From 0e0f8ad440ac117685aeed4df16f320c7e9ac1c6 Mon Sep 17 00:00:00 2001
From: Steve French <smfrench@gmail.com>
Date: Fri, 15 Sep 2017 22:51:15 -0500
Subject: [PATCH] [SMB3] Add support for multidialect negotiation (SMB2.1 and
 later)

With the need to discourage use of less secure dialect, SMB1 (CIFS),
we temporarily upgraded the dialect to SMB3, but since there are
various servers which only support SMB2.1 (still much secure than
CIFS/SMB1) but not optimal for a default dialect - add support
for multidialect negotiation.  cifs.ko will now request SMB2.1
or later (ie SMB2.1 or SMB3.0, SMB3.02) and the server will
pick the latest most secure one it can support.

In addition since we are sending multidialect negotiate, add
support for secure negotiate to validate that a man in the
middle didn't downgrade us.

Signed-off-by: Steve French <smfrench@gmail.com>
---
 fs/cifs/cifsglob.h |  6 ++++++
 fs/cifs/connect.c  | 23 ++++++++++++++++-------
 fs/cifs/smb2ops.c  | 40 ++++++++++++++++++++++++++++++++++++++++
 fs/cifs/smb2pdu.c  | 53 ++++++++++++++++++++++++++++++++++++++++++++++-------
 fs/cifs/smb2pdu.h  |  2 +-
 5 files changed, 109 insertions(+), 15 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 808486c..ae4ffb1 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -188,6 +188,8 @@ enum smb_version {
 #ifdef CONFIG_CIFS_SMB311
 	Smb_311,
 #endif /* SMB311 */
+	Smb_3any,
+	Smb_default,
 	Smb_version_err
 };
 
@@ -1701,6 +1703,10 @@ extern struct smb_version_values smb20_values;
 #define SMB21_VERSION_STRING	"2.1"
 extern struct smb_version_operations smb21_operations;
 extern struct smb_version_values smb21_values;
+#define SMB3DEFAULT_VERSION_STRING "default"
+extern struct smb_version_values smbdefault_values;
+#define SMB3ANY_VERSION_STRING "3"
+extern struct smb_version_values smb3any_values;
 #define SMB30_VERSION_STRING	"3.0"
 extern struct smb_version_operations smb30_operations;
 extern struct smb_version_values smb30_values;
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 5aa2d27..d353910 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -301,6 +301,8 @@ static const match_table_t cifs_smb_version_tokens = {
 	{ Smb_311, SMB311_VERSION_STRING },
 	{ Smb_311, ALT_SMB311_VERSION_STRING },
 #endif /* SMB311 */
+	{ Smb_3any, SMB3ANY_VERSION_STRING },
+	{ Smb_default, SMB3DEFAULT_VERSION_STRING },
 	{ Smb_version_err, NULL }
 };
 
@@ -1148,6 +1150,14 @@ cifs_parse_smb_version(char *value, struct smb_vol *vol)
 		vol->vals = &smb311_values;
 		break;
 #endif /* SMB311 */
+	case Smb_3any:
+		vol->ops = &smb30_operations; /* currently identical with 3.0 */
+		vol->vals = &smb3any_values;
+		break;
+	case Smb_default:
+		vol->ops = &smb30_operations; /* currently identical with 3.0 */
+		vol->vals = &smbdefault_values;
+		break;
 	default:
 		cifs_dbg(VFS, "Unknown vers= option specified: %s\n", value);
 		return 1;
@@ -1274,9 +1284,9 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 
 	vol->actimeo = CIFS_DEF_ACTIMEO;
 
-	/* FIXME: add autonegotiation for SMB3 or later rather than just SMB3 */
-	vol->ops = &smb30_operations; /* both secure and accepted widely */
-	vol->vals = &smb30_values;
+	/* offer SMB2.1 and later (SMB3 etc). Secure and widely accepted */
+	vol->ops = &smb30_operations;
+	vol->vals = &smbdefault_values;
 
 	vol->echo_interval = SMB_ECHO_INTERVAL_DEFAULT;
 
