| Message ID | 20200727175720.4022402-2-willmcvicker@google.com |
|---|---|
| State | Changes Requested |
| Delegated to: | Pablo Neira |
| Headers | show |
| Series | Netfilter OOB memory access security patch | expand |
Hi Will, On Mon, Jul 27, 2020 at 05:57:20PM +0000, Will McVicker wrote: > The indexes to the nf_nat_l[34]protos arrays come from userspace. So we > need to make sure that before indexing the arrays, we verify the index > is within the array bounds in order to prevent an OOB memory access. > Here is an example kernel panic on 4.14.180 when userspace passes in an > index greater than NFPROTO_NUMPROTO. > > Internal error: Oops - BUG: 0 [#1] PREEMPT SMP > Modules linked in:... > Process poc (pid: 5614, stack limit = 0x00000000a3933121) > CPU: 4 PID: 5614 Comm: poc Tainted: G S W O 4.14.180-g051355490483 > Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150 Google Inc. MSM > task: 000000002a3dfffe task.stack: 00000000a3933121 > pc : __cfi_check_fail+0x1c/0x24 > lr : __cfi_check_fail+0x1c/0x24 > ... > Call trace: > __cfi_check_fail+0x1c/0x24 > name_to_dev_t+0x0/0x468 > nfnetlink_parse_nat_setup+0x234/0x258 If this oops is only triggerable from userspace, I think a sanity check in nfnetlink_parse_nat_setup should suffice to reject unsupported layer 3 and layer 4 protocols. I mean, in this patch I see more chunks in the packet path, such as nf_nat_l3proto_ipv4 that should never happen. I would just fix the userspace ctnetlink path. BTW, do you have a Fixes: tag for this? This will be useful for -stable maintainer to pick up this fix. Thanks.
Hi Pablo, Yes, I believe this oops is only triggered by userspace when the user specifically passes in an invalid nf_nat_l3protos index. I'm happy to re-work the patch to check for this in ctnetlink_create_conntrack(). > BTW, do you have a Fixes: tag for this? This will be useful for > -stable maintainer to pick up this fix. Regarding the Fixes: tag, I don't have one offhand since this bug was reported to me, but I can search through the code history to find the commit that exposed this vulnerability. Thanks, Will On 07/29/2020, Pablo Neira Ayuso wrote: > Hi Will, > > On Mon, Jul 27, 2020 at 05:57:20PM +0000, Will McVicker wrote: > > The indexes to the nf_nat_l[34]protos arrays come from userspace. So we > > need to make sure that before indexing the arrays, we verify the index > > is within the array bounds in order to prevent an OOB memory access. > > Here is an example kernel panic on 4.14.180 when userspace passes in an > > index greater than NFPROTO_NUMPROTO. > > > > Internal error: Oops - BUG: 0 [#1] PREEMPT SMP > > Modules linked in:... > > Process poc (pid: 5614, stack limit = 0x00000000a3933121) > > CPU: 4 PID: 5614 Comm: poc Tainted: G S W O 4.14.180-g051355490483 > > Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150 Google Inc. MSM > > task: 000000002a3dfffe task.stack: 00000000a3933121 > > pc : __cfi_check_fail+0x1c/0x24 > > lr : __cfi_check_fail+0x1c/0x24 > > ... > > Call trace: > > __cfi_check_fail+0x1c/0x24 > > name_to_dev_t+0x0/0x468 > > nfnetlink_parse_nat_setup+0x234/0x258 > > If this oops is only triggerable from userspace, I think a sanity > check in nfnetlink_parse_nat_setup should suffice to reject > unsupported layer 3 and layer 4 protocols. > > I mean, in this patch I see more chunks in the packet path, such as > nf_nat_l3proto_ipv4 that should never happen. I would just fix the > userspace ctnetlink path. > > BTW, do you have a Fixes: tag for this? This will be useful for > -stable maintainer to pick up this fix. > > Thanks.
