On 15-08-17 10:10, Steffan Karger wrote:
> On 14-08-17 22:59, Guido Vranken wrote:
>> this concerns key_method 1. I know it's deprecated, but reporting it
>> just in case people still use it..
>>
>> So key_method_1_read() calls read_key() which doesn't perform adequate
>> bounds checks. cipher_length and hmac_length are specified by the
>> peer:
>>
>> 1643 uint8_t cipher_length;
>> 1644 uint8_t hmac_length;
>> 1645
>> 1646 CLEAR(*key);
>> 1647 if (!buf_read(buf, &cipher_length, 1))
>> 1648 {
>> 1649 goto read_err;
>> 1650 }
>> 1651 if (!buf_read(buf, &hmac_length, 1))
>> 1652 {
>> 1653 goto read_err;
>> 1654 }
>>
>> And this many bytes of data are then read into key->cipher and key->hmac:
>>
>> 1656 if (!buf_read(buf, key->cipher, cipher_length))
>> 1657 {
>> 1658 goto read_err;
>> 1659 }
>> 1660 if (!buf_read(buf, key->hmac, hmac_length))
>> 1661 {
>> 1662 goto read_err;
>> 1663 }
>>
>> key->hmac is only 64 bytes. So it's trivial to overflow key->hmac.
>
> Ouch. Thanks once more for the report!
>
> To all: following <[email protected]> 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.
What I should mention too is that 'key-method 1' only works for 'peer to
peer TLS setups' (i.e. 'tls-server' and 'tls-client'). As soon as
someone uses 'mode server' (or 'server'), or 'pull' (or 'client'),
key-method 2 must be used. This strongly limits the possible affected
users.
-Steffan
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