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//! Configuration information for onion services.
use crate::internal_prelude::*;
use tor_cell::relaycell::hs::est_intro;
/// Configuration for one onion service.
#[derive(Debug, Clone, Builder, Eq, PartialEq)]
#[builder(build_fn(error = "ConfigBuildError", validate = "Self::validate"))]
#[builder(derive(Serialize, Deserialize, Debug, Deftly, Eq, PartialEq))]
#[builder_struct_attr(derive_deftly(tor_config::Flattenable))]
pub struct OnionServiceConfig {
/// The nickname used to look up this service's keys, state, configuration, etc.
pub(crate) nickname: HsNickname,
// TODO: Perhaps this belongs at a higher level. Perhaps we don't need it
// at all.
//
// enabled: bool,
/// Whether we want this to be a non-anonymous "single onion service".
/// We could skip this in v1. We should make sure that our state
/// is built to make it hard to accidentally set this.
#[builder(default)]
pub(crate) anonymity: crate::Anonymity,
/// Number of intro points; defaults to 3; max 20.
#[builder(default = "DEFAULT_NUM_INTRO_POINTS")]
pub(crate) num_intro_points: u8,
/// A rate-limit on the acceptable rate of introduction requests.
///
/// We send this to the send to the introduction point to configure how many
/// introduction requests it sends us.
/// If this is not set, the introduction point chooses a default based on
/// the current consensus.
///
/// We do not enforce this limit ourselves.
///
/// This configuration is sent as a `DOS_PARAMS` extension, as documented in
/// <https://spec.torproject.org/rend-spec/introduction-protocol.html#EST_INTRO_DOS_EXT>.
#[builder(default)]
rate_limit_at_intro: Option<TokenBucketConfig>,
/// How many streams will we allow to be open at once for a single circuit on
/// this service?
#[builder(default = "65535")]
max_concurrent_streams_per_circuit: u32,
// TODO POW: The POW items are disabled for now, since they aren't implemented.
// /// If true, we will require proof-of-work when we're under heavy load.
// // enable_pow: bool,
// /// Disable the compiled backend for proof-of-work.
// // disable_pow_compilation: bool,
// TODO POW: C tor has this, but I don't know if we want it.
//
// TODO POW: It's possible that we want this to relate, somehow, to our
// rate_limit_at_intro settings.
//
// /// A rate-limit on dispatching requests from the request queue when
// /// our proof-of-work defense is enabled.
// pow_queue_rate: TokenBucketConfig,
// ...
// /// Configure descriptor-based client authorization.
// ///
// /// When this is enabled, we encrypt our list of introduction point and keys
// /// so that only clients holding one of the listed keys can decrypt it.
//
// TODO (#1206): we'd like this to be an Option, but that doesn't work well with
// sub_builder. We need to figure out what to do there.
//
// TODO (#1206): Temporarily disabled while we figure out how we want it to work;
// see also #1028
//
// pub(crate) encrypt_descriptor: Option<DescEncryptionConfig>,
}
/// Default number of introduction points.
const DEFAULT_NUM_INTRO_POINTS: u8 = 3;
impl OnionServiceConfig {
/// Return a reference to this configuration's nickname.
pub fn nickname(&self) -> &HsNickname {
&self.nickname
}
/// Check whether an onion service running with this configuration can
/// switch over `other` according to the rules of `how`.
///
// Return an error if it can't; otherwise return the new config that we
// should change to.
pub(crate) fn for_transition_to(
&self,
mut other: OnionServiceConfig,
how: tor_config::Reconfigure,
) -> Result<OnionServiceConfig, tor_config::ReconfigureError> {
/// Arguments to a handler for a field
///
/// The handler must:
/// * check whether this field can be updated
/// * if necessary, throw an error (in which case `*other` may be wrong)
/// * if it doesn't throw an error, ensure that `*other`
/// is appropriately updated.
//
// We could have a trait but that seems overkill.
