Web Application Security
Re: SQLi with backslash Jun 25 2011 10:40PM
Voulnet (voulnet gmail com) (1 replies)
Have you tried a backslash to let MySQL auto escape a single quote for you?
Example:

insert into log values('a\', ' );drop table log --');

If I am correct, the first parameter would be 'a\', ' <-- this would
be because with the backslash, MySQL would escape the next single
quote, and consider the starting single quote of the 2nd parameter as
the closing quote of the 1st parameter, then what you input as the 2nd
parameter would be executed, so you terminate the insert correctly and
execute your SQLi string.

I am not sure if it would work, but I'm sure you can play around with
that concept and get it to to work. You might have some lack finding
column truncation issues, too.

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On Sat, Jun 25, 2011 at 10:33 PM, Robin Wood <robin (at) digininja (dot) org [email concealed]> wrote:
> On 25 June 2011 17:51, Voulnet <voulnet (at) gmail (dot) com [email concealed]> wrote:
>> Okay then, have you tried an alternate encoding? MySQL can act funny
>> when asian characters are used. For reference you can see this:
>>
>> http://stackoverflow.com/questions/1220182/does-mysql-real-escape-string
-fully-protect-against-sql-injection
>>
>> Because, if I understand correctly, there would a discrepancy between
>> what PHP sees (thinking it is a normal multibyte character and passing
>> it on, and what MySQL sees if set incorrectly which would result in it
>> parsing the asian character as something + single quote.
>
> Just tried and it didn't work, was worth a try.
>
>> By the way, have you tried the char(39) or hex encoding and verified
>> it didn't work?
>
> Yes, it won't work as the char(39) is inside the quotes so is just
> taken as a string:
>
> insert into log values ('a', 'xx char(39) ...');
>
> To use it I would have to have broken out of the quotes first.
>
> Robin
>
>>
>> On Sat, Jun 25, 2011 at 1:36 PM, Robin Wood <robin (at) digininja (dot) org [email concealed]> wrote:
>>> On 24 June 2011 18:17, Voulnet <voulnet (at) gmail (dot) com [email concealed]> wrote:
>>>> They are probably using that mysql_real_escape_string php function,
>>>> which escapes these characters. There are many ways to bypass it, and
>>>> you can find it all over the web.
>>>>
>>>> Some examples:
>>>>
>>>> use char(39) <-- ASCII decimal value of ' is 39
>>>> or use the hex value. For example SELECT (0x27) <-- 27 is the hex value of '.
>>>>
>>>> For example if you want to load a file, you would call
>>>> load_file('myfile'), using hex encoding you take 'myfile' with the
>>>> single quotes included and convert it to hex, then write it as
>>>> load_file(0x27..........27) with the rest of the hex values of the
>>>> filename characters filled in between.
>>>>
>>>
>>> No, all they are doing is stripping ' and ", they dump the statements
>>> to screen in the error message.
>>>
>>> And using 0x27 will just end up with the string 0x27 being inserted as
>>> it is inside the single quoted string. That might help if I could
>>> escape the quotes but that is the bit I can't do.
>>>
>>> Robin
>>>
>>>>
>>>> On Wed, Jun 22, 2011 at 5:03 PM, Robin Wood <robin (at) digininja (dot) org [email concealed]> wrote:
>>>>> Hi
>>>>> I've got a scenario where both single and double quotes are being
>>>>> stripped but no other escaping appears to be being performed. The
>>>>> database is MySQL with php on top.
>>>>>
>>>>> The query that I've found SQL injection on is in the form
>>>>>
>>>>> insert into log values ('a', 'b');
>>>>>
>>>>> where I can inject in to the second parameter.
>>>>>
>>>>> If I inject a backslash then I get
>>>>>
>>>>> insert into log values ('a', 'b\');
>>>>>
>>>>> which gives an invalid SQL statement and is how the injection was
>>>>> found. Can anyone come up with a way to exploit this? If I put
>>>>> anything before the slash isn't really worth anything and if I put
>>>>> anything after then the statement becomes valid and the slash escapes
>>>>> whatever character is after it.
>>>>>
>>>>> I thought about using the slash to encode something but couldn't get it to work.
>>>>>
>>>>> The table is write only for me, I can't see any of its entries echo'ed
>>>>> back to the site anywhere so I can't go for stored XSS or anything
>>>>> like that (maybe possible but not in the time available for the test).
>>>>>
>>>>> Apart from breaking the statement I can't see a way to exploit this,
>>>>> can anyone else?
>>>>>
>>>>> Robin
>>>>>
>>>>>
>>>>>
>>>>> This list is sponsored by Cenzic
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>>>>>
>>>>>
>>>>
>>>
>>
>

This list is sponsored by Cenzic
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[ reply ]
Re: SQLi with backslash Jun 25 2011 10:46PM
Robin Wood (robin digininja org) (1 replies)
Re: SQLi with backslash Jun 26 2011 05:02AM
Voulnet (voulnet gmail com)


 

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