Add timeout to DMG analysis

To limit regression in the total analysis time from Safe Browsing,
cutoff DMG analysis at 10 seconds. Future CLs will institute similar
timeouts for ZIP and RAR archives.

Bug: 948277
Change-Id: Iff7dabfdecc1791d5a83e36dc34a8c57ed99fd9e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1594166Reviewed-by: Nathan Parker <nparker@chromium.org>
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Cr-Commit-Position: refs/heads/master@{#657415}

chrome/utility/safe_browsing/mac/dmg_analyzer.cc

@@ -14,6 +14,7 @@
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/time/time.h"
 #include "chrome/common/safe_browsing/archive_analyzer_results.h"
 #include "chrome/common/safe_browsing/binary_feature_extractor.h"
 #include "chrome/common/safe_browsing/mach_o_image_reader_mac.h"
@@ -28,6 +29,9 @@ namespace dmg {
 
 namespace {
 
+// The maximum duration of DMG analysis, in milliseconds.
+const double kDmgAnalysisTimeoutMs = 10000;
+
 // MachOFeatureExtractor examines files to determine if they are Mach-O, and,
 // if so, it uses the BinaryFeatureExtractor to obtain information about the
 // image. In addition, this class will compute the SHA256 hash of the file.
@@ -133,6 +137,7 @@ void AnalyzeDMGFile(base::File dmg_file, ArchiveAnalyzerResults* results) {
 }
 
 void AnalyzeDMGFile(DMGIterator* iterator, ArchiveAnalyzerResults* results) {
+  base::Time start_time = base::Time::Now();
   results->success = false;
 
   if (!iterator->Open())
@@ -142,10 +147,16 @@ void AnalyzeDMGFile(DMGIterator* iterator, ArchiveAnalyzerResults* results) {
 
   results->signature_blob = iterator->GetCodeSignature();
 
+  bool timeout = false;
   while (iterator->Next()) {
     std::unique_ptr<ReadStream> stream = iterator->GetReadStream();
     if (!stream)
       continue;
+    if (base::Time::Now() - start_time >=
+        base::TimeDelta::FromMilliseconds(kDmgAnalysisTimeoutMs)) {
+      timeout = true;
+      break;
+    }
 
     std::string path = base::UTF16ToUTF8(iterator->GetPath());
 
@@ -187,6 +198,7 @@ void AnalyzeDMGFile(DMGIterator* iterator, ArchiveAnalyzerResults* results) {
     }
   }
 
+  if (!timeout)
     results->success = true;
 }