#[allow(clippy::missing_docs_in_private_items)] // avoid otiosity
struct HandlerInput<'i, 'o, T> {
how: tor_config::Reconfigure,
self_: &'i T,
other: &'o mut T,
field_name: &'i str,
}
/// Convenience alias
type HandlerResult = Result<(), tor_config::ReconfigureError>;
/// Handler for config fields that cannot be changed
#[allow(clippy::needless_pass_by_value)]
fn unchangeable<T: Clone + PartialEq>(i: HandlerInput<T>) -> HandlerResult {
if i.self_ != i.other {
i.how.cannot_change(i.field_name)?;
// If we reach here, then `how` is WarnOnFailures, so we keep the
// original value.
*i.other = i.self_.clone();
}
Ok(())
}
/// Handler for config fields that can be freely changed
#[allow(clippy::unnecessary_wraps)]
fn simply_update<T>(_: HandlerInput<T>) -> HandlerResult {
Ok(())
}
/// Check all the fields. Input maps fields to handlers.
macro_rules! fields { {
$(
$field:ident: $handler:expr
),* $(,)?
} => {
// prove that we have handled every field
let OnionServiceConfig { $( $field: _, )* } = self;
$(
$handler(HandlerInput {
how,
self_: &self.$field,
other: &mut other.$field,
field_name: stringify!($field),
})?;
)*
} }
fields! {
nickname: unchangeable,
// Note: C Tor absolutely forbids changing between different
// values here.
//
// The rationale thinking here is that if you have ever published a
// given service non-anonymously, it is de-anonymized forever, and
// that if you ever de-anonymize a service, you are de-anonymizing
// it retroactively.
//
// We may someday want to ease this behavior.
anonymity: unchangeable,
// IPT manager will respond by adding or removing IPTs as desired.
// (Old IPTs are not proactively removed, but they will not be replaced
// as they are rotated out.)
num_intro_points: simply_update,
// IPT manager's "new configuration" select arm handles this,
// by replacing IPTs if necessary.
rate_limit_at_intro: simply_update,
// We extract this on every introduction request.
max_concurrent_streams_per_circuit: simply_update,
}
Ok(other)
}
/// Return the DosParams extension we should send for this configuration, if any.
pub(crate) fn dos_extension(&self) -> Result<Option<est_intro::DosParams>, crate::FatalError> {
Ok(self
.rate_limit_at_intro
.as_ref()
.map(dos_params_from_token_bucket_config)
.transpose()
.map_err(into_internal!(
"somehow built an un-validated rate-limit-at-intro"
))?)
}
/// Return a RequestFilter based on this configuration.
pub(crate) fn filter_settings(&self) -> crate::rend_handshake::RequestFilter {
crate::rend_handshake::RequestFilter {
max_concurrent_streams: self.max_concurrent_streams_per_circuit as usize,
}
}
}
impl OnionServiceConfigBuilder {
/// Builder helper: check whether the options in this builder are consistent.
fn validate(&self) -> Result<(), ConfigBuildError> {
/// Largest number of introduction points supported.
///
/// (This is not a very principled value; it's just copied from the C
/// implementation.)
const MAX_NUM_INTRO_POINTS: u8 = 20;
/// Supported range of numbers of intro points.
const ALLOWED_NUM_INTRO_POINTS: std::ops::RangeInclusive<u8> =
DEFAULT_NUM_INTRO_POINTS..=MAX_NUM_INTRO_POINTS;
// Make sure MAX_INTRO_POINTS is in range.
if let Some(ipts) = self.num_intro_points {
if !ALLOWED_NUM_INTRO_POINTS.contains(&ipts) {
return Err(ConfigBuildError::Invalid {
field: "num_intro_points".into(),
problem: format!(
"out of range {}-{}",
DEFAULT_NUM_INTRO_POINTS, MAX_NUM_INTRO_POINTS
),
});
}
}
// Make sure that our rate_limit_at_intro is valid.
if let Some(Some(ref rate_limit)) = self.rate_limit_at_intro {
let _ignore_extension: est_intro::DosParams =
dos_params_from_token_bucket_config(rate_limit)?;
}
Ok(())
}
/// Return the configured nickname for this service, if it has one.
pub fn peek_nickname(&self) -> Option<&HsNickname> {
self.nickname.as_ref()
}
}
/// Configure a token-bucket style limit on some process.
