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strongswan-ext/src/charon/sa/authenticators/eap/eap_sim.c
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/**
* @file eap_sim.c
*
* @brief Implementation of eap_sim_t.
*
*/
/*
* Copyright (C) 2007 Martin Willi
* Hochschule fuer Technik Rapperswil
*
* 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. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* 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.
*/
#include "eap_sim.h"
#include <dlfcn.h>
#include <daemon.h>
#include <library.h>
#define MAX_TRIES 3
ENUM(sim_subtype_names, SIM_START, SIM_CLIENT_ERROR,
"SIM_START",
"SIM_CHALLENGE",
"SIM_NOTIFICATION",
"SIM_13",
"SIM_CLIENT_ERROR",
);
ENUM_BEGIN(sim_attribute_names, AT_END, AT_CLIENT_ERROR_CODE,
"AT_END",
"AT_0",
"AT_RAND",
"AT_AUTN",
"AT_RES",
"AT_AUTS",
"AT_5",
"AT_PADDING",
"AT_NONCE_MT",
"AT_8",
"AT_9",
"AT_PERMANENT_ID_REQ",
"AT_MAC",
"AT_NOTIFICATION",
"AT_ANY_ID_REQ",
"AT_IDENTITY",
"AT_VERSION_LIST",
"AT_SELECTED_VERSION",
"AT_FULLAUTH_ID_REQ",
"AT_18",
"AT_COUNTER",
"AT_COUNTER_TOO_SMALL",
"AT_NONCE_S",
"AT_CLIENT_ERROR_CODE");
ENUM_NEXT(sim_attribute_names, AT_IV, AT_RESULT_IND, AT_CLIENT_ERROR_CODE,
"AT_IV",
"AT_ENCR_DATA",
"AT_131",
"AT_NEXT_PSEUDONYM",
"AT_NEXT_REAUTH_ID",
"AT_CHECKCODE",
"AT_RESULT_IND");
ENUM_END(sim_attribute_names, AT_RESULT_IND);
typedef struct private_eap_sim_t private_eap_sim_t;
/**
* Private data of an eap_sim_t object.
*/
struct private_eap_sim_t {
/**
* Public authenticator_t interface.
*/
eap_sim_t public;
/**
* ID of ourself
*/
identification_t *peer;
/**
* SIM cardreader function loaded from library
*/
sim_algo_t alg;
/**
* handle of the loaded library
*/
void *handle;
/**
* how many times we try to authenticate
*/
int tries;
/**
* version this implementation uses
*/
chunk_t version;
/**
* version list received from server
*/
chunk_t version_list;
/**
* Nonce value used in AT_NONCE_MT
*/
chunk_t nonce;
/**
* k_encr key derived from MK
*/
chunk_t k_encr;
/**
* k_auth key derived from MK, used for AT_MAC verification
*/
chunk_t k_auth;
/**
* MSK, used for EAP-SIM based IKEv2 authentication
*/
chunk_t msk;
/**
* EMSK, extendes MSK for further uses
*/
chunk_t emsk;
};
/** length of the AT_NONCE_MT nonce value */
#define NONCE_LEN 16
/** length of the AT_MAC value */
#define MAC_LEN 16
/** length of the AT_RAND value */
#define RAND_LEN 16
/** length of the k_encr key */
#define KENCR_LEN 16
/** length of the k_auth key */
#define KAUTH_LEN 16
/** length of the MSK */
#define MSK_LEN 64
/** length of the EMSK */
#define EMSK_LEN 64
/* client error codes used in AT_CLIENT_ERROR_CODE */
char client_error_general_buf[] = {0x00, 0x01};
char client_error_unsupported_buf[] = {0x00, 0x02};
char client_error_insufficient_buf[] = {0x00, 0x03};
char client_error_notfresh_buf[] = {0x00, 0x04};
chunk_t client_error_general = chunk_from_buf(client_error_general_buf);
chunk_t client_error_unsupported = chunk_from_buf(client_error_unsupported_buf);
chunk_t client_error_insufficient = chunk_from_buf(client_error_insufficient_buf);
chunk_t client_error_notfresh = chunk_from_buf(client_error_notfresh_buf);
/**
* Read EAP and EAP-SIM header, return SIM type
*/
static sim_subtype_t read_header(chunk_t *message)
{
sim_subtype_t type;
if (message->len < 8)
{
*message = chunk_empty;
return 0;
}
type = *(message->ptr + 5);
*message = chunk_skip(*message, 8);
return type;
}
/**
* read the next attribute from the chunk data
*/
static sim_attribute_t read_attribute(chunk_t *message, chunk_t *data)
{
sim_attribute_t attribute;
size_t length;
DBG3(DBG_IKE, "reading attribute from %B", message);
if (message->len < 2)
{
return AT_END;
}
attribute = *message->ptr++;
length = *message->ptr++ * 4 - 2;
message->len -= 2;
DBG3(DBG_IKE, "found attribute %N with length %d",
sim_attribute_names, attribute, length);
if (length > message->len)
{
return AT_END;
}
data->len = length;
data->ptr = message->ptr;
*message = chunk_skip(*message, length);
return attribute;
}
/**
* Build an EAP-SIM payload using a variable length attribute list.
