CVE-2017-12163: s3:smbd: Prevent client short SMB1 write from writing server memory...

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13020

Signed-off-by: Jeremy Allison <jra@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>

diff --git a/source3/smbd/reply.c b/source3/smbd/reply.c
index 82dcbba0c1d752aa43f7d0a291edae3addaad568..a40ff81b24055cb5dcbf2cdfe3700f6a84cca1eb 100644 (file)
--- a/source3/smbd/reply.c
+++ b/source3/smbd/reply.c
@@ -4489,6 +4489,9 @@ void reply_writebraw(struct smb_request *req)
        }
 
        /* 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);
@@ -4589,6 +4592,11 @@ void reply_writebraw(struct smb_request *req)
                        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);
@@ -4670,6 +4678,7 @@ void reply_writeunlock(struct smb_request *req)
        connection_struct *conn = req->conn;
        ssize_t nwritten = -1;
        size_t numtowrite;
+       size_t remaining;
        off_t startpos;
        const char *data;
        NTSTATUS status = NT_STATUS_OK;
@@ -4702,6 +4711,17 @@ void reply_writeunlock(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(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,
@@ -4783,6 +4803,7 @@ void reply_write(struct smb_request *req)
 {
        connection_struct *conn = req->conn;
        size_t numtowrite;
+       size_t remaining;
        ssize_t nwritten = -1;
        off_t startpos;
        const char *data;
@@ -4823,6 +4844,17 @@ 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,
@@ -5049,6 +5081,9 @@ void reply_write_and_X(struct smb_request *req)
                        goto out;
                }
        } 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);
@@ -5477,6 +5512,7 @@ void reply_writeclose(struct smb_request *req)
 {
        connection_struct *conn = req->conn;
        size_t numtowrite;
+       size_t remaining;
        ssize_t nwritten = -1;
        NTSTATUS close_status = NT_STATUS_OK;
        off_t startpos;
@@ -5510,6 +5546,17 @@ void reply_writeclose(struct smb_request *req)
        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 == NULL) {
                init_strict_lock_struct(fsp, (uint64_t)req->smbpid,
                    (uint64_t)startpos, (uint64_t)numtowrite, WRITE_LOCK,
@@ -6105,6 +6152,9 @@ void reply_printwrite(struct smb_request *req)
 
        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);