troll-patrol/src/positive_report.rs

// For Lox-related code where points are uppercase and scalars are lowercase
#![allow(non_snake_case)]

// TODO: Make SerializableBridgeToken, check its fields while deserializing,
// check that its fields match the report's fields while deserializing a report

use crate::{get_date, CONFIG, COUNTRY_CODES};

use curve25519_dalek::Scalar;
use ed25519_dalek::{Signature, Signer, SigningKey, Verifier, VerifyingKey};
use lox_library::{cred::Lox, proto::positive_report as lox_pr, IssuerPubKey};
use serde::{Deserialize, Serialize};
use sha1::{Digest, Sha1};
use std::option::Option;

#[derive(Debug)]
pub enum PositiveReportError {
    DateInFuture,
    FailedToDeserialize, // couldn't deserialize to SerializablePositiveReport
    InvalidCountryCode,
    MissingBridgeToken,
    MissingCountryCode,
}

/// A report that the user was able to connect to the bridge
pub struct PositiveReport {
    /// hashed fingerprint (SHA-1 hash of 20-byte bridge ID)
    pub fingerprint: [u8; 20],
    /// token from the bridge indicating it was reached
    bridge_token: Option<BridgeToken>,
    // proof of Lox cred with level >= 3 and this bridge
    lox_proof: lox_pr::Request,
    /// user's country code, may be an empty string
    pub country: String,
    /// today's Julian date
    pub date: u32,
}

impl PositiveReport {
    pub fn new(
        bridge_id: [u8; 20],
        bridge_token: Option<BridgeToken>,
        lox_proof: lox_pr::Request,
        country: String,
    ) -> Self {
        if CONFIG.require_bridge_token && bridge_token.is_none() {
            panic!("Bridge tokens are required for positive reports.");
        }
        let mut hasher = Sha1::new();
        hasher.update(bridge_id);
        let fingerprint: [u8; 20] = hasher.finalize().into();
        let date = get_date();
        Self {
            fingerprint,
            bridge_token,
            lox_proof,
            country,
            date,
        }
    }

    pub fn from_lox_credential(
        bridge_id: [u8; 20],
        bridge_token: Option<BridgeToken>,
        lox_cred: &Lox,
        lox_pub: &IssuerPubKey,
        country: String,
    ) -> Self {
        let lox_proof = lox_pr::request(lox_cred, lox_pub).unwrap();
        PositiveReport::new(bridge_id, bridge_token, lox_proof, country)
    }

    /// Convert report to a serializable version
    pub fn to_serializable_report(self) -> SerializablePositiveReport {
        SerializablePositiveReport {
            fingerprint: self.fingerprint,
            bridge_token: self.bridge_token,
            lox_proof: self.lox_proof,
            country: self.country,
            date: self.date,
        }
    }

    /// Serializes the report, eliding the underlying process
    pub fn to_json(self) -> String {
        serde_json::to_string(&self.to_serializable_report()).unwrap()
    }

    /// Deserializes the report, eliding the underlying process
    pub fn from_json(str: String) -> Result<Self, PositiveReportError> {
        match serde_json::from_str::<SerializablePositiveReport>(&str) {
            Ok(v) => v.to_report(),
            Err(_) => Err(PositiveReportError::FailedToDeserialize),
        }
    }

    /// Verify everything except the Lox proof.
    /// Parameters:
    ///   - The bucket ID for the bucket containing this bridge
    ///   - The bridge verifying key for this bridge
    /// These parameters are assumed to be correct and are NOT checked against
    /// the fingerprint listed in the report.
    pub fn verify_excluding_lox_proof(
        self,
        bucket: Scalar,
        bridge_key: Option<VerifyingKey>,
    ) -> bool {
        // Verify bridge token
        if CONFIG.require_bridge_token {
            let bridge_token = self.bridge_token.unwrap();
            if bridge_key.is_none() {
                return false;
            }
            if bridge_key
                .unwrap()
                .verify(
                    &bincode::serialize(&bridge_token.unsigned_bridge_token).unwrap(),
                    &bridge_token.sig,
                )
                .is_err()
            {
                return false;
            }
        }
        // Verify knowledge of bucket ID
        let H = self.lox_proof.H;
        let BP = self.lox_proof.BP;
        if bucket * H != BP {
            return false;
        }
        true
    }
}

/// (De)serializable positive report object which must be consumed by the
/// checking function before it can be used
#[derive(Deserialize, Serialize)]
pub struct SerializablePositiveReport {
    pub fingerprint: [u8; 20],
    bridge_token: Option<BridgeToken>,
    lox_proof: lox_pr::Request,
    pub country: String,
    pub date: u32,
}

impl SerializablePositiveReport {
    pub fn to_report(self) -> Result<PositiveReport, PositiveReportError> {
        if CONFIG.require_bridge_token && self.bridge_token.is_none() {
            return Err(PositiveReportError::MissingBridgeToken);
        }
        if self.country == "" {
            return Err(PositiveReportError::MissingCountryCode);
        }
        if !COUNTRY_CODES.contains(self.country.as_str()) {
            return Err(PositiveReportError::InvalidCountryCode);
        }
        if self.date > get_date().into() {
            return Err(PositiveReportError::DateInFuture);
        }
        Ok(PositiveReport {
            fingerprint: self.fingerprint,
            bridge_token: self.bridge_token,
            lox_proof: self.lox_proof,
            country: self.country,
            date: self.date,
        })
    }
}

/// An unsigned token which indicates that the bridge was reached
#[derive(Serialize, Deserialize)]
pub struct UnsignedBridgeToken {
    /// hashed fingerprint (SHA-1 hash of 20-byte bridge ID)
    pub fingerprint: [u8; 20],
    /// client's country code
    pub country: String,
    /// today's Julian date
    pub date: u32,
}

impl UnsignedBridgeToken {
    pub fn new(bridge_id: [u8; 20], country: String) -> Self {
        let mut hasher = Sha1::new();
        hasher.update(bridge_id);
        let fingerprint: [u8; 20] = hasher.finalize().into();
        let date = get_date();
        Self {
            fingerprint,
            country,
            date,
        }
    }
}

/// A signed token which indicates that the bridge was reached
#[derive(Serialize, Deserialize)]
pub struct BridgeToken {
    /// the unsigned version of this token
    pub unsigned_bridge_token: UnsignedBridgeToken,
    /// signature from bridge's ed25519 key
    pub sig: Signature,
}

impl BridgeToken {
    pub fn new(unsigned_bridge_token: UnsignedBridgeToken, keypair: SigningKey) -> Self {
        let sig = keypair.sign(&bincode::serialize(&unsigned_bridge_token).unwrap());
        Self {
            unsigned_bridge_token,
            sig,
        }
    }
}