Templates and predicates
This section provides an introduction to the Snyk Code Query Language standard library of templates and predicates, to give some practical examples of each predicate and template.
Methods, literals, and arguments
A basic capability of Snyk Code is to find method calls and reason about their arguments. The goal here is to discover certain patterns of method calls and their arguments and to check if certain properties hold for these objects.
Consider the following Python program to be analyzed and searched. If a similar program is provided, the same examples will work for any other language Snyk Code supports. The code does not need to be compiled to be queried.
The first query finds the method connect
. The query "connect"
returns both the string with this value and the method call with this name. These can be separated by putting the value in a template. We can use autocompletion to find how the name connect
can be wrapped. Literal
or StringLiteral
will restrict the search results to the string 'connect'
, whereas CallExpression
will restrict the results to the function call connect()
.
Note that you can find function calls to functions outside of the file being scanned. Trying to find CallExpression<"safesend">
will not yield results. The reason is that the analysis may inline local functions in order to reason about their behavior.
Look at the most called method in the file, send
. This method is called on an object returned by connect and takes various strings as input. To see its arguments, you can use some of the templates for its arguments. These are HasArg0
, HasArg1
, and so on.
For example, you can find all calls to send on an object returned by connect
with the following query:
CallExpression<"send"> HasArg0<CallExpression<"connect">>
These are all locations, but we can find the places where we call send with the first argument taking the value connect
.
This gives a different picture. The interprocedural analysis figured out that the message connect was sent in a call to a local function.
Different tasks around the state of the object o
can be explored. Assume we want to find all the calls to send after disconnect. These should be pretty bad cases of the programs where the connection may be in a bad state. To do this query, you can perform the following query:
CallExpression<"send"> HasArg0<DataFlowAfter<Arg0In<CallExpression<"disconnect">>>>
This query searches for calls to send with its argument 0
satisfying the following property: in the dataflow, it is after a location that is an argument 0
in a call to disconnect
. This matches only the final unsafe send
call.
For negation, you can search for objects that are returned by connect
, but not calling disconnect
for the returned object.
CallExpression<"connect"> Not<ForSameObject<Arg0In<CallExpression<"disconnect">>>>
Similarly, you can call send
with connect
but not call disconnect
. The following example has no matches in the preceding code snippet:
CallExpression<"send"> HasArg0<CallExpression<"connect">> Not<HasArg0<ForSameObject<Arg0In<CallExpression<"disconnect">>>>>
In all cases, the auto-completion for the rules should guide the search through the examples to make it easier to write such queries and those that are even more complex.
Taint flows and data sources
In many cases, you want to ensure that certain types of data have no way to flow to certain sensitive locations in the program. This is often done for security reasons, both to ensure compliance and correctness.
The first important element to query is sensitive data sources. Snyk has built in the following set of hierarchical data sources that you can query:
The first category of sources (SourceServer) is defined for programs that implement servers. These sources are typically fully user-controllable. This means that a malicious user can use them to launch an attack against the application or that one needs to handle such data with additional care. For example, you may want to check that authentication is always performed or that some other property is enforced.
The non-server predicates also apply to programs that do not implement server functionality.
Each of the predicates in the SourceServer category is returned by querying PRED:SourceServer
or PRED:AnySource
. Consider the following TypeScript code example:
This implements a request handler for an express server. In this case, the code reads the user cookie and logs it on the console. This might be a security vulnerability and a compliance problem for many applications. The first capability of Snyk Code is that it can discover these cookie locations, and you can connect them to check a lot of properties about them. In this case, running a PRED:SourceCookie
query will find the first line of the request handler.
You can now verify that cookies are handled correctly by the code. For example, you can check that cookies do not end up logged anywhere. You can try to use data flow or ForSameObject.
In this case, report if the cookie is logged as part of some other object, string concatenation, or other simple transformation.
To achieve this, there is a taint analysis done with the taint
predicate. This takes the following shape: Taint< source, sanitizer, sink >
.
