diff mbox series

[v2] cifs: decoding negTokenInit with generic ASN1 decoder

Message ID 20210521020051.196434-1-hyc.lee@gmail.com (mailing list archive)
State New, archived
Headers show
Series [v2] cifs: decoding negTokenInit with generic ASN1 decoder | expand

Commit Message

Hyunchul Lee May 21, 2021, 2 a.m. UTC
Decode negTokenInit with lib/asn1_decoder. For that,
add OIDs in linux/oid_registry.h and a negTokenInit
ASN1 file, "spnego_negtokeninit.asn1".
And define decoder's callback functions, which
are the gssapi_this_mech for checking SPENGO oid and
the neg_token_init_mech_type for getting authentication
mechanisms supported by a server.

Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
---
changes from v1:
 - Select CONFIG_OID_REGISTRY

 fs/cifs/Kconfig                  |   2 +
 fs/cifs/Makefile                 |   4 +-
 fs/cifs/asn1.c                   | 624 ++-----------------------------
 fs/cifs/spnego_negtokeninit.asn1 |  40 ++
 include/linux/oid_registry.h     |   8 +
 5 files changed, 90 insertions(+), 588 deletions(-)
 create mode 100644 fs/cifs/spnego_negtokeninit.asn1

Comments

Aurélien Aptel May 21, 2021, 8:43 a.m. UTC | #1
Hi Hyunchul,

The existence of multiple ASN1 decoder has been a regular complaint,
this looks nice. Have you tested it against any servers?

I think we need to make sure it works with Windows Server (including
increased ones with the increased security flag, Steve do you remember
the name of that flag?) and Samba at least.

There is the SDC EMEA plugfest coming up, might be a good time to try it
out against other vendors as well.

Cheers,
Hyunchul Lee May 22, 2021, 2:17 p.m. UTC | #2
Hi Aurélien,

2021년 5월 21일 (금) 오후 5:43, Aurélien Aptel <aaptel@suse.com>님이 작성:
>
> Hi Hyunchul,
>
> The existence of multiple ASN1 decoder has been a regular complaint,
> this looks nice. Have you tested it against any servers?
>

Yes, I have tested this patch against Windows 10, Samba 4.11.6, and cifsd.
If you have trouble,  you need to rebuild the kernel due to rebuilding
the OID registry.

> I think we need to make sure it works with Windows Server (including
> increased ones with the increased security flag, Steve do you remember
> the name of that flag?) and Samba at least.
>

If you let me know the option, I will try.

> There is the SDC EMEA plugfest coming up, might be a good time to try it
> out against other vendors as well.
>

Yes, but I am not gonna to attend the plugfest because of personal reasons.
Is there any other way to test this against other vendors?

Thanks,
Hyunchul

> Cheers,
> --
> Aurélien Aptel / SUSE Labs Samba Team
> GPG: 1839 CB5F 9F5B FB9B AA97  8C99 03C8 A49B 521B D5D3
> SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
> GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)
>
kernel test robot May 22, 2021, 8:12 p.m. UTC | #3
Hi Hyunchul,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on cifs/for-next]
[also build test WARNING on linux/master linus/master v5.13-rc2 next-20210521]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Hyunchul-Lee/cifs-decoding-negTokenInit-with-generic-ASN1-decoder/20210522-232614
base:   git://git.samba.org/sfrench/cifs-2.6.git for-next
config: i386-defconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/e1097df7e174530fece6a8afc49d61d34b904869
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Hyunchul-Lee/cifs-decoding-negTokenInit-with-generic-ASN1-decoder/20210522-232614
        git checkout e1097df7e174530fece6a8afc49d61d34b904869
        # save the attached .config to linux build tree
        make W=1 ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> fs/cifs/asn1.c:11:1: warning: no previous prototype for 'decode_negTokenInit' [-Wmissing-prototypes]
      11 | decode_negTokenInit(unsigned char *security_blob, int length,
         | ^~~~~~~~~~~~~~~~~~~


