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SMB3: Fix length checking of SMB3.11 negotiate request

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The length checking for SMB3.11 negotiate request includes
"negotiate contexts" which caused a buffer validation problem
and a confusing warning message on SMB3.11 mount e.g.:

     SMB2 server sent bad RFC1001 len 236 not 170

Fix the length checking for SMB3.11 negotiate to account for
the new negotiate context so that we don't log a warning on
SMB3.11 mount by default but do log warnings if lengths returned
by the server are incorrect.

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
This commit is contained in:
Steve French 2018-04-08 16:14:31 -05:00
parent f2f176b418
commit 136ff1b4b6
2 changed files with 46 additions and 0 deletions
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39
fs/cifs/smb2misc.c
View File

@ -93,6 +93,41 @@ static const __le16 smb2_rsp_struct_sizes[NUMBER_OF_SMB2_COMMANDS] = {
/* SMB2_OPLOCK_BREAK */ cpu_to_le16(24)
};
#ifdef CONFIG_CIFS_SMB311
static __u32 get_neg_ctxt_len(struct smb2_hdr *hdr, __u32 len, __u32 non_ctxlen)
{
__u16 neg_count;
__u32 nc_offset, size_of_pad_before_neg_ctxts;
struct smb2_negotiate_rsp *pneg_rsp = (struct smb2_negotiate_rsp *)hdr;
/* Negotiate contexts are only valid for latest dialect SMB3.11 */
neg_count = le16_to_cpu(pneg_rsp->NegotiateContextCount);
if ((neg_count == 0) ||
(pneg_rsp->DialectRevision != cpu_to_le16(SMB311_PROT_ID)))
return 0;
/* Make sure that negotiate contexts start after gss security blob */
nc_offset = le32_to_cpu(pneg_rsp->NegotiateContextOffset);
if (nc_offset < non_ctxlen - 4 /* RFC1001 len field */) {
printk_once(KERN_WARNING "invalid negotiate context offset\n");
return 0;
}
size_of_pad_before_neg_ctxts = nc_offset - (non_ctxlen - 4);
/* Verify that at least minimal negotiate contexts fit within frame */
if (len < nc_offset + (neg_count * sizeof(struct smb2_neg_context))) {
printk_once(KERN_WARNING "negotiate context goes beyond end\n");
return 0;
}
cifs_dbg(FYI, "length of negcontexts %d pad %d\n",
len - nc_offset, size_of_pad_before_neg_ctxts);
/* length of negcontexts including pad from end of sec blob to them */
return (len - nc_offset) + size_of_pad_before_neg_ctxts;
}
#endif /* CIFS_SMB311 */
int
smb2_check_message(char *buf, unsigned int length, struct TCP_Server_Info *srvr)
{
@ -198,6 +233,10 @@ smb2_check_message(char *buf, unsigned int length, struct TCP_Server_Info *srvr)
clc_len = smb2_calc_size(hdr);
#ifdef CONFIG_CIFS_SMB311
if (shdr->Command == SMB2_NEGOTIATE)
clc_len += get_neg_ctxt_len(hdr, len, clc_len);
#endif /* SMB311 */
if (srvr->vals->header_preamble_size + len != clc_len) {
cifs_dbg(FYI, "Calculated size %u length %zu mismatch mid %llu\n",
clc_len, srvr->vals->header_preamble_size + len, mid);

7
fs/cifs/smb2pdu.h
View File

@ -263,6 +263,13 @@ struct smb2_negotiate_req {
#define SMB2_NT_FIND 0x00100000
#define SMB2_LARGE_FILES 0x00200000
struct smb2_neg_context {
__le16 ContextType;
__le16 DataLength;
__le32 Reserved;
/* Followed by array of data */
} __packed;
#define SMB311_SALT_SIZE 32
/* Hash Algorithm Types */
#define SMB2_PREAUTH_INTEGRITY_SHA512 cpu_to_le16(0x0001)