//
// TODO: Someday we may wish to lower this; it will be used in far more places.
//
// TODO: Do we want to parameterize this, or make it always u32? Do we want to
// specify "per second"?
#[derive(Debug, Clone, Serialize, Deserialize, Eq, PartialEq)]
pub struct TokenBucketConfig {
/// The maximum number of items to process per second.
rate: u32,
/// The maximum number of items to process in a single burst.
burst: u32,
}
impl TokenBucketConfig {
/// Create a new token-bucket configuration to rate-limit some action.
///
/// The "bucket" will have a maximum capacity of `burst`, and will fill at a
/// rate of `rate` per second. New actions are permitted if the bucket is nonempty;
/// each action removes one token from the bucket.
pub fn new(rate: u32, burst: u32) -> Self {
Self { rate, burst }
}
}
/// Helper: Try to create a DosParams from a given token bucket configuration.
/// Give an error if the value is out of range.
///
/// This is a separate function so we can use the same logic when validating
/// and when making the extension object.
fn dos_params_from_token_bucket_config(
c: &TokenBucketConfig,
) -> Result<est_intro::DosParams, ConfigBuildError> {
let err = || ConfigBuildError::Invalid {
field: "rate_limit_at_intro".into(),
problem: "out of range".into(),
};
let cast = |n| i32::try_from(n).map_err(|_| err());
est_intro::DosParams::new(Some(cast(c.rate)?), Some(cast(c.burst)?)).map_err(|_| err())
}
/// Configuration for descriptor encryption.
#[derive(Debug, Clone, Builder, PartialEq)]
#[builder(derive(Serialize, Deserialize))]
#[non_exhaustive]
pub struct DescEncryptionConfig {
/// A list of our authorized clients.
///
/// Note that if this list is empty, no clients can connect.
//
// TODO (#1206): It might be good to replace this with a trait or something, so that
// we can let callers give us a ClientKeyProvider or some plug-in that reads
// keys from somewhere else. On the other hand, we might have this configure
// our default ClientKeyProvider, and only allow programmatic ClientKeyProviders
pub authorized_client: Vec<AuthorizedClientConfig>,
}
/// A single client (or a collection of clients) authorized using the descriptor encryption mechanism.
#[derive(Debug, Clone, PartialEq, serde_with::DeserializeFromStr, serde_with::SerializeDisplay)]
#[non_exhaustive]
pub enum AuthorizedClientConfig {
/// A directory full of authorized public keys.
///
/// Currently, only valid unicode pathnames are supported.
DirectoryOfKeys(String),
/// A single authorized public key.
Curve25519Key(HsClientDescEncKey),
}
impl std::fmt::Display for AuthorizedClientConfig {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Self::DirectoryOfKeys(pb) => write!(f, "dir:{}", pb),
Self::Curve25519Key(key) => write!(
f,
"curve25519:{}",
Base64Unpadded::encode_string(key.as_bytes())
),
}
}
}
/// A problem encountered while parsing an AuthorizedClientConfig.
#[derive(thiserror::Error, Clone, Debug)]
#[non_exhaustive]
pub enum AuthorizedClientParseError {
/// Didn't recognize the type of this [`AuthorizedClientConfig`].
///
/// Recognized types are `dir` and `curve25519`.
#[error("Unrecognized authorized client type")]
InvalidType,
/// Couldn't parse a curve25519 key.
#[error("Invalid curve25519 key")]
InvalidKey,
}
impl std::str::FromStr for AuthorizedClientConfig {
type Err = AuthorizedClientParseError;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let Some((tp, val)) = s.split_once(':') else {
return Err(Self::Err::InvalidType);
};
if tp == "dir" {
Ok(Self::DirectoryOfKeys(val.into()))
} else if tp == "curve25519" {
let bytes: [u8; 32] = Base64Unpadded::decode_vec(val)
.map_err(|_| Self::Err::InvalidKey)?
.try_into()
.map_err(|_| Self::Err::InvalidKey)?;
Ok(Self::Curve25519Key(HsClientDescEncKey::from(
curve25519::PublicKey::from(bytes),
)))
} else {
Err(Self::Err::InvalidType)
}
}
}