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SUSE:SLE-12-SP1:GA
qemu-linux-user.6354
0152-CVE-2015-1779-incrementally-decode-.patch
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File 0152-CVE-2015-1779-incrementally-decode-.patch of Package qemu-linux-user.6354
From 30cb84d120392d9d65d4ed0c69d7004097f4acd1 Mon Sep 17 00:00:00 2001 From: "Daniel P. Berrange" <berrange@redhat.com> Date: Mon, 23 Mar 2015 22:58:21 +0000 Subject: [PATCH] CVE-2015-1779: incrementally decode websocket frames MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 ] [ kraxel: fix 32bit build ] Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> (cherry picked from commit a2bebfd6e09d285aa793cae3fb0fc3a39a9fee6e) [AF: BSC#924018] Signed-off-by: Andreas Färber <afaerber@suse.de> --- ui/vnc-ws.c | 105 ++++++++++++++++++++++++++++++++++++++++-------------------- ui/vnc-ws.h | 9 ++++-- ui/vnc.h | 2 ++ 3 files changed, 80 insertions(+), 36 deletions(-) diff --git a/ui/vnc-ws.c b/ui/vnc-ws.c index e304bafeb0..e5c1911119 100644 --- a/ui/vnc-ws.c +++ b/ui/vnc-ws.c @@ -115,7 +115,7 @@ long vnc_client_read_ws(VncState *vs) { int ret, err; uint8_t *payload; - size_t payload_size, frame_size; + size_t payload_size, header_size; VNC_DEBUG("Read websocket %p size %zd offset %zd\n", vs->ws_input.buffer, vs->ws_input.capacity, vs->ws_input.offset); buffer_reserve(&vs->ws_input, 4096); @@ -125,18 +125,39 @@ long vnc_client_read_ws(VncState *vs) } vs->ws_input.offset += ret; - /* make sure that nothing is left in the ws_input buffer */ + ret = 0; + /* consume as much of ws_input buffer as possible */ do { - err = vncws_decode_frame(&vs->ws_input, &payload, - &payload_size, &frame_size); - if (err <= 0) { - return err; + if (vs->ws_payload_remain == 0) { + err = vncws_decode_frame_header(&vs->ws_input, + &header_size, + &vs->ws_payload_remain, + &vs->ws_payload_mask); + if (err <= 0) { + return err; + } + + buffer_advance(&vs->ws_input, header_size); } + if (vs->ws_payload_remain != 0) { + err = vncws_decode_frame_payload(&vs->ws_input, + &vs->ws_payload_remain, + &vs->ws_payload_mask, + &payload, + &payload_size); + if (err < 0) { + return err; + } + if (err == 0) { + return ret; + } + ret += err; - buffer_reserve(&vs->input, payload_size); - buffer_append(&vs->input, payload, payload_size); + buffer_reserve(&vs->input, payload_size); + buffer_append(&vs->input, payload, payload_size); - buffer_advance(&vs->ws_input, frame_size); + buffer_advance(&vs->ws_input, payload_size); + } } while (vs->ws_input.offset > 0); return ret; @@ -274,15 +295,14 @@ void vncws_encode_frame(Buffer *output, const void *payload, buffer_append(output, payload, payload_size); } -int vncws_decode_frame(Buffer *input, uint8_t **payload, - size_t *payload_size, size_t *frame_size) +int vncws_decode_frame_header(Buffer *input, + size_t *header_size, + size_t *payload_remain, + WsMask *payload_mask) { unsigned char opcode = 0, fin = 0, has_mask = 0; - size_t header_size = 0; - uint32_t *payload32; + size_t payload_len; WsHeader *header = (WsHeader *)input->buffer; - WsMask mask; - int i; if (input->offset < WS_HEAD_MIN_LEN + 4) { /* header not complete */ @@ -292,7 +312,7 @@ int vncws_decode_frame(Buffer *input, uint8_t **payload, fin = (header->b0 & 0x80) >> 7; opcode = header->b0 & 0x0f; has_mask = (header->b1 & 0x80) >> 