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mirror of https://git.kernel.org/pub/scm/network/wireless/iwd.git synced 2024-12-30 06:02:39 +01:00

eap: Implement the EAP-TTLS method

Only EAP as the inner authentication option is supported.  According to
wikipedia this is the most popular EAP-TTLS use case, with MD5 as the
inner EAP's method.
This commit is contained in:
Andrew Zaborowski 2015-10-30 11:12:17 +01:00 committed by Denis Kenzior
parent c5e368a264
commit 830161399e
4 changed files with 707 additions and 3 deletions

View File

@ -70,7 +70,7 @@ src_iwd_SOURCES = src/main.c linux/nl80211.h linux/kdbus.h \
src/wscutil.h src/wscutil.c \
src/wsc.h src/wsc.c \
src/eap.h src/eap.c \
src/eap-tls.c \
src/eap-tls.c src/eap-ttls.c \
src/iwd.h
src_iwd_LDADD = ell/libell-internal.la
@ -90,7 +90,7 @@ monitor_iwmon_SOURCES = monitor/main.c linux/nl80211.h \
src/crypto.h src/crypto.c \
src/eapol.h src/eapol.c \
src/eap.h src/eap.c \
src/eap-tls.c
src/eap-tls.c src/eap-ttls.c
monitor_iwmon_LDADD = ell/libell-internal.la
noinst_PROGRAMS = tools/hwsim
@ -159,7 +159,7 @@ unit_test_eapol_SOURCES = unit/test-eapol.c \
src/ie.h src/ie.c \
src/eapol.h src/eapol.c \
src/eap.h src/eap.c \
src/eap-tls.c
src/eap-tls.c src/eap-ttls.c
unit_test_eapol_LDADD = ell/libell-internal.la
unit_test_ssid_to_utf8_SOURCES = src/util.h src/util.c \

702
src/eap-ttls.c Normal file
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@ -0,0 +1,702 @@
/*
*
* Wireless daemon for Linux
*
* Copyright (C) 2013-2014 Intel Corporation. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <ell/ell.h>
#include <ell/tls-private.h>
#include "eap.h"
struct eap_ttls_state {
char *ca_cert;
char *client_cert;
char *client_key;
char *passphrase;
struct l_tls *tls;
uint8_t *rx_pkt_buf;
size_t rx_pkt_received, rx_pkt_len;
uint8_t *tx_pkt_buf;
size_t tx_pkt_len, tx_pkt_capacity, tx_pkt_offset;
uint8_t *avp_buf;
size_t avp_received, avp_capacity;
bool phase1_completed;
bool completed;
struct eap_state *eap;
uint8_t negotiated_version;
};
static int eap_ttls_probe(struct eap_state *eap, const char *name)
{
struct eap_ttls_state *ttls;
if (strcasecmp(name, "TTLS"))
return -ENOTSUP;
ttls = l_new(struct eap_ttls_state, 1);
eap_set_data(eap, ttls);
return 0;
}
static void eap_ttls_remove(struct eap_state *eap)
{
struct eap_ttls_state *ttls = eap_get_data(eap);
eap_set_data(eap, NULL);
l_free(ttls->ca_cert);
l_free(ttls->client_cert);
l_free(ttls->client_key);
l_free(ttls->passphrase);
if (ttls->rx_pkt_buf) {
l_free(ttls->rx_pkt_buf);
ttls->rx_pkt_buf = NULL;
}
if (ttls->tx_pkt_buf) {
l_free(ttls->tx_pkt_buf);
ttls->tx_pkt_buf = NULL;
ttls->tx_pkt_capacity = 0;
ttls->tx_pkt_len = 0;
}
if (ttls->avp_buf) {
l_free(ttls->avp_buf);
ttls->avp_buf = NULL;
ttls->avp_received = 0;
}
if (ttls->eap) {
eap_free(ttls->eap);
ttls->eap = NULL;
}
if (ttls->tls) {
l_tls_free(ttls->tls);
ttls->tls = NULL;
}
l_free(ttls);
}
#define EAP_TTLS_RESPONSE_HEADER_LEN 10
#define EAP_TTLS_FLAG_L (1 << 7)
#define EAP_TTLS_FLAG_M (1 << 6)
#define EAP_TTLS_FLAG_S (1 << 5)
#define EAP_TTLS_FLAG_MASK \
(EAP_TTLS_FLAG_L | EAP_TTLS_FLAG_M | EAP_TTLS_FLAG_S)
