[geary: 1/2] Fix 100% CPU usage on mismatch utf escapes in rfc822 string

[Michael Gratton <mjog src gnome org>]

commit 15e0d18dd66e5387361e354d2b6e0a0876b3ddbb
Author: Joe Barnett <jbarnett tribedynamics com>
Date:   Tue Aug 6 07:30:28 2019 -0700

    Fix 100% CPU usage on mismatch utf escapes in rfc822 string
    
    Since we're adding 2 to the index_of return value, we can't
    compare to -1.
    
    See issue #504

 src/engine/rfc822/rfc822-mailbox-address.vala | 2 +-
 test/engine/rfc822-mailbox-address-test.vala  | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/src/engine/rfc822/rfc822-mailbox-address.vala b/src/engine/rfc822/rfc822-mailbox-address.vala
index 4ab8d21e..73803f19 100644
--- a/src/engine/rfc822/rfc822-mailbox-address.vala
+++ b/src/engine/rfc822/rfc822-mailbox-address.vala
@@ -131,7 +131,7 @@ public class Geary.RFC822.MailboxAddress :
         while ((start = text.index_of("=?", offset)) != -1) {
             // Find the closing marker.
             int end = text.index_of("?=", start + 2) + 2;
-            if (end == -1) {
+            if (end <= 1) {
                 end = text.length;
             }
 
diff --git a/test/engine/rfc822-mailbox-address-test.vala b/test/engine/rfc822-mailbox-address-test.vala
index b3f7547d..c04d47e0 100644
--- a/test/engine/rfc822-mailbox-address-test.vala
+++ b/test/engine/rfc822-mailbox-address-test.vala
@@ -147,6 +147,11 @@ class Geary.RFC822.MailboxAddressTest : TestCase {
             addr = new 
MailboxAddress.from_rfc822_string("\"=?utf-8?Q?=42=45=47=49=4E=20=2F=20=28=7C=29=7C=3C=7C=3E=7C=40=7C=2C=7C=3B=7C=3A=7C=5C=7C=22=7C=2F=7C=5B=7C=5D=7C=3F=7C=2E=7C=3D=20=2F=20=00=20=50=41=53=53=45=44=20=4E=55=4C=4C=20=42=59=54=45=20=2F=20=0D=0A=20=50=41=53=53=45=44=20=43=52=4C=46=20=2F=20?==?utf-8?b?RU5E=?=\"");
             assert(addr.name == null);
             assert(addr.address == "BEGIN / (|)|<|>|@|,|;|:|\\|\"|/|[|]|?|.|= / ? PASSED NULL BYTE / \r\n 
PASSED CRLF / END");
+
+            addr = new 
MailboxAddress.from_rfc822_string("=?UTF-8?Q?=22Firstname_=22=C2=AF\\=5F=28=E3=83=84=29=5F/=C2=AF=22_Lastname_via?==?UTF-8?Q?_Vendor=22_<system
 vendor com>?=");
+            assert(addr.name == "Firstname ¯_(ツ)_/¯ Lastname via=?UTF-8?Q?_Vendor=22_");
+            assert(addr.mailbox == "system");
+            assert(addr.domain == "vendor.com");
         } catch (Error err) {
             assert_not_reached();
         }