This check isn't necessary (see comment on #7801), but it took at
least two smart people a little while to see why it wasn't necessary,
so let's have it in to make the code more readable.
We need a weak RNG in a couple of places where the strong RNG is
both needless and too slow. We had been using the weak RNG from our
platform's libc implementation, but that was problematic (because
many platforms have exceptionally horrible weak RNGs -- like, ones
that only return values between 0 and SHORT_MAX) and because we were
using it in a way that was wrong for LCG-based weak RNGs. (We were
counting on the low bits of the LCG output to be as random as the
high ones, which isn't true.)
This patch adds a separate type for a weak RNG, adds an LCG
implementation for it, and uses that exclusively where we had been
using the platform weak RNG.
Right now, all our curve25519 backends ignore the high bit of the
public key. But possibly, others could treat the high bit of the
public key as encoding out-of-bounds values, or as something to be
preserved. This could be used to distinguish clients with different
backends, at the cost of killing a circuit.
As a workaround, let's just clear the high bit of each public key
indiscriminately before we use it. Fix for bug 8121, reported by
rransom. Bugfix on 0.2.4.8-alpha.
Authorities don't set is_possible_guard on node_t, so they were
never deciding that they could build enough paths. This is a quick
and dirty fix.
Bug not in any released version of Tor
These seem to have gotten conflicted out of existence while mike was
working on path bias stuff.
Thanks to sysrqb for collecting these in a handy patch.
The fix is to move the two functions to format/parse base64
curve25519 public keys into a new "crypto_format.c" file. I could
have put them in crypto.c, but that's a big file worth splitting
anyway.
Fixes bug 8153; bugfix on 0.2.4.8-alpha where I did the fix for 7869.
Now we can specify to skip bridges that wouldn't be able to answer the
type of dir fetch we're launching.
It's still the responsibility of the rest of the code to prevent us from
launching a given dir fetch if we have no bridges that could handle it.
Now as we move into a future where most bridges can handle microdescs
we will generally find ourselves using them, rather than holding back
just because one of our bridges doesn't use them.
