[PATCH][SMB3.1.1] add ability to send signing negotiate context

[Steve French <smfrench@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 8807 bytes --]

Support for faster packet signing (using GMAC instead of CMAC) can
now be negotiated to some newer servers, including Windows.
See MS-SMB2 section 2.2.3.17.

This patch adds support for sending the new negotiate context
with the first of three supported signing algorithms (AES-CMAC)
and decoding the response.  A followon patch will add support
for sending the other two (including AES-GMAC, which is fastest)
and changing the signing algorithm used based on what was
negotiated.

To allow the client to request GMAC signing set module parameter
"enable_negotiate_signing" to 1.

Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/cifs/cifsfs.c   |  4 +++
 fs/cifs/cifsglob.h |  3 ++
 fs/cifs/smb2pdu.c  | 83 ++++++++++++++++++++++++++++++++++++++++------
 fs/cifs/smb2pdu.h  |  5 ++-
 4 files changed, 84 insertions(+), 11 deletions(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 9fb874dd8d24..476b07213fcd 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -65,6 +65,7 @@ bool lookupCacheEnabled = true;
 bool disable_legacy_dialects; /* false by default */
 bool enable_gcm_256 = true;
 bool require_gcm_256; /* false by default */
+bool enable_negotiate_signing; /* false by default */
 unsigned int global_secflags = CIFSSEC_DEF;
 /* unsigned int ntlmv2_support = 0; */
 unsigned int sign_CIFS_PDUs = 1;
@@ -104,6 +105,9 @@ MODULE_PARM_DESC(enable_gcm_256, "Enable
requesting strongest (256 bit) GCM encr
 module_param(require_gcm_256, bool, 0644);
 MODULE_PARM_DESC(require_gcm_256, "Require strongest (256 bit) GCM
encryption. Default: n/N/0");

+module_param(enable_negotiate_signing, bool, 0644);
+MODULE_PARM_DESC(enable_GMAC_signing, "Enable requesting faster
(GMAC) packet signing. Default: n/N/0");
+
 module_param(disable_legacy_dialects, bool, 0644);
 MODULE_PARM_DESC(disable_legacy_dialects, "To improve security it may be "
    "helpful to restrict the ability to "
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 921680fb7931..3c2e117bb926 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -667,9 +667,11 @@ struct TCP_Server_Info {
  unsigned int max_write;
  unsigned int min_offload;
  __le16 compress_algorithm;
+ __u16 signing_algorithm;
  __le16 cipher_type;
  /* save initital negprot hash */
  __u8 preauth_sha_hash[SMB2_PREAUTH_HASH_SIZE];
+ bool signing_negotiated; /* true if valid signing context rcvd from server */
  bool posix_ext_supported;
  struct delayed_work reconnect; /* reconnect workqueue job */
  struct mutex reconnect_mutex; /* prevent simultaneous reconnects */
@@ -1869,6 +1871,7 @@ extern unsigned int global_secflags; /* if on,
session setup sent
 extern unsigned int sign_CIFS_PDUs;  /* enable smb packet signing */
 extern bool enable_gcm_256; /* allow optional negotiate of strongest
signing (aes-gcm-256) */
 extern bool require_gcm_256; /* require use of strongest signing
(aes-gcm-256) */
+extern bool enable_negotiate_signing; /* request use of faster (GMAC)
signing if available */
 extern bool linuxExtEnabled;/*enable Linux/Unix CIFS extensions*/
 extern unsigned int CIFSMaxBufSize;  /* max size not including hdr */
 extern unsigned int cifs_min_rcv;    /* min size of big ntwrk buf pool */
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 962826dc3316..757f145e70e5 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -433,6 +433,23 @@ build_compression_ctxt(struct
smb2_compression_capabilities_context *pneg_ctxt)
  pneg_ctxt->CompressionAlgorithms[2] = SMB3_COMPRESS_LZNT1;
 }

