libosmogsm: Allow auth API caller to specify RES length

There are 3G algorithms which support different lengths of RES values
(4, 8, 16 byte).  For MILENAGE, we never really had to bother, as
the 4-byte RES is simply the first 4 bytes of the 8-byte RES.

However, for TUAK, the expected RES length is an input parameter to
the Keccak crypto functions, so the result of all parameters (including
CK, IK, ...) will be completely different for RES length 4 than RES
length 8.

So let's permit the caller of the osmocom auth API to specify the
requested RES length via the osmo_auth_vector.res_len parameter.

For backwards compatibility of callers of the old osmo_auth_gen_vec/
osmo_auth_gen_vec_auts API: Always force the res_len to 8 in this case,
which was the hard-coded length before this patch.

Change-Id: Ic662843fbe8b5c58e4af39ea630ad5ac13fd6bef

1 files changed, 14 insertions, 4 deletions

diff --git a/utils/osmo-auc-gen.c b/utils/osmo-auc-gen.c
index 86abeda6..50419a43 100644
--- a/utils/osmo-auc-gen.c
+++ b/utils/osmo-auc-gen.c
@@ -98,6 +98,7 @@ static void help(void)
 		"-s  --sqn\tSpecify SQN (only for 3G)\n"
 		"-i  --ind\tSpecify IND slot for new SQN after AUTS (only for 3G)\n"
 		"-l  --ind-len\tSpecify IND bit length (default=5) (only for 3G)\n"
+		"-L  --res-len\tSpecify RES byte length (default=8) (only for 3G)\n"
 		"-A  --auts\tSpecify AUTS (only for 3G)\n"
 		"-r  --rand\tSpecify random value\n"
 		"-I  --ipsec\tOutput in triplets.dat format for strongswan\n");
@@ -123,10 +124,12 @@ int main(int argc, char **argv)
 	int fmt_triplets_dat = 0;
 	uint64_t ind_mask = 0;
 
-	printf("osmo-auc-gen (C) 2011-2012 by Harald Welte\n");
+	printf("osmo-auc-gen (C) 2011-2023 by Harald Welte\n");
 	printf("This is FREE SOFTWARE with ABSOLUTELY NO WARRANTY\n\n");
 
 	memset(_auts, 0, sizeof(_auts));
+	memset(vec, 0, sizeof(*vec));
+	vec->res_len = 8; /* default */
 
 	while (1) {
 		int c;
@@ -141,6 +144,7 @@ int main(int argc, char **argv)
 			{ "sqn", 1, 0, 's' },
 			{ "ind", 1, 0, 'i' },
 			{ "ind-len", 1, 0, 'l' },
+			{ "res-len", 1, 0, 'L' },
 			{ "rand", 1, 0, 'r' },
 			{ "auts", 1, 0, 'A' },
 			{ "help", 0, 0, 'h' },
@@ -149,7 +153,7 @@ int main(int argc, char **argv)
 
 		rc = 0;
 
-		c = getopt_long(argc, argv, "23a:k:o:f:s:i:l:r:hO:A:I", long_options,
+		c = getopt_long(argc, argv, "23a:k:o:f:s:i:l:L:r:hO:A:I", long_options,
 				&option_index);
 
 		if (c == -1)
@@ -265,6 +269,14 @@ int main(int argc, char **argv)
 			}
 			test_aud.u.umts.ind_bitlen = atoi(optarg);
 			break;
+		case 'L':
+			rc = atoi(optarg);
+			if (rc != 4 && rc != 8 && rc != 16) {
+				fprintf(stderr, "Invalid RES length %u\n", rc);
+				exit(2);
+			}
+			vec->res_len = rc;
+			break;
 		case 'r':
 			rc = osmo_hexparse(optarg, _rand, sizeof(_rand));
 			if (rc != sizeof(_rand)) {
@@ -313,8 +325,6 @@ int main(int argc, char **argv)
 		exit(2);
 	}
 
-	memset(vec, 0, sizeof(*vec));
-
 	if (test_aud.type == OSMO_AUTH_TYPE_UMTS) {
 		uint64_t seq_1 = 1LL << test_aud.u.umts.ind_bitlen;
 		ind_mask = seq_1 - 1;