I am trying to write an sql query and I am having a problem. When we want to write a query with a where clause to narrow down our results, we can do
... where name = 'John'
(Where name is a column in the table).
Now I am trying to insert a clause like this except the name is "O'Malley". So I thought the query would be
... where name = 'O'Malley'
but this gives me a null pointer exception.
Does anyone know how you could solve this problem?
Thanks for your help in advance.
Your problem is that the single quote in the string "O'Malley" is interpreted by SQL as the string terminator. To escape a single quote, replace it with two single quotes, like this:
where name = 'O''Malley'
Edit: If the string "O'Malley" came from a user input, your code is vulnerable to an SQL injection exploit. To avoid this risk, use a parameterized query.
Use bind variables to avoid thinking about quotation problems.
Bind variables beware of sql injection to.
Depending on the database you could escape the ' I think. Have a look at http://dev.mysql.com/doc/refman/5.0/en/string-syntax.html
If you use two apostrophes together in you search string SQL will realise that it is part of the string and isn't part of the SQL syntax.
where name = 'O''Malley'
Related
I am writing a SQL program in Delphi 7 and came across a problem.
If you add an SQL command you have to use ' to indicate it is a Variable or String, but I want to build up my SQL statement because it is coming from different If statements and thus have to build it up. Therefore, I wanted to know if anyone knows a trick to add a ' into a string.
Don't make the same mistake like many before you and lookup parametrized queries or else you will be open for SQL injection attacks. If you need to include string constants in your query then use 2 single quotes ('') or the QuotedStr() function from the SysUtils unit.
Try two quotes to represent one i.e. ''
I'm using sqlite3_exec() function in order to execute an SQL Insert command. The problem starts when I need to insert strings that need to be encoded.
For example, I want to insert the following string: "f('hello')". If I want to insert this string I need to change "'" to "''".
My question is, how do I encode these strings? Is there a function I can count on? or a table that details all the needed encodes?
Thanks! :-)
Instead of manually escaping strings (which is error-prone and invites SQL injection attacks), I'd strongly recommend using prepared statements and bind values; read up on sqlite3_bind_XXX and sqlite3_prepare_v2
Using bind values will solve this problem and it will also make sqlite faster because it remembers previously executed sql statements and it can reuse their execution plans. This doesn't work when the sql statement is always slightly different because it hashes the complete sql statement.
sqlite_mprintf supports %q for that.
"Maybe" you should use something like a prepared statement. I am not an expert in SQLite, but I found this link (http://www.sqlite.org/c3ref/stmt.html) and it could help you. It is about SQL Statement Object.
You have found a SQL injection vulnerability in a numeric field, but you need to use a string value in one of your attack payloads.How can you place a string into your query without using any quotation marks?
Use a parametrized query instead of concatenation strings. Guide to SQL Injection
Escape ' with ''
INSERT INTO Foo(A)VALUES('GEORGE''S CAT')
The website i worked was recently attempted to be hacked by the following SQL injection script
boys' and 3=8 union
select 1,
concat(0x232425,ifnull(`table_name`,0x30),char(9),ifnull(`table_rows`,0x30), char(9),0x252423),
3,4,5,6,7,8,9
from `information_schema`.`tables`
where table_schema=0x62646B3032 limit 44,1 -- And '8'='8
This injection returned the mysql table name. This was reported by the error reporting system on that website and we managed to fix that part however I am not able to understand what does the above injection mean?
Anyone can explain this?
Penuel
They're using a select from the Information Schema views in mysql server :
http://dev.mysql.com/doc/refman/5.0/en/information-schema.html
They use some clever hacks to rout out simple sql injection prevention techniques.
According to this the MySQL concat()
Returns the string that results from
concatenating the arguments. May have
one or more arguments. If all
arguments are nonbinary strings, the
result is a nonbinary string. If the
arguments include any binary strings,
the result is a binary string. A
numeric argument is converted to its
equivalent binary string form
So 0x232425 is converted to #$% which is simply added to the begining and end of the table_name field. Maybe just to make it easier for them to pull out the Table names later using Regex.
