mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 09:19:51 +00:00
![Jonathan Lemon](/assets/img/avatar_default.png)
ipv6_find_hdr() prints a non-rate limited error message when it cannot find an ipv6 header at a specific offset. This could be used as a DoS, so just remove it. Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
280 lines
7.5 KiB
C
280 lines
7.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* IPv6 library code, needed by static components when full IPv6 support is
|
|
* not configured or static.
|
|
*/
|
|
#include <linux/export.h>
|
|
#include <net/ipv6.h>
|
|
|
|
/*
|
|
* find out if nexthdr is a well-known extension header or a protocol
|
|
*/
|
|
|
|
bool ipv6_ext_hdr(u8 nexthdr)
|
|
{
|
|
/*
|
|
* find out if nexthdr is an extension header or a protocol
|
|
*/
|
|
return (nexthdr == NEXTHDR_HOP) ||
|
|
(nexthdr == NEXTHDR_ROUTING) ||
|
|
(nexthdr == NEXTHDR_FRAGMENT) ||
|
|
(nexthdr == NEXTHDR_AUTH) ||
|
|
(nexthdr == NEXTHDR_NONE) ||
|
|
(nexthdr == NEXTHDR_DEST);
|
|
}
|
|
EXPORT_SYMBOL(ipv6_ext_hdr);
|
|
|
|
/*
|
|
* Skip any extension headers. This is used by the ICMP module.
|
|
*
|
|
* Note that strictly speaking this conflicts with RFC 2460 4.0:
|
|
* ...The contents and semantics of each extension header determine whether
|
|
* or not to proceed to the next header. Therefore, extension headers must
|
|
* be processed strictly in the order they appear in the packet; a
|
|
* receiver must not, for example, scan through a packet looking for a
|
|
* particular kind of extension header and process that header prior to
|
|
* processing all preceding ones.
|
|
*
|
|
* We do exactly this. This is a protocol bug. We can't decide after a
|
|
* seeing an unknown discard-with-error flavour TLV option if it's a
|
|
* ICMP error message or not (errors should never be send in reply to
|
|
* ICMP error messages).
|
|
*
|
|
* But I see no other way to do this. This might need to be reexamined
|
|
* when Linux implements ESP (and maybe AUTH) headers.
|
|
* --AK
|
|
*
|
|
* This function parses (probably truncated) exthdr set "hdr".
|
|
* "nexthdrp" initially points to some place,
|
|
* where type of the first header can be found.
|
|
*
|
|
* It skips all well-known exthdrs, and returns pointer to the start
|
|
* of unparsable area i.e. the first header with unknown type.
|
|
* If it is not NULL *nexthdr is updated by type/protocol of this header.
|
|
*
|
|
* NOTES: - if packet terminated with NEXTHDR_NONE it returns NULL.
|
|
* - it may return pointer pointing beyond end of packet,
|
|
* if the last recognized header is truncated in the middle.
|
|
* - if packet is truncated, so that all parsed headers are skipped,
|
|
* it returns NULL.
|
|
* - First fragment header is skipped, not-first ones
|
|
* are considered as unparsable.
|
|
* - Reports the offset field of the final fragment header so it is
|
|
* possible to tell whether this is a first fragment, later fragment,
|
|
* or not fragmented.
|
|
* - ESP is unparsable for now and considered like
|
|
* normal payload protocol.
|
|
* - Note also special handling of AUTH header. Thanks to IPsec wizards.
|
|
*
|
|
* --ANK (980726)
|
|
*/
|
|
|
|
int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp,
|
|
__be16 *frag_offp)
|
|
{
|
|
u8 nexthdr = *nexthdrp;
|
|
|
|
*frag_offp = 0;
|
|
|
|
while (ipv6_ext_hdr(nexthdr)) {
|
|
struct ipv6_opt_hdr _hdr, *hp;
|
|
int hdrlen;
|
|
|
|
if (nexthdr == NEXTHDR_NONE)
|
|
return -1;
|
|
hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
|
|
if (!hp)
|
|
return -1;
|
|
if (nexthdr == NEXTHDR_FRAGMENT) {
|
|
__be16 _frag_off, *fp;
|
|
fp = skb_header_pointer(skb,
|
|
start+offsetof(struct frag_hdr,
|
|
frag_off),
|
|
sizeof(_frag_off),
|
|
&_frag_off);
|
|
if (!fp)
|
|
return -1;
|
|
|
|
*frag_offp = *fp;
|
|
if (ntohs(*frag_offp) & ~0x7)
|
|
break;
|
|
hdrlen = 8;
|
|
} else if (nexthdr == NEXTHDR_AUTH)
|
|
hdrlen = ipv6_authlen(hp);
|
|
else
|
|
hdrlen = ipv6_optlen(hp);
|
|
|
|
nexthdr = hp->nexthdr;
|
|
start += hdrlen;
|
|
}
|
|
|
|
*nexthdrp = nexthdr;
|
|
return start;
|
|
}
|
|
EXPORT_SYMBOL(ipv6_skip_exthdr);
|
|
|
|
int ipv6_find_tlv(const struct sk_buff *skb, int offset, int type)
|
|
{
|
|
const unsigned char *nh = skb_network_header(skb);
|
|
int packet_len = skb_tail_pointer(skb) - skb_network_header(skb);
|
|
struct ipv6_opt_hdr *hdr;
|
|
int len;
|
|
|
|
if (offset + 2 > packet_len)
|
|
goto bad;
|
|
hdr = (struct ipv6_opt_hdr *)(nh + offset);
|
|
len = ((hdr->hdrlen + 1) << 3);
|
|
|
|
if (offset + len > packet_len)
|
|
goto bad;
|
|
|
|
offset += 2;
|
|
len -= 2;
|
|
|
|
while (len > 0) {
|
|
int opttype = nh[offset];
|
|
int optlen;
|
|
|
|
if (opttype == type)
|
|
return offset;
|
|
|
|
switch (opttype) {
|
|
case IPV6_TLV_PAD1:
|
|
optlen = 1;
|
|
break;
|
|
default:
|
|
optlen = nh[offset + 1] + 2;
|
|
if (optlen > len)
|
|
goto bad;
|
|
break;
|
|
}
|
|
offset += optlen;
|
|
len -= optlen;
|
|
}
|
|
/* not_found */
|
|
bad:
|
|
return -1;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ipv6_find_tlv);
|
|
|
|
/*
|
|
* find the offset to specified header or the protocol number of last header
|
|
* if target < 0. "last header" is transport protocol header, ESP, or
|
|
* "No next header".
