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Vadim Yanitskiy gerrit-no-reply at lists.osmocom.org
Review at https://gerrit.osmocom.org/7310
libosmogsm: add support for XOR authentication
Change-Id: I1afaf0a9e2dce43aec87964bacefb21ed4d3d565
---
M src/gsm/Makefile.am
A src/gsm/auth_xor.c
2 files changed, 151 insertions(+), 1 deletion(-)
git pull ssh://gerrit.osmocom.org:29418/libosmocore refs/changes/10/7310/1
diff --git a/src/gsm/Makefile.am b/src/gsm/Makefile.am
index 0439ce6..478336b 100644
--- a/src/gsm/Makefile.am
+++ b/src/gsm/Makefile.am
@@ -25,7 +25,7 @@
gprs_cipher_core.c gprs_rlc.c gsm0480.c abis_nm.c gsm0502.c \
gsm0411_utils.c gsm0411_smc.c gsm0411_smr.c gsm0414.c \
lapd_core.c lapdm.c kasumi.c gsm_04_08_gprs.c \
- auth_core.c auth_comp128v1.c auth_comp128v23.c \
+ auth_core.c auth_comp128v1.c auth_comp128v23.c auth_xor.c \
auth_milenage.c milenage/aes-encblock.c gea.c \
milenage/aes-internal.c milenage/aes-internal-enc.c \
milenage/milenage.c gan.c ipa.c gsm0341.c apn.c \
diff --git a/src/gsm/auth_xor.c b/src/gsm/auth_xor.c
new file mode 100644
index 0000000..b037a32
--- /dev/null
+++ b/src/gsm/auth_xor.c
@@ -0,0 +1,150 @@
+/*! \file auth_xor.c
+ * GSM/GPRS/3G authentication core infrastructure */
+/*
+ * (C) 2017 by sysmocom s.f.m.c. GmbH
+ * All Rights Reserved
+ *
+ * Author: Daniel Willmann <dwillmann at sysmocom.de>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <osmocom/crypt/auth.h>
+#include <string.h>
+#include <errno.h>
+
+/*! \addtogroup auth
+ * @{
+ */
+
+static void xor(uint8_t *out, const uint8_t *a, const uint8_t *b, size_t len)
+{
+ size_t i;
+
+ for (i = 0; i < len; i++)
+ out[i] = a[i] ^ b[i];
+}
+
+/* 3GPP TS 34.108 8.1.2.1 XOR auth procedure */
+static int xor_gen_vec(struct osmo_auth_vector *vec,
+ struct osmo_sub_auth_data *aud, const uint8_t *_rand)
+{
+ uint8_t xdout[16], ak[6], cdout[8], xmac[8];
+ /* res[16], ck[16], ik[16],*/
+ int i;
+
+ /* Step 1: xdout = ki XOR rand */
+ if (aud->type == OSMO_AUTH_TYPE_GSM)
+ xor(xdout, aud->u.gsm.ki, _rand, sizeof(xdout));
+ else if (aud->type == OSMO_AUTH_TYPE_UMTS)
+ xor(xdout, aud->u.umts.k, _rand, sizeof(xdout));
+ else
+ return -ENOTSUP;
+
+ /**
+ * Step 2: res = xdout
+ *
+ * Suggested length for res is 128 bits, i.e. 16 bytes,
+ * but also can be in range: 30 < n < 128 bits.
+ */
+ memcpy(vec->res, xdout, sizeof(xdout));
+ vec->res_len = 16;
+
+ /* ck = xdout[1-15,0] */
+ memcpy(vec->ck, xdout + 1, sizeof(xdout) - 1);
+ vec->ck[15] = xdout[0];
+
+ /* ik = xdout[2-15,0-1] */
+ memcpy(vec->ik, xdout + 2, sizeof(xdout) - 2);
+ memcpy(vec->ik + 14, xdout, 2);
+
+ /* ak = xdout[3-8] */
+ memcpy(ak, xdout + 3, sizeof(ak));
+
+ /**
+ * 3GPP TS 33.102, clause 6.8.1.2, b
+ * sres = c2(res) = res[0-3] ^ res[4-7] ^ res[8-11] ^ res[12-15]
+ */
+ for (i = 0; i < 4; i++) {
+ vec->sres[i] = vec->res[i] ^ vec->res[i + 4];
+ vec->sres[i] ^= vec->res[i + 8] ^ vec->res[i + 12];
+ }
+
+ /**
+ * 3GPP TS 33.102, clause 6.8.1.2, c
+ * kc = c3(ck, ik) = ck[0-3] ^ ck[4-7] ^ ik[0-3] ^ ik[4-7]
+ */
+ for (i = 0; i < 8; i++) {
+ vec->kc[i] = vec->ck[i] ^ vec->ck[i + 8];
+ vec->kc[i] ^= vec->ik[i] ^ vec->ik[i + 8];
+ }
+
+ /* The further part is UMTS specific */
+ if (aud->type != OSMO_AUTH_TYPE_UMTS) {
+ vec->auth_types = OSMO_AUTH_TYPE_GSM;
+ return 0;
+ }
+
+ /**
+ * Step 3: cdout = sqn[0-5] || amf[0-1]
+ *
+ * FIXME: The aud->u.umts.sqn has uint64_t type,
+ * so 8 bytes long. We take 6 bytes from *the beginning*
+ * of sqn, but shouldn't we shift it first?
+ * I.e. aud->u.umts.sqn << 2
+ *
+ * And what about byte order??
+ */
+ memcpy(cdout, (uint8_t *) &aud->u.umts.sqn, 6);
+ memcpy(cdout + 6, aud->u.umts.amf, 2);
+
+ /* Step 4: xmac = xdout[0-8] XOR cdout[0-8] */
+ xor(xmac, xdout, cdout, sizeof(xmac));
+
+ /**
+ * Step 5: autn = sqn XOR ak || amf || mac
+ *
+ * FIXME: The aud->u.umts.sqn has uint64_t type,
+ * so 8 bytes long. We take 6 bytes from *the beginning*
+ * of sqn, but shouldn't we shift it first?
+ * I.e. aud->u.umts.sqn << 2
+ *
+ * And what about byte order??
+ */
+ xor(vec->autn, (uint8_t *) &aud->u.umts.sqn, ak, sizeof(ak));
+ memcpy(vec->autn + 6, aud->u.umts.amf, 2);
+ memcpy(vec->autn + 8, xmac, sizeof(xmac));
+
+ vec->auth_types = OSMO_AUTH_TYPE_UMTS | OSMO_AUTH_TYPE_GSM;
+
+ return 0;
+}
+
+static struct osmo_auth_impl xor_alg = {
+ .algo = OSMO_AUTH_ALG_XOR,
+ .name = "XOR (libosmogsm built-in)",
+ .priority = 1000,
+ .gen_vec = &xor_gen_vec,
+};
+
+static __attribute__((constructor)) void on_dso_load_xor(void)
+{
+ osmo_auth_register(&xor_alg);
+}
+
+/*! @} */
--
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I1afaf0a9e2dce43aec87964bacefb21ed4d3d565
Gerrit-PatchSet: 1
Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Owner: Vadim Yanitskiy <axilirator at gmail.com>
Gerrit-Reviewer: daniel <dwillmann at sysmocom.de>