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This section will explain in detail how you can undestand a vulnerabilty as reported by Kiuwan.
|Table of Contents|
The explanation is focused on injection-related vulnerabilities, as an example of complex vulnerabilities.
To do it,firstly we will provide an
We will first provide an overview of Tainted Flow Analysis (the theoretical basis behind the scenes),and
and then we will focuson
on Kiuwan vulnerability reporting.
Tainted Flow Analysis
Root The root cause of many security breaches is is trusting unvalidated input:. This could be:
- Input from the user is considered as tainted , which could be considered as tainted (possibly controlled controlled by an adversary), i.e user is considered as a an untrusted source source
- Data is used, assuming it is is untainted (must not be controlled controlled by an adversary), i.e. sensitive data sinks rely on trusted (untainted) data
locations are those code places from where data comes in, that can be potentially controlled by the user (or the environment) and must consequently be presumably considered as tainted (it may be used to build injection attacks).
locations are those code places where consumed data must not be tainted.
of Tainted Flow Analysisis
is to detect tainted data flows:For
Prove, for all possible sinks,prove
that tainted data will never be used where untainted data is expected.
Kiuwan implements Tainted Flow Analysis by inferring flows in the source code of your application:
When inferring flows from an untainted sink to a tainted source, Kiuwan is able to can detect if any well-known known sanitizer is is used, dropping those flows and thus avoiding to raise false vulnerabilities.
Kiuwan contains a built-in library of sanitizers for every supported programming language and framework.
These sanitizers are commonly used directly by programmers or by frameworks. And Kiuwan detects the their use of them.
How to understand tainted-flow vulnerabilities
Vulnerabilities are reportedat
under Code Security–
All the vulnerabilities of the same type (i.e. coming from the same Kiuwan rule that checks for it) are grouped under the Kiuwan rule name, indicating how many files are “affected” affected and how many vulnerabilities were found.
Finding Vulnerabilities(e.g. SQL Injection)
For our explanation, we will follow an example based on Waratek – Spiracle software, focused focusing on SQL -Injection injection vulnerabilities.
Below image shows SQl-Injection vulnerabilities. Just use the "Search for the SQL injection vulnerabilities by entering "SQL" in the Search by rule name" filter field..
We In this image, we can see in the image that there are 2 files affected, i.e. two files where there’s are affected: there is a sink that is being feed by fed tainted data, i. e. an An injection point.Also, we can see that for
For every file there are a number of vulnerabilities.
What do those vulnerabilities mean? See next image.
Graphical view ofall Sources and Sinks related with a Vulnerability
For every vulnerability, you could see next icon
Clicking on that icon will open a graphical view of the complete set of sources, sinks and tainted flows of the selected vulnerability (rule) of your application.
sources and sinks
Every vulnerability offers the possibility to view a graph view of all the propagation paths for this item.
Click the Image Added icon on the right:
The following graph will open:
Tainted data flows are represented as directed graphs from sources (at the top) to sinks (at the bottom).
Any element may have a number that indicates in which how many tainted data flows it participates.
You can see the detail of any element (source, sink or propagation node) by hovering the mouse overt it. A dialog information will be displayed as in the image below.:
Clicking on the affected file will open all its affected sinks.
In this case, there’s only one sink for every file (only one injection point), but it could be many… many. Kiuwan will display all the line numbers of the affected sinks.
If you want to see a grahical graphical view of all the sources, sinks and tainted data flows for a file you can also click on the icon.
And the following graph will be displayed.:
Clicking on a sink will display its details as well as all the sources where data is collectedform
from an untrusted source and flows to the sink without being neutralized (or sanitized).
Sink's detailed information
Detailed information of a sink
Sink detail includes The sink details include the following information:
Most commonly, every source will be a different file. But depending on the flow path, you could find same source and line many times.
Let’s see how to understand every source.
Source's detailed information
Clicking on a source will open a frame with its detailed information about the source.
Source detail includes following information:
Important: You You should not understand the propagation path as a typical stack of method calls. It’s not that.
You should understand it as a data-flow path.
Let’s see with look at the following example.:
You can also view it in grahical graphical mode:
Any propagation path is composed of a source node, a sink node and as many propagation nodes as different methods are involved in the propagation path.
