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Handle extending EDNS0 OPT RR.

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This commit is contained in:
Simon Kelley
2015-12-21 16:23:47 +00:00
parent 1d03016bbc
commit 5bb88f0963
4 changed files with 81 additions and 56 deletions
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115
src/edns0.c
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@@ -16,12 +16,12 @@
#include "dnsmasq.h"
unsigned char *find_pseudoheader(struct dns_header *header, size_t plen, size_t *len, unsigned char **p, int *is_sign)
unsigned char *find_pseudoheader(struct dns_header *header, size_t plen, size_t *len, unsigned char **p, int *is_sign, int *is_last)
{
/* See if packet has an RFC2671 pseudoheader, and if so return a pointer to it.
also return length of pseudoheader in *len and pointer to the UDP size in *p
Finally, check to see if a packet is signed. If it is we cannot change a single bit before
forwarding. We look for SIG and TSIG in the addition section, and TKEY queries (for GSS-TSIG) */
forwarding. We look for TSIG in the addition section, and TKEY queries (for GSS-TSIG) */
int i, arcount = ntohs(header->arcount);
unsigned char *ansp = (unsigned char *)(header+1);
@@ -76,8 +76,13 @@ unsigned char *find_pseudoheader(struct dns_header *header, size_t plen, size_t
{
if (len)
*len = ansp - start;
if (p)
*p = save;
if (is_last)
*is_last = (i == arcount-1);
ret = start;
}
else if (is_sign &&
@@ -100,50 +105,31 @@ struct macparm {
size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *limit,
unsigned short udp_sz, int optno, unsigned char *opt, size_t optlen, int set_do)
{
unsigned char *lenp, *datap, *p;
int rdlen, is_sign;
if (!(p = find_pseudoheader(header, plen, NULL, NULL, &is_sign)))
{
if (is_sign)
return plen;
unsigned char *lenp, *datap, *p, *udp_len, *buff = NULL;
int rdlen = 0, is_sign, is_last;
unsigned short flags = set_do ? 0x8000 : 0, rcode = 0;
/* We are adding the pseudoheader */
if (!(p = skip_questions(header, plen)) ||
!(p = skip_section(p,
ntohs(header->ancount) + ntohs(header->nscount) + ntohs(header->arcount),
header, plen)))
return plen;
*p++ = 0; /* empty name */
PUTSHORT(T_OPT, p);
PUTSHORT(udp_sz, p); /* max packet length, 512 if not given in EDNS0 header */
PUTSHORT(0, p); /* extended RCODE and version */
PUTSHORT(set_do ? 0x8000 : 0, p); /* DO flag */
lenp = p;
PUTSHORT(0, p); /* RDLEN */
rdlen = 0;
if (((ssize_t)optlen) > (limit - (p + 4)))
return plen; /* Too big */
header->arcount = htons(ntohs(header->arcount) + 1);
datap = p;
}
else
p = find_pseudoheader(header, plen, NULL, &udp_len, &is_sign, &is_last);
if (is_sign)
return plen;
if (p)
{
/* Existing header */
int i;
unsigned short code, len, flags;
/* Must be at the end, if exists */
if (ntohs(header->arcount) != 1 ||
is_sign ||
(!(p = skip_name(p, header, plen, 10))))
return plen;
p += 6; /* skip UDP length and RCODE */
unsigned short code, len;
p = udp_len;
GETSHORT(udp_sz, p);
GETSHORT(rcode, p);
GETSHORT(flags, p);
if (set_do)
{
p -=2;
PUTSHORT(flags | 0x8000, p);
flags |= 0x8000;
PUTSHORT(flags, p);
}
lenp = p;
@@ -165,22 +151,61 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
return plen;
p += len;
}
if (((ssize_t)optlen) > (limit - (p + 4)))
return plen; /* Too big */
/* If we're going to extend the RR, it has to be the last RR in the packet */
if (!is_last)
{
/* First, take a copy of the options. */
if (rdlen != 0 && (buff = whine_malloc(rdlen)))
memcpy(buff, datap, rdlen);
/* now, delete OPT RR */
plen = rrfilter(header, plen, 0);
/* Now, force addition of a new one */
p = NULL;
}
}
if (!p)
{
/* We are (re)adding the pseudoheader */
if (!(p = skip_questions(header, plen)) ||
!(p = skip_section(p,
ntohs(header->ancount) + ntohs(header->nscount) + ntohs(header->arcount),
header, plen)))
return plen;
*p++ = 0; /* empty name */
PUTSHORT(T_OPT, p);
PUTSHORT(udp_sz, p); /* max packet length, 512 if not given in EDNS0 header */
PUTSHORT(rcode, p); /* extended RCODE and version */
PUTSHORT(flags, p); /* DO flag */
lenp = p;
PUTSHORT(rdlen, p); /* RDLEN */
datap = p;
/* Copy back any options */
if (buff)
{
memcpy(p, buff, rdlen);
free(buff);
p += rdlen;
}
header->arcount = htons(ntohs(header->arcount) + 1);
}
if (((ssize_t)optlen) > (limit - (p + 4)))
return plen; /* Too big */
/* Add new option */
if (optno != 0)
{
PUTSHORT(optno, p);
PUTSHORT(optlen, p);
memcpy(p, opt, optlen);
p += optlen;
PUTSHORT(p - datap, lenp);
}
PUTSHORT(p - datap, lenp);
return p - (unsigned char *)header;
}
static int filter_mac(int family, char *addrp, char *mac, size_t maclen, void *parmv)