Verify the SELabels used in property_contexts

Verify that the SELabels used in property_contexts correspond to a
real type in the SEPolicy and that this type has the property_type attribute.

Bug: 74078792
Test: Build property_contexts on bullhead successfully
Test: See failure when using a faulty SELabel in property_contexts
Change-Id: If1618c2c3dae4c0cd3efa5f88056478a6db6bd0b

property_service/property_info_checker/Android.bp

@@ -7,6 +7,7 @@ cc_binary {
         "libpropertyinfoserializer",
         "libpropertyinfoparser",
         "libbase",
+        "libsepol",
     ],
     srcs: ["property_info_checker.cpp"],
 }

property_service/property_info_checker/property_info_checker.cpp

@@ -1,26 +1,150 @@
 #include <iostream>
+#include <memory>
 #include <string>
 #include <vector>
 
 #include <android-base/file.h>
-
+#include <property_info_parser/property_info_parser.h>
 #include <property_info_serializer/property_info_serializer.h>
+#include <sepol/context.h>
+#include <sepol/context_record.h>
+#include <sepol/handle.h>
+#include <sepol/policydb.h>
+#include <sepol/policydb/policydb.h>
 
 using android::base::ReadFileToString;
 using android::properties::BuildTrie;
 using android::properties::ParsePropertyInfoFile;
+using android::properties::PropertyInfoArea;
 using android::properties::PropertyInfoEntry;
 
+class ContextChecker {
+ public:
+  ContextChecker()
+      : policy_file_(nullptr),
+        sepol_handle_(nullptr),
+        sepol_policy_file_(nullptr),
+        sepol_policy_db_(nullptr) {}
+
+  ~ContextChecker() {
+    if (sepol_policy_db_ != nullptr) {
+      sepol_policydb_free(sepol_policy_db_);
+    }
+
+    if (sepol_policy_file_ != nullptr) {
+      sepol_policy_file_free(sepol_policy_file_);
+    }
+
+    if (sepol_handle_ != nullptr) {
+      sepol_handle_destroy(sepol_handle_);
+    }
+
+    if (policy_file_ != nullptr) {
+      fclose(policy_file_);
+    }
+  }
+
+  bool Initialize(const char* policy_file) {
+    policy_file_ = fopen(policy_file, "re");
+    if (policy_file_ == nullptr) {
+      std::cerr << "Could not open policy file, " << policy_file << std::endl;
+      return false;
+    }
+
+    sepol_handle_ = sepol_handle_create();
+    if (sepol_handle_ == nullptr) {
+      std::cerr << "Could not create policy handle." << std::endl;
+      return false;
+    }
+
+    if (sepol_policy_file_create(&sepol_policy_file_) < 0) {
+      std::cerr << "Could not create policy file." << std::endl;
+      return false;
+    }
+
+    if (sepol_policydb_create(&sepol_policy_db_) < 0) {
+      std::cerr << "Could not create policy db." << std::endl;
+      return false;
+    }
+
+    sepol_policy_file_set_fp(sepol_policy_file_, policy_file_);
+    sepol_policy_file_set_handle(sepol_policy_file_, sepol_handle_);
+
+    if (sepol_policydb_read(sepol_policy_db_, sepol_policy_file_) < 0) {
+      std::cerr << "Could not read policy file into policy db." << std::endl;
+      return false;
+    }
+
+    auto* attr =
+        reinterpret_cast<type_datum*>(hashtab_search(policy_db_->p_types.table, "property_type"));
+    if (attr == nullptr || attr->flavor != TYPE_ATTRIB) {
+      std::cerr << "'property_type' is not defined correctly." << std::endl;
+      return false;
+    }
+
+    property_type_bit_ = attr->s.value - 1;
+
+    return true;
+  }
+
+  bool CheckContext(const char* context) {
+    sepol_context_t* sepol_context_raw;
+    if (sepol_context_from_string(sepol_handle_, context, &sepol_context_raw) < 0) {
+      std::cerr << "Could not allocate context for " << context << std::endl;
+      return false;
+    }
+    auto sepol_context = std::unique_ptr<sepol_context_t, decltype(&sepol_context_free)>{
+        sepol_context_raw, sepol_context_free};
+
+    if (sepol_context_check(sepol_handle_, sepol_policy_db_, sepol_context.get()) < 0) {
+      std::cerr << "Sepol context check failed for " << context << std::endl;
+      return false;
+    }
+
+    const char* context_type = sepol_context_get_type(sepol_context.get());
+
+    auto* type =
+        reinterpret_cast<type_datum*>(hashtab_search(policy_db_->p_types.table, context_type));
+    if (type == nullptr) {
+      std::cerr << "Could not find context '" << context << "' in policy database" << std::endl;
+      return false;
+    }
+
+    if (type->flavor != TYPE_TYPE) {
+      std::cerr << "Context '" << context << "' is not defined as a type in policy database"
+                << std::endl;
+      return false;
+    }
+
+    if (!ebitmap_get_bit(&policy_db_->type_attr_map[type->s.value - 1], property_type_bit_)) {
+      std::cerr << "Context '" << context << "' does not have property_type attribute" << std::endl;
+      return false;
+    }
+
+    return true;
+  }
+
+ private:
+  FILE* policy_file_;
+  sepol_handle_t* sepol_handle_;
+  sepol_policy_file_t* sepol_policy_file_;
+  union {
+    sepol_policydb_t* sepol_policy_db_;
+    policydb_t* policy_db_;
+  };
+  unsigned int property_type_bit_;
+};
+
 int main(int argc, char** argv) {
-  if (argc < 2) {
-    std::cerr << "A list of property info files to be checked is expected on the command line"
-              << std::endl;
+  if (argc < 3) {
+    std::cerr << "usage: " << argv[0]
+              << " COMPILED_SEPOLICY PROPERTY_INFO_FILE [PROPERTY_INFO_FILE]..." << std::endl;
     return -1;
   }
 
   auto property_info_entries = std::vector<PropertyInfoEntry>{};
 
-  for (int i = 1; i < argc; ++i) {
+  for (int i = 2; i < argc; ++i) {
     auto filename = argv[i];
     auto file_contents = std::string{};
     if (!ReadFileToString(filename, &file_contents)) {
@@ -47,5 +171,17 @@ int main(int argc, char** argv) {
     return -1;
   }
 
+  auto checker = ContextChecker{};
+  if (!checker.Initialize(argv[1])) {
+    return -1;
+  }
+
+  auto property_info_area = reinterpret_cast<PropertyInfoArea*>(serialized_contexts.data());
+  for (size_t i = 0; i < property_info_area->num_contexts(); ++i) {
+    if (!checker.CheckContext(property_info_area->context(i))) {
+      return -1;
+    }
+  }
+
   return 0;
 }