Sql Injection Attacks And Defense Pdf File

Sql injection attacks and defense pdf file

Indeed, they go hand in hand because XSS attacks are contingent on a successful Injection attack. While this is the most obvious partnership, Injection is not just limited to enabling XSS. Injection is an entire class of attacks that rely on injecting data into a web application in order to facilitate the execution or interpretation of malicious data in an unexpected manner. They are the most common and successful attacks on the internet due to their numerous types, large attack surface, and the complexity sometimes needed to protect against them.

All applications need data from somewhere in order to function.

Sql injection attacks and defense pdf file

SQL Injections are not only extremely common but also very deadly. I cannot emphasise enough the importance of understanding this attack, the conditions under which it can be successfully accomplished and the steps required to defend against it.

The data usually comes from untrusted input such as a web form. Programmers will often trust data from their own database believing it to be completely safe without realising that being safe for one particular usage does not mean it is safe for all other subsequent usages. Data from a database should be treated as untrusted unless proven otherwise, e. If successful, an SQL Injection can manipulate the SQL query being targeted to perform a database operation not intended by the programmer.

SQL injection: attacks and defenses

The above has a number of things wrong with it. Names are reasonably broad in scope and may include quotes. When we reuse that string in a later query, it would then manipulate the query string if we considered the database a trusted source of data and failed to properly escape or bind it. Another factor of SQL Injection to pay attention to is that persistent storage need not always occurs on the server. It should be validated to ensure it is in the correct form we expect before using it in a SQL query and it should be escaped before including it in the query or by including it as a bound parameter.

Chapter 2 covered Input Validation and, as I then noted, we should assume that all data not created explicitly in the PHP source code of the current request should be considered untrusted.

SQL Injection Attacks and Defense, 2nd Edition PDF Free Download

Validate it strictly and reject all failing data. Common validation mistakes can include validating the data for its then current use e. Just to give you even more of a headache, you can never ever fail to escape data entering an SQL query.

Sql injection attacks and defense pdf file

One slip, and it will possibly be vulnerable to SQL Injection. For the reasons above, escaping is not really recommended. It will do in a pinch and might be necessary if a database library you use for abstraction allows the setting of naked SQL queries or query parts without enforcing parameter binding.

Otherwise you should just avoid the need to escape altogether. Parameterisation or Parameter Binding is the recommended way to construct SQL queries and all good database libraries will use this by default. Using parameter binding consistently is also far more reliable than remembering to manually escape everything.

Putting the breaks on a successful SQL Injection is just as important as preventing it from occuring in the first place. Once an attacker gains the ability to execute SQL queries, they will be doing so as a specific database user. The principle of Least Privilege can be enforced by ensuring that all database users are given only those privileges which are absolutely necessary for them in order to complete their intended tasks.

SQL injection

If a database user has significant privileges, an attacker may be able to drop tables and manipulate the privileges of other users under which the attacker can perform other SQL Injections.

You should never access the database from a web application as the root or any other highly privileged or administrator level user so as to ensure this can never happen. Another variant of the Least Privilege principle is to separate the roles of reading and writing data to a database.

SQL Injection Attack - How to prevent SQL Injection Attacks? - Cybersecurity Training - Edureka

You would have a user with sufficient privileges to perform writes and another separate user restricted to a read-only role. This degree of task separation ensures that if an SQL Injection targets a read-only user, the attacker cannot write or manipulate table data. This form of compartmentalisation can be extended to limit access even further and so minimise the impact of successful SQL Injection attacks.

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Many web applications, particularly open source applications, are specifically designed to use one single database user and that user is almost certainly never checked to see if they are highly privileged or not. Code Injection refers to any means which allows an attacker to inject source code into a web application such that it is interpreted and executed.

This does not apply to code injected into a client of the application, e. The source code can be injected directly from an untrusted input or the web application can be manipulated into loading it from the local filesystem or from an external source such a URL. When a Code Injection occurs as the result of including an external resource it is commonly referred to as a Remote File Inclusion though a RFI attack itself need always be intended to inject code.

The primary causes of Code Injection are Input Validation failures, the inclusion of untrusted input in any context where the input may be evaluated as PHP code, failures to secure source code repositories, failures to exercise caution in downloading third-party libraries, and server misconfigurations which allow non-PHP files to be passed to the PHP interpreter by the web server.

Particular attention should be paid to the final point as it means that all files uploaded to the server by untrusted users can pose a significant risk. If untrusted input is allowed to determine the path parameter passed to these functions it is possible to influence which local file will be included.

It should be noted that the included file need not be an actual PHP file; any included file that is capable of carrying textual data e.

SQL Injection: Defense in Depth

Using the.. Untrusted input used in the replacement string could therefore inject PHP code to be executed.

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Web applications, by definition, will include various files necessary to service any given request. By manipulating the request path or its parameters, it may be possible to provoke the server into including unintended local files by taking advantage of flawed logic in its routing, dependency management, autoloading or other processes.

