Add new AvoidSecretDisclosure rule

Rules/AvoidSecretDisclosure.cs

@@ -0,0 +1,181 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+using System.Collections.Generic;
+#if !CORECLR
+using System.ComponentModel.Composition;
+#endif
+using System.Globalization;
+using System.Linq;
+using System.Management.Automation.Language;
+using Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic;
+
+namespace Microsoft.Windows.PowerShell.ScriptAnalyzer.BuiltinRules
+{
+    /// <summary>
+    /// AvoidSecretDisclosure: Checks whether a plaintext secret is being retrieved which can lead
+    /// to security vulnerabilities such as memory trails or logging trails.
+    /// The general approach of dealing with credentials is to avoid them and instead rely on other
+    ///  means to authenticate, such as certificates or Windows authentication.
+    /// </summary>
+#if !CORECLR
+    [Export(typeof(IScriptRule))]
+#endif
+    public class AvoidSecretDisclosure : ConfigurableRule
+    {
+
+        /// <summary>
+        /// Construct an object of AvoidSecretDisclosure type.
+        /// </summary>
+        public AvoidSecretDisclosure() {
+            Enable = false;
+        }
+
+        /// <summary>
+        /// Analyzes the given ast to find the [violation]
+        /// </summary>
+        /// <param name="ast">AST to be analyzed. This should be non-null</param>
+        /// <param name="fileName">Name of file that corresponds to the input AST.</param>
+        /// <returns>A an enumerable type containing the violations</returns>
+        public override IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
+        {
+            if (ast == null) throw new ArgumentNullException(Strings.NullAstErrorMessage);
+
+            // Check for ConvertFrom-SecureString with -AsPlainText parameter
+            IEnumerable<CommandAst> convertFromSecureStringAsts = ast.FindAll(testAst =>
+                testAst is CommandAst cmdAst &&
+                cmdAst.GetCommandName() != null &&
+                cmdAst.GetCommandName().Equals("ConvertFrom-SecureString", StringComparison.OrdinalIgnoreCase),
+                true
+            ).Cast<CommandAst>();
+
+            foreach (CommandAst cmdAst in convertFromSecureStringAsts)
+            {
+                // Use StaticParameterBinder to reliably get parameter values
+                var bindingResult = StaticParameterBinder.BindCommand(cmdAst, true);
+
+                // Check for -AsPlainText parameter
+                // The constantValue appears true even the value is a variable
+                // This is ok because the rule should still trigger in that case since the value of the
+                // variable could be true at runtime, and we want to catch all potential violations
+                if (
+                    bindingResult.BoundParameters.TryGetValue("AsPlainText", out ParameterBindingResult asPlainTextBinding) &&
+                    asPlainTextBinding.ConstantValue is bool constantValue &&
+                    constantValue == true
+                ) {
+                    yield return GetDiagnosticRecord(cmdAst.Extent, fileName, "AsPlainText");
+                }
+            }
+
+            // Check for any invocation of a method that starts with "SecureStringTo"
+            // (e.g. SecureStringToBSTR, SecureStringToCoTaskMemAnsi, etc.)
+            IEnumerable<InvokeMemberExpressionAst> secureStringToAsts = ast.FindAll(testAst =>
+                testAst is InvokeMemberExpressionAst invokeAst &&
+                invokeAst.Member != null &&
+                invokeAst.Member.ToString().StartsWith("SecureStringTo", StringComparison.OrdinalIgnoreCase),
+                true
+            ).Cast<InvokeMemberExpressionAst>();
+
+            foreach (InvokeMemberExpressionAst secureStringToAst in secureStringToAsts) {
+                yield return GetDiagnosticRecord(secureStringToAst.Extent, fileName, secureStringToAst.Member.ToString());
+            }
+
+            // Check for any member access of a property named "Password".
+            // Note that this is a heuristic and may lead to false positives,
+            // as not all properties named "Password" necessarily contain secrets,
+            // and there may be secrets stored in properties with other names.