vim +/decode_negTokenInit +11 fs/cifs/asn1.c

     9	
    10	int
  > 11	decode_negTokenInit(unsigned char *security_blob, int length,
    12			    struct TCP_Server_Info *server)
    13	{
    14		if (asn1_ber_decoder(&spnego_negtokeninit_decoder, server,
    15				     security_blob, length) == 0)
    16			return 1;
    17		else
    18			return 0;
    19	}
    20	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
kernel test robot May 22, 2021, 9:47 p.m. UTC | #4
Hi Hyunchul,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on cifs/for-next]
[also build test ERROR on linux/master linus/master v5.13-rc2 next-20210521]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Hyunchul-Lee/cifs-decoding-negTokenInit-with-generic-ASN1-decoder/20210522-232614
base:   git://git.samba.org/sfrench/cifs-2.6.git for-next
config: um-allmodconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/e1097df7e174530fece6a8afc49d61d34b904869
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Hyunchul-Lee/cifs-decoding-negTokenInit-with-generic-ASN1-decoder/20210522-232614
        git checkout e1097df7e174530fece6a8afc49d61d34b904869
        # save the attached .config to linux build tree
        make W=1 ARCH=um 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> fs/cifs/asn1.c:8:10: fatal error: spnego_negtokeninit.asn1.h: No such file or directory
       8 | #include "spnego_negtokeninit.asn1.h"
         |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
   compilation terminated.


vim +8 fs/cifs/asn1.c

     2	
     3	#include <linux/module.h>
     4	#include <linux/kernel.h>
     5	#include <linux/oid_registry.h>
     6	#include "cifsglob.h"
     7	#include "cifs_debug.h"
   > 8	#include "spnego_negtokeninit.asn1.h"
     9	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Steve French May 23, 2021, 2:36 a.m. UTC | #5
On Fri, May 21, 2021 at 3:44 AM Aurélien Aptel via samba-technical
<samba-technical@lists.samba.org> wrote:
>
> Hi Hyunchul,
>
> The existence of multiple ASN1 decoder has been a regular complaint,
> this looks nice. Have you tested it against any servers?
>
> I think we need to make sure it works with Windows Server (including
> increased ones with the increased security flag, Steve do you remember
> the name of that flag?) and Samba at least.

Are you thinking about the authentication problem to Windows when a
stricter registry setting is chosen for server name hardening?

This involves populating the ntlmv2 response area of an NTLMSSP blob
with the  "Target Name" attribute ie missing MsvAvTargetNamefield and
maybe also
MsvAvTimestamp and NTLMSSP_AVFLAG_MIC_IN_AUTHENTICATE_MESSAGE in
MsvAvFlags.   These (the target name field in particular) are required
when Windows servers set the registry parm SmbServerNameHardeningLevel
to 2

See e.g. https://docs.microsoft.com/en-us/windows/security/threat-protection/security-policy-settings/microsoft-network-server-server-spn-target-name-validation-level

> There is the SDC EMEA plugfest coming up, might be a good time to try it
> out against other vendors as well.

Yes - definitely need to try with various cases (krb5 and ntlmssp in
SPNEGO) to various servers (Macs, NetApp, Windows, Azure, Samba,ksmbd
etc)
diff mbox series

Patch

diff --git a/fs/cifs/Kconfig b/fs/cifs/Kconfig
index bf52e9326ebe..7de5c893c181 100644
--- a/fs/cifs/Kconfig
+++ b/fs/cifs/Kconfig
@@ -19,6 +19,8 @@  config CIFS
 	select CRYPTO_LIB_DES
 	select KEYS
 	select DNS_RESOLVER
+	select ASN1
+	select OID_REGISTRY
 	help
 	  This is the client VFS module for the SMB3 family of NAS protocols,
 	  (including support for the most recent, most secure dialect SMB3.1.1)
diff --git a/fs/cifs/Makefile b/fs/cifs/Makefile
index 3ee3b7de4ded..f12c1a3abd44 100644
--- a/fs/cifs/Makefile
+++ b/fs/cifs/Makefile
@@ -5,13 +5,15 @@ 
 ccflags-y += -I$(src)		# needed for trace events
 obj-$(CONFIG_CIFS) += cifs.o
 
