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Verify only the required signatures on verify_event (#394)

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The spec says that the required signatures for a signed event is the
signature of sender's server (unless is a third party invite) and the
`event_id` server (in v1 and v2 room versions).

This changes the previous behaviour, which tried to verify the
signatures for all the servers in the `PublicKeyMap`, instead of
checking only the required signatures.

Relevant spec section:
https://matrix.org/docs/spec/server_server/r0.1.4#validating-hashes-and-signatures-on-received-events
This commit is contained in:
gnieto 2021-01-18 23:21:47 +01:00 committed by GitHub
parent 1b22c252f6
commit 0635b40729
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 267 additions and 12 deletions
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4
ruma-signatures/CHANGELOG.md
View File

@ -5,3 +5,7 @@ Breaking changes:
* Remove `Copy` implementation for `Algorithm`
* Remove `Copy` and `Clone` implementations for `Ed25519Verifier`
* Upgrade ruma-identifiers
Bug fixes:
* Verify only the required signatures on `verify_event`

275
ruma-signatures/src/functions.rs
View File

@ -1,10 +1,14 @@
//! Functions for signing and verifying JSON and events.
use std::{collections::BTreeMap, mem};
use std::{
collections::{BTreeMap, BTreeSet},
mem,
str::FromStr,
};
use base64::{decode_config, encode_config, STANDARD_NO_PAD, URL_SAFE_NO_PAD};
use ring::digest::{digest, SHA256};
use ruma_identifiers::RoomVersionId;
use ruma_identifiers::{EventId, RoomVersionId, ServerNameBox, UserId};
use ruma_serde::{to_canonical_json_string, CanonicalJsonObject, CanonicalJsonValue};
use serde_json::from_str as from_json_str;
@ -506,12 +510,12 @@ where
Ok(())
}
/// Uses a set of public keys to verify a signed event.
/// Verifies that the signed event contains all the required valid signatures.
///
/// Some room versions may require signatures from multiple homeservers, so this function takes a
/// map from servers to sets of public keys. For each homeserver present in the map, this function
/// will require a valid signature. All known public keys for a homeserver should be provided. The
/// first one found on the given event will be used.
/// map from servers to sets of public keys. Signatures are verified for each required homeserver.
/// All known public keys for a homeserver should be provided. The first one found on the given
/// event will be used.
///
/// If the `Ok` variant is returned by this function, it will contain a `Verified` value which
/// distinguishes an event with valid signatures and a matching content hash with an event with
@ -524,6 +528,7 @@ where
/// "example.com") for which a signature must be verified. Key identifiers for each server (e.g.
/// "ed25519:1") then map to their respective public keys.
/// * object: The JSON object of the event that was signed.
/// * version: Room version of the given event
///
/// # Examples
///
@ -531,6 +536,7 @@ where
/// # use std::collections::BTreeMap;
/// # use ruma_identifiers::RoomVersionId;
/// # use ruma_signatures::verify_event;
/// # use ruma_signatures::Verified;
/// #
/// const PUBLIC_KEY: &str = "XGX0JRS2Af3be3knz2fBiRbApjm2Dh61gXDJA8kcJNI";
///
@ -567,7 +573,9 @@ where
/// public_key_map.insert("domain".into(), public_key_set);
///
/// // Verify at least one signature for each entity in `public_key_map`.
/// assert!(verify_event(&public_key_map, &object, &RoomVersionId::Version6).is_ok());
/// let verification_result = verify_event(&public_key_map, &object, &RoomVersionId::Version6);
/// assert!(verification_result.is_ok());
/// assert!(matches!(verification_result.unwrap(), Verified::All));
/// ```
pub fn verify_event(
public_key_map: &PublicKeyMap,
@ -596,8 +604,11 @@ pub fn verify_event(
None => return Err(Error::new("JSON object must contain a `signatures` field.")),
};
for (entity_id, public_keys) in public_key_map {
let signature_set = match signature_map.get(entity_id) {
