Add encoder and decoder for PreKey messages
This commit is contained in:
parent
816435a860
commit
e44c82a7b4
4 changed files with 265 additions and 66 deletions
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@ -37,6 +37,7 @@ struct MessageWriter {
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struct MessageReader {
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std::uint8_t version;
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bool has_counter;
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std::uint32_t counter;
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std::uint8_t const * input; std::size_t input_length;
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std::uint8_t const * ratchet_key; std::size_t ratchet_key_length;
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@ -46,9 +47,8 @@ struct MessageReader {
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/**
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* Writes the message headers into the output buffer.
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* Returns a writer struct populated with pointers into the output buffer.
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* Populates the writer struct with pointers into the output buffer.
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*/
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void encode_message(
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MessageWriter & writer,
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std::uint8_t version,
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@ -62,13 +62,67 @@ void encode_message(
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/**
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* Reads the message headers from the input buffer.
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* Populates the reader struct with pointers into the input buffer.
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* On failure returns std::size_t(-1).
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*/
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std::size_t decode_message(
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void decode_message(
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MessageReader & reader,
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std::uint8_t const * input, std::size_t input_length,
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std::size_t mac_length
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);
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struct PreKeyMessageWriter {
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std::uint8_t * identity_key;
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std::uint8_t * base_key;
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std::uint8_t * message;
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};
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struct PreKeyMessageReader {
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std::uint8_t version;
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bool has_registration_id;
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bool has_one_time_key_id;
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std::uint32_t registration_id;
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std::uint32_t one_time_key_id;
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std::uint8_t const * identity_key; std::size_t identity_key_length;
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std::uint8_t const * base_key; std::size_t base_key_length;
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std::uint8_t const * message; std::size_t message_length;
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};
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/**
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* The length of the buffer needed to hold a message.
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*/
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std::size_t encode_one_time_key_message_length(
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std::uint32_t registration_id,
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std::uint32_t one_time_key_id,
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std::size_t identity_key_length,
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std::size_t base_key_length,
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std::size_t message_length
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);
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/**
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* Writes the message headers into the output buffer.
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* Populates the writer struct with pointers into the output buffer.
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*/
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void encode_one_time_key_message(
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PreKeyMessageWriter & writer,
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std::uint8_t version,
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std::uint32_t registration_id,
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std::uint32_t one_time_key_id,
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std::size_t identity_key_length,
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std::size_t base_key_length,
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std::size_t message_length,
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std::uint8_t * output
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);
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/**
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* Reads the message headers from the input buffer.
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* Populates the reader struct with pointers into the input buffer.
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*/
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void decode_one_time_key_message(
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PreKeyMessageReader & reader,
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std::uint8_t const * input, std::size_t input_length
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);
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} // namespace axolotl
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255
src/message.cpp
255
src/message.cpp
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@ -81,6 +81,82 @@ static std::uint8_t const RATCHET_KEY_TAG = 012;
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static std::uint8_t const COUNTER_TAG = 020;
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static std::uint8_t const CIPHERTEXT_TAG = 042;
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std::uint8_t * encode(
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std::uint8_t * pos,
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std::uint8_t tag,
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std::uint32_t value
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) {
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*(pos++) = tag;
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return varint_encode(pos, value);
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}
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std::uint8_t * encode(
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std::uint8_t * pos,
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std::uint8_t tag,
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std::uint8_t * & value, std::size_t value_length
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) {
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*(pos++) = tag;
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pos = varint_encode(pos, value_length);
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value = pos;
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return pos + value_length;
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}
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std::uint8_t const * decode(
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std::uint8_t const * pos, std::uint8_t const * end,
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std::uint8_t tag,
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std::uint32_t & value, bool & has_value
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) {
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if (pos != end && *pos == tag) {
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++pos;
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std::uint8_t const * value_start = pos;
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pos = varint_skip(pos, end);
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value = varint_decode<std::uint32_t>(value_start, pos);
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has_value = true;
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}
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return pos;
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}
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std::uint8_t const * decode(
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std::uint8_t const * pos, std::uint8_t const * end,
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std::uint8_t tag,
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std::uint8_t const * & value, std::size_t & value_length
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) {
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if (pos != end && *pos == tag) {
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++pos;
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std::uint8_t const * len_start = pos;
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pos = varint_skip(pos, end);
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std::size_t len = varint_decode<std::size_t>(len_start, pos);