Hi William, On Fri, Jul 31, 2020 at 12:26:11AM +0000, William Mcvicker wrote: > Hi Pablo, > > Yes, I believe this oops is only triggered by userspace when the user > specifically passes in an invalid nf_nat_l3protos index. I'm happy to re-work > the patch to check for this in ctnetlink_create_conntrack(). Great. Note that this code does not exist in the tree anymore. I'm not sure if this problem still exists upstream, this patch does not apply to nf.git. This fix should only go for -stable maintainers. > > BTW, do you have a Fixes: tag for this? This will be useful for > > -stable maintainer to pick up this fix. > > Regarding the Fixes: tag, I don't have one offhand since this bug was reported > to me, but I can search through the code history to find the commit that > exposed this vulnerability. That would be great. Thank you.
Hi Pablo, > Note that this code does not exist in the tree anymore. I'm not sure > if this problem still exists upstream, this patch does not apply to > nf.git. This fix should only go for -stable maintainers. Right, the vulnerability has been fixed by the refactor commit fe2d0020994cd ("netfilter: nat: remove l4proto->in_range"), but this patch is a part of a full re-work of the code and doesn't backport very cleanly to the LTS branches. So this fix is only applicable to the 4.19, 4.14, 4.9, and 4.4 LTS branches. I missed the -stable email, but will re-add it to this thread with the re-worked patch. Thanks, Will On 07/31/2020, Pablo Neira Ayuso wrote: > Hi William, > > On Fri, Jul 31, 2020 at 12:26:11AM +0000, William Mcvicker wrote: > > Hi Pablo, > > > > Yes, I believe this oops is only triggered by userspace when the user > > specifically passes in an invalid nf_nat_l3protos index. I'm happy to re-work > > the patch to check for this in ctnetlink_create_conntrack(). > > Great. > > Note that this code does not exist in the tree anymore. I'm not sure > if this problem still exists upstream, this patch does not apply to > nf.git. This fix should only go for -stable maintainers. > > > > BTW, do you have a Fixes: tag for this? This will be useful for > > > -stable maintainer to pick up this fix. > > > > Regarding the Fixes: tag, I don't have one offhand since this bug was reported > > to me, but I can search through the code history to find the commit that > > exposed this vulnerability. > > That would be great. > > Thank you.
Hi, I have attached the follow up fix that checks for the proto index during conntrack creation. Thanks, Will On 07/31/2020, William Mcvicker wrote: > Hi Pablo, > > > Note that this code does not exist in the tree anymore. I'm not sure > > if this problem still exists upstream, this patch does not apply to > > nf.git. This fix should only go for -stable maintainers. > > Right, the vulnerability has been fixed by the refactor commit fe2d0020994cd > ("netfilter: nat: remove l4proto->in_range"), but this patch is a part of > a full re-work of the code and doesn't backport very cleanly to the LTS > branches. So this fix is only applicable to the 4.19, 4.14, 4.9, and 4.4 LTS > branches. I missed the -stable email, but will re-add it to this thread with > the re-worked patch. > > Thanks, > Will > > On 07/31/2020, Pablo Neira Ayuso wrote: > > Hi William, > > > > On Fri, Jul 31, 2020 at 12:26:11AM +0000, William Mcvicker wrote: > > > Hi Pablo, > > > > > > Yes, I believe this oops is only triggered by userspace when the user > > > specifically passes in an invalid nf_nat_l3protos index. I'm happy to re-work > > > the patch to check for this in ctnetlink_create_conntrack(). > > > > Great. > > > > Note that this code does not exist in the tree anymore. I'm not sure > > if this problem still exists upstream, this patch does not apply to > > nf.git. This fix should only go for -stable maintainers. > > > > > > BTW, do you have a Fixes: tag for this? This will be useful for > > > > -stable maintainer to pick up this fix. > > > > > > Regarding the Fixes: tag, I don't have one offhand since this bug was reported > > > to me, but I can search through the code history to find the commit that > > > exposed this vulnerability. > > > > That would be great. > > > > Thank you.
