Hello Daniel,
Something went wrong in my last email, what I wanted to say is:
The patch prevents that "cur_len" underflows. No negative values for
"cur_len" so no way to underflow the "cur_len" variable and therefore no
vulnerability.
Hector.
On 24/10/2019 15:13, Hector Marco wrote:
> Hello Daniel,
>
> The patch prevents that "cur_len" underflows. No negative values for
> "cur_len" so way to underflow the "cur_len" variable and therefore
>
> I hope this helps,
>
> Hector.
>
>
>
> On 23/10/2019 11:14, Daniel Kiper wrote:
>> On Fri, Oct 18, 2019 at 02:39:01PM +0200, Javier Martinez Canillas wrote:
>>> From: Hector Marco-Gisbert <hecma...@upv.es>
>>>
>>> This patch fixes two integer underflows at:
>>> * grub-core/lib/crypto.c
>>> * grub-core/normal/auth.c
>>>
>>> Resolves: CVE-2015-8370
>>>
>>> Signed-off-by: Hector Marco-Gisbert <hecma...@upv.es>
>>> Signed-off-by: Ismael Ripoll-Ripoll <irip...@disca.upv.es>
>>> Signed-off-by: Javier Martinez Canillas <javi...@redhat.com>
>>> ---
>>>
>>> grub-core/lib/crypto.c | 2 +-
>>> grub-core/normal/auth.c | 2 +-
>>> 2 files changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/grub-core/lib/crypto.c b/grub-core/lib/crypto.c
>>> index ca334d5a40e..e6c78d16d39 100644
>>> --- a/grub-core/lib/crypto.c
>>> +++ b/grub-core/lib/crypto.c
>>> @@ -468,7 +468,7 @@ grub_password_get (char buf[], unsigned buf_size)
>>> break;
>>> }
>>>
>>> - if (key == '\b')
>>> + if (key == '\b' && cur_len)
>>> {
>>> if (cur_len)
>>> cur_len--;
>>> diff --git a/grub-core/normal/auth.c b/grub-core/normal/auth.c
>>> index 6be678c0de1..c35ce972473 100644
>>> --- a/grub-core/normal/auth.c
>>> +++ b/grub-core/normal/auth.c
>>> @@ -172,7 +172,7 @@ grub_username_get (char buf[], unsigned buf_size)
>>> break;
>>> }
>>>
>>> - if (key == GRUB_TERM_BACKSPACE)
>>> + if (key == GRUB_TERM_BACKSPACE && cur_len)
>>> {
>>> if (cur_len)
>>> {
>>
>> TBH, I do not understand how this patch helps. It only delays continue
>> execution to the next "if (!grub_isprint (key))" if cur_len == 0.
>>
>> Daniel
>>
>
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