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. 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> 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> --- CHANGELOG.md | 1 + src/tcp_subr.c | 7 +++++++ 2 files changed, 8 insertions(+) diff -up ./slirp4netns-21fdece2737dc24ffa3f01a341b8a6854f8b13b4/vendor/libslirp/src/tcp_subr.c.CVE-2020-7039 ./slirp4netns-21fdece2737dc24ffa3f01a341b8a6854f8b13b4/vendor/libslirp/src/tcp_subr.c --- slirp4netns-21fdece2737dc24ffa3f01a341b8a6854f8b13b4/vendor/libslirp/src/tcp_subr.c.CVE-2020-7039 2020-01-16 11:13:43.472696979 +0100 +++ slirp4netns-21fdece2737dc24ffa3f01a341b8a6854f8b13b4/vendor/libslirp/src/tcp_subr.c 2020-01-16 11:13:43.474697002 +0100 @@ -692,7 +692,7 @@ int tcp_emu(struct socket *so, struct mb 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; @@ -727,8 +727,7 @@ int tcp_emu(struct socket *so, struct mb 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 : ""); @@ -754,8 +753,8 @@ int tcp_emu(struct socket *so, struct mb 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: @@ -774,7 +773,8 @@ int tcp_emu(struct socket *so, struct mb 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, @@ -784,8 +784,8 @@ int tcp_emu(struct socket *so, struct mb 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, @@ -795,8 +795,8 @@ int tcp_emu(struct socket *so, struct mb 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); } @@ -882,6 +882,9 @@ int tcp_emu(struct socket *so, struct mb 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 @@ -897,6 +900,10 @@ int tcp_emu(struct socket *so, struct mb /* 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 */