+$(obj)/spnego_negtokeninit.asn1.o: $(obj)/spnego_negtokeninit.asn1.c $(obj)/spnego_negtokeninit.asn1.h
+
 cifs-y := trace.o cifsfs.o cifssmb.o cifs_debug.o connect.o dir.o file.o \
 	  inode.o link.o misc.o netmisc.o smbencrypt.o transport.o asn1.o \
 	  cifs_unicode.o nterr.o cifsencrypt.o \
 	  readdir.o ioctl.o sess.o export.o smb1ops.o unc.o winucase.o \
 	  smb2ops.o smb2maperror.o smb2transport.o \
 	  smb2misc.o smb2pdu.o smb2inode.o smb2file.o cifsacl.o fs_context.o \
-	  dns_resolve.o
+	  dns_resolve.o spnego_negtokeninit.asn1.o
 
 cifs-$(CONFIG_CIFS_XATTR) += xattr.o
 
diff --git a/fs/cifs/asn1.c b/fs/cifs/asn1.c
index 3150c19cdc2f..69a31d6b5fd9 100644
--- a/fs/cifs/asn1.c
+++ b/fs/cifs/asn1.c
@@ -1,612 +1,62 @@ 
 // SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * The ASB.1/BER parsing code is derived from ip_nat_snmp_basic.c which was in
- * turn derived from the gxsnmp package by Gregory McLean & Jochen Friedrich
- *
- * Copyright (c) 2000 RP Internet (www.rpi.net.au).
- */
 
 #include <linux/module.h>
-#include <linux/types.h>
 #include <linux/kernel.h>
-#include <linux/mm.h>
-#include <linux/slab.h>
-#include "cifspdu.h"
+#include <linux/oid_registry.h>
 #include "cifsglob.h"
 #include "cifs_debug.h"
-#include "cifsproto.h"
+#include "spnego_negtokeninit.asn1.h"
 
