I have a page that will generate an AuthKey for my web-app. I am using an Access Database database (just to try it locally, later on I will step to SQL Server). In my code-behind I am using C# as my writing language.
This is my code:
using System.Data.OleDb;
OleDBCommand cmd = new OleDBCommand();
cmd.CommandText = "insert into AuthKeys (AuthKey, User_Assign,locatedAt) values(#AuthKey, #idstr, 'Dashboard')";
cmd.Parameters.Add("#AuthKey", OleDbTypes.<sometype>).Value = AuthKey;
cmd.Parameters.Add("#idstr", OleDbTypes.<sometype>).Value = idstr;
the idstr == the userName
the AuthKey == code generated key (GUID)
But as I noticed, this application is very vulnerable for SQL Injection. So my question is: how can I prevent SQL Injection?
EDIT: My question is related to this forum post: https://social.msdn.microsoft.com/Forums/sqlserver/en-US/94608549-6fee-4c01-82ae-601ed7c20327/getting-errors-with-insert-into?forum=sqlnetfx#e933c92b-8d0a-4b40-906f-2d335b30b6d4
But as I noticed, this application is very vulnerable for SQL Injection.
No, it is not. You cannot tamper with the actual SQL statement since you use parameters already. There is no SQL injection vulnerability in your code.
There's a difference between unauthorized injection of code that executes in the script to perform unwanted behavior in your SQL statements and simply inserting data into the table that you don't want.
In this case, you'd likely be wanting something more on the validation side of things to prevent these unwanted record entries.
Quite the contrary, this approach (using prepared statements and parameterized queries) is the only sensible and reliable way of avoiding SQL injectons.
Mind you, if you're doing weird SQL trickery on the back end (like concatenating parameter values to get "dynamic SQL"-like behavior), you can still be bitten by SQL injection.
Related
This question already has answers here:
How can I add user-supplied input to an SQL statement?
(2 answers)
Closed 7 years ago.
I have to program an application management system for my OJT company. The front end will be done in C# and the back end in SQL.
Now I have never done a project of this scope before; in school we had only basic lessons about SQL. Somehow our teacher completely failed to discuss SQL injections, something which I have only now come in contact with by reading about it on the net.
So anyway my question is: how do you prevent SQL injections in C#? I vaguely think that it can be done by properly masking the text fields of the application so that it only accepts input in a specified format. For example: an e-mail textbox should be of the format "example#examplecompany.tld". Would this approach be sufficient? Or does .NET have pre-defined methods that handle stuff like this? Can I apply a filter to a textbox so it only accepts email-address format or a name textbox so it doesn't accept special chars?
By using the SqlCommand and its child collection of parameters all the pain of checking for sql injection is taken away from you and will be handled by these classes.
Here is an example, taken from one of the articles above:
private static void UpdateDemographics(Int32 customerID,
string demoXml, string connectionString)
{
// Update the demographics for a store, which is stored
// in an xml column.
string commandText = "UPDATE Sales.Store SET Demographics = #demographics "
+ "WHERE CustomerID = #ID;";
using (SqlConnection connection = new SqlConnection(connectionString))
{
SqlCommand command = new SqlCommand(commandText, connection);
command.Parameters.Add("#ID", SqlDbType.Int);
command.Parameters["#ID"].Value = customerID;
// Use AddWithValue to assign Demographics.
// SQL Server will implicitly convert strings into XML.
command.Parameters.AddWithValue("#demographics", demoXml);
try
{
connection.Open();
Int32 rowsAffected = command.ExecuteNonQuery();
Console.WriteLine("RowsAffected: {0}", rowsAffected);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
My answer is quite easy:
Use Entity Framework for communication between C# and your SQL database. That will make parameterized SQL strings that isn't vulnerable to SQL injection.
As a bonus, it's very easy to work with as well.
SQL injection can be a tricky problem but there are ways around it. Your risk is reduced your risk simply by using an ORM like Linq2Entities, Linq2SQL, NHibrenate. However you can have SQL injection problems even with them.
The main thing with SQL injection is user controlled input (as is with XSS). In the most simple example if you have a login form (I hope you never have one that just does this) that takes a username and password.
