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Merge pull request #3111 from RasmusWL/python-fabric-command-injection
Approved by BekaValentine
2 parents ae076da + 49fa7c8 commit ac7c74d

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‎change-notes/1.24/analysis-python.md‎

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@@ -15,6 +15,7 @@ Support for Django version 2.x and 3.x
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| **Query** | **Expected impact** | **Change** |
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|----------------------------|------------------------|------------------------------------------------------------------|
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| Uncontrolled command line (`py/command-line-injection`) | More results | We now model the `fabric` and `invoke` pacakges for command execution. |
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### Web framework support
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‎python/ql/src/Security/CWE-078/CommandInjection.ql‎

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@@ -29,8 +29,7 @@ class CommandInjectionConfiguration extends TaintTracking::Configuration {
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}
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override predicate isSink(TaintTracking::Sink sink) {
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sink instanceof OsCommandFirstArgument or
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sink instanceof ShellCommand
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sink instanceof CommandSink
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}
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override predicate isExtension(TaintTracking::Extension extension) {

‎python/ql/src/semmle/python/security/injection/Command.qll‎

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@@ -1,26 +1,27 @@
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/** Provides class and predicates to track external data that
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/**
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* Provides class and predicates to track external data that
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* may represent malicious OS commands.
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*
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* This module is intended to be imported into a taint-tracking query
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* to extend `TaintKind` and `TaintSink`.
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*
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*/
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import python
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import python
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import semmle.python.security.TaintTracking
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import semmle.python.security.strings.Untrusted
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/** Abstract taint sink that is potentially vulnerable to malicious shell commands. */
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abstract class CommandSink extends TaintSink { }
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private ModuleObject osOrPopenModule() {
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result.getName() = "os" or
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result.getName() = "popen2"
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}
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private Object makeOsCall() {
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exists(string name |
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result = ModuleObject::named("subprocess").attr(name) |
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exists(string name | result = ModuleObject::named("subprocess").attr(name) |
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name = "Popen" or
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name = "call" or
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name = "call" or
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name = "check_call" or
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name = "check_output" or
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name = "run"
@@ -29,40 +30,27 @@ private Object makeOsCall() {
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/**Special case for first element in sequence. */
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class FirstElementKind extends TaintKind {
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FirstElementKind() { this = "sequence[" + any(ExternalStringKind key) + "][0]" }
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FirstElementKind() {
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this = "sequence[" + any(ExternalStringKind key) + "][0]"
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}
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override string repr() {
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result = "first item in sequence of " + this.getItem().repr()
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}
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override string repr() { result = "first item in sequence of " + this.getItem().repr() }
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/** Gets the taint kind for item in this sequence. */
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ExternalStringKind getItem() {
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this = "sequence[" + result + "][0]"
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}
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ExternalStringKind getItem() { this = "sequence[" + result + "][0]" }
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}
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class FirstElementFlow extends DataFlowExtension::DataFlowNode {
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FirstElementFlow() { this = any(SequenceNode s).getElement(0) }
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FirstElementFlow() {
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this = any(SequenceNode s).getElement(0)
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}
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override
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ControlFlowNode getASuccessorNode(TaintKind fromkind, TaintKind tokind) {
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override ControlFlowNode getASuccessorNode(TaintKind fromkind, TaintKind tokind) {
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result.(SequenceNode).getElement(0) = this and tokind.(FirstElementKind).getItem() = fromkind
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}
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}
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/** A taint sink that is potentially vulnerable to malicious shell commands.
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/**
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* A taint sink that is potentially vulnerable to malicious shell commands.
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* The `vuln` in `subprocess.call(shell=vuln)` and similar calls.
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*/
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class ShellCommand extends TaintSink {
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class ShellCommand extends CommandSink {
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override string toString() { result = "shell command" }
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ShellCommand() {
@@ -75,7 +63,8 @@ class ShellCommand extends TaintSink {
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or
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exists(CallNode call, string name |
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call.getAnArg() = this and
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call.getFunction().refersTo(osOrPopenModule().attr(name)) |
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call.getFunction().refersTo(osOrPopenModule().attr(name))
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|
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name = "system" or
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name = "popen" or
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name.matches("popen_")
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/* List (or tuple) containing a tainted string command */
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kind instanceof ExternalStringSequenceKind
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}
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}
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/** A taint sink that is potentially vulnerable to malicious shell commands.