+static void
+build_signing_ctxt(struct smb2_signing_capabilities *pneg_ctxt)
+{
+ pneg_ctxt->ContextType = SMB2_SIGNING_CAPABILITIES;
+ /*
+ * Data length must be increased here if more than 3 signing algorithms
+ * sent but currently only 3 are defined. And context Data length must
+ * be rounded to multiple of 8 for some servers.
+ */
+ pneg_ctxt->DataLength =
+ cpu_to_le16(DIV_ROUND_UP(sizeof(struct smb2_signing_capabilities) -
+ sizeof(struct smb2_neg_context), 8) * 8);
+ pneg_ctxt->SigningAlgorithmCount = cpu_to_le16(1);
+ pneg_ctxt->SigningAlgorithms[0] = cpu_to_le16(SIGNING_ALG_AES_CMAC);
+ /* TBD add SIGNING_ALG_AES_GMAC and/or SIGNING_ALG_HMAC_SHA256 */
+}
+
 static void
 build_encrypt_ctxt(struct smb2_encryption_neg_context *pneg_ctxt)
 {
@@ -498,7 +515,7 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
        struct TCP_Server_Info *server, unsigned int *total_len)
 {
  char *pneg_ctxt;
- unsigned int ctxt_len;
+ unsigned int ctxt_len, neg_context_count;

  if (*total_len > 200) {
  /* In case length corrupted don't want to overrun smb buffer */
@@ -525,6 +542,17 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
  *total_len += ctxt_len;
  pneg_ctxt += ctxt_len;

+ ctxt_len = build_netname_ctxt((struct smb2_netname_neg_context *)pneg_ctxt,
+ server->hostname);
+ *total_len += ctxt_len;
+ pneg_ctxt += ctxt_len;
+
+ build_posix_ctxt((struct smb2_posix_neg_context *)pneg_ctxt);
+ *total_len += sizeof(struct smb2_posix_neg_context);
+ pneg_ctxt += sizeof(struct smb2_posix_neg_context);
+
+ neg_context_count = 4;
+
  if (server->compress_algorithm) {
  build_compression_ctxt((struct smb2_compression_capabilities_context *)
  pneg_ctxt);
@@ -533,17 +561,24 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
  8) * 8;
  *total_len += ctxt_len;
  pneg_ctxt += ctxt_len;
- req->NegotiateContextCount = cpu_to_le16(5);
- } else
- req->NegotiateContextCount = cpu_to_le16(4);
+ neg_context_count++;
+ }

- ctxt_len = build_netname_ctxt((struct smb2_netname_neg_context *)pneg_ctxt,
- server->hostname);
- *total_len += ctxt_len;
- pneg_ctxt += ctxt_len;
+ if (enable_negotiate_signing) {
+ pr_warn_once("requesting GMAC signing is experimental\n");
+ build_signing_ctxt((struct smb2_signing_capabilities *)
+ pneg_ctxt);
+ ctxt_len = DIV_ROUND_UP(
+ sizeof(struct smb2_signing_capabilities),
+ 8) * 8;
+ *total_len += ctxt_len;
+ pneg_ctxt += ctxt_len;
+ neg_context_count++;
+ }
+
+ /* check for and add transport_capabilities and signing capabilities */
+ req->NegotiateContextCount = cpu_to_le16(neg_context_count);

- build_posix_ctxt((struct smb2_posix_neg_context *)pneg_ctxt);
- *total_len += sizeof(struct smb2_posix_neg_context);
 }

 static void decode_preauth_context(struct smb2_preauth_neg_context *ctxt)
@@ -632,6 +667,31 @@ static int decode_encrypt_ctx(struct
TCP_Server_Info *server,
  return 0;
 }

