Swift: Add the shared SensitiveDataHeuristics.qll to Swift.

Author: geoffw0

config/identical-files.json

@@ -512,7 +512,8 @@
   "SensitiveDataHeuristics Python/JS": [
     "javascript/ql/lib/semmle/javascript/security/internal/SensitiveDataHeuristics.qll",
     "python/ql/lib/semmle/python/security/internal/SensitiveDataHeuristics.qll",
-    "ruby/ql/lib/codeql/ruby/security/internal/SensitiveDataHeuristics.qll"
+    "ruby/ql/lib/codeql/ruby/security/internal/SensitiveDataHeuristics.qll",
+    "swift/ql/lib/codeql/swift/security/internal/SensitiveDataHeuristics.qll"
   ],
   "CFG": [
     "csharp/ql/lib/semmle/code/csharp/controlflow/internal/ControlFlowGraphImplShared.qll",
@@ -599,4 +600,4 @@
     "python/ql/lib/semmle/python/security/internal/EncryptionKeySizes.qll",
     "java/ql/lib/semmle/code/java/security/internal/EncryptionKeySizes.qll"
   ]
-}
+}

swift/ql/lib/codeql/swift/security/internal/SensitiveDataHeuristics.qll

@@ -0,0 +1,124 @@
+/**
+ * INTERNAL: Do not use.
+ *
+ * Provides classes and predicates for identifying strings that may indicate the presence of sensitive data.
+ * Such that we can share this logic across our CodeQL analysis of different languages.
+ *
+ * 'Sensitive' data in general is anything that should not be sent around in unencrypted form.
+ */
+
+/**
+ * A classification of different kinds of sensitive data:
+ *
+ *   - secret: generic secret or trusted data;
+ *   - id: a user name or other account information;
+ *   - password: a password or authorization key;
+ *   - certificate: a certificate.
+ *
+ * While classifications are represented as strings, this should not be relied upon.
+ * Instead, use the predicates in `SensitiveDataClassification::` to work with
+ * classifications.
+ */
+class SensitiveDataClassification extends string {
+  SensitiveDataClassification() { this in ["secret", "id", "password", "certificate"] }
+}
+
+/**
+ * Provides predicates to select the different kinds of sensitive data we support.
+ */
+module SensitiveDataClassification {
+  /** Gets the classification for secret or trusted data. */
+  SensitiveDataClassification secret() { result = "secret" }
+
+  /** Gets the classification for user names or other account information. */
+  SensitiveDataClassification id() { result = "id" }
+
+  /** Gets the classification for passwords or authorization keys. */
+  SensitiveDataClassification password() { result = "password" }
+
+  /** Gets the classification for certificates. */
+  SensitiveDataClassification certificate() { result = "certificate" }
+}
+
+/**
+ * INTERNAL: Do not use.
+ *
+ * Provides heuristics for identifying names related to sensitive information.
+ */
+module HeuristicNames {
+  /**
+   * Gets a regular expression that identifies strings that may indicate the presence of secret
+   * or trusted data.
+   */
+  string maybeSecret() { result = "(?is).*((?<!is|is_)secret|(?<!un|un_|is|is_)trusted).*" }
+
+  /**
+   * Gets a regular expression that identifies strings that may indicate the presence of
+   * user names or other account information.
+   */
+  string maybeAccountInfo() {
+    result = "(?is).*acc(ou)?nt.*" or
+    result = "(?is).*(puid|username|userid|session(id|key)).*" or
+    result = "(?s).*([uU]|^|_|[a-z](?=U))([uU][iI][dD]).*"
+  }
+
+  /**
+   * Gets a regular expression that identifies strings that may indicate the presence of
+   * a password or an authorization key.
+   */
+  string maybePassword() {
+    result = "(?is).*pass(wd|word|code|phrase)(?!.*question).*" or
+    result = "(?is).*(auth(entication|ori[sz]ation)?)key.*"
+  }
+
+  /**
+   * Gets a regular expression that identifies strings that may indicate the presence of
+   * a certificate.
+   */
+  string maybeCertificate() { result = "(?is).*(cert)(?!.*(format|name)).*" }
+
+  /**
+   * Gets a regular expression that identifies strings that may indicate the presence
+   * of sensitive data, with `classification` describing the kind of sensitive data involved.
+   */
+  string maybeSensitiveRegexp(SensitiveDataClassification classification) {
+    result = maybeSecret() and classification = SensitiveDataClassification::secret()
+    or
+    result = maybeAccountInfo() and classification = SensitiveDataClassification::id()
+    or
+    result = maybePassword() and classification = SensitiveDataClassification::password()
+    or
+    result = maybeCertificate() and
+    classification = SensitiveDataClassification::certificate()
+  }
+
+  /**
+   * Gets a regular expression that identifies strings that may indicate the presence of data
+   * that is hashed or encrypted, and hence rendered non-sensitive, or contains special characters
+   * suggesting nouns within the string do not represent the meaning of the whole string (e.g. a URL or a SQL query).
+   *
+   * We also filter out common words like `certain` and `concert`, since otherwise these could
+   * be matched by the certificate regular expressions. Same for `accountable` (account), or
+   * `secretarial` (secret).
+   */
+  string notSensitiveRegexp() {
+    result =
+      "(?is).*([^\\w$.-]|redact|censor|obfuscate|hash|md5|sha|random|((?<!un)(en))?(crypt|(?<!pass)code)|certain|concert|secretar|accountant|accountab).*"
+  }
+
+  /**
+   * Holds if `name` may indicate the presence of sensitive data, and
+   * `name` does not indicate that the data is in fact non-sensitive (for example since
+   * it is hashed or encrypted). `classification` describes the kind of sensitive data
+   * involved.
+   *
+   * That is, one of the regexps from `maybeSensitiveRegexp` matches `name` (with the
+   * given classification), and none of the regexps from `notSensitiveRegexp` matches
+   * `name`.
+   */
+  bindingset[name]
+  predicate nameIndicatesSensitiveData(string name, SensitiveDataClassification classification) {
+    name.regexpMatch(maybeSensitiveRegexp(classification)) and
+    not name.regexpMatch(notSensitiveRegexp())
+  }
+}