Hi, This patch is much smaller and if you confirm this is address the issue, then this is awesome. On Mon, Aug 03, 2020 at 06:31:56PM +0000, William Mcvicker wrote: [...] > diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c > index 31fa94064a62..56d310f8b29a 100644 > --- a/net/netfilter/nf_conntrack_netlink.c > +++ b/net/netfilter/nf_conntrack_netlink.c > @@ -1129,6 +1129,8 @@ ctnetlink_parse_tuple(const struct nlattr * const cda[], > if (!tb[CTA_TUPLE_IP]) > return -EINVAL; > > + if (l3num >= NFPROTO_NUMPROTO) > + return -EINVAL; l3num can only be either NFPROTO_IPV4 or NFPROTO_IPV6. Other than that, bail out with EOPNOTSUPP. Thank you.
Hi Will, Pablo, On Tue, Aug 04, 2020 at 01:37:11PM +0200, Pablo Neira Ayuso wrote: > This patch is much smaller and if you confirm this is address the > issue, then this is awesome. Did that ever get confirmed? AFAICT, nothing ended up landing in the stable trees for this. Cheers, Will > On Mon, Aug 03, 2020 at 06:31:56PM +0000, William Mcvicker wrote: > [...] > > diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c > > index 31fa94064a62..56d310f8b29a 100644 > > --- a/net/netfilter/nf_conntrack_netlink.c > > +++ b/net/netfilter/nf_conntrack_netlink.c > > @@ -1129,6 +1129,8 @@ ctnetlink_parse_tuple(const struct nlattr * const cda[], > > if (!tb[CTA_TUPLE_IP]) > > return -EINVAL; > > > > + if (l3num >= NFPROTO_NUMPROTO) > > + return -EINVAL; > > l3num can only be either NFPROTO_IPV4 or NFPROTO_IPV6. > > Other than that, bail out with EOPNOTSUPP. > > Thank you.
Hi Will, Pablo is going to add the latest patch to the nf.git tree. Once that happens, I'm going to propose the patch in nf.git get cherry-picked to the -stable branches. Thanks, Will On Tue, Sep 1, 2020 at 8:36 AM Will Deacon <will@kernel.org> wrote: > > Hi Will, Pablo, > > On Tue, Aug 04, 2020 at 01:37:11PM +0200, Pablo Neira Ayuso wrote: > > This patch is much smaller and if you confirm this is address the > > issue, then this is awesome. > > Did that ever get confirmed? AFAICT, nothing ended up landing in the stable > trees for this. > > Cheers, > > Will > > > > On Mon, Aug 03, 2020 at 06:31:56PM +0000, William Mcvicker wrote: > > [...] > > > diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c > > > index 31fa94064a62..56d310f8b29a 100644 > > > --- a/net/netfilter/nf_conntrack_netlink.c > > > +++ b/net/netfilter/nf_conntrack_netlink.c > > > @@ -1129,6 +1129,8 @@ ctnetlink_parse_tuple(const struct nlattr * const cda[], > > > if (!tb[CTA_TUPLE_IP]) > > > return -EINVAL; > > > > > > + if (l3num >= NFPROTO_NUMPROTO) > > > + return -EINVAL; > > > > l3num can only be either NFPROTO_IPV4 or NFPROTO_IPV6. > > > > Other than that, bail out with EOPNOTSUPP. > > > > Thank you.