+static void decode_signing_ctx(struct TCP_Server_Info *server,
+        struct smb2_signing_capabilities *pctxt)
+{
+ unsigned int len = le16_to_cpu(pctxt->DataLength);
+
+ if ((len < 4) || (len > 16)) {
+ pr_warn_once("server sent bad signing negcontext\n");
+ return;
+ }
+ if (le16_to_cpu(pctxt->SigningAlgorithmCount) != 1) {
+ pr_warn_once("Invalid signing algorithm count\n");
+ return;
+ }
+ if (le16_to_cpu(pctxt->SigningAlgorithms[0]) > 2) {
+ pr_warn_once("unknown signing algorithm\n");
+ return;
+ }
+
+ server->signing_negotiated = true;
+ server->signing_algorithm = le16_to_cpu(pctxt->SigningAlgorithms[0]);
+ cifs_dbg(FYI, "signing algorithm %d chosen\n",
+      server->signing_algorithm);
+}
+
+
 static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp,
       struct TCP_Server_Info *server,
       unsigned int len_of_smb)
@@ -675,6 +735,9 @@ static int smb311_decode_neg_context(struct
smb2_negotiate_rsp *rsp,
  (struct smb2_compression_capabilities_context *)pctx);
  else if (pctx->ContextType == SMB2_POSIX_EXTENSIONS_AVAILABLE)
  server->posix_ext_supported = true;
+ else if (pctx->ContextType == SMB2_SIGNING_CAPABILITIES)
+ decode_signing_ctx(server,
+ (struct smb2_signing_capabilities *)pctx);
  else
  cifs_server_dbg(VFS, "unknown negcontext of type %d ignored\n",
  le16_to_cpu(pctx->ContextType));
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index ba75e65924ac..4b27cb9105fd 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -329,7 +329,7 @@ struct smb2_neg_context {
  __le16 ContextType;
  __le16 DataLength;
  __le32 Reserved;
- /* Followed by array of data */
+ /* Followed by array of data. NOTE: some servers require padding to
8 byte boundary */
 } __packed;

 #define SMB311_LINUX_CLIENT_SALT_SIZE 32
@@ -394,6 +394,7 @@ struct smb2_compression_capabilities_context {
  __u16 Padding;
  __u32 Flags;
  __le16 CompressionAlgorithms[3];
+ /* Check if pad needed */
 } __packed;

 /*
@@ -420,6 +421,7 @@ struct smb2_transport_capabilities_context {
  __le16  DataLength;
  __u32 Reserved;
  __le32 Flags;
+ __u32 Pad;
 } __packed;

 /*
@@ -458,6 +460,7 @@ struct smb2_signing_capabilities {
  __u32 Reserved;
  __le16 SigningAlgorithmCount;
  __le16 SigningAlgorithms[];
+ /*  Followed by padding to 8 byte boundary (required by some servers) */
 } __packed;

 #define POSIX_CTXT_DATA_LEN 16

-- 
Thanks,

Steve

[-- Attachment #2: 0001-SMB3.1.1-Add-support-for-negotiating-signing-algorit.patch --]
[-- Type: text/x-patch, Size: 9121 bytes --]

From 8b55a00636ba7e1be8c1659df939b6e3cb53abe2 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Mon, 5 Jul 2021 15:05:39 -0500
Subject: [PATCH] SMB3.1.1: Add support for negotiating signing algorithm

Support for faster packet signing (using GMAC instead of CMAC) can
now be negotiated to some newer servers, including Windows.
See MS-SMB2 section 2.2.3.17.

This patch adds support for sending the new negotiate context
with the first of three supported signing algorithms (AES-CMAC)
and decoding the response.  A followon patch will add support
for sending the other two (including AES-GMAC, which is fastest)
and changing the signing algorithm used based on what was
negotiated.

To allow the client to request GMAC signing set module parameter
"enable_negotiate_signing" to 1.

Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/cifs/cifsfs.c   |  4 +++
 fs/cifs/cifsglob.h |  3 ++
 fs/cifs/smb2pdu.c  | 83 ++++++++++++++++++++++++++++++++++++++++------
 fs/cifs/smb2pdu.h  |  5 ++-
 4 files changed, 84 insertions(+), 11 deletions(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 9fb874dd8d24..476b07213fcd 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -65,6 +65,7 @@ bool lookupCacheEnabled = true;
 bool disable_legacy_dialects; /* false by default */
 bool enable_gcm_256 = true;
 bool require_gcm_256; /* false by default */
+bool enable_negotiate_signing; /* false by default */
 unsigned int global_secflags = CIFSSEC_DEF;
 /* unsigned int ntlmv2_support = 0; */
 unsigned int sign_CIFS_PDUs = 1;
@@ -104,6 +105,9 @@ MODULE_PARM_DESC(enable_gcm_256, "Enable requesting strongest (256 bit) GCM encr
 module_param(require_gcm_256, bool, 0644);
 MODULE_PARM_DESC(require_gcm_256, "Require strongest (256 bit) GCM encryption. Default: n/N/0");
 
