Add taint-tracking for context package

Author: gagliardetto

ql/src/semmle/go/frameworks/Stdlib.qll

@@ -15,6 +15,7 @@ import semmle.go.frameworks.stdlib.CompressZlib
 import semmle.go.frameworks.stdlib.Mime
 import semmle.go.frameworks.stdlib.MimeMultipart
 import semmle.go.frameworks.stdlib.MimeQuotedprintable
+import semmle.go.frameworks.stdlib.Context
 import semmle.go.frameworks.stdlib.Path
 import semmle.go.frameworks.stdlib.PathFilepath
 import semmle.go.frameworks.stdlib.Reflect

ql/src/semmle/go/frameworks/stdlib/Context.qll

@@ -0,0 +1,50 @@
+/**
+ * Provides classes modeling security-relevant aspects of the `context` package.
+ */
+
+import go
+
+/** Provides models of commonly used functions in the `context` package. */
+module Context {
+  private class FunctionModels extends TaintTracking::FunctionModel {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    FunctionModels() {
+      // signature: func WithCancel(parent Context) (ctx Context, cancel CancelFunc)
+      hasQualifiedName("context", "WithCancel") and
+      (inp.isParameter(0) and outp.isResult(0))
+      or
+      // signature: func WithDeadline(parent Context, d time.Time) (Context, CancelFunc)
+      hasQualifiedName("context", "WithDeadline") and
+      (inp.isParameter(0) and outp.isResult(0))
+      or
+      // signature: func WithTimeout(parent Context, timeout time.Duration) (Context, CancelFunc)
+      hasQualifiedName("context", "WithTimeout") and
+      (inp.isParameter(0) and outp.isResult(0))
+      or
+      // signature: func WithValue(parent Context, key interface{}, val interface{}) Context
+      hasQualifiedName("context", "WithValue") and
+      (inp.isParameter(_) and outp.isResult())
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+
+  private class MethodModels extends TaintTracking::FunctionModel, Method {
+    FunctionInput inp;
+    FunctionOutput outp;
+
+    MethodModels() {
+      // signature: func (Context).Value(key interface{}) interface{}
+      this.implements("context", "Context", "Value") and
+      (inp.isReceiver() and outp.isResult())
+    }
+
+    override predicate hasTaintFlow(FunctionInput input, FunctionOutput output) {
+      input = inp and output = outp
+    }
+  }
+}