|
|
*
|
|
* Note that *offset is used as input/output parameter, and if it is not zero,
|
|
* then it must be a valid offset to an inner IPv6 header. This can be used
|
|
* to explore inner IPv6 header, eg. ICMPv6 error messages.
|
|
*
|
|
* If target header is found, its offset is set in *offset and return protocol
|
|
* number. Otherwise, return -1.
|
|
*
|
|
* If the first fragment doesn't contain the final protocol header or
|
|
* NEXTHDR_NONE it is considered invalid.
|
|
*
|
|
* Note that non-1st fragment is special case that "the protocol number
|
|
* of last header" is "next header" field in Fragment header. In this case,
|
|
* *offset is meaningless and fragment offset is stored in *fragoff if fragoff
|
|
* isn't NULL.
|
|
*
|
|
* if flags is not NULL and it's a fragment, then the frag flag
|
|
* IP6_FH_F_FRAG will be set. If it's an AH header, the
|
|
* IP6_FH_F_AUTH flag is set and target < 0, then this function will
|
|
* stop at the AH header. If IP6_FH_F_SKIP_RH flag was passed, then this
|
|
* function will skip all those routing headers, where segements_left was 0.
|
|
*/
|
|
int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset,
|
|
int target, unsigned short *fragoff, int *flags)
|
|
{
|
|
unsigned int start = skb_network_offset(skb) + sizeof(struct ipv6hdr);
|
|
u8 nexthdr = ipv6_hdr(skb)->nexthdr;
|
|
bool found;
|
|
|
|
if (fragoff)
|
|
*fragoff = 0;
|
|
|
|
if (*offset) {
|
|
struct ipv6hdr _ip6, *ip6;
|
|
|
|
ip6 = skb_header_pointer(skb, *offset, sizeof(_ip6), &_ip6);
|
|
if (!ip6 || (ip6->version != 6))
|
|
return -EBADMSG;
|
|
start = *offset + sizeof(struct ipv6hdr);
|
|
nexthdr = ip6->nexthdr;
|
|
}
|
|
|
|
do {
|
|
struct ipv6_opt_hdr _hdr, *hp;
|
|
unsigned int hdrlen;
|
|
found = (nexthdr == target);
|
|
|
|
if ((!ipv6_ext_hdr(nexthdr)) || nexthdr == NEXTHDR_NONE) {
|
|
if (target < 0 || found)
|
|
break;
|
|
return -ENOENT;
|
|
}
|
|
|
|
hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
|
|
if (!hp)
|
|
return -EBADMSG;
|
|
|
|
if (nexthdr == NEXTHDR_ROUTING) {
|
|
struct ipv6_rt_hdr _rh, *rh;
|
|
|
|
rh = skb_header_pointer(skb, start, sizeof(_rh),
|
|
&_rh);
|
|
if (!rh)
|
|
return -EBADMSG;
|
|
|
|
if (flags && (*flags & IP6_FH_F_SKIP_RH) &&
|
|
rh->segments_left == 0)
|
|
found = false;
|
|
}
|
|
|
|
if (nexthdr == NEXTHDR_FRAGMENT) {
|
|
unsigned short _frag_off;
|
|
__be16 *fp;
|
|
|
|
if (flags) /* Indicate that this is a fragment */
|
|
*flags |= IP6_FH_F_FRAG;
|
|
fp = skb_header_pointer(skb,
|
|
start+offsetof(struct frag_hdr,
|
|
frag_off),
|
|
sizeof(_frag_off),
|
|
&_frag_off);
|
|
if (!fp)
|
|
return -EBADMSG;
|
|
|
|
_frag_off = ntohs(*fp) & ~0x7;
|
|
if (_frag_off) {
|
|
if (target < 0 &&
|
|
((!ipv6_ext_hdr(hp->nexthdr)) ||
|
|
hp->nexthdr == NEXTHDR_NONE)) {
|
|
if (fragoff)
|
|
*fragoff = _frag_off;
|
|
return hp->nexthdr;
|
|
}
|
|
if (!found)
|
|
return -ENOENT;
|
|
if (fragoff)
|
|
*fragoff = _frag_off;
|
|
break;
|
|
}
|
|
hdrlen = 8;
|
|
} else if (nexthdr == NEXTHDR_AUTH) {
|
|
if (flags && (*flags & IP6_FH_F_AUTH) && (target < 0))
|
|
break;
|
|
hdrlen = ipv6_authlen(hp);
|
|
} else
|
|
hdrlen = ipv6_optlen(hp);
|
|
|
|
if (!found) {
|
|
nexthdr = hp->nexthdr;
|
|
start += hdrlen;
|
|
}
|
|
} while (!found);
|
|
|
|
*offset = start;
|
|
return nexthdr;
|
|
}
|
|
EXPORT_SYMBOL(ipv6_find_hdr);
|