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From: =?utf-8?q?Guido_G=C3=BCnther?= <agx@sigxcpu.org>
Date: Wed, 20 Sep 2017 20:02:03 +0200
Subject: CVE-2017-12163: s3:smbd: Prevent client short SMB1 write from
writing server memory to file.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=13020
Author: Jeremy Allison <jra@samba.org>
Signed-off-by: Jeremy Allison <jra@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
---
source3/smbd/reply.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 50 insertions(+)
--- a/source3/smbd/reply.c
+++ b/source3/smbd/reply.c
@@ -3979,6 +3979,9 @@ void reply_writebraw(struct smb_request
}
/* Ensure we don't write bytes past the end of this packet. */
+ /*
+ * This already protects us against CVE-2017-12163.
+ */
if (data + numtowrite > smb_base(req->inbuf) + smb_len(req->inbuf)) {
reply_nterror(req, NT_STATUS_INVALID_PARAMETER);
error_to_writebrawerr(req);
@@ -4080,6 +4083,11 @@ void reply_writebraw(struct smb_request
exit_server_cleanly("secondary writebraw failed");
}
+ /*
+ * We are not vulnerable to CVE-2017-12163
+ * here as we are guarenteed to have numtowrite
+ * bytes available - we just read from the client.
+ */
nwritten = write_file(req,fsp,buf+4,startpos+nwritten,numtowrite);
if (nwritten == -1) {
TALLOC_FREE(buf);
@@ -4161,6 +4169,7 @@ void reply_writeunlock(struct smb_reques
connection_struct *conn = req->conn;
ssize_t nwritten = -1;
size_t numtowrite;
+ size_t remaining;
SMB_OFF_T startpos;
const char *data;
NTSTATUS status = NT_STATUS_OK;
@@ -4193,6 +4202,17 @@ void reply_writeunlock(struct smb_reques
startpos = IVAL_TO_SMB_OFF_T(req->vwv+2, 0);
data = (const char *)req->buf + 3;
+ /*
+ * Ensure client isn't asking us to write more than
+ * they sent. CVE-2017-12163.
+ */
+ remaining = smbreq_bufrem(req, data);
+ if (numtowrite > remaining) {
+ reply_nterror(req, NT_STATUS_INVALID_PARAMETER);
+ END_PROFILE(SMBwriteunlock);
+ return;
+ }
+
if (!fsp->print_file && numtowrite > 0) {
init_strict_lock_struct(fsp, (uint64_t)req->smbpid,
(uint64_t)startpos, (uint64_t)numtowrite, WRITE_LOCK,
@@ -4274,6 +4294,7 @@ void reply_write(struct smb_request *req
{
connection_struct *conn = req->conn;
size_t numtowrite;
+ size_t remaining;
ssize_t nwritten = -1;
SMB_OFF_T startpos;
const char *data;
@@ -4314,6 +4335,17 @@ void reply_write(struct smb_request *req
startpos = IVAL_TO_SMB_OFF_T(req->vwv+2, 0);
data = (const char *)req->buf + 3;
+ /*
+ * Ensure client isn't asking us to write more than
+ * they sent. CVE-2017-12163.
+ */
+ remaining = smbreq_bufrem(req, data);
+ if (numtowrite > remaining) {
+ reply_nterror(req, NT_STATUS_INVALID_PARAMETER);
+ END_PROFILE(SMBwrite);
+ return;
+ }
+
if (!fsp->print_file) {
init_strict_lock_struct(fsp, (uint64_t)req->smbpid,
(uint64_t)startpos, (uint64_t)numtowrite, WRITE_LOCK,
@@ -4525,6 +4557,9 @@ void reply_write_and_X(struct smb_reques
return;
}
} else {
+ /*
+ * This already protects us against CVE-2017-12163.
+ */
if (smb_doff > smblen || smb_doff + numtowrite < numtowrite ||
smb_doff + numtowrite > smblen) {
reply_nterror(req, NT_STATUS_INVALID_PARAMETER);
@@ -4894,6 +4929,7 @@ void reply_writeclose(struct smb_request
{
connection_struct *conn = req->conn;
size_t numtowrite;
+ size_t remaining;
ssize_t nwritten = -1;
NTSTATUS close_status = NT_STATUS_OK;
SMB_OFF_T startpos;
@@ -4927,6 +4963,17 @@ void reply_writeclose(struct smb_request
mtime = convert_time_t_to_timespec(srv_make_unix_date3(req->vwv+4));
data = (const char *)req->buf + 1;
+ /*
+ * Ensure client isn't asking us to write more than
+ * they sent. CVE-2017-12163.
+ */
+ remaining = smbreq_bufrem(req, data);
+ if (numtowrite > remaining) {
+ reply_nterror(req, NT_STATUS_INVALID_PARAMETER);
+ END_PROFILE(SMBwriteclose);
+ return;
+ }
+
if (!fsp->print_file) {
init_strict_lock_struct(fsp, (uint64_t)req->smbpid,
(uint64_t)startpos, (uint64_t)numtowrite, WRITE_LOCK,
@@ -5497,6 +5544,9 @@ void reply_printwrite(struct smb_request
numtowrite = SVAL(req->buf, 1);
+ /*
+ * This already protects us against CVE-2017-12163.
+ */
if (req->buflen < numtowrite + 3) {
reply_nterror(req, NT_STATUS_INVALID_PARAMETER);
END_PROFILE(SMBsplwr);
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