@@ -1988,11 +1998,10 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 
 	if (got_version == false)
 		pr_warn("No dialect specified on mount. Default has changed to "
-			"a more secure dialect, SMB3 (vers=3.0), from CIFS "
+			"a more secure dialect, SMB2.1 or later (e.g. SMB3), from CIFS "
 			"(SMB1). To use the less secure SMB1 dialect to access "
-			"old servers which do not support SMB3 specify vers=1.0"
-			" on mount. For somewhat newer servers such as Windows "
-			"7 try vers=2.1.\n");
+			"old servers which do not support SMB3 (or SMB2.1) specify vers=1.0"
+			" on mount.\n");
 
 	kfree(mountdata_copy);
 	return 0;
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index fb2934b..7c1ab9f 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -3110,6 +3110,46 @@ struct smb_version_values smb21_values = {
 	.create_lease_size = sizeof(struct create_lease),
 };
 
+struct smb_version_values smb3any_values = {
+	.version_string = SMB3ANY_VERSION_STRING,
+	.protocol_id = SMB302_PROT_ID, /* doesn't matter, send protocol array */
+	.req_capabilities = SMB2_GLOBAL_CAP_DFS | SMB2_GLOBAL_CAP_LEASING | SMB2_GLOBAL_CAP_LARGE_MTU | SMB2_GLOBAL_CAP_PERSISTENT_HANDLES | SMB2_GLOBAL_CAP_ENCRYPTION,
+	.large_lock_type = 0,
+	.exclusive_lock_type = SMB2_LOCKFLAG_EXCLUSIVE_LOCK,
+	.shared_lock_type = SMB2_LOCKFLAG_SHARED_LOCK,
+	.unlock_lock_type = SMB2_LOCKFLAG_UNLOCK,
+	.header_size = sizeof(struct smb2_hdr),
+	.max_header_size = MAX_SMB2_HDR_SIZE,
+	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.lock_cmd = SMB2_LOCK,
+	.cap_unix = 0,
+	.cap_nt_find = SMB2_NT_FIND,
+	.cap_large_files = SMB2_LARGE_FILES,
+	.signing_enabled = SMB2_NEGOTIATE_SIGNING_ENABLED | SMB2_NEGOTIATE_SIGNING_REQUIRED,
+	.signing_required = SMB2_NEGOTIATE_SIGNING_REQUIRED,
+	.create_lease_size = sizeof(struct create_lease_v2),
+};
+
+struct smb_version_values smbdefault_values = {
+	.version_string = SMB3DEFAULT_VERSION_STRING,
+	.protocol_id = SMB302_PROT_ID, /* doesn't matter, send protocol array */
+	.req_capabilities = SMB2_GLOBAL_CAP_DFS | SMB2_GLOBAL_CAP_LEASING | SMB2_GLOBAL_CAP_LARGE_MTU | SMB2_GLOBAL_CAP_PERSISTENT_HANDLES | SMB2_GLOBAL_CAP_ENCRYPTION,
+	.large_lock_type = 0,
+	.exclusive_lock_type = SMB2_LOCKFLAG_EXCLUSIVE_LOCK,
+	.shared_lock_type = SMB2_LOCKFLAG_SHARED_LOCK,
+	.unlock_lock_type = SMB2_LOCKFLAG_UNLOCK,
+	.header_size = sizeof(struct smb2_hdr),
+	.max_header_size = MAX_SMB2_HDR_SIZE,
+	.read_rsp_size = sizeof(struct smb2_read_rsp) - 1,
+	.lock_cmd = SMB2_LOCK,
+	.cap_unix = 0,
+	.cap_nt_find = SMB2_NT_FIND,
+	.cap_large_files = SMB2_LARGE_FILES,
+	.signing_enabled = SMB2_NEGOTIATE_SIGNING_ENABLED | SMB2_NEGOTIATE_SIGNING_REQUIRED,
+	.signing_required = SMB2_NEGOTIATE_SIGNING_REQUIRED,
+	.create_lease_size = sizeof(struct create_lease_v2),
+};
+
 struct smb_version_values smb30_values = {
 	.version_string = SMB30_VERSION_STRING,
 	.protocol_id = SMB30_PROT_ID,
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 69a751b..c32c394 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -491,10 +491,25 @@ SMB2_negotiate(const unsigned int xid, struct cifs_ses *ses)
 
 	req->hdr.sync_hdr.SessionId = 0;
 
