From 5926a8fd29ecb997e6c4609e2195e68274d1f9df Mon Sep 17 00:00:00 2001 From: Mark Haines Date: Tue, 13 Sep 2016 16:45:54 +0100 Subject: [PATCH] Comment on the encoding of the message counter. --- src/inbound_group_session.c | 8 ++++---- src/outbound_group_session.c | 8 ++++---- 2 files changed, 8 insertions(+), 8 deletions(-) diff --git a/src/inbound_group_session.c b/src/inbound_group_session.c index f2a310a..82ff66f 100644 --- a/src/inbound_group_session.c +++ b/src/inbound_group_session.c @@ -88,10 +88,10 @@ static size_t _init_group_session_keys( } uint32_t counter = 0; - counter <<= 8; counter |= *ptr++; - counter <<= 8; counter |= *ptr++; - counter <<= 8; counter |= *ptr++; - counter <<= 8; counter |= *ptr++; + // 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); diff --git a/src/outbound_group_session.c b/src/outbound_group_session.c index 7116547..8686993 100644 --- a/src/outbound_group_session.c +++ b/src/outbound_group_session.c @@ -337,10 +337,10 @@ size_t olm_outbound_group_session_key( *ptr++ = SESSION_KEY_VERSION; uint32_t counter = session->ratchet.counter; - *ptr++ = 0xFF & (counter >> 24); counter <<= 8; - *ptr++ = 0xFF & (counter >> 24); counter <<= 8; - *ptr++ = 0xFF & (counter >> 24); counter <<= 8; - *ptr++ = 0xFF & (counter >> 24); counter <<= 8; + // Encode counter as a big endian 32-bit number. + if (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;