Add SASL GSSAPI (Kerberos) support

Author: grisha

README.md

@@ -117,7 +117,17 @@ Connecting with a specific Hive version (0.12) and using the `:http` transport:
       connection.fetch('SHOW TABLES')
     end
 
-We have not tested the SASL connection, as we don't run SASL; pull requests and testing are welcomed.
+Connecting with SASL and Kerberos v5:
+
+    RBHive.tcli_connect('hive.hadoop.forward.co.uk', 10_000, {
+      :transport => :sasl,
+      :sasl_params => {
+        :mechanism => 'GSSAPI',
+        :remote_host => 'example.com',
+        :remote_principal => 'hive/example.com@EXAMPLE.COM'
+    ) do |connection|
+      connection.fetch("show tables")
+    end
 
 #### Hiveserver2 protocol versions
 

lib/rbhive/t_c_l_i_connection.rb

@@ -375,7 +375,9 @@ def method_missing(meth, *args)
     private
 
     def prepare_open_session(client_protocol)
-      req = ::Hive2::Thrift::TOpenSessionReq.new( @options[:sasl_params].nil? ? [] : @options[:sasl_params] )
+      req = ::Hive2::Thrift::TOpenSessionReq.new( @options[:sasl_params].nil? ? [] : {
+                                                    :username => @options[:sasl_params][:username],
+                                                    :password => @options[:sasl_params][:password]})
       req.client_protocol = client_protocol
       req
     end

lib/thrift/sasl_client_transport.rb

@@ -1,10 +1,9 @@
-module Thrift
-  class SaslClientTransport < BufferedTransport
-    attr_reader :challenge
+require 'gssapi'
 
+module Thrift
+  class SaslClientTransport < FramedTransport
     STATUS_BYTES = 1
     PAYLOAD_LENGTH_BYTES = 4
-    AUTH_MECHANISM = 'PLAIN'
     NEGOTIATION_STATUS = {
       START:    0x01,
       OK:       0x02,
@@ -15,76 +14,122 @@ class SaslClientTransport < BufferedTransport
 
     def initialize(transport, sasl_params={})
       super(transport)
-      @challenge = nil
+      @sasl_complete = nil
       @sasl_username = sasl_params.fetch(:username, 'anonymous')
       @sasl_password = sasl_params.fetch(:password, 'anonymous')
+      @sasl_mechanism = sasl_params.fetch(:mechanism, 'PLAIN')
+
+      unless ['PLAIN', 'GSSAPI'].include? @sasl_mechanism
+        raise "Unknown SASL mechanism: #{@sasl_mechanism}"
+      end
+
+      if @sasl_mechanism == 'GSSAPI'
+        @sasl_remote_principal = sasl_params[:remote_principal]
+        @sasl_remote_host = sasl_params[:remote_host]
+        @gsscli = GSSAPI::Simple.new(@sasl_remote_host, @sasl_remote_principal)
+      end
     end
 
     def read(sz)
-      len, = @transport.read(PAYLOAD_LENGTH_BYTES).unpack('l>') if @rbuf.nil?
-      sz = len if len && sz > len
-      @index += sz
-      ret = @rbuf.slice(@index - sz, sz) || Bytes.empty_byte_buffer
-      if ret.length == 0
-        @rbuf = @transport.read(len) rescue Bytes.empty_byte_buffer
-        @index = sz
-        ret = @rbuf.slice(0, sz) || Bytes.empty_byte_buffer
-      end
-      ret
+      handshake! unless @sasl_complete
+      super(sz)
     end
 
     def read_byte
-      reset_buffer! if @index >= @rbuf.size
-      @index += 1
-      Bytes.get_string_byte(@rbuf, @index - 1)
+      handshake! unless @sasl_complete
+      super
     end
 
-    def read_into_buffer(buffer, size)
-      i = 0
-      while i < size
-        reset_buffer! if @index >= @rbuf.size
-        byte = Bytes.get_string_byte(@rbuf, @index)
-        Bytes.set_string_byte(buffer, i, byte)
-        @index += 1
-        i += 1
-      end
-      i
+    def read_into_buffer(buf, size)
+      handshake! unless @sasl_complete
+      super(buf, size)
     end
 
     def write(buf)
-      initiate_hand_shake if @challenge.nil?
-      header = [buf.length].pack('l>')
-      @wbuf << (header + Bytes.force_binary_encoding(buf))
+      handshake! unless @sasl_complete
+      super(buf)
     end
 
