In protover.c, the `expand_protocol_list()` function expands a `smartlist_t` of
`proto_entry_t`s to their protocol name concatenated with each version number.
For example, given a `proto_entry_t` like so:
proto_entry_t *proto = tor_malloc(sizeof(proto_entry_t));
proto_range_t *range = tor_malloc_zero(sizeof(proto_range_t));
proto->name = tor_strdup("DoSaaaaaaaaaaaaaaaaaaaaaa[19KB]aaa");
proto->ranges = smartlist_new();
range->low = 1;
range->high = 65536;
smartlist_add(proto->ranges, range);
(Where `[19KB]` is roughly 19KB of `"a"` bytes.) This would expand in
`expand_protocol_list()` to a `smartlist_t` containing 65536 copies of the
string, e.g.:
"DoSaaaaaaaaaaaaaaaaaaaaaa[19KB]aaa=1"
"DoSaaaaaaaaaaaaaaaaaaaaaa[19KB]aaa=2"
[…]
"DoSaaaaaaaaaaaaaaaaaaaaaa[19KB]aaa=65535"
Thus constituting a potential resource exhaustion attack.
The Rust implementation is not subject to this attack, because it instead
expands the above string into a `HashMap<String, HashSet<u32>` prior to #24031,
and a `HashMap<UnvalidatedProtocol, ProtoSet>` after). Neither Rust version is
subject to this attack, because it only stores the `String` once per protocol.
(Although a related, but apparently of too minor impact to be usable, DoS bug
has been fixed in #24031. [0])
[0]: https://bugs.torproject.org/24031
* ADDS hard limit on protocol name lengths in protover.c and checks in
parse_single_entry() and expand_protocol_list().
* ADDS tests to ensure the bug is caught.
* FIXES#25517: https://bugs.torproject.org/25517
Apparently, even though I had tested on OpenSSL 1.1.1 with
no-deprecated, OpenSSL 1.1.0 is different enough that I should have
tested with that as well.
Fixes bug 26156; bugfix on 0.3.4.1-alpha where we first declared
support for this configuration.
The new gcov sometimes emits *s if there is a line containing
multiple basic blocks, and some are not executed. (The gcov
documentation says something weird about this point, so I'm trying
to interpret it into the compilerese that I'm familiar with.)
That's bug 26101.
Also, when we're looking for unique variations in our coverage, we
would like cov-diff to suppress timestamps on the diffs. That's bug
26102.
Both of these are bugfixes on 0.2.5.1-alpha when the cov-diff script
was introduced.
My apologies for the perl.
