/pidgin/main: 6436e14bdb9d: Add bounds checking when parsing emo...

Changeset: 6436e14bdb9d997dfd73cc7cea1b300c37fa401d
Author:	 Mark Doliner <[email protected]>
Date:	 2014-04-07 23:45 -0700
Branch:	 release-2.x.y
URL: https://hg.pidgin.im/pidgin/main/rev/6436e14bdb9d

Description:

Add bounds checking when parsing emoticon responses in MXit. This fixes
a potential remote crash when parsing a malformed emoticon response.
We'll need to get a CVE ID for this.

Discovered by Yves Younan and Richard Johnson of Sourcefire VRT. Thanks
to Sourcefire VRT for finding this and reporting it to us!

diffstat:

 ChangeLog                         |   7 +++++-
 libpurple/protocols/mxit/markup.c |  45 ++++++++++++++++++++++++++++++++------
 2 files changed, 43 insertions(+), 9 deletions(-)

diffs (166 lines):

diff --git a/ChangeLog b/ChangeLog
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,7 +3,7 @@ Pidgin and Finch: The Pimpin' Penguin IM
 version 2.10.10 (?/?/?):
 	Windows-Specific Changes:
 	* Don't allow overwriting arbitrary files on the file system when the
-	  user installs a smiley theme from a tar file. (Discovered by Yves
+	  user installs a smiley theme via drag-and-drop. (Discovered by Yves
 	  Younan of Sourcefire VRT)
 
 	Finch:
@@ -12,6 +12,11 @@ version 2.10.10 (?/?/?):
 	Gadu-Gadu:
 	* Updated internal libgadu to version 1.12.0-rc2.
 
+	MXit:
+	* Fix potential remote crash parsing a malformed emoticon response.
+	  (Discovered by Yves Younan and Richard Johnson of Sourcefire VRT)
+	  (CVE-2014-NNNN)
+
 version 2.10.9 (2/2/2014):
 	XMPP:
 	* Fix problems logging into some servers including jabber.org and
diff --git a/libpurple/protocols/mxit/markup.c b/libpurple/protocols/mxit/markup.c
--- a/libpurple/protocols/mxit/markup.c
+++ b/libpurple/protocols/mxit/markup.c
@@ -163,16 +163,22 @@ void mxit_add_html_link( struct RXMsgDat
  * Extract an ASN.1 formatted length field from the data.
  *
  *  @param data				The source data
+ *  @param data_len			Length of data
  *  @param size				The extracted length
  *  @return					The number of bytes extracted
  */
-static unsigned int asn_getlength( const gchar* data, int* size )
+static unsigned int asn_getlength( const gchar* data, gsize data_len, int* size )
 {
 	unsigned int	len		= 0;
 	unsigned char	bytes;
 	unsigned char	byte;
 	int				i;
 
+	if ( data_len < 1 ) {
+		/* missing first byte! */
+		return -1;
+	}
+
 	/* first byte specifies the number of bytes in the length */
 	bytes = ( data[0] & ~0x80 );
 	if ( bytes > sizeof( unsigned int ) ) {
@@ -181,6 +187,11 @@ static unsigned int asn_getlength( const
 	}
 	data++;
 
+	if ( data_len - 1 < bytes ) {
+		/* missing length! */
+		return -1;
+	}
+
 	/* parse out the actual length */
 	for ( i = 0; i < bytes; i++ ) {
 		byte = data[i];
@@ -197,15 +208,21 @@ static unsigned int asn_getlength( const
  * Extract an ASN.1 formatted UTF-8 string field from the data.
  *
  *  @param data				The source data
+ *  @param data_len			Length of data
  *  @param type				Expected type of string
  *  @param utf8				The extracted string.  Must be deallocated by caller.
  *  @return					The number of bytes extracted
  */
-static int asn_getUtf8( const gchar* data, gchar type, char** utf8 )
+static int asn_getUtf8( const gchar* data, gsize data_len, gchar type, char** utf8 )
 {
 	unsigned int len;
 	gchar *out_str;
 