SELECT * FROM Users WHERE Username = '" + username + "' AND password = '" + password + "'"
If a user were to input the following for the username Admin' -- the SQL Statement would look like this when executing against the database.
SELECT * FROM Users WHERE Username = 'Admin' --' AND password = ''
In this simple case using a paramaterized query (which is what an ORM does) would remove your risk. You also have a the issue of a lesser known SQL injection attack vector and that's with stored procedures. In this case even if you use a paramaterized query or an ORM you would still have a SQL injection problem. Stored procedures can contain execute commands, and those commands themselves may be suceptable to SQL injection attacks.
CREATE PROCEDURE SP_GetLogin #username varchar(100), #password varchar(100) AS
DECLARE #sql nvarchar(4000)
SELECT #sql = ' SELECT * FROM users' +
' FROM Product Where username = ''' + #username + ''' AND password = '''+#password+''''
EXECUTE sp_executesql #sql
So this example would have the same SQL injection problem as the previous one even if you use paramaterized queries or an ORM. And although the example seems silly you'd be surprised as to how often something like this is written.
My recommendations would be to use an ORM to immediately reduce your chances of having a SQL injection problem, and then learn to spot code and stored procedures which can have the problem and work to fix them. I don't recommend using ADO.NET (SqlClient, SqlCommand etc...) directly unless you have to, not because it's somehow not safe to use it with parameters but because it's that much easier to get lazy and just start writing a SQL query using strings and just ignoring the parameters. ORMS do a great job of forcing you to use parameters because it's just what they do.
Next Visit the OWASP site on SQL injection https://www.owasp.org/index.php/SQL_Injection and use the SQL injection cheat sheet to make sure you can spot and take out any issues that will arise in your code. https://www.owasp.org/index.php/SQL_Injection_Prevention_Cheat_Sheet finally I would say put in place a good code review between you and other developers at your company where you can review each others code for things like SQL injection and XSS. A lot of times programmers miss this stuff because they're trying to rush out some feature and don't spend too much time on reviewing their code.
SQL injection should not be prevented by trying to validate your input; instead, that input should be properly escaped before being passed to the database.
How to escape input totally depends on what technology you are using to interface with the database. In most cases and unless you are writing bare SQL (which you should avoid as hard as you can) it will be taken care of automatically by the framework so you get bulletproof protection for free.
You should explore this question further after you have decided exactly what your interfacing technology will be.
This question already has answers here:
How can I add user-supplied input to an SQL statement?
(2 answers)
Closed 7 years ago.
I have to program an application management system for my OJT company. The front end will be done in C# and the back end in SQL.
Now I have never done a project of this scope before; in school we had only basic lessons about SQL. Somehow our teacher completely failed to discuss SQL injections, something which I have only now come in contact with by reading about it on the net.
So anyway my question is: how do you prevent SQL injections in C#? I vaguely think that it can be done by properly masking the text fields of the application so that it only accepts input in a specified format. For example: an e-mail textbox should be of the format "example#examplecompany.tld". Would this approach be sufficient? Or does .NET have pre-defined methods that handle stuff like this? Can I apply a filter to a textbox so it only accepts email-address format or a name textbox so it doesn't accept special chars?
By using the SqlCommand and its child collection of parameters all the pain of checking for sql injection is taken away from you and will be handled by these classes.
Here is an example, taken from one of the articles above:
private static void UpdateDemographics(Int32 customerID,
string demoXml, string connectionString)
{
// Update the demographics for a store, which is stored
// in an xml column.
string commandText = "UPDATE Sales.Store SET Demographics = #demographics "
+ "WHERE CustomerID = #ID;";
using (SqlConnection connection = new SqlConnection(connectionString))
{
SqlCommand command = new SqlCommand(commandText, connection);
command.Parameters.Add("#ID", SqlDbType.Int);
command.Parameters["#ID"].Value = customerID;
// Use AddWithValue to assign Demographics.
// SQL Server will implicitly convert strings into XML.
command.Parameters.AddWithValue("#demographics", demoXml);
try
{
connection.Open();
Int32 rowsAffected = command.ExecuteNonQuery();
Console.WriteLine("RowsAffected: {0}", rowsAffected);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
My answer is quite easy:
Use Entity Framework for communication between C# and your SQL database. That will make parameterized SQL strings that isn't vulnerable to SQL injection.