-/*****************************************************************************
- *
- * Basic ASN.1 decoding routines (gxsnmp author Dirk Wisse)
- *
- *****************************************************************************/
-
-/* Class */
-#define ASN1_UNI	0	/* Universal */
-#define ASN1_APL	1	/* Application */
-#define ASN1_CTX	2	/* Context */
-#define ASN1_PRV	3	/* Private */
-
-/* Tag */
-#define ASN1_EOC	0	/* End Of Contents or N/A */
-#define ASN1_BOL	1	/* Boolean */
-#define ASN1_INT	2	/* Integer */
-#define ASN1_BTS	3	/* Bit String */
-#define ASN1_OTS	4	/* Octet String */
-#define ASN1_NUL	5	/* Null */
-#define ASN1_OJI	6	/* Object Identifier  */
-#define ASN1_OJD	7	/* Object Description */
-#define ASN1_EXT	8	/* External */
-#define ASN1_ENUM	10	/* Enumerated */
-#define ASN1_SEQ	16	/* Sequence */
-#define ASN1_SET	17	/* Set */
-#define ASN1_NUMSTR	18	/* Numerical String */
-#define ASN1_PRNSTR	19	/* Printable String */
-#define ASN1_TEXSTR	20	/* Teletext String */
-#define ASN1_VIDSTR	21	/* Video String */
-#define ASN1_IA5STR	22	/* IA5 String */
-#define ASN1_UNITIM	23	/* Universal Time */
-#define ASN1_GENTIM	24	/* General Time */
-#define ASN1_GRASTR	25	/* Graphical String */
-#define ASN1_VISSTR	26	/* Visible String */
-#define ASN1_GENSTR	27	/* General String */
-
-/* Primitive / Constructed methods*/
-#define ASN1_PRI	0	/* Primitive */
-#define ASN1_CON	1	/* Constructed */
-
-/*
- * Error codes.
- */
-#define ASN1_ERR_NOERROR		0
-#define ASN1_ERR_DEC_EMPTY		2
-#define ASN1_ERR_DEC_EOC_MISMATCH	3
-#define ASN1_ERR_DEC_LENGTH_MISMATCH	4
-#define ASN1_ERR_DEC_BADVALUE		5
-
-#define SPNEGO_OID_LEN 7
-#define NTLMSSP_OID_LEN  10
-#define KRB5_OID_LEN  7
-#define KRB5U2U_OID_LEN  8
-#define MSKRB5_OID_LEN  7
-static unsigned long SPNEGO_OID[7] = { 1, 3, 6, 1, 5, 5, 2 };
-static unsigned long NTLMSSP_OID[10] = { 1, 3, 6, 1, 4, 1, 311, 2, 2, 10 };
-static unsigned long KRB5_OID[7] = { 1, 2, 840, 113554, 1, 2, 2 };
-static unsigned long KRB5U2U_OID[8] = { 1, 2, 840, 113554, 1, 2, 2, 3 };
-static unsigned long MSKRB5_OID[7] = { 1, 2, 840, 48018, 1, 2, 2 };
-
-/*
- * ASN.1 context.
- */
-struct asn1_ctx {
-	int error;		/* Error condition */
-	unsigned char *pointer;	/* Octet just to be decoded */
-	unsigned char *begin;	/* First octet */
-	unsigned char *end;	/* Octet after last octet */
-};
-
-/*
- * Octet string (not null terminated)
- */
-struct asn1_octstr {
-	unsigned char *data;
-	unsigned int len;
-};
-
-static void
-asn1_open(struct asn1_ctx *ctx, unsigned char *buf, unsigned int len)
-{
-	ctx->begin = buf;
-	ctx->end = buf + len;
-	ctx->pointer = buf;
-	ctx->error = ASN1_ERR_NOERROR;
-}
-
-static unsigned char
-asn1_octet_decode(struct asn1_ctx *ctx, unsigned char *ch)
-{
-	if (ctx->pointer >= ctx->end) {
-		ctx->error = ASN1_ERR_DEC_EMPTY;
-		return 0;
-	}
-	*ch = *(ctx->pointer)++;
-	return 1;
-}
-
-#if 0 /* will be needed later by spnego decoding/encoding of ntlmssp */
-static unsigned char
-asn1_enum_decode(struct asn1_ctx *ctx, __le32 *val)
-{
-	unsigned char ch;
-
-	if (ctx->pointer >= ctx->end) {
-		ctx->error = ASN1_ERR_DEC_EMPTY;
-		return 0;
-	}
-
-	ch = *(ctx->pointer)++; /* ch has 0xa, ptr points to length octet */
-	if ((ch) == ASN1_ENUM)  /* if ch value is ENUM, 0xa */
-		*val = *(++(ctx->pointer)); /* value has enum value */
-	else
-		return 0;
-
-	ctx->pointer++;
-	return 1;
-}
-#endif
-
-static unsigned char
-asn1_tag_decode(struct asn1_ctx *ctx, unsigned int *tag)
-{
-	unsigned char ch;
-
-	*tag = 0;
-
-	do {
-		if (!asn1_octet_decode(ctx, &ch))
-			return 0;
-		*tag <<= 7;
-		*tag |= ch & 0x7F;
-	} while ((ch & 0x80) == 0x80);
-	return 1;
-}
-
-static unsigned char
-asn1_id_decode(struct asn1_ctx *ctx,
-	       unsigned int *cls, unsigned int *con, unsigned int *tag)
-{
-	unsigned char ch;
