gnu: QEMU: Fix CVE-2020-8608.

* gnu/packages/patches/qemu-CVE-2020-8608.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/virtualization.scm (qemu)[source]: Use it.

1 files changed, 269 insertions, 0 deletions

diff --git a/gnu/packages/patches/qemu-CVE-2020-8608.patch b/gnu/packages/patches/qemu-CVE-2020-8608.patch
new file mode 100644
index 0000000000..4cb017c795
--- /dev/null
+++ b/gnu/packages/patches/qemu-CVE-2020-8608.patch
@@ -0,0 +1,269 @@
+Fix CVE-2020-8608:
+
+https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-8608
+https://www.openwall.com/lists/oss-security/2020/02/06/2
+
+Patches copied from upstream dependency repository:
+
+https://gitlab.freedesktop.org/slirp/libslirp/commit/68ccb8021a838066f0951d4b2817eb6b6f10a843
+https://gitlab.freedesktop.org/slirp/libslirp/commit/30648c03b27fb8d9611b723184216cd3174b6775
+
+From 68ccb8021a838066f0951d4b2817eb6b6f10a843 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
+Date: Mon, 27 Jan 2020 10:24:14 +0100
+Subject: [PATCH] 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 <lersek@redhat.com>
+Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
+Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
+Message-Id: <20200127092414.169796-7-marcandre.lureau@redhat.com>
+---
+ src/tcp_subr.c | 44 +++++++++++++++++++++-----------------------
+ 1 file changed, 21 insertions(+), 23 deletions(-)
+
+diff --git a/src/tcp_subr.c b/src/tcp_subr.c
+index a699117..a72c86b 100644
+--- a/slirp/src/tcp_subr.c
++++ b/slirp/src/tcp_subr.c
+@@ -643,8 +643,7 @@ 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';
+             }
+@@ -684,9 +683,9 @@ 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_FREEROOM(m),
+-                                 "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) {
+             /*
+@@ -719,10 +718,9 @@ 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_FREEROOM(m),
+-                         "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;
+         }
+ 
+@@ -745,8 +743,8 @@ 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_ROOM(m),
+-                                "%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:
+@@ -765,10 +763,10 @@ 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_FREEROOM(m),
+-                                 "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),
+@@ -776,10 +774,10 @@ 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_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);
++            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),
+@@ -787,10 +785,10 @@ 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_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);
++            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;
+ 
+-- 
+2.25.1
+
+From 30648c03b27fb8d9611b723184216cd3174b6775 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
+Date: Mon, 27 Jan 2020 10:24:09 +0100
+Subject: [PATCH] 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 <marcandre.lureau@redhat.com>
+Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
+Message-Id: <20200127092414.169796-2-marcandre.lureau@redhat.com>
+---
+ src/util.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ src/util.h |  3 +++
+ 2 files changed, 65 insertions(+)
+
+diff --git a/src/util.c b/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/src/util.h b/src/util.h
+index e9c3073..5530c46 100644
+--- a/slirp/src/util.h
++++ b/slirp/src/util.h
+@@ -181,4 +181,7 @@ 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
+-- 
+2.25.1
+