Previously, the limit for MAX_PROTOCOLS_TO_EXPAND was actually being applied
in Rust to the maximum number of version (total, for all subprotocols).
Whereas in C, it was being applied to the number of subprotocols that were
allowed. This changes the Rust to match C's behaviour.
The behaviours still do not match, unsurprisingly, but now we know where a
primary difference is: the Rust is validating version ranges more than the C,
so in the C it's possible to call protover_all_supported on a ridiculous
version range like "Sleen=0-4294967294" because the C uses
MAX_PROTOCOLS_TO_EXPAND to count the number of *subprotocols* whereas the Rust
uses it to count the total number of *versions* of all subprotocols.
During code review and discussion with Chelsea Komlo, she pointed out
that protover::compute_for_old_tor() was a public function whose
return type was `&'static CStr`. We both agree that C-like parts of
APIs should:
1. not be exposed publicly (to other Rust crates),
2. only be called in the appropriate FFI code,
3. not expose types which are meant for FFI code (e.g. `*mut char`,
`CString`, `*const c_int`, etc.) to the pure-Rust code of other
crates.
4. FFI code (e.g. things in `ffi.rs` modules) should _never_ be called
from pure-Rust, not even from other modules in its own crate
(i.e. do not call `protover::ffi::*` from anywhere in
`protover::protoset::*`, etc).
With that in mind, this commit makes the following changes:
* CHANGE `protover::compute_for_old_tor()` to be
visible only at the `pub(crate)` level.
* RENAME `protover::compute_for_old_tor()` to
`protover::compute_for_old_tor_cstr()` to reflect the last change.
* ADD a new `protover::compute_for_old_tor()` function wrapper which
is public and intended for other Rust code to use, which returns a
`&str`.
It was changed to take borrows instead of taking ownership.
* REFACTOR `protover::ffi::protover_is_supported_here()` to use changed method
signature on `protover::is_supported_here()`.
This includes a subtle difference in behaviour to the previous Rust
implementation, where, for each vote that we're computing over, if a single one
fails to parse, we skip it. This now matches the current behaviour in the C
implementation.
* REFACTOR `protover::ffi::protover_compute_vote()` to use
new types and methods.
This includes a subtle difference in behaviour, as in 4258f1e18, where we return
(matching the C impl's return behaviour) earlier than before if parsing failed,
saving us computation in parsing the versions into a
protover::protoset::ProtoSet.
* REFACTOR `protover::ffi::protover_list_supports_protocol_or_later()` to use
new types and methods.
This includes a subtle difference in behaviour, as in 4258f1e18, where we return
(matching the C impl's return behaviour) earlier than before if parsing failed,
saving us computation in parsing the versions into a
protover::protoset::ProtoSet.
* REFACTOR `protover::ffi::protover_list_supports_protocol()` to use new types
and methods.
This includes differences in behaviour to before, which should now more closely
match the C version:
- If parsing a protover `char*` from C, and the string is not parseable, this
function will return 1 early, which matches the C behaviour when protocols
are unparseable. Previously, we would parse it and its version numbers
simultaneously, i.e. there was no fail early option, causing us to spend more
time unnecessarily parsing versions.
* REFACTOR `protover::ffi::protover_all_supported()` to use new types and
methods.
Previously, the rust implementation of protover considered an empty string to be
a valid ProtoEntry, while the C version did not (it must have a "=" character).
Other differences include that unknown protocols must now be parsed as
`protover::UnknownProtocol`s, and hence their entries as
`protover::UnvalidatedProtoEntry`s, whereas before (nearly) all protoentries
could be parsed regardless of how erroneous they might be considered by the C
version.
My apologies for this somewhat messy and difficult to read commit, if any part
is frustrating to the reviewer, please feel free to ask me to split this into
smaller changes (possibly hard to do, since so much changed), or ask me to
comment on a specific line/change and clarify how/when the behaviours differ.
The tests here should more closely match the behaviours exhibited by the C
implementation, but I do not yet personally guarantee they match precisely.
* REFACTOR unittests in protover::protover.
* ADD new integration tests for previously untested behaviour.
* FIXES part of #24031: https://bugs.torproject.org/24031.
This changes `protover::is_supported_here()` to be aware of new datatypes
(e.g. don't call `.0` on things which are no longer tuple structs) and also
changes the method signature to take borrows, making it faster, threadable, and
easier to read (i.e. the caller can know from reading the function signature
that the function won't mutate values passed into it).
* CHANGE the `protover::is_supported_here()` function to take borrows.
* REFACTOR the `protover::is_supported_here()` function to be aware of new
datatypes.
* FIXES part of #24031: https://bugs.torproject.org/24031
This adds a new type for votes upon `protover::ProtoEntry`s (technically, on
`protover::UnvalidatedProtoEntry`s, because the C code does not validate based
upon currently known protocols when voting, in order to maintain
future-compatibility), and converts several functions which would have operated
on this datatype into methods for ease-of-use and readability.
This also fixes a behavioural differentce to the C version of
protover_compute_vote(). The C version of protover_compute_vote() calls
expand_protocol_list() which checks if there would be too many subprotocols *or*
expanded individual version numbers, i.e. more than MAX_PROTOCOLS_TO_EXPAND, and
does this *per vote* (but only in compute_vote(), everywhere else in the C seems
to only care about the number of subprotocols, not the number of individual
versions). We need to match its behaviour in Rust and ensure we're not allowing
more than it would to get the votes to match.
* ADD new `protover::ProtoverVote` datatype.
* REMOVE the `protover::compute_vote()` function and refactor it into an
equivalent-in-behaviour albeit more memory-efficient voting algorithm based
on the new underlying `protover::protoset::ProtoSet` datatype, as
`ProtoverVote::compute()`.
