Michael Kuc
86af080ba6
Currently doesn't return any valid result, hence host believes device failed to register, however, insecure storage of keys does occur.
110 lines
3.6 KiB
C++
110 lines
3.6 KiB
C++
#include "U2F_Register_APDU.hpp"
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#include <exception>
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#include <cstring>
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#include "micro-ecc/uECC.h"
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#include "Certificates.hpp"
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#include <mbedtls/sha256.h>
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#include <iostream>
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using namespace std;
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U2F_Register_APDU::U2F_Register_APDU(const U2F_Msg_CMD &msg, const vector<uint8_t> &data)
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: U2F_Msg_CMD{ msg }
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{
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if (data.size() != 64)
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throw runtime_error{ "Incorrect registration size" };
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else if (p1 != 0x00 || p2 != 0x00)
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{
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cerr << "p1: " << static_cast<uint32_t>(p1) << ", p2: " << static_cast<uint32_t>(p2) << endl;
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//throw runtime_error{ "Invalid APDU parameters" };
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}
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copy(data.data() + 0, data.data() + 32, challengeP.begin());
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copy(data.data() + 32, data.data() + 64, appP.begin());
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//Use crypto lib to generate keypair
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uint8_t pub[65];
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uint8_t priv[32];
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//Unsure if necessary
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//From github.com/pratikd650/Teensy_U2F/blob/master/Teensy_U2F.cpp
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pub[0] = 0x04;
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uECC_make_key(pub + 1, priv, uECC_secp256r1());
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Storage::PrivKey privKey{};
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copy(priv, end(priv), privKey.begin());
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Storage::PubKey pubKey;
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copy(pub, end(pub), pubKey.begin());
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this->keyH = Storage::appParams.size();
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Storage::appParams[this->keyH] = appP;
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Storage::privKeys[this->keyH] = privKey;
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Storage::pubKeys[this->keyH] = pubKey;
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}
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//Ripped from https://github.com/pratikd650/Teensy_U2F/blob/master/Teensy_U2F.cpp
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void appendSignatureAsDER(vector<uint8_t> &response, const array<uint8_t, 64> &signature) {
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response.push_back(0x30); // Start of ASN.1 SEQUENCE
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response.push_back(68); //total length from (2 * (32 + 2)) to (2 * (33 + 2))
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auto &count = response.back();
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// Loop twice - for R and S
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for(unsigned int i = 0; i < 2; i++) {
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unsigned int sigOffs = i * 32;
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response.push_back(0x02); //header: integer
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response.push_back(32); //32 byte
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if (signature[sigOffs] > 0x7f) { // Integer needs to be represented in 2's completement notion
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response.back()++;
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response.push_back(0); // add leading 0, to indicate it is a positive number
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count++;
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}
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copy(signature.begin() + sigOffs, signature.begin() + sigOffs + 32, back_inserter(response)); //R or S value
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}
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}
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void U2F_Register_APDU::respond()
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{
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const auto appParam = Storage::appParams[this->keyH];
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const auto pubKey = Storage::pubKeys[this->keyH];
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const auto privKey = Storage::privKeys[this->keyH];
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vector<uint8_t> response;
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response.push_back(0x05);
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copy(pubKey.begin(), pubKey.end(), back_inserter(response));
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response.push_back(sizeof(this->keyH));
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auto fakeKeyHBytes = reinterpret_cast<uint8_t *>(&this->keyH);
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copy(fakeKeyHBytes, fakeKeyHBytes + 4, back_inserter(response));
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copy(attestCert, end(attestCert), back_inserter(response));
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//Gen signature
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array<uint8_t, 32> digest;
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{
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mbedtls_sha256_context shaContext;
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mbedtls_sha256_init(&shaContext);
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mbedtls_sha256_starts(&shaContext, 0);
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uint8_t byteReserved = 0;
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mbedtls_sha256_update(&shaContext, reinterpret_cast<unsigned char*>(&byteReserved), 1);
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mbedtls_sha256_update(&shaContext, reinterpret_cast<const unsigned char*>(appParam.data()), appParam.size());
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mbedtls_sha256_update(&shaContext, reinterpret_cast<unsigned char*>(challengeP.data()), challengeP.size());
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mbedtls_sha256_update(&shaContext, reinterpret_cast<unsigned char*>(&keyH), sizeof(keyH));
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mbedtls_sha256_update(&shaContext, reinterpret_cast<const unsigned char*>(pubKey.data()), pubKey.size());
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mbedtls_sha256_finish(&shaContext, reinterpret_cast<unsigned char*>(digest.data()));
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mbedtls_sha256_free(&shaContext);
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}
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array<uint8_t, 64> signature;
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uECC_sign(attestPrivKey, digest.data(), digest.size(), signature.data(), uECC_secp256r1());
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//Append signature as DER
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appendSignatureAsDER(response, signature);
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}
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