I was reading about the Winter War and I can't help but wonder whether it was a proxy war for Germany to test and attack the Soviet Union (much like the Spanish Civil War in the years prior) prior to their invasion. The Winter War was fought very early in the war, while both nations were officially at peace, and I'm sure that Finland fit somewhere in the Nazi's racial hierarchy. I bet they wouldn't want it to come under the control of what they called "Jewish Bolshevism".
Is there any evidence that Germany supported Finland in their war with the USSR?
Absolutely not.
Germany was at the time dependent on Soviet supplies of raw materials and fully focused on their coming offensive against France, the Low Countries and the British Expeditionary Force in France.
Finnish orders for German arms, including 20mm Flak30 automatic AA guns were stalled or impounded on Soviet request.
Before the war, the Finns requested to know what the German position was on the Soviet demands, and got a diplomatic reply that the Germans did not have one - diplomatic speech for "you are on your own!"
Italian, Belgian and Hungarian requests to transport arms to Finland on the German rail network to the Baltic Sea shore were denied. The Hungarian volunteer battalion had to take the long route through Yugoslavia, Italy and France and then sail to Finland, arriving only a week before the end of the war and were still training skiing and winter warfare when the peace came. 94 500 Italian rifles with ammunition and 35 Italian fighter planes along wth 20 37mm Bofors AT guns made in Hungary were impounded in Germany during the war, and only released to Finland after it.
On the 26th of February 1940, the Finns officially requested Swedish military aid since the Soviets ahd reached their 3rd (and last) line of defence on the Karelian Isthmus. Sweden denied the request, but made plans to send two infantry divisions of 'volunteers'. The German military attaché von Uthmann then met with the Swedish foreign minister Günther and told him that Germany would view such a move "as extremely hostile towards Germany" - in diplomatic and unofficial ways the Germans were threatening to declare war on Sweden if aid to Finland was not limited.
In short, the Germans did all they could - diplomatically and directly to prevent aid and military supplies from reaching Finland and to isolate Finland, in accordance with the Molotov-Ribbentrop pact.
It was not until after the Winter War and after their success in the west that the Germans started seeing the Finns as a potential ally in their upcoming war against the Soviets and released impounded arms and equipment and started selling them captured arms at discount prices (this included French AT guns and fighters, Polish AA guns and AT guns and much more).
So I think we can safely say that Germany's actions during the Winter War allows us to say it was not a proxy war between Germany and the Soviet Union. It was a war between the Soviet Union and Finland, with the Finns getting Swedish, Danish, Norwegian, Belgian, French, US, British, Hungarian and Italian help, with the Germans doing what it could to prevent the latter.