diff --git a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c index 6115bf1ff6f0..1912fc66147c 100644 --- a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c +++ b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c @@ -218,7 +218,8 @@ int nf_nat_icmp_reply_translation(struct sk_buff *skb, return 1; l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, inside->ip.protocol); - if (!nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp), + if (!l4proto || + !nf_nat_ipv4_manip_pkt(skb, hdrlen + sizeof(inside->icmp), l4proto, &ct->tuplehash[!dir].tuple, !manip)) return 0; @@ -234,7 +235,8 @@ int nf_nat_icmp_reply_translation(struct sk_buff *skb, /* Change outer to look like the reply to an incoming packet */ nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple); l4proto = __nf_nat_l4proto_find(NFPROTO_IPV4, 0); - if (!nf_nat_ipv4_manip_pkt(skb, 0, l4proto, &target, manip)) + if (!l4proto || + !nf_nat_ipv4_manip_pkt(skb, 0, l4proto, &target, manip)) return 0; return 1; diff --git a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c index ca6d38698b1a..a72840baf27b 100644 --- a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c +++ b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c @@ -228,7 +228,8 @@ int nf_nat_icmpv6_reply_translation(struct sk_buff *skb, return 1; l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, inside->ip6.nexthdr); - if (!nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6), + if (!l4proto || + !nf_nat_ipv6_manip_pkt(skb, hdrlen + sizeof(inside->icmp6), l4proto, &ct->tuplehash[!dir].tuple, !manip)) return 0; @@ -245,7 +246,7 @@ int nf_nat_icmpv6_reply_translation(struct sk_buff *skb, nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple); l4proto = __nf_nat_l4proto_find(NFPROTO_IPV6, IPPROTO_ICMPV6); - if (!nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip)) + if (!l4proto || !nf_nat_ipv6_manip_pkt(skb, 0, l4proto, &target, manip)) return 0; return 1; diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c index 2268b10a9dcf..d28185f38955 100644 --- a/net/netfilter/nf_nat_core.c +++ b/net/netfilter/nf_nat_core.c @@ -64,12 +64,16 @@ struct nat_net { inline const struct nf_nat_l3proto * __nf_nat_l3proto_find(u8 family) { + if (family >= NFPROTO_NUMPROTO) + return NULL; return rcu_dereference(nf_nat_l3protos[family]); } inline const struct nf_nat_l4proto * __nf_nat_l4proto_find(u8 family, u8 protonum) { + if (family >= NFPROTO_NUMPROTO) + return NULL; return rcu_dereference(nf_nat_l4protos[family][protonum]); } EXPORT_SYMBOL_GPL(__nf_nat_l4proto_find); @@ -317,7 +321,7 @@ find_best_ips_proto(const struct nf_conntrack_zone *zone, * range. It might not be possible to get a unique tuple, but we try. * At worst (or if we race), we will end up with a final duplicate in * __ip_conntrack_confirm and drop the packet. */ -static void +static int get_unique_tuple(struct nf_conntrack_tuple *tuple, const struct nf_conntrack_tuple *orig_tuple, const struct nf_nat_range2 *range, @@ -328,13 +332,22 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple, const struct nf_nat_l3proto *l3proto; const struct nf_nat_l4proto *l4proto; struct net *net = nf_ct_net(ct); + int ret = 0; zone = nf_ct_zone(ct); rcu_read_lock(); l3proto = __nf_nat_l3proto_find(orig_tuple->src.l3num); + if (!l3proto) { + ret = -EINVAL; + goto out; + } l4proto = __nf_nat_l4proto_find(orig_tuple->src.l3num, orig_tuple->dst.protonum); + if (!l4proto) { + ret = -EINVAL; + goto out; + } /* 1) If this srcip/proto/src-proto-part is currently mapped, * and that same mapping gives a unique tuple within the given @@ -387,6 +400,7 @@ get_unique_tuple(struct nf_conntrack_tuple *tuple, l4proto->unique_tuple(l3proto, tuple, range, maniptype, ct); out: rcu_read_unlock(); + return ret; } struct nf_conn_nat *nf_ct_nat_ext_add(struct nf_conn *ct) @@ -409,6 +423,7 @@ nf_nat_setup_info(struct nf_conn *ct, { struct net *net = nf_ct_net(ct); struct nf_conntrack_tuple curr_tuple, new_tuple; + int err; /* Can't setup nat info for confirmed ct. */ if (nf_ct_is_confirmed(ct)) @@ -428,7 +443,9 @@ nf_nat_setup_info(struct nf_conn *ct, nf_ct_invert_tuplepr(&curr_tuple, &ct->tuplehash[IP_CT_DIR_REPLY].tuple); - get_unique_tuple(&new_tuple, &curr_tuple, range, ct, maniptype); + err = get_unique_tuple(&new_tuple, &curr_tuple, range, ct, maniptype); + if (err < 0) + return NF_DROP; if (!nf_ct_tuple_equal(&new_tuple, &curr_tuple)) { struct nf_conntrack_tuple reply; @@ -509,8 +526,12 @@ static unsigned int nf_nat_manip_pkt(struct sk_buff *skb, struct nf_conn *ct, nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple); l3proto = __nf_nat_l3proto_find(target.src.l3num); + if (!l3proto) + return NF_DROP; l4proto = __nf_nat_l4proto_find(target.src.l3num, target.dst.protonum); + if (!l4proto) + return NF_DROP; if (!l3proto->manip_pkt(skb, 0, l4proto, &target, mtype)) return NF_DROP; @@ -816,6 +837,8 @@ static int nfnetlink_parse_nat_proto(struct nlattr *attr, return err; l4proto = __nf_nat_l4proto_find(nf_ct_l3num(ct), nf_ct_protonum(ct)); + if (!l4proto) + return -EINVAL; if (l4proto->nlattr_to_range) err = l4proto->nlattr_to_range(tb, range); diff --git a/net/netfilter/nf_nat_helper.c b/net/netfilter/nf_nat_helper.c index 99606baedda4..6f694444137e 100644 --- a/net/netfilter/nf_nat_helper.c +++ b/net/netfilter/nf_nat_helper.c @@ -121,6 +121,8 @@ bool __nf_nat_mangle_tcp_packet(struct sk_buff *skb, datalen = skb->len - protoff; l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct)); + if (!l3proto) + return false; l3proto->csum_recalc(skb, IPPROTO_TCP, tcph, &tcph->check, datalen, oldlen); @@ -179,6 +181,8 @@ nf_nat_mangle_udp_packet(struct sk_buff *skb, return true; l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct)); + if (!l3proto) + return false; l3proto->csum_recalc(skb, IPPROTO_UDP, udph, &udph->check, datalen, oldlen);
The indexes to the nf_nat_l[34]protos arrays come from userspace. So we need to make sure that before indexing the arrays, we verify the index is within the array bounds in order to prevent an OOB memory access. Here is an example kernel panic on 4.14.180 when userspace passes in an index greater than NFPROTO_NUMPROTO. Internal error: Oops - BUG: 0 [#1] PREEMPT SMP Modules linked in:... Process poc (pid: 5614, stack limit = 0x00000000a3933121) CPU: 4 PID: 5614 Comm: poc Tainted: G S W O 4.14.180-g051355490483 Hardware name: Qualcomm Technologies, Inc. SM8150 V2 PM8150 Google Inc. MSM task: 000000002a3dfffe task.stack: 00000000a3933121 pc : __cfi_check_fail+0x1c/0x24 lr : __cfi_check_fail+0x1c/0x24 ... Call trace: __cfi_check_fail+0x1c/0x24 name_to_dev_t+0x0/0x468 nfnetlink_parse_nat_setup+0x234/0x258 ctnetlink_parse_nat_setup+0x4c/0x228 ctnetlink_new_conntrack+0x590/0xc40 nfnetlink_rcv_msg+0x31c/0x4d4 netlink_rcv_skb+0x100/0x184 nfnetlink_rcv+0xf4/0x180 netlink_unicast+0x360/0x770 netlink_sendmsg+0x5a0/0x6a4 ___sys_sendmsg+0x314/0x46c SyS_sendmsg+0xb4/0x108 el0_svc_naked+0x34/0x38 Signed-off-by: Will McVicker <willmcvicker@google.com> --- net/ipv4/netfilter/nf_nat_l3proto_ipv4.c | 6 ++++-- net/ipv6/netfilter/nf_nat_l3proto_ipv6.c | 5 +++-- net/netfilter/nf_nat_core.c | 27 ++++++++++++++++++++++-- net/netfilter/nf_nat_helper.c | 4 ++++ 4 files changed, 36 insertions(+), 6 deletions(-)