+            // However, it is too complex to reliably determine whether a Password
+            // property is a result of e.g. a PSCredential.GetNetworkCredential() call.
+            // Anyways, this is still a useful common check to have.
+            IEnumerable<MemberExpressionAst> passwordAsts = ast.FindAll(testAst =>
+                testAst is MemberExpressionAst memberAst &&
+                memberAst.Member != null &&
+                string.Equals(memberAst.Member.ToString(), "Password", StringComparison.OrdinalIgnoreCase),
+                true
+            ).Cast<MemberExpressionAst>();
+
+            foreach (MemberExpressionAst passwordAst in passwordAsts) {
+                yield return GetDiagnosticRecord(passwordAst.Extent, fileName, passwordAst.Member.ToString());
+            }
+
+        }
+
+        /// <summary>
+        /// Helper function to create a DiagnosticRecord for a given violation
+        /// </summary>
+        private DiagnosticRecord GetDiagnosticRecord(IScriptExtent Extent, string fileName, string suppressionId)
+        {
+            return new DiagnosticRecord(
+                Strings.AvoidSecretDisclosureError,
+                Extent,
+                GetName(),
+                DiagnosticSeverity.Warning,
+                fileName,
+                suppressionId
+            );
+        }
+
+        /// <summary>
+        /// Retrieves the common name of this rule.
+        /// </summary>
+        public override string GetCommonName()
+        {
+            return string.Format(CultureInfo.CurrentCulture, Strings.AvoidSecretDisclosureCommonName);
+        }
+
+        /// <summary>
+        /// Retrieves the description of this rule.
+        /// </summary>
+        public override string GetDescription()
+        {
+            return string.Format(CultureInfo.CurrentCulture, Strings.AvoidSecretDisclosureDescription);
+        }
+
+        /// <summary>
+        /// Retrieves the name of this rule.
+        /// </summary>
+        public override string GetName()
+        {
+            return string.Format(
+                CultureInfo.CurrentCulture,
+                Strings.NameSpaceFormat,
+                GetSourceName(),
+                Strings.AvoidSecretDisclosureName);
+        }
+
+        /// <summary>
+        /// Retrieves the severity of the rule: error, warning or information.
+        /// </summary>
+        public override RuleSeverity GetSeverity()
+        {
+            return RuleSeverity.Warning;
+        }
+
+        /// <summary>
+        /// Gets the severity of the returned diagnostic record: error, warning, or information.
+        /// </summary>
+        /// <returns></returns>
+        public DiagnosticSeverity GetDiagnosticSeverity()
+        {
+            return DiagnosticSeverity.Warning;
+        }
+
+        /// <summary>
+        /// Retrieves the name of the module/assembly the rule is from.
+        /// </summary>
+        public override string GetSourceName()
+        {
+            return string.Format(CultureInfo.CurrentCulture, Strings.SourceName);
+        }
+
+        /// <summary>
+        /// Retrieves the type of the rule, Builtin, Managed or Module.
+        /// </summary>
+        public override SourceType GetSourceType()
+        {
+            return SourceType.Builtin;
+        }
+    }
+}
+

Rules/Strings.resx

@@ -921,6 +921,18 @@
   <data name="AvoidLongLinesError" xml:space="preserve">
     <value>Line exceeds the configured maximum length of {0} characters</value>
   </data>
+  <data name="AvoidSecretDisclosureName" xml:space="preserve">
+    <value>AvoidSecretDisclosure</value>
+  </data>
+  <data name="AvoidSecretDisclosureCommonName" xml:space="preserve">
+    <value>Avoid secret disclosure</value>
+  </data>
+  <data name="AvoidSecretDisclosureDescription" xml:space="preserve">
+    <value>Disclosing a secret might result in security vulnerabilities such as memory trails or logging trails</value>
+  </data>
+  <data name="AvoidSecretDisclosureError" xml:space="preserve">
+    <value>Avoid disclosing a secret</value>
+  </data>
   <data name="AvoidSemicolonsAsLineTerminatorsName" xml:space="preserve">
     <value>AvoidSemicolonsAsLineTerminators</value>
   </data>