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LibTLS: Add support for AEAD cipher suites
And integrate AES-GCM.
This commit is contained in:
AnotherTest
Andreas Kling
parent
d3c52cef86
commit
1172746633
4 changed files with 253 additions and 85 deletions
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@ -26,6 +26,7 @@
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#include <AK/Endian.h>
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#include <AK/MemoryStream.h>
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#include <LibCore/Timer.h>
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#include <LibCrypto/ASN1/DER.h>
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#include <LibCrypto/PK/Code/EMSA_PSS.h>
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@ -68,14 +69,23 @@ void TLSv12::update_packet(ByteBuffer& packet)
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}
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}
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if (m_context.cipher_spec_set && m_context.crypto.created) {
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size_t length = packet.size() - header_size + mac_length();
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auto block_size = m_aes_local->cipher().block_size();
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// If the length is already a multiple a block_size,
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// an entire block of padding is added.
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// In short, we _never_ have no padding.
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size_t padding = block_size - length % block_size;
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length += padding;
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size_t mac_size = mac_length();
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size_t length = packet.size() - header_size;
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size_t block_size, padding, mac_size;
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if (!is_aead()) {
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block_size = m_aes_local.cbc->cipher().block_size();
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// If the length is already a multiple a block_size,
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// an entire block of padding is added.
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// In short, we _never_ have no padding.
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padding = block_size - length % block_size;
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length += padding;
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mac_size = mac_length();
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length += mac_size;
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} else {
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block_size = m_aes_local.gcm->cipher().block_size();
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padding = 0;
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mac_size = 0; // AEAD provides its own authentication scheme.
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}
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if (m_context.crypto.created == 1) {
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// `buffer' will continue to be encrypted
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@ -83,41 +93,93 @@ void TLSv12::update_packet(ByteBuffer& packet)
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size_t buffer_position = 0;
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auto iv_size = iv_length();
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// We need enough space for a header, iv_length bytes of IV and whatever the packet contains
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auto ct = ByteBuffer::create_uninitialized(length + header_size + iv_size);
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// copy the header over
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ct.overwrite(0, packet.data(), header_size - 2);
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// copy the packet, sans the header
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buffer.overwrite(buffer_position, packet.offset_pointer(header_size), packet.size() - header_size);
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buffer_position += packet.size() - header_size;
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// get the appropricate HMAC value for the entire packet
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auto mac = hmac_message(packet, {}, mac_size, true);
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ByteBuffer ct;
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// write the MAC
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buffer.overwrite(buffer_position, mac.data(), mac.size());
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buffer_position += mac.size();
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if (is_aead()) {
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// We need enough space for a header, the data, a tag, and the IV
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ct = ByteBuffer::create_uninitialized(length + header_size + iv_size + 16);
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// Apply the padding (a packet MUST always be padded)
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memset(buffer.offset_pointer(buffer_position), padding - 1, padding);
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buffer_position += padding;
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// copy the header over
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ct.overwrite(0, packet.data(), header_size - 2);
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ASSERT(buffer_position == buffer.size());
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// AEAD AAD (13)
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// Seq. no (8)
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// content type (1)
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// version (2)
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// length (2)
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u8 aad[13];
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Bytes aad_bytes { aad, 13 };
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OutputMemoryStream aad_stream { aad_bytes };
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auto iv = ByteBuffer::create_uninitialized(iv_size);
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AK::fill_with_random(iv.data(), iv.size());
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u64 seq_no = AK::convert_between_host_and_network_endian(m_context.local_sequence_number);
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u16 len = AK::convert_between_host_and_network_endian((u16)(packet.size() - header_size));
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// write it into the ciphertext portion of the message
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ct.overwrite(header_size, iv.data(), iv.size());
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aad_stream.write({ &seq_no, sizeof(seq_no) });
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aad_stream.write(packet.bytes().slice(0, 3)); // content-type + version
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aad_stream.write({ &len, sizeof(len) }); // length
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ASSERT(aad_stream.is_end());
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ASSERT(header_size + iv_size + length == ct.size());
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ASSERT(length % block_size == 0);
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// AEAD IV (12)
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// IV (4)
