KABUL, Afghanistan — Dozens of people killed in a brazen Taliban attack on a military base were members of Afghanistan’s intelligence agency, officials said Tuesday, in a severe blow to the government that already has lost control of nearly half of the country to the insurgents. At least 45 people were killed and as many as 70 were wounded by a suicide bomber who drove an armored Humvee packed with explosives at the base in eastern Maidan Wardak province on Monday, the officials said. There were fears the death toll from the daytime assault could increase.