First, from Wikipedia, a bit on Boss (and a 2011 Boss apology here):
Hugo Boss started his clothing company in 1924 in Metzingen, a small town south of Stuttgart, where it is still based. Due to the economic climate in Germany at the time, Boss was forced into bankruptcy. In 1931, he reached an agreement with his creditors, leaving him with six sewing machines to start again.
The same year 1931, he became a member of the National Socialist (Nazi) party and a sponsoring member ("Förderndes Mitglied") of the Schutzstaffel (SS) and his economic situation improved with their help. He later stated himself that he had joined the party because of their promise to end unemployment and because he felt "temporarily" withdrawn from the Lutheran church.
He joined the German Labour Front in 1936, the Reich Air Protection Association in 1939, and the National Socialist People's Welfare in 1941. His sales increased from 38,260 RM in 1932 to over 3,300,000 RM in 1941, while his profits increased in the same period from 5,000 RM to 241,000 RM. Though he claimed in a 1934/1935 advertising that he had been a "supplier for National Socialist uniforms since 1924", such supplies are probable since 1928/1929 and certain since 1934, when he became an Reichszeugmeisterei-licensed (official) supplier of uniforms to the Sturmabteilung, Schutzstaffel, Hitler Youth, National Socialist Motor Corps, and other party organizations.
To meet demand in later years of the war, Boss used about 30 to 40 prisoners of war and about 150 forced (i.e. slave) labourers, from the Baltic States, Belgium, France, Italy, Austria, Poland, Czechoslovakia, and the Soviet Union. According to German historian Henning Kober, the company managers were "avowed Nazis", "the Boss were all great admirers of Adolf Hitler", and Hugo Boss himself had in 1945 in his apartment a photograph of himself with Hitler taken in the latter's Obersalzberg retreat.