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-rw-r--r--src/inbound_group_session.c43
1 files changed, 36 insertions, 7 deletions
diff --git a/src/inbound_group_session.c b/src/inbound_group_session.c
index be0984c..845c960 100644
--- a/src/inbound_group_session.c
+++ b/src/inbound_group_session.c
@@ -30,7 +30,7 @@
#define OLM_PROTOCOL_VERSION 3
#define GROUP_SESSION_ID_LENGTH ED25519_PUBLIC_KEY_LENGTH
-#define PICKLE_VERSION 1
+#define PICKLE_VERSION 2
#define SESSION_KEY_VERSION 2
#define SESSION_EXPORT_VERSION 1
@@ -44,6 +44,17 @@ struct OlmInboundGroupSession {
/** The ed25519 signing key */
struct _olm_ed25519_public_key signing_key;
+ /**
+ * Have we ever seen any evidence that this is a valid session?
+ * (either because the original session share was signed, or because we
+ * have subsequently successfully decrypted a message?)
+ *
+ * (We don't do anything with this currently, but we may want to bear it in
+ * mind when we consider handling key-shares for sessions we already know
+ * about.)
+ */
+ int signing_key_verified;
+
enum OlmErrorCode last_error;
};
@@ -109,11 +120,15 @@ static size_t _init_group_session_keys(
);
ptr += ED25519_PUBLIC_KEY_LENGTH;
- if (!export_format && !_olm_crypto_ed25519_verify(
- &session->signing_key, key_buf, ptr - key_buf, ptr
- )) {
- session->last_error = OLM_BAD_SIGNATURE;
- return (size_t)-1;
+ if (!export_format) {
+ if (!_olm_crypto_ed25519_verify(&session->signing_key, key_buf,
+ ptr - key_buf, ptr)) {
+ session->last_error = OLM_BAD_SIGNATURE;
+ return (size_t)-1;
+ }
+
+ /* signed keyshare */
+ session->signing_key_verified = 1;
}
return 0;
}
@@ -174,6 +189,7 @@ static size_t raw_pickle_length(
length += megolm_pickle_length(&session->initial_ratchet);
length += megolm_pickle_length(&session->latest_ratchet);
length += _olm_pickle_ed25519_public_key_length(&session->signing_key);
+ length += _olm_pickle_bool_length(session->signing_key_verified);
return length;
}
@@ -201,6 +217,7 @@ size_t olm_pickle_inbound_group_session(
pos = megolm_pickle(&session->initial_ratchet, pos);
pos = megolm_pickle(&session->latest_ratchet, pos);
pos = _olm_pickle_ed25519_public_key(pos, &session->signing_key);
+ pos = _olm_pickle_bool(pos, session->signing_key_verified);
return _olm_enc_output(key, key_length, pickled, raw_length);
}
@@ -224,7 +241,7 @@ size_t olm_unpickle_inbound_group_session(
pos = pickled;
end = pos + raw_length;
pos = _olm_unpickle_uint32(pos, end, &pickle_version);
- if (pickle_version != PICKLE_VERSION) {
+ if (pickle_version < 1 || pickle_version > PICKLE_VERSION) {
session->last_error = OLM_UNKNOWN_PICKLE_VERSION;
return (size_t)-1;
}
@@ -232,6 +249,14 @@ size_t olm_unpickle_inbound_group_session(
pos = megolm_unpickle(&session->latest_ratchet, pos, end);
pos = _olm_unpickle_ed25519_public_key(pos, end, &session->signing_key);
+ if (pickle_version == 1) {
+ /* pickle v1 had no signing_key_verified field (all keyshares were
+ * verified at import time) */
+ session->signing_key_verified = 1;
+ } else {
+ pos = _olm_unpickle_bool(pos, end, &(session->signing_key_verified));
+ }
+
if (end != pos) {
/* We had the wrong number of bytes in the input. */
session->last_error = OLM_CORRUPTED_PICKLE;
@@ -391,6 +416,10 @@ static size_t _decrypt(
return r;
}
+ /* once we have successfully decrypted a message, set a flag to say the
+ * session appears valid. */
+ session->signing_key_verified = 1;
+
return r;
}