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https://github.com/xemu-project/xemu.git
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a2bebfd6e0
The logic for decoding websocket frames wants to fully decode the frame header and payload, before allowing the VNC server to see any of the payload data. There is no size limit on websocket payloads, so this allows a malicious network client to consume 2^64 bytes in memory in QEMU. It can trigger this denial of service before the VNC server even performs any authentication. The fix is to decode the header, and then incrementally decode the payload data as it is needed. With this fix the websocket decoder will allow at most 4k of data to be buffered before decoding and processing payload. Signed-off-by: Daniel P. Berrange <berrange@redhat.com> [ kraxel: fix frequent spurious disconnects, suggested by Peter Maydell ] @@ -361,7 +361,7 @@ int vncws_decode_frame_payload(Buffer *input, - *payload_size = input->offset; + *payload_size = *payload_remain; [ kraxel: fix 32bit build ] @@ -306,7 +306,7 @@ struct VncState - uint64_t ws_payload_remain; + size_t ws_payload_remain; Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
95 lines
2.8 KiB
C
95 lines
2.8 KiB
C
/*
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* QEMU VNC display driver: Websockets support
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*
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* Copyright (C) 2010 Joel Martin
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* Copyright (C) 2012 Tim Hardeck
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*
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* This is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This software is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this software; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __QEMU_UI_VNC_WS_H
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#define __QEMU_UI_VNC_WS_H
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#include <gnutls/gnutls.h>
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#define B64LEN(__x) (((__x + 2) / 3) * 12 / 3)
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#define SHA1_DIGEST_LEN 20
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#define WS_ACCEPT_LEN (B64LEN(SHA1_DIGEST_LEN) + 1)
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#define WS_CLIENT_KEY_LEN 24
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#define WS_GUID "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
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#define WS_GUID_LEN strlen(WS_GUID)
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#define WS_HANDSHAKE "HTTP/1.1 101 Switching Protocols\r\n\
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Upgrade: websocket\r\n\
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Connection: Upgrade\r\n\
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Sec-WebSocket-Accept: %s\r\n\
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Sec-WebSocket-Protocol: binary\r\n\
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\r\n"
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#define WS_HANDSHAKE_DELIM "\r\n"
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#define WS_HANDSHAKE_END "\r\n\r\n"
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#define WS_SUPPORTED_VERSION "13"
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#define WS_HEAD_MIN_LEN sizeof(uint16_t)
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#define WS_HEAD_MAX_LEN (WS_HEAD_MIN_LEN + sizeof(uint64_t) + sizeof(uint32_t))
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typedef union WsMask {
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char c[4];
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uint32_t u;
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} WsMask;
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typedef struct QEMU_PACKED WsHeader {
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unsigned char b0;
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unsigned char b1;
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union {
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struct QEMU_PACKED {
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uint16_t l16;
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WsMask m16;
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} s16;
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struct QEMU_PACKED {
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uint64_t l64;
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WsMask m64;
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} s64;
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WsMask m;
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} u;
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} WsHeader;
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enum {
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WS_OPCODE_CONTINUATION = 0x0,
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WS_OPCODE_TEXT_FRAME = 0x1,
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WS_OPCODE_BINARY_FRAME = 0x2,
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WS_OPCODE_CLOSE = 0x8,
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WS_OPCODE_PING = 0x9,
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WS_OPCODE_PONG = 0xA
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};
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#ifdef CONFIG_VNC_TLS
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void vncws_tls_handshake_io(void *opaque);
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#endif /* CONFIG_VNC_TLS */
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void vncws_handshake_read(void *opaque);
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long vnc_client_write_ws(VncState *vs);
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long vnc_client_read_ws(VncState *vs);
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void vncws_process_handshake(VncState *vs, uint8_t *line, size_t size);
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void vncws_encode_frame(Buffer *output, const void *payload,
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const size_t payload_size);
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int vncws_decode_frame_header(Buffer *input,
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size_t *header_size,
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size_t *payload_remain,
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WsMask *payload_mask);
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int vncws_decode_frame_payload(Buffer *input,
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size_t *payload_remain, WsMask *payload_mask,
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uint8_t **payload, size_t *payload_size);
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#endif /* __QEMU_UI_VNC_WS_H */
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