r818: added server side SMB signing to Samba4

(This used to be commit 8e5ddf5e8eb74f667897f90baa2d00f02ca5818b)

7 files changed, 196 insertions, 8 deletions

diff --git a/source4/smb_server/config.m4 b/source4/smb_server/config.m4
index e94dbf1444..4722faf8bb 100644
--- a/source4/smb_server/config.m4
+++ b/source4/smb_server/config.m4
@@ -13,4 +13,5 @@ SMB_SUBSYSTEM(SMB,smb_server/smb_server.o,
 		smb_server/session.o
 		smb_server/sesssetup.o
 		smb_server/srvtime.o
-		smb_server/trans2.o])
+		smb_server/trans2.o
+		smb_server/signing.o])
diff --git a/source4/smb_server/negprot.c b/source4/smb_server/negprot.c
index d9d65d4cf2..253dc1d7a4 100644
--- a/source4/smb_server/negprot.c
+++ b/source4/smb_server/negprot.c
@@ -288,6 +288,20 @@ static void reply_nt1(struct request_context *req, uint16 choice)
 	if (req->smb->negotiate.encrypted_passwords) {
 		secword |= NEGOTIATE_SECURITY_CHALLENGE_RESPONSE;
 	}
+
+	req->smb->signing.signing_state = lp_server_signing();
+
+	switch (req->smb->signing.signing_state) {
+	case SMB_SIGNING_OFF:
+		break;
+	case SMB_SIGNING_SUPPORTED:
+		secword |= NEGOTIATE_SECURITY_SIGNATURES_ENABLED;
+		break;
+	case SMB_SIGNING_REQUIRED:
+		secword |= NEGOTIATE_SECURITY_SIGNATURES_ENABLED |
+			NEGOTIATE_SECURITY_SIGNATURES_REQUIRED;
+		break;
+	}
 	
 	req->smb->negotiate.protocol = PROTOCOL_NT1;
 
@@ -334,7 +348,7 @@ static void reply_nt1(struct request_context *req, uint16 choice)
 #endif
 	}
 	
-	req_send_reply(req);	
+	req_send_reply_nosign(req);	
 }
 
 /* these are the protocol lists used for auto architecture detection:
diff --git a/source4/smb_server/reply.c b/source4/smb_server/reply.c
index 8b9bb4fb5e..073ee956ca 100644
--- a/source4/smb_server/reply.c
+++ b/source4/smb_server/reply.c
@@ -710,7 +710,8 @@ failed:
 	req->out.size = 4;
 	req->out.buffer = talloc(req->mem_ctx, req->out.size);
 	SIVAL(req->out.buffer, 0, 0); /* init NBT header */
-	req_send_reply(req);
+
+	req_send_reply_nosign(req);
 }
 
 
@@ -2335,7 +2336,7 @@ void reply_special(struct request_context *req)
 		
 		req->out.buffer = buf;
 		req->out.size = 4;
-		req_send_reply(req);
+		req_send_reply_nosign(req);
 		return;
 		
 	case 0x89: /* session keepalive request 
@@ -2344,7 +2345,7 @@ void reply_special(struct request_context *req)
 		SCVAL(buf, 3, 0);
 		req->out.buffer = buf;
 		req->out.size = 4;
-		req_send_reply(req);
+		req_send_reply_nosign(req);
 		return;
 		
 	case SMBkeepalive: 
diff --git a/source4/smb_server/request.c b/source4/smb_server/request.c
index 964f4a2d70..5c1d14a9d0 100644
--- a/source4/smb_server/request.c
+++ b/source4/smb_server/request.c
@@ -256,7 +256,7 @@ void req_grow_data(struct request_context *req, unsigned new_size)
   note that this only looks at req->out.buffer and req->out.size, allowing manually 
   constructed packets to be sent
 */
-void req_send_reply(struct request_context *req)
+void req_send_reply_nosign(struct request_context *req)
 {
 	if (req->out.size > NBT_HDR_SIZE) {
 		_smb_setlen(req->out.buffer, req->out.size - NBT_HDR_SIZE);
@@ -269,6 +269,23 @@ void req_send_reply(struct request_context *req)
 	req_destroy(req);
 }
 
+/*
+  possibly sign a message then send a reply and destroy the request buffer
+
+  note that this only looks at req->out.buffer and req->out.size, allowing manually 
+  constructed packets to be sent
+*/
+void req_send_reply(struct request_context *req)
+{
+	if (req->out.size > NBT_HDR_SIZE) {
+		_smb_setlen(req->out.buffer, req->out.size - NBT_HDR_SIZE);
+	}
+
+	req_sign_packet(req);
+
+	req_send_reply_nosign(req);
+}
+
 
 
 /* 
diff --git a/source4/smb_server/sesssetup.c b/source4/smb_server/sesssetup.c
index f42efcb7ec..fdcc1d298a 100644
--- a/source4/smb_server/sesssetup.c
+++ b/source4/smb_server/sesssetup.c
@@ -127,6 +127,8 @@ static NTSTATUS sesssetup_nt1(struct request_context *req, union smb_sesssetup *
 				 &sess->nt1.out.lanman,
 				 &sess->nt1.out.domain);
 
