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From 1ea36437bb4b0f3ac42db5222cd7311363fa6ec9 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/misc.c | 37 +++++++++++++++++++++++
src/misc.h | 10 +++++++
src/packet.c | 84 ++++++++++++++++++++++++----------------------------
3 files changed, 85 insertions(+), 46 deletions(-)
diff --git a/src/misc.c b/src/misc.c
index f7faae7..1b2682f 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -643,3 +643,40 @@ void *_libssh2_calloc(LIBSSH2_SESSION* session, size_t size)
}
return p;
}
+
+int _libssh2_check_length(struct string_buf *buf, size_t len)
+{
+ unsigned char *endp = &buf->data[buf->len];
+ size_t left = endp - buf->dataptr;
+ return ((len <= left) && (left <= buf->len));
+}
+
+int _libssh2_get_u32(struct string_buf *buf, uint32_t *out)
+{
+ if(!_libssh2_check_length(buf, 4)) {
+ return -1;
+ }
+
+ *out = _libssh2_ntohu32(buf->dataptr);
+ buf->dataptr += 4;
+ return 0;
+}
+
+int _libssh2_get_string(struct string_buf *buf, unsigned char **outbuf,
+ size_t *outlen)
+{
+ uint32_t data_len;
+ if(_libssh2_get_u32(buf, &data_len) != 0) {
+ return -1;
+ }
+ if(!_libssh2_check_length(buf, data_len)) {
+ return -1;
+ }
+ *outbuf = buf->dataptr;
+ buf->dataptr += data_len;
+
+ if(outlen)
+ *outlen = (size_t)data_len;
+
+ return 0;
+}
diff --git a/src/misc.h b/src/misc.h
index 54ae546..cf5abb5 100644
--- a/src/misc.h
+++ b/src/misc.h
@@ -49,6 +49,12 @@ struct list_node {
struct list_head *head;
};
+struct string_buf {
+ unsigned char *data;
+ unsigned char *dataptr;
+ size_t len;
+};
+
int _libssh2_error_flags(LIBSSH2_SESSION* session, int errcode, const char* errmsg, int errflags);
int _libssh2_error(LIBSSH2_SESSION* session, int errcode, const char* errmsg);
@@ -80,6 +86,10 @@ void _libssh2_store_u32(unsigned char **buf, uint32_t value);
void _libssh2_store_str(unsigned char **buf, const char *str, size_t len);
void *_libssh2_calloc(LIBSSH2_SESSION* session, size_t size);
+int _libssh2_get_u32(struct string_buf *buf, uint32_t *out);
+int _libssh2_get_string(struct string_buf *buf, unsigned char **outbuf,
+ size_t *outlen);
+
#if defined(LIBSSH2_WIN32) && !defined(__MINGW32__) && !defined(__CYGWIN__)
/* provide a private one */
#undef HAVE_GETTIMEOFDAY
diff --git a/src/packet.c b/src/packet.c
index c950b5d..f180b77 100644
--- a/src/packet.c
+++ b/src/packet.c
@@ -416,10 +416,10 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
size_t datalen, int macstate)
{
int rc = 0;
- char *message=NULL;
- char *language=NULL;
- size_t message_len=0;
- size_t language_len=0;
+ unsigned char *message = NULL;
+ unsigned char *language = NULL;
+ size_t message_len = 0;
+ size_t language_len = 0;
LIBSSH2_CHANNEL *channelp = NULL;
size_t data_head = 0;
unsigned char msg = data[0];
@@ -430,7 +430,7 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
"Packet type %d received, length=%d",
(int) msg, (int) datalen);
- if ((macstate == LIBSSH2_MAC_INVALID) &&
+ if((macstate == LIBSSH2_MAC_INVALID) &&
(!session->macerror ||
LIBSSH2_MACERROR(session, (char *) data, datalen))) {
/* Bad MAC input, but no callback set or non-zero return from the
@@ -456,9 +456,9 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
break;
}
- if (session->packAdd_state == libssh2_NB_state_allocated) {
+ if(session->packAdd_state == libssh2_NB_state_allocated) {
/* A couple exceptions to the packet adding rule: */
- switch (msg) {
+ switch(msg) {
/*
byte SSH_MSG_DISCONNECT
@@ -469,32 +469,23 @@ _libssh2_packet_add(LIBSSH2_SESSION * session, unsigned char *data,
case SSH_MSG_DISCONNECT:
if(datalen >= 5) {
- size_t reason = _libssh2_ntohu32(data + 1);
-
- if(datalen >= 9) {
- message_len = _libssh2_ntohu32(data + 5);
-
- 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);
+ 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 */
+
+ _libssh2_get_u32(&buf, &reason);
+ _libssh2_get_string(&buf, &message, &message_len);
+ _libssh2_get_string(&buf, &language, &language_len);
+
+ if(session->ssh_msg_disconnect) {
+ 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);
@@ -534,23 +525,24 @@ _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);
+ if(session->ssh_msg_debug) {
+ 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
@@ -573,7 +565,7 @@ _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
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