!1796 修复SSL认证模式下中间人攻击的问题

Merge pull request !1796 from buter/master

src/common/backend/libpq/pqcomm.cpp

@@ -1366,6 +1366,17 @@ static int pq_discardbytes(size_t len)
     return 0;
 }
 
+/* --------------------------------
+ * pq_buffer_has_data - is any buffered data available to read?
+ *
+ * This will *not* attempt to read more data.
+ * --------------------------------
+ */
+bool pq_buffer_has_data(void)
+{
+    return (t_thrd.libpq_cxt.PqRecvPointer < t_thrd.libpq_cxt.PqRecvLength);
+}
+
 /* --------------------------------
  *		pq_getstring	- get a null terminated string from connection
  *

src/common/interfaces/libpq/fe-connect.cpp

@@ -2610,6 +2610,18 @@ keep_going: /* We will come back to here until there is
              */
             pollres = pqsecure_open_client(conn);
             if (pollres == PGRES_POLLING_OK) {
+                /*
+                 * At this point we should have no data already buffered.
+                 * If we do, it was received before we performed the SSL
+                 * handshake, so it wasn't encrypted and indeed may have
+                 * been injected by a man-in-the-middle.
+                 */
+                if (conn->inCursor != conn->inEnd) {
+                    appendPQExpBufferStr(&conn->errorMessage,
+                        libpq_gettext("received unencrypted data after SSL response\n"));
+                    goto error_return;
+                }
+
                 /* SSL handshake done, ready to send startup packet */
                 conn->status = CONNECTION_MADE;
                 return PGRES_POLLING_WRITING;

src/gausskernel/process/postmaster/postmaster.cpp

@@ -3584,6 +3584,18 @@ int ProcessStartupPacket(Port* port, bool SSLdone)
         }
 
 #endif
+        /*
+         * At this point we should have no data already buffered.  If we do,
+         * it was received before we performed the SSL handshake, so it wasn't
+         * encrypted and indeed may have been injected by a man-in-the-middle.
+         * We report this case to the client.
+         */
+        if (pq_buffer_has_data()) {
+            ereport(FATAL, (errcode(ERRCODE_PROTOCOL_VIOLATION), errmsg("received unencrypted data after SSL request"),
+                errdetail("This could be either a client-software bug or "
+                    "evidence of an attempted man-in-the-middle attack.")));
+        }
+
         /* regular startup packet, cancel, etc packet should follow... */
         /* but not another SSL negotiation request */
         return ProcessStartupPacket(port, true);

src/include/libpq/libpq.h

@@ -56,6 +56,7 @@ extern int pq_getmessage(StringInfo s, int maxlen);
 extern int pq_getbyte(void);
 extern int pq_peekbyte(void);
 extern int pq_getbyte_if_available(unsigned char* c);
+extern bool pq_buffer_has_data(void);
 extern int pq_putbytes(const char* s, size_t len);
 extern int pq_flush(void);
 extern int pq_flush_if_writable(void);