GSUP, OAP, osmo-gen-vec: fix AUTS length to 14, not 16

GSUP transmits AUTS for UMTS authentication procedures, and OAP uses the same
procedures to authenticate. osmo-gen-vec is a utility program that passes AUTS
to our osmo_auth_gen_vec_auts() API.

According to 3GPP 33.102 6.3.3, AUTS = SQN^AK || MAC-S, which are 6 || 8 == 14
bytes. This is confirmed by 24.008 9.2.3a where the TLV has 16 bytes, TL = 2
and AUTS being the V = 14.

It is not harmful for milenage_gen_vec_auts() to pass two more AUTS bytes. But
writing 16 bytes to a GSUP struct is a potential problem when passing in a 14
byte long AUTS buffer to the GSUP API, which then reads past the AUTS buffer.
The API implies the length, so far to be 16, so passing in a 14 byte buffer to
GSUP would require copying to a larger buffer first.

Fix this by using a length of 14 for AUTS everywhere instead.

This constitues an ABI breakage, we may handle it as a "fix before an official
release", otherwise we need a version bump.

The OAP protocol document has also been updated, needs an update in the
osmo-gsm-manuals as well.

Change-Id: If25b173d9ec57ea4c504d860954912b7d82af455
changes/31/1731/2
Neels Hofmeyr 6 years ago
parent 4a7f87cdc8
commit 8352d31a86
  1. 3
      TODO-RELEASE
  2. 2
      doc/osmocom-authn-protocol.txt
  3. 2
      include/osmocom/gsm/oap.h
  4. 2
      src/gsm/gsup.c
  5. 4
      tests/oap/oap_test.c
  6. 2
      tests/oap/oap_test.ok
  7. 2
      utils/osmo-auc-gen.c

@ -8,3 +8,6 @@
# If any interfaces have been removed or changed since the last public release: c:r:0.
#library what description / commit summary line
libosmocore new function osmo_sock_get_name()
libosmogsm/gsup ABI change fix AUTS length to 14, not 16 (length is implicit)
libosmogsm/oap ABI change fix AUTS length to 14, not 16 (length is implicit)
osmo-auc-gen UI change fix AUTS length to 14, not 16 (length is implicit)

@ -181,7 +181,7 @@ Client -> Server
IEI Info Element Type Pres. Format Length
Message type 4.2.1 M V 1
20 AUTS octet string (16) M TLV 18
20 AUTS octet string (14) M TLV 16
3.2.8. Sync Error

@ -64,7 +64,7 @@ struct osmo_oap_message {
int xres_present;
uint8_t xres[8];
int auts_present;
uint8_t auts[16];
uint8_t auts[14];
};
int osmo_oap_decode(struct osmo_oap_message *oap_msg, const uint8_t *data,

@ -497,7 +497,7 @@ void osmo_gsup_encode(struct msgb *msg, const struct osmo_gsup_message *gsup_msg
}
if (gsup_msg->auts)
msgb_tlv_put(msg, OSMO_GSUP_AUTS_IE, 16, gsup_msg->auts);
msgb_tlv_put(msg, OSMO_GSUP_AUTS_IE, 14, gsup_msg->auts);
if (gsup_msg->rand)
msgb_tlv_put(msg, OSMO_GSUP_RAND_IE, 16, gsup_msg->rand);

@ -155,8 +155,8 @@ static void test_oap_messages_dec_enc(void)
printf("- Sync Request\n");
CLEAR();
oap_msg.message_type = OAP_MSGT_SYNC_REQUEST;
osmo_hexparse("102030405060708090a0b0c0d0e0f001",
oap_msg.auts, 16);
osmo_hexparse("102030405060708090a0b0c0d0e0",
oap_msg.auts, 14);
oap_msg.auts_present = 1;
CHECK();

@ -37,6 +37,6 @@ encoded message:
ok
- Sync Request
encoded message:
0c 25 10 10 20 30 40 50 60 70 80 90 a0 b0 c0 d0 e0 f0 01
0c 25 0e 10 20 30 40 50 60 70 80 90 a0 b0 c0 d0 e0
ok
Done.

@ -87,7 +87,7 @@ int main(int argc, char **argv)
{
struct osmo_auth_vector _vec;
struct osmo_auth_vector *vec = &_vec;
uint8_t _rand[16], _auts[16];
uint8_t _rand[16], _auts[14];
int rc, option_index;
int rand_is_set = 0;
int auts_is_set = 0;

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