In the example, we can see the next propagation path (flowing from source to sink):
- Source The source node indicates that the file ParameterNullFix.java line 32 (within sanitizeNull method) gets the value from a request parameter.
- This is marked a source because HttpServletRequest.getParameter(..) is considered as an untrusted input source (i.e. is directly manipulated by the user) and no neutralization routine has been found.
- First The first propagation node indicates that Delete_User.java line 68 receives back the above tainted data.
- Second The second propagation node indicates that Delete_User.java line 75 sends the tainted data (via method parameter) to another object through UpdateUtil.executeUpdate(…) method call.
- Looking at the source code, you could see that the tainted data is directly appended to a sql string without any neutralization, allowing this way to directly insert user code into the sql sentence.
- Sink The sink node indicates that the file UpdateUtil.java line 61 (within executeUpdate(…) method) injects tainted data (sql sentence) to a PreparedStatement that finally is executed against the database.
Once explained a concrete source-sink propagation path, let’s Let’s go back to the initial sink information.
As said above, for every sink there will appear the list of sources that are “feeding” that sink.
But you might be wondering why are there 5 are 5 sources with the same file name and line.
We’ve selected this specific example because it shows to show something that would be possible to could happen in your own code. Let’s go in detail exploring the 2nd sourceexplore the second source into detail.
In the 2nd source you can see that the propagation nodes are different from the previous one.
While in the 1st the propagation it was through Delete_User.java, in the 2nd, it goes through a different file: Insert_Raw_Text.java.
Remainder Reminder sources for the same sink shows show that there are still other different propagation paths between the same source and the sink.
This example is a special case where the call sequence consists of 5 servlets calling a utility (ParameterNullFix.sanitizeNull(..)) to recover some request parameters, building a an SQL sentence with those this tainted data and sending the sql SQL sentence to another utility (UpdateUtil.executeUpdate(…) ) to execute the database update.
This is the reason Kiuwan shows one sink with 5 different sinks. That difference is because the propagation paths are through the different servlets. In In this case, the easiest fix would be to sanitize the user data at the source, therefore remediating 5 found defects with only one fix.
As a summary, you can understand any injection vulnerability as a unique propagation path from source to sink, regardless of whether source and sink be are the same.
A vulnerability's data path information is complementary to its propagation path. Although they may similar, the data path adds detailed information on how the data flows through your code making it vulnerable.
Let us inspect the data path corresponding to the example shown in the Propagation path section:
A data path is composed of a series of steps that show how tainted data flows through the source code.
The data path shown in the example consists of (from source to sink):
- The container step shows the method where the user input is first detected in the analyzed source code. In this case, the request parameter contains user input data.
- The source step reports how the new val variable is initialized retrieving data from the request parameter, so Kiuwan considers it a tainted variable.
- In the next step the val variable is assigned to another object. In this case, the outputMap object is tainted because it contains input data that has not been sanitized.
- This map is then returned to the calling method, that is reported in the next step and belongs to a different file (Delete_user.java).
- The next step shows how the returned map is then inspected to get a key that has been tainted.
- The name variable is tainted and is injected into a query in the next step.
- The created sql string object is then sent to a method located in UpdateUtil.java.
- Once inside the method (which has been identified as the sink of the vulnerability), the tainted variable sql is used to construct the prepared statement that will be executed (and it contains data in which a user could have injected mailicious code).
Some injection rules provide the ability to behave differently depending on a configuration a configuration parameter: parametersAsSources
This parameter makes the rule to consider the function/method parameters where the sink is contained as "sources". And sources are always being considered as "tainted".
If parametersAsSources=true, the rule performs a tainting path analysis to check if the parameters are neutralized since being received by the function/method until are consumed by the sink. If no neutralization is found, an injection vulnerability is raised. By default, parametersAsSources=false.
Why should you change it to true ?
If your software being analyzed by Kiuwan is a complete application (i.e. it contains presentation plus logic and ddbb layers), you should let it be as false. This In this way, Kiuwan will make a full tanting path analysis over the whole application code.
But, if your software is a "library", i.e. a software component that will be used by 3rd parties to build their own applications, you should configure this property to true, making Kiuwan to perform that local tainting path analysis, thus guaranteeing that your library is protected against injection vulnerabilities regardless the usage by third parties.
As you can guess, setting to true and analyzing a complete application will result in a number of false positives.