Hi,
On Tue, Aug 15, 2017 at 10:10:32AM +0200, Steffan Karger wrote:
[..]
> To all: following <54fc26bb.2000...@karger.me> and commit 1ce06386, I
> think it really is time to remove key method 1 from the master branch.
>
> Attached a proposed patch to fix this issue in release/2.4 and master.
>
> -Steffan
> From f7390bf97af7f1977547586529be1d51adde4c67 Mon Sep 17 00:00:00 2001
> From: Steffan Karger <steffan.kar...@fox-it.com>
> Date: Tue, 15 Aug 2017 10:04:33 +0200
> Subject: [PATCH] CVE-2017-xxx: fix bounds check in read_key()
>
> The bounds check in read_key() was performed after using the value, instead
> of before. If 'key-method 1' is used, this allowed an attacker to send a
> malformed packet to trigger a stack buffer overflow.
>
> Fix this by moving the input validation to before the writes.
>
> Note that 'key-method 1' has been replaced by 'key method 2' as the default
> in OpenVPN 2.0 (released on 2005-04-17), and explicitly deprecated in 2.4
> and marked for removal in 2.5. This should limit the amount of users
> impacted by this issue.
>
> Signed-off-by: Steffan Karger <steffan.kar...@fox-it.com>
> ---
> src/openvpn/crypto.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/src/openvpn/crypto.c b/src/openvpn/crypto.c
> index cc3c7b6..0ebbcd0 100644
> --- a/src/openvpn/crypto.c
> +++ b/src/openvpn/crypto.c
> @@ -1653,6 +1653,11 @@ read_key(struct key *key, const struct key_type *kt,
> struct buffer *buf)
> goto read_err;
> }
>
> + if (cipher_length != kt->cipher_length || hmac_length != kt->hmac_length)
> + {
> + goto key_len_err;
> + }
> +
> if (!buf_read(buf, key->cipher, cipher_length))
> {
> goto read_err;
> @@ -1662,11 +1667,6 @@ read_key(struct key *key, const struct key_type *kt,
> struct buffer *buf)
> goto read_err;
> }
>
> - if (cipher_length != kt->cipher_length || hmac_length != kt->hmac_length)
> - {
> - goto key_len_err;
> - }
> -
> return 1;
>
> read_err:
ACK. Fixes the problem at hand and is generally good housekeeping
to check your things first :-)
Subject: and commit message needs "real" CVE message.
gert
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Gert Doering - Munich, Germany g...@greenie.muc.de
fax: +49-89-35655025 g...@net.informatik.tu-muenchen.de
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