-
-	if (!asn1_octet_decode(ctx, &ch))
-		return 0;
-
-	*cls = (ch & 0xC0) >> 6;
-	*con = (ch & 0x20) >> 5;
-	*tag = (ch & 0x1F);
-
-	if (*tag == 0x1F) {
-		if (!asn1_tag_decode(ctx, tag))
-			return 0;
-	}
-	return 1;
-}
-
-static unsigned char
-asn1_length_decode(struct asn1_ctx *ctx, unsigned int *def, unsigned int *len)
-{
-	unsigned char ch, cnt;
-
-	if (!asn1_octet_decode(ctx, &ch))
-		return 0;
-
-	if (ch == 0x80)
-		*def = 0;
-	else {
-		*def = 1;
-
-		if (ch < 0x80)
-			*len = ch;
-		else {
-			cnt = (unsigned char) (ch & 0x7F);
-			*len = 0;
-
-			while (cnt > 0) {
-				if (!asn1_octet_decode(ctx, &ch))
-					return 0;
-				*len <<= 8;
-				*len |= ch;
-				cnt--;
-			}
-		}
-	}
-
-	/* don't trust len bigger than ctx buffer */
-	if (*len > ctx->end - ctx->pointer)
-		return 0;
-
-	return 1;
-}
-
-static unsigned char
-asn1_header_decode(struct asn1_ctx *ctx,
-		   unsigned char **eoc,
-		   unsigned int *cls, unsigned int *con, unsigned int *tag)
-{
-	unsigned int def = 0;
-	unsigned int len = 0;
-
-	if (!asn1_id_decode(ctx, cls, con, tag))
-		return 0;
-
-	if (!asn1_length_decode(ctx, &def, &len))
-		return 0;
-
-	/* primitive shall be definite, indefinite shall be constructed */
-	if (*con == ASN1_PRI && !def)
-		return 0;
-
-	if (def)
-		*eoc = ctx->pointer + len;
-	else
-		*eoc = NULL;
-	return 1;
-}
-
-static unsigned char
-asn1_eoc_decode(struct asn1_ctx *ctx, unsigned char *eoc)
+int
+decode_negTokenInit(unsigned char *security_blob, int length,
+		    struct TCP_Server_Info *server)
 {
-	unsigned char ch;
-
-	if (eoc == NULL) {
-		if (!asn1_octet_decode(ctx, &ch))
-			return 0;
-
-		if (ch != 0x00) {
-			ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
-			return 0;
-		}
-
-		if (!asn1_octet_decode(ctx, &ch))
-			return 0;
-
-		if (ch != 0x00) {
-			ctx->error = ASN1_ERR_DEC_EOC_MISMATCH;
-			return 0;
-		}
-		return 1;
-	} else {
-		if (ctx->pointer != eoc) {
-			ctx->error = ASN1_ERR_DEC_LENGTH_MISMATCH;
-			return 0;
-		}
+	if (asn1_ber_decoder(&spnego_negtokeninit_decoder, server,
+			     security_blob, length) == 0)
 		return 1;
-	}
-}
-
-/* static unsigned char asn1_null_decode(struct asn1_ctx *ctx,
-				      unsigned char *eoc)
-{
-	ctx->pointer = eoc;
-	return 1;
-}
-
-static unsigned char asn1_long_decode(struct asn1_ctx *ctx,
-				      unsigned char *eoc, long *integer)
-{
-	unsigned char ch;
-	unsigned int len;
-
-	if (!asn1_octet_decode(ctx, &ch))
-		return 0;
-
-	*integer = (signed char) ch;
-	len = 1;
-
-	while (ctx->pointer < eoc) {
-		if (++len > sizeof(long)) {
-			ctx->error = ASN1_ERR_DEC_BADVALUE;
-			return 0;
-		}
-
-		if (!asn1_octet_decode(ctx, &ch))
-			return 0;
-
-		*integer <<= 8;
-		*integer |= ch;
-	}
-	return 1;
-}
-
-static unsigned char asn1_uint_decode(struct asn1_ctx *ctx,
-				      unsigned char *eoc,
-				      unsigned int *integer)
-{
-	unsigned char ch;
-	unsigned int len;
-
-	if (!asn1_octet_decode(ctx, &ch))
-		return 0;
-
-	*integer = ch;
-	if (ch == 0)
-		len = 0;
 	else
-		len = 1;
-
-	while (ctx->pointer < eoc) {
-		if (++len > sizeof(unsigned int)) {
-			ctx->error = ASN1_ERR_DEC_BADVALUE;
-			return 0;
-		}
-
-		if (!asn1_octet_decode(ctx, &ch))
-			return 0;
-
-		*integer <<= 8;
-		*integer |= ch;
-	}
-	return 1;
-}
-
-static unsigned char asn1_ulong_decode(struct asn1_ctx *ctx,
-				       unsigned char *eoc,
-				       unsigned long *integer)
-{
-	unsigned char ch;
-	unsigned int len;
-
-	if (!asn1_octet_decode(ctx, &ch))
 		return 0;
-
-	*integer = ch;
-	if (ch == 0)
-		len = 0;
-	else
-		len = 1;
-
-	while (ctx->pointer < eoc) {
-		if (++len > sizeof(unsigned long)) {
-			ctx->error = ASN1_ERR_DEC_BADVALUE;
-			return 0;
-		}
-
-		if (!asn1_octet_decode(ctx, &ch))
-			return 0;
-
-		*integer <<= 8;
-		*integer |= ch;
-	}
-	return 1;
 }
 