static uint8_t *eap_ttls_tx_buf_reserve(struct eap_ttls_state *ttls,
size_t size)
{
int offset = ttls->tx_pkt_offset + ttls->tx_pkt_len;
size_t end_offset = offset + size;
ttls->tx_pkt_len += size;
if (end_offset > ttls->tx_pkt_capacity) {
ttls->tx_pkt_capacity = end_offset + 1024;
ttls->tx_pkt_buf =
l_realloc(ttls->tx_pkt_buf, ttls->tx_pkt_capacity);
}
return ttls->tx_pkt_buf + offset;
}
static void eap_ttls_tx_cb(const uint8_t *data, size_t len, void *user_data)
{
struct eap_state *eap = user_data;
struct eap_ttls_state *ttls = eap_get_data(eap);
memcpy(eap_ttls_tx_buf_reserve(ttls, len), data, len);
}
struct eap_ttls_avp {
__be32 avp_code;
uint8_t avp_flags;
uint8_t avp_len[3];
uint8_t data[0];
} __attribute__ ((packed));
#define EAP_TTLS_AVP_FLAG_V (1 << 7)
#define EAP_TTLS_AVP_FLAG_M (1 << 6)
#define RADIUS_AVP_EAP_MESSAGE 79
static bool eap_ttls_handle_avp(struct eap_state *eap, struct eap_ttls_avp *avp)
{
struct eap_ttls_state *ttls = eap_get_data(eap);
uint8_t *data;
uint64_t code;
size_t data_len;
data = avp->data;
data_len = ((avp->avp_len[0] << 16) |
(avp->avp_len[1] << 8) |
(avp->avp_len[2] << 0)) - sizeof(struct eap_ttls_avp);
code = l_get_be32(&avp->avp_code);
if (avp->avp_flags & EAP_TTLS_AVP_FLAG_V) {
if (data_len < 4)
goto avp_err;
code |= (uint64_t) l_get_be32(data) << 32;
data += 4;
data_len -= 4;
}
switch (code) {
/* EAP-Message attribute, actually defined in RFC2869 5.13 */
case RADIUS_AVP_EAP_MESSAGE:
if (!ttls->eap)
goto avp_err;
/* TODO: split if necessary */
eap_rx_packet(ttls->eap, data, data_len);
break;
default:
if (avp->avp_flags & EAP_TTLS_AVP_FLAG_M)
goto avp_err;
break;
}
return true;
avp_err:
l_tls_close(ttls->tls);
return false;
}
static size_t avp_min_len(const uint8_t *buf, size_t len)
{
struct eap_ttls_avp *avp;
if (len < sizeof(struct eap_ttls_avp))
return sizeof(struct eap_ttls_avp);
avp = (struct eap_ttls_avp *) buf;
return (((avp->avp_len[0] << 16) |
(avp->avp_len[1] << 8) |
(avp->avp_len[2] << 0)) + 3) & ~3;
}
static void eap_ttls_data_cb(const uint8_t *data, size_t len, void *user_data)
{
struct eap_state *eap = user_data;
struct eap_ttls_state *ttls = eap_get_data(eap);
struct eap_ttls_avp *avp;
size_t avp_len, chunk_len;
/* Continue assembling the AVP that we have buffered */
while (ttls->avp_received) {
avp_len = avp_min_len(ttls->avp_buf, ttls->avp_received);
chunk_len = avp_len - ttls->avp_received;
if (chunk_len > len)
chunk_len = len;
if (ttls->avp_received + chunk_len > ttls->avp_capacity) {
ttls->avp_capacity = avp_len;
ttls->avp_buf = l_realloc(ttls->avp_buf,
ttls->avp_capacity);
}
memcpy(ttls->avp_buf + ttls->avp_received, data, chunk_len);
ttls->avp_received += chunk_len;
if (avp_len > ttls->avp_received) /* Wait for more data */
return;
/* Do we have a full AVP or just the header */
if (ttls->avp_received - chunk_len >=
sizeof(struct eap_ttls_avp)) {
ttls->avp_received = 0;
avp = (struct eap_ttls_avp *) ttls->avp_buf;
if (!eap_ttls_handle_avp(eap, avp))
return;
data += chunk_len;
len -= chunk_len;
}
}
/* Handle all the AVPs fully contained in the newly received data */
while (len) {
