Adjust Uri host parsing to use last instead of first @.

Malformed authority segments can currently cause the parser to produce
a hostname that doesn't match the hostname produced by the WHATWG URL
parsing algorithm* used by browsers, which means that a URL could be seen
as having a "safe" host when checked by an Android app but actually visit
a different host when passed to a browser.  The WHATWG URL parsing
algorithm always produces a hostname based on the last @ in the authority
segment, so we do the same.

* https://url.spec.whatwg.org/#authority-state resets the "buffer", which
  is being used to build up the host name, each time an @ is found, so it
  has the effect of using the content between the final @ and the end
  of the authority section as the hostname.

Bug: 68341964
Test: vogar android.net.UriTest (on NYC branch)
Test: cts -m CtsNetTestCases (on NYC branch)
Change-Id: Idca79f35a886de042c94d6ab66787c2e98ac8376

core/java/android/net/Uri.java

@@ -1060,7 +1060,7 @@ private String parseUserInfo() {
                 return null;
             }
 
-            int end = authority.indexOf('@');
+            int end = authority.lastIndexOf('@');
             return end == NOT_FOUND ? null : authority.substring(0, end);
         }
 
@@ -1084,7 +1084,7 @@ private String parseHost() {
             }
 
             // Parse out user info and then port.
-            int userInfoSeparator = authority.indexOf('@');
+            int userInfoSeparator = authority.lastIndexOf('@');
             int portSeparator = authority.indexOf(':', userInfoSeparator);
 
             String encodedHost = portSeparator == NOT_FOUND
@@ -1110,7 +1110,7 @@ private int parsePort() {
 
             // Make sure we look for the port separtor *after* the user info
             // separator. We have URLs with a ':' in the user info.
-            int userInfoSeparator = authority.indexOf('@');
+            int userInfoSeparator = authority.lastIndexOf('@');
             int portSeparator = authority.indexOf(':', userInfoSeparator);
 
             if (portSeparator == NOT_FOUND) {

core/tests/coretests/src/android/net/UriTest.java

@@ -187,6 +187,11 @@ public void testAuthorityParsing() {
         uri = Uri.parse("http://localhost");
         assertEquals("localhost", uri.getHost());
         assertEquals(-1, uri.getPort());
+
+        uri = Uri.parse("http://a:a@example.com:a@example2.com/path");
+        assertEquals("a:a@example.com:a@example2.com", uri.getAuthority());
+        assertEquals("example2.com", uri.getHost());
+        assertEquals(-1, uri.getPort());
     }
 
     @SmallTest