+	if ( data_len < 2 ) {
+		/* missing type or length! */
+		return -1;
+	}
+
 	/* validate the field type [1 byte] */
 	if ( data[0] != type ) {
 		/* this is not a utf-8 string! */
@@ -214,6 +231,11 @@ static int asn_getUtf8( const gchar* dat
 	}
 
 	len = (guint8)data[1]; /* length field [1 byte] */
+	if ( data_len - 2 < len ) {
+		/* not enough bytes left in data! */
+		return -1;
+	}
+
 	out_str = g_malloc(len + 1);
 	memcpy(out_str, &data[2], len); /* data field */
 	out_str[len] = '\0';
@@ -500,7 +522,7 @@ static void emoticon_returned( PurpleUti
 #endif
 
 	/* validate that the returned data starts with the magic constant that indicates it is a custom emoticon */
-	if ( memcmp( MXIT_FRAME_MAGIC, &data[pos], strlen( MXIT_FRAME_MAGIC ) ) != 0 ) {
+	if ( len - pos < strlen( MXIT_FRAME_MAGIC ) || memcmp( MXIT_FRAME_MAGIC, &data[pos], strlen( MXIT_FRAME_MAGIC ) ) != 0 ) {
 		purple_debug_error( MXIT_PLUGIN_ID, "Invalid emoticon received from wapsite (bad magic)\n" );
 		goto done;
 	}
@@ -514,7 +536,7 @@ static void emoticon_returned( PurpleUti
 	pos++;
 
 	/* get the frame image data length */
-	res = asn_getlength( &data[pos], &em_size );
+	res = asn_getlength( &data[pos], len - pos, &em_size );
 	if ( res <= 0 ) {
 		purple_debug_error( MXIT_PLUGIN_ID, "Invalid emoticon received from wapsite (bad frame length)\n" );
 		goto done;
@@ -525,7 +547,7 @@ static void emoticon_returned( PurpleUti
 #endif
 
 	/* utf-8 (emoticon name) */
-	res = asn_getUtf8( &data[pos], 0x0C, &str );
+	res = asn_getUtf8( &data[pos], len - pos, 0x0C, &str );
 	if ( res <= 0 ) {
 		purple_debug_error( MXIT_PLUGIN_ID, "Invalid emoticon received from wapsite (bad name string)\n" );
 		goto done;
@@ -538,7 +560,7 @@ static void emoticon_returned( PurpleUti
 	str = NULL;
 
 	/* utf-8 (emoticon shortcut) */
-	res = asn_getUtf8( &data[pos], 0x81, &str );
+	res = asn_getUtf8( &data[pos], len - pos, 0x81, &str );
 	if ( res <= 0 ) {
 		purple_debug_error( MXIT_PLUGIN_ID, "Invalid emoticon received from wapsite (bad shortcut string)\n" );
 		goto done;
@@ -550,7 +572,7 @@ static void emoticon_returned( PurpleUti
 	em_id = str;
 
 	/* validate the image data type */
-	if ( data[pos] != '\x82' ) {
+	if ( len - pos < 1 || data[pos] != '\x82' ) {
 		purple_debug_error( MXIT_PLUGIN_ID, "Invalid emoticon received from wapsite (bad data type)\n" );
 		g_free( em_id );
 		goto done;
@@ -558,7 +580,7 @@ static void emoticon_returned( PurpleUti
 	pos++;
 
 	/* get the data length */
-	res = asn_getlength( &data[pos], &em_size );
+	res = asn_getlength( &data[pos], len - pos, &em_size );
 	if ( res <= 0 ) {
 		/* bad frame length */
 		purple_debug_error( MXIT_PLUGIN_ID, "Invalid emoticon received from wapsite (bad data length)\n" );
@@ -570,6 +592,13 @@ static void emoticon_returned( PurpleUti
 	purple_debug_info( MXIT_PLUGIN_ID, "read the length '%i'\n", em_size );
 #endif
 
+	if ( len - pos < em_size ) {
+		/* not enough bytes left in data! */
+		purple_debug_error( MXIT_PLUGIN_ID, "Invalid emoticon received from wapsite (data length too long)\n");
+		g_free( em_id );
+		goto done;
+	}
+
 	/* strip the mxit markup tags from the emoticon id (eg, .{XY} -> XY) */
 	if ( ( em_id[0] == '.' ) && ( em_id[1] == '{' ) ) {
 		char	emo[MXIT_MAX_EMO_ID + 1];