Fix unnecessary file updates when HTTP source lacks checksum headers

lib/puppet/file_serving/http_metadata.rb

@@ -13,8 +13,6 @@ def initialize(http_response, path = '/dev/null')
 
     # hash available checksums for eventual collection
     @checksums = {}
-    # use a default mtime in case there is no usable HTTP header
-    @checksums[:mtime] = "{mtime}#{Time.now}"
 
     # RFC-1864, deprecated in HTTP/1.1 due to partial responses
     checksum = http_response['content-md5']
@@ -82,5 +80,8 @@ def collect
       @checksum = @checksums[type]
       break if @checksum
     end
+
+    # If no checksum was found in headers, leave checksum as nil
+    # The HTTP indirector will need to fetch content to compute a checksum
   end
 end

lib/puppet/indirector/file_metadata/http.rb

@@ -17,17 +17,21 @@ def find(request)
     client = Puppet.runtime[:http]
     head = client.head(uri, options: { include_system_store: true })
 
-    return create_httpmetadata(head, checksum_type) if head.success?
+    metadata = create_httpmetadata(head, checksum_type)
+    return metadata if metadata.checksum
 
-    case head.code
-    when 403, 405
-      # AMZ presigned URL and puppetserver may return 403
-      # instead of 405. Fallback to partial get
-      get = partial_get(client, uri)
-      return create_httpmetadata(get, checksum_type) if get.success?
-    end
+    # If no checksum headers were available, fetch the content to compute a checksum
+    get = client.get(uri, options: { include_system_store: true })
+    return nil unless get.success?
 
-    nil
+    # Compute checksum from the content
+    content = get.body
+    checksum_type ||= Puppet[:digest_algorithm].to_sym
+    checksum = "{#{checksum_type}}" + Digest.const_get(checksum_type.to_s.upcase).hexdigest(content)
+
+    metadata.checksum = checksum
+    metadata.checksum_type = checksum_type
+    metadata
   end
 
   def search(request)

spec/unit/indirector/file_metadata/http_spec.rb

@@ -29,16 +29,18 @@
   end
 
   context "when finding" do
-    it "returns http file metadata" do
+    it "returns http file metadata and fetches content to compute checksum when no headers available" do
       stub_request(:head, key)
         .to_return(status: 200, headers: DEFAULT_HEADERS)
+      stub_request(:get, key)
+        .to_return(status: 200, body: "test content")
 
       result = model.indirection.find(key)
       expect(result.ftype).to eq('file')
       expect(result.path).to eq('/dev/null')
       expect(result.relative_path).to be_nil
       expect(result.destination).to be_nil
-      expect(result.checksum).to match(%r{mtime})
+      expect(result.checksum).to match(%r{sha256})
       expect(result.owner).to be_nil
       expect(result.group).to be_nil
       expect(result.mode).to be_nil