From 3b1a61e9fb27213c46f76312f4065816bee8ed01 Mon Sep 17 00:00:00 2001 From: Steffan Karger Date: Tue, 15 Aug 2017 10:04:33 +0200 Subject: [PATCH] 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 Note that 'key-method 1' has been replaced by 'key method 2' as the default in OpenVPN 2.0 (released on 2005-04-17), and explicitly deprecated in 2.4 and marked for removal in 2.5.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. CVE: 2017-12166 Signed-off-by: Steffan Karger Acked-by: Gert Doering Acked-by: David Sommerseth Message-Id: <80690690-67ac-3320-1891-9fecedc6a1fa@fox-it.com> URL: https://www.mail-archive.com/search?l=mid&q=80690690-67ac-3320-1891-9fecedc6a1fa@fox-it.com Signed-off-by: David Sommerseth --- 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 131257e5..3f3caa1c 100644 --- a/src/openvpn/crypto.c +++ b/src/openvpn/crypto.c @@ -1666,6 +1666,11 @@ 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; @@ -1675,11 +1680,6 @@ 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: -- 2.13.6