s3:smbd: add support for SMB2 signing
authorStefan Metzmacher <metze@samba.org>
Fri, 22 May 2009 20:58:39 +0000 (22:58 +0200)
committerStefan Metzmacher <metze@samba.org>
Tue, 26 May 2009 07:53:06 +0000 (09:53 +0200)
metze

source3/Makefile.in
source3/smbd/globals.h
source3/smbd/smb2_server.c
source3/smbd/smb2_sesssetup.c
source3/smbd/smb2_signing.c [new file with mode: 0644]

index 1120092f9091447cb089d22efad2cc59d493ad3f..2b30b4a5bd5f540a126399d39528e92ee916dd01 100644 (file)
@@ -359,7 +359,8 @@ UTIL_OBJ = ../lib/util/rbtree.o ../lib/util/signal.o ../lib/util/time.o \
 
 CRYPTO_OBJ = ../lib/crypto/crc32.o ../lib/crypto/md5.o \
                         ../lib/crypto/hmacmd5.o ../lib/crypto/arcfour.o \
-                        ../lib/crypto/md4.o
+                        ../lib/crypto/md4.o \
+                        ../lib/crypto/sha256.o ../lib/crypto/hmacsha256.o
 
 LIB_OBJ = $(LIBSAMBAUTIL_OBJ) $(UTIL_OBJ) $(CRYPTO_OBJ) \
          lib/messages.o librpc/gen_ndr/ndr_messaging.o lib/messages_local.o \
@@ -750,7 +751,7 @@ SMBD_OBJ_SRV = smbd/files.o smbd/chgpasswd.o smbd/connection.o \
               smbd/dnsregister.o smbd/globals.o \
               smbd/smb2_server.o smbd/smb2_negprot.o \
               smbd/smb2_sesssetup.o smbd/smb2_tcon.o \
-              smbd/smb2_keepalive.o \
+              smbd/smb2_keepalive.o smbd/smb2_signing.o \
               $(MANGLE_OBJ) @VFS_STATIC@
 
 SMBD_OBJ_BASE = $(PARAM_WITHOUT_REG_OBJ) $(SMBD_OBJ_SRV) $(LIBSMB_OBJ) \
index 9d5eead93976dbfefc9cd55ad9e8c1cc5d2aedcd..c6ab31dc36e49141a796f363f4977fa9a3d06f95 100644 (file)
@@ -206,6 +206,13 @@ struct smbd_smb2_tcon;
 
 DATA_BLOB negprot_spnego(void);
 
+NTSTATUS smb2_signing_sign_pdu(DATA_BLOB session_key,
+                              struct iovec *vector,
+                              int count);
+NTSTATUS smb2_signing_check_pdu(DATA_BLOB session_key,
+                               const struct iovec *vector,
+                               int count);
+
 bool smbd_is_smb2_header(const uint8_t *inbuf, size_t size);
 
 void reply_smb2002(struct smb_request *req, uint16_t choice);
@@ -244,6 +251,7 @@ struct smbd_smb2_request {
        struct smbd_smb2_tcon *tcon;
 
        int current_idx;
+       bool do_signing;
 
        struct {
                /* the NBT header is not allocated */
@@ -299,6 +307,9 @@ struct smbd_smb2_session {
        NTSTATUS status;
        uint64_t vuid;
        AUTH_NTLMSSP_STATE *auth_ntlmssp_state;
+       struct auth_serversupplied_info *server_info;
+       DATA_BLOB session_key;
+       bool do_signing;
 
        struct {
                /* an id tree used to allocate tids */
index 32bb5543aeeff3c4d33fa8287ce8a8b9ec6daf3f..562fc567cc23e0d2193f254df427701ce5f7dd89 100644 (file)
@@ -288,14 +288,45 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
        const uint8_t *inhdr;
        int i = req->current_idx;
        uint16_t opcode;
+       uint32_t flags;
        NTSTATUS status;
+       NTSTATUS session_status;
 
        inhdr = (const uint8_t *)req->in.vector[i].iov_base;
 
