I have a SQL statement similar to the one shown below in Perl:
my $sql="abc..TableName '$a','$b' ";
The $a is free text which can contain anything including single quotes, double quotes, back- and front-slash characters, etc.
How can these characters be escaped to make the SQL statement work?
Thanks.
You can either use the ->quote method (assuming you're using DBI):
my $oldValue = $dbh->quote('oldValue');
my $newValue = $dbh->quote('newValue');
$dbh->do("UPDATE myTable SET myValue=$newValue where myValue=$oldValue");
Better still, the best practice is to use bind values:
my $sth = $dbh->prepare('UPDATE myTable SET myValue=? WHERE myValue=?');
$sth->execute('newValue','oldValue');
This should also work for stored procedure calls, assuming the statement once the strings have been expanded is valid SQL. This may be driver/DB specific so YMMV.
my $sth = $dbh->prepare("DBName..ProcName ?,? ");
$sth->execute($a, $b);
Use a prepared statement. Replace the variable with a ?. To crib an example from DBI manpages:
$sql = 'SELECT * FROM people WHERE lastname = ?';
$sth = $dbh->prepare($sql);
$sth->execute($user_input_here);
Interpolating user input into your SQL is asking for security holes.
If you use query parameter placeholders, you don't have to escape the content of the strings.
my $sql="DBName..ProcName ?, ?";
$sth = $dbh->prepare($sql);
$sth->execute($a, $b);
If the DBI is using true query parameters, it sends the parameter values to the RDBMS separately from the SQL statement. The values are never combined with the SQL statement string, therefore the values never have an opportunity to cause SQL injection.
If the DBI is "emulating" prepared statements by interpolating the variables into the query string, then DBI should handle the correct escaping logic so you don't have to. Let the experts (those who write and test DBI) worry about how to do it.
If you don't want to use ->quote (for some reason, this function doesn't run on my version of DBI) then try this:
$query=~s/\"/\\\"/g;
I tend to do the same with single quotes and commas too just to be safe.
Seems to work fine for me...!
Related
I have some automated workflow, which includes updating a column via SQL with HTML tags in it.
The basic SQL statement goes like this:
UPDATE content SET bodytext = '<div class="one two three">Here comes a whole lot of HTML with all special chars and double quotes " and single quotes ' and empty lines and all possible kind of stuff...</div>' WHERE pid = 10;
Is there a way to make MariaDB or MySQL to escape things automatically in SQL (without PHP)?
I'd suggest to use prepared statements. This way you separate the statement from it's parameters and don't need to care about additional escaping necessary in plain SQL.
Using functionality provided in PHP's MySQLi driver would simplify the process:
https://www.w3schools.com/php/php_mysql_prepared_statements.asp
Prepared statements are also possible in plain SQL, but I'm not sure if doing it manually would be worth the hassle
https://dev.mysql.com/doc/refman/8.0/en/sql-prepared-statements.html
Thank you for your input, but I think, I found a solution which works for me. It seems that you actually can tell the SQL server to accept a raw string by this kind of syntax:
SELECT q'[The 'end' of the day]'
(Source: https://www.databasestar.com/sql-escape-single-quote/)
So I did the following:
SELECT #html := '[<div class="one two three">Here comes a whole lot of HTML with all special chars and double quotes " and single quotes '' and empty lines and all possible kind of stuff...</div>]';
UPDATE content SET bodytext = #html WHERE pid = 10;
And it works that way without any escaping problems.
$id = $_GET['id'];
$id = str_replace("'", "", $id);
$sql = "select name from test where id='$id'";
$stmt = $conn->query($sql);
As the php code snippet above, it removes all single quotes from the user input, and then put it in a sql query, whaterver it gets from the user is not able to escape from the quotes surrounding them, it seems safe from sql injection. I am quite curious about how to inject sql code to this.
Some question said about escaping quotes, which has examples to exploit it. But in my occasion, removing all quotes isn't really the same as escaping.
I know there is the parameterized query way to prevent sql injection. And yes, it's possible that single quotes may be contained in legitimate data. I am asking this question out of curiosity while learing sql injection, all I want to know is there are any examples to exploit this code?
If you don't want to use parameterization or escaping, and assuming your id is an integer, you could use typecasting. This is totally safe, and faster code than calling a function to do string replacement:
$id = (int) $_GET['id'];
$sql = "select name from test WHERE id=$id";
$stmt = $conn->query($sql);
But you should just get into the habit of using parameters. It's simple and fast. It works for strings, even if the strings contain special characters like quotes.
It's super easy in PDO, and it takes just one extra line of code:
$id = $_GET['id'];
$sql = "select name from test WHERE id=?";
$stmt = $conn->prepare($sql);
$stmt->execute([$id]);
my question [is], is it safe to remove quotes for string fields?
No. Don't do this. You don't know enough to do this safely. For example, what about backslash (\)? And other special characters?
Do you know why the internal MySQL API https://dev.mysql.com/doc/refman/5.7/en/mysql-real-escape-string.html escapes more than just the quotes? This is the list of characters that are escaped:
\, ', ", NUL (ASCII 0), \n, \r, and Control+Z
So is it enough to remove these characters? No, you still have to think about character sets and hex-encoded characters.
There's no reason to do this. You already have more reliable solutions to make SQL queries safe.
Don't get fixated on your remove-the-quote solution. It's not sufficient.