As a bonus, it's very easy to work with as well.
SQL injection can be a tricky problem but there are ways around it. Your risk is reduced your risk simply by using an ORM like Linq2Entities, Linq2SQL, NHibrenate. However you can have SQL injection problems even with them.
The main thing with SQL injection is user controlled input (as is with XSS). In the most simple example if you have a login form (I hope you never have one that just does this) that takes a username and password.
SELECT * FROM Users WHERE Username = '" + username + "' AND password = '" + password + "'"
If a user were to input the following for the username Admin' -- the SQL Statement would look like this when executing against the database.
SELECT * FROM Users WHERE Username = 'Admin' --' AND password = ''
In this simple case using a paramaterized query (which is what an ORM does) would remove your risk. You also have a the issue of a lesser known SQL injection attack vector and that's with stored procedures. In this case even if you use a paramaterized query or an ORM you would still have a SQL injection problem. Stored procedures can contain execute commands, and those commands themselves may be suceptable to SQL injection attacks.
CREATE PROCEDURE SP_GetLogin #username varchar(100), #password varchar(100) AS
DECLARE #sql nvarchar(4000)
SELECT #sql = ' SELECT * FROM users' +
' FROM Product Where username = ''' + #username + ''' AND password = '''+#password+''''
EXECUTE sp_executesql #sql
So this example would have the same SQL injection problem as the previous one even if you use paramaterized queries or an ORM. And although the example seems silly you'd be surprised as to how often something like this is written.
My recommendations would be to use an ORM to immediately reduce your chances of having a SQL injection problem, and then learn to spot code and stored procedures which can have the problem and work to fix them. I don't recommend using ADO.NET (SqlClient, SqlCommand etc...) directly unless you have to, not because it's somehow not safe to use it with parameters but because it's that much easier to get lazy and just start writing a SQL query using strings and just ignoring the parameters. ORMS do a great job of forcing you to use parameters because it's just what they do.
Next Visit the OWASP site on SQL injection https://www.owasp.org/index.php/SQL_Injection and use the SQL injection cheat sheet to make sure you can spot and take out any issues that will arise in your code. https://www.owasp.org/index.php/SQL_Injection_Prevention_Cheat_Sheet finally I would say put in place a good code review between you and other developers at your company where you can review each others code for things like SQL injection and XSS. A lot of times programmers miss this stuff because they're trying to rush out some feature and don't spend too much time on reviewing their code.
SQL injection should not be prevented by trying to validate your input; instead, that input should be properly escaped before being passed to the database.
How to escape input totally depends on what technology you are using to interface with the database. In most cases and unless you are writing bare SQL (which you should avoid as hard as you can) it will be taken care of automatically by the framework so you get bulletproof protection for free.
You should explore this question further after you have decided exactly what your interfacing technology will be.
This question already has answers here:
How can I add user-supplied input to an SQL statement?
(2 answers)
Closed 7 years ago.
I have to program an application management system for my OJT company. The front end will be done in C# and the back end in SQL.
Now I have never done a project of this scope before; in school we had only basic lessons about SQL. Somehow our teacher completely failed to discuss SQL injections, something which I have only now come in contact with by reading about it on the net.
So anyway my question is: how do you prevent SQL injections in C#? I vaguely think that it can be done by properly masking the text fields of the application so that it only accepts input in a specified format. For example: an e-mail textbox should be of the format "example#examplecompany.tld". Would this approach be sufficient? Or does .NET have pre-defined methods that handle stuff like this? Can I apply a filter to a textbox so it only accepts email-address format or a name textbox so it doesn't accept special chars?
By using the SqlCommand and its child collection of parameters all the pain of checking for sql injection is taken away from you and will be handled by these classes.
Here is an example, taken from one of the articles above:
private static void UpdateDemographics(Int32 customerID,
string demoXml, string connectionString)
{
// Update the demographics for a store, which is stored
// in an xml column.
string commandText = "UPDATE Sales.Store SET Demographics = #demographics "
+ "WHERE CustomerID = #ID;";
using (SqlConnection connection = new SqlConnection(connectionString))
{
SqlCommand command = new SqlCommand(commandText, connection);
command.Parameters.Add("#ID", SqlDbType.Int);
command.Parameters["#ID"].Value = customerID;
// Use AddWithValue to assign Demographics.
