Fix CVE-2020-7039: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-7039 Patches copied from upstream dependency repository: https://gitlab.freedesktop.org/slirp/libslirp/commit/2655fffed7a9e765bcb4701dd876e9dab975f289 https://gitlab.freedesktop.org/slirp/libslirp/commit/ce131029d6d4a405cb7d3ac6716d03e58fb4a5d9 https://gitlab.freedesktop.org/slirp/libslirp/commit/82ebe9c370a0e2970fb5695aa19aa5214a6a1c80 From 2655fffed7a9e765bcb4701dd876e9dab975f289 Mon Sep 17 00:00:00 2001 From: Samuel Thibault Date: Wed, 8 Jan 2020 00:58:48 +0100 Subject: [PATCH] tcp_emu: Fix oob access The main loop only checks for one available byte, while we sometimes need two bytes. --- CHANGELOG.md | 1 + src/tcp_subr.c | 7 +++++++ 2 files changed, 8 insertions(+) #diff --git a/CHANGELOG.md b/CHANGELOG.md #index 00d0ce2..5cf94a8 100644 #--- a/CHANGELOG.md #+++ b/CHANGELOG.md #@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0 # ### Fixed # # - ncsi: fix checksum OOB memory access #+ - `tcp_emu()`: fix OOB accesses # # ## [4.1.0] - 2019-12-02 # diff --git a/src/tcp_subr.c b/src/tcp_subr.c index 382aa38..9c1bdec 100644 --- a/slirp/src/tcp_subr.c +++ b/slirp/src/tcp_subr.c @@ -871,6 +871,9 @@ int tcp_emu(struct socket *so, struct mbuf *m) break; case 5: + if (bptr == m->m_data + m->m_len - 1) + return 1; /* We need two bytes */ + /* * The difference between versions 1.0 and * 2.0 is here. For future versions of @@ -886,6 +889,10 @@ int tcp_emu(struct socket *so, struct mbuf *m) /* This is the field containing the port * number that RA-player is listening to. */ + + if (bptr == m->m_data + m->m_len - 1) + return 1; /* We need two bytes */ + lport = (((uint8_t *)bptr)[0] << 8) + ((uint8_t *)bptr)[1]; if (lport < 6970) lport += 256; /* don't know why */ -- 2.24.1 From ce131029d6d4a405cb7d3ac6716d03e58fb4a5d9 Mon Sep 17 00:00:00 2001 From: Prasad J Pandit Date: Thu, 9 Jan 2020 15:12:27 +0530 Subject: [PATCH] slirp: use correct size while emulating IRC commands While emulating IRC DCC commands, tcp_emu() uses 'mbuf' size 'm->m_size' to write DCC commands via snprintf(3). This may lead to OOB write access, because 'bptr' points somewhere in the middle of 'mbuf' buffer, not at the start. Use M_FREEROOM(m) size to avoid OOB access. Reported-by: Vishnu Dev TJ Signed-off-by: Prasad J Pandit Reviewed-by: Samuel Thibault Message-Id: <20200109094228.79764-2-ppandit@redhat.com> --- src/tcp_subr.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/src/tcp_subr.c b/src/tcp_subr.c index 9c1bdec..ee7a938 100644 --- a/slirp/src/tcp_subr.c +++ b/slirp/src/tcp_subr.c @@ -763,7 +763,8 @@ 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", + 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); } else if (sscanf(bptr, "DCC SEND %256s %u %u %u", buff, &laddr, &lport, @@ -773,8 +774,8 @@ 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, + 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); } else if (sscanf(bptr, "DCC MOVE %256s %u %u %u", buff, &laddr, &lport, @@ -784,8 +785,8 @@ 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, + 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); } -- 2.24.1 From 82ebe9c370a0e2970fb5695aa19aa5214a6a1c80 Mon Sep 17 00:00:00 2001 From: Prasad J Pandit Date: Thu, 9 Jan 2020 15:12:28 +0530 Subject: [PATCH] slirp: use correct size while emulating commands While emulating services in tcp_emu(), it uses 'mbuf' size 'm->m_size' to write commands via snprintf(3). Use M_FREEROOM(m) size to avoid possible OOB access. Signed-off-by: Prasad J Pandit Signed-off-by: Samuel Thibault Message-Id: <20200109094228.79764-3-ppandit@redhat.com> --- src/tcp_subr.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/src/tcp_subr.c b/src/tcp_subr.c index ee7a938..177dfd2 100644 --- a/slirp/src/tcp_subr.c +++ b/slirp/src/tcp_subr.c @@ -681,7 +681,7 @@ 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, + 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 : ""); return 1; @@ -716,8 +716,7 @@ 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, + 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 : ""); @@ -743,8 +742,8 @@ 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 = snprintf(m->m_data, M_ROOM(m), + "%d", ntohs(so->so_fport)) + 1; return 1; case EMU_IRC: -- 2.24.1