        /* TODO: verify more things */
 
+       flags = IVAL(inhdr, SMB2_HDR_FLAGS);
        opcode = IVAL(inhdr, SMB2_HDR_OPCODE);
        DEBUG(10,("smbd_smb2_request_dispatch: opcode[%u]\n", opcode));
+
+#define TMP_SMB2_ALLOWED_FLAGS ( \
+       SMB2_HDR_FLAG_CHAINED | \
+       SMB2_HDR_FLAG_SIGNED | \
+       SMB2_HDR_FLAG_DFS)
+       if ((flags & ~TMP_SMB2_ALLOWED_FLAGS) != 0) {
+               return smbd_smb2_request_error(req, NT_STATUS_INVALID_PARAMETER);
+       }
+#undef TMP_SMB2_ALLOWED_FLAGS
+
+       session_status = smbd_smb2_request_check_session(req);
+
+       req->do_signing = false;
+       if (flags & SMB2_HDR_FLAG_SIGNED) {
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
+               }
+
+               req->do_signing = true;
+               status = smb2_signing_check_pdu(req->session->session_key,
+                                               &req->in.vector[i], 3);
+               if (!NT_STATUS_IS_OK(status)) {
+                       return smbd_smb2_request_error(req, status);
+               }
+       } else if (req->session && req->session->do_signing) {
+               return smbd_smb2_request_error(req, NT_STATUS_ACCESS_DENIED);
+       }
+
        switch (opcode) {
        case SMB2_OP_NEGPROT:
                return smbd_smb2_request_process_negprot(req);
@@ -304,13 +335,15 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_process_sesssetup(req);
 
        case SMB2_OP_LOGOFF:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                return smbd_smb2_request_process_logoff(req);
 
        case SMB2_OP_TCON:
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
+               }
                status = smbd_smb2_request_check_session(req);
                if (!NT_STATUS_IS_OK(status)) {
                        return smbd_smb2_request_error(req, status);
@@ -318,9 +351,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_process_tcon(req);
 
        case SMB2_OP_TDIS:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -329,9 +361,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_process_tdis(req);
 
        case SMB2_OP_CREATE:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -340,9 +371,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_CLOSE:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -351,9 +381,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_FLUSH:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -362,9 +391,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_READ:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -373,9 +401,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_WRITE:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -384,9 +411,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_LOCK:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -395,9 +421,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_IOCTL:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -412,9 +437,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_process_keepalive(req);
 
        case SMB2_OP_FIND:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -423,9 +447,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_NOTIFY:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -434,9 +457,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_GETINFO:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -445,9 +467,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_SETINFO:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -456,9 +477,8 @@ static NTSTATUS smbd_smb2_request_dispatch(struct smbd_smb2_request *req)
                return smbd_smb2_request_error(req, NT_STATUS_NOT_IMPLEMENTED);
 
        case SMB2_OP_BREAK:
-               status = smbd_smb2_request_check_session(req);
-               if (!NT_STATUS_IS_OK(status)) {
-                       return smbd_smb2_request_error(req, status);
+               if (!NT_STATUS_IS_OK(session_status)) {
+                       return smbd_smb2_request_error(req, session_status);
                }
                status = smbd_smb2_request_check_tcon(req);
                if (!NT_STATUS_IS_OK(status)) {
@@ -481,6 +501,16 @@ static NTSTATUS smbd_smb2_request_reply(struct smbd_smb2_request *req)
 
        smb2_setup_nbt_length(req->out.vector, req->out.vector_count);
 
+       if (req->do_signing) {
+               int i = req->current_idx;
+               NTSTATUS status;
+               status = smb2_signing_sign_pdu(req->session->session_key,
+                                              &req->out.vector[i], 3);
+               if (!NT_STATUS_IS_OK(status)) {
+                       return status;
+               }
+       }
+
        req->current_idx += 3;
 
        if (req->current_idx > req->in.vector_count) {
index fafda24ca474af6f93c5f351fdb7732c488f8437..be37aec04d32b107830d74eb1ff4d3d78ed9f8a2 100644 (file)
@@ -24,7 +24,9 @@
 
 static NTSTATUS smbd_smb2_session_setup(struct smbd_smb2_request *req,
                                        uint64_t in_session_id,
+                                       uint8_t in_security_mode,
                                        DATA_BLOB in_security_buffer,
+                                       uint16_t *out_session_flags,
                                        DATA_BLOB *out_security_buffer,
                                        uint64_t *out_session_id);
 