Source is the source of sensitive data, sanitizer gives code patterns that would transform the data to be non-sensitive, and sink is the location where the sensitive data should reach a report to be made. The report is then made at the sink location.
Now, consider finding places where the user is logged in. You can then use the following query:
Taint<PRED:SourceCookie, PRED:None, CallExpression<"log">>
Of course, one may want to say that if a cookie is hashed using the function hash123
, then it is safe to be logged. Then, the query would look like:
Taint<PRED:SourceCookie, CallExpression<"hash123">, CallExpression<"log">>
Predefined sinks and sanitizers
Using the preceding taint template, you can start writing vulnerability detectors. However, Snyk Code provides predicates for various types of vulnerabilities. For example, if you want to detect SQL injection, this can be performed fully with the following query:
Taint<PRED:AnySource, PRED:SqliSanitizer, PRED:SqliSink>
Of course, this assumes that any of the sources in AnySource
(see the hierarchy above) is one that a malicious actor may control. For example, not every application is set up in a way that users control environment variables or command line arguments. If you want to find only such SQL injections, you can run a query like:
Taint<Or<PRED:AnySource, PRED:SourceResourceAccess>, PRED:SqliSanitizer, PRED:SqliSink>
In addition to SQL injection, Snyk Code can detect tens of other vulnerabilities and has corresponding predicates accessible from search and custom rules. The number of predicates is growing over time, and more rules are getting open to modifications.
Predefined templates and predicates
Predicates
Any
A "catchall" rule. Matches on anything.
AnySink
Matches on a range of potential data sinks, including server responses, file systems, database writes, external APIs, logging mechanisms, and other forms of data export or display.
AnySource
Matches on various types of potentially user controlled data sources, both servers (e.g., HTTP parameters/header/body, URLs, cookies, etc.) or indirect ones (e.g., database fields, local files, I/O or environment variables).
ApexPageReferenceSource
Matches on potential XSS sources (Language support: Apex).
CleartextCookieStorageSanitizer
Matches on cleartext cookie storage sanitizers (Supported languages: C#).
CleartextCookieStorageSink
Matches on cleartext cookie storage sinks (Supported languages: C#).
CleartextTransmissionSanitizer
Matches on cleartext transmission sanitizers (Supported languages: C#).
CleartextTransmissionSink
Matches on cleartext transmission sinks (Supported languages: C#).
ClientXssSanitizer
Matches on client XSS (e.g., DOMXSS) sanitizers (Supported languages: Javascript).
ClientXssSink
Matches on client XSS (e.g., DOMXSS) sinks (Supported languages: Javascript).
CodeInjectionSanitizer
Matches on code injection sanitizers (Supported languages: C#, Java, JS, Kotlin, PHP, Python, Ruby, Scala, Swift, VB.NET).
CodeInjectionSink
Matches on code injection sinks (Supported languages: C#, Java, JS, Kotlin, PHP, Python, Ruby, Scala, Swift, VB.NET).
CommandInjectionSanitizer
Matches on command injection sanitizers.
CommandInjectionSink
Matches on command injection sinks.
DeserializationSanitizer
Matches on deserialization sanitizers.
DeserializationSink
Matches on deserialization sinks.
EmailContentInjectionSanitizer
Matches on email content injection sanitizers (Language support: Apex, Go).
EmailContentInjectionSink
Matches on email content injection sinks (Language support: Apex, Go).
ErrorMessageOutput
Matches on error message outputs (e.g., stacktraces) (Language support: C#, Go, Java, Javascript, Kotlin, PHP, Scala).
ErrorMessageOutputSanitizer
Matches on error message output sanitizers (Supported languages: C#, Java, Javascript, Kotlin, PHP, Scala).
ErrorMessageOutputSink
Matches on error message output sinks (Supported languages: C#, Go, Java, Javascript, Kotlin, PHP, Scala).
FileInclusionSanitizer
Matches on file inclusion sanitizers (Supported languages: PHP).
FileInclusionSink
Matches on file inclusion sinks (Supported languages: PHP).
