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
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
Previously, if "Link=1-5" was supported, and you asked protover_all_supported()
(or protover::all_supported() in Rust) if it supported "Link=3-999", the C
version would return "Link=3-999" and the Rust would return "Link=6-999". These
both behave the same now, i.e. both return "Link=6-999".
Previously, if "Link=1-5" was supported, and you asked protover_all_supported()
(or protover::all_supported() in Rust) if it supported "Link=3-999", the C
version would return "Link=3-999" and the Rust would return "Link=6-999". These
both behave the same now, i.e. both return "Link=6-999".
The C code and the rust code had different separate integer overflow
bugs here. That suggests that we're better off just forbidding this
pathological case.
Also, add tests for expected behavior on receiving a bad protocol
list in a consensus.
Fixes another part of 25249.
This one can only be exploited if you can generate a correctly
signed consensus, so it's not as bad as 25074.
Fixes bug 25251; also tracked as TROVE-2018-004.
In some cases we had checked for it, but in others we had not. One
of these cases could have been used to remotely cause
denial-of-service against directory authorities while they attempted
to vote.
Fixes TROVE-2018-001.
When computing old Tor protocol line version in protover, we were looking at
0.2.7.5 twice instead of the specific case for 0.2.9.1-alpha.
Fixes#20810
Signed-off-by: David Goulet <dgoulet@torproject.org>
Use the following coccinelle script to change uses of
smartlist_add(sl, tor_strdup(str)) to
smartlist_add_strdup(sl, string) (coccinelle script from nickm
via bug 20048):
@@
expression a;
expression b;
@@
- smartlist_add
+ smartlist_add_strdup
(a,
- tor_strdup(
b
- )
)
This commit adds or improves the module-level documenation for:
buffers.c circuitstats.c command.c connection_edge.c control.c
cpuworker.c crypto_curve25519.c crypto_curve25519.h
crypto_ed25519.c crypto_format.c dircollate.c dirserv.c dns.c
dns_structs.h fp_pair.c geoip.c hibernate.c keypin.c ntmain.c
onion.c onion_fast.c onion_ntor.c onion_tap.c periodic.c
protover.c protover.h reasons.c rephist.c replaycache.c
routerlist.c routerparse.c routerset.c statefile.c status.c
tor_main.c workqueue.c
In particular, I've tried to explain (for each documented module)
what each module does, what's in it, what the big idea is, why it
belongs in Tor, and who calls it. In a few cases, I've added TODO
notes about refactoring opportunities.
I've also renamed an argument, and fixed a few DOCDOC comments.
