We need to make sure that the worst thing that a weird consensus param
can do to us is to break our Tor (and only if the other Tors are
reliably broken in the same way) so that the majority of directory
authorities can't pull any attacks that are worse than the DoS that
they can trigger by simply shutting down.
One of these worse things was the cbtnummodes parameter, which could
lead to heap corruption on some systems if the value was sufficiently
large.
This commit fixes this particular issue and also introduces sanity
checking for all consensus parameters.
In its zeal to keep me from saying memset(x, '0', sizeof(x)), Coverity
disallows memset(x, 48, sizeof(x)). Fine. I'll choose a different
magic number, see if I care!
This patch introduces a new type called document_signature_t to represent the
signature of a consensus document. Now, each consensus document can have up
to one document signature per voter per digest algorithm. Also, each
detached-signatures document can have up to one signature per <voter,
algorithm, flavor>.
Found by coverity
test_mem_op_hex was leaking memory, which showed up in a few
tests.
Also, the dir_param test had a memleak of its own.
Found by Coverity
