AU: Verify source rootfs/kernel hashes before applying delta.

omaha_hash_calculator.cc

Index: omaha_hash_calculator.cc
diff --git a/omaha_hash_calculator.cc b/omaha_hash_calculator.cc
index fdc70f01990ad136238efc99042d7b86f008e076..ac4edf480d6589846192cd70318a538a76fa2f8e 100644
--- a/omaha_hash_calculator.cc
+++ b/omaha_hash_calculator.cc
@@ -113,6 +113,20 @@ bool OmahaHashCalculator::RawHashOfData(const vector<char>& data,
   return true;
 }
 
+off_t OmahaHashCalculator::RawHashOfFile(const std::string& name, off_t length,
+                                         std::vector<char>* out_hash) {
+  OmahaHashCalculator calc;
+  off_t res = calc.UpdateFile(name, length);
+  if (res < 0) {
+    return res;
+  }
+  if (!calc.Finalize()) {
+    return -1;
+  }
+  *out_hash = calc.raw_hash();
+  return res;
+}
+
 string OmahaHashCalculator::OmahaHashOfBytes(
     const void* data, size_t length) {
   OmahaHashCalculator calc;