On Mon, Nov 10, 2014 at 06:00:09PM +0100, Daniel Borkmann wrote:
> A very minimal and simple user space application allocating an SCTP
> socket, setting SCTP_AUTH_KEY setsockopt(2) on it and then closing
> the socket again will leak the memory containing the authentication
> key from user space:
>
> unreferenced object 0xffff8800837047c0 (size 16):
> comm "a.out", pid 2789, jiffies 4296954322 (age 192.258s)
> hex dump (first 16 bytes):
> 01 00 00 00 04 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<ffffffff816d7e8e>] kmemleak_alloc+0x4e/0xb0
> [<ffffffff811c88d8>] __kmalloc+0xe8/0x270
> [<ffffffffa0870c23>] sctp_auth_create_key+0x23/0x50 [sctp]
> [<ffffffffa08718b1>] sctp_auth_set_key+0xa1/0x140 [sctp]
> [<ffffffffa086b383>] sctp_setsockopt+0xd03/0x1180 [sctp]
> [<ffffffff815bfd94>] sock_common_setsockopt+0x14/0x20
> [<ffffffff815beb61>] SyS_setsockopt+0x71/0xd0
> [<ffffffff816e58a9>] system_call_fastpath+0x12/0x17
> [<ffffffffffffffff>] 0xffffffffffffffff
>
> This is bad because of two things, we can bring down a machine from
> user space when auth_enable=1, but also we would leave security sensitive
> keying material in memory without clearing it after use. The issue is
> that sctp_auth_create_key() already sets the refcount to 1, but after
> allocation sctp_auth_set_key() does an additional refcount on it, and
> thus leaving it around when we free the socket.
>
> Fixes: 65b07e5d0d0 ("[SCTP]: API updates to suport SCTP-AUTH extensions.")
> Signed-off-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
> Cc: Vlad Yasevich <vyasevich@xxxxxxxxx>
> ---
> net/sctp/auth.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/net/sctp/auth.c b/net/sctp/auth.c
> index 0e85291..fb7976a 100644
> --- a/net/sctp/auth.c
> +++ b/net/sctp/auth.c
> @@ -862,8 +862,6 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
> list_add(&cur_key->key_list, sh_keys);
>
> cur_key->key = key;
> - sctp_auth_key_hold(key);
> -
> return 0;
> nomem:
> if (!replace)
> --
> 1.7.11.7
>
> --
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>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
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