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cifs: fix negotiate context parsing 

smb311_decode_neg_context() doesn't properly check against SMB packet
boundaries prior to accessing individual negotiate context entries. This
is due to the length check omitting the eight byte smb2_neg_context
header, as well as incorrect decrementing of len_of_ctxts.

Fixes: 5100d8a3fe ("SMB311: Improve checking of negotiate security contexts")
Reported-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
David Disseldorp 2023-04-07 00:34:11 +02:00 committed by Steve French
parent 09a9639e56
commit 5105a7ffce
1 changed files with 31 additions and 10 deletions
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41
fs/cifs/smb2pdu.c
View File

@ -587,11 +587,15 @@ assemble_neg_contexts(struct smb2_negotiate_req *req,
}
/* If invalid preauth context warn but use what we requested, SHA-512 */
static void decode_preauth_context(struct smb2_preauth_neg_context *ctxt)
{
unsigned int len = le16_to_cpu(ctxt->DataLength);
/* If invalid preauth context warn but use what we requested, SHA-512 */
/*
* Caller checked that DataLength remains within SMB boundary. We still
* need to confirm that one HashAlgorithms member is accounted for.
*/
if (len < MIN_PREAUTH_CTXT_DATA_LEN) {
pr_warn_once("server sent bad preauth context\n");
return;
@ -610,7 +614,11 @@ static void decode_compress_ctx(struct TCP_Server_Info *server,
{
unsigned int len = le16_to_cpu(ctxt->DataLength);
/* sizeof compress context is a one element compression capbility struct */
/*
* Caller checked that DataLength remains within SMB boundary. We still
* need to confirm that one CompressionAlgorithms member is accounted
* for.
*/
if (len < 10) {
pr_warn_once("server sent bad compression cntxt\n");
return;
@ -632,6 +640,11 @@ static int decode_encrypt_ctx(struct TCP_Server_Info *server,
unsigned int len = le16_to_cpu(ctxt->DataLength);
cifs_dbg(FYI, "decode SMB3.11 encryption neg context of len %d\n", len);
/*
* Caller checked that DataLength remains within SMB boundary. We still
* need to confirm that one Cipher flexible array member is accounted
* for.
*/
if (len < MIN_ENCRYPT_CTXT_DATA_LEN) {
pr_warn_once("server sent bad crypto ctxt len\n");
return -EINVAL;
@ -678,6 +691,11 @@ static void decode_signing_ctx(struct TCP_Server_Info *server,
{
unsigned int len = le16_to_cpu(pctxt->DataLength);
/*
* Caller checked that DataLength remains within SMB boundary. We still
* need to confirm that one SigningAlgorithms flexible array member is
* accounted for.
*/
if ((len < 4) || (len > 16)) {
pr_warn_once("server sent bad signing negcontext\n");
return;
@ -719,14 +737,19 @@ static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp,
for (i = 0; i < ctxt_cnt; i++) {
int clen;
/* check that offset is not beyond end of SMB */
if (len_of_ctxts == 0)
break;
if (len_of_ctxts < sizeof(struct smb2_neg_context))
break;
pctx = (struct smb2_neg_context *)(offset + (char *)rsp);
clen = le16_to_cpu(pctx->DataLength);
clen = sizeof(struct smb2_neg_context)
+ le16_to_cpu(pctx->DataLength);
/*
* 2.2.4 SMB2 NEGOTIATE Response
* Subsequent negotiate contexts MUST appear at the first 8-byte
* aligned offset following the previous negotiate context.
*/
if (i + 1 != ctxt_cnt)
clen = ALIGN(clen, 8);
if (clen > len_of_ctxts)
break;
@ -747,12 +770,10 @@ static int smb311_decode_neg_context(struct smb2_negotiate_rsp *rsp,
else
cifs_server_dbg(VFS, "unknown negcontext of type %d ignored\n",
le16_to_cpu(pctx->ContextType));
if (rc)
break;
/* offsets must be 8 byte aligned */
clen = ALIGN(clen, 8);
offset += clen + sizeof(struct smb2_neg_context);
offset += clen;
len_of_ctxts -= clen;
}
return rc;