-static unsigned char
-asn1_octets_decode(struct asn1_ctx *ctx,
-		   unsigned char *eoc,
-		   unsigned char **octets, unsigned int *len)
+int gssapi_this_mech(void *context, size_t hdrlen,
+		     unsigned char tag, const void *value, size_t vlen)
 {
-	unsigned char *ptr;
-
-	*len = 0;
-
-	*octets = kmalloc(eoc - ctx->pointer, GFP_ATOMIC);
-	if (*octets == NULL) {
-		return 0;
-	}
-
-	ptr = *octets;
-	while (ctx->pointer < eoc) {
-		if (!asn1_octet_decode(ctx, (unsigned char *) ptr++)) {
-			kfree(*octets);
-			*octets = NULL;
-			return 0;
-		}
-		(*len)++;
-	}
-	return 1;
-} */
-
-static unsigned char
-asn1_subid_decode(struct asn1_ctx *ctx, unsigned long *subid)
-{
-	unsigned char ch;
-
-	*subid = 0;
-
-	do {
-		if (!asn1_octet_decode(ctx, &ch))
-			return 0;
-
-		*subid <<= 7;
-		*subid |= ch & 0x7F;
-	} while ((ch & 0x80) == 0x80);
-	return 1;
-}
-
-static int
-asn1_oid_decode(struct asn1_ctx *ctx,
-		unsigned char *eoc, unsigned long **oid, unsigned int *len)
-{
-	unsigned long subid;
-	unsigned int size;
-	unsigned long *optr;
-
-	size = eoc - ctx->pointer + 1;
-
-	/* first subid actually encodes first two subids */
-	if (size < 2 || size > UINT_MAX/sizeof(unsigned long))
-		return 0;
-
-	*oid = kmalloc_array(size, sizeof(unsigned long), GFP_ATOMIC);
-	if (*oid == NULL)
-		return 0;
-
-	optr = *oid;
-
-	if (!asn1_subid_decode(ctx, &subid)) {
-		kfree(*oid);
-		*oid = NULL;
-		return 0;
-	}
-
-	if (subid < 40) {
-		optr[0] = 0;
-		optr[1] = subid;
-	} else if (subid < 80) {
-		optr[0] = 1;
-		optr[1] = subid - 40;
-	} else {
-		optr[0] = 2;
-		optr[1] = subid - 80;
-	}
-
-	*len = 2;
-	optr += 2;
+	enum OID oid;
 
