The following piece of code is being highlighted as a security vulnerability to SQL injection attacks.
StringBuilder sb = new StringBuilder();
sb.Append("DROP DATABASE IF EXISTS " + dbname);
String **sqlCommText** = sb.ToString();
using (SqlCommand command = new SqlCommand(**sqlCommText**, connection))
{
connection.Open();
Namely the sqlCommText
I'm aware of creating prepared statements on DML sql like insert and updates but i dont think this works on DDL sql - i cant parameterize the dbname into the sql.
Any suggestions how this should be fixed?
Preventing SQL Injection here is pretty easy: query the names of all of the databases on the SQL Server like this:
SELECT name, QUOTENAME(name) as QName
FROM sys.databases
WHERE database_id > 4;
Then, before you execute the rest of your SQL code, just check that your dbname variable is in that list of names returned by the query and if it is, then use the corresponding QName in your query (this protects against odd characters in the database name and also against something called latent injection).
However, as I mentioned in the comments, stopping injection is the easy problem. The hard problem here is to make sure that that legitimate users do not accidentally drop the wrong database, and worse, that bad actors do not intentionally drop the wrong database(s).
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 read a lot of things about SQL injection and many arguments why you should avoid to build your query dynamically using plain code/concatenations within your cs.file
However, I have question and I need some advice from someone with more experience than me.
I created some DLL files in order to re-use my code in different projects and for that reason I was thinking generic.
I created these DLL files that contained all the logic/code of building SQL queries in a dynamic way + concatenation of statement. Thereafter, I add these DLL files as reference to my project.
This will be vulnerable to SQL Injection ? also is that insufficient procedure (time consuming/insufficient maintenance)?
Any advice would be appreciated.
If you are not processing your input that you are passing to your query (built at run time) you are vulnerable to SQL injection. Adding to dll or not doesn't makes any difference.
To overcome this you need to use parameterised queries. They have multiple advantages a part from security.
One reason that i can think of right now is that you have a text box. And your query is
"select * from table1 where name = '" + textbox1.Text;
Not lets assume that in textbox1 user enters Ehsan's. Your query will go bang and won't even execute.
Example of parameterised query
"select * from table1 where name = #Name"
yourCommand.Parameters.AddWithValue("#Name", textbox1.Text);
It's difficult to know for sure but if you do something like
string sql = "SELECT Field FROM Table WHERE Field = " + Somevar;
Then you are open to SQL injection if somevar comes from input of some kind (usually user input).
There is just no reason to do it as you can just do
string sql = "SELECT Field FROM Table WHERE Field = #myvar"
You should make sure you are using parameterized queries or stored procedures, etc.
And avoid using dynamic SQL queries such as
"SELECT * FROM Users WHERE UserID = " + UserID
as these are vulnerable to SQL Injection
Instead use a parameterized query or a stored procedure, e.g.
"SELECT * FROM Users WHERE UserID = #UserID"
Most ORMs (eg .NET's Entity Framework) will provide some protection against SQL Injection (but only if used properly)
this link explains in more detail http://www.troyhunt.com/2013/07/everything-you-wanted-to-know-about-sql.html