct composite_context *smb_composite_sesssetup_send(struct smbcli_session *se struct composite_context *c; struct sesssetup_state *state; NTSTATUS status; + enum credentials_use_kerberos krb5_state = + cli_credentials_get_kerberos_state(io->in.credentials); c = composite_create(session, session->transport->ev); if (c == NULL) return NULL; @@ -635,6 +637,10 @@ struct composite_context *smb_composite_sesssetup_send(struct smbcli_session *se /* no session setup at all in earliest protocol varients */ if (session->transport->negotiate.protocol < PROTOCOL_LANMAN1) { + if (krb5_state == CRED_MUST_USE_KERBEROS) { + composite_error(c, NT_STATUS_NETWORK_CREDENTIAL_CONFLICT); + return c; + } ZERO_STRUCT(io->out); composite_done(c); return c; @@ -642,9 +648,17 @@ struct composite_context *smb_composite_sesssetup_send(struct smbcli_session *se /* see what session setup interface we will use */ if (session->transport->negotiate.protocol < PROTOCOL_NT1) { + if (krb5_state == CRED_MUST_USE_KERBEROS) { + composite_error(c, NT_STATUS_NETWORK_CREDENTIAL_CONFLICT); + return c; + } status = session_setup_old(c, session, io, &state->req); } else if (!session->transport->options.use_spnego || !(io->in.capabilities & CAP_EXTENDED_SECURITY)) { + if (krb5_state == CRED_MUST_USE_KERBEROS) { + composite_error(c, NT_STATUS_NETWORK_CREDENTIAL_CONFLICT); + return c; + } status = session_setup_nt1(c, session, io, &state->req); } else { struct tevent_req *subreq = NULL; -- 2.25.1 From f3221aac07a4339b9c7941414e16ec383e9cdb67 Mon Sep 17 00:00:00 2001 From: Stefan Metzmacher Date: Thu, 27 Oct 2016 10:40:28 +0200 Subject: [PATCH 2/2] CVE-2016-2124: s3:libsmb: don't fallback to non spnego authentication if we require kerberos We should not send NTLM[v2] nor plaintext data on the wire if the user asked for kerberos only. BUG: https://bugzilla.samba.org/show_bug.cgi?id=12444 Signed-off-by: Stefan Metzmacher [jsutton@samba.org Removed addition of cli_credentials_get_kerberos_state() call already existing in 4.12] --- source3/libsmb/cliconnect.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/source3/libsmb/cliconnect.c b/source3/libsmb/cliconnect.c index 9bba2665663..9a69d4b7217 100644 --- a/source3/libsmb/cliconnect.c +++ b/source3/libsmb/cliconnect.c @@ -1455,6 +1455,13 @@ struct tevent_req *cli_session_setup_creds_send(TALLOC_CTX *mem_ctx, return req; } + if (krb5_state == CRED_MUST_USE_KERBEROS) { + DBG_WARNING("Kerberos authentication requested, but " + "the server does not support SPNEGO authentication\n"); + tevent_req_nterror(req, NT_STATUS_NETWORK_CREDENTIAL_CONFLICT); + return tevent_req_post(req, ev); + } + if (smbXcli_conn_protocol(cli->conn) < PROTOCOL_LANMAN1) { /* * SessionSetupAndX was introduced by LANMAN 1.0. So we skip -- 2.25.1