avp_len = avp_min_len(data, len);
if (len < avp_len || len < sizeof(struct eap_ttls_avp))
break;
avp = (struct eap_ttls_avp *) data;
if (!eap_ttls_handle_avp(eap, avp))
return;
data += avp_len;
len -= avp_len;
}
if (!len)
return;
/* Store the remaining bytes */
if (ttls->avp_capacity < len) {
ttls->avp_capacity = avp_len;
ttls->avp_buf = l_realloc(ttls->avp_buf, ttls->avp_capacity);
}
memcpy(ttls->avp_buf, data, len);
ttls->avp_received = len;
}
static void eap_ttls_eap_tx_packet(const uint8_t *eap_data, size_t len,
void *user_data)
{
struct eap_state *eap = user_data;
struct eap_ttls_state *ttls = eap_get_data(eap);
uint8_t buf[sizeof(struct eap_ttls_avp) + len + 3];
struct eap_ttls_avp *avp = (struct eap_ttls_avp *) buf;
size_t avp_len = sizeof(struct eap_ttls_avp) + len;
l_put_be32(RADIUS_AVP_EAP_MESSAGE, &avp->avp_code);
avp->avp_flags = EAP_TTLS_AVP_FLAG_M;
avp->avp_len[0] = avp_len >> 16;
avp->avp_len[1] = avp_len >> 8;
avp->avp_len[2] = avp_len >> 0;
memcpy(avp->data, eap_data, len);
if (avp_len & 3)
memset(avp->data + len, 0, 4 - (avp_len & 3));
l_tls_write(ttls->tls, buf, (avp_len + 3) & ~3);
}
static void eap_ttls_eap_complete(enum eap_result result, void *user_data)
{
struct eap_state *eap = user_data;
struct eap_ttls_state *ttls = eap_get_data(eap);
uint8_t last_id;
eap_save_last_id(ttls->eap, &last_id);
/* Prepare for possible chained authentication */
/* We currently have no way to configure the new instance */
eap_free(ttls->eap);
ttls->eap = eap_new(eap_ttls_eap_tx_packet,
eap_ttls_eap_complete, eap);
if (!ttls->eap) {
ttls->completed = true;
return;
}
/* Preserve the last_id as mandated by 11.3 */
eap_restore_last_id(ttls->eap, last_id);
}
static void eap_ttls_ready_cb(const char *peer_identity, void *user_data)
{
struct eap_state *eap = user_data;
struct eap_ttls_state *ttls = eap_get_data(eap);
uint8_t msk_emsk[128];
uint8_t seed[64];
uint8_t packet[5] = { EAP_CODE_REQUEST, 0, 0, 5, EAP_TYPE_IDENTITY };
/* TODO: if we have a CA certificate require non-NULL peer_identity */
ttls->phase1_completed = true;
/*
* TTLSv0 seems to assume that the TLS handshake phase authenticates
* the server to the client enough that the inner method success or
* failure status doesn't matter as long as the server lets us in,
* although in various places it says the client may also have a
* specific policy.
*/
eap_method_success(eap);
/* MSK, EMSK and challenge derivation */
memcpy(seed + 0, ttls->tls->pending.client_random, 32);
memcpy(seed + 32, ttls->tls->pending.server_random, 32);
tls_prf_get_bytes(ttls->tls, L_CHECKSUM_SHA256, 32,
ttls->tls->pending.master_secret,
sizeof(ttls->tls->pending.master_secret),
"ttls keying material", seed, 64,
msk_emsk, 128);
memset(seed, 0, 64);
eap_set_key_material(eap, msk_emsk + 0, 64, msk_emsk + 64, 64,
NULL, 0);
/* Start the EAP negotiation */
if (!ttls->eap) {
ttls->eap = eap_new(eap_ttls_eap_tx_packet,
eap_ttls_eap_complete, eap);
if (!ttls->eap) {
l_error("Could not create the TTLS inner EAP instance");
goto err;
}
}
/*
* Consume a fake Request/Identity packet so that the EAP instance
* starts with its Response/Identity right away.
