Overview

This is another overflow in the DOUBLE data type in MySQL I found. You can refer to my previous post on BIGINT Overflow Error based injections if you want to understand exploiting overflows in extracting data. Also the queries are similar to my previous post. When we take the functions in MySQL I was interested in the mathematical functions. They too should contain some data type to hold values. So I went on testing for functions which would cause any overflow errors and I found out that exp() would cause a overflow error when we pass a large value above 709.

mysql> select exp(709);
+-----------------------+
| exp(709)              |
+-----------------------+
| 8.218407461554972e307 |
+-----------------------+
1 row in set (0.00 sec)

mysql> select exp(710);
ERROR 1690 (22003): DOUBLE value is out of range in 'exp(710)'

The exp is the opposite of the ln and log functions of MySQL. If I briefly explain the functionality of these, log and ln and both returns the answer to the natural logarithm or to the base e. In common e is approximated to: $latex e \approx 2.71828183&bg=FFFFFF&s=1$ .

$latex ln(15) = log_ {e} (15) = 2.70805020110221 &bg=FFFFFF&s=1$
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Overview

I was interested in finding out new techniques that we can use in extracting data via MySQL errors. This is a detailed write-up which will make you understand how I made these queries. When we look how MySQL handles integers I was interested in causing overflows. This is how MySQL stores integers.

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(Source: http://dev.mysql.com/doc/refman/5.5/en/integer-types.html)
These overflow errors will cause in MySQL versions 5.5.5 and above only. In below versions integer overflows would result in a silent wraparound.
The data type BIGINT is of 8 bytes in size which means it’s of 64 bits. If we take the maximum signed value of a BIGINT its “0b0111111111111111111111111111111111111111111111111111111111111111”, “0x7fffffffffffffff”, “9223372036854775807” in binary, hex and decimal respectively. Once we evaluate numerical expressions on this value like adding will cause a “BIGINT value is out of range” error.

mysql> select 9223372036854775807+1; 
ERROR 1690 (22003): BIGINT value is out of range in '(9223372036854775807 + 1)'

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