let servers_to_check = servers_to_check_signatures(object, version)?;
let canonical_json = from_json_str(&canonical_json(&redacted))?;
for entity_id in servers_to_check {
let signature_set = match signature_map.get(entity_id.as_str()) {
Some(CanonicalJsonValue::Object(set)) => set,
Some(_) => return Err(Error::new("signatures sets must be JSON objects")),
None => {
@ -608,6 +619,10 @@ pub fn verify_event(
let mut maybe_signature = None;
let mut maybe_public_key = None;
let public_keys = public_key_map
.get(entity_id.as_str())
.ok_or_else(|| Error::new(format!("missing public keys for server {}", entity_id)))?;
for (key_id, public_key) in public_keys {
// Since only ed25519 is supported right now, we don't actually need to check what the
// algorithm is. If it split successfully, it's ed25519.
@ -638,8 +653,6 @@ pub fn verify_event(
}
};
let canonical_json = from_json_str(&canonical_json(&redacted))?;
let signature_bytes = decode_config(signature, STANDARD_NO_PAD)?;
let public_key_bytes = decode_config(&public_key, STANDARD_NO_PAD)?;
@ -731,13 +744,75 @@ pub fn redact(
Ok(event)
}
/// Extracts the server names to check signatures for given event. It will return the sender's
/// server (unless it's a third party invite) and the event id server (on v1 and v2 room versions)
fn servers_to_check_signatures(
object: &CanonicalJsonObject,
version: &RoomVersionId,
) -> Result<BTreeSet<ServerNameBox>, Error> {
let mut servers_to_check = BTreeSet::new();
if !is_third_party_invite(object)? {
match object.get("sender") {
Some(CanonicalJsonValue::String(raw_sender)) => {
let user_id = UserId::from_str(raw_sender)
.map_err(|_| Error::new("could not parse user id"))?;
servers_to_check.insert(user_id.server_name().to_owned());
}
_ => return Err(Error::new("field `sender` must be a JSON string")),
};
}
match version {
RoomVersionId::Version1 | RoomVersionId::Version2 => match object.get("event_id") {
Some(CanonicalJsonValue::String(raw_event_id)) => {
let event_id = EventId::from_str(raw_event_id)
.map_err(|_| Error::new("could not parse event id"))?;
let server_name = event_id
.server_name()
.ok_or_else(|| {
Error::new("Event id should have a server name for the given room version")
})?
.to_owned();
servers_to_check.insert(server_name);
}
_ => {
return Err(Error::new(
"Expected to find a string `event_id` for the given room version",
))
}
},
_ => (),
}
Ok(servers_to_check)
}
/// Checks if `object` contains an event of type `m.room.third_party_invite`
fn is_third_party_invite(object: &CanonicalJsonObject) -> Result<bool, Error> {
match object.get("type") {
Some(CanonicalJsonValue::String(raw_type)) => Ok(raw_type == "m.room.third_party_invite"),
_ => Err(Error::new("field `type` must be a JSON string")),
}
}
#[cfg(test)]
mod tests {
use std::{
collections::BTreeMap,
convert::{TryFrom, TryInto},
};
use base64::{encode_config, STANDARD_NO_PAD};
use ruma_identifiers::{RoomVersionId, ServerSigningKeyId, SigningKeyAlgorithm};
use ruma_serde::CanonicalJsonValue;
use serde_json::json;
use std::convert::TryFrom;
use super::canonical_json;
use crate::{sign_json, verify_event, Ed25519KeyPair, PublicKeyMap, PublicKeySet, Verified};
#[test]
fn canonical_json_complex() {
@ -770,4 +845,180 @@ mod tests {
assert_eq!(canonical_json(&object), canonical);
}
#[test]
fn verify_event_does_not_check_signatures_for_third_party_invites() {
let signed_event = serde_json::from_str(
r#"{
"auth_events": [],
"content": {},
"depth": 3,
"hashes": {
"sha256": "5jM4wQpv6lnBo7CLIghJuHdW+s2CMBJPUOGOC89ncos"
},
"origin": "domain",
"origin_server_ts": 1000000,
"prev_events": [],
"room_id": "!x:domain",
"sender": "@a:domain",
"signatures": {
"domain": {
"ed25519:1": "KxwGjPSDEtvnFgU00fwFz+l6d2pJM6XBIaMEn81SXPTRl16AqLAYqfIReFGZlHi5KLjAWbOoMszkwsQma+lYAg"
}
},
"type": "m.room.third_party_invite",
"unsigned": {
"age_ts": 1000000
}
}"#
).unwrap();
let public_key_map = BTreeMap::new();
let verification_result =
verify_event(&public_key_map, &signed_event, &RoomVersionId::Version6);
assert!(verification_result.is_ok());
