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Fix some pointer arithmetic in build_icmp_raw. There were two bugs. The

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first is a pointer was kept to the beginning of the packet payload, and
it was increased based on the varying size of the ICMP header. But its
type was pointer to u32 instead of pointer to u8, so the expression
datastart += 12 actually increased the pointer by 48 bytes, leaving
garbage in the first 36 bytes of the payload and making it possible for
the buffer to overflow. The second was that the remaining space left in
the buffer was not decreased when the datastart was increased, again
making it possible to overflow. I got a reliable segmentation fault with
the command
nmap -PP 1.2.3.4 --data-length 1480
This commit is contained in:
david
2009-08-29 01:45:28 +00:00
parent 3c14c0d7b1
commit 02c9cf42f7
1 changed files with 5 additions and 3 deletions
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8
tcpip.cc
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@@ -1493,7 +1493,9 @@ struct ppkt {
u16 seq;
u8 data[1500]; /* Note -- first 4-12 bytes can be used for ICMP header */
} pingpkt;
u32 *datastart = (u32 *) pingpkt.data;
u8 *datastart = pingpkt.data;
/* dlen is the amount of space remaining in the data buffer; it may be reduced
depending on type. */
int dlen = sizeof(pingpkt.data);
int icmplen=0;
char *ping = (char *) &pingpkt;
@@ -1507,11 +1509,11 @@ char *ping = (char *) &pingpkt;
icmplen = 20;
memset(datastart, 0, 12);
datastart += 12;
//datalen -= 12;
dlen -= 12;
} else if (ptype == 17 && pcode == 0) /* icmp netmask req */ {
icmplen = 12;
*datastart++ = 0;
//datalen -= 4;
dlen -= 4;
} else
fatal("Unknown icmp type/code (%d/%d) in %s", ptype, pcode, __func__);