-	while (ctx->pointer < eoc) {
-		if (++(*len) > size) {
-			ctx->error = ASN1_ERR_DEC_BADVALUE;
-			kfree(*oid);
-			*oid = NULL;
-			return 0;
-		}
+	oid = look_up_OID(value, vlen);
+	if (oid != OID_spnego) {
+		char buf[50];
 
-		if (!asn1_subid_decode(ctx, optr++)) {
-			kfree(*oid);
-			*oid = NULL;
-			return 0;
-		}
+		sprint_oid(value, vlen, buf, sizeof(buf));
+		cifs_dbg(FYI, "Error decoding negTokenInit header: unexpected OID %s\n",
+			 buf);
+		return -EBADMSG;
 	}
-	return 1;
+	return 0;
 }
 
-static int
-compare_oid(unsigned long *oid1, unsigned int oid1len,
-	    unsigned long *oid2, unsigned int oid2len)
+int neg_token_init_mech_type(void *context, size_t hdrlen,
+			     unsigned char tag,
+			     const void *value, size_t vlen)
 {
-	unsigned int i;
+	struct TCP_Server_Info *server = context;
+	enum OID oid;
 
-	if (oid1len != oid2len)
-		return 0;
+	oid = look_up_OID(value, vlen);
+	if (oid == OID_mskrb5)
+		server->sec_mskerberos = true;
+	else if (oid == OID_krb5u2u)
+		server->sec_kerberosu2u = true;
+	else if (oid == OID_krb5)
+		server->sec_kerberos = true;
+	else if (oid == OID_ntlmssp)
+		server->sec_ntlmssp = true;
 	else {
-		for (i = 0; i < oid1len; i++) {
-			if (oid1[i] != oid2[i])
-				return 0;
-		}
-		return 1;
-	}
-}
-
-	/* BB check for endian conversion issues here */
-
-int
-decode_negTokenInit(unsigned char *security_blob, int length,
-		    struct TCP_Server_Info *server)
-{
-	struct asn1_ctx ctx;
-	unsigned char *end;
-	unsigned char *sequence_end;
-	unsigned long *oid = NULL;
-	unsigned int cls, con, tag, oidlen, rc;
-
-	/* cifs_dump_mem(" Received SecBlob ", security_blob, length); */
-
-	asn1_open(&ctx, security_blob, length);
+		char buf[50];
 
