fall back to ruby-hmac when openssl refuses to sha256

Gemfile

@@ -8,5 +8,6 @@ gem 'mime-types', ">= 0"
 gem 'net-ssh', ">= 0"
 gem 'nokogiri', ">= 0"
 gem 'rspec', '>= 0'
+gem 'ruby-hmac', '>= 0'
 gem 'shindo', '>= 0.1.5'
 gem 'builder', '>= 0'

Gemfile.lock

@@ -20,9 +20,11 @@ specs:
     version: 1.4.2
 - rspec: 
     version: 1.3.0
+- ruby-hmac: 
+    version: 0.4.0
 - shindo: 
     version: 0.1.5
-hash: 58a08d793d993ef27b7140767d8a94aa21a49a13
+hash: 12012795f07111bf764cef89d9ba91f521c54956
 sources: 
 - Rubygems: 
     uri: http://gemcutter.org
@@ -35,11 +37,15 @@ dependencies:
     version: ">= 0"
     group: 
     - :default
+  rake: 
+    version: ">= 0"
+    group: 
+    - :default
   rspec: 
     version: ">= 0"
     group: 
     - :default
-  rake: 
+  ruby-hmac: 
     version: ">= 0"
     group: 
     - :default
@@ -51,14 +57,14 @@ dependencies:
     version: ">= 0"
     group: 
     - :default
-  json: 
-    version: ">= 0"
-    group: 
-    - :default
   excon: 
     version: ">= 0.0.26"
     group: 
     - :default
+  json: 
+    version: ">= 0"
+    group: 
+    - :default
   builder: 
     version: ">= 0"
     group: 

fog.gemspec

@@ -48,6 +48,7 @@ Gem::Specification.new do |s|
   s.add_dependency('mime-types')
   s.add_dependency('net-ssh')
   s.add_dependency('nokogiri')
+  s.add_dependency('ruby-hmac')
 
   ## List your development dependencies here. Development dependencies are
   ## those that are only needed during development

lib/fog/hmac.rb

@@ -25,9 +25,22 @@ module Fog
     end
 
     def setup_sha256
-      @digest = OpenSSL::Digest::Digest.new('sha256')
-      @signer = lambda do |data|
-        OpenSSL::HMAC.digest(@digest, @key, data)
+      begin
+        @digest = OpenSSL::Digest::Digest.new('sha256')
+        @signer = lambda do |data|
+          OpenSSL::HMAC.digest(@digest, @key, data)
+        end
+      rescue RuntimeError => error
+        unless error.message == 'Unsupported digest algorithm (sha256).'
+          raise error
+        else
+          require 'hmac-sha2'
+          @hmac = ::HMAC::SHA256.new(@key)
+          @signer = lambda do |data|
+            @hmac.update(data)
+            @hmac.digest
+          end
+        end
       end
     end