From fc39a77d600968f5ad7dce2bf66e160caa90854a Mon Sep 17 00:00:00 2001 From: Cole Robinson Date: Apr 02 2015 18:11:41 +0000 Subject: CVE-2015-1779 vnc: insufficient resource limiting in VNC websockets decoder (bz #1205051, bz #1199572) --- diff --git a/0015-CVE-2015-1779-incrementally-decode-websocket-frames.patch b/0015-CVE-2015-1779-incrementally-decode-websocket-frames.patch new file mode 100644 index 0000000..05a3483 --- /dev/null +++ b/0015-CVE-2015-1779-incrementally-decode-websocket-frames.patch @@ -0,0 +1,238 @@ +From: "Daniel P. Berrange" +Date: Mon, 23 Mar 2015 22:58:21 +0000 +Subject: [PATCH] CVE-2015-1779: incrementally decode websocket frames + +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 + +[ 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 +(cherry picked from commit a2bebfd6e09d285aa793cae3fb0fc3a39a9fee6e) +--- + 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 e304baf..e5c1911 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 95c1b0a..6e93fa0 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 334de9d..8630c6c 100644 +--- a/ui/vnc.h ++++ b/ui/vnc.h +@@ -302,6 +302,8 @@ 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; diff --git a/0016-CVE-2015-1779-limit-size-of-HTTP-headers-from-websoc.patch b/0016-CVE-2015-1779-limit-size-of-HTTP-headers-from-websoc.patch new file mode 100644 index 0000000..07a3cc3 --- /dev/null +++ b/0016-CVE-2015-1779-limit-size-of-HTTP-headers-from-websoc.patch @@ -0,0 +1,55 @@ +From: "Daniel P. Berrange" +Date: Mon, 23 Mar 2015 22:58:22 +0000 +Subject: [PATCH] CVE-2015-1779: limit size of HTTP headers from websockets + clients + +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 +Signed-off-by: Gerd Hoffmann +(cherry picked from commit 2cdb5e142fb93e875fa53c52864ef5eb8d5d8b41) +--- + 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); + } + } + diff --git a/qemu.spec b/qemu.spec index 3d1de4c..c1f774c 100644 --- a/qemu.spec +++ b/qemu.spec @@ -152,7 +152,7 @@ Summary: QEMU is a FAST! processor emulator Name: qemu Version: 2.1.3 -Release: 4%{?dist} +Release: 5%{?dist} Epoch: 2 License: GPLv2+ and LGPLv2+ and BSD Group: Development/Tools @@ -215,6 +215,10 @@ Patch0012: 0012-cirrus-fix-blit-region-check.patch Patch0013: 0013-cirrus-don-t-overflow-CirrusVGAState-cirrus_bltbuf.patch # Fix .vdi disk corruption (bz #1199400) Patch0014: 0014-block-vdi-Add-locking-for-parallel-requests.patch +# CVE-2015-1779 vnc: insufficient resource limiting in VNC websockets +# decoder (bz #1205051, bz #1199572) +Patch0015: 0015-CVE-2015-1779-incrementally-decode-websocket-frames.patch +Patch0016: 0016-CVE-2015-1779-limit-size-of-HTTP-headers-from-websoc.patch BuildRequires: SDL2-devel BuildRequires: zlib-devel @@ -764,6 +768,10 @@ CAC emulation development files. %patch0013 -p1 # Fix .vdi disk corruption (bz #1199400) %patch0014 -p1 +# CVE-2015-1779 vnc: insufficient resource limiting in VNC websockets +# decoder (bz #1205051, bz #1199572) +%patch0015 -p1 +%patch0016 -p1 %build @@ -1544,6 +1552,10 @@ getent passwd qemu >/dev/null || \ %endif %changelog +* Thu Apr 02 2015 Cole Robinson - 2:2.1.3-5 +- CVE-2015-1779 vnc: insufficient resource limiting in VNC websockets decoder + (bz #1205051, bz #1199572) + * Fri Mar 27 2015 Cole Robinson - 2:2.1.3-4 - Qemu: PRDT overflow from guest to host (bz #1204919, bz #1205322) - CVE-2014-8106: cirrus: insufficient blit region checks (bz #1170612, bz