// SQL Server will implicitly convert strings into XML.
command.Parameters.AddWithValue("#demographics", demoXml);
try
{
connection.Open();
Int32 rowsAffected = command.ExecuteNonQuery();
Console.WriteLine("RowsAffected: {0}", rowsAffected);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
My answer is quite easy:
Use Entity Framework for communication between C# and your SQL database. That will make parameterized SQL strings that isn't vulnerable to SQL injection.
As a bonus, it's very easy to work with as well.
SQL injection can be a tricky problem but there are ways around it. Your risk is reduced your risk simply by using an ORM like Linq2Entities, Linq2SQL, NHibrenate. However you can have SQL injection problems even with them.
The main thing with SQL injection is user controlled input (as is with XSS). In the most simple example if you have a login form (I hope you never have one that just does this) that takes a username and password.
SELECT * FROM Users WHERE Username = '" + username + "' AND password = '" + password + "'"
If a user were to input the following for the username Admin' -- the SQL Statement would look like this when executing against the database.
SELECT * FROM Users WHERE Username = 'Admin' --' AND password = ''
In this simple case using a paramaterized query (which is what an ORM does) would remove your risk. You also have a the issue of a lesser known SQL injection attack vector and that's with stored procedures. In this case even if you use a paramaterized query or an ORM you would still have a SQL injection problem. Stored procedures can contain execute commands, and those commands themselves may be suceptable to SQL injection attacks.
CREATE PROCEDURE SP_GetLogin #username varchar(100), #password varchar(100) AS
DECLARE #sql nvarchar(4000)
SELECT #sql = ' SELECT * FROM users' +
' FROM Product Where username = ''' + #username + ''' AND password = '''+#password+''''
EXECUTE sp_executesql #sql
So this example would have the same SQL injection problem as the previous one even if you use paramaterized queries or an ORM. And although the example seems silly you'd be surprised as to how often something like this is written.
My recommendations would be to use an ORM to immediately reduce your chances of having a SQL injection problem, and then learn to spot code and stored procedures which can have the problem and work to fix them. I don't recommend using ADO.NET (SqlClient, SqlCommand etc...) directly unless you have to, not because it's somehow not safe to use it with parameters but because it's that much easier to get lazy and just start writing a SQL query using strings and just ignoring the parameters. ORMS do a great job of forcing you to use parameters because it's just what they do.
Next Visit the OWASP site on SQL injection https://www.owasp.org/index.php/SQL_Injection and use the SQL injection cheat sheet to make sure you can spot and take out any issues that will arise in your code. https://www.owasp.org/index.php/SQL_Injection_Prevention_Cheat_Sheet finally I would say put in place a good code review between you and other developers at your company where you can review each others code for things like SQL injection and XSS. A lot of times programmers miss this stuff because they're trying to rush out some feature and don't spend too much time on reviewing their code.
SQL injection should not be prevented by trying to validate your input; instead, that input should be properly escaped before being passed to the database.
How to escape input totally depends on what technology you are using to interface with the database. In most cases and unless you are writing bare SQL (which you should avoid as hard as you can) it will be taken care of automatically by the framework so you get bulletproof protection for free.
You should explore this question further after you have decided exactly what your interfacing technology will be.
This question already has answers here:
How can I add user-supplied input to an SQL statement?
(2 answers)
Closed 7 years ago.
I have to program an application management system for my OJT company. The front end will be done in C# and the back end in SQL.
Now I have never done a project of this scope before; in school we had only basic lessons about SQL. Somehow our teacher completely failed to discuss SQL injections, something which I have only now come in contact with by reading about it on the net.
So anyway my question is: how do you prevent SQL injections in C#? I vaguely think that it can be done by properly masking the text fields of the application so that it only accepts input in a specified format. For example: an e-mail textbox should be of the format "example#examplecompany.tld". Would this approach be sufficient? Or does .NET have pre-defined methods that handle stuff like this? Can I apply a filter to a textbox so it only accepts email-address format or a name textbox so it doesn't accept special chars?