InformationDisclosureSanitizer
Matches on information disclosure sanitizers (Supported languages: C#, Go, PHP).
InformationDisclosureSink
Matches on information disclosure sinks (Supported languages: C#, Go, PHP).
IsPaNode
Used to document which language variants are missing an implementation for various stdlib definitions
JndiInjectionSanitizer
Matches on JNDI injection sanitizers (Supported languages: Java, Kotlin, Scala).
JndiInjectionSink
Matches on JNDI injection sinks (Supported languages: Java, Kotlin, Scala).
LdapInjectionSanitizer
Matches on LDAP injection sanitizers (Supported languages: C++, C#, Java, Kotlin, Scala).
LdapInjectionSink
Matches on LDAP injection sinks (Supported languages: C++, C#, Java, Kotlin, Scala).
LogsForgingSanitizer
Matches on log-forging sanitizers (Supported languages: C#).
LogsForgingSink
Matches on log-forging sinks (Supported languages: C#).
MemoryCorruptionSanitizer
Matches on prototype memory corruption sanitizers (Supported languages: Swift).
NoSqliSanitizer
Matches on NoSQL sanitizers (Supported languages: Java, Javascript, Python).
NoSqliSink
Matches on NoSQL sinks (Supported languages: Java, Javascript, Python).
None
An "anti-catchall" rule. Matches on nothing.
OpenRedirectSanitizer
Matches on open-redirect sanitizers (Supported languages: Apex, C#, Go, Java, Javascript, Kotlin, PHP, Python, Scala, VB.NET).
OpenRedirectSink
Matches on open-redirect sinks (Supported languages: Apex, C#, Go, Java, Javascript, Kotlin, PHP, Python, Scala, VB.NET).
PointerOperationSink
Matches on prototype memory operation sinks (Supported languages: Swift).
PotentialXssSink
Matches on potential XSS sinks (Language support: Apex).
PrototypePollutionAssignmentSanitizer
Matches on prototype pollution assignment sanitizers (Supported languages: Javascript).
PrototypePollutionAssignmentSink
Matches on prototype pollution assignment sinks (Supported languages: Javascript).
PtSanitizer
Matches on path-traversal sanitizers.
PtSink
Matches on path-traversal sinks.
RedosSanitizer
Matches on regular-expression denial-of-service sanitizers.
RedosSink
Matches on regular-expression denial-of-service sinks.
ReflectionSanitizer
Matches on reflection sanitizers (Supported languages: Java, Ruby).
ReflectionSink
Matches on reflection sinks (Supported languages: Java, Ruby).
SoqliSanitizer
Matches on soqli sanitizers (Language support: Apex).
SoqliSink
Matches on soqli sinks (Language support: Apex).
SosliSanitizer
Matches on sosli sanitizers (Language support: Apex).
SosliSink
Matches on sosli sinks (Language support: Apex).
SourceArchive
Matches on reading values that are coming from zip, tar or other archives.
SourceCLI
Matches on reading command line arguments.
SourceClientFramework
Matches on reading values that are coming from a client-side framework such as Android, SwiftUI, UIKit, the DOM of an HTML page.
SourceContainsSensitiveData
Matches on reading sensitive data (Language support: C#, Go, PHP).
SourceCookie
Matches on reading values of cookies in an http server. These values are of security interest, because they can be fully controlled by malicious users.
SourceDatabase
Matches on reading values that are coming from a database.
SourceEnvironmentVariable
Matches on reading environment variables of a process.
SourceFile
Matches on reading values that are coming from files.
SourceHttpBody
Matches on reading http request body in an http server. These values are of security interest, because they may be fully controlled by malicious actors.
SourceHttpFileUpload
Matches on the name and content of file uploaded to an http server. These values are of security interest, because they may be fully controlled by malicious actors.
SourceHttpHeader
Matches on reading values of http headers in a server. These values are of security interest, because they may be fully controlled by malicious actors.