* REMOVE the `protover::write_vote_to_string()` function, since this
functionality is now generated by the impl_to_string_for_proto_entry!() macro
for both `ProtoEntry` and `UnvalidatedProtoEntry` (the latter of which is the
correct type to return from a voting protocol instance, since the entity
voting may not know of all protocols being voted upon or known about by other
voting parties).
* FIXES part of #24031: https://bugs.torproject.org/24031
rust: Fix a difference in compute_vote() behaviour to C version.
This implements conversions from either a ProtoEntry or an UnvalidatedProtoEntry
into a String, for use in replacing such functions as
`protover::write_vote_to_string()`.
* ADD macro for implementing ToString trait for ProtoEntry and
UnvalidatedProtoEntry.
* FIXES part of #24031: https://bugs.torproject.org/24031
This adds a new protover::UnvalidatedProtoEntry type, which is the
UnknownProtocol variant of a ProtoEntry, and refactors several functions which
should operate on this type into methods.
This also fixes what was previously another difference to the C implementation:
if you asked the C version of protovet_compute_vote() to compute a single vote
containing "Fribble=", it would return NULL. However, the Rust version would
return "Fribble=" since it didn't check if the versions were empty before
constructing the string of differences. ("Fribble=" is technically a valid
protover string.) This is now fixed, and the Rust version in that case will,
analogous to (although safer than) C returning a NULL, return None.
* REMOVE internal `contains_only_supported_protocols()` function.
* REMOVE `all_supported()` function and refactor it into
`UnvalidatedProtoEntry::all_supported()`.
* REMOVE `parse_protocols_from_string_with_no_validation()` and
refactor it into the more rusty implementation of
`impl FromStr for UnvalidatedProtoEntry`.
* REMOVE `protover_string_supports_protocol()` and refactor it into
`UnvalidatedProtoEntry::supports_protocol()`.
* REMOVE `protover_string_supports_protocol_or_later()` and refactor
it into `UnvalidatedProtoEntry::supports_protocol_or_later()`.
* FIXES part of #24031: https://bugs.torproject.org/24031
rust: Fix another C/Rust different in compute_vote().
This fixes the unittest from the prior commit by checking if the versions are
empty before adding a protocol to a vote.
This replaces the `protover::SupportedProtocols` (why would you have a type just
for things which are supported?) with a new, more generic type,
`protover::ProtoEntry`, which utilises the new, more memory-efficient datatype
in protover::protoset.
* REMOVE `get_supported_protocols()` and `SupportedProtocols::tor_supported()`
(since they were never used separately) and collapse their functionality into
a single `ProtoEntry::supported()` method.
* REMOVE `SupportedProtocols::from_proto_entries()` and reimplement its
functionality as the more rusty `impl FromStr for ProtoEntry`.
* REMOVE `get_proto_and_vers()` function and refactor it into the more rusty
`impl FromStr for ProtoEntry`.
* FIXES part of #24031: https://bugs.torproject.org/24031
* ADD new type, protover::UnknownProtocol, so that we have greater type safety
and our protover functionality which works with unsanitised protocol names is
more clearly demarcated.
* REFACTOR protover::Proto, renaming it protover::Protocol to mirror the new
protover::UnknownProtocol type name.
* ADD a utility conversion of `impl From<Protocol> for UnknownProtocol` so that
we can easily with known protocols and unknown protocols simultaneously
(e.g. doing comparisons, checking their version numbers), while not allowing
UnknownProtocols to be accidentally used in functions which should only take
Protocols.
* FIXES part of #24031: https://bugs.torproject.org/24031
* ADD new protover::protoset module.
* ADD new protover::protoset::ProtoSet class for holding protover versions.
* REMOVE protover::Versions type implementation and its method
`from_version_string()`, and instead implement this behaviour in a more
rust-like manner as `impl FromStr for ProtoSet`.
* MOVE the `find_range()` utility function from protover::protover to
protover::protoset since it's only used internally in the
implementation of ProtoSet.
* REMOVE the `contract_protocol_list()` function from protover::protover and
instead refactor it (reusing nearly the entire thing, with minor superficial,
i.e. non-behavioural, changes) into a more rusty
`impl ToString for ProtoSet`.
* REMOVE the `expand_version_range()` function from protover::protover and
instead refactor it into a more rusty implementation of
`impl Into<Vec<Version>> for ProtoSet` using the new error types in
protover::errors.
* FIXES part of #24031: https://bugs.torproject.org/24031.
This will allow us to do actual error handling intra-crate in a more
rusty manner, e.g. propogating errors in match statements, conversion
between error types, logging messages, etc.
* FIXES part of #24031: https://bugs.torproject.org/24031.
Also correct MAX_VERSIONS_TO_EXPAND to match the C.
NOTE that this patch leads to incorrect behavior: the C code allows
huge ranges; it just doesn't allow votes on them (currently). For
full compatibility, we'll need to make the rust code store ranges as
ranges natively, possibly using something like the range_map crate.
Still, this patch is smaller than a "proper" fix.
Fixes TROVE-2018-003.
Rationale: this helps for performance only, but we don't actually
have any reason to think that the checks here are
performance-critical. Let's not normalize the use of unsafe {}.
* FIXES#25127: https://bugs.torproject.org/25127
* ADDS a new module to the Rust tor_util crate for small utilities
for working with static strings between languages.
* CHANGES the return type of protover_compute_for_old_tor to point to
immutable data.
* CHANGES the code from the previous commit to use the new static
string utilities.
And fix the unsupported protover example so it uses a Link protover much
higher than 5.
Part of #25070, bugfix on 0.3.3.1-alpha, which introduced the protover crate.
