File 0153-CVE-2015-1779-limit-size-of-HTTP-he.patch of Package qemu.3557

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File 0153-CVE-2015-1779-limit-size-of-HTTP-he.patch of Package qemu.3557

From 720065c7a27de182c484958c3a9d43b8732a82d8 Mon Sep 17 00:00:00 2001
From: "Daniel P. Berrange" <berrange@redhat.com>
Date: Mon, 23 Mar 2015 22:58:22 +0000
Subject: [PATCH] CVE-2015-1779: limit size of HTTP headers from websockets
 clients
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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The VNC server websockets decoder will read and buffer data from
websockets clients until it sees the end of the HTTP headers,
as indicated by \r\n\r\n. In theory this allows a malicious to
trick QEMU into consuming an arbitrary amount of RAM. In practice,
because QEMU runs g_strstr_len() across the buffered header data,
it will spend increasingly long burning CPU time searching for
the substring match and less & less time reading data. So while
this does cause arbitrary memory growth, the bigger problem is
that QEMU will be burning 100% of available CPU time.

A novnc websockets client typically sends headers of around
512 bytes in length. As such it is reasonable to place a 4096
byte limit on the amount of data buffered while searching for
the end of HTTP headers.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 2cdb5e142fb93e875fa53c52864ef5eb8d5d8b41)
[AF: BSC#924018]
Signed-off-by: Andreas Färber <afaerber@suse.de>
---
 ui/vnc-ws.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/ui/vnc-ws.c b/ui/vnc-ws.c
index e5c1911..1ea8554 100644
--- a/ui/vnc-ws.c
+++ b/ui/vnc-ws.c
@@ -89,8 +89,11 @@ void vncws_handshake_read(void *opaque)
     VncState *vs = opaque;
     uint8_t *handshake_end;
     long ret;
-    buffer_reserve(&vs->ws_input, 4096);
-    ret = vnc_client_read_buf(vs, buffer_end(&vs->ws_input), 4096);
+    /* Typical HTTP headers from novnc are 512 bytes, so limiting
+     * total header size to 4096 is easily enough. */
+    size_t want = 4096 - vs->ws_input.offset;
+    buffer_reserve(&vs->ws_input, want);
+    ret = vnc_client_read_buf(vs, buffer_end(&vs->ws_input), want);
 
     if (!ret) {
         if (vs->csock == -1) {
@@ -107,6 +110,9 @@ void vncws_handshake_read(void *opaque)
         vncws_process_handshake(vs, vs->ws_input.buffer, vs->ws_input.offset);
         buffer_advance(&vs->ws_input, handshake_end - vs->ws_input.buffer +
                 strlen(WS_HANDSHAKE_END));
+    } else if (vs->ws_input.offset >= 4096) {
+        VNC_DEBUG("End of headers not found in first 4096 bytes\n");
+        vnc_client_error(vs);
     }
 }

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File 0153-CVE-2015-1779-limit-size-of-HTTP-he.patch of Package qemu.3557

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