crypto: Canonicalize the start event content before calculating the commitment

This fixes: #117.
This commit is contained in:
Damir Jelić 2020-12-08 16:01:42 +01:00
parent 8e53982bcd
commit fd705b7d5e
3 changed files with 71 additions and 22 deletions

View file

@ -8,7 +8,7 @@ pub use ruma::{
AuthScheme, EndpointError, OutgoingRequest,
},
directory, encryption, events, identifiers, presence, push,
serde::Raw,
serde::{CanonicalJsonValue, Raw},
thirdparty, Outgoing,
};

View file

@ -16,16 +16,19 @@ use std::{collections::BTreeMap, convert::TryInto};
use tracing::{trace, warn};
use olm_rs::sas::OlmSas;
use olm_rs::{sas::OlmSas, utility::OlmUtility};
use matrix_sdk_common::{
api::r0::to_device::DeviceIdOrAllDevices,
events::{
key::verification::{cancel::CancelCode, mac::MacToDeviceEventContent},
key::verification::{
cancel::CancelCode, mac::MacToDeviceEventContent, start::StartToDeviceEventContent,
},
AnyToDeviceEventContent, EventType, ToDeviceEvent,
},
identifiers::{DeviceId, DeviceKeyAlgorithm, DeviceKeyId, UserId},
uuid::Uuid,
CanonicalJsonValue,
};
use crate::{
@ -40,6 +43,26 @@ pub struct SasIds {
pub other_identity: Option<UserIdentities>,
}
/// Calculate the commitment for a accept event from the public key and the
/// start event.
///
/// # Arguments
///
/// * `public_key` - Our own ephemeral public key that is used for the
/// interactive verification.
///
/// * `content` - The `m.key.verification.start` event content that started the
/// interactive verification process.
pub fn calculate_commitment(public_key: &str, content: &StartToDeviceEventContent) -> String {
let json_content: CanonicalJsonValue = serde_json::to_value(content)
.expect("Can't serialize content")
.try_into()
.expect("Can't canonicalize content");
let utility = OlmUtility::new();
utility.sha256_utf8_msg(&format!("{}{}", public_key, json_content))
}
/// Get a tuple of an emoji and a description of the emoji using a number.
///
/// This is taken directly from the [spec]
@ -493,12 +516,38 @@ pub fn content_to_request(
#[cfg(test)]
mod test {
use matrix_sdk_common::events::key::verification::start::StartToDeviceEventContent;
use proptest::prelude::*;
use serde_json::json;
use super::{bytes_to_decimal, bytes_to_emoji, bytes_to_emoji_index, emoji_from_index};
use super::{
bytes_to_decimal, bytes_to_emoji, bytes_to_emoji_index, calculate_commitment,
emoji_from_index,
};
#[test]
fn test_emoji_generation() {
fn commitment_calculation() {
let commitment = "CCQmB4JCdB0FW21FdAnHj/Hu8+W9+Nb0vgwPEnZZQ4g";
let public_key = "Q/NmNFEUS1fS+YeEmiZkjjblKTitrKOAk7cPEumcMlg";
let content = json!({
"from_device":"XOWLHHFSWM",
"transaction_id":"bYxBsirjUJO9osar6ST4i2M2NjrYLA7l",
"method":"m.sas.v1",
"key_agreement_protocols":["curve25519-hkdf-sha256","curve25519"],
"hashes":["sha256"],
"message_authentication_codes":["hkdf-hmac-sha256","hmac-sha256"],
"short_authentication_string":["decimal","emoji"]
});
let content: StartToDeviceEventContent = serde_json::from_value(content).unwrap();
let calculated_commitment = calculate_commitment(public_key, &content);
assert_eq!(commitment, &calculated_commitment);
}
#[test]
fn emoji_generation() {
let bytes = vec![0, 0, 0, 0, 0, 0];
let index: Vec<(&'static str, &'static str)> = vec![0, 0, 0, 0, 0, 0, 0]
.into_iter()
@ -516,7 +565,7 @@ mod test {
}
#[test]
fn test_decimal_generation() {
fn decimal_generation() {
let bytes = vec![0, 0, 0, 0, 0];
let result = bytes_to_decimal(bytes);

View file

@ -19,7 +19,7 @@ use std::{
time::{Duration, Instant},
};
use olm_rs::{sas::OlmSas, utility::OlmUtility};
use olm_rs::sas::OlmSas;
use matrix_sdk_common::{
events::{
@ -40,8 +40,11 @@ use matrix_sdk_common::{
identifiers::{DeviceId, UserId},
uuid::Uuid,
};
use tracing::error;
use super::helpers::{get_decimal, get_emoji, get_mac_content, receive_mac_event, SasIds};
use super::helpers::{
calculate_commitment, get_decimal, get_emoji, get_mac_content, receive_mac_event, SasIds,
};
use crate::{
identities::{ReadOnlyDevice, UserIdentities},
@ -176,7 +179,7 @@ pub struct Started {
#[derive(Clone, Debug)]
pub struct Accepted {
accepted_protocols: Arc<AcceptedProtocols>,
json_start_content: String,
start_content: Arc<StartToDeviceEventContent>,
commitment: String,
}
@ -348,8 +351,7 @@ impl SasState<Created> {
let accepted_protocols =
AcceptedProtocols::try_from(content.clone()).map_err(|c| self.clone().cancel(c))?;
let json_start_content = serde_json::to_string(&self.as_content())
.expect("Can't deserialize start event content");
let start_content = self.as_content().into();
Ok(SasState {
inner: self.inner,
@ -358,9 +360,9 @@ impl SasState<Created> {
creation_time: self.creation_time,
last_event_time: self.last_event_time,
state: Arc::new(Accepted {
json_start_content,
start_content,
commitment: content.commitment.clone(),
accepted_protocols: Arc::new(accepted_protocols),
accepted_protocols: accepted_protocols.into(),
}),
})
} else {
@ -391,12 +393,14 @@ impl SasState<Started> {
) -> Result<SasState<Started>, SasState<Canceled>> {
if let StartMethod::MSasV1(content) = &event.content.method {
let sas = OlmSas::new();
let utility = OlmUtility::new();
let json_content =
serde_json::to_string(&event.content).expect("Can't serialize content");
let pubkey = sas.public_key();
let commitment = utility.sha256_utf8_msg(&format!("{}{}", pubkey, json_content));
let commitment = calculate_commitment(&pubkey, &event.content);
error!(
"Calculated commitment for pubkey {} and content {:?} {}",
pubkey, event.content, commitment
);
let sas = SasState {
inner: Arc::new(Mutex::new(sas)),
@ -540,11 +544,7 @@ impl SasState<Accepted> {
self.check_event(&event.sender, &event.content.transaction_id)
.map_err(|c| self.clone().cancel(c))?;
let utility = OlmUtility::new();
let commitment = utility.sha256_utf8_msg(&format!(
"{}{}",
event.content.key, self.state.json_start_content
));
let commitment = calculate_commitment(&event.content.key, &self.state.start_content);
if self.state.commitment != commitment {
Err(self.cancel(CancelCode::InvalidMessage))