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// (Nonce) (8)
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// -- Our GCM impl takes 16 bytes
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// zero (4)
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u8 iv[16];
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Bytes iv_bytes { iv, 16 };
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Bytes { m_context.crypto.local_aead_iv, 4 }.copy_to(iv_bytes);
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AK::fill_with_random(iv_bytes.offset(4), 8);
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memset(iv_bytes.offset(12), 0, 4);
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// get a block to encrypt into
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auto view = ct.bytes().slice(header_size + iv_size, length);
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m_aes_local->encrypt(buffer, view, iv);
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// write the random part of the iv out
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iv_bytes.slice(4, 8).copy_to(ct.bytes().slice(header_size));
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// Write the encrypted data and the tag
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m_aes_local.gcm->encrypt(
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packet.bytes().slice(header_size, length),
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ct.bytes().slice(header_size + 8, length),
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iv_bytes,
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aad_bytes,
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ct.bytes().slice(header_size + 8 + length, 16));
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ASSERT(header_size + 8 + length + 16 == ct.size());
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} else {
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// We need enough space for a header, iv_length bytes of IV and whatever the packet contains
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ct = ByteBuffer::create_uninitialized(length + header_size + iv_size);
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// copy the header over
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ct.overwrite(0, packet.data(), header_size - 2);
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// get the appropricate HMAC value for the entire packet
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auto mac = hmac_message(packet, {}, mac_size, true);
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// write the MAC
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buffer.overwrite(buffer_position, mac.data(), mac.size());
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buffer_position += mac.size();
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// Apply the padding (a packet MUST always be padded)
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memset(buffer.offset_pointer(buffer_position), padding - 1, padding);
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buffer_position += padding;
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ASSERT(buffer_position == buffer.size());
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auto iv = ByteBuffer::create_uninitialized(iv_size);
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AK::fill_with_random(iv.data(), iv.size());
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// write it into the ciphertext portion of the message
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ct.overwrite(header_size, iv.data(), iv.size());
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ASSERT(header_size + iv_size + length == ct.size());
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ASSERT(length % block_size == 0);
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// get a block to encrypt into
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auto view = ct.bytes().slice(header_size + iv_size, length);
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m_aes_local.cbc->encrypt(buffer, view, iv);
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}
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// store the correct ciphertext length into the packet
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u16 ct_length = (u16)ct.size() - header_size;
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@ -211,50 +273,116 @@ ssize_t TLSv12::handle_message(const ByteBuffer& buffer)
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print_buffer(buffer.slice_view(header_size, length));
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#endif
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ASSERT(m_aes_remote);
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auto iv_size = iv_length();
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if (is_aead()) {
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ASSERT(m_aes_remote.gcm);
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auto decrypted = m_aes_remote->create_aligned_buffer(length - iv_size);
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auto iv = buffer.slice_view(header_size, iv_size);
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if (length < 24) {
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dbg() << "Invalid packet length";
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auto packet = build_alert(true, (u8)AlertDescription::DecryptError);
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write_packet(packet);
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return (i8)Error::BrokenPacket;
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}
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Bytes decrypted_span = decrypted;
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m_aes_remote->decrypt(buffer.bytes().slice(header_size + iv_size, length - iv_size), decrypted_span, iv);
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auto packet_length = length - iv_length() - 16;
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auto payload = plain.bytes();
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auto decrypted = ByteBuffer::create_uninitialized(packet_length);
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length = decrypted_span.size();
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// AEAD AAD (13)
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// Seq. no (8)
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// content type (1)
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// version (2)
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// length (2)
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u8 aad[13];
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Bytes aad_bytes { aad, 13 };
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OutputMemoryStream aad_stream { aad_bytes };
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u64 seq_no = AK::convert_between_host_and_network_endian(m_context.remote_sequence_number);
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u16 len = AK::convert_between_host_and_network_endian((u16)packet_length);
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aad_stream.write({ &seq_no, sizeof(seq_no) }); // Sequence number
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aad_stream.write(buffer.bytes().slice(0, header_size - 2)); // content-type + version
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aad_stream.write({ &len, sizeof(u16) });
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ASSERT(aad_stream.is_end());
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auto nonce = payload.slice(0, iv_length());
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payload = payload.slice(iv_length());
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// AEAD IV (12)
