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Resolves: CVE-2019-17498 - fix integer overflow in SSH_MSG_DISCONNECT logic

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This commit is contained in:
Kamil Dudka 2019-10-30 18:23:36 +01:00
parent 3d9150262d
commit 41525baf3f
2 changed files with 138 additions and 1 deletions
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130
0001-libssh2-1.9.0-CVE-2019-17498.patch Normal file
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@ -0,0 +1,130 @@
From a1554e78e15fc0daeb574c3dd5c87654469a3742 Mon Sep 17 00:00:00 2001
From: Will Cosgrove <will@panic.com>
Date: Fri, 30 Aug 2019 09:57:38 -0700
Subject: [PATCH] packet.c: improve message parsing (#402)
* packet.c: improve parsing of packets
file: packet.c
notes:
Use _libssh2_get_string API in SSH_MSG_DEBUG/SSH_MSG_DISCONNECT. Additional uint32 bounds check in SSH_MSG_GLOBAL_REQUEST.
Upstream-commit: dedcbd106f8e52d5586b0205bc7677e4c9868f9c
Signed-off-by: Kamil Dudka <kdudka@redhat.com>
---
src/packet.c | 68 ++++++++++++++++++++++------------------------------
1 file changed, 29 insertions(+), 39 deletions(-)
diff --git a/src/packet.c b/src/packet.c
index 38ab629..2e01bfc 100644
--- a/src/packet.c
+++ b/src/packet.c
@@ -419,8 +419,8 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
size_t datalen, int macstate)
{
int rc = 0;
- char *message = NULL;
- char *language = NULL;
+ unsigned char *message = NULL;
+ unsigned char *language = NULL;
size_t message_len = 0;
size_t language_len = 0;
LIBSSH2_CHANNEL *channelp = NULL;
@@ -472,33 +472,23 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
case SSH_MSG_DISCONNECT:
if(datalen >= 5) {
- size_t reason = _libssh2_ntohu32(data + 1);
+ uint32_t reason = 0;
+ struct string_buf buf;
+ buf.data = (unsigned char *)data;
+ buf.dataptr = buf.data;
+ buf.len = datalen;
+ buf.dataptr++; /* advance past type */
- if(datalen >= 9) {
- message_len = _libssh2_ntohu32(data + 5);
+ _libssh2_get_u32(&buf, &reason);
+ _libssh2_get_string(&buf, &message, &message_len);
+ _libssh2_get_string(&buf, &language, &language_len);
- if(message_len < datalen-13) {
- /* 9 = packet_type(1) + reason(4) + message_len(4) */
- message = (char *) data + 9;
-
- language_len =
- _libssh2_ntohu32(data + 9 + message_len);
- language = (char *) data + 9 + message_len + 4;
-
- if(language_len > (datalen-13-message_len)) {
- /* bad input, clear info */
- language = message = NULL;
- language_len = message_len = 0;
- }
- }
- else
- /* bad size, clear it */
- message_len = 0;
- }
if(session->ssh_msg_disconnect) {
- LIBSSH2_DISCONNECT(session, reason, message,
- message_len, language, language_len);
+ LIBSSH2_DISCONNECT(session, reason, (const char *)message,
+ message_len, (const char *)language,
+ language_len);
}
+
_libssh2_debug(session, LIBSSH2_TRACE_TRANS,
"Disconnect(%d): %s(%s)", reason,
message, language);
@@ -539,24 +529,24 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
int always_display = data[1];
if(datalen >= 6) {
- message_len = _libssh2_ntohu32(data + 2);
-
- if(message_len <= (datalen - 10)) {
- /* 6 = packet_type(1) + display(1) + message_len(4) */
- message = (char *) data + 6;
- language_len = _libssh2_ntohu32(data + 6 +
- message_len);
-
- if(language_len <= (datalen - 10 - message_len))
- language = (char *) data + 10 + message_len;
- }
+ struct string_buf buf;
+ buf.data = (unsigned char *)data;
+ buf.dataptr = buf.data;
+ buf.len = datalen;
+ buf.dataptr += 2; /* advance past type & always display */
+
+ _libssh2_get_string(&buf, &message, &message_len);
+ _libssh2_get_string(&buf, &language, &language_len);
}
if(session->ssh_msg_debug) {
- LIBSSH2_DEBUG(session, always_display, message,
- message_len, language, language_len);
+ LIBSSH2_DEBUG(session, always_display,
+ (const char *)message,
+ message_len, (const char *)language,
+ language_len);
}
}
+
/*
* _libssh2_debug will actually truncate this for us so
* that it's not an inordinate about of data
@@ -579,7 +569,7 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
uint32_t len = 0;
unsigned char want_reply = 0;
len = _libssh2_ntohu32(data + 1);
- if(datalen >= (6 + len)) {
+ if((len <= (UINT_MAX - 6)) && (datalen >= (6 + len))) {
want_reply = data[5 + len];
_libssh2_debug(session,
LIBSSH2_TRACE_CONN,
--
2.20.1

9
libssh2.spec
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@ -1,11 +1,14 @@
Name: libssh2
Version: 1.9.0
Release: 2%{?dist}
Release: 3%{?dist}
Summary: A library implementing the SSH2 protocol
License: BSD
URL: http://www.libssh2.org/
Source0: http://libssh2.org/download/libssh2-%{version}.tar.gz
# fix integer overflow in SSH_MSG_DISCONNECT logic (CVE-2019-17498)
Patch1: 0001-libssh2-1.9.0-CVE-2019-17498.patch
BuildRequires: coreutils
BuildRequires: findutils
BuildRequires: gcc
@ -48,6 +51,7 @@ developing applications that use libssh2.
%prep
%setup -q
%patch1 -p1
# Replace hard wired port number in the test suite to avoid collisions
# between 32-bit and 64-bit builds running on a single build-host
@ -111,6 +115,9 @@ LC_ALL=en_US.UTF-8 make -C tests check
%{_libdir}/pkgconfig/libssh2.pc
%changelog
* Wed Oct 30 2019 Kamil Dudka <kdudka@redhat.com> - 1.9.0-3
- fix integer overflow in SSH_MSG_DISCONNECT logic (CVE-2019-17498)
* Thu Jul 25 2019 Fedora Release Engineering <releng@fedoraproject.org> - 1.9.0-2
- Rebuilt for https://fedoraproject.org/wiki/Fedora_31_Mass_Rebuild