I am still getting my head around a PDO statement but the code below does not do what I assumed it would
$temp = "6c ";
$weather_report = "Its currently $temp " ;
$qry = $pdo->exec("UPDATE data_weather SET text= '$weather_report' WHERE period='report' ");
This does update my database but only with 'Its currently' and the temp value is missing ,
After reading some articles I believe I need to use quote but I am not sure how to implement it ?
any help please ?
Please use query parameters instead of interpolating variables into SQL strings.
It's safer, faster, and easier.
$temp = "6c ";
$weather_report = "It's currently $temp " ;
$sql = "UPDATE data_weather SET text= ? WHERE period='report'";
$stmt = $pdo->prepare($sql);
$stmt->execute(array($weather_report));
Note that you don't need to quote the string. In fact, you must not put quotes around the ? placeholder. You can use apostrophes inside your weather report string safely.
You can use a parameter placeholder any place you would normally put a single scalar value in an SQL expression. E.g. in place of a quoted string, quoted date, or numeric literal. But not for table names or column names, or for lists of values, or SQL keywords.
Although Bill has already answered the question, I'd like to add:
Do not use named parameters with TEXT columns, at least not with MySQL. It won't work. Use question marks instead.
While I was trying the following SQL command , I got sql error.
INSERT INTO exampleTbl VALUES('he doesn't work for me')
where doesn't contain the apostrophe.
What is the way to insert text having ' (apostrophe) into a SQL table.
In SQL, the way to do this is to double the apostrophe:
'he doesn''t work for me'
However, if you are doing this programmatically, you should use an API that accepts parameters and escapes them for you automatically. Programmatically escaping and using string concatenation to assemble a query yourself is a sure way to end up with SQL injection vulnerabilities.
INSERT INTO exampleTbl VALUES('he doesn''t work for me')
If you're adding a record through ASP.NET, you can use the SqlParameter object to pass in values so you don't have to worry about the apostrophe's that users enter in.
$value = "he doesn't work for me";
$new_value = str_replace("'", "''", "$value"); // it looks like " ' " , " ' ' "
INSERT INTO exampleTbl (`column`) VALUES('$new_value')
try this
INSERT INTO exampleTbl VALUES('he doesn''t work for me')
insert into table1 values("sunil''s book",123,99382932938);
use double apostrophe inside of single apostrophe,
it will work
I know the question is aimed at the direct escaping of the apostrophe character but I assume that usually this is going to be triggered by some sort of program providing the input.
What I have done universally in the scripts and programs I have worked with is to substitute it with a ` character when processing the formatting of the text being input.
Now I know that in some cases, the backtick character may in fact be part of what you might be trying to save (such as on a forum like this) but if you're simply saving text input from users it's a possible solution.
Going into the SQL database
$newval=~s/\'/`/g;
Then, when coming back out for display, filtered again like this:
$showval=~s/`/\'/g;
This example was when PERL/CGI is being used but it can apply to PHP and other bases as well. I have found it works well because I think it helps prevent possible injection attempts, because all ' are removed prior to attempting an insertion of a record.
yes, sql server doesn't allow to insert single quote in table field due to the sql injection attack. so we must replace single appostrophe by double while saving.
(he doesn't work for me) must be => (he doesn''t work for me)
you can use backslash '\' if you want to display a single quote in your text.
INSERT INTO exampleTbl VALUES('He doesn(\')t') ;
I have the following problem, when I pass GString to SQL.executeInsert, the text variables are not automatically souranded by ' so the insert query failes:
String value4fa = "I would like to get know"
int value4fb = 2
def query = "INSERT INTO TAB_A (F_A, F_B) VALUES (${value4fa}, ${value4fb})"
sql.executeInsert(query);
If I put ' by myself:
def query = "INSERT INTO TAB_A (F_A, F_B) VALUES ('${value4fa}', ${value4fb})"
Groovy informs me that I have introduced a security hole, because Groovy can not use PreparedStatement to execute the SQL query.
Could anybody explain me how to force Groovy to evaluate query body correctly and prepare the variables?
You should not have to decorate strings with anything to have them converted to PreparedStatement automatically.
sql.execute("INSERT INTO TAB_A (F_A, F_B) VALUES ($value4fa, $value4fb)")
will do the correct thing for all the methods that accept a GString as a single parameter. note the lack of {} which is syntactic sugar for .toString()
The reason yours causes the complaint is that,
def query = "INSERT INTO TAB_A (F_A, F_B) VALUES (${value4fa}, ${value4fb})"
sql.execute(query)
is different than passing the GString directly to the method.
it applies the substitutions before passing query to the .execute() method. Given your example data, it passes the following to and the replacements have already happened. "INSERT INTO TAB_A (F_A, F_B) VALUES (I would like to get know, 2)" which is not even a valid SQL statement because the string value is missing the ' around it.
This is functionally equivalent to using String.format(), StringBuilder/Buffer.append() or plain on concatenation using +.
I have not tested this idea, but the code for 2.4.4 is here.
The execute(String sql, List<Object> params) method uses prepared statements.
Given that, consider this example:
firstName = "yue"
lastName = "wu"
sql.execute("insert into people (firstName, lastName) "+
" values (?,?)", [firstName, lastName])
If necessary, it is easy to add single-quotes to the variables themselves (rather than the SQL string).