-	/* GSSAPI header */
-	if (asn1_header_decode(&ctx, &end, &cls, &con, &tag) == 0) {
-		cifs_dbg(FYI, "Error decoding negTokenInit header\n");
-		return 0;
-	} else if ((cls != ASN1_APL) || (con != ASN1_CON)
-		   || (tag != ASN1_EOC)) {
-		cifs_dbg(FYI, "cls = %d con = %d tag = %d\n", cls, con, tag);
-		return 0;
+		sprint_oid(value, vlen, buf, sizeof(buf));
+		cifs_dbg(FYI, "Decoding negTokenInit: unsupported OID %s\n",
+			 buf);
 	}
-
-	/* Check for SPNEGO OID -- remember to free obj->oid */
-	rc = asn1_header_decode(&ctx, &end, &cls, &con, &tag);
-	if (rc) {
-		if ((tag == ASN1_OJI) && (con == ASN1_PRI) &&
-		    (cls == ASN1_UNI)) {
-			rc = asn1_oid_decode(&ctx, end, &oid, &oidlen);
-			if (rc) {
-				rc = compare_oid(oid, oidlen, SPNEGO_OID,
-						 SPNEGO_OID_LEN);
-				kfree(oid);
-			}
-		} else
-			rc = 0;
-	}
-
-	/* SPNEGO OID not present or garbled -- bail out */
-	if (!rc) {
-		cifs_dbg(FYI, "Error decoding negTokenInit header\n");
-		return 0;
-	}
-
-	/* SPNEGO */
-	if (asn1_header_decode(&ctx, &end, &cls, &con, &tag) == 0) {
-		cifs_dbg(FYI, "Error decoding negTokenInit\n");
-		return 0;
-	} else if ((cls != ASN1_CTX) || (con != ASN1_CON)
-		   || (tag != ASN1_EOC)) {
-		cifs_dbg(FYI, "cls = %d con = %d tag = %d end = %p exit 0\n",
-			 cls, con, tag, end);
-		return 0;
-	}
-
-	/* negTokenInit */
-	if (asn1_header_decode(&ctx, &end, &cls, &con, &tag) == 0) {
-		cifs_dbg(FYI, "Error decoding negTokenInit\n");
-		return 0;
-	} else if ((cls != ASN1_UNI) || (con != ASN1_CON)
-		   || (tag != ASN1_SEQ)) {
-		cifs_dbg(FYI, "cls = %d con = %d tag = %d end = %p exit 1\n",
-			 cls, con, tag, end);
-		return 0;
-	}
-
-	/* sequence */
-	if (asn1_header_decode(&ctx, &end, &cls, &con, &tag) == 0) {
-		cifs_dbg(FYI, "Error decoding 2nd part of negTokenInit\n");
-		return 0;
-	} else if ((cls != ASN1_CTX) || (con != ASN1_CON)
-		   || (tag != ASN1_EOC)) {
-		cifs_dbg(FYI, "cls = %d con = %d tag = %d end = %p exit 0\n",
-			 cls, con, tag, end);
-		return 0;
-	}
-
-	/* sequence of */
-	if (asn1_header_decode
-	    (&ctx, &sequence_end, &cls, &con, &tag) == 0) {
-		cifs_dbg(FYI, "Error decoding 2nd part of negTokenInit\n");
-		return 0;
-	} else if ((cls != ASN1_UNI) || (con != ASN1_CON)
-		   || (tag != ASN1_SEQ)) {
-		cifs_dbg(FYI, "cls = %d con = %d tag = %d sequence_end = %p exit 1\n",
-			 cls, con, tag, sequence_end);
-		return 0;
-	}
-
-	/* list of security mechanisms */
-	while (!asn1_eoc_decode(&ctx, sequence_end)) {
-		rc = asn1_header_decode(&ctx, &end, &cls, &con, &tag);
-		if (!rc) {
-			cifs_dbg(FYI, "Error decoding negTokenInit hdr exit2\n");
-			return 0;
-		}
-		if ((tag == ASN1_OJI) && (con == ASN1_PRI)) {
-			if (asn1_oid_decode(&ctx, end, &oid, &oidlen)) {
-
-				cifs_dbg(FYI, "OID len = %d oid = 0x%lx 0x%lx 0x%lx 0x%lx\n",
-					 oidlen, *oid, *(oid + 1), *(oid + 2),
-					 *(oid + 3));
-
-				if (compare_oid(oid, oidlen, MSKRB5_OID,
-						MSKRB5_OID_LEN))
-					server->sec_mskerberos = true;
-				else if (compare_oid(oid, oidlen, KRB5U2U_OID,
-						     KRB5U2U_OID_LEN))
-					server->sec_kerberosu2u = true;
-				else if (compare_oid(oid, oidlen, KRB5_OID,
-						     KRB5_OID_LEN))
-					server->sec_kerberos = true;
-				else if (compare_oid(oid, oidlen, NTLMSSP_OID,
-						     NTLMSSP_OID_LEN))
-					server->sec_ntlmssp = true;
-
-				kfree(oid);
-			}
-		} else {
-			cifs_dbg(FYI, "Should be an oid what is going on?\n");
-		}
-	}
-
-	/*
-	 * We currently ignore anything at the end of the SPNEGO blob after
-	 * the mechTypes have been parsed, since none of that info is
-	 * used at the moment.
-	 */
-	return 1;
+	return 0;
 }
diff --git a/fs/cifs/spnego_negtokeninit.asn1 b/fs/cifs/spnego_negtokeninit.asn1
new file mode 100644
index 000000000000..aa5b4a61b3f5
--- /dev/null
+++ b/fs/cifs/spnego_negtokeninit.asn1
@@ -0,0 +1,40 @@ 
+GSSAPI ::=
+	[APPLICATION 0] IMPLICIT SEQUENCE {
+		thisMech
+			OBJECT IDENTIFIER ({gssapi_this_mech}),
+		negotiationToken
+			NegotiationToken
+	}
+
+MechType ::= OBJECT IDENTIFIER ({neg_token_init_mech_type})
+
+MechTypeList ::= SEQUENCE OF MechType
+
+NegHints ::= SEQUENCE {
+	hintName
+		[0] GeneralString OPTIONAL,
+	hintAddress
+		[1] OCTET STRING OPTIONAL
+	}
+
+NegTokenInit2 ::=
+	SEQUENCE {
+		mechTypes
+			[0] MechTypeList OPTIONAL,
+		reqFlags
+			[1] BIT STRING OPTIONAL,
+		mechToken
+			[2] OCTET STRING OPTIONAL,
+		negHints
+			[3] NegHints OPTIONAL,
+		mechListMIC
+			[3] OCTET STRING OPTIONAL
+	}
+
+NegotiationToken ::=
+	CHOICE {
+		negTokenInit
+			[0] NegTokenInit2,
+		negTokenTarg
+			[1] ANY
+	}
diff --git a/include/linux/oid_registry.h b/include/linux/oid_registry.h
index 461b7aa587ba..3d8db1f6a5db 100644
--- a/include/linux/oid_registry.h
+++ b/include/linux/oid_registry.h
@@ -54,6 +54,10 @@  enum OID {
 	OID_md4,			/* 1.2.840.113549.2.4 */
 	OID_md5,			/* 1.2.840.113549.2.5 */
 
+	OID_mskrb5,			/* 1.2.840.48018.1.2.2 */
+	OID_krb5,			/* 1.2.840.113554.1.2.2 */
+	OID_krb5u2u,			/* 1.2.840.113554.1.2.2.3 */
+
 	/* Microsoft Authenticode & Software Publishing */
 	OID_msIndirectData,		/* 1.3.6.1.4.1.311.2.1.4 */
 	OID_msStatementType,		/* 1.3.6.1.4.1.311.2.1.11 */
@@ -62,6 +66,10 @@  enum OID {
 	OID_msIndividualSPKeyPurpose,	/* 1.3.6.1.4.1.311.2.1.21 */
 	OID_msOutlookExpress,		/* 1.3.6.1.4.1.311.16.4 */
 
+	OID_ntlmssp,			/* 1.3.6.1.4.1.311.2.2.10 */
+
+	OID_spnego,			/* 1.3.6.1.5.5.2 */
+
 	OID_certAuthInfoAccess,		/* 1.3.6.1.5.5.7.1.1 */
 	OID_sha1,			/* 1.3.14.3.2.26 */
 	OID_id_ansip384r1,		/* 1.3.132.0.34 */