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if (len > end - pos) return end;
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value = pos;
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value_length = len;
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pos += len;
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}
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return pos;
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}
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std::uint8_t const * skip_unknown(
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std::uint8_t const * pos, std::uint8_t const * end
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) {
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if (pos != end) {
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uint8_t tag = *pos;
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if (tag & 0x7 == 0) {
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pos = varint_skip(pos, end);
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pos = varint_skip(pos, end);
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} else if (tag & 0x7 == 2) {
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pos = varint_skip(pos, end);
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std::uint8_t const * len_start = pos;
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pos = varint_skip(pos, end);
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std::size_t len = varint_decode<std::size_t>(len_start, pos);
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if (len > end - pos) return end;
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pos += len;
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} else {
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return end;
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}
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}
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return pos;
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}
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} // namespace
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@ -109,75 +185,138 @@ void axolotl::encode_message(
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) {
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std::uint8_t * pos = output;
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*(pos++) = version;
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*(pos++) = COUNTER_TAG;
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pos = varint_encode(pos, counter);
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*(pos++) = RATCHET_KEY_TAG;
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pos = varint_encode(pos, ratchet_key_length);
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writer.ratchet_key = pos;
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pos += ratchet_key_length;
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*(pos++) = CIPHERTEXT_TAG;
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pos = varint_encode(pos, ciphertext_length);
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writer.ciphertext = pos;
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pos += ciphertext_length;
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pos = encode(pos, RATCHET_KEY_TAG, writer.ratchet_key, ratchet_key_length);
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pos = encode(pos, COUNTER_TAG, counter);
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pos = encode(pos, CIPHERTEXT_TAG, writer.ciphertext, ciphertext_length);
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}
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std::size_t axolotl::decode_message(
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void axolotl::decode_message(
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axolotl::MessageReader & reader,
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std::uint8_t const * input, std::size_t input_length,
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std::size_t mac_length
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) {
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std::uint8_t const * pos = input;
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std::uint8_t const * end = input + input_length - mac_length;
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std::uint8_t flags = 0;
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std::size_t result = std::size_t(-1);
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if (pos == end) return result;
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std::uint8_t const * unknown = NULL;
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if (pos == end) return;
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reader.version = *(pos++);
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reader.input = input;
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reader.input_length = input_length;
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reader.has_counter = false;
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reader.ratchet_key = NULL;
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reader.ciphertext = NULL;
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while (pos != end) {
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uint8_t tag = *(pos);
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if (tag == COUNTER_TAG) {
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++pos;
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std::uint8_t const * counter_start = pos;
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pos = varint_skip(pos, end);
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reader.counter = varint_decode<std::uint32_t>(counter_start, pos);
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flags |= 1;
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} else if (tag == RATCHET_KEY_TAG) {
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++pos;
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std::uint8_t const * len_start = pos;
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pos = varint_skip(pos, end);
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std::size_t len = varint_decode<std::size_t>(len_start, pos);
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if (len > end - pos) return result;
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reader.ratchet_key_length = len;
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reader.ratchet_key = pos;
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pos += len;
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flags |= 2;
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} else if (tag == CIPHERTEXT_TAG) {
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++pos;
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std::uint8_t const * len_start = pos;
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pos = varint_skip(pos, end);
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std::size_t len = varint_decode<std::size_t>(len_start, pos);
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if (len > end - pos) return result;
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reader.ciphertext_length = len;
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reader.ciphertext = pos;
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pos += len;
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flags |= 4;
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} else if (tag & 0x7 == 0) {
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pos = varint_skip(pos, end);
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pos = varint_skip(pos, end);
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} else if (tag & 0x7 == 2) {
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std::uint8_t const * len_start = pos;
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pos = varint_skip(pos, end);
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std::size_t len = varint_decode<std::size_t>(len_start, pos);
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if (len > end - pos) return result;
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pos += len;
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} else {
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return std::size_t(-1);
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pos = decode(
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pos, end, RATCHET_KEY_TAG,
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reader.ratchet_key, reader.ratchet_key_length
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);
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pos = decode(
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pos, end, COUNTER_TAG,
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reader.counter, reader.has_counter
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);
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pos = decode(
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pos, end, CIPHERTEXT_TAG,
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reader.ciphertext, reader.ciphertext_length
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);
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if (unknown == pos) {
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pos == skip_unknown(pos, end);
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}
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unknown = pos;
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}
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}
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namespace {
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static std::uint8_t const REGISTRATION_ID_TAG = 050;
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static std::uint8_t const ONE_TIME_KEY_ID_TAG = 010;
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static std::uint8_t const BASE_KEY_TAG = 022;
