1 files changed, 76 insertions, 0 deletions
diff --git a/lib/uri/generic.rb b/lib/uri/generic.rb
index 0435fd25ce..1d8963af4d 100644
--- a/lib/uri/generic.rb
+++ b/lib/uri/generic.rb
@@ -1596,5 +1596,81 @@ module URI
 
       return oth, self
     end
+
+    # returns a proxy URI.
+    # The proxy URI is obtained from environment variables such as http_proxy,
+    # ftp_proxy, no_proxy, etc.
+    # If there is no proper proxy, nil is returned.
+    #
+    # Note that capitalized variables (HTTP_PROXY, FTP_PROXY, NO_PROXY, etc.)
+    # are examined too.
+    #
+    # But http_proxy and HTTP_PROXY is treated specially under CGI environment.
+    # It's because HTTP_PROXY may be set by Proxy: header.
+    # So HTTP_PROXY is not used.
+    # http_proxy is not used too if the variable is case insensitive.
+    # CGI_HTTP_PROXY can be used instead.
+    def find_proxy
+      name = self.scheme.downcase + '_proxy'
+      proxy_uri = nil
+      if name == 'http_proxy' && ENV.include?('REQUEST_METHOD') # CGI?
+        # HTTP_PROXY conflicts with *_proxy for proxy settings and
+        # HTTP_* for header information in CGI.
+        # So it should be careful to use it.
+        pairs = ENV.reject {|k, v| /\Ahttp_proxy\z/i !~ k }
+        case pairs.length
+        when 0 # no proxy setting anyway.
+          proxy_uri = nil
+        when 1
+          k, _ = pairs.shift
+          if k == 'http_proxy' && ENV[k.upcase] == nil
+            # http_proxy is safe to use because ENV is case sensitive.
+            proxy_uri = ENV[name]
+          else
+            proxy_uri = nil
+          end
+        else # http_proxy is safe to use because ENV is case sensitive.
+          proxy_uri = ENV.to_hash[name]
+        end
+        if !proxy_uri
+          # Use CGI_HTTP_PROXY.  cf. libwww-perl.
+          proxy_uri = ENV["CGI_#{name.upcase}"]
+        end
+      elsif name == 'http_proxy'
+        unless proxy_uri = ENV[name]
+          if proxy_uri = ENV[name.upcase]
+            warn 'The environment variable HTTP_PROXY is discouraged.  Use http_proxy.'
+          end
+        end
+      else
+        proxy_uri = ENV[name] || ENV[name.upcase]
+      end
+
+      if proxy_uri && self.hostname
+        require 'socket'
+        begin
+          addr = IPSocket.getaddress(self.hostname)
+          proxy_uri = nil if /\A127\.|\A::1\z/ =~ addr
+        rescue SocketError
+        end
+      end
+
+      if proxy_uri
+        proxy_uri = URI.parse(proxy_uri)
+        name = 'no_proxy'
+        if no_proxy = ENV[name] || ENV[name.upcase]
+          no_proxy.scan(/([^:,]*)(?::(\d+))?/) {|host, port|
+            if /(\A|\.)#{Regexp.quote host}\z/i =~ self.host &&
+               (!port || self.port == port.to_i)
+              proxy_uri = nil
+              break
+            end
+          }
+        end
+        proxy_uri
+      else
+        nil
+      end
+    end
   end
 end