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Note that 'key-method 1' has been replaced by 'key method 2' as the default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 <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>
Steffan Karger authored on 2017/08/15 17:04:33Showing 1 changed files
| ... | ... |
@@ -1666,6 +1666,11 @@ read_key(struct key *key, const struct key_type *kt, struct buffer *buf) |
| 1666 | 1666 |
goto read_err; |
| 1667 | 1667 |
} |
| 1668 | 1668 |
|
| 1669 |
+ if (cipher_length != kt->cipher_length || hmac_length != kt->hmac_length) |
|
| 1670 |
+ {
|
|
| 1671 |
+ goto key_len_err; |
|
| 1672 |
+ } |
|
| 1673 |
+ |
|
| 1669 | 1674 |
if (!buf_read(buf, key->cipher, cipher_length)) |
| 1670 | 1675 |
{
|
| 1671 | 1676 |
goto read_err; |
| ... | ... |
@@ -1675,11 +1680,6 @@ read_key(struct key *key, const struct key_type *kt, struct buffer *buf) |
| 1675 | 1675 |
goto read_err; |
| 1676 | 1676 |
} |
| 1677 | 1677 |
|
| 1678 |
- if (cipher_length != kt->cipher_length || hmac_length != kt->hmac_length) |
|
| 1679 |
- {
|
|
| 1680 |
- goto key_len_err; |
|
| 1681 |
- } |
|
| 1682 |
- |
|
| 1683 | 1678 |
return 1; |
| 1684 | 1679 |
|
| 1685 | 1680 |
read_err: |