File 0343-tcp_emu-fix-unsafe-snprintf-usages.patch of Package qemu-linux-user.15026
From 1518e47ebcc177bc6728f852227f9db3b6d6a04c 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
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Git-commit: 68ccb8021a838066f0951d4b2817eb6b6f10a843
References: bsc#1163018, CVE-2020-8608
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>
[Since porting from a quite different now libslirp, quite a bit changed]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
slirp/slirp.h | 1 +
slirp/tcp_subr.c | 40 ++++++++++++++++++++--------------------
2 files changed, 21 insertions(+), 20 deletions(-)
diff --git a/slirp/slirp.h b/slirp/slirp.h
index 203deec480..201fd2d18d 100644
--- a/slirp/slirp.h
+++ b/slirp/slirp.h
@@ -91,6 +91,7 @@ void free(void *ptr);
#include <glib.h>
#include "debug.h"
+#include "util.h"
#include "qemu/queue.h"
#include "qemu/sockets.h"
diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
index eef9e48823..e45e8215bf 100644
--- a/slirp/tcp_subr.c
+++ b/slirp/tcp_subr.c
@@ -706,9 +706,9 @@ 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) {
/*
@@ -739,9 +739,9 @@ 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;
}
@@ -765,8 +765,8 @@ 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:
@@ -786,10 +786,10 @@ 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), htons(lport),
@@ -797,10 +797,10 @@ 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), htons(lport),
@@ -808,10 +808,10 @@ 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;
