Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection')ID: 89 | Date: (C)2012-05-14 (M)2022-10-10 | Type: weakness | Status: DRAFT | Abstraction Type: Base |
Description The software constructs all or part of an SQL command using
externally-influenced input from an upstream component, but it does not
neutralize or incorrectly neutralizes special elements that could modify the
intended SQL command when it is sent to a downstream
component. Extended DescriptionWithout sufficient removal or quoting of SQL syntax in user-controllable
inputs, the generated SQL query can cause those inputs to be interpreted as
SQL instead of ordinary user data. This can be used to alter query logic to
bypass security checks, or to insert additional statements that modify the
back-end database, possibly including execution of system commands.SQL injection has become a common issue with database-driven web sites.
The flaw is easily detected, and easily exploited, and as such, any site or
software package with even a minimal user base is likely to be subject to an
attempted attack of this kind. This flaw depends on the fact that SQL makes
no real distinction between the control and data planes. Enabling Factors for ExploitationThe application dynamically generates queries that contain user
input. Likelihood of Exploit: Very High Applicable PlatformsLanguage Class: AllTechnology Class: Database-Server Time Of Introduction - Architecture and Design
- Implementation
- Operation
Related Attack Patterns Common Consequences Scope | Technical Impact | Notes |
---|
Confidentiality | Read application
data | Since SQL databases generally hold sensitive data, loss of
confidentiality is a frequent problem with SQL injection
vulnerabilities. | Access_Control | Bypass protection
mechanism | If poor SQL commands are used to check user names and passwords, it
may be possible to connect to a system as another user with no previous
knowledge of the password. | Access_Control | Bypass protection
mechanism | If authorization information is held in a SQL database, it may be
possible to change this information through the successful exploitation
of a SQL injection vulnerability. | Integrity | Modify application
data | Just as it may be possible to read sensitive information, it is also
possible to make changes or even delete this information with a SQL
injection attack. |
Detection Methods Name | Description | Effectiveness | Notes |
---|
Automated Static Analysis | This weakness can often be detected using automated static analysis
tools. Many modern tools use data flow analysis or constraint-based
techniques to minimize the number of false positives.Automated static analysis might not be able to recognize when proper
input validation is being performed, leading to false positives - i.e.,
warnings that do not have any security consequences or do not require
any code changes.Automated static analysis might not be able to detect the usage of
custom API functions or third-party libraries that indirectly invoke SQL
commands, leading to false negatives - especially if the API/library
code is not available for analysis. | | | Automated Dynamic Analysis | This weakness can be detected using dynamic tools and techniques that
interact with the software using large test suites with many diverse
inputs, such as fuzz testing (fuzzing), robustness testing, and fault
injection. The software's operation may slow down, but it should not
become unstable, crash, or generate incorrect results. | Moderate | | Manual Analysis | Manual analysis can be useful for finding this weakness, but it might
not achieve desired code coverage within limited time constraints. This
becomes difficult for weaknesses that must be considered for all inputs,
since the attack surface can be too large. | | |
Potential Mitigations Phase | Strategy | Description | Effectiveness | Notes |
---|
Architecture and Design | Libraries or Frameworks | Use a vetted library or framework that does not allow this weakness to
occur or provides constructs that make this weakness easier to
avoid.For example, consider using persistence layers such as Hibernate or
Enterprise Java Beans, which can provide significant protection against
SQL injection if used properly. | | | Architecture and Design | Parameterization | If available, use structured mechanisms that automatically enforce the
separation between data and code. These mechanisms may be able to
provide the relevant quoting, encoding, and validation automatically,
instead of relying on the developer to provide this capability at every
point where output is generated.Process SQL queries using prepared statements, parameterized queries,
or stored procedures. These features should accept parameters or
variables and support strong typing. Do not dynamically construct and
execute query strings within these features using "exec" or similar
functionality, since this may re-introduce the possibility of SQL
injection. [R.89.3] | | | Architecture and DesignOperation | Environment Hardening | Run your code using the lowest privileges that are required to
accomplish the necessary tasks [R.89.12]. If possible, create isolated
accounts with limited privileges that are only used for a single task.