SourceHttpParam
Matches on reading values of http parameters in an http server. These values are of security interest, because they may be fully controlled by malicious actors.
SourceLocalEnv
Matches on reading values from the local environment of the running process. This includes command line arguments, standard input or environment variables.
SourceNetworkRequest
Matches on reading values that are coming from a remote resource through network requests.
SourceNonServer
Matches on reading values that may be controlled by an adversary, but not directly by sending requests to a server. E.g. if an application fetches a value from a URL, an adversary in control of that URL may use it to control its content.
SourceRequestUrl
Matches on reading request URLs in a server. The URLs are of security interest, because they may be fully controlled by malicious actors.
SourceResourceAccess
Matches on reading values that may be controlled by an adversary if they gain access to a resource. The resources this matches are remote URLs, files, database fields or other framework-specific cases such as Android intents.
SourceRpcApiParam
Matches on parameters of RPCs implemented in an RPC server. These values are of security interest, because they may be fully controlled by malicious actors.
SourceServer
Matches on reading values that an attacker can send to a server. Examples are HTTP parameters/header/body, URLs or cookies. Since these may be directly controllable by attacker, these sources are of significant security interest.
SourceStdin
Matches on reading input from the standard input of a process.
SourceUnrestrictedArchiveFilePath
Matches on zipslip sources (Language support: C#, Javascript, PHP, Python).
SourceWebForm
Matches on reading values of web forms in a web server. These values are of security interest, because they may be fully controlled by malicious actors.
SqliSanitizer
Matches on SQL injection sanitizers.
SqliSink
Matches on SQL injection sinks.
SsrfSanitizer
Matches on SSRF sanitizers.
SsrfSink
Matches on SSRF sinks.
SstiSanitizer
Matches on SSTI sanitizers (Language support: Javascript, Python, Ruby).
SstiSink
Matches on SSTI sinks (Language support: Javascript, Python, Ruby).
UnsafeSoqliConcatSource
Matches on unsafe sosli/soqli concatenations (Language support: Apex).
UnsafeSosliConcatSource
Matches on unsafe sosli/soqli concatenations (Language support: Apex).
XPathInjectionSanitizer
Matches on XPath injection sanitizers (Supported languages: Apex, C#, VB.NET).
XPathInjectionSink
Matches on XPath injection sinks (Supported languages: Apex, C#, VB.NET).
XamlInjectionSanitizer
Matches on XAML injection sanitizers (Supported languages: C#).
XamlInjectionSink
Matches on XAML injection sinks (Supported languages: C#).
XmlInjectionSanitizer
Matches on XML injection sanitizers (Language support: Apex, C#, VB.NET).
XmlInjectionSink
Matches on XML injection sinks (Language support: Apex, C#, VB.NET).
XssSanitizer
Matches on XSS sanitizers.
XssSink
Matches on XSS sinks.
XxeSanitizer
Matches on XXE sanitizers.
XxeSink
Matches on XXE sinks.
ZipSlipSanitizer
Matches on zipslip sanitizers (Supported languages: C#, Javascript, PHP, Python).
ZipSlipSink
Matches on zipslip sinks (Supported languages: C#, Javascript, PHP, Python).
Templates
And
A binary conjunction. Matches only if both arguments match.
Template parameters:
First - conjunct
Second - conjunct
AnyParamIn
Matches on all parameters of the provided method or function declaration.
Template parameters:
Function
Arg0In
Matches on the 0th index argument (i.e. the receiver object for method calls) for the provided method or function.
Template parameters:
Function
Arg1In
Matches on the 1st index argument for the provided method or function.
Template parameters:
Function
Arg2In
Matches on the 2nd index argument for the provided method or function.
Template parameters:
Function
Arg3In
Matches on the 3rd index argument for the provided method or function.
Template parameters:
Function
Arg4In
Matches on the 4th index argument for the provided method or function.
Template parameters:
Function
Arg5In
Matches on the 5th index argument for the provided method or function.
Template parameters:
Function
Arg6In
Matches on the 6th index argument for the provided method or function.
