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Fix that ParseTcpOption doesn't work correctly

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Suppose there is a TCP SYN or SYN-ACK packet taking options as:
    02 04 05 b4 01 01 04 02 01 03 03 04 
which is 
Options: (12 bytes)
    >Maximum segment size: 1460 bytes
    >No-Operation (NOP)
    >No-Operation (NOP)
    >TCP SACK Permitted Option: True
    >No-Operation (NOP)
    >Window scale: 4 (multiply by 16)

Then the original parse function only returns MSS 1460 while WSS is 0.
This commit is contained in:
ajeecai 2016-08-04 17:33:18 +08:00 committed by GitHub
parent 1e17c9bcfd
commit 9bc67cc293
1 changed files with 12 additions and 6 deletions
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18
src/Cedar/Virtual.c
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@ -5429,7 +5429,7 @@ SCAN_FIRST:
void ParseTcpOption(TCP_OPTION *o, void *data, UINT size)
{
UCHAR *buf = (UCHAR *)data;
UINT i;
UINT i = 0;
UINT value_size = 0;
UINT value_id = 0;
UCHAR value[128];
@ -5441,13 +5441,18 @@ void ParseTcpOption(TCP_OPTION *o, void *data, UINT size)
Zero(o, sizeof(TCP_OPTION));
for (i = 0;i < size;i++)
while(i < size)
{
if (buf[i] == 0)
{
return;
}
if (buf[i] != 1)
else if (buf[i] == 1)
{
i++;
continue;
}
else
{
value_id = buf[i];
i++;
@ -5466,12 +5471,14 @@ void ParseTcpOption(TCP_OPTION *o, void *data, UINT size)
return;
}
value_size -= 2;
Copy(value, &buf[i], value_size);
i += value_size;
if (i >= size)
if (i > size)
{
return;
}
switch (value_id)
{
case 2: // MSS
@ -5486,14 +5493,13 @@ void ParseTcpOption(TCP_OPTION *o, void *data, UINT size)
if (value_size == 1)
{
UCHAR *wss = (UCHAR *)value;
o->WindowScaling = Endian16(*wss);
o->WindowScaling = *wss;
}
break;
}
}
}
}
// Create a new NAT TCP session