-	req->Dialects[0] = cpu_to_le16(ses->server->vals->protocol_id);
-
-	req->DialectCount = cpu_to_le16(1); /* One vers= at a time for now */
-	inc_rfc1001_len(req, 2);
+	if (strcmp(ses->server->vals->version_string,
+		SMB3ANY_VERSION_STRING) == 0) {
+		req->Dialects[0] = cpu_to_le16(SMB30_PROT_ID);
+		req->Dialects[1] = cpu_to_le16(SMB302_PROT_ID);
+		req->DialectCount = cpu_to_le16(2);
+		inc_rfc1001_len(req, 4);
+	} else if (strcmp(ses->server->vals->version_string,
+		SMB3DEFAULT_VERSION_STRING) == 0) {
+		req->Dialects[0] = cpu_to_le16(SMB21_PROT_ID);
+		req->Dialects[1] = cpu_to_le16(SMB30_PROT_ID);
+		req->Dialects[2] = cpu_to_le16(SMB302_PROT_ID);
+		req->DialectCount = cpu_to_le16(3);
+		inc_rfc1001_len(req, 6);
+	} else {
+		/* otherwise send specific dialect */
+		req->Dialects[0] = cpu_to_le16(ses->server->vals->protocol_id);
+		req->DialectCount = cpu_to_le16(1);
+		inc_rfc1001_len(req, 2);
+	}
 
 	/* only one of SMB2 signing flags may be set in SMB2 request */
 	if (ses->sign)
@@ -558,6 +573,8 @@ SMB2_negotiate(const unsigned int xid, struct cifs_ses *ses)
 	}
 	server->dialect = le16_to_cpu(rsp->DialectRevision);
 
+	/* BB: add check that dialect was valid given dialect(s) we asked for */
+
 	/* SMB2 only has an extended negflavor */
 	server->negflavor = CIFS_NEGFLAVOR_EXTENDED;
 	/* set it to the maximum buffer size value we can send with 1 credit */
@@ -606,6 +623,7 @@ int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
 	struct validate_negotiate_info_req vneg_inbuf;
 	struct validate_negotiate_info_rsp *pneg_rsp;
 	u32 rsplen;
+	u32 inbuflen; /* max of 4 dialects */
 
 	cifs_dbg(FYI, "validate negotiate\n");
 
@@ -634,9 +652,30 @@ int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
 	else
 		vneg_inbuf.SecurityMode = 0;
 
-	vneg_inbuf.DialectCount = cpu_to_le16(1);
-	vneg_inbuf.Dialects[0] =
-		cpu_to_le16(tcon->ses->server->vals->protocol_id);
+
+	if (strcmp(tcon->ses->server->vals->version_string,
+		SMB3ANY_VERSION_STRING) == 0) {
+		vneg_inbuf.Dialects[0] = cpu_to_le16(SMB30_PROT_ID);
+		vneg_inbuf.Dialects[1] = cpu_to_le16(SMB302_PROT_ID);
+		vneg_inbuf.DialectCount = cpu_to_le16(2);
+		/* structure is big enough for 3 dialects, sending only 2 */
+		inbuflen = sizeof(struct validate_negotiate_info_req) - 2;
+	} else if (strcmp(tcon->ses->server->vals->version_string,
+		SMB3DEFAULT_VERSION_STRING) == 0) {
+		vneg_inbuf.Dialects[0] = cpu_to_le16(SMB21_PROT_ID);
+		vneg_inbuf.Dialects[1] = cpu_to_le16(SMB30_PROT_ID);
+		vneg_inbuf.Dialects[2] = cpu_to_le16(SMB302_PROT_ID);
+		vneg_inbuf.DialectCount = cpu_to_le16(3);
+		/* structure is big enough for 3 dialects */
+		inbuflen = sizeof(struct validate_negotiate_info_req);
+	} else {
+		/* otherwise specific dialect was requested */
+		vneg_inbuf.Dialects[0] =
+			cpu_to_le16(tcon->ses->server->vals->protocol_id);
+		vneg_inbuf.DialectCount = cpu_to_le16(1);
+		/* structure is big enough for 3 dialects, sending only 1 */
+		inbuflen = sizeof(struct validate_negotiate_info_req) - 4;
+	}
 
 	rc = SMB2_ioctl(xid, tcon, NO_FILE_ID, NO_FILE_ID,
 		FSCTL_VALIDATE_NEGOTIATE_INFO, true /* is_fsctl */,
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index 393ed5f..6c9653a 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -716,7 +716,7 @@ struct validate_negotiate_info_req {
 	__u8   Guid[SMB2_CLIENT_GUID_SIZE];
 	__le16 SecurityMode;
 	__le16 DialectCount;
-	__le16 Dialects[1]; /* dialect (someday maybe list) client asked for */
+	__le16 Dialects[3]; /* BB expand this if autonegotiate > 3 dialects */
 } __packed;
 
 struct validate_negotiate_info_rsp {
-- 
2.7.4

