This question already has answers here:
How can prepared statements protect from SQL injection attacks?
(10 answers)
Closed 8 years ago.
I heard that separated SQL clause and args can protect against SQL injection. For example,
clause = SELECT * WHERE ID = ? AND NAME = ?
with ID = 23, and NAME = "Tom".
Can someone explain to me how it works?
Basically, you're making the distinction between data and the actual code (query part) very clear. You're telling the SQL server: this is clearly data and this is clearly code.
This way, you're basically skipping the part where the server has to pull apart the code and data from your query so there's no chance the server can misinterpret bits of data as part of your query.
Edit: as per the link in the comments, this answer pretty much answers your question much better than I've explained here.
Related
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Is there any way to trace\log the sql using Dapper?
(6 answers)
Closed 3 years ago.
Lets take an example:
const string PERSON_SQL = "SELECT Id " +
"FROM Persons " +
"WHERE LastName=#LastName AND FirstName=#FirstName";
patientId = connection.ExecuteScalar<int>(PERSON_SQL, new
{
LastName = _entity.Lastname,
FirstName = _entity.Firstname
});
I would like to print out actual SQL query with parameter values for debugging purposes. I am sure there is some extension or helper function for it...
Dapper doesn't include that functionality itself, the authors tend to use MiniProfiler for capturing SQL queries (see Marc Gravell's answer about something similar).
You could also use SQL Profiler, presuming you're using a SQL database.
Finally, if nothing "off the shelf" suits your needs, you could wrap the database connections and commands that you use with Dapper and capture / log the queries (and parameters) when ExecuteReader, ExecuteScalar, etc.. are called. I had some sample code for this in my answer to a question someone had about using Dapper with Access (though the sample code is database-agnostic, so you could use the "WrappedDbConnection" with whatever database you are using at the moment).
This question already has answers here:
How does SQLParameter prevent SQL Injection?
(4 answers)
How does the SQL injection from the "Bobby Tables" XKCD comic work?
(13 answers)
Closed 8 years ago.
I'm very early on in learning SQL, but I've encountered the topic of SQL injections, and understand that parameters are probably the best way to prevent them. But I couldn't find any explanation of what they actually ARE.
So, for instance, in this code in ASP.NET (from w3schools):
txtUserId = getRequestString("UserId");
sql = "SELECT * FROM Customers WHERE CustomerId = #0";
command = new SqlCommand(sql);
command.Parameters.AddWithValue("#0",txtUserID);
command.ExecuteReader();
What dos the "command.parameters.addwithvalue" actually do?
I'm sorry if this is a stupid question, but I couldn't find the answer to it - everywhere I look they just say "use parameters" but don't explain what that actually means...
Thanks!
actually you need to make prepared statement to stop sql injection , another thing is you need to escape the query or add slashed before single quotes in order to qvoid SQL Injection
Form w3schools
"Some web developers use a "blacklist" of words or characters to
search for in SQL input, to prevent SQL injection attacks.
This is not a very good idea. Many of these words (like delete or
drop) and characters (like semicolons and quotation marks), are used
in common language, and should be allowed in many types of input.
(In fact it should be perfectly legal to input an SQL statement in a
database field.)
The only proven way to protect a web site from SQL injection attacks,
is to use SQL parameters.
SQL parameters are values that are added to an SQL query at execution
time, in a controlled manner.
ASP.NET Razor Example
txtUserId = getRequestString("UserId"); txtSQL = "SELECT * FROM Users
WHERE UserId = #0"; db.Execute(txtSQL,txtUserId);
Note that parameters are represented in the SQL statement by a #
marker.
The SQL engine checks each parameter to ensure that it is correct for
its column and are treated literally, and not as part of the SQL to be
executed. Another Example txtNam = getRequestString("CustomerName");
txtAdd = getRequestString("Address"); txtCit =
getRequestString("City"); txtSQL = "INSERT INTO Customers
(CustomerName,Address,City) Values(#0,#1,#2)";
db.Execute(txtSQL,txtNam,txtAdd,txtCit);"
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
What does the colon sign “:” do in a SQL query?
Simple SQL question:
What does : stand for?
For example:
SELECT * FROM myTable
WHERE Employee_column = :P_EmplId;
The : isn't exactly easy to google when you don't know what this is called. Even searching here didn't help. I'm using Oracle 11g if that makes any difference.
It is a bind variable:
A placeholder in a SQL statement that must be replaced with a valid
value or value address for the statement to execute successfully. By
using bind variables, you can write a SQL statement that accepts
inputs or parameters at run time. The following example shows a query
that uses v_empid as a bind variable:
Most likely you took the query from a template. It is meant to be processed with php's MDB2 sql framework. The ":" (colon) signals a placeholder in the statement, meant to be replaced when the query is executed.
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
Site has been hacked via SQL Injection
Looks like one of my websites had a hacker attempt on it, my reports showed the following querystring data attempted:
QUERY_STRING = ID=-999.9%20UNION%20ALL%20SELECT%200x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536,0x31303235343830303536-
It failed because any integer parameter I always cast to an integer so you get mismatch errors if anything like this is tried (classic ASP). But I'm confused what the query above is attempting? It doesn't look like anything I've seen before.
take a look at:
Site has been hacked via SQL Injection
at a first look a guess it was some automatic tool doing some blind sql injection.
This question already has answers here:
What is the question mark's significance in MySQL at "WHERE column = ?"?
(4 answers)
What does a question mark represent in SQL queries?
(6 answers)
Closed 9 years ago.
I was just surfing the net and found a query something like:
sql = "select milk_rate from special_milk_rate
where code_producer_id=? and effective_from <= ?
and effective_till >= ?"
what exactly this query means i means what is the use of ? in this statement.
and one thing more what is use of & in sql.
This usually implies a prepared statement, where the parameters are filled in later. (see e.g. http://en.wikipedia.org/wiki/Prepared_statements#Parameterized_statements).
what exactly this query means i means what is the use of ? in this statement.
The question marks are for parameters.
and one thing more what is use of & in sql.
& is a bitwise AND operator in sql
The question marks are supposed to contain the actual parameters.
E.g.
"select milk_rate from special_milk_rate
where code_producer_id=2 and effective_from <= '20101231'
and effective_till >= '20110124'"
& usually denotes a variable or substitution value which you may be prompted for at run time
Here is nice article:
http://publib.boulder.ibm.com/infocenter/idshelp/v10/topic/com.ibm.sqls.doc/sqls610.htm#sii-02prep-18104
In some statements, parameters are
unknown when the statement is prepared
because a different value can be
inserted each time the statement is
executed. In these statements, you can
use a question-mark ( ? ) placeholder
where a parameter must be supplied
when the statement is executed.
Question marks are found in prepared statements, meaning it is parametrized and can be called again and again without having to reconstruct the whole sql statement, just by changing the parameters. Some frameworks use those that together with SqlCommands. Those encapsulate escaping and prevent sql injection attacks.
Some frameworks also allow named parameters.