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| author | David Lebrun <dlebrun@google.com> | 2022-09-02 10:45:06 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-09-15 12:23:52 +0200 |
| commit | dc9dbd65c803af1607484fed5da50d41dc8dd864 (patch) | |
| tree | 55ee9033e75f26f953cde017deee0b3eb0063ba3 | |
| parent | c9d6f7ce3b13c48d6693055fae996be72a2d71b0 (diff) | |
| download | linux-stable-dc9dbd65c803af1607484fed5da50d41dc8dd864.tar.gz | |
ipv6: sr: fix out-of-bounds read when setting HMAC data.
[ Upstream commit 84a53580c5d2138c7361c7c3eea5b31827e63b35 ]
The SRv6 layer allows defining HMAC data that can later be used to sign IPv6
Segment Routing Headers. This configuration is realised via netlink through
four attributes: SEG6_ATTR_HMACKEYID, SEG6_ATTR_SECRET, SEG6_ATTR_SECRETLEN and
SEG6_ATTR_ALGID. Because the SECRETLEN attribute is decoupled from the actual
length of the SECRET attribute, it is possible to provide invalid combinations
(e.g., secret = "", secretlen = 64). This case is not checked in the code and
with an appropriately crafted netlink message, an out-of-bounds read of up
to 64 bytes (max secret length) can occur past the skb end pointer and into
skb_shared_info:
Breakpoint 1, seg6_genl_sethmac (skb=<optimized out>, info=<optimized out>) at net/ipv6/seg6.c:208
208 memcpy(hinfo->secret, secret, slen);
(gdb) bt
#0 seg6_genl_sethmac (skb=<optimized out>, info=<optimized out>) at net/ipv6/seg6.c:208
#1 0xffffffff81e012e9 in genl_family_rcv_msg_doit (skb=skb@entry=0xffff88800b1f9f00, nlh=nlh@entry=0xffff88800b1b7600,
extack=extack@entry=0xffffc90000ba7af0, ops=ops@entry=0xffffc90000ba7a80, hdrlen=4, net=0xffffffff84237580 <init_net>, family=<optimized out>,
family=<optimized out>) at net/netlink/genetlink.c:731
#2 0xffffffff81e01435 in genl_family_rcv_msg (extack=0xffffc90000ba7af0, nlh=0xffff88800b1b7600, skb=0xffff88800b1f9f00,
family=0xffffffff82fef6c0 <seg6_genl_family>) at net/netlink/genetlink.c:775
#3 genl_rcv_msg (skb=0xffff88800b1f9f00, nlh=0xffff88800b1b7600, extack=0xffffc90000ba7af0) at net/netlink/genetlink.c:792
#4 0xffffffff81dfffc3 in netlink_rcv_skb (skb=skb@entry=0xffff88800b1f9f00, cb=cb@entry=0xffffffff81e01350 <genl_rcv_msg>)
at net/netlink/af_netlink.c:2501
#5 0xffffffff81e00919 in genl_rcv (skb=0xffff88800b1f9f00) at net/netlink/genetlink.c:803
#6 0xffffffff81dff6ae in netlink_unicast_kernel (ssk=0xffff888010eec800, skb=0xffff88800b1f9f00, sk=0xffff888004aed000)
at net/netlink/af_netlink.c:1319
#7 netlink_unicast (ssk=ssk@entry=0xffff888010eec800, skb=skb@entry=0xffff88800b1f9f00, portid=portid@entry=0, nonblock=<optimized out>)
at net/netlink/af_netlink.c:1345
#8 0xffffffff81dff9a4 in netlink_sendmsg (sock=<optimized out>, msg=0xffffc90000ba7e48, len=<optimized out>) at net/netlink/af_netlink.c:1921
...
(gdb) p/x ((struct sk_buff *)0xffff88800b1f9f00)->head + ((struct sk_buff *)0xffff88800b1f9f00)->end
$1 = 0xffff88800b1b76c0
(gdb) p/x secret
$2 = 0xffff88800b1b76c0
(gdb) p slen
$3 = 64 '@'
The OOB data can then be read back from userspace by dumping HMAC state. This
commit fixes this by ensuring SECRETLEN cannot exceed the actual length of
SECRET.
Reported-by: Lucas Leong <wmliang.tw@gmail.com>
Tested: verified that EINVAL is correctly returned when secretlen > len(secret)
Fixes: 4f4853dc1c9c1 ("ipv6: sr: implement API to control SR HMAC structure")
Signed-off-by: David Lebrun <dlebrun@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | net/ipv6/seg6.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/net/ipv6/seg6.c b/net/ipv6/seg6.c index fdeb90dd1c82..9c45165fe79b 100644 --- a/net/ipv6/seg6.c +++ b/net/ipv6/seg6.c @@ -129,6 +129,11 @@ static int seg6_genl_sethmac(struct sk_buff *skb, struct genl_info *info) goto out_unlock; } + if (slen > nla_len(info->attrs[SEG6_ATTR_SECRET])) { + err = -EINVAL; + goto out_unlock; + } + if (hinfo) { err = seg6_hmac_info_del(net, hmackeyid); if (err) |