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// IV (4)
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// (Nonce) (8)
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// -- Our GCM impl takes 16 bytes
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// zero (4)
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u8 iv[16];
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Bytes iv_bytes { iv, 16 };
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Bytes { m_context.crypto.remote_aead_iv, 4 }.copy_to(iv_bytes);
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nonce.copy_to(iv_bytes.slice(4));
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memset(iv_bytes.offset(12), 0, 4);
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auto ciphertext = payload.slice(0, payload.size() - 16);
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auto tag = payload.slice(ciphertext.size());
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auto consistency = m_aes_remote.gcm->decrypt(
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ciphertext,
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decrypted,
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iv_bytes,
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aad_bytes,
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tag);
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if (consistency != Crypto::VerificationConsistency::Consistent) {
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dbg() << "integrity check failed (tag length " << tag.size() << ")";
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auto packet = build_alert(true, (u8)AlertDescription::BadRecordMAC);
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write_packet(packet);
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return (i8)Error::IntegrityCheckFailed;
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}
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plain = decrypted;
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} else {
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ASSERT(m_aes_remote.cbc);
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auto iv_size = iv_length();
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auto decrypted = m_aes_remote.cbc->create_aligned_buffer(length - iv_size);
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auto iv = buffer.slice_view(header_size, iv_size);
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Bytes decrypted_span = decrypted;
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m_aes_remote.cbc->decrypt(buffer.bytes().slice(header_size + iv_size, length - iv_size), decrypted_span, iv);
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length = decrypted_span.size();
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#ifdef TLS_DEBUG
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dbg() << "Decrypted: ";
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print_buffer(decrypted);
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dbg() << "Decrypted: ";
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print_buffer(decrypted);
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#endif
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auto mac_size = mac_length();
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if (length < mac_size) {
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dbg() << "broken packet";
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auto packet = build_alert(true, (u8)AlertDescription::DecryptError);
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write_packet(packet);
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return (i8)Error::BrokenPacket;
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auto mac_size = mac_length();
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if (length < mac_size) {
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dbg() << "broken packet";
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auto packet = build_alert(true, (u8)AlertDescription::DecryptError);
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write_packet(packet);
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return (i8)Error::BrokenPacket;
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}
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length -= mac_size;
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const u8* message_hmac = decrypted_span.offset(length);
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u8 temp_buf[5];
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memcpy(temp_buf, buffer.offset_pointer(0), 3);
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*(u16*)(temp_buf + 3) = AK::convert_between_host_and_network_endian(length);
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auto hmac = hmac_message({ temp_buf, 5 }, decrypted_span.slice(0, length), mac_size);
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auto message_mac = ByteBuffer::wrap(const_cast<u8*>(message_hmac), mac_size);
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if (hmac != message_mac) {
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dbg() << "integrity check failed (mac length " << mac_size << ")";
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dbg() << "mac received:";
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print_buffer(message_mac);
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dbg() << "mac computed:";
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print_buffer(hmac);
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auto packet = build_alert(true, (u8)AlertDescription::BadRecordMAC);
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write_packet(packet);
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return (i8)Error::IntegrityCheckFailed;
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}
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plain = decrypted.slice(0, length);
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}
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length -= mac_size;
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const u8* message_hmac = decrypted_span.offset(length);
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u8 temp_buf[5];
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memcpy(temp_buf, buffer.offset_pointer(0), 3);
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*(u16*)(temp_buf + 3) = AK::convert_between_host_and_network_endian(length);
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auto hmac = hmac_message({ temp_buf, 5 }, decrypted_span.slice(0, length), mac_size);
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auto message_mac = ByteBuffer::wrap(const_cast<u8*>(message_hmac), mac_size);
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if (hmac != message_mac) {
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dbg() << "integrity check failed (mac length " << mac_size << ")";
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dbg() << "mac received:";
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print_buffer(message_mac);
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dbg() << "mac computed:";
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print_buffer(hmac);
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auto packet = build_alert(true, (u8)AlertDescription::BadRecordMAC);
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write_packet(packet);
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return (i8)Error::IntegrityCheckFailed;
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}
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plain = decrypted.slice(0, length);
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}
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m_context.remote_sequence_number++;
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