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authorDavid Disseldorp <ddiss@suse.de>2023-04-07 00:34:11 +0200
committerSteve French <stfrench@microsoft.com>2023-04-15 18:26:56 -0500
commit5105a7ffce19160e7062aee67fb6b3b8a1b56d78 (patch)
treeee227deca4072e030d02e42c3722530098e0d18e
parent09a9639e56c01c7a00d6c0ca63f4c7c41abe075d (diff)
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: 5100d8a3fe03 ("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>
-rw-r--r--fs/cifs/smb2pdu.c41
1 files changed, 31 insertions, 10 deletions
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 2b92132097dc..4245249dbba8 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -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;