@@ -39,9 +41,11 @@ NTSTATUS smbd_smb2_request_process_sesssetup(struct smbd_smb2_request *req)
        size_t expected_body_size = 0x19;
        size_t body_size;
        uint64_t in_session_id;
+       uint8_t in_security_mode;
        uint16_t in_security_offset;
        uint16_t in_security_length;
        DATA_BLOB in_security_buffer;
+       uint16_t out_session_flags;
        uint64_t out_session_id;
        uint16_t out_security_offset;
        DATA_BLOB out_security_buffer;
@@ -72,12 +76,15 @@ NTSTATUS smbd_smb2_request_process_sesssetup(struct smbd_smb2_request *req)
        }
 
        in_session_id = BVAL(inhdr, SMB2_HDR_SESSION_ID);
+       in_security_mode = CVAL(inbody, 0x03);
        in_security_buffer.data = (uint8_t *)req->in.vector[i+2].iov_base;
        in_security_buffer.length = in_security_length;
 
        status = smbd_smb2_session_setup(req,
                                         in_session_id,
+                                        in_security_mode,
                                         in_security_buffer,
+                                        &out_session_flags,
                                         &out_security_buffer,
                                         &out_session_id);
        if (!NT_STATUS_IS_OK(status) &&
@@ -98,7 +105,8 @@ NTSTATUS smbd_smb2_request_process_sesssetup(struct smbd_smb2_request *req)
        SBVAL(outhdr, SMB2_HDR_SESSION_ID, out_session_id);
 
        SSVAL(outbody.data, 0x00, 0x08 + 1);    /* struct size */
-       SSVAL(outbody.data, 0x02, 0);           /* session flags */
+       SSVAL(outbody.data, 0x02,
+             out_session_flags);               /* session flags */
        SSVAL(outbody.data, 0x04,
              out_security_offset);             /* security buffer offset */
        SSVAL(outbody.data, 0x06,
@@ -132,13 +140,17 @@ static int smbd_smb2_session_destructor(struct smbd_smb2_session *session)
 
 static NTSTATUS smbd_smb2_session_setup(struct smbd_smb2_request *req,
                                        uint64_t in_session_id,
+                                       uint8_t in_security_mode,
                                        DATA_BLOB in_security_buffer,
+                                       uint16_t *out_session_flags,
                                        DATA_BLOB *out_security_buffer,
                                        uint64_t *out_session_id)
 {
        struct smbd_smb2_session *session;
        NTSTATUS status;
 
+       *out_session_flags = 0;
+
        if (in_session_id == 0) {
                int id;
 
@@ -185,6 +197,7 @@ static NTSTATUS smbd_smb2_session_setup(struct smbd_smb2_request *req,
        if (session->auth_ntlmssp_state == NULL) {
                status = auth_ntlmssp_start(&session->auth_ntlmssp_state);
                if (!NT_STATUS_IS_OK(status)) {
+                       TALLOC_FREE(session);
                        return status;
                }
        }
@@ -193,19 +206,54 @@ static NTSTATUS smbd_smb2_session_setup(struct smbd_smb2_request *req,
                                     in_security_buffer,
                                     out_security_buffer);
        if (NT_STATUS_EQUAL(status, NT_STATUS_MORE_PROCESSING_REQUIRED)) {
-               /* nothing to do */
-       } else if (NT_STATUS_IS_OK(status)) {
-               /* TODO: setup session key for signing */
-               session->status = NT_STATUS_OK;
-               /*
-                * we attach the session to the request
-                * so that the response can be signed
-                */
-               req->session = session;
-       } else {
+               *out_session_id = session->vuid;
+               return status;
+       } else if (!NT_STATUS_IS_OK(status)) {
+               TALLOC_FREE(session);
                return status;
        }
 
