So basically openssl_malloc() wasn't always malloc()-ing -- it would sometimes return a previously malloc()-ed aread that was never (actually) freed.
This rendered OpenBSD's hardened malloc() useless: you can configure OBSD to always initialize malloc-ed areas. If OpenSSL had used malloc() instead of openssl_malloc, even with the wrong (large and unchecked) size, the buffer would not have contained previous values, as it would have already been initialized to 0x0D. Instead, they'd return previous malloc()-ed -- and never actually free()-d -- buffers, that contained the old data. Since malloc() was not called for them, there was never a chance to re-initialize their contents.
This can trivially (if just as dumbly!) be implemented in Go. It's equally pointless (the reasons they did that were 100% historical), but possible. And -- assuming they'd have done away with the whole openssl_dothis() and openssl_dothat() crap -- heartbleed would have been trivially prevented in C by just sanely implementing malloc.
> (We eventually plan on supporting this case, just haven't gotten there yet.)
I'm really (and not maliciously!) curious about how this will be done :). You guys are doing some amazing work with Rust! Good luck!