Skip netrc with Authorization header, up/downcase.

The fix for the Netrc user/password overriding a user-set Authorization
header that was committed in #374 was case-sensitive and does not cover
users who pass `:authorization` or `"authorization"` as the header name.

Add @processed_headers_lowercase so that case-insensitive tests like
this are easier in the future. It would be better if
`Request#stringify_headers` normalized both Symbols and Strings.
https://github.com/rest-client/rest-client/issues/599

Also add a test for the case-insensitive behavior.

Fixes: #524, #550

lib/restclient/request.rb

@@ -146,6 +146,7 @@ module RestClient
       @log = args[:log]
       @max_redirects = args[:max_redirects] || 10
       @processed_headers = make_headers headers
+      @processed_headers_lowercase = Hash[@processed_headers.map {|k, v| [k.downcase, v]}]
       @args = args
 
       @before_execution_proc = args[:before_execution_proc]
@@ -368,6 +369,13 @@ module RestClient
     #   - headers from the payload object (e.g. Content-Type, Content-Lenth)
     #   - cookie headers from #make_cookie_header
     #
+    # BUG: stringify_headers does not alter the capitalization of headers that
+    # are passed as strings, it only normalizes those passed as symbols. This
+    # behavior will probably remain for a while for compatibility, but it means
+    # that the warnings that attempt to detect accidental header overrides may
+    # not always work.
+    # https://github.com/rest-client/rest-client/issues/599
+    #
     # @param [Hash] user_headers User-provided headers to include
     #
     # @return [Hash<String, String>] A hash of HTTP headers => values
@@ -536,6 +544,12 @@ module RestClient
     end
 
     # Return a hash of headers whose keys are capitalized strings
+    #
+    # BUG: stringify_headers does not fix the capitalization of headers that
+    # are already Strings. Leaving this behavior as is for now for
+    # backwards compatibility.
+    # https://github.com/rest-client/rest-client/issues/599
+    #
     def stringify_headers headers
       headers.inject({}) do |result, (key, value)|
         if key.is_a? Symbol
@@ -761,7 +775,9 @@ module RestClient
     end
 
     def setup_credentials(req)
-      req.basic_auth(user, password) if user && !headers.has_key?("Authorization")
+      if user && !@processed_headers_lowercase.include?('authorization')
+        req.basic_auth(user, password)
+      end
     end
 
     def fetch_body_to_tempfile(http_response)

spec/unit/request_spec.rb

@@ -448,12 +448,13 @@ describe RestClient::Request, :include_helpers do
     end
 
     it "does not attempt to send credentials if Authorization header is set" do
-      @request.headers['Authorization'] = 'Token abc123'
-      allow(@request).to receive(:user).and_return('joe')
-      allow(@request).to receive(:password).and_return('mypass')
-      req = double("request")
-      expect(req).not_to receive(:basic_auth)
-      @request.send(:setup_credentials, req)
+      ['Authorization', 'authorization', 'auTHORization', :authorization].each do |authorization|
+        headers = {authorization => 'Token abc123'}
+        request = RestClient::Request.new(method: :get, url: 'http://some/resource', headers: headers, user: 'joe', password: 'mypass')
+        req = double("net::http request")
+        expect(req).not_to receive(:basic_auth)
+        request.send(:setup_credentials, req)
+      end
     end
   end