+module_param(enable_negotiate_signing, bool, 0644);
+MODULE_PARM_DESC(enable_GMAC_signing, "Enable requesting faster (GMAC) packet signing. Default: n/N/0");
+
 module_param(disable_legacy_dialects, bool, 0644);
 MODULE_PARM_DESC(disable_legacy_dialects, "To improve security it may be "
 				  "helpful to restrict the ability to "
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 921680fb7931..3c2e117bb926 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -667,9 +667,11 @@ struct TCP_Server_Info {
 	unsigned int	max_write;
 	unsigned int	min_offload;
 	__le16	compress_algorithm;
+	__u16	signing_algorithm;
 	__le16	cipher_type;
 	 /* save initital negprot hash */
 	__u8	preauth_sha_hash[SMB2_PREAUTH_HASH_SIZE];
+	bool	signing_negotiated; /* true if valid signing context rcvd from server */
 	bool	posix_ext_supported;
 	struct delayed_work reconnect; /* reconnect workqueue job */
 	struct mutex reconnect_mutex; /* prevent simultaneous reconnects */
@@ -1869,6 +1871,7 @@ extern unsigned int global_secflags;	/* if on, session setup sent
 extern unsigned int sign_CIFS_PDUs;  /* enable smb packet signing */
 extern bool enable_gcm_256; /* allow optional negotiate of strongest signing (aes-gcm-256) */
 extern bool require_gcm_256; /* require use of strongest signing (aes-gcm-256) */
+extern bool enable_negotiate_signing; /* request use of faster (GMAC) signing if available */
 extern bool linuxExtEnabled;/*enable Linux/Unix CIFS extensions*/
 extern unsigned int CIFSMaxBufSize;  /* max size not including hdr */
 extern unsigned int cifs_min_rcv;    /* min size of big ntwrk buf pool */
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 962826dc3316..757f145e70e5 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -433,6 +433,23 @@ build_compression_ctxt(struct smb2_compression_capabilities_context *pneg_ctxt)
 	pneg_ctxt->CompressionAlgorithms[2] = SMB3_COMPRESS_LZNT1;
 }
 
+static void
+build_signing_ctxt(struct smb2_signing_capabilities *pneg_ctxt)
+{
+	pneg_ctxt->ContextType = SMB2_SIGNING_CAPABILITIES;
+	/*
+	 * Data length must be increased here if more than 3 signing algorithms
+	 * sent but currently only 3 are defined. And context Data length must
+	 * be rounded to multiple of 8 for some servers.
+	 */
+	pneg_ctxt->DataLength =
+		cpu_to_le16(DIV_ROUND_UP(sizeof(struct smb2_signing_capabilities) -
+					sizeof(struct smb2_neg_context), 8) * 8);
+	pneg_ctxt->SigningAlgorithmCount = cpu_to_le16(1);
+	pneg_ctxt->SigningAlgorithms[0] = cpu_to_le16(SIGNING_ALG_AES_CMAC);
+	/* TBD add SIGNING_ALG_AES_GMAC and/or SIGNING_ALG_HMAC_SHA256 */
+}
+
 static void
 build_encrypt_ctxt(struct smb2_encryption_neg_context *pneg_ctxt)
 {
@@ -498,7 +515,7 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
 		      struct TCP_Server_Info *server, unsigned int *total_len)
 {
 	char *pneg_ctxt;
-	unsigned int ctxt_len;
+	unsigned int ctxt_len, neg_context_count;
 
 	if (*total_len > 200) {
 		/* In case length corrupted don't want to overrun smb buffer */
@@ -525,6 +542,17 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
 	*total_len += ctxt_len;
 	pneg_ctxt += ctxt_len;
 
+	ctxt_len = build_netname_ctxt((struct smb2_netname_neg_context *)pneg_ctxt,
+					server->hostname);
+	*total_len += ctxt_len;
+	pneg_ctxt += ctxt_len;
+
+	build_posix_ctxt((struct smb2_posix_neg_context *)pneg_ctxt);
+	*total_len += sizeof(struct smb2_posix_neg_context);
+	pneg_ctxt += sizeof(struct smb2_posix_neg_context);
+
+	neg_context_count = 4;
+
 	if (server->compress_algorithm) {
 		build_compression_ctxt((struct smb2_compression_capabilities_context *)
 				pneg_ctxt);
@@ -533,17 +561,24 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
 				8) * 8;
 		*total_len += ctxt_len;
 		pneg_ctxt += ctxt_len;
-		req->NegotiateContextCount = cpu_to_le16(5);
-	} else
-		req->NegotiateContextCount = cpu_to_le16(4);
+		neg_context_count++;
+	}
 