* The variable argument takes a sim_attribute_t followed by its data in a chunk.
*/
static eap_payload_t *build_payload(private_eap_sim_t *this, u_int8_t identifier,
sim_subtype_t type, ...)
{
chunk_t message = chunk_alloca(512);
chunk_t pos = message;
eap_payload_t *payload;
va_list args;
sim_attribute_t attr;
u_int8_t *mac_pos = NULL;
chunk_t mac_data = chunk_empty;
/* write EAP header, skip length bytes */
*pos.ptr++ = EAP_RESPONSE;
*pos.ptr++ = identifier;
pos.ptr += 2;
pos.len -= 4;
/* write SIM header with type and subtype, zero reserved bytes */
*pos.ptr++ = EAP_SIM;
*pos.ptr++ = type;
*pos.ptr++ = 0;
*pos.ptr++ = 0;
pos.len -= 4;
va_start(args, type);
while ((attr = va_arg(args, sim_attribute_t)) != AT_END)
{
chunk_t data = va_arg(args, chunk_t);
DBG3(DBG_IKE, "building %N %B", sim_attribute_names, attr, &data);
/* write attribute header */
*pos.ptr++ = attr;
pos.len--;
switch (attr)
{
case AT_CLIENT_ERROR_CODE:
case AT_SELECTED_VERSION:
{
*pos.ptr = data.len/4 + 1;
pos = chunk_skip(pos, 1);
memcpy(pos.ptr, data.ptr, data.len);
pos = chunk_skip(pos, data.len);
break;
}
case AT_IDENTITY:
{
u_int16_t act_len = data.len;
/* align up to four byte */
if (data.len % 4)
{
chunk_t tmp = chunk_alloca((data.len/4)*4 + 4);
memset(tmp.ptr, 0, tmp.len);
memcpy(tmp.ptr, data.ptr, data.len);
data = tmp;
}
*pos.ptr = data.len/4 + 1;
pos = chunk_skip(pos, 1);
/* actual length in bytes */
*(u_int16_t*)pos.ptr = htons(act_len);
pos = chunk_skip(pos, sizeof(u_int16_t));
memcpy(pos.ptr, data.ptr, data.len);
pos = chunk_skip(pos, data.len);
break;
}
case AT_NONCE_MT:
{
*pos.ptr = data.len/4 + 1;
pos = chunk_skip(pos, 1);
memset(pos.ptr, 0, 2);
pos = chunk_skip(pos, 2);
memcpy(pos.ptr, data.ptr, data.len);
pos = chunk_skip(pos, data.len);
break;
}
case AT_MAC:
{
*pos.ptr++ = 5; pos.len--;
*pos.ptr++ = 0; pos.len--;
*pos.ptr++ = 0; pos.len--;
mac_pos = pos.ptr;
memset(mac_pos, 0, MAC_LEN);
pos = chunk_skip(pos, MAC_LEN);
mac_data = data;
break;
}
case AT_RAND:
{
*pos.ptr++ = data.len/4 + 1; pos.len--;
*pos.ptr++ = 0; pos.len--;
*pos.ptr++ = 0; pos.len--;
memcpy(pos.ptr, data.ptr, data.len);
pos = chunk_skip(pos, data.len);
break;
}
default:
DBG1(DBG_IKE, "no rule to build EAP_SIM attribute %N, skipped",
sim_attribute_names, attr);
break;
}
}
va_end(args);
/* calculate message length, write into header */
message.len = pos.ptr - message.ptr;
*(u_int16_t*)(message.ptr + 2) = htons(message.len);
/* create MAC if AT_MAC attribte was included. Append supplied va_arg
* chunk mac_data to "to-sign" chunk */
if (mac_pos)
{
signer_t *signer = signer_create(AUTH_HMAC_SHA1_128);
signer->set_key(signer, this->k_auth);
mac_data = chunk_cata("cc", message, mac_data);
signer->get_signature(signer, mac_data, mac_pos);
DBG3(DBG_IKE, "AT_MAC signature of %B\n is %b",
&mac_data, mac_pos, MAC_LEN);
signer->destroy(signer);
}
payload = eap_payload_create_data(message);
DBG3(DBG_IKE, "created EAP message %B", &message);
return payload;
}
/**
* process an EAP-SIM/Request/Start message
*/
static status_t process_start(private_eap_sim_t *this, eap_payload_t *in,
eap_payload_t **out)
{
chunk_t message, data;
sim_attribute_t attribute, include_id = AT_END;
u_int8_t identifier;
identifier = in->get_identifier(in);
message = in->get_data(in);
read_header(&message);
