lib-privatebin/src/json_parser.cpp

#include "json_parser.h"
#include <iostream>
#include <chrono>
#include <cryptopp/base64.h>
#include <cryptopp/filters.h>
#include <cryptopp/queue.h>

// Helper: Base64 encode without line breaks
static std::string encode_base64(const std::vector<unsigned char>& data) {
    std::string result;
    CryptoPP::StringSource ss(
        data.data(), data.size(), true,
        new CryptoPP::Base64Encoder(new CryptoPP::StringSink(result), false /* insertLineBreaks */)
    );
    return result;
}

// Helper: Base64 decode
static std::vector<unsigned char> decode_base64(const std::string& b64) {
    std::string decoded;
    CryptoPP::StringSource ss(
        b64, true, new CryptoPP::Base64Decoder(new CryptoPP::StringSink(decoded))
    );
    return std::vector<unsigned char>(decoded.begin(), decoded.end());
}

json JsonParser::create_paste_json(const std::vector<unsigned char>& cipher_text,
                                 const std::vector<unsigned char>& auth_tag,
                                 const std::vector<unsigned char>& iv,
                                 const std::vector<unsigned char>& salt,
                                 const std::string& expiration,
                                 const std::string& format,
                                 bool burn_after_reading,
                                 bool open_discussion) {
    
    // Convert binary data to base64 strings
    std::string cipher_text_b64 = encode_base64(cipher_text);
    std::string iv_b64 = encode_base64(iv);
    std::string salt_b64 = encode_base64(salt);
    
    // Get current timestamp
    auto now = std::chrono::duration_cast<std::chrono::seconds>(
        std::chrono::system_clock::now().time_since_epoch()).count();
    
    // Create the metadata array according to PrivateBin v2
    json metadata = {
        {
            iv_b64,           // base64(cipher_iv)
            salt_b64,         // base64(kdf_salt)
            100000,           // iterations
            256,              // key size
            128,              // tag size
            "aes",            // cipher
            "gcm",            // mode
            "zlib"            // compression
        },
        format,               // formatter key
        burn_after_reading ? 1 : 0,  // burn after reading
        open_discussion ? 1 : 0      // open discussion
    };
    
    // Create the main JSON structure
    // JSON close to v1.3 JSON-LD: meta.expire used by server
    json paste_json = {
        {"v", 2},                 // version
        {"adata", metadata},      // metadata
        {"ct", cipher_text_b64},  // ciphertext (base64)
        {"meta", {
            {"expire", expiration}
        }}
    };
    
    return paste_json;
}

bool JsonParser::parse_paste_json(const json& json_data,
                                std::vector<unsigned char>& cipher_text,
                                std::vector<unsigned char>& auth_tag,
                                std::vector<unsigned char>& iv,
                                std::vector<unsigned char>& salt,
                                std::string& expiration) {
    
    try {
        // Extract and decode cipher text
        std::string ct_b64 = json_data.at("ct");
        cipher_text = decode_base64(ct_b64);
        
        // Optional explicit tag field
        if (json_data.contains("tag")) {
            std::string tag_b64 = json_data.at("tag");
            auth_tag = decode_base64(tag_b64);
        } else {
            auth_tag.clear();
        }
        
        // Extract metadata and decode IV & salt
        json adata = json_data.at("adata");
        if (adata.size() >= 1) {
            json first_element = adata[0];
            if (first_element.is_array() && first_element.size() >= 2) {
                std::string iv_b64 = first_element[0];
                std::string salt_b64 = first_element[1];
                iv = decode_base64(iv_b64);
                salt = decode_base64(salt_b64);
            }
        }
        
        // Extract expiration; servers may return either meta.expire (string)
        // or meta.time_to_live (integer seconds). Both are optional for our use.
        try {
            expiration = json_data.at("meta").at("expire");
        } catch (...) {
            try {
                auto ttl = json_data.at("meta").at("time_to_live").get<int>();
                expiration = std::to_string(ttl);
            } catch (...) {
                expiration.clear();
            }
        }
        
        return true;
    } catch (...) {
        return false;
    }
}

bool JsonParser::parse_response(const std::string& response,
                              int& status,
                              std::string& message,
                              std::string& paste_id,
                              std::string& url,
                              std::string& delete_token) {
    
    try {
        json json_response = json::parse(response);
        status = json_response.value("status", 1);
        if (status == 0) {
            paste_id = json_response.value("id", "");
            url = json_response.value("url", "");
            delete_token = json_response.value("deletetoken", "");
        } else {
            message = json_response.value("message", "");
        }
        
        return true;
    } catch (...) {
        return false;
    }
}