Require 'exact', 'prefix', or '' for match operation in property_contexts

The previous code would lazily check for 'exact' and accept any other
value as a prefix match.  This should be a tighter check allowing only
'exact', 'prefix', or an empty string for this option.

Test: build fails if an invalid string is used for the match operation
Test: build succeeds normally
Test: `getprop -Z` shows exact vs prefix is differentiated correctly
Change-Id: I21dcb193810d65f468f8960967eabfd261f71e21

init/host_init_verifier.cpp

@@ -191,7 +191,7 @@ void HandlePropertyContexts(const std::string& filename,
     }
 
     auto errors = std::vector<std::string>{};
-    ParsePropertyInfoFile(file_contents, property_infos, &errors);
+    ParsePropertyInfoFile(file_contents, true, property_infos, &errors);
     for (const auto& error : errors) {
         LOG(ERROR) << "Could not read line from '" << filename << "': " << error;
     }

init/property_service.cpp

@@ -925,7 +925,8 @@ bool LoadPropertyInfoFromFile(const std::string& filename,
     }
 
     auto errors = std::vector<std::string>{};
-    ParsePropertyInfoFile(file_contents, property_infos, &errors);
+    bool require_prefix_or_exact = SelinuxGetVendorAndroidVersion() >= __ANDROID_API_R__;
+    ParsePropertyInfoFile(file_contents, require_prefix_or_exact, property_infos, &errors);
     // Individual parsing errors are reported but do not cause a failed boot, which is what
     // returning false would do here.
     for (const auto& error : errors) {

property_service/libpropertyinfoserializer/include/property_info_serializer/property_info_serializer.h

@@ -14,8 +14,7 @@
 // limitations under the License.
 //
 
-#ifndef PROPERTY_INFO_SERIALIZER_H
-#define PROPERTY_INFO_SERIALIZER_H
+#pragma once
 
 #include <string>
 #include <vector>
@@ -41,11 +40,9 @@ bool BuildTrie(const std::vector<PropertyInfoEntry>& property_info,
                const std::string& default_context, const std::string& default_type,
                std::string* serialized_trie, std::string* error);
 
-void ParsePropertyInfoFile(const std::string& file_contents,
+void ParsePropertyInfoFile(const std::string& file_contents, bool require_prefix_or_exact,
                            std::vector<PropertyInfoEntry>* property_infos,
                            std::vector<std::string>* errors);
 
 }  // namespace properties
 }  // namespace android
-
-#endif

property_service/libpropertyinfoserializer/property_info_file.cpp

@@ -56,7 +56,8 @@ bool IsTypeValid(const std::vector<std::string>& type_strings) {
   return false;
 }
 
-bool ParsePropertyInfoLine(const std::string& line, PropertyInfoEntry* out, std::string* error) {
+bool ParsePropertyInfoLine(const std::string& line, bool require_prefix_or_exact,
+                           PropertyInfoEntry* out, std::string* error) {
   auto tokenizer = SpaceTokenizer(line);
 
   auto property = tokenizer.GetNext();
@@ -72,7 +73,7 @@ bool ParsePropertyInfoLine(const std::string& line, PropertyInfoEntry* out, std:
   }
 
   // It is not an error to not find exact_match or a type, as older files will not contain them.
-  auto exact_match = tokenizer.GetNext();
+  auto match_operation = tokenizer.GetNext();
   // We reformat type to be space deliminated regardless of the input whitespace for easier storage
   // and subsequent parsing.
   auto type_strings = std::vector<std::string>{};
@@ -82,18 +83,27 @@ bool ParsePropertyInfoLine(const std::string& line, PropertyInfoEntry* out, std:
     type = tokenizer.GetNext();
   }
 
+  bool exact_match = false;
+  if (match_operation == "exact") {
+    exact_match = true;
+  } else if (match_operation != "prefix" && match_operation != "" && require_prefix_or_exact) {
+    *error = "Match operation '" + match_operation +
+             "' is not valid: must be either 'prefix' or 'exact'";
+    return false;
+  }
+
   if (!type_strings.empty() && !IsTypeValid(type_strings)) {
     *error = "Type '" + Join(type_strings, " ") + "' is not valid";
     return false;
   }
 
-  *out = {property, context, Join(type_strings, " "), exact_match == "exact"};
+  *out = {property, context, Join(type_strings, " "), exact_match};
   return true;
 }
 
 }  // namespace
 
-void ParsePropertyInfoFile(const std::string& file_contents,
+void ParsePropertyInfoFile(const std::string& file_contents, bool require_prefix_or_exact,
                            std::vector<PropertyInfoEntry>* property_infos,
                            std::vector<std::string>* errors) {
   // Do not clear property_infos to allow this function to be called on multiple files, with
@@ -108,7 +118,8 @@ void ParsePropertyInfoFile(const std::string& file_contents,
 
     auto property_info_entry = PropertyInfoEntry{};
     auto parse_error = std::string{};
-    if (!ParsePropertyInfoLine(trimmed_line, &property_info_entry, &parse_error)) {
+    if (!ParsePropertyInfoLine(trimmed_line, require_prefix_or_exact, &property_info_entry,
+                               &parse_error)) {
       errors->emplace_back(parse_error);
       continue;
     }

property_service/property_info_checker/property_info_checker.cpp

@@ -153,7 +153,7 @@ int main(int argc, char** argv) {
     }
 
     auto errors = std::vector<std::string>{};
-    ParsePropertyInfoFile(file_contents, &property_info_entries, &errors);
+    ParsePropertyInfoFile(file_contents, true, &property_info_entries, &errors);
     if (!errors.empty()) {
       for (const auto& error : errors) {
         std::cerr << "Could not read line from '" << filename << "': " << error << std::endl;