-	ctxt_len = build_netname_ctxt((struct smb2_netname_neg_context *)pneg_ctxt,
-					server->hostname);
-	*total_len += ctxt_len;
-	pneg_ctxt += ctxt_len;
+	if (enable_negotiate_signing) {
+		pr_warn_once("requesting GMAC signing is experimental\n");
+		build_signing_ctxt((struct smb2_signing_capabilities *)
+				pneg_ctxt);
+		ctxt_len = DIV_ROUND_UP(
+			sizeof(struct smb2_signing_capabilities),
+				8) * 8;
+		*total_len += ctxt_len;
+		pneg_ctxt += ctxt_len;
+		neg_context_count++;
+	}
+
+	/* check for and add transport_capabilities and signing capabilities */
+	req->NegotiateContextCount = cpu_to_le16(neg_context_count);
 
-	build_posix_ctxt((struct smb2_posix_neg_context *)pneg_ctxt);
-	*total_len += sizeof(struct smb2_posix_neg_context);
 }
 
 static void decode_preauth_context(struct smb2_preauth_neg_context *ctxt)
@@ -632,6 +667,31 @@ static int decode_encrypt_ctx(struct TCP_Server_Info *server,
 	return 0;
 }
 
+static void decode_signing_ctx(struct TCP_Server_Info *server,
+			       struct smb2_signing_capabilities *pctxt)
+{
+	unsigned int len = le16_to_cpu(pctxt->DataLength);
+
+	if ((len < 4) || (len > 16)) {
+		pr_warn_once("server sent bad signing negcontext\n");
+		return;
+	}
+	if (le16_to_cpu(pctxt->SigningAlgorithmCount) != 1) {
+		pr_warn_once("Invalid signing algorithm count\n");
+		return;
+	}
+	if (le16_to_cpu(pctxt->SigningAlgorithms[0]) > 2) {
+		pr_warn_once("unknown signing algorithm\n");
+		return;
+	}
+
+	server->signing_negotiated = true;
+	server->signing_algorithm = le16_to_cpu(pctxt->SigningAlgorithms[0]);
+	cifs_dbg(FYI, "signing algorithm %d chosen\n",
+		     server->signing_algorithm);
+}
+
+
 static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp,
 				     struct TCP_Server_Info *server,
 				     unsigned int len_of_smb)
@@ -675,6 +735,9 @@ static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp,
 				(struct smb2_compression_capabilities_context *)pctx);
 		else if (pctx->ContextType == SMB2_POSIX_EXTENSIONS_AVAILABLE)
 			server->posix_ext_supported = true;
+		else if (pctx->ContextType == SMB2_SIGNING_CAPABILITIES)
+			decode_signing_ctx(server,
+				(struct smb2_signing_capabilities *)pctx);
 		else
 			cifs_server_dbg(VFS, "unknown negcontext of type %d ignored\n",
 				le16_to_cpu(pctx->ContextType));
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index ba75e65924ac..4b27cb9105fd 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -329,7 +329,7 @@ struct smb2_neg_context {
 	__le16	ContextType;
 	__le16	DataLength;
 	__le32	Reserved;
-	/* Followed by array of data */
+	/* Followed by array of data. NOTE: some servers require padding to 8 byte boundary */
 } __packed;
 
 #define SMB311_LINUX_CLIENT_SALT_SIZE			32
@@ -394,6 +394,7 @@ struct smb2_compression_capabilities_context {
 	__u16	Padding;
 	__u32	Flags;
 	__le16	CompressionAlgorithms[3];
+	/* Check if pad needed */
 } __packed;
 
 /*
@@ -420,6 +421,7 @@ struct smb2_transport_capabilities_context {
 	__le16  DataLength;
 	__u32	Reserved;
 	__le32	Flags;
+	__u32	Pad;
 } __packed;
 
 /*
@@ -458,6 +460,7 @@ struct smb2_signing_capabilities {
 	__u32	Reserved;
 	__le16	SigningAlgorithmCount;
 	__le16	SigningAlgorithms[];
+	/*  Followed by padding to 8 byte boundary (required by some servers) */
 } __packed;
 
 #define POSIX_CTXT_DATA_LEN	16
-- 
2.30.2