[chromecast] Fix bugs in bluetooth_util::ParseUuid

BUG=internal b/78234633
TEST=cast_bluetooth_unittests

Change-Id: I2672aee77de583bf8a4292dd9fabc89e3cdc1476
Reviewed-on: https://chromium-review.googlesource.com/1017778Reviewed-by: Stephen Lanham <slan@chromium.org>
Commit-Queue: Bailey Forrest <bcf@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551869}

chromecast/device/bluetooth/bluetooth_util.cc

@@ -15,6 +15,7 @@ namespace {
 const int kMacAddrStrLen = 17;
 const int kUuid16bitLen = 4;
 const int kUuidHexNumChars = 32;
+const int kUuidNumDashes = 4;
 
 const char kFmtUuid[] =
     "%02hhx%02hhx%02hhx%02hhx-%02hhx%02hhx-%02hhx%02hhx"
@@ -59,18 +60,27 @@ std::string UuidToString(const bluetooth_v2_shlib::Uuid& uuid) {
 }
 
 bool ParseUuid(const std::string& str, bluetooth_v2_shlib::Uuid* uuid) {
-  // sscanf will incorrectly succeed if all characters except the last one are
-  // hex digits.
-  if (str.empty() || !std::isxdigit(str.back())) {
+  if (str.empty()) {
     return false;
   }
 
+  for (const auto& c : str) {
+    if (c != '-' && !std::isxdigit(c)) {
+      return false;
+    }
+  }
+
   // Check for 16-bit UUID
   if (str.size() == kUuid16bitLen) {
     *uuid = kUuidBase;
     return sscanf(str.c_str(), "%02hhx%02hhx", &(*uuid)[2], &(*uuid)[3]) == 2;
   }
 
+  if (str.size() > kUuidHexNumChars &&
+      str.size() != kUuidHexNumChars + kUuidNumDashes) {
+    return false;
+  }
+
   std::string no_dashes = str;
   no_dashes.erase(std::remove(no_dashes.begin(), no_dashes.end(), '-'),
                   no_dashes.end());

chromecast/device/bluetooth/bluetooth_util_test.cc

@@ -43,6 +43,10 @@ TEST(BluetoothUtilTest, AddrStringConversion) {
 TEST(BluetoothUtilTest, UuidStringConversion) {
   const char kBadUuid1[] = "hello";
   const char kBadUuid2[] = "a822c885-af02-c780-9d4d-bd9a1fa06d9z";
+  const char kBadUuid3[] = "00000000-0000-0000-0000-0x0000000000";
+  const char kBadUuid4[] = "123e-567-e89b-12d3-a456-426655440000";
+  const char kBadUuid5[] = "123e456--e89b-12d3-a456-426655440000";
+  const char kBadUuid6[] = "123e4567--e89b-12d3-a456-426655440000";
 
   const char kUuid1[] = "123e4567-e89b-12d3-a456-426655440000";
   const char kUuid2[] = "123E4567-E89B-12D3-A456-426655440000";
@@ -64,6 +68,10 @@ TEST(BluetoothUtilTest, UuidStringConversion) {
   bluetooth_v2_shlib::Uuid uuid;
   EXPECT_FALSE(ParseUuid(kBadUuid1, &uuid));
   EXPECT_FALSE(ParseUuid(kBadUuid2, &uuid));
+  EXPECT_FALSE(ParseUuid(kBadUuid3, &uuid));
+  EXPECT_FALSE(ParseUuid(kBadUuid4, &uuid));
+  EXPECT_FALSE(ParseUuid(kBadUuid5, &uuid));
+  EXPECT_FALSE(ParseUuid(kBadUuid6, &uuid));
 
   EXPECT_TRUE(ParseUuid(kUuid1, &uuid));
   EXPECT_EQ(kGoodBytes1, uuid);