-    protected
+    def flush
+      handshake! unless @sasl_complete
+      super
+    end
 
-    def initiate_hand_shake
-      header = [NEGOTIATION_STATUS[:START], AUTH_MECHANISM.length].pack('cl>')
-      @transport.write header + AUTH_MECHANISM
-      message = "[#{AUTH_MECHANISM}]\u0000#{@sasl_username}\u0000#{@sasl_password}"
-      header = [NEGOTIATION_STATUS[:OK], message.length].pack('cl>')
-      @transport.write header + message
-      status, len = @transport.read(STATUS_BYTES + PAYLOAD_LENGTH_BYTES).unpack('cl>')
+    private
+
+    def handshake!
+      case @sasl_mechanism
+      when 'PLAIN'
+        handshake_plain!
+      when 'GSSAPI'
+        handshake_gssapi!
+      end
+    end
+
+    def handshake_plain!
+      token = "[#{@sasl_mechanism}]\u0000#{@sasl_username}\u0000#{@sasl_password}"
+      write_handshake_message(NEGOTIATION_STATUS[:START], @sasl_mechanism)
+      write_handshake_message(NEGOTIATION_STATUS[:OK], token)
+
+      status, msg = read_handshake_message
       case status
-      when NEGOTIATION_STATUS[:BAD], NEGOTIATION_STATUS[:ERROR]
-        raise @transport.to_io.read(len)
       when NEGOTIATION_STATUS[:COMPLETE]
-        @challenge = @transport.to_io.read len
+        @sasl_complete = true
       when NEGOTIATION_STATUS[:OK]
         raise "Failed to complete challenge exchange: only NONE supported currently"
       end
     end
 
-    private
+    def handshake_gssapi!
+      token = @gsscli.init_context
+      write_handshake_message(NEGOTIATION_STATUS[:START], @sasl_mechanism)
+      write_handshake_message(NEGOTIATION_STATUS[:OK], token)
+
+      status, msg = read_handshake_message
+      case status
+      when NEGOTIATION_STATUS[:COMPLETE]
+        raise "Unexpected COMPLETE from server"
+      when NEGOTIATION_STATUS[:OK]
+        unless @gsscli.init_context(msg)
+          raise "GSSAPI: challenge provided by server could not be verified"
+        end
+
+        write_handshake_message(NEGOTIATION_STATUS[:OK], "")
+
+        status, msg = read_handshake_message
+        case status
+        when NEGOTIATION_STATUS[:COMPLETE]
+          raise "Unexpected COMPLETE from server"
+        when NEGOTIATION_STATUS[:OK]
+          unwrapped = @gsscli.unwrap_message(msg)
+          rewrapped = @gsscli.wrap_message(unwrapped)
+
+          write_handshake_message(NEGOTIATION_STATUS[:COMPLETE], rewrapped)
 
-    def reset_buffer!
-      len, = @transport.read(PAYLOAD_LENGTH_BYTES).unpack('l>')
-      @rbuf = @transport.read(len)
-      while @rbuf.size < len
-        @rbuf << @transport.read(len - @rbuf.size)
+          status, msg = read_handshake_message
+          case status
+          when NEGOTIATION_STATUS[:COMPLETE]
+            @sasl_complete = true
+          when NEGOTIATION_STATUS[:OK]
+            raise "Failed to complete GSS challenge exchange"
+          end
+        end
       end
-      @index = 0
+    end
+
+    def read_handshake_message
+      status, len = @transport.read(STATUS_BYTES + PAYLOAD_LENGTH_BYTES).unpack('cl>')
+      body = @transport.to_io.read(len)
+      if [NEGOTIATION_STATUS[:BAD], NEGOTIATION_STATUS[:ERROR]].include?(status)
+        raise "Exception from server: #{body}"
+      end
+
+      [status, body]
+    end
+
+    def write_handshake_message(status, message)
+      header = [status, message.length].pack('cl>')
+      @transport.write(header + message)
     end
   end
 
@@ -93,5 +138,4 @@ def get_transport(transport)
       return SaslClientTransport.new(transport)
     end
   end
-
 end

rbhive.gemspec

@@ -19,6 +19,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.add_dependency('thrift', '~> 0.9')
+  spec.add_dependency('gssapi', '~> 1.2')
   spec.add_dependency('json')
 
   spec.add_development_dependency 'rake'