tls: use SHA1 for sessionIdContext

FIPS 140-2 disallows use of MD5, which is used to derive the
default sessionIdContext for tls.createServer().
PR-URL: #3866
Reviewed-By: Fedor Indutny <fedor@indutny.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: stefanmb

doc/api/tls.markdown

@@ -841,9 +841,9 @@ automatically set as a listener for the [secureConnection][] event. The
  NOTE: Automatically shared between `cluster` module workers.
 
 -`sessionIdContext`: A string containing an opaque identifier for session
- resumption. If `requestCert` is `true`, the default is MD5 hash value
- generated from command-line. (In FIPS mode a truncated SHA1 hash is
-used instead.) Otherwise, the default is not provided.
+ resumption. If `requestCert` is `true`, the default is a 128 bit
+truncated SHA1 hash value generated from command-line. Otherwise,
+ the default is not provided.
 
 -`secureProtocol`: The SSL method to use, e.g. `SSLv3_method` to force
  SSL version 3. The possible values depend on your installation of

lib/_tls_wrap.js

@@ -14,21 +14,6 @@ const Timer = process.binding('timer_wrap').Timer;
 consttls_wrap=process.binding('tls_wrap');
 constTCP=process.binding('tcp_wrap').TCP;
 constPipe=process.binding('pipe_wrap').Pipe;
-constdefaultSessionIdContext=getDefaultSessionIdContext();
-
-functiongetDefaultSessionIdContext(){
-vardefaultText=process.argv.join(' ');
-/* SSL_MAX_SID_CTX_LENGTH is 128 bits */
-if(process.config.variables.openssl_fips){
-returncrypto.createHash('sha1')
-.update(defaultText)
-.digest('hex').slice(0,32);
-}else{
-returncrypto.createHash('md5')
-.update(defaultText)
-.digest('hex');
-}
-}
 
 functiononhandshakestart(){
 debug('onhandshakestart');
@@ -908,7 +893,10 @@ Server.prototype.setOptions = function(options) {
 if(options.sessionIdContext){
 this.sessionIdContext=options.sessionIdContext;
 }else{
-this.sessionIdContext=defaultSessionIdContext;
+this.sessionIdContext=crypto.createHash('sha1')
+.update(process.argv.join(' '))
+.digest('hex')
+.slice(0,32);
 }
 };