From 284d3b2cabef10362a574efe209d1d406f351dfa Mon Sep 17 00:00:00 2001 From: Oguz Bektas Date: Thu, 6 Feb 2020 15:25:49 +0100 Subject: [PATCH] security patches for libslirp CVE-2020-8608 original commits and email can be found here[0] A out-of-bounds heap buffer access issue was found in the SLiRP networking implementation of the QEMU emulator. It occurs in tcp_emu() routine while emulating IRC and other protocols due to unsafe usage of snprintf(3) function. A user/process could use this flaw to crash the Qemu process on the host resulting in DoS or potentially execute arbitrary code with privileges of the QEMU process on the host. [0]: https://seclists.org/oss-sec/2020/q1/64 Signed-off-by: Oguz Bektas Signed-off-by: Thomas Lamprecht --- .../0004-util-add-slirp_fmt-helpers.patch | 126 ++++++++++++++++ ...5-tcp_emu-fix-unsafe-snprintf-usages.patch | 135 ++++++++++++++++++ debian/patches/series | 2 + 3 files changed, 263 insertions(+) create mode 100644 debian/patches/extra/0004-util-add-slirp_fmt-helpers.patch create mode 100644 debian/patches/extra/0005-tcp_emu-fix-unsafe-snprintf-usages.patch diff --git a/debian/patches/extra/0004-util-add-slirp_fmt-helpers.patch b/debian/patches/extra/0004-util-add-slirp_fmt-helpers.patch new file mode 100644 index 0000000..af944f8 --- /dev/null +++ b/debian/patches/extra/0004-util-add-slirp_fmt-helpers.patch @@ -0,0 +1,126 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= +Date: Mon, 27 Jan 2020 10:24:09 +0100 +Subject: [PATCH 1/2] util: add slirp_fmt() helpers +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Various calls to snprintf() in libslirp assume that snprintf() returns +"only" the number of bytes written (excluding terminating NUL). + +https://pubs.opengroup.org/onlinepubs/9699919799/functions/snprintf.html#tag_16_159_04 + +"Upon successful completion, the snprintf() function shall return the +number of bytes that would be written to s had n been sufficiently +large excluding the terminating null byte." + +Introduce slirp_fmt() that handles several pathological cases the +way libslirp usually expect: + +- treat error as fatal (instead of silently returning -1) + +- fmt0() will always \0 end + +- return the number of bytes actually written (instead of what would +have been written, which would usually result in OOB later), including +the ending \0 for fmt0() + +- warn if truncation happened (instead of ignoring) + +Other less common cases can still be handled with strcpy/snprintf() etc. + +Signed-off-by: Marc-André Lureau +Reviewed-by: Samuel Thibault +Message-Id: <20200127092414.169796-2-marcandre.lureau@redhat.com> +Signed-off-by: Oguz Bektas +--- + slirp/src/util.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ + slirp/src/util.h | 3 +++ + 2 files changed, 65 insertions(+) + +diff --git a/slirp/src/util.c b/slirp/src/util.c +index e596087..e3b6257 100644 +--- a/slirp/src/util.c ++++ b/slirp/src/util.c +@@ -364,3 +364,65 @@ void slirp_pstrcpy(char *buf, int buf_size, const char *str) + } + *q = '\0'; + } ++ ++static int slirp_vsnprintf(char *str, size_t size, ++ const char *format, va_list args) ++{ ++ int rv = vsnprintf(str, size, format, args); ++ ++ if (rv < 0) { ++ g_error("vsnprintf() failed: %s", g_strerror(errno)); ++ } ++ ++ return rv; ++} ++ ++/* ++ * A snprintf()-like function that: ++ * - returns the number of bytes written (excluding optional \0-ending) ++ * - dies on error ++ * - warn on truncation ++ */ ++int slirp_fmt(char *str, size_t size, const char *format, ...) ++{ ++ va_list args; ++ int rv; ++ ++ va_start(args, format); ++ rv = slirp_vsnprintf(str, size, format, args); ++ va_end(args); ++ ++ if (rv > size) { ++ g_critical("vsnprintf() truncation"); ++ } ++ ++ return MIN(rv, size); ++} ++ ++/* ++ * A snprintf()-like function that: ++ * - always \0-end (unless size == 0) ++ * - returns the number of bytes actually written, including \0 ending ++ * - dies on error ++ * - warn on truncation ++ */ ++int slirp_fmt0(char *str, size_t size, const char *format, ...) ++{ ++ va_list args; ++ int rv; ++ ++ va_start(args, format); ++ rv = slirp_vsnprintf(str, size, format, args); ++ va_end(args); ++ ++ if (rv >= size) { ++ g_critical("vsnprintf() truncation"); ++ if (size > 0) ++ str[size - 1] = '\0'; ++ rv = size; ++ } else { ++ rv += 1; /* include \0 */ ++ } ++ ++ return rv; ++} +diff --git a/slirp/src/util.h b/slirp/src/util.h +index 3c6223c..0558dfc 100644 +--- a/slirp/src/util.h ++++ b/slirp/src/util.h +@@ -177,4 +177,7 @@ static inline int slirp_socket_set_fast_reuse(int fd) + + void slirp_pstrcpy(char *buf, int buf_size, const char *str); + ++int slirp_fmt(char *str, size_t size, const char *format, ...); ++int slirp_fmt0(char *str, size_t size, const char *format, ...); ++ + #endif +-- +2.20.1 + diff --git a/debian/patches/extra/0005-tcp_emu-fix-unsafe-snprintf-usages.patch b/debian/patches/extra/0005-tcp_emu-fix-unsafe-snprintf-usages.patch new file mode 100644 index 0000000..099fecd --- /dev/null +++ b/debian/patches/extra/0005-tcp_emu-fix-unsafe-snprintf-usages.patch @@ -0,0 +1,135 @@ +From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= +Date: Mon, 27 Jan 2020 10:24:14 +0100 +Subject: [PATCH 2/2] tcp_emu: fix unsafe snprintf() usages +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +Various calls to snprintf() assume that snprintf() returns "only" the +number of bytes written (excluding terminating NUL). + +https://pubs.opengroup.org/onlinepubs/9699919799/functions/snprintf.html#tag_16_159_04 + +"Upon successful completion, the snprintf() function shall return the +number of bytes that would be written to s had n been sufficiently +large excluding the terminating null byte." + +Before patch ce131029, if there isn't enough room in "m_data" for the +"DCC ..." message, we overflow "m_data". + +After the patch, if there isn't enough room for the same, we don't +overflow "m_data", but we set "m_len" out-of-bounds. The next time an +access is bounded by "m_len", we'll have a buffer overflow then. + +Use slirp_fmt*() to fix potential OOB memory access. + +Reported-by: Laszlo Ersek +Signed-off-by: Marc-André Lureau +Reviewed-by: Samuel Thibault +Message-Id: <20200127092414.169796-7-marcandre.lureau@redhat.com> +Signed-off-by: Oguz Bektas +--- + slirp/src/tcp_subr.c | 44 +++++++++++++++++++++----------------------- + 1 file changed, 21 insertions(+), 23 deletions(-) + +diff --git a/slirp/src/tcp_subr.c b/slirp/src/tcp_subr.c +index d6dd133..93b3488 100644 +--- a/slirp/src/tcp_subr.c ++++ b/slirp/src/tcp_subr.c +@@ -655,8 +655,7 @@ int tcp_emu(struct socket *so, struct mbuf *m) + NTOHS(n1); + NTOHS(n2); + m_inc(m, snprintf(NULL, 0, "%d,%d\r\n", n1, n2) + 1); +- m->m_len = snprintf(m->m_data, M_ROOM(m), "%d,%d\r\n", n1, n2); +- assert(m->m_len < M_ROOM(m)); ++ m->m_len = slirp_fmt(m->m_data, M_ROOM(m), "%d,%d\r\n", n1, n2); + } else { + *eol = '\r'; + } +@@ -696,9 +695,9 @@ int tcp_emu(struct socket *so, struct mbuf *m) + n4 = (laddr & 0xff); + + m->m_len = bptr - m->m_data; /* Adjust length */ +- m->m_len += snprintf(bptr, m->m_size - m->m_len, +- "ORT %d,%d,%d,%d,%d,%d\r\n%s", n1, n2, n3, n4, +- n5, n6, x == 7 ? buff : ""); ++ m->m_len += slirp_fmt(bptr, M_FREEROOM(m), ++ "ORT %d,%d,%d,%d,%d,%d\r\n%s", ++ n1, n2, n3, n4, n5, n6, x == 7 ? buff : ""); + return 1; + } else if ((bptr = (char *)strstr(m->m_data, "27 Entering")) != NULL) { + /* +@@ -731,11 +730,9 @@ int tcp_emu(struct socket *so, struct mbuf *m) + n4 = (laddr & 0xff); + + m->m_len = bptr - m->m_data; /* Adjust length */ +- m->m_len += +- snprintf(bptr, m->m_size - m->m_len, +- "27 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n%s", +- n1, n2, n3, n4, n5, n6, x == 7 ? buff : ""); +- ++ m->m_len += slirp_fmt(bptr, M_FREEROOM(m), ++ "27 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n%s", ++ n1, n2, n3, n4, n5, n6, x == 7 ? buff : ""); + return 1; + } + +@@ -758,8 +755,8 @@ int tcp_emu(struct socket *so, struct mbuf *m) + if (m->m_data[m->m_len - 1] == '\0' && lport != 0 && + (so = tcp_listen(slirp, INADDR_ANY, 0, so->so_laddr.s_addr, + htons(lport), SS_FACCEPTONCE)) != NULL) +- m->m_len = +- snprintf(m->m_data, m->m_size, "%d", ntohs(so->so_fport)) + 1; ++ m->m_len = slirp_fmt0(m->m_data, M_ROOM(m), ++ "%d", ntohs(so->so_fport)); + return 1; + + case EMU_IRC: +@@ -778,9 +775,10 @@ int tcp_emu(struct socket *so, struct mbuf *m) + return 1; + } + m->m_len = bptr - m->m_data; /* Adjust length */ +- m->m_len += snprintf(bptr, m->m_size, "DCC CHAT chat %lu %u%c\n", +- (unsigned long)ntohl(so->so_faddr.s_addr), +- ntohs(so->so_fport), 1); ++ m->m_len += slirp_fmt(bptr, M_FREEROOM(m), ++ "DCC CHAT chat %lu %u%c\n", ++ (unsigned long)ntohl(so->so_faddr.s_addr), ++ ntohs(so->so_fport), 1); + } else if (sscanf(bptr, "DCC SEND %256s %u %u %u", buff, &laddr, &lport, + &n1) == 4) { + if ((so = tcp_listen(slirp, INADDR_ANY, 0, htonl(laddr), +@@ -788,10 +786,10 @@ int tcp_emu(struct socket *so, struct mbuf *m) + return 1; + } + m->m_len = bptr - m->m_data; /* Adjust length */ +- m->m_len += +- snprintf(bptr, m->m_size, "DCC SEND %s %lu %u %u%c\n", buff, +- (unsigned long)ntohl(so->so_faddr.s_addr), +- ntohs(so->so_fport), n1, 1); ++ m->m_len += slirp_fmt(bptr, M_FREEROOM(m), ++ "DCC SEND %s %lu %u %u%c\n", buff, ++ (unsigned long)ntohl(so->so_faddr.s_addr), ++ ntohs(so->so_fport), n1, 1); + } else if (sscanf(bptr, "DCC MOVE %256s %u %u %u", buff, &laddr, &lport, + &n1) == 4) { + if ((so = tcp_listen(slirp, INADDR_ANY, 0, htonl(laddr), +@@ -799,10 +797,10 @@ int tcp_emu(struct socket *so, struct mbuf *m) + return 1; + } + m->m_len = bptr - m->m_data; /* Adjust length */ +- m->m_len += +- snprintf(bptr, m->m_size, "DCC MOVE %s %lu %u %u%c\n", buff, +- (unsigned long)ntohl(so->so_faddr.s_addr), +- ntohs(so->so_fport), n1, 1); ++ m->m_len += slirp_fmt(bptr, M_FREEROOM(m), ++ "DCC MOVE %s %lu %u %u%c\n", buff, ++ (unsigned long)ntohl(so->so_faddr.s_addr), ++ ntohs(so->so_fport), n1, 1); + } + return 1; + +-- +2.20.1 + diff --git a/debian/patches/series b/debian/patches/series index 8222495..6f5dcd0 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -1,6 +1,8 @@ extra/0001-monitor-qmp-resume-monitor-when-clearing-its-queue.patch extra/0002-virtio-blk-schedule-virtio_notify_config-to-run-on-m.patch extra/0003-vnc-fix-memory-leak-when-vnc-disconnect.patch +extra/0004-util-add-slirp_fmt-helpers.patch +extra/0005-tcp_emu-fix-unsafe-snprintf-usages.patch pve/0001-PVE-Config-block-file-change-locking-default-to-off.patch pve/0002-PVE-Config-Adjust-network-script-path-to-etc-kvm.patch pve/0003-PVE-Config-set-the-CPU-model-to-kvm64-32-instead-of-.patch