let verification = verification_result.unwrap();
assert!(matches!(verification, Verified::Signatures));
}
#[test]
fn verify_event_check_signatures_for_both_sender_and_event_id() {
let key_pair_sender = generate_key_pair();
let key_pair_event = generate_key_pair();
let mut signed_event = serde_json::from_str(
r#"{
"event_id": "$event_id:domain-event",
"auth_events": [],
"content": {},
"depth": 3,
"hashes": {
"sha256": "5jM4wQpv6lnBo7CLIghJuHdW+s2CMBJPUOGOC89ncos"
},
"origin": "domain",
"origin_server_ts": 1000000,
"prev_events": [],
"room_id": "!x:domain",
"sender": "@name:domain-sender",
"type": "X",
"unsigned": {
"age_ts": 1000000
}
}"#,
)
.unwrap();
sign_json("domain-sender", &key_pair_sender, &mut signed_event).unwrap();
sign_json("domain-event", &key_pair_event, &mut signed_event).unwrap();
let mut public_key_map = BTreeMap::new();
add_key_to_map(&mut public_key_map, "domain-sender", &key_pair_sender);
add_key_to_map(&mut public_key_map, "domain-event", &key_pair_event);
let verification_result =
verify_event(&public_key_map, &signed_event, &RoomVersionId::Version1);
assert!(verification_result.is_ok());
let verification = verification_result.unwrap();
assert!(matches!(verification, Verified::Signatures));
}
#[test]
fn verification_fails_if_required_keys_are_not_given() {
let key_pair_sender = generate_key_pair();
let mut signed_event = serde_json::from_str(
r#"{
"auth_events": [],
"content": {},
"depth": 3,
"hashes": {
"sha256": "5jM4wQpv6lnBo7CLIghJuHdW+s2CMBJPUOGOC89ncos"
},
"origin": "domain",
"origin_server_ts": 1000000,
"prev_events": [],
"room_id": "!x:domain",
"sender": "@name:domain-sender",
"type": "X",
"unsigned": {
"age_ts": 1000000
}
}"#,
)
.unwrap();
sign_json("domain-sender", &key_pair_sender, &mut signed_event).unwrap();
// Verify with an empty public key map should fail due to missing public keys
let public_key_map = BTreeMap::new();
let verification_result =
verify_event(&public_key_map, &signed_event, &RoomVersionId::Version6);
assert!(verification_result.is_err());
let error_msg = verification_result.err().unwrap().message;
assert!(error_msg.contains("missing public keys for server"));
}
#[test]
fn verify_event_fails_if_public_key_is_invalid() {
let key_pair_sender = generate_key_pair();
let mut signed_event = serde_json::from_str(
r#"{
"auth_events": [],
"content": {},
"depth": 3,
"hashes": {
"sha256": "5jM4wQpv6lnBo7CLIghJuHdW+s2CMBJPUOGOC89ncos"
},
"origin": "domain",
"origin_server_ts": 1000000,
"prev_events": [],
"room_id": "!x:domain",
"sender": "@name:domain-sender",
"type": "X",
"unsigned": {
"age_ts": 1000000
}
}"#,
)
.unwrap();
sign_json("domain-sender", &key_pair_sender, &mut signed_event).unwrap();
let mut public_key_map = PublicKeyMap::new();
let mut sender_key_map = PublicKeySet::new();
let newly_generated_key_pair = generate_key_pair();
let encoded_public_key =
encode_config(newly_generated_key_pair.public_key(), STANDARD_NO_PAD);
let version = ServerSigningKeyId::from_parts(
SigningKeyAlgorithm::Ed25519,
key_pair_sender.version().try_into().unwrap(),
);
sender_key_map.insert(version.to_string(), encoded_public_key);
public_key_map.insert("domain-sender".to_string(), sender_key_map);
let verification_result =
verify_event(&public_key_map, &signed_event, &RoomVersionId::Version6);
assert!(verification_result.is_err());
let error_msg = verification_result.err().unwrap().message;
assert!(error_msg.contains("signature verification failed"));
}
fn generate_key_pair() -> Ed25519KeyPair {
let key_content = Ed25519KeyPair::generate().unwrap();
Ed25519KeyPair::new(&key_content, "1".to_string()).unwrap()
}
fn add_key_to_map(public_key_map: &mut PublicKeyMap, name: &str, pair: &Ed25519KeyPair) {
let mut sender_key_map = PublicKeySet::new();
let encoded_public_key = encode_config(pair.public_key(), STANDARD_NO_PAD);
let version = ServerSigningKeyId::from_parts(
SigningKeyAlgorithm::Ed25519,
pair.version().try_into().unwrap(),
);
sender_key_map.insert(version.to_string(), encoded_public_key);
public_key_map.insert(name.to_string(), sender_key_map);
}
}