That way, a successful attack will not immediately give the attacker
access to the rest of the software or its environment. For example,
database applications rarely need to run as the database administrator,
especially in day-to-day operations.Specifically, follow the principle of least privilege when creating
user accounts to a SQL database. The database users should only have the
minimum privileges necessary to use their account. If the requirements
of the system indicate that a user can read and modify their own data,
then limit their privileges so they cannot read/write others' data. Use
the strictest permissions possible on all database objects, such as
execute-only for stored procedures. | | | Architecture and Design | | For any security checks that are performed on the client side, ensure
that these checks are duplicated on the server side, in order to avoid
CWE-602. Attackers can bypass the client-side checks by modifying values
after the checks have been performed, or by changing the client to
remove the client-side checks entirely. Then, these modified values
would be submitted to the server. | | | Implementation | Output Encoding | While it is risky to use dynamically-generated query strings, code, or
commands that mix control and data together, sometimes it may be
unavoidable. Properly quote arguments and escape any special characters
within those arguments. The most conservative approach is to escape or
filter all characters that do not pass an extremely strict whitelist
(such as everything that is not alphanumeric or white space). If some
special characters are still needed, such as white space, wrap each
argument in quotes after the escaping/filtering step. Be careful of
argument injection (CWE-88).Instead of building a new implementation, such features may be
available in the database or programming language. For example, the
Oracle DBMS_ASSERT package can check or enforce that parameters have
certain properties that make them less vulnerable to SQL injection. For
MySQL, the mysql_real_escape_string() API function is available in both
C and PHP. | | | Implementation | Input Validation | Assume all input is malicious. Use an "accept known good" input
validation strategy, i.e., use a whitelist of acceptable inputs that
strictly conform to specifications. Reject any input that does not
strictly conform to specifications, or transform it into something that
does.When performing input validation, consider all potentially relevant
properties, including length, type of input, the full range of
acceptable values, missing or extra inputs, syntax, consistency across
related fields, and conformance to business rules. As an example of
business rule logic, "boat" may be syntactically valid because it only
contains alphanumeric characters, but it is not valid if the input is
only expected to contain colors such as "red" or "blue."Do not rely exclusively on looking for malicious or malformed inputs
(i.e., do not rely on a blacklist). A blacklist is likely to miss at
least one undesirable input, especially if the code's environment
changes. This can give attackers enough room to bypass the intended
validation. However, blacklists can be useful for detecting potential
attacks or determining which inputs are so malformed that they should be
rejected outright.When constructing SQL query strings, use stringent whitelists that
limit the character set based on the expected value of the parameter in
the request. This will indirectly limit the scope of an attack, but this
technique is less important than proper output encoding and
escaping.Note that proper output encoding, escaping, and quoting is the most
effective solution for preventing SQL injection, although input
validation may provide some defense-in-depth. This is because it
effectively limits what will appear in output. Input validation will not
always prevent SQL injection, especially if you are required to support
free-form text fields that could contain arbitrary characters. For
example, the name "O'Reilly" would likely pass the validation step,
since it is a common last name in the English language. However, it
cannot be directly inserted into the database because it contains the
"'" apostrophe character, which would need to be escaped or otherwise
handled. In this case, stripping the apostrophe might reduce the risk of
SQL injection, but it would produce incorrect behavior because the wrong
name would be recorded.When feasible, it may be safest to disallow meta-characters entirely,
instead of escaping them. This will provide some defense in depth. After
the data is entered into the database, later processes may neglect to
escape meta-characters before use, and you may not have control over
those processes. | | | Architecture and Design | Enforcement by Conversion | When the set of acceptable objects, such as filenames or URLs, is
limited or known, create a mapping from a set of fixed input values
(such as numeric IDs) to the actual filenames or URLs, and reject all
other inputs. | | | Implementation | | Ensure that error messages only contain minimal details that are
useful to the intended audience, and nobody else. The messages need to
strike the balance between being too cryptic and not being cryptic
enough. They should not necessarily reveal the methods that were used to
determine the error. Such detailed information can be used to refine the
original attack to increase the chances of success.If errors must be tracked in some detail, capture them in log messages
- but consider what could occur if the log messages can be viewed by
attackers. Avoid recording highly sensitive information such as
passwords in any form. Avoid inconsistent messaging that might
accidentally tip off an attacker about internal state, such as whether a
username is valid or not.In the context of SQL Injection, error messages revealing the
structure of a SQL query can help attackers tailor successful attack
strings. | | | Operation | Firewall | Use an application firewall that can detect attacks against this
weakness. It can be beneficial in cases in which the code cannot be
fixed (because it is controlled by a third party), as an emergency
prevention measure while more comprehensive software assurance measures
are applied, or to provide defense in depth. | Moderate | An application firewall might not cover all possible input vectors. In
addition, attack techniques might be available to bypass the protection
mechanism, such as using malformed inputs that can still be processed by
the component that receives those inputs. Depending on functionality, an
application firewall might inadvertently reject or modify legitimate
requests. Finally, some manual effort may be required for
customization. | OperationImplementation | Environment Hardening | When using PHP, configure the application so that it does not use
register_globals. During implementation, develop the application so that
it does not rely on this feature, but be wary of implementing a
register_globals emulation that is subject to weaknesses such as CWE-95,
CWE-621, and similar issues. | | |
RelationshipsSQL injection can be resultant from special character mismanagement, MAID,
or blacklist/whitelist problems. It can be primary to authentication
errors. Related CWE | Type | View | Chain |
---|
CWE-89 ChildOf CWE-896 | Category | CWE-888 | |
Demonstrative Examples (Details) - In 2008, a large number of web servers were compromised using the
same SQL injection attack string. This single string worked against many
different programs. The SQL injection was then used to modify the web sites
to serve malicious code. [1]
- MS SQL has a built in function that enables shell command execution.
