The former IT administrator turned whistle blower told a German newspaper:
Believe me, the CIA does have its sources inside Russian intelligence. If I was a Russian spy, the U.S. would know. And it would be on the front page of every newspaper
The accusation has always rested on inference, not publicly available evidence. The inference is that if Snowden arrived in Moscow with the NSA materials he stole, then surely, the Russian intelligence took possession of what he had. But Snowden says he destroyed his hard drives before he traveled to Moscow, and the US government has never asserted that the Russians received the material from him.
The theory of writer Edward Epstein that Snowden acted on behalf of a foreign power depended on the claim that there were no records of where Snowden stayed for 10 days in Hong Kongin June 2013, before he traveled to Moscow.
But then Snowden’s Hong Kong lawyers obtained his hotel records, and Glenn Greenwald posted them at The Intercept. As recipient of Snowden’s leak, Greenwald is, of course, too close to the story to be the final arbiter. But Charlie Savage of the New York Times who debated the issue with Epstein in the New York Review of Books, says the evidence supports Snowden. Epstein seems to have backed off his theory.
Based on the available evidence, I think Snowden’s denial is credible