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static std::uint8_t const IDENTITY_KEY_TAG = 032;
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static std::uint8_t const MESSAGE_TAG = 042;
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} // namespace
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std::size_t axolotl::encode_one_time_key_message_length(
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std::uint32_t registration_id,
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std::uint32_t one_time_key_id,
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std::size_t identity_key_length,
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std::size_t base_key_length,
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std::size_t message_length
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) {
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std::size_t length = VERSION_LENGTH;
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length += 1 + varint_length(registration_id);
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length += 1 + varint_length(one_time_key_id);
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length += 1 + varstring_length(identity_key_length);
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length += 1 + varstring_length(base_key_length);
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length += 1 + varstring_length(message_length);
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return length;
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}
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void axolotl::encode_one_time_key_message(
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axolotl::PreKeyMessageWriter & writer,
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std::uint8_t version,
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std::uint32_t registration_id,
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std::uint32_t one_time_key_id,
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std::size_t identity_key_length,
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std::size_t base_key_length,
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std::size_t message_length,
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std::uint8_t * output
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) {
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std::uint8_t * pos = output;
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*(pos++) = version;
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pos = encode(pos, REGISTRATION_ID_TAG, registration_id);
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pos = encode(pos, ONE_TIME_KEY_ID_TAG, one_time_key_id);
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pos = encode(pos, BASE_KEY_TAG, writer.base_key, base_key_length);
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pos = encode(pos, IDENTITY_KEY_TAG, writer.identity_key, identity_key_length);
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pos = encode(pos, MESSAGE_TAG, writer.message, message_length);
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}
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void axolotl::decode_one_time_key_message(
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PreKeyMessageReader & reader,
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std::uint8_t const * input, std::size_t input_length
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) {
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std::uint8_t const * pos = input;
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std::uint8_t const * end = input + input_length;
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std::uint8_t const * unknown = NULL;
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if (pos == end) return;
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reader.version = *(pos++);
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reader.has_registration_id = false;
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reader.has_one_time_key_id = false;
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reader.identity_key = NULL;
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reader.base_key = NULL;
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reader.message = NULL;
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while (pos != end) {
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pos = decode(
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pos, end, REGISTRATION_ID_TAG,
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reader.registration_id, reader.has_registration_id
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);
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pos = decode(
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pos, end, ONE_TIME_KEY_ID_TAG,
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reader.one_time_key_id, reader.has_one_time_key_id
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);
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pos = decode(
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pos, end, BASE_KEY_TAG,
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reader.base_key, reader.base_key_length
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);
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pos = decode(
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pos, end, IDENTITY_KEY_TAG,
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reader.identity_key, reader.identity_key_length
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);
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pos = decode(
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pos, end, MESSAGE_TAG,
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reader.message, reader.message_length
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);
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if (unknown == pos) {
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pos == skip_unknown(pos, end);
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}
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unknown = pos;
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}
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if (flags == 0x7) {
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reader.input = input;
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reader.input_length = input_length;
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return std::size_t(pos - input);
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}
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return result;
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}
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@ -444,7 +444,7 @@ std::size_t axolotl::Session::decrypt(
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}
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axolotl::MessageReader reader;
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std::size_t body_length = axolotl::decode_message(
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axolotl::decode_message(
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reader, input, input_length, ratchet_cipher.mac_length()
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);
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@ -453,7 +453,12 @@ std::size_t axolotl::Session::decrypt(
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return std::size_t(-1);
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}
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if (body_length == size_t(-1) || reader.ratchet_key_length != KEY_LENGTH) {
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if (!reader.has_counter || !reader.ratchet_key || !reader.ciphertext) {
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last_error = axolotl::ErrorCode::BAD_MESSAGE_FORMAT;
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return std::size_t(-1);
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}
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if (reader.ratchet_key_length != KEY_LENGTH) {
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last_error = axolotl::ErrorCode::BAD_MESSAGE_FORMAT;
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return std::size_t(-1);
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}
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@ -17,8 +17,8 @@
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int main() {
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std::uint8_t message1[36] = "\x03\n\nratchetkey\x10\x01\"\nciphertexthmacsha2";
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std::uint8_t message2[36] = "\x03\x10\x01\n\nratchetkey\"\nciphertexthmacsha2";
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std::uint8_t message1[36] = "\x03\x10\x01\n\nratchetkey\"\nciphertexthmacsha2";
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std::uint8_t message2[36] = "\x03\n\nratchetkey\x10\x01\"\nciphertexthmacsha2";
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std::uint8_t ratchetkey[11] = "ratchetkey";
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std::uint8_t ciphertext[11] = "ciphertext";
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std::uint8_t hmacsha2[9] = "hmacsha2";
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@ -31,6 +31,7 @@ axolotl::MessageReader reader;
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axolotl::decode_message(reader, message1, 35, 8);
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assert_equals(std::uint8_t(3), reader.version);
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assert_equals(true, reader.has_counter);
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assert_equals(std::uint32_t(1), reader.counter);
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assert_equals(std::size_t(10), reader.ratchet_key_length);
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assert_equals(std::size_t(10), reader.ciphertext_length);
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