Commit e0b51971 authored by Mark Haines's avatar Mark Haines Committed by GitHub
Browse files

Merge pull request #21 from matrix-org/markjh/fix_session_ids

Use the ed25519 public key as the group session id.
parents 976495e0 a89a169c
......@@ -30,7 +30,7 @@
#define OLM_PROTOCOL_VERSION 3
#define PICKLE_VERSION 1
#define SESSION_KEY_VERSION 1
#define SESSION_KEY_VERSION 2
struct OlmInboundGroupSession {
/** our earliest known ratchet value */
......@@ -71,12 +71,12 @@ size_t olm_clear_inbound_group_session(
}
#define SESSION_KEY_RAW_LENGTH \
(1 + MEGOLM_RATCHET_LENGTH + ED25519_PUBLIC_KEY_LENGTH)
(1 + 4 + MEGOLM_RATCHET_LENGTH + ED25519_PUBLIC_KEY_LENGTH\
+ ED25519_SIGNATURE_LENGTH)
/** init the session keys from the un-base64-ed session keys */
static size_t _init_group_session_keys(
OlmInboundGroupSession *session,
uint32_t message_index,
const uint8_t *key_buf
) {
const uint8_t *ptr = key_buf;
......@@ -87,13 +87,27 @@ static size_t _init_group_session_keys(
return (size_t)-1;
}
megolm_init(&session->initial_ratchet, ptr, message_index);
megolm_init(&session->latest_ratchet, ptr, message_index);
uint32_t counter = 0;
// Decode counter as a big endian 32-bit number.
for (unsigned i = 0; i < 4; i++) {
counter <<= 8; counter |= *ptr++;
}
megolm_init(&session->initial_ratchet, ptr, counter);
megolm_init(&session->latest_ratchet, ptr, counter);
ptr += MEGOLM_RATCHET_LENGTH;
memcpy(
session->signing_key.public_key, ptr, ED25519_PUBLIC_KEY_LENGTH
);
ptr += ED25519_PUBLIC_KEY_LENGTH;
if (!_olm_crypto_ed25519_verify(
&session->signing_key, key_buf, ptr - key_buf, ptr
)) {
session->last_error = OLM_BAD_SIGNATURE;
return (size_t)-1;
}
return 0;
}
......@@ -117,7 +131,7 @@ size_t olm_init_inbound_group_session(
}
_olm_decode_base64(session_key, session_key_length, key_buf);
result = _init_group_session_keys(session, message_index, key_buf);
result = _init_group_session_keys(session, key_buf);
_olm_unset(key_buf, SESSION_KEY_RAW_LENGTH);
return result;
}
......@@ -288,7 +302,6 @@ static size_t _decrypt(
return (size_t)-1;
}
max_length = megolm_cipher->ops->decrypt_max_plaintext_length(
megolm_cipher,
decoded_results.ciphertext_length
......
......@@ -29,10 +29,9 @@
#include "olm/pickle_encoding.h"
#define OLM_PROTOCOL_VERSION 3
#define SESSION_ID_RANDOM_BYTES 4
#define GROUP_SESSION_ID_LENGTH (sizeof(struct timeval) + SESSION_ID_RANDOM_BYTES)
#define GROUP_SESSION_ID_LENGTH ED25519_PUBLIC_KEY_LENGTH
#define PICKLE_VERSION 1
#define SESSION_KEY_VERSION 1
#define SESSION_KEY_VERSION 2
struct OlmOutboundGroupSession {
/** the Megolm ratchet providing the encryption keys */
......@@ -41,9 +40,6 @@ struct OlmOutboundGroupSession {
/** The ed25519 keypair used for signing the messages */
struct _olm_ed25519_key_pair signing_key;
/** unique identifier for this session */
uint8_t session_id[GROUP_SESSION_ID_LENGTH];
enum OlmErrorCode last_error;
};
......@@ -80,8 +76,6 @@ static size_t raw_pickle_length(
length += _olm_pickle_uint32_length(PICKLE_VERSION);
length += megolm_pickle_length(&(session->ratchet));
length += _olm_pickle_ed25519_key_pair_length(&(session->signing_key));
length += _olm_pickle_bytes_length(session->session_id,
GROUP_SESSION_ID_LENGTH);
return length;
}
......@@ -108,7 +102,6 @@ size_t olm_pickle_outbound_group_session(
pos = _olm_pickle_uint32(pos, PICKLE_VERSION);
pos = megolm_pickle(&(session->ratchet), pos);
pos = _olm_pickle_ed25519_key_pair(pos, &(session->signing_key));
pos = _olm_pickle_bytes(pos, session->session_id, GROUP_SESSION_ID_LENGTH);
return _olm_enc_output(key, key_length, pickled, raw_length);
}
......@@ -138,7 +131,6 @@ size_t olm_unpickle_outbound_group_session(
}
pos = megolm_unpickle(&(session->ratchet), pos, end);
pos = _olm_unpickle_ed25519_key_pair(pos, end, &(session->signing_key));
pos = _olm_unpickle_bytes(pos, end, session->session_id, GROUP_SESSION_ID_LENGTH);
if (end != pos) {
/* We had the wrong number of bytes in the input. */
......@@ -157,8 +149,7 @@ size_t olm_init_outbound_group_session_random_length(
* session id.
*/
return MEGOLM_RATCHET_LENGTH +
ED25519_RANDOM_LENGTH +
SESSION_ID_RANDOM_BYTES;
ED25519_RANDOM_LENGTH;
}
size_t olm_init_outbound_group_session(
......@@ -177,13 +168,6 @@ size_t olm_init_outbound_group_session(
_olm_crypto_ed25519_generate_key(random, &(session->signing_key));
random += ED25519_RANDOM_LENGTH;
/* initialise the session id. This just has to be unique. We use the
* current time plus some random data.
*/
gettimeofday((struct timeval *)(session->session_id), NULL);
memcpy((session->session_id) + sizeof(struct timeval),
random, SESSION_ID_RANDOM_BYTES);
return 0;
}
......@@ -314,7 +298,9 @@ size_t olm_outbound_group_session_id(
return (size_t)-1;
}
return _olm_encode_base64(session->session_id, GROUP_SESSION_ID_LENGTH, id);
return _olm_encode_base64(
session->signing_key.public_key.public_key, GROUP_SESSION_ID_LENGTH, id
);
}
uint32_t olm_outbound_group_session_message_index(
......@@ -324,7 +310,8 @@ uint32_t olm_outbound_group_session_message_index(
}
#define SESSION_KEY_RAW_LENGTH \
(1 + MEGOLM_RATCHET_LENGTH + ED25519_PUBLIC_KEY_LENGTH)
(1 + 4 + MEGOLM_RATCHET_LENGTH + ED25519_PUBLIC_KEY_LENGTH\
+ ED25519_SIGNATURE_LENGTH)
size_t olm_outbound_group_session_key_length(
const OlmOutboundGroupSession *session
......@@ -349,6 +336,12 @@ size_t olm_outbound_group_session_key(
raw = ptr = key + encoded_length - SESSION_KEY_RAW_LENGTH;
*ptr++ = SESSION_KEY_VERSION;
uint32_t counter = session->ratchet.counter;
// Encode counter as a big endian 32-bit number.
for (unsigned i = 0; i < 4; i++) {
*ptr++ = 0xFF & (counter >> 24); counter <<= 8;
}
memcpy(ptr, megolm_get_data(&session->ratchet), MEGOLM_RATCHET_LENGTH);
ptr += MEGOLM_RATCHET_LENGTH;
......@@ -358,5 +351,11 @@ size_t olm_outbound_group_session_key(
);
ptr += ED25519_PUBLIC_KEY_LENGTH;
/* sign the whole thing with the ed25519 key. */
_olm_crypto_ed25519_sign(
&(session->signing_key),
raw, ptr - raw, ptr
);
return _olm_encode_base64(raw, SESSION_KEY_RAW_LENGTH, key);
}
......@@ -97,7 +97,7 @@ int main() {
uint8_t memory[size];
OlmOutboundGroupSession *session = olm_outbound_group_session(memory);
assert_equals((size_t)164,
assert_equals((size_t)160,
olm_init_outbound_group_session_random_length(session));
size_t res = olm_init_outbound_group_session(
......@@ -154,14 +154,15 @@ int main() {
size_t plaintext_length = sizeof(plaintext) - 1;
uint8_t session_key[] =
"ATAxMjM0NTY3ODlBQkRFRjAxMjM0NTY3ODlBQkNERUYwMTIzNDU2Nzg5QUJERUYw"
"MTIzNDU2Nzg5QUJDREVGMDEyMzQ1Njc4OUFCREVGMDEyMzQ1Njc4OUFCQ0RFRjAx"
"MjM0NTY3ODlBQkRFRjAxMjM0NTY3ODlBQkNERUYwMTIzDRt2DUEOrg/H+yUGjDTq"
"ryf8H1YF/BZjI04HwOVSZcY";
"AgAAAAAwMTIzNDU2Nzg5QUJERUYwMTIzNDU2Nzg5QUJDREVGMDEyMzQ1Njc4OUFCREVGM"
"DEyMzQ1Njc4OUFCQ0RFRjAxMjM0NTY3ODlBQkRFRjAxMjM0NTY3ODlBQkNERUYwMTIzND"
"U2Nzg5QUJERUYwMTIzNDU2Nzg5QUJDREVGMDEyMztqJ7zOtqQtYqOo0CpvDXNlMhV3HeJ"
"DpjrASKGLWdop4lx1cSN3Xv1TgfLPW8rhGiW+hHiMxd36nRuxscNv9k4oJA/KP+o0mi1w"
"v44StrEJ1wwx9WZHBUIWkQbaBSuBDw";
uint8_t message[] =
"AwgAEhAcbh6UpbByoyZxufQ+h2B+8XHMjhR69G8F4+qjMaFlnIXusJZX3r8LnROR"
"G9T3DXFdbVuvIWrLyRfm4i8QRbe8VPwGRFG57B1CtmxanuP8bHtnnYqlwPsD";
"AwgAEhAcbh6UpbByoyZxufQ+h2B+8XHMjhR69G8nP4pNZGl/3QMgrzCZPmP+F2aPLyKPz"
"xRPBMUkeXRJ6Iqm5NeOdx2eERgTW7P20CM+lL3Xpk+ZUOOPvsSQNaAL";
size_t msglen = sizeof(message)-1;
/* build the inbound session */
......
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