*/
eap_rx_packet(ttls->eap, packet, sizeof(packet));
return;
err:
l_tls_close(ttls->tls);
}
static void eap_ttls_disconnect_cb(enum l_tls_alert_desc reason,
bool remote, void *user_data)
{
struct eap_state *eap = user_data;
struct eap_ttls_state *ttls = eap_get_data(eap);
ttls->completed = true;
}
static void eap_ttls_handle_request(struct eap_state *eap,
const uint8_t *pkt, size_t len)
{
uint8_t flags;
uint32_t total_len;
struct eap_ttls_state *ttls = eap_get_data(eap);
size_t fragment_len;
uint8_t *tx_buf;
if (len < 1) {
l_error("EAP-TTLS request too short");
goto err;
}
flags = pkt[0];
pkt += 1;
len -= 1;
if (!(flags & EAP_TTLS_FLAG_S) &&
(flags & 7) != ttls->negotiated_version) {
l_error("Non-zero EAP-TTLS version: %i", flags & 7);
goto err;
}
/* Check if we're expecting a fragment ACK */
if (ttls->tx_pkt_len) {
if ((flags & EAP_TTLS_FLAG_MASK) || len) {
l_error("EAP-TTLS request is not an ACK");
goto err;
}
/* Send next response fragment, prepend the 6-byte header */
tx_buf = &ttls->tx_pkt_buf[ttls->tx_pkt_offset - 6];
fragment_len = eap_get_mtu(eap) - 6;
tx_buf[5] = EAP_TTLS_FLAG_M |
ttls->negotiated_version; /* Flags */
if (ttls->tx_pkt_len <= fragment_len) {
fragment_len = ttls->tx_pkt_len;
tx_buf[5] = ttls->negotiated_version; /* Flags */
}
eap_send_response(eap, EAP_TYPE_TTLS,
tx_buf, fragment_len + 6);
ttls->tx_pkt_len -= fragment_len;
ttls->tx_pkt_offset += fragment_len;
return;
}
/* Complain if S bit is not correct */
if (!(flags & EAP_TTLS_FLAG_S) == !ttls->tls) {
l_error("EAP-TTLS request S flag invalid");
goto err;
}
/* Method can't be restarted */
if ((flags & EAP_TTLS_FLAG_S) && ttls->completed) {
l_error("EAP-TTLS start after completed");
goto err;
}
if (flags & EAP_TTLS_FLAG_L) {
if (len < 7) {
l_error("EAP-TTLS request with L flag too short");
goto err;
}
total_len = l_get_be32(pkt);
pkt += 4;
len -= 4;
if (ttls->rx_pkt_buf) {
l_error("EAP-TTLS request L flag invalid");
l_free(ttls->rx_pkt_buf);
ttls->rx_pkt_buf = NULL;
goto err;
}
if (!(flags & EAP_TTLS_FLAG_M) && total_len != len) {
l_error("EAP-TTLS request Length value invalid");
goto err;
}
}
if (!ttls->rx_pkt_buf && (flags & EAP_TTLS_FLAG_M)) {
if (!(flags & EAP_TTLS_FLAG_L)) {
l_error("EAP-TTLS requst 1st fragment with no length");
goto err;
}
ttls->rx_pkt_buf = l_malloc(total_len);
ttls->rx_pkt_len = total_len;
ttls->rx_pkt_received = 0;
}
if (ttls->rx_pkt_buf) {
if (
((flags & EAP_TTLS_FLAG_M) &&
ttls->rx_pkt_received + len >=
ttls->rx_pkt_len) ||
(!(flags & EAP_TTLS_FLAG_M) &&
ttls->rx_pkt_received + len !=
ttls->rx_pkt_len)) {
l_error("EAP-TTLS request fragment length mismatch");
l_free(ttls->rx_pkt_buf);
ttls->rx_pkt_buf = NULL;
goto err;
}
memcpy(ttls->rx_pkt_buf + ttls->rx_pkt_received, pkt, len);
ttls->rx_pkt_received += len;
}
if (flags & EAP_TTLS_FLAG_M) {
uint8_t buf[6];
/* Send an empty response as ACK */
buf[5] = 0;
eap_send_response(eap, EAP_TYPE_TTLS, buf, 6);
return;
}
if (ttls->rx_pkt_buf) {
pkt = ttls->rx_pkt_buf;
len = ttls->rx_pkt_len;
}
eap_ttls_tx_buf_reserve(ttls, EAP_TTLS_RESPONSE_HEADER_LEN);
ttls->tx_pkt_offset = ttls->tx_pkt_len;
ttls->tx_pkt_len = 0;
if (flags & EAP_TTLS_FLAG_S) {
ttls->tls = l_tls_new(false, eap_ttls_data_cb,
eap_ttls_tx_cb, eap_ttls_ready_cb,
eap_ttls_disconnect_cb, eap);
if (!ttls->tls) {
l_error("Creating a TLS instance failed");
goto err;
}
l_tls_set_auth_data(ttls->tls, ttls->client_cert,
ttls->client_key, ttls->passphrase);
if (ttls->ca_cert)
l_tls_set_cacert(ttls->tls, ttls->ca_cert);
/*
* RFC5281 section 9.1: "For all packets other than a
* Start packet, the Data field consists of the raw
* TLS message sequence or fragment thereof. For a
* Start packet, the Data field may optionally
* contain an AVP sequence."
* We ignore the unencrypted AVP sequence if there is
* any.