while ((attribute = read_attribute(&message, &data)) != AT_END)
{
switch (attribute)
{
case AT_VERSION_LIST:
{
/* check if server supports our implementation */
bool found = FALSE;
if (data.len > 2)
{
/* read actual length first */
data.len = min(data.len, ntohs(*(u_int16_t*)data.ptr) + 2);
data = chunk_skip(data, 2);
chunk_free(&this->version_list);
this->version_list = chunk_clone(data);
while (data.len >= this->version.len)
{
if (memeq(data.ptr, this->version.ptr, this->version.len))
{
found = TRUE;
break;
}
data = chunk_skip(data, this->version.len);
}
}
if (!found)
{
DBG1(DBG_IKE, "server does not support EAP_SIM "
"version number %#B", &this->version);
*out = build_payload(this, identifier, SIM_CLIENT_ERROR,
AT_CLIENT_ERROR_CODE, client_error_unsupported,
AT_END);
return NEED_MORE;
}
break;
}
case AT_PERMANENT_ID_REQ:
case AT_FULLAUTH_ID_REQ:
case AT_ANY_ID_REQ:
/* only include AT_IDENTITY if requested */
include_id = AT_IDENTITY;
break;
case AT_NOTIFICATION:
{
u_int16_t code = 0;
if (data.len == 2)
{
code = ntohs(*(u_int16_t*)data.ptr);
}
if (code <= 32767) /* no success bit */
{
DBG1(DBG_IKE, "received %N error %d",
sim_attribute_names, attribute, code);
*out = build_payload(this,
in->get_identifier(in), SIM_CLIENT_ERROR,
AT_CLIENT_ERROR_CODE, client_error_general,
AT_END);
return NEED_MORE;
}
else
{
DBG1(DBG_IKE, "received %N code %d",
sim_attribute_names, attribute, code);
}
break;
}
default:
DBG1(DBG_IKE, "ignoring EAP_SIM attribute %N",
sim_attribute_names, attribute);
break;
}
}
/* build payload. If "include_id" is AT_END, AT_IDENTITY is ommited */
*out = build_payload(this, identifier, SIM_START,
AT_SELECTED_VERSION, this->version,
AT_NONCE_MT, this->nonce,
include_id, this->peer->get_encoding(this->peer),
AT_END);
return NEED_MORE;
}
/**
* process an EAP-SIM/Request/Challenge message
*/
static status_t process_challenge(private_eap_sim_t *this, eap_payload_t *in,
eap_payload_t **out)
{
chunk_t message, data, tmp, kcs, kc, sreses, sres, mk;
sim_attribute_t attribute;
u_int8_t identifier, i;
chunk_t mac = chunk_empty, rands = chunk_empty;
signer_t *signer;
hasher_t *hasher;
prf_t *prf;
if (this->tries-- <= 0)
{
/* give up without notification. This hack is required as some buggy
* server implementations won't respect our client-error. */
return FAILED;
}
identifier = in->get_identifier(in);
message = in->get_data(in);
read_header(&message);
while ((attribute = read_attribute(&message, &data)) != AT_END)
{
switch (attribute)
{
case AT_RAND:
{
rands = chunk_skip(data, 2);
break;
}
case AT_MAC:
{
/* backup MAC, zero it inline for later verification */
data = chunk_skip(data, 2);
mac = chunk_clonea(data);
memset(data.ptr, 0, data.len);
break;
}
case AT_NOTIFICATION:
{
u_int16_t code = 0;
if (data.len == 2)
{
code = ntohs(*(u_int16_t*)data.ptr);
}
if (code <= 32767) /* no success bit */
{
DBG1(DBG_IKE, "received %N error %d",
sim_attribute_names, attribute, code);
*out = build_payload(this,
in->get_identifier(in), SIM_CLIENT_ERROR,
AT_CLIENT_ERROR_CODE, client_error_general,
AT_END);
return NEED_MORE;
}
else
{
DBG1(DBG_IKE, "received %N code %d",
sim_attribute_names, attribute, code);
}
break;
}
default:
DBG1(DBG_IKE, "ignoring EAP_SIM attribute %N",
sim_attribute_names, attribute);
break;
}
}
/* excepting two or three RAND, