Refactors GetDeviceIdentifier()

This refactors GetDeviceIdentifier function into GetDeviceIdentifier
and GetSaltedString. GetSaltedString is a utility function that can
be used elsewhere.

Review URL: https://codereview.chromium.org/309963003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@274520 0039d316-1c4b-4281-b951-d872f2087c98

base/ios/device_util.h

@@ -72,6 +72,12 @@ std::string GetRandomId();
 // something that should be anonymous, you should probably pass NULL.
 std::string GetDeviceIdentifier(const char* salt);
 
+// Returns a hashed version of |in_string| using |salt| (which must not
+// zero-length). Different salt values should result in differently hashed
+// strings.
+std::string GetSaltedString(const std::string& in_string,
+                            const std::string& salt);
+
 }  // namespace device_util
 }  // namespace ios
 

base/ios/device_util.mm

@@ -157,8 +157,16 @@ std::string GetDeviceIdentifier(const char* salt) {
     [defaults synchronize];
   }
 
-  NSData* hash_data = [[NSString stringWithFormat:@"%@%s", client_id,
-      salt ? salt : kDefaultSalt] dataUsingEncoding:NSUTF8StringEncoding];
+  return GetSaltedString([client_id UTF8String], salt ? salt : kDefaultSalt);
+}
+
+std::string GetSaltedString(const std::string& in_string,
+                            const std::string& salt) {
+  DCHECK(in_string.length());
+  DCHECK(salt.length());
+  NSData* hash_data =
+      [[NSString stringWithFormat:@"%s%s", in_string.c_str(), salt.c_str()]
+          dataUsingEncoding:NSUTF8StringEncoding];
 
   unsigned char hash[CC_SHA256_DIGEST_LENGTH];
   CC_SHA256([hash_data bytes], [hash_data length], hash);

base/ios/device_util_unittest.mm

@@ -99,6 +99,33 @@ TEST_F(DeviceUtilTest, CheckMigrationFromZero) {
   CleanNSUserDefaultsForDeviceId();
 }
 
+TEST_F(DeviceUtilTest, GetSaltedStringEquals) {
+  std::string string1("The quick brown fox jumps over the lazy dog");
+  std::string string2("The quick brown fox jumps over the lazy dog");
+  std::string salt("salt");
+  // Same string and same salt should result in the same salted string.
+  EXPECT_EQ(ios::device_util::GetSaltedString(string1, salt),
+            ios::device_util::GetSaltedString(string2, salt));
+}
+
+TEST_F(DeviceUtilTest, GetSaltedStringNotEquals) {
+  std::string string1("The quick brown fox jumps over the lazy dog");
+  std::string string2("The lazy brown fox jumps over the quick dog");
+  std::string salt("salt");
+  // Different string and same salt should result in different salted strings.
+  EXPECT_NE(ios::device_util::GetSaltedString(string1, salt),
+            ios::device_util::GetSaltedString(string2, salt));
+}
+
+TEST_F(DeviceUtilTest, GetSaltedStringDifferentSalt) {
+  std::string string1("The quick brown fox jumps over the lazy dog");
+  std::string salt1("salt");
+  std::string salt2("pepper");
+  // Same string with different salt should result in different salted strings.
+  EXPECT_NE(ios::device_util::GetSaltedString(string1, salt1),
+            ios::device_util::GetSaltedString(string1, salt2));
+}
+
 TEST_F(DeviceUtilTest, CheckDeviceMigration) {
   CleanNSUserDefaultsForDeviceId();