By using the SqlCommand and its child collection of parameters all the pain of checking for sql injection is taken away from you and will be handled by these classes.
Here is an example, taken from one of the articles above:
private static void UpdateDemographics(Int32 customerID,
string demoXml, string connectionString)
{
// Update the demographics for a store, which is stored
// in an xml column.
string commandText = "UPDATE Sales.Store SET Demographics = #demographics "
+ "WHERE CustomerID = #ID;";
using (SqlConnection connection = new SqlConnection(connectionString))
{
SqlCommand command = new SqlCommand(commandText, connection);
command.Parameters.Add("#ID", SqlDbType.Int);
command.Parameters["#ID"].Value = customerID;
// Use AddWithValue to assign Demographics.
// SQL Server will implicitly convert strings into XML.
command.Parameters.AddWithValue("#demographics", demoXml);
try
{
connection.Open();
Int32 rowsAffected = command.ExecuteNonQuery();
Console.WriteLine("RowsAffected: {0}", rowsAffected);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
My answer is quite easy:
Use Entity Framework for communication between C# and your SQL database. That will make parameterized SQL strings that isn't vulnerable to SQL injection.
As a bonus, it's very easy to work with as well.
SQL injection can be a tricky problem but there are ways around it. Your risk is reduced your risk simply by using an ORM like Linq2Entities, Linq2SQL, NHibrenate. However you can have SQL injection problems even with them.
The main thing with SQL injection is user controlled input (as is with XSS). In the most simple example if you have a login form (I hope you never have one that just does this) that takes a username and password.
SELECT * FROM Users WHERE Username = '" + username + "' AND password = '" + password + "'"
If a user were to input the following for the username Admin' -- the SQL Statement would look like this when executing against the database.
SELECT * FROM Users WHERE Username = 'Admin' --' AND password = ''
In this simple case using a paramaterized query (which is what an ORM does) would remove your risk. You also have a the issue of a lesser known SQL injection attack vector and that's with stored procedures. In this case even if you use a paramaterized query or an ORM you would still have a SQL injection problem. Stored procedures can contain execute commands, and those commands themselves may be suceptable to SQL injection attacks.
CREATE PROCEDURE SP_GetLogin #username varchar(100), #password varchar(100) AS
DECLARE #sql nvarchar(4000)
SELECT #sql = ' SELECT * FROM users' +
' FROM Product Where username = ''' + #username + ''' AND password = '''+#password+''''
EXECUTE sp_executesql #sql
So this example would have the same SQL injection problem as the previous one even if you use paramaterized queries or an ORM. And although the example seems silly you'd be surprised as to how often something like this is written.
My recommendations would be to use an ORM to immediately reduce your chances of having a SQL injection problem, and then learn to spot code and stored procedures which can have the problem and work to fix them. I don't recommend using ADO.NET (SqlClient, SqlCommand etc...) directly unless you have to, not because it's somehow not safe to use it with parameters but because it's that much easier to get lazy and just start writing a SQL query using strings and just ignoring the parameters. ORMS do a great job of forcing you to use parameters because it's just what they do.
Next Visit the OWASP site on SQL injection https://www.owasp.org/index.php/SQL_Injection and use the SQL injection cheat sheet to make sure you can spot and take out any issues that will arise in your code. https://www.owasp.org/index.php/SQL_Injection_Prevention_Cheat_Sheet finally I would say put in place a good code review between you and other developers at your company where you can review each others code for things like SQL injection and XSS. A lot of times programmers miss this stuff because they're trying to rush out some feature and don't spend too much time on reviewing their code.
SQL injection should not be prevented by trying to validate your input; instead, that input should be properly escaped before being passed to the database.
How to escape input totally depends on what technology you are using to interface with the database. In most cases and unless you are writing bare SQL (which you should avoid as hard as you can) it will be taken care of automatically by the framework so you get bulletproof protection for free.
You should explore this question further after you have decided exactly what your interfacing technology will be.
I have created a small survey web page on our company Intranet. This web page is not accessible from the outside.
The form is simply a couple of radio buttons and a comments box.
I would like to maintain good coding practices and would like to guard against SQL Injections.
