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Fix bounds check in read_key()

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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Note that 'key-method 1' has been replaced by 'key method 2' as the default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 <steffan.karger@fox-it.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Acked-by: David Sommerseth <davids@openvpn.net>
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 <davids@openvpn.net>
(cherry picked from commit fce3437529)
This commit is contained in:
Steffan Karger 2017-08-15 10:04:33 +02:00 committed by David Sommerseth
parent 4bec9d25d5
commit a9f5c744d6
No known key found for this signature in database
GPG Key ID: 86CF944C9671FDF2
1 changed files with 3 additions and 2 deletions
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5
crypto.c
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@ -1461,13 +1461,14 @@ read_key (struct key *key, const struct key_type *kt, struct buffer *buf)
if (!buf_read (buf, &hmac_length, 1))
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;
if (!buf_read (buf, key->hmac, hmac_length))
goto read_err;
if (cipher_length != kt->cipher_length || hmac_length != kt->hmac_length)
goto key_len_err;
return 1;