An SQL injection in such a context could be disastrous. For example, a query
of the form:
- The following code dynamically constructs and executes a SQL query
that searches for items matching a specified name. The query restricts the
items displayed to those where owner matches the user name of the
currently-authenticated user.
- This code intends to print a message summary given the message
ID.
- This example attempts to take a last name provided by a user and
enter it into a database.
- This example examines the effects of a different malicious value
passed to the query constructed and executed in the previous
example.
Observed Examples - CVE-2004-0366 : chain: SQL injection in library intended for database authentication allows SQL injection and authentication bypass.
- CVE-2008-2790 : SQL injection through an ID that was supposed to be numeric.
- CVE-2008-2223 : SQL injection through an ID that was supposed to be numeric.
- CVE-2007-6602 : SQL injection via user name.
- CVE-2008-5817 : SQL injection via user name or password fields.
- CVE-2003-0377 : SQL injection in security product, using a crafted group name.
- CVE-2008-2380 : SQL injection in authentication library.
For more examples, refer to CVE relations in the bottom box. White Box DefinitionsA weakness where the code path has:1. start statement that accepts input and2. end statement that performs an SQL command wherea. the input is part of the SQL command andb. input contains SQL syntax (esp. query separator) Black Box Definitions None Taxynomy Mappings Taxynomy | Id | Name | Fit |
---|
PLOVER | | SQL injection | | 7 Pernicious Kingdoms | | SQL Injection | | CLASP | | SQL injection | | OWASP Top Ten 2007 | A2 | Injection Flaws | CWE_More_Specific | OWASP Top Ten 2004 | A1 | Unvalidated Input | CWE_More_Specific | OWASP Top Ten 2004 | A6 | Injection Flaws | CWE_More_Specific | WASC | 19 | SQL Injection | |
References: - Michael Howard David LeBlanc John Viega .24 Deadly Sins of Software Security. McGraw-Hill. Section:'"Sin 1: SQL Injection." Page 3'. Published on 2010.
- M. Howard D. LeBlanc .Writing Secure Code 2nd Edition. Microsoft. Section:'Chapter 12, "Database Input Issues" Page
397'. Published on 2002.
- OWASP .SQL Injection Prevention Cheat Sheet.
- Steven Friedl .SQL Injection Attacks by Example. 2007-10-10.
- Ferruh Mavituna .SQL Injection Cheat Sheet. 2007-03-15.
- David Litchfield Chris Anley John Heasman Bill Grindlay .The Database Hacker's Handbook: Defending Database
Servers. Wiley. 2005-07-14.
- David Litchfield .The Oracle Hacker's Handbook: Hacking and Defending
Oracle. Wiley. 2007-01-30.
- Microsoft .SQL Injection. Published on December 2008.
- Microsoft Security Vulnerability Research &
Defense .SQL Injection Attack.
- Michael Howard .Giving SQL Injection the Respect it Deserves. 2008-05-15.
- Frank Kim .Top 25 Series - Rank 2 - SQL Injection. SANS Software Security Institute. 2010-03-01.
- Sean Barnum Michael Gegick .Least Privilege. Published on 2005-09-14.
- Mark Dowd John McDonald Justin Schuh .The Art of Software Security Assessment 1st Edition. Addison Wesley. Section:'Chapter 8, "SQL Queries", Page 431.'. Published on 2006.
- Mark Dowd John McDonald Justin Schuh .The Art of Software Security Assessment 1st Edition. Addison Wesley. Section:'Chapter 17, "SQL Injection", Page 1061.'. Published on 2006.
|