v3 of patch. Updated with additional feedback from Ronnie (to make it
more context len and datalength clearer)
On Wed, Jul 7, 2021 at 9:44 PM Steve French <smfrench@xxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx>
> Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
> ---
> 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
--
Thanks,
Steve
From 387c856bf8b8098c2d8750376dcde289f5952ee7 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@xxxxxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
---
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..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..2258ff413204 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -433,6 +433,28 @@ 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);
+
+ 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) +
+ (2 /* sizeof u16 */ * 1 /* SigningAlgorithmCount */), 8) * 8);
+ pneg_ctxt->SigningAlgorithmCount = cpu_to_le16(1);
+ pneg_ctxt->SigningAlgorithms[0] = cpu_to_le16(SIGNING_ALG_AES_CMAC);
+
+ ctxt_len += 2 /* sizeof u16 */ * 1 /* SigningAlgorithmCount */;
+ 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 +520,7 @@ 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 +547,17 @@ 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 +566,21 @@ 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");
+ 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
--
2.30.2