+       /* TODO: setup session key for signing */
+
+       if ((in_security_mode & SMB2_NEGOTIATE_SIGNING_REQUIRED) ||
+           lp_server_signing() == Required) {
+               session->do_signing = true;
+       }
+
+       if (session->auth_ntlmssp_state->server_info->guest) {
+               /* we map anonymous to guest internally */
+               *out_session_flags |= SMB2_SESSION_FLAG_IS_GUEST;
+               *out_session_flags |= SMB2_SESSION_FLAG_IS_NULL;
+               /* force no signing */
+               session->do_signing = false;
+       }
+
+       session->server_info = session->auth_ntlmssp_state->server_info;
+       data_blob_free(&session->server_info->user_session_key);
+       session->server_info->user_session_key =
+                       data_blob_talloc(
+                       session->server_info,
+                       session->auth_ntlmssp_state->ntlmssp_state->session_key.data,
+                       session->auth_ntlmssp_state->ntlmssp_state->session_key.length);
+       if (session->auth_ntlmssp_state->ntlmssp_state->session_key.length > 0) {
+               if (session->server_info->user_session_key.data == NULL) {
+                       TALLOC_FREE(session);
+                       return NT_STATUS_NO_MEMORY;
+               }
+       }
+       session->session_key = session->server_info->user_session_key;
+
+       session->status = NT_STATUS_OK;
+
+       /*
+        * we attach the session to the request
+        * so that the response can be signed
+        */
+       req->session = session;
+       if (session->do_signing) {
+               req->do_signing = true;
+       }
+
        *out_session_id = session->vuid;
        return status;
 }
diff --git a/source3/smbd/smb2_signing.c b/source3/smbd/smb2_signing.c
new file mode 100644 (file)
index 0000000..55ed4f6
--- /dev/null
@@ -0,0 +1,135 @@
+/*
+   Unix SMB/CIFS implementation.
+   SMB2 signing
+
+   Copyright (C) Stefan Metzmacher 2009
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include "smbd/globals.h"
+#include "../source4/libcli/smb2/smb2_constants.h"
+#include "../lib/crypto/crypto.h"
+
+NTSTATUS smb2_signing_sign_pdu(DATA_BLOB session_key,
+                              struct iovec *vector,
+                              int count)
+{
+       uint8_t *hdr;
+       uint64_t session_id;
+       struct HMACSHA256Context m;
+       uint8_t res[SHA256_DIGEST_LENGTH];
+       int i;
+
+       if (count < 2) {
+               return NT_STATUS_INVALID_PARAMETER;
+       }
+
+       if (vector[0].iov_len != SMB2_HDR_BODY) {
+               return NT_STATUS_INVALID_PARAMETER;
+       }
+
+       hdr = (uint8_t *)vector[0].iov_base;
+
+       session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
+       if (session_id == 0) {
+               /*
+                * do not sign messages with a zero session_id.
+                * See MS-SMB2 3.2.4.1.1
+                */
+               return NT_STATUS_OK;
+       }
+
+       if (session_key.length == 0) {
+               DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
+                        (unsigned)session_key.length));
+               return NT_STATUS_ACCESS_DENIED;
+       }
+
+       memset(hdr + SMB2_HDR_SIGNATURE, 0, 16);
+
+       SIVAL(hdr, SMB2_HDR_FLAGS, IVAL(hdr, SMB2_HDR_FLAGS) | SMB2_HDR_FLAG_SIGNED);
+
+       ZERO_STRUCT(m);
+       hmac_sha256_init(session_key.data, MIN(session_key.length, 16), &m);
+       for (i=0; i < count; i++) {
+               hmac_sha256_update((const uint8_t *)vector[i].iov_base,
+                                  vector[i].iov_len, &m);
+       }
+       hmac_sha256_final(res, &m);
+       DEBUG(5,("signed SMB2 message\n"));
+
+       memcpy(hdr + SMB2_HDR_SIGNATURE, res, 16);
+
+       return NT_STATUS_OK;
+}
+
+NTSTATUS smb2_signing_check_pdu(DATA_BLOB session_key,
+                               const struct iovec *vector,
+                               int count)
+{
+       const uint8_t *hdr;
+       const uint8_t *sig;
+       uint64_t session_id;
+       struct HMACSHA256Context m;
+       uint8_t res[SHA256_DIGEST_LENGTH];
+       static const uint8_t zero_sig[16];
+       int i;
+
+       if (count < 2) {
+               return NT_STATUS_INVALID_PARAMETER;
+       }
+
+       if (vector[0].iov_len != SMB2_HDR_BODY) {
+               return NT_STATUS_INVALID_PARAMETER;
+       }
+
+       hdr = (const uint8_t *)vector[0].iov_base;
+
+       session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
+       if (session_id == 0) {
+               /*
+                * do not sign messages with a zero session_id.
+                * See MS-SMB2 3.2.4.1.1
+                */
+               return NT_STATUS_OK;
+       }
+
+       if (session_key.length == 0) {
+               /* we don't have the session key yet */
+               return NT_STATUS_OK;
+       }
+
+       sig = hdr+SMB2_HDR_SIGNATURE;
+
+       ZERO_STRUCT(m);
+       hmac_sha256_init(session_key.data, MIN(session_key.length, 16), &m);
+       hmac_sha256_update(hdr, SMB2_HDR_SIGNATURE, &m);
+       hmac_sha256_update(zero_sig, 16, &m);
+       for (i=1; i < count; i++) {
+               hmac_sha256_update((const uint8_t *)vector[i].iov_base,
+                                  vector[i].iov_len, &m);
+       }
+       hmac_sha256_final(res, &m);
+
+       if (memcmp(res, sig, 16) != 0) {
+               DEBUG(0,("Bad SMB2 signature for message\n"));
+               dump_data(0, sig, 16);
+               dump_data(0, res, 16);
+               return NT_STATUS_ACCESS_DENIED;
+       }
+
+       return NT_STATUS_OK;
+}