7; - *payload_size = header->b1 & 0x7f; + payload_len = header->b1 & 0x7f; if (opcode == WS_OPCODE_CLOSE) { /* disconnect */ @@ -309,40 +329,57 @@ int vncws_decode_frame(Buffer *input, uint8_t **payload, return -2; } - if (*payload_size < 126) { - header_size = 6; - mask = header->u.m; - } else if (*payload_size == 126 && input->offset >= 8) { - *payload_size = be16_to_cpu(header->u.s16.l16); - header_size = 8; - mask = header->u.s16.m16; - } else if (*payload_size == 127 && input->offset >= 14) { - *payload_size = be64_to_cpu(header->u.s64.l64); - header_size = 14; - mask = header->u.s64.m64; + if (payload_len < 126) { + *payload_remain = payload_len; + *header_size = 6; + *payload_mask = header->u.m; + } else if (payload_len == 126 && input->offset >= 8) { + *payload_remain = be16_to_cpu(header->u.s16.l16); + *header_size = 8; + *payload_mask = header->u.s16.m16; + } else if (payload_len == 127 && input->offset >= 14) { + *payload_remain = be64_to_cpu(header->u.s64.l64); + *header_size = 14; + *payload_mask = header->u.s64.m64; } else { /* header not complete */ return 0; } - *frame_size = header_size + *payload_size; + return 1; +} + +int vncws_decode_frame_payload(Buffer *input, + size_t *payload_remain, WsMask *payload_mask, + uint8_t **payload, size_t *payload_size) +{ + size_t i; + uint32_t *payload32; - if (input->offset < *frame_size) { - /* frame not complete */ + *payload = input->buffer; + /* If we aren't at the end of the payload, then drop + * off the last bytes, so we're always multiple of 4 + * for purpose of unmasking, except at end of payload + */ + if (input->offset < *payload_remain) { + *payload_size = input->offset - (input->offset % 4); + } else { + *payload_size = *payload_remain; + } + if (*payload_size == 0) { return 0; } - - *payload = input->buffer + header_size; + *payload_remain -= *payload_size; /* unmask frame */ /* process 1 frame (32 bit op) */ payload32 = (uint32_t *)(*payload); for (i = 0; i < *payload_size / 4; i++) { - payload32[i] ^= mask.u; + payload32[i] ^= payload_mask->u; } /* process the remaining bytes (if any) */ for (i *= 4; i < *payload_size; i++) { - (*payload)[i] ^= mask.c[i % 4]; + (*payload)[i] ^= payload_mask->c[i % 4]; } return 1; diff --git a/ui/vnc-ws.h b/ui/vnc-ws.h index 95c1b0aeae..6e93fa0200 100644 --- a/ui/vnc-ws.h +++ b/ui/vnc-ws.h @@ -83,7 +83,12 @@ long vnc_client_read_ws(VncState *vs); void vncws_process_handshake(VncState *vs, uint8_t *line, size_t size); void vncws_encode_frame(Buffer *output, const void *payload, const size_t payload_size); -int vncws_decode_frame(Buffer *input, uint8_t **payload, - size_t *payload_size, size_t *frame_size); +int vncws_decode_frame_header(Buffer *input, + size_t *header_size, + size_t *payload_remain, + WsMask *payload_mask); +int vncws_decode_frame_payload(Buffer *input, + size_t *payload_remain, WsMask *payload_mask, + uint8_t **payload, size_t *payload_size); #endif /* __QEMU_UI_VNC_WS_H */ diff --git a/ui/vnc.h b/ui/vnc.h index 8da81b8d6e..6606a427df 100644 --- a/ui/vnc.h +++ b/ui/vnc.h @@ -299,6 +299,8 @@ struct VncState #ifdef CONFIG_VNC_WS Buffer ws_input; Buffer ws_output; + size_t ws_payload_remain; + WsMask ws_payload_mask; #endif /* current output mode information */ VncWritePixels *write_pixels;
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