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Extend stop-dns-rebind to reject IPv6 LL and ULA addresses.

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We also reject the loopback address if rebind-localhost-ok is NOT set.

Signed-off-by: DL6ER <dl6er@dl6er.de>
This commit is contained in:
Dominik DL6ER
2020-03-17 22:59:17 +00:00
committed by Simon Kelley
parent 63ed917ad9
commit e7ee1aa093
2 changed files with 26 additions and 10 deletions
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8
man/dnsmasq.8
View File

@@ -395,11 +395,13 @@ were previously disabled.
.TP
.B --stop-dns-rebind
Reject (and log) addresses from upstream nameservers which are in the
private IP ranges. This blocks an attack where a browser behind a
firewall is used to probe machines on the local network.
private ranges. This blocks an attack where a browser behind a
firewall is used to probe machines on the local network. For IPv6, the
private range covers the IPv4-mapped addresses in private space plus
all link-local (LL) and site-local (ULA) addresses.
.TP
.B --rebind-localhost-ok
Exempt 127.0.0.0/8 from rebinding checks. This address range is
Exempt 127.0.0.0/8 and ::1 from rebinding checks. This address range is
returned by realtime black hole servers, so blocking it may disable
these services.
.TP

24
src/rfc1035.c
View File

@@ -844,12 +844,26 @@ int extract_addresses(struct dns_header *header, size_t qlen, char *name, time_t
private_net(addr.addr4, !option_bool(OPT_LOCAL_REBIND)))
return 1;
if ((flags & F_IPV6) &&
IN6_IS_ADDR_V4MAPPED(&addr.addr6))
/* Block IPv4-mapped IPv6 addresses in private IPv4 address space */
if (flags & F_IPV6)
{
struct in_addr v4;
v4.s_addr = ((const uint32_t *) (&addr.addr6))[3];
if (private_net(v4, !option_bool(OPT_LOCAL_REBIND)))
if (IN6_IS_ADDR_V4MAPPED(&addr.addr6))
{
struct in_addr v4;
v4.s_addr = ((const uint32_t *) (&addr.addr6))[3];
if (private_net(v4, !option_bool(OPT_LOCAL_REBIND)))
return 1;
}
/* Check for link-local (LL) and site-local (ULA) IPv6 addresses */
if (IN6_IS_ADDR_LINKLOCAL(&addr.addr6) ||
IN6_IS_ADDR_SITELOCAL(&addr.addr6))
return 1;
/* Check for the IPv6 loopback address (::1) when
option rebind-localhost-ok is NOT set */
if (!option_bool(OPT_LOCAL_REBIND) &&
IN6_IS_ADDR_LOOPBACK(&addr.addr6))
return 1;
}
}