Such manipulations outside of what the web application was designed to handle can have unforeseen effects. For example, an application might unwittingly expose routes intended only for command line usage. The application may also expose other classes whose constructors perform tasks not a recommended way to design classes but it happens.

Many applications maintain a range of logs which are often displayable to authorised users from a HTML interface.

Sql injection attacks and defense pdf file

As a result, they are a prime target for attackers wishing to disguise other attacks, mislead log reviewers, or even mount a subsequent attack on the users of the monitoring application used to read and analyse the logs. The vulnerability of logs depends on the controls put in place over the writing of logs and ensuring that log data is treated as an untrusted source of data when it comes to performing any monitoring or analysis of the log entries. For example, a programmer might log failed login attempts using a string of the following format:.

If this string, from untrusted input were inserted into the log the attacker would have successfully disguised their failed login attempt as an innocent failure by the Admin user to login.

Adding a successful retry attempt makes the data even less suspicious. Of course, the point here is that an attacker can append all manner of log entries. They can also inject XSS vectors, and even inject characters to mess with the display of the log entries in a console.


Injection may also target log format interpreters. If an analyser tool uses regular expressions to parse a log entry to break it up into data fields, an injected string could be carefully constructed to ensure the regex matches an injected surplus field instead of the correct field.

For example, the following entry might pose a few problems:. More nefarious attacks using Log Injection may attempt to build on a Directory Traversal attack to display a log in a browser. In the right circumstances, injecting PHP code into a log message and calling up the log file in the browser can lead to a successful means of Code Injection which can be carefully formatted and executed at will by the attacker.

Enough said there. The simplest defence against Log Injections is to sanitise any outbound log messages using an allowed characters whitelist.

We could, for example, limit all logs to alphanumeric characters and spaces. Messages detected outside of this character list may be construed as being corrupt leading to a log message concerning a potential LFI to notify you of the potential attempt.

Sql injection attacks and defense pdf file

A secondary defence may be to encode the untrusted input portion into something like base64 which maintains a limited allowed characters profile while still allowing a wide range of information to be stored in text. Path Traversal also Directory Traversal Attacks are attempts to influence backend operations that read from or write to files in the web application by injecting parameters capable of manipulating the file paths employed by the backend operation. This seems completely counterintuitive but it means that the following two function calls using absolute file paths i.

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In a Path Traversal vulnerability, the common factor is that the path to a file is manipulated to instead point at a different file. This is commonly achieved by injecting a series of.. The Dot-Dot-Slash sequence allows an attacker to tell the system to navigate or backtrack up to the parent directory. Of course, path traversals are not just for backtracking.

Sql injection attacks and defense pdf file

An attacker can also inject new path elements to access child directories which may be inaccessible from a browser, e.

XML is so ubiquitous that it can also be found in use on the web application server, in browsers as the format of choice for XMLHttpRequest requests and responses, and in browser extensions. Where the browser is an active participant in an XML exchange, consideration should be given to XML as a request format where authenticated users, via a Cross-Site Scripting attack, may be submitting XML which is actually written by an attacker. XML allows you to expand on the standard entity set by defining custom entities within the XML document itself.

Custom entities can be defined by including them directly in an optional DOCTYPE and the expanded value they represent may reference an external resource to be included.

It is this capacity of ordinary XML to carry custom references which can be expanded with the contents of an external resources that gives rise to an XXE vulnerability. Under normal circumstances, untrusted inputs should never be capable of interacting with our system in unanticipated ways and XXE is almost certainly unexpected for most programmers making it an area of particular concern.

Custom entities obviously have a benefit in representing repetitive text and XML with shorter named entities. However, in keeping with our theme of not trusting outside inputs, we need to be very careful as to what all the XML our application is consuming is really up to.

2nd Edition

For example, this one is definitely not of the harmless variety:. The file retrieved will be interpreted as XML unless it avoids the special characters that trigger that interpretation thus making the scope of local file content disclosure limited.

If the file is intepreted as XML but does not contain valid XML, an error will be the likely result preventing disclosure of the contents. All three of these use the libxml2 extension and external entity support is enabled by default.

Sql injection attacks and defense pdf file

As a consequence, PHP has a by-default vulnerability to XXE which makes it extremely easy to miss when considering the security of a web application or an XML consuming library. We previously met an example of Information Disclosure by noting that a custom entity in XML could reference an external file. Since all such requests are done locally, it allows for disclosing the contents of all files that the application has read access to.

This would allow attackers to examine files that are not publicly available should the expanded entity be included in the output of the application.

Parameterize all Queries

This restriction can, however, be completely ignored in PHP:. The PHP wrapper supports a number of filters which can be run against a given resource so that the results are returned from the function call.

In the above case, we use the convert. What this means is that an attacker, via an XXE vulnerability, can read any accessible file in PHP regardless of its textual format. All the attacker needs to do is base64 decode the output they receive from the application and they can dissect the contents of a wide range of non-public files with impunity. Access Controls can be dictated in any number of ways.

Consider the following primitive access control:.