fix for issue 81

use different buffers for decode and encode

libvncserver/websockets.c

@@ -79,8 +79,9 @@ typedef int (*wsEncodeFunc)(rfbClientPtr cl, const char *src, int len, char **ds
 typedef int (*wsDecodeFunc)(rfbClientPtr cl, char *dst, int len);
 
 typedef struct ws_ctx_s {
-    char codeBuf[B64LEN(UPDATE_BUF_SIZE) + WSHLENMAX]; /* base64 + maximum frame header length */
-    char readbuf[8192];
+    char codeBufDecode[B64LEN(UPDATE_BUF_SIZE) + WSHLENMAX]; /* base64 + maximum frame header length */
+	char codeBufEncode[B64LEN(UPDATE_BUF_SIZE) + WSHLENMAX]; /* base64 + maximum frame header length */
+	char readbuf[8192];
     int readbufstart;
     int readbuflen;
     int dblen;
@@ -490,15 +491,15 @@ webSocketsEncodeHixie(rfbClientPtr cl, const char *src, int len, char **dst)
     int sz = 0;
     ws_ctx_t *wsctx = (ws_ctx_t *)cl->wsctx;
 
-    wsctx->codeBuf[sz++] = '\x00';
-    len = __b64_ntop((unsigned char *)src, len, wsctx->codeBuf+sz, sizeof(wsctx->codeBuf) - (sz + 1));
+    wsctx->codeBufEncode[sz++] = '\x00';
+    len = __b64_ntop((unsigned char *)src, len, wsctx->codeBufEncode+sz, sizeof(wsctx->codeBufEncode) - (sz + 1));
     if (len < 0) {
         return len;
     }
     sz += len;
 
-    wsctx->codeBuf[sz++] = '\xff';
-    *dst = wsctx->codeBuf;
+    wsctx->codeBufEncode[sz++] = '\xff';
+    *dst = wsctx->codeBufEncode;
     return sz;
 }
 
@@ -536,7 +537,7 @@ webSocketsDecodeHixie(rfbClientPtr cl, char *dst, int len)
     char *buf, *end = NULL;
     ws_ctx_t *wsctx = (ws_ctx_t *)cl->wsctx;
 
-    buf = wsctx->codeBuf;
+    buf = wsctx->codeBufDecode;
 
     n = ws_peek(cl, buf, len*2+2);
 
@@ -657,8 +658,8 @@ webSocketsDecodeHybi(rfbClientPtr cl, char *dst, int len)
       goto spor;
     }
 
-    buf = wsctx->codeBuf;
-    header = (ws_header_t *)wsctx->codeBuf;
+    buf = wsctx->codeBufDecode;
+    header = (ws_header_t *)wsctx->codeBufDecode;
 
     ret = ws_peek(cl, buf, B64LEN(len) + WSHLENMAX);
 
@@ -742,11 +743,11 @@ webSocketsDecodeHybi(rfbClientPtr cl, char *dst, int len)
 	errno = ECONNRESET;
 	break;
       case WS_OPCODE_TEXT_FRAME:
-	if (-1 == (flength = __b64_pton(payload, (unsigned char *)wsctx->codeBuf, sizeof(wsctx->codeBuf)))) {
+	if (-1 == (flength = __b64_pton(payload, (unsigned char *)wsctx->codeBufDecode, sizeof(wsctx->codeBufDecode)))) {
 	  rfbErr("%s: Base64 decode error; %m\n", __func__);
 	  break;
 	}
-	payload = wsctx->codeBuf;
+	payload = wsctx->codeBufDecode;
 	/* fall through */
       case WS_OPCODE_BINARY_FRAME:
 	if (flength > len) {
@@ -790,7 +791,7 @@ webSocketsEncodeHybi(rfbClientPtr cl, const char *src, int len, char **dst)
 	  return 0;
     }
 
-    header = (ws_header_t *)wsctx->codeBuf;
+    header = (ws_header_t *)wsctx->codeBufEncode;
 
     if (wsctx->base64) {
 	opcode = WS_OPCODE_TEXT_FRAME;
@@ -816,7 +817,7 @@ webSocketsEncodeHybi(rfbClientPtr cl, const char *src, int len, char **dst)
     }
 
     if (wsctx->base64) {
-        if (-1 == (ret = __b64_ntop((unsigned char *)src, len, wsctx->codeBuf + sz, sizeof(wsctx->codeBuf) - sz))) {
+        if (-1 == (ret = __b64_ntop((unsigned char *)src, len, wsctx->codeBufEncode + sz, sizeof(wsctx->codeBufEncode) - sz))) {
 	  rfbErr("%s: Base 64 encode failed\n", __func__);
 	} else {
 	  if (ret != blen)
@@ -824,11 +825,12 @@ webSocketsEncodeHybi(rfbClientPtr cl, const char *src, int len, char **dst)
 	  ret += sz;
 	}
     } else {
-      memcpy(wsctx->codeBuf + sz, src, len);
+      memcpy(wsctx->codeBufEncode + sz, src, len);
       ret =  sz + len;
     }
 
-    *dst = wsctx->codeBuf;
+    *dst = wsctx->codeBufEncode;
+
     return ret;
 }