troll-patrol/src/positive_report.rs

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

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

use curve25519_dalek::{RistrettoPoint, 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 sha2::Sha512;
use std::option::Option;

#[derive(Debug)]
pub enum PositiveReportError {
    DateInFuture,
    FailedToDeserialize, // couldn't deserialize to SerializablePositiveReport
    InvalidBridgeToken,
    InvalidCountryCode,
    InvalidLoxProof,
    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 {
        let bridge_token = if self.bridge_token.is_none() {
            None
        } else {
            Some(self.bridge_token.unwrap().to_serializable_bridge_token())
        };
        SerializablePositiveReport {
            fingerprint: self.fingerprint,
            bridge_token: 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 (if bridge token is required)
    /// 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(
                    &bridge_token.unsigned_bridge_token.to_bincode(),
                    &bridge_token.sig,
                )
                .is_err()
            {
                return false;
            }
        }
        // Verify knowledge of bucket ID
        let H = RistrettoPoint::hash_from_bytes::<Sha512>(
            format!("{}{}", lox_pr::H_GENERATOR_STRING, self.lox_proof.date).as_bytes(),
        );
        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<SerializableBridgeToken>,
    lox_proof: lox_pr::Request,
    pub country: String,
    pub date: u32,
}

impl SerializablePositiveReport {
    pub fn to_report(self) -> Result<PositiveReport, PositiveReportError> {
        // Check that fields are valid
        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);
        }
        let date: u32 = get_date().into();
        if self.date > date {
            return Err(PositiveReportError::DateInFuture);
        }
        if self.lox_proof.date != date {
            return Err(PositiveReportError::InvalidLoxProof);
        }
        let bridge_token = if self.bridge_token.is_none() {
            None
        } else {
            let bridge_token_unchecked = self.bridge_token.unwrap().to_bridge_token()?;
            // Check that bridge token fields match report fields...
            // The user may override the bridge's autodetected country code,
            // so allow the country code to be different.
            if self.fingerprint != bridge_token_unchecked.unsigned_bridge_token.fingerprint
                || self.date != bridge_token_unchecked.unsigned_bridge_token.date
            {
                return Err(PositiveReportError::InvalidBridgeToken);
            }
            Some(bridge_token_unchecked)
        };
        Ok(PositiveReport {
            fingerprint: self.fingerprint,
            bridge_token: bridge_token,
            lox_proof: self.lox_proof,
            country: self.country,
            date: self.date,
        })
    }
}

/// An unsigned token which indicates that the bridge was reached
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,
        }
    }

    pub fn to_serializable_unsigned_bridge_token(self) -> SerializableUnsignedBridgeToken {
        SerializableUnsignedBridgeToken {
            fingerprint: self.fingerprint,
            country: self.country,
            date: self.date,
        }
    }

    /// Serializes the token, eliding the underlying process
    pub fn to_bincode(self) -> Vec<u8> {
        bincode::serialize(&self.to_serializable_unsigned_bridge_token()).unwrap()
    }

    /// Deserializes the token, eliding the underlying process
    pub fn from_bincode(vec: Vec<u8>) -> Result<Self, PositiveReportError> {
        match bincode::deserialize::<SerializableUnsignedBridgeToken>(&vec[..]) {
            Ok(v) => v.to_unsigned_bridge_token(),
            Err(_) => Err(PositiveReportError::FailedToDeserialize),
        }
    }
}

/// (De)serializable unsigned bridge token object which must be consumed by the
/// checking function before it can be used
#[derive(Serialize, Deserialize)]
pub struct SerializableUnsignedBridgeToken {
    pub fingerprint: [u8; 20],
    pub country: String,
    pub date: u32,
}

impl SerializableUnsignedBridgeToken {
    pub fn to_unsigned_bridge_token(self) -> Result<UnsignedBridgeToken, PositiveReportError> {
        if self.country == ""
            || !COUNTRY_CODES.contains(self.country.as_str())
            || self.date > get_date().into()
        {
            return Err(PositiveReportError::InvalidBridgeToken);
        }
        Ok(UnsignedBridgeToken {
            fingerprint: self.fingerprint,
            country: self.country,
            date: self.date,
        })
    }
}

/// A signed token which indicates that the bridge was reached
pub struct BridgeToken {
    /// the unsigned version of this token
    pub unsigned_bridge_token: UnsignedBridgeToken,

    /// signature from bridge's ed25519 key
    sig: Signature,
}

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

    /// Convert bridge token to a serializable version
    pub fn to_serializable_bridge_token(self) -> SerializableBridgeToken {
        SerializableBridgeToken {
            unsigned_bridge_token: self
                .unsigned_bridge_token
                .to_serializable_unsigned_bridge_token(),
            sig: self.sig,
        }
    }

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

    /// Deserializes the bridge token, eliding the underlying process
    pub fn from_json(str: String) -> Result<Self, PositiveReportError> {
        match serde_json::from_str::<SerializableBridgeToken>(&str) {
            Ok(v) => v.to_bridge_token(),
            Err(_) => Err(PositiveReportError::InvalidBridgeToken),
        }
    }
}

/// (De)serializable bridge token object which must be consumed by the
/// checking function before it can be used
#[derive(Serialize, Deserialize)]
pub struct SerializableBridgeToken {
    pub unsigned_bridge_token: SerializableUnsignedBridgeToken,
    sig: Signature,
}

impl SerializableBridgeToken {
    pub fn to_bridge_token(self) -> Result<BridgeToken, PositiveReportError> {
        let unsigned_bridge_token = self.unsigned_bridge_token.to_unsigned_bridge_token()?;
        Ok(BridgeToken {
            unsigned_bridge_token: unsigned_bridge_token,
            sig: self.sig,
        })
    }
}