+	srv_setup_signing(req->smb, &session_key, &sess->nt1.in.password2);
+
 	return NT_STATUS_OK;
 }
 
diff --git a/source4/smb_server/signing.c b/source4/smb_server/signing.c
new file mode 100644
index 0000000000..a3779e17cf
--- /dev/null
+++ b/source4/smb_server/signing.c
@@ -0,0 +1,149 @@
+/* 
+   Unix SMB/CIFS implementation.
+   
+   Copyright (C) Andrew Tridgell              2004
+   
+   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 2 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, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "includes.h"
+
+/*
+  mark the flags2 field in a packet as signed
+*/
+static void mark_packet_signed(struct request_context *req) 
+{
+	uint16 flags2;
+	flags2 = SVAL(req->out.hdr, HDR_FLG2);
+	flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES;
+	SSVAL(req->out.hdr, HDR_FLG2, flags2);
+}
+
+/*
+  calculate the signature for a message
+*/
+static void calc_signature(uint8 *buffer, size_t length,
+			   DATA_BLOB *mac_key, uint8 signature[8])
+{
+	unsigned char calc_md5_mac[16];
+	struct MD5Context md5_ctx;
+
+	MD5Init(&md5_ctx);
+	MD5Update(&md5_ctx, mac_key->data, mac_key->length); 
+	MD5Update(&md5_ctx, buffer, length);
+	MD5Final(calc_md5_mac, &md5_ctx);
+	memcpy(signature, calc_md5_mac, 8);
+}
+			   
+
+/*
+  sign an outgoing packet
+*/
+void req_sign_packet(struct request_context *req)
+{
+	/* check if we are doing signing on this connection */
+	if (req->smb->signing.signing_state != SMB_SIGNING_REQUIRED) {
+		return;
+	}
+
+	SBVAL(req->out.hdr, HDR_SS_FIELD, req->seq_num+1);
+
+	mark_packet_signed(req);
+
+	calc_signature(req->out.hdr, req->out.size - NBT_HDR_SIZE,
+		       &req->smb->signing.mac_key, 
+		       &req->out.hdr[HDR_SS_FIELD]);
+}
+
+
+/*
+  setup the signing key for a connection. Called after authentication succeeds
+  in a session setup
+*/
+void srv_setup_signing(struct server_context *smb,
+		       DATA_BLOB *session_key,
+		       DATA_BLOB *session_response)
+{
+	smb->signing.mac_key = data_blob(NULL, 
+					 session_key->length + session_response->length);
+	memcpy(smb->signing.mac_key.data, session_key->data, session_key->length);
+	if (session_response->length != 0) {
+		memcpy(&smb->signing.mac_key.data[session_key->length],
+		       session_response->data, 
+		       session_response->length);
+	}
+}
+
+
+/*
+  allocate a sequence number to a request
+*/
+static void req_signing_alloc_seq_num(struct request_context *req)
+{
+	req->seq_num = req->smb->signing.next_seq_num;
+
+	/* TODO: we need to handle one-way requests like NTcancel, which 
+	   only increment the sequence number by 1 */
+	if (req->smb->signing.signing_state != SMB_SIGNING_OFF) {
+		req->smb->signing.next_seq_num += 2;
+	}
+}
+
+/*
+  check the signature of an incoming packet
+*/
+BOOL req_signing_check_incoming(struct request_context *req)
+{
+	unsigned char client_md5_mac[8], signature[8];
+
+	switch (req->smb->signing.signing_state) {
+	case SMB_SIGNING_OFF:
+		return True;
+	case SMB_SIGNING_SUPPORTED:
+		if (req->flags2 & FLAGS2_SMB_SECURITY_SIGNATURES) {
+			req->smb->signing.signing_state = SMB_SIGNING_REQUIRED;
+		}
+		return True;
+	case SMB_SIGNING_REQUIRED:
+		break;
+	}
+
+	req_signing_alloc_seq_num(req);
+
+	/* the first packet isn't checked as the key hasn't been established */
+	if (req->seq_num == 0) {
+		return True;
+	}
+
+	/* room enough for the signature? */
+	if (req->in.size < NBT_HDR_SIZE + HDR_SS_FIELD + 8) {
+		return False;
+	}
+
+	memcpy(client_md5_mac, req->in.hdr + HDR_SS_FIELD, 8);
+
+	SBVAL(req->in.hdr, HDR_SS_FIELD, req->seq_num);
+
+	calc_signature(req->in.hdr, req->in.size - NBT_HDR_SIZE,
+		       &req->smb->signing.mac_key, 
+		       signature);
+
+	if (memcmp(client_md5_mac, signature, 8) != 0) {
+		DEBUG(2,("Bad SMB signature seq_num=%d\n", (int)req->seq_num));
+		return False;
+	}
+
+	return True;
+}
diff --git a/source4/smb_server/smb_server.c b/source4/smb_server/smb_server.c
index aceae08ad8..ce50df04c3 100644
--- a/source4/smb_server/smb_server.c
+++ b/source4/smb_server/smb_server.c
@@ -558,7 +558,6 @@ static void construct_reply(struct request_context *req)
 		return;
 	}
 
-
 	/* Make sure this is an SMB packet */	
 	if (memcmp(req->in.hdr,"\377SMB",4) != 0) {
 		DEBUG(2,("Non-SMB packet of length %d. Terminating connection\n", 
@@ -584,6 +583,11 @@ static void construct_reply(struct request_context *req)
 	req->flags = CVAL(req->in.hdr, HDR_FLG);
 	req->flags2 = SVAL(req->in.hdr, HDR_FLG2);
 
+	if (!req_signing_check_incoming(req)) {
+		req_reply_error(req, NT_STATUS_ACCESS_DENIED);
+		return;
+	}
+
 	switch_message(type, req);
 }
 
@@ -733,7 +737,7 @@ void init_smbsession(struct event_context *ev, struct model_ops *model_ops, int
 
 	mem_ctx = talloc_init("server_context");
 
-	smb = (struct server_context *)talloc(mem_ctx, sizeof(*smb));
+	smb = talloc_p(mem_ctx, struct server_context);
 	if (!smb) return;
 
 	ZERO_STRUCTP(smb);