Fix header regex.

The previous regex would match any number of instances of any of the
supported SHA formats, e.g. SHA111. Instead of matching any number, we
want to match optionally one.

Also added some tests that this rejects invalid digest formats.

Author: packrat386

lib/api_auth/base.rb

@@ -69,7 +69,7 @@ def generate_secret_key
 
     private
 
-    AUTH_HEADER_PATTERN = /APIAuth(?:-HMAC-(MD[245]|SHA(?:1|224|256|384|512)*))? ([^:]+):(.+)$/
+    AUTH_HEADER_PATTERN = /APIAuth(?:-HMAC-(MD[245]|SHA(?:1|224|256|384|512)?))? ([^:]+):(.+)$/
 
     def request_too_old?(headers)
       # 900 seconds is 15 minutes

spec/api_auth_spec.rb

@@ -127,16 +127,32 @@ def hmac(secret_key, request, canonical_string = nil, digest = 'sha1')
                                         )
         canonical_string = ApiAuth::Headers.new(new_request).canonical_string
         signature = hmac('123', new_request, canonical_string, 'sha256')
-        new_request['Authorization'] = "APIAuth-HMAC-SHA256 1044:#{signature}"
+        new_request['Authorization'] = "APIAuth-HMAC-#{digest} 1044:#{signature}"
         new_request
       end
 
-      it 'validates for sha256 digest' do
-        expect(ApiAuth.authentic?(request, '123', :digest => 'sha256')).to eq true
+      context 'valid request digest' do
+        let(:digest) { 'SHA256' }
+
+        context 'matching client digest' do
+          it 'validates matching digest' do
+            expect(ApiAuth.authentic?(request, '123', :digest => 'sha256')).to eq true
+          end
+        end
+
+        context 'different client digest' do
+          it 'raises an exception' do
+            expect { ApiAuth.authentic?(request, '123', :digest => 'sha512') }.to raise_error(ApiAuth::InvalidRequestDigest)
+          end
+        end
       end
 
-      it 'validates exception with wrong client digest' do
-        expect { ApiAuth.authentic?(request, '123', :digest => 'sha512') }.to raise_error(ApiAuth::InvalidRequestDigest)
+      context 'invalid request digest' do
+        let(:digest) { 'SHA111' }
+
+        it 'fails validation' do
+          expect(ApiAuth.authentic?(request, '123', :digest => 'sha111')).to eq false
+        end
       end
     end
   end