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Date: Wed, 16 Sep 2015 17:40:11 +0800
From: Qinghao Tang <luodalongde@...il.com>
To: secalert@...hat.com, oss-security@...ts.openwall.com
Subject: CVE-2015-5155 - openslp 1.2.1 ParseExtension() DoS vulnerability
HI there,
Greeting! This is Qinghao Tang from QIHU 360 company, China. I am a
security researcher there.I'm writing to report a vulnerability in openslp.
The function ParseExtension() in openslp 1.2.1 exists a vulnerability , an
attacher can cause a denial of service (infinite loop) via a packet with
crafted "nextoffset" value and "extid" value.
Let`s see how this issue happened,the code below is from
/openslp-1.2.1/common/slp_message.c:
/*--------------------------------------------------------------------------*/
int ParseExtension(SLPBuffer buffer, SLPMessage message)
/* Parse extensions *after* all standard protocol fields are parsed
*/
/*--------------------------------------------------------------------------*/
{
int extid;
int nextoffset;
int result = SLP_ERROR_OK;
nextoffset = message->header.extoffset;
while(nextoffset)
{
//here,buffer->start value is stable ,and we can
control nextoffset,so we can control buffer->curpos
buffer->curpos = buffer->start + nextoffset;
if(buffer->curpos + 5 >= buffer->end)
{
/* Extension takes us past the end of the buffer */
result = SLP_ERROR_PARSE_ERROR;
goto CLEANUP;
}
extid = AsUINT16(buffer->curpos);
buffer->curpos += 2;
//here,wo can control nextoffset by make a crafted packet
nextoffset = AsUINT24(buffer->curpos);
buffer->curpos += 3;
switch(extid)
{
case SLP_EXTENSION_ID_REG_PID:
if(message->header.functionid == SLP_FUNCT_SRVREG)
{
/* check to see if buffer is large enough to contain the 4
byte pid */
if(buffer->curpos + 4 > buffer->end)
{
result = SLP_ERROR_PARSE_ERROR;
goto CLEANUP;
}
message->body.srvreg.pid = AsUINT32(buffer->curpos);
buffer->curpos += 4;
}
break;
default:
if (extid >= 0x4000 && extid <= 0x7FFF )
{
/* This is a required extension. We better error out */
result = SLP_ERROR_MESSAGE_NOT_SUPPORTED;
goto CLEANUP;
}
break;
}
}
CLEANUP:
return result;
}
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