[http_authorization] Check for nil value when decode based64 value

Performing a match on a nil value results in an exception being thrown
and bypassing the entire authorization validation process.

Author: tkan145

CHANGELOG.md

@@ -55,6 +55,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Fixed APIcast send request through proxy server even when `NO_PROXY` is used [PR #1478](https://github.com/3scale/APIcast/pull/1478) [THREESCALE-11128](https://issues.redhat.com/browse/THREESCALE-11128)
 
+- Fixed APIcast panic when parsing invalid base64 encoded value [PR #1505](https://github.com/3scale/APIcast/pull/1505) [THEESCALE-11435](https://issues.redhat.com/browse/THREESCALE-11435)
+
 ### Added
 
 - Detect number of CPU shares when running on Cgroups V2 [PR #1410](https://github.com/3scale/apicast/pull/1410) [THREESCALE-10167](https://issues.redhat.com/browse/THREESCALE-10167)

gateway/src/resty/http_authorization.lua

@@ -9,8 +9,11 @@ local _M = {
 local mt = { __index = _M }
 
 function _M.parsers.Basic(param)
+  local userid, password
   local user_pass = ngx.decode_base64(param)
-  local userid, password = match(user_pass, '^(.*):(.*)$')
+  if user_pass then
+    userid, password = match(user_pass, '^(.*):(.*)$')
+  end
 
   return {
     userid = userid,

spec/resty/http_authorization_spec.lua

@@ -60,6 +60,13 @@ describe('HTTP Authorization', function()
         assert.equal('', auth.userid)
         assert.equal('pass', auth.password)
       end)
+
+      it('do not panic with invalid header', function()
+        local auth = authorization.new('Basic !123!')
+
+        assert.equal(nil, auth.userid)
+        assert.equal(nil, auth.password)
+      end)
     end)
 
     describe('Bearer', function()