*/
len = 0;
}
/*
* Here we take advantage of knowing that ell will send all the
* records corresponding to the current handshake step from within
* the l_tls_handle_rx call because it doesn't use any other context
* such as timers - basic TLS specifies no timeouts. Otherwise we
* would need to analyze the record types in eap_ttls_tx_cb to decide
* when we're ready to send out a response.
*/
if (len)
l_tls_handle_rx(ttls->tls, pkt, len);
if (ttls->rx_pkt_buf) {
l_free(ttls->rx_pkt_buf);
ttls->rx_pkt_buf = NULL;
}
/*
* Note if ttls->completed && !eap->method_success we can send an empty
* response instead of passing the TLS alert.
*/
if (ttls->tx_pkt_len <= eap_get_mtu(eap)) {
/*
* Response fits in a single response packet, prepend the
* 6-byte header (no length) before the data.
*/
tx_buf = &ttls->tx_pkt_buf[ttls->tx_pkt_offset - 6];
tx_buf[5] = ttls->negotiated_version; /* Flags */
eap_send_response(eap, EAP_TYPE_TTLS,
tx_buf, ttls->tx_pkt_len + 6);
ttls->tx_pkt_len = 0;
} else {
/*
* Fragmentation needed, prepend the 10-byte header
* (4 EAP header + 2 response + 4 length) to build the
* initial fragment packet.
*/
tx_buf = &ttls->tx_pkt_buf[ttls->tx_pkt_offset - 10];
tx_buf[5] = EAP_TTLS_FLAG_L | EAP_TTLS_FLAG_M |
ttls->negotiated_version; /* Flags */
l_put_be32(ttls->tx_pkt_len, &tx_buf[6]);
fragment_len = eap_get_mtu(eap) - 10;
eap_send_response(eap, EAP_TYPE_TTLS,
tx_buf, fragment_len + 10);
ttls->tx_pkt_len -= fragment_len;
ttls->tx_pkt_offset += fragment_len;
}
if (ttls->completed) {
l_tls_free(ttls->tls);
ttls->tls = NULL;
if (ttls->eap) {
eap_free(ttls->eap);
ttls->eap = NULL;
}
}
return;
err:
ttls->completed = true;
l_tls_free(ttls->tls);
ttls->tls = NULL;
eap_method_error(eap);
}
static bool eap_ttls_load_settings(struct eap_state *eap,
struct l_settings *settings,
const char *prefix)
{
struct eap_ttls_state *ttls = eap_get_data(eap);
char setting[64];
snprintf(setting, sizeof(setting), "%sTTLS-CACert", prefix);
ttls->ca_cert = l_strdup(l_settings_get_value(settings,
"Security", setting));
snprintf(setting, sizeof(setting), "%sTTLS-ClientCert", prefix);
ttls->client_cert = l_strdup(l_settings_get_value(settings,
"Security", setting));
snprintf(setting, sizeof(setting), "%sTTLS-ClientKey", prefix);
ttls->client_key = l_strdup(l_settings_get_value(settings,
"Security", setting));
snprintf(setting, sizeof(setting), "%sTTLS-ClientKeyPassphrase",
prefix);
ttls->passphrase = l_strdup(l_settings_get_value(settings,
"Security", setting));
if (!ttls->client_cert && ttls->client_key) {
l_error("Client key present but no client certificate");
return false;
}
if (!ttls->client_key && ttls->passphrase) {
l_error("Passphrase present but no client private key");
return false;
}
ttls->eap = eap_new(eap_ttls_eap_tx_packet,
eap_ttls_eap_complete, eap);
if (!ttls->eap) {
l_error("Could not create the TTLS inner EAP instance");
return false;
}
snprintf(setting, sizeof(setting), "%sTTLS-Phase2-", prefix);
return eap_load_settings(ttls->eap, settings, setting);
}
struct eap_method eap_ttls = {
.request_type = EAP_TYPE_TTLS,
.exports_msk = true,
.name = "TTLS",
.probe = eap_ttls_probe,
.remove = eap_ttls_remove,
.handle_request = eap_ttls_handle_request,
.load_settings = eap_ttls_load_settings,
};

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@ -417,6 +417,7 @@ void eap_init(void) {
eap_register_method(&eap_md5);
eap_register_method(&eap_tls);
eap_register_method(&eap_ttls);
}
void eap_exit(void) {

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@ -120,3 +120,4 @@ void eap_restore_last_id(struct eap_state *eap, uint8_t last_id);
extern struct eap_method eap_md5;
extern struct eap_method eap_tls;
extern struct eap_method eap_ttls;