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While Data Flow Analysis (DFA) is the computer technique to extract info about values at each program site, Tainting Flow Analysis (TFA) is a special case of DFA between sources/sinks for checking if non-neutralized external inputs may reach vulnerability sinks.
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Tainting Propagation Algorithm: for each sink detected (typically, an argument expression to a call to a sick function), follow backwards the variable value propagation in the CGF (Control Flow Graph) that could affect the sink site, until a source site that “taints” any of the candidate variables is reached.
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Example 2 (Java)
In the next example the neutralization only affects to filesystem resources:
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language | xml |
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language | java |
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Reference
Structure of Custom Neutralization File (CNF)
Info |
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Any CNF must be an XML file with the following structure:
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Next sections describe this structure.
Reference to master DTD file
Reference to master DTD must be specified in the 1st line.
Next table shows specific content depending on the technology:
Tech | DTD specification | DTD location |
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abap | <!DOCTYPE library SYSTEM "abap_library.dtd"> | [agent_home_dir]/libraries/abap |
c / cpp | <!DOCTYPE library SYSTEM "cpp_library.dtd"> | [agent_home_dir]/libraries/c |
csharp | <!DOCTYPE library SYSTEM "library_metadata.dtd"> |
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java | <!DOCTYPE library SYSTEM "library_metadata.dtd"> |
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javascript | <!DOCTYPE library SYSTEM "js_library_metadata.dtd"> | [agent_home_dir]/libraries/javascript |
objectivec | <!DOCTYPE library SYSTEM "library_metadata.dtd"> |
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php | <!DOCTYPE library SYSTEM "php_library.dtd"> | [agent_home_dir]/libraries/php |
python | <!DOCTYPE library SYSTEM "python_library_metadata.dtd"> | [agent_home_dir]/libraries/python |
Neutralization elements
A neutralization is defined in Kiuwan by the following element:
Code Block | ||
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<!ELEMENT neutralization (#PCDATA)*>
<!ATTLIST neutralization
argpos CDATA #REQUIRED
kind CDATA #IMPLIED
resource %resource; #IMPLIED
> |
argpos
Info | ||
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argpos attribute specifies the “tainted” object, i.e. what object (or objects) are “untainted” by the routine. |
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value = obj.call( arg1, arg2)
The neutralization routine can “untaint” one or many of those objects.
argpos attribute specifies which ones, as follows:
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title | kind |
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In case you want the neutralization applies to ALL the vulnerabilities (i.e. it’s not specific to any vulnerability), set “string” as the value for “kind” attribute
resource
A neutralization routine also can be specifically suited to a particular resource type.
For example, your neutralization routine could be applied to “database” or “filesystem” resource types.
Valid values of resource can be one of (memory |os |configuration |environment |filesystem |formatstr |database |web |network |gui |crypto |other).
As above, check the Sink Data to set the appropriate value. That’s the value you must indicate in “kind” attribute.
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