Later on the char(9) is equivalent to a tab as you can see here and is just there to format the output nicer.
The 3,4,5,6,7,8,9 is just there so that the columns match the boys table that they are performing the Union on.
This injection returned the mysql table name.
Do you mean that your website displayed the table name when you gave it this input, or that the query returns that when run from the mysql client? If it showed on your website, then the attacker has the ability to inject much more harmful queries. Check your data.
This question already has answers here:
How to anticipate and escape single quote ' in oracle
(2 answers)
Closed 7 years ago.
I have a database with names in it such as John Doe etc. Unfortunately some of these names contain quotes like Keiran O'Keefe. Now when I try and search for such names as follows:
SELECT * FROM PEOPLE WHERE SURNAME='O'Keefe'
I (understandably) get an error.
How do I prevent this error from occurring. I am using Oracle and PLSQL.
The escape character is ', so you would need to replace the quote with two quotes.
For example,
SELECT * FROM PEOPLE WHERE SURNAME='O'Keefe'
becomes
SELECT * FROM PEOPLE WHERE SURNAME='O''Keefe'
That said, it's probably incorrect to do this yourself. Your language may have a function to escape strings for use in SQL, but an even better option is to use parameters. Usually this works as follows.
Your SQL command would be :
SELECT * FROM PEOPLE WHERE SURNAME=?
Then, when you execute it, you pass in "O'Keefe" as a parameter.
Because the SQL is parsed before the parameter value is set, there's no way for the parameter value to alter the structure of the SQL (and it's even a little faster if you want to run the same statement several times with different parameters).
I should also point out that, while your example just causes an error, you open youself up to a lot of other problems by not escaping strings appropriately. See http://en.wikipedia.org/wiki/SQL_injection for a good starting point or the following classic xkcd comic.
Oracle 10 solution is
SELECT * FROM PEOPLE WHERE SURNAME=q'{O'Keefe}'
Parameterized queries are your friend, as suggested by Matt.
Command = SELECT * FROM PEOPLE WHERE SURNAME=?
They will protect you from headaches involved with
Strings with quotes
Querying using dates
SQL Injection
Use of parameterized SQL has other benefits, it reduces CPU overhead (as well as other resources) in Oracle by reducing the amount of work Oracle requires in order to parse the statement. If you do not use parameters (we call them bind variables in Oracle) then "select * from foo where bar='cat'" and "select * from foo where bar='dog'" are treated as separate statements, where as "select * from foo where bar=:b1" is the same statement, meaning things like syntax, validity of objects that are referenced etc...do not need to be checked again. There are occasional problems that arise when using bind variables which usually manifests itself in not getting the most efficient SQL execution plan but there are workarounds for this and these problems really depend on the predicates you are using, indexing and data skew.
Input filtering is usually done on the language level rather than database layers.
php and .NET both have their respective libraries for escaping sql statements. Check your language, see waht's available.
If your data are trustable, then you can just do a string replace to add another ' infront of the ' to escape it. Usually that is enough if there isn't any risks that the input is malicious.
I suppose a good question is what language are you using?
In PHP you would do: SELECT * FROM PEOPLE WHERE SURNAME='mysql_escape_string(O'Keefe)'
But since you didn't specify the language I will suggest that you look into a escape string function mysql or otherwise in your language.
To deal quotes if you're using Zend Framework here is the code
$db = Zend_Db_Table_Abstract::getDefaultAdapter();
$db->quoteInto('your_query_here = ?','your_value_here');
for example ;
//SELECT * FROM PEOPLE WHERE SURNAME='O'Keefe' will become
SELECT * FROM PEOPLE WHERE SURNAME='\'O\'Keefe\''
Found in under 30s on Google...
Oracle SQL FAQ