Implement stdin models

Unfortunately due to how variable and varargs work, these are better
done in QL

Author: egregius313

go/ql/lib/semmle/go/frameworks/stdlib/Fmt.qll

@@ -112,6 +112,15 @@ module Fmt {
     Scanner() { this.hasQualifiedName("fmt", ["Scan", "Scanf", "Scanln"]) }
   }
 
+  private class ScannerSource extends SourceNode {
+    ScannerSource() {
+      // All of the arguments which are sources are varargs.
+      this.asExpr() = any(Scanner s).getACall().getAnImplicitVarargsArgument().asExpr()
+    }
+
+    override string getThreatModel() { result = "stdin" }
+  }
+
   /**
    * The `Fscan` function or one of its variants,
    * all of which read from a specified `io.Reader`.

go/ql/lib/semmle/go/frameworks/stdlib/Os.qll

@@ -43,4 +43,14 @@ module Os {
       input = inp and output = outp
     }
   }
+
+  private class Stdin extends SourceNode {
+    Stdin() {
+      exists(Variable osStdin | osStdin.hasQualifiedName("os", "Stdin") |
+        this.asExpr() = osStdin.getARead().asExpr()
+      )
+    }
+
+    override string getThreatModel() { result = "stdin" }
+  }
 }

go/ql/test/library-tests/semmle/go/dataflow/flowsources/local/stdin/go.mod

@@ -0,0 +1,3 @@
+module test
+
+go 1.22.6

go/ql/test/library-tests/semmle/go/dataflow/flowsources/local/stdin/source.ext.yml

@@ -0,0 +1,7 @@
+extensions:
+
+  - addsTo:
+      pack: codeql/threat-models
+      extensible: threatModelConfiguration
+    data:
+      - ["stdin", true, 0]

go/ql/test/library-tests/semmle/go/dataflow/flowsources/local/stdin/source.ql

@@ -0,0 +1,19 @@
+import go
+import ModelValidation
+import TestUtilities.InlineExpectationsTest
+
+module SourceTest implements TestSig {
+  string getARelevantTag() { result = "source" }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(ThreatModelFlowSource s |
+      s.hasLocationInfo(location.getFile().getAbsolutePath(), location.getStartLine(),
+        location.getStartColumn(), location.getEndLine(), location.getEndColumn()) and
+      element = s.toString() and
+      value = "" and
+      tag = "source"
+    )
+  }
+}
+
+import MakeTest<SourceTest>

go/ql/test/library-tests/semmle/go/dataflow/flowsources/local/stdin/test.expected

@@ -0,0 +1,2 @@
+testFailures
+invalidModelRow

go/ql/test/library-tests/semmle/go/dataflow/flowsources/local/stdin/test.ext.yml

@@ -0,0 +1,7 @@
+extensions:
+
+  - addsTo:
+      pack: codeql/threat-models
+      extensible: threatModelConfiguration
+    data:
+      - ["stdin", true, 0]

go/ql/test/library-tests/semmle/go/dataflow/flowsources/local/stdin/test.go

@@ -0,0 +1,48 @@
+package test
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func sink(string) {
+
+}
+
+func readStdinBuffer() {
+	buf := make([]byte, 1024)
+	n, err := os.Stdin.Read(buf) // $source
+	if err != nil {
+		return
+	}
+	sink(string(buf[:n])) // $hasTaintFlow="type conversion"
+}
+
+func readStdinBuffReader() {
+	buf := make([]byte, 1024)
+	r := bufio.NewReader(os.Stdin) // $source
+	n, err := r.Read(buf)
+	if err != nil {
+		return
+	}
+	sink(string(buf[:n])) // $hasTaintFlow="type conversion"
+}
+
+func scan() {
+	var username, email string
+	fmt.Scan(&username, &email) // $source
+	sink(username)              // $hasTaintFlow="username"
+}
+
+func scanf() {
+	var s string
+	fmt.Scanf("%s", &s) // $source
+	sink(s)             // $hasTaintFlow="s"
+}
+
+func scanl() {
+	var s string
+	fmt.Scanln(&s) // $source
+	sink(s)        // $hasTaintFlow="s"
+}

go/ql/test/library-tests/semmle/go/dataflow/flowsources/local/stdin/test.ql

@@ -0,0 +1,15 @@
+import go
+import semmle.go.dataflow.ExternalFlow
+import ModelValidation
+import experimental.frameworks.CleverGo
+import TestUtilities.InlineFlowTest
+
+module Config implements DataFlow::ConfigSig {
+  predicate isSource(DataFlow::Node source) { source instanceof ThreatModelFlowSource }
+
+  predicate isSink(DataFlow::Node sink) {
+    sink.asExpr() = any(CallExpr c | c.getTarget().getName() = "sink").getArgument(0)
+  }
+}
+
+import TaintFlowTest<Config>