troll-patrol/src/negative_report.rs

use crate::{get_date, COUNTRY_CODES};

use curve25519_dalek::scalar::Scalar;
use lox_library::{bridge_table::BridgeLine, cred::Lox};

use serde::{Deserialize, Serialize};
use sha1::{Digest, Sha1};
use sha3::Sha3_256;

#[derive(Debug)]
pub enum NegativeReportError {
    DateInFuture,
    FailedToDeserialize, // couldn't deserialize to SerializableNegativeReport
    InvalidCountryCode,
}

/// A report that the user was unable to connect to the bridge
pub struct NegativeReport {
    /// hashed fingerprint (SHA-1 hash of 20-byte bridge ID)
    pub fingerprint: [u8; 20],
    /// some way to prove knowledge of bridge
    bridge_pok: ProofOfBridgeKnowledge,
    /// user's country code, may be an empty string
    pub country: String,
    /// today's Julian date
    pub date: u32,
}

impl NegativeReport {
    pub fn new(bridge_id: [u8; 20], bridge_pok: ProofOfBridgeKnowledge, 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,
            bridge_pok,
            country,
            date,
        }
    }

    pub fn from_bridgeline(bridge_id: [u8; 20], bridgeline: BridgeLine, country: String) -> Self {
        let bridge_pok =
            ProofOfBridgeKnowledge::HashOfBridgeLine(HashOfBridgeLine::new(&bridgeline));
        NegativeReport::new(bridge_id, bridge_pok, country)
    }

    pub fn from_bucket(bridge_id: [u8; 20], bucket: Scalar, country: String) -> Self {
        let mut hasher = Sha3_256::new();
        hasher.update(bucket.to_bytes());
        let bucket_hash: [u8; 32] = hasher.finalize().into();
        let bridge_pok = ProofOfBridgeKnowledge::HashOfBucket(HashOfBucket { hash: bucket_hash });
        NegativeReport::new(bridge_id, bridge_pok, country)
    }

    pub fn from_lox_credential(bridge_id: [u8; 20], cred: Lox, country: String) -> Self {
        NegativeReport::from_bucket(bridge_id, cred.bucket, country)
    }

    /// Convert report to a serializable version
    pub fn to_serializable_report(self) -> SerializableNegativeReport {
        SerializableNegativeReport {
            fingerprint: self.fingerprint,
            bridge_pok: self.bridge_pok,
            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, NegativeReportError> {
        match serde_json::from_str::<SerializableNegativeReport>(&str) {
            Ok(v) => v.to_report(),
            Err(_) => Err(NegativeReportError::FailedToDeserialize),
        }
    }

    /// Verify report if proof of bridge knowledge is bridge line hash
    pub fn verify_with_hash_of_bridge_line(self, bl: &BridgeLine) -> bool {
        match self.bridge_pok {
            ProofOfBridgeKnowledge::HashOfBridgeLine(pok) => {
                let hash = HashOfBridgeLine::new(bl);
                hash == pok
            },
            _ => false,
        }
    }

    /// Verify report if proof of bridge knowledge is bucket hash
    pub fn verify_with_hash_of_bucket(self, bucket: &Scalar) -> bool {
        match self.bridge_pok {
            ProofOfBridgeKnowledge::HashOfBucket(pok) => {
                let hash = HashOfBucket::new(bucket);
                hash == pok
            },
            _ => false,
        }
    }
}

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

impl SerializableNegativeReport {
    pub fn to_report(self) -> Result<NegativeReport, NegativeReportError> {
        if self.country != "" && !COUNTRY_CODES.contains(self.country.as_str()) {
            return Err(NegativeReportError::InvalidCountryCode);
        }
        if self.date > get_date().into() {
            return Err(NegativeReportError::DateInFuture);
        }
        Ok(NegativeReport {
            fingerprint: self.fingerprint,
            bridge_pok: self.bridge_pok,
            country: self.country.to_string(),
            date: self.date.try_into().unwrap(),
        })
    }
}

/// Proof that the user knows (and should be able to access) a given bridge
#[derive(Serialize, Deserialize)]
pub enum ProofOfBridgeKnowledge {
    /// Hash of bridge line as proof of knowledge of bridge line
    HashOfBridgeLine(HashOfBridgeLine),
    /// Hash of bucket ID for Lox user
    HashOfBucket(HashOfBucket),
}

/// Hash of bridge line to prove knowledge of that bridge
#[derive(PartialEq, Serialize, Deserialize)]
pub struct HashOfBridgeLine {
    hash: [u8; 32],
}

impl HashOfBridgeLine {
    pub fn new(bl: &BridgeLine) -> Self {
        let mut hasher = Sha3_256::new();
        hasher.update(bincode::serialize(&bl).unwrap());
        let hash: [u8; 32] = hasher.finalize().into();
        Self { hash }
    }
}

/// Hash of bucket ID to prove knowledge of bridges in that bucket
#[derive(PartialEq, Serialize, Deserialize)]
pub struct HashOfBucket {
    hash: [u8; 32],
}

impl HashOfBucket {
    pub fn new(bucket: &Scalar) -> Self {
        let mut hasher = Sha3_256::new();
        hasher.update(bucket.to_bytes());
        let hash: [u8; 32] = hasher.finalize().into();
        Self { hash }
    }
}