Template parameters:
Function
Arg7In
Matches on the 7th index argument for the provided method or function.
Template parameters:
Function
BooleanLiteral
Matches on boolean type literals.
Template parameters:
Value
CallExpression
Matches when a given name is called.
Template parameters:
Callee - Function, method or constructor to call.
DataFlowAfter
Matches on entities that happen after in the dataflow of its parameter.
Template parameters:
PrevAction - The previous action executed.
DataFlowsFrom
Matches on places which a taint data can flow from.
Template parameters:
Source
DataFlowsInto
Matches on places which a taint data can flow into.
Template parameters:
Sink
ExplicitSelfParamIn
Matches on the explicit receiver parameter (e.g., self in Python and Rust) for the provided method or function declaration.
Template parameters:
Function
ForSameObject
Matches on entities that happen on the same object as its parameter.
Template parameters:
ObjectAction - The action that happens on the object.
HasAnnotation
Matches on entities annotated by a given annotation.
Template parameters:
Annotation - The annotation with which the entity is annotated.
HasAnnotation
can not be used within Taint
workflows yet.
HasAnyArg
Matches on entities that take any argument with the provided value.
Template parameters:
Value
HasArg0
Matches on entities that take an argument in the 0th index (i.e. receiver object for method calls) with the provided value.
Template parameters:
Value
HasArg1
Matches on entities that take an argument in the 1st index with the provided value.
Template parameters:
Value
HasArg2
Matches on entities that take an argument in the 2nd index with the provided value.
Template parameters:
Value
HasArg3
Matches on entities that take an argument in the 3rd index with the provided value.
Template parameters:
Value
HasArg4
Matches on entities that take an argument in the 4th index with the provided value.
Template parameters:
Value
HasArg5
Matches on entities that take an argument in the 5th index with the provided value.
Template parameters:
Value
HasArg6
Matches on entities that take an argument in the 6th index with the provided value.
Template parameters:
Value
HasArg7
Matches on entities that take an argument in the 7th index with the provided value.
Template parameters:
Value
HasNamedArg
Matches on entities that take a named argument with the provided value.
Template parameters:
Name - The name of the argument.
Value - The value the named argument should have.
Identifier (deprecated)
Matches on an identifier.
Template parameters:
Name - The entity that should be an identifier.
Literal
Matches on string/boolean or number type literals.
Template parameters:
Value
NamedArgIn
Matches on the named argument for the provided method or function.
Template parameters:
Name - The name of the argument.
Function - The provided method or function.
Not
A negation. Matches only if the argument does not match.
Template parameters:
Negated - property
NumberLiteral
Matches on numeric type literals.
Template parameters:
Value
Or
A binary disjunction. Matches if either (or both) arguments match.
Template parameters:
First - disjunct
Second - disjunct
Param1In
Matches on the 1st parameter for the provided method or function declaration.
Template parameters:
Function
Param2In
Matches on the 2nd parameter for the provided method or function declaration.
Template parameters:
Function
Param3In
Matches on the 3rd parameter for the provided method or function declaration.
Template parameters:
Function
Param4In
Matches on the 4th parameter for the provided method or function declaration.
Template parameters:
Function
Param5In
Matches on the 5th parameter for the provided method or function declaration.
Template parameters:
Function
Param6In
Matches on the 6th parameter for the provided method or function declaration.
Template parameters:
Function
Param7In
Matches on the 7th parameter for the provided method or function declaration.
Template parameters:
Function
ReturnedBy
Matches on the returned entity.
Template parameters:
Function - The entity that returns.
Returns
Matches on the entity (e.g. a function or a method) that returns the value provided as argument.
Template parameters:
Value - What is returned.
StringLiteral
Matches on string type literals.
Template parameters:
Value
Taint
Identify data propagation flows that start at the specified source(s) and reach the designated destination sinks (like vulnerable methods) without going through the specified sanitizer(s).
Template parameters:
Source
Sanitizer
Sink
Last updated