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
Git-commit: 53d31a3ffd60176af24f2f77fb3a7e567134eb90
Patch-mainline: v5.14-rc1
References: bsc#1192606
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>
Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
---
fs/cifs/cifsfs.c | 4 +++
fs/cifs/cifsglob.h | 3 ++
fs/cifs/smb2pdu.c | 85 ++++++++++++++++++++++++++++++++++++++++------
fs/cifs/smb2pdu.h | 5 ++-
4 files changed, 86 insertions(+), 11 deletions(-)
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 9fb874dd8d24..64b71c4e2a9d 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_negotiate_signing, "Enable negotiating packet signing algorithm with server. 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..781d14e5f2af 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -433,6 +433,29 @@ build_compression_ctxt(struct smb2_compression_capabilities_context *pneg_ctxt)
pneg_ctxt->CompressionAlgorithms[2] = SMB3_COMPRESS_LZNT1;
}
+static unsigned int
+build_signing_ctxt(struct smb2_signing_capabilities *pneg_ctxt)
+{
+ unsigned int ctxt_len = sizeof(struct smb2_signing_capabilities);
+ unsigned short num_algs = 1; /* number of signing algorithms sent */
+
+ pneg_ctxt->ContextType = SMB2_SIGNING_CAPABILITIES;
+ /*
+ * 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) +
+ (num_algs * 2 /* sizeof u16 */), 8) * 8);
+ pneg_ctxt->SigningAlgorithmCount = cpu_to_le16(num_algs);
+ pneg_ctxt->SigningAlgorithms[0] = cpu_to_le16(SIGNING_ALG_AES_CMAC);
+
+ ctxt_len += 2 /* sizeof le16 */ * num_algs;
+ ctxt_len = DIV_ROUND_UP(ctxt_len, 8) * 8;
+ return ctxt_len;
+ /* 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 +521,7 @@ 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 +548,17 @@ 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 +567,20 @@ 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) {
+ ctxt_len = build_signing_ctxt((struct smb2_signing_capabilities *)
+ pneg_ctxt);
+ *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 +669,31 @@ 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 +737,9 @@ 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
--
2.33.1