Can SQL injections happen on a insert statement with comments from the textbox?
If so, how can I guard against it using .NET 2.0?
Injection can happen on any SQL statement not run properly.
For example, let's pretend your comment table has two fields, an integer ID and the comment string. So you'd INSERT as follows:
INSERT INTO COMMENTS VALUES(122,'I like this website');
Consider someone entering the following comment:
'); DELETE FROM users; --
If you just put the comment string into the SQL without any processesing this could turn your single INSERT in to the following two statements followed by a comment:
INSERT INTO COMMENTS VALUES(123,''); DELETE FROM users; -- ');
This would delete everything from your users table. And there are people willing to spend all day finding the right tablename to empty using trial and error and various tricks. Here's a description of how you could perform an SQL Injection attack.
You need to use parameterized SQL statements to prevent this.
And this isn't just for security reasons. For example, if you're creating your SQL statements naively the following comment:
I'm just loving this website
would cause an SQL syntax error because of the apostrophe being interpreted by SQL as a closing quote.
Use parameterized queries so that the text is automatically quoted for you.
SqlCommand command = connection.CreateCommand();
command.CommandText = "insert into dbo.Table (val1,val2,txt) values (#val1,#val2,#txt)";
command.AddParameterWithValue( "val1", value1 );
command.AddParameterWithValue( "val2", value2 );
command.AddParameterWithValue( "txt", text );
...
SQL injection can happen any time you pass a query back to the database. Here's a simple demonstration:
SQL Injection Explained
The key, within .NET, is to do as Dave Webb has given. It will prevent the injection attempt by encompassing the entire string as one parameter to be submitted, handling all characters that might be interpreted by SQL Server to change the query or append additional commands.
And it should be pointed out that SQL injection can occur on any application, not just web applications. And that an internal attack is usually the most costly to an organization. One cannot safely assume that an attack won't originate from within.
In addition to using prepared statements and parameters rather than concatenating strings into your SQL you should also do the following:
Validate and format user input on the server side. Client side validation and limits can easily be bypasses with tools like WebScarab, or by spoofing your form.
Configure appropriate permissions for the database user account. Web application should use a separate account or role in your database with permissions restricted to only the tables, views and procedures required to run your application. Make sure that user does not have select rights on the system tables
Hide detailed error messages from users, and use less common names for your objects. It amazes me how often you can determine the server type (oracle, mysql, sqlserver) and find basic schema information in an error message and then get information from tables called 'user(s)', 'employee(s)'. If you haven't set your permissions as in (2) and I can determine your server type you are open to statements like this for SQL Server
SELECT table_name FROM information_schema.table
EXECUTE sp_help foundTableName
Yes, they can happen. The easiest way to guard against this is to use prepared statements rather than building the SQL manually.
So, rather than this:
String sql =
String.Format("INSERT INTO mytable (text_column) VALUES ( '{0}' )",
myTextBox.Text); // Unsafe!
You would do something like this:
String sql = "INSERT INTO mytable (text_column) VALUES ( ? )"; // Much safer
Then add the text of the text box as a parameter to your DbCommand which will cause it to be automatically escaped and replace the "?" in the SQL.
Prevent SQL Injection by using prepared statement. The use of placehoder(?) totally eliminates sql Injection Vulnerability.
example
String sql=Select * from user_table where username='+request.getparameter("username")+';
statement.executeQuery(sql);
the above statement is vulnerable to sql injection.
To make it safe against sql injection.
Use following the snippet
String sql=Select * from user_table where username=?;
statement.setString(1,username);
Yes, it can. Let's say the client sends this:
OR 1 = 1
That can be very painfull for your
SELECT * FROM admin WHERE name = #name AND password = #password
You can prevent this with
using Parameter class from ADO.NET
using regexp
reading, reading: http://www.codeproject.com/KB/database/SqlInjectionAttacks.aspx
The easiest way to guard against that form of SQL injection, is to use parameters and stored procedures rather then building sql statements to run. (In C# or internally to SQL Server).
However I'm not entirely sure you should be spending time on this, unless of course it's your corporate policy, as the chances of it ever occuring internally are minimal at best, and if it did occur, I would hope you would know immediately who it is.