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onionreq: reject truncated XChaCha20 ciphertexts #140

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onionreq: reject truncated XChaCha20 ciphertexts #140

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10 changes: 5 additions & 5 deletions src/onionreq/hop_encryption.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -211,17 +211,17 @@ std::vector<unsigned char> HopEncryption::encrypt_xchacha20(

std::vector<unsigned char> HopEncryption::decrypt_xchacha20(
std::vector<unsigned char> ciphertext_, const network::x25519_pubkey& pubKey) const {
if (ciphertext_.size() <
crypto_aead_xchacha20poly1305_ietf_NPUBBYTES + crypto_aead_xchacha20poly1305_ietf_ABYTES)
throw std::invalid_argument{
"Invalid ciphertext: too short to contain valid encrypted data"};

std::span<const unsigned char> ciphertext = to_span(ciphertext_);

// Extract nonce from the beginning of the ciphertext:
auto nonce = ciphertext.subspan(0, crypto_aead_xchacha20poly1305_ietf_NPUBBYTES);
ciphertext = ciphertext.subspan(nonce.size());

if (!response_long_enough(EncryptType::xchacha20, ciphertext_.size()))
throw std::invalid_argument{
"Ciphertext data is too short: " +
std::string(reinterpret_cast<const char*>(ciphertext_.data()))};

const auto key = xchacha20_shared_key(public_key_, private_key_, pubKey, !server_);

std::vector<unsigned char> plaintext;
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12 changes: 12 additions & 0 deletions tests/test_onionreq.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,18 @@ TEST_CASE("Onion request encryption", "[encryption][onionreq]") {
CHECK_THROWS(e.decrypt_aesgcm(enc_xchacha20_broken2, x25519_pubkey::from_bytes(A)));
CHECK_THROWS(e.decrypt_xchacha20(enc_xchacha20_broken1, x25519_pubkey::from_bytes(A)));
CHECK_THROWS(e.decrypt_xchacha20(enc_xchacha20_broken2, x25519_pubkey::from_bytes(A)));

auto enc_xchacha20_empty = e.encrypt_xchacha20({}, x25519_pubkey::from_bytes(A));
CHECK(enc_xchacha20_empty.size() == 24 + 16);
CHECK(e.decrypt_xchacha20(enc_xchacha20_empty, x25519_pubkey::from_bytes(A)).empty());

for (size_t size : {0, 1, 15, 16, 23, 24, 39}) {
INFO("ciphertext size: " << size);
CHECK_THROWS_AS(
e.decrypt_xchacha20(
std::vector<unsigned char>(size, 0x41), x25519_pubkey::from_bytes(A)),
std::invalid_argument);
}
}

TEST_CASE("Onion request parser", "[onionreq][parser]") {
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