redmine: Fix openid

For some reason, redmine:3.4 ships with ancient (2014) ruby-openid,
which is no longer compatible with the way how ruby handles HMAC.

Change-Id: I60f6f1ede059accf6b29891abcfe3b2529744e8a

redmine/Dockerfile

@@ -7,3 +7,6 @@ RUN	apt-get update && \
 		mscgen \
 		patch && \
 	apt-get clean
+
+ADD	hmac.diff /tmp/hmac.diff
+RUN	cd / && patch -p0 < /tmp/hmac.diff

redmine/hmac.diff

@@ -0,0 +1,21 @@
+--- usr/local/bundle/gems/ruby-openid-2.3.0/lib/openid/cryptutil.rb.old	2018-10-07 08:53:33.612724431 +0000
++++ usr/local/bundle/gems/ruby-openid-2.3.0/lib/openid/cryptutil.rb	2018-10-07 08:54:03.016525355 +0000
+@@ -39,6 +39,6 @@
+     def CryptUtil.hmac_sha1(key, text)
+-      if Digest.const_defined? :HMAC
+-        Digest::HMAC.new(key,Digest::SHA1).update(text).digest
++      if defined? OpenSSL
++        OpenSSL::HMAC.digest(OpenSSL::Digest::SHA1.new, key, text)
+       else
+         return HMAC::SHA1.digest(key, text)
+       end
+@@ -50,7 +50,7 @@
+ 
+     def CryptUtil.hmac_sha256(key, text)
+-      if Digest.const_defined? :HMAC
+-        Digest::HMAC.new(key,Digest::SHA256).update(text).digest
++      if defined? OpenSSL
++        OpenSSL::HMAC.digest(OpenSSL::Digest::SHA256.new, key, text)
+       else
+         return HMAC::SHA256.digest(key, text)
+       end