8d76402ee1
In libssh2 v1.9.0 and earlier versions, the SSH_MSG_DISCONNECT logic in packet.c has an integer overflow in a bounds check, enabling an attacker to specify an arbitrary (out-of-bounds) offset for a subsequent memory read. A crafted SSH server may be able to disclose sensitive information or cause a denial of service condition on the client system when a user connects to the server. Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com> Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
128 lines
5.5 KiB
Diff
128 lines
5.5 KiB
Diff
From dedcbd106f8e52d5586b0205bc7677e4c9868f9c Mon Sep 17 00:00:00 2001
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From: Will Cosgrove <will@panic.com>
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Date: Fri, 30 Aug 2019 09:57:38 -0700
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Subject: [PATCH] packet.c: improve message parsing (#402)
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* packet.c: improve parsing of packets
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file: packet.c
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notes:
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Use _libssh2_get_string API in SSH_MSG_DEBUG/SSH_MSG_DISCONNECT. Additional uint32 bounds check in SSH_MSG_GLOBAL_REQUEST.
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[Retrieved from:
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https://github.com/libssh2/libssh2/commit/dedcbd106f8e52d5586b0205bc7677e4c9868f9c]
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Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
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---
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src/packet.c | 68 ++++++++++++++++++++++------------------------------
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1 file changed, 29 insertions(+), 39 deletions(-)
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diff --git a/src/packet.c b/src/packet.c
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index 38ab6294..2e01bfc5 100644
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--- a/src/packet.c
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+++ b/src/packet.c
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@@ -419,8 +419,8 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
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size_t datalen, int macstate)
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{
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int rc = 0;
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- char *message = NULL;
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- char *language = NULL;
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+ unsigned char *message = NULL;
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+ unsigned char *language = NULL;
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size_t message_len = 0;
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size_t language_len = 0;
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LIBSSH2_CHANNEL *channelp = NULL;
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@@ -472,33 +472,23 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
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case SSH_MSG_DISCONNECT:
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if(datalen >= 5) {
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- size_t reason = _libssh2_ntohu32(data + 1);
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+ uint32_t reason = 0;
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+ struct string_buf buf;
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+ buf.data = (unsigned char *)data;
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+ buf.dataptr = buf.data;
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+ buf.len = datalen;
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+ buf.dataptr++; /* advance past type */
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- if(datalen >= 9) {
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- message_len = _libssh2_ntohu32(data + 5);
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+ _libssh2_get_u32(&buf, &reason);
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+ _libssh2_get_string(&buf, &message, &message_len);
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+ _libssh2_get_string(&buf, &language, &language_len);
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- if(message_len < datalen-13) {
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- /* 9 = packet_type(1) + reason(4) + message_len(4) */
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- message = (char *) data + 9;
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-
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- language_len =
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- _libssh2_ntohu32(data + 9 + message_len);
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- language = (char *) data + 9 + message_len + 4;
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-
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- if(language_len > (datalen-13-message_len)) {
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- /* bad input, clear info */
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- language = message = NULL;
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- language_len = message_len = 0;
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- }
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- }
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- else
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- /* bad size, clear it */
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- message_len = 0;
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- }
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if(session->ssh_msg_disconnect) {
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- LIBSSH2_DISCONNECT(session, reason, message,
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- message_len, language, language_len);
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+ LIBSSH2_DISCONNECT(session, reason, (const char *)message,
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+ message_len, (const char *)language,
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+ language_len);
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}
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+
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_libssh2_debug(session, LIBSSH2_TRACE_TRANS,
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"Disconnect(%d): %s(%s)", reason,
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message, language);
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@@ -539,24 +529,24 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
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int always_display = data[1];
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if(datalen >= 6) {
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- message_len = _libssh2_ntohu32(data + 2);
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-
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- if(message_len <= (datalen - 10)) {
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- /* 6 = packet_type(1) + display(1) + message_len(4) */
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- message = (char *) data + 6;
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- language_len = _libssh2_ntohu32(data + 6 +
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- message_len);
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-
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- if(language_len <= (datalen - 10 - message_len))
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- language = (char *) data + 10 + message_len;
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- }
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+ struct string_buf buf;
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+ buf.data = (unsigned char *)data;
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+ buf.dataptr = buf.data;
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+ buf.len = datalen;
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+ buf.dataptr += 2; /* advance past type & always display */
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+
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+ _libssh2_get_string(&buf, &message, &message_len);
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+ _libssh2_get_string(&buf, &language, &language_len);
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}
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if(session->ssh_msg_debug) {
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- LIBSSH2_DEBUG(session, always_display, message,
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- message_len, language, language_len);
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+ LIBSSH2_DEBUG(session, always_display,
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+ (const char *)message,
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+ message_len, (const char *)language,
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+ language_len);
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}
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}
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+
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/*
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* _libssh2_debug will actually truncate this for us so
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* that it's not an inordinate about of data
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@@ -579,7 +569,7 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
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uint32_t len = 0;
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unsigned char want_reply = 0;
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len = _libssh2_ntohu32(data + 1);
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- if(datalen >= (6 + len)) {
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+ if((len <= (UINT_MAX - 6)) && (datalen >= (6 + len))) {
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want_reply = data[5 + len];
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_libssh2_debug(session,
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LIBSSH2_TRACE_CONN,
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