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/**
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* A taint sink that is potentially vulnerable to malicious shell commands.
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* The `vuln` in `subprocess.call(vuln, ...)` and similar calls.
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*/
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class OsCommandFirstArgument extends TaintSink {
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class OsCommandFirstArgument extends CommandSink {
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override string toString() { result = "OS command first argument" }
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OsCommandFirstArgument() {
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not this instanceof ShellCommand and
109-
exists(CallNode call|
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exists(CallNode call |
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call.getFunction().refersTo(makeOsCall()) and
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call.getArg(0) = this
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)
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/* List (or tuple) whose first element is tainted */
120108
kind instanceof FirstElementKind
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}
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}
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// -------------------------------------------------------------------------- //
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// Modeling of the 'invoke' package and 'fabric' package (v 2.x)
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//
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// Since fabric build so closely upon invoke, we model them together to avoid
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// duplication
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// -------------------------------------------------------------------------- //
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/**
119+
* A taint sink that is potentially vulnerable to malicious shell commands.
120+
* The `vuln` in `invoke.run(vuln, ...)` and similar calls.
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*/
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class InvokeRun extends CommandSink {
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InvokeRun() {
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this = Value::named("invoke.run").(FunctionValue).getArgumentForCall(_, 0)
125+
or
126+
this = Value::named("invoke.sudo").(FunctionValue).getArgumentForCall(_, 0)
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}
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override string toString() { result = "InvokeRun" }
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131+
override predicate sinks(TaintKind kind) { kind instanceof ExternalStringKind }
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}
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/**
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* Internal TaintKind to track the invoke.Context instance passed to functions
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* marked with @invoke.task
137+
*/
138+
private class InvokeContextArg extends TaintKind {
139+
InvokeContextArg() { this = "InvokeContextArg" }
140+
}
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/** Internal TaintSource to track the context passed to functions marked with @invoke.task */
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private class InvokeContextArgSource extends TaintSource {
144+
InvokeContextArgSource() {
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exists(Function f, Expr decorator |
146+
count(f.getADecorator()) = 1 and
147+
(
148+
decorator = f.getADecorator() and not decorator instanceof Call
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or
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decorator = f.getADecorator().(Call).getFunc()
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) and
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(
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decorator.pointsTo(Value::named("invoke.task"))
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or
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decorator.pointsTo(Value::named("fabric.task"))
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)
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|
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this.(ControlFlowNode).getNode() = f.getArg(0)
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)
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}
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override predicate isSourceOf(TaintKind kind) { kind instanceof InvokeContextArg }
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}
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/**
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* A taint sink that is potentially vulnerable to malicious shell commands.
167+
* The `vuln` in `invoke.Context().run(vuln, ...)` and similar calls.
168+
*/
169+
class InvokeContextRun extends CommandSink {
170+
InvokeContextRun() {
171+
exists(CallNode call |
172+
any(InvokeContextArg k).taints(call.getFunction().(AttrNode).getObject("run"))
173+
or
174+
call = Value::named("invoke.Context").(ClassValue).lookup("run").getACall()
175+
or
176+
// fabric.connection.Connection is a subtype of invoke.context.Context
177+
// since fabric.Connection.run has a decorator, it doesn't work with FunctionValue :|
178+
// and `Value::named("fabric.Connection").(ClassValue).lookup("run").getACall()` returned no results,
179+
// so here is the hacky solution that works :\
180+
call.getFunction().(AttrNode).getObject("run").pointsTo().getClass() =
181+
Value::named("fabric.Connection")
182+
|
183+
this = call.getArg(0)
184+
or
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this = call.getArgByName("command")
186+
)
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}
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189+
override string toString() { result = "InvokeContextRun" }
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191+
override predicate sinks(TaintKind kind) { kind instanceof ExternalStringKind }
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}
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194+
/**
195+
* A taint sink that is potentially vulnerable to malicious shell commands.
196+
* The `vuln` in `fabric.Group().run(vuln, ...)` and similar calls.
197+
*/
198+
class FabricGroupRun extends CommandSink {
199+
FabricGroupRun() {
200+
exists(ClassValue cls |
201+
cls.getASuperType() = Value::named("fabric.Group") and
202+
this = cls.lookup("run").(FunctionValue).getArgumentForCall(_, 1)
203+
)
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}
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206+
override string toString() { result = "FabricGroupRun" }
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208+
override predicate sinks(TaintKind kind) { kind instanceof ExternalStringKind }
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}
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211+
// -------------------------------------------------------------------------- //
212+
// Modeling of the 'invoke' package and 'fabric' package (v 1.x)
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// -------------------------------------------------------------------------- //
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class FabricV1Commands extends CommandSink {
215+
FabricV1Commands() {
216+
// since `run` and `sudo` are decorated, we can't use FunctionValue's :(
217+
exists(CallNode call |
218+
call = Value::named("fabric.api.local").getACall()
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or
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call = Value::named("fabric.api.run").getACall()
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or
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call = Value::named("fabric.api.sudo").getACall()
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|
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this = call.getArg(0)
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or
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this = call.getArgByName("command")
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)
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}
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230+
override string toString() { result = "FabricV1Commands" }
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override predicate sinks(TaintKind kind) { kind instanceof ExternalStringKind }
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}

‎python/ql/test/library-tests/security/command-execution/CommandSinks.expected‎

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| fabric_v1_test.py:8:7:8:28 | FabricV1Commands | externally controlled string |
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| fabric_v1_test.py:9:5:9:27 | FabricV1Commands | externally controlled string |
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| fabric_v1_test.py:10:6:10:38 | FabricV1Commands | externally controlled string |
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| fabric_v2_test.py:10:16:10:25 | InvokeContextRun | externally controlled string |
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| fabric_v2_test.py:12:15:12:36 | InvokeContextRun | externally controlled string |
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| fabric_v2_test.py:16:45:16:54 | FabricGroupRun | externally controlled string |
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| fabric_v2_test.py:21:10:21:13 | FabricGroupRun | externally controlled string |
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| fabric_v2_test.py:31:14:31:41 | InvokeContextRun | externally controlled string |
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| fabric_v2_test.py:33:15:33:64 | InvokeContextRun | externally controlled string |
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| invoke_test.py:8:12:8:21 | InvokeRun | externally controlled string |
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| invoke_test.py:9:20:9:40 | InvokeRun | externally controlled string |
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| invoke_test.py:12:17:12:24 | InvokeRun | externally controlled string |
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| invoke_test.py:13:25:13:32 | InvokeRun | externally controlled string |
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| invoke_test.py:17:11:17:40 | InvokeContextRun | externally controlled string |
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| invoke_test.py:21:11:21:32 | InvokeContextRun | externally controlled string |
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| invoke_test.py:27:11:27:25 | InvokeContextRun | externally controlled string |
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| invoke_test.py:32:11:32:25 | InvokeContextRun | externally controlled string |

‎python/ql/test/library-tests/security/command-execution/CommandSinks.ql‎

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import python
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import semmle.python.security.injection.Command
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import semmle.python.security.strings.Untrusted
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5+
from CommandSink sink, TaintKind kind
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where sink.sinks(kind)
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select sink, kind

‎python/ql/test/library-tests/security/command-execution/fabric-LICENSE‎

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Copyright (c) 2020 Jeff Forcier.
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
19+
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
21+
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

‎python/ql/test/library-tests/security/command-execution/fabric_v1_test.py‎

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"""tests for the 'fabric' package (v1.x)
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See http://docs.fabfile.org/en/1.14/tutorial.html
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"""
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from fabric.api import run, local, sudo
7+
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local('echo local execution')
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run('echo remote execution')
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sudo('echo remote execution with sudo')

‎python/ql/test/library-tests/security/command-execution/fabric_v2_test.py‎

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"""tests for the 'fabric' package (v2.x)
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Most of these examples are taken from the fabric documentation: http://docs.fabfile.org/en/2.5/getting-started.html
4+
See fabric-LICENSE for its' license.
5+
"""
6+
7+
from fabric import Connection
8+
9+
c = Connection('web1')
10+
result = c.run('uname -s')
11+
12+
c.run(command='echo run with kwargs')
13+
14+
15+
from fabric import SerialGroup as Group
16+
results = Group('web1', 'web2', 'mac1').run('uname -s')
17+
18+
19+
from fabric import SerialGroup as Group
20+
pool = Group('web1', 'web2', 'web3')
21+
pool.run('ls')
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23+
24+
25+
# using the 'fab' command-line tool
26+
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from fabric import task
28+
29+
@task
30+
def upload_and_unpack(c):
31+
if c.run('test -f /opt/mydata/myfile', warn=True).failed:
32+
c.put('myfiles.tgz', '/opt/mydata')
33+
c.run('tar -C /opt/mydata -xzvf /opt/mydata/myfiles.tgz')

‎python/ql/test/library-tests/security/command-execution/invoke_test.py‎

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"""tests for the 'invoke' package
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see https://www.pyinvoke.org/
4+
"""
5+
6+
import invoke
7+
8+
invoke.run('echo run')
9+
invoke.run(command='echo run with kwarg')
10+
11+
def with_sudo():
12+
invoke.sudo('whoami')
13+
invoke.sudo(command='whoami')
14+
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def manual_context():
16+
c = invoke.Context()
17+
c.run('echo run from manual context')
18+
manual_context()
19+
20+
def foo_helper(c):
21+
c.run('echo from foo_helper')
22+
23+
# for use with the 'invoke' command-line tool
24+
@invoke.task
25+
def foo(c):
26+
# 'c' is a invoke.context.Context
27+
c.run('echo task foo')
28+
foo_helper(c)
29+
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@invoke.task()
31+
def bar(c):
32+
c.run('echo task bar')

‎python/ql/test/library-tests/security/command-execution/options‎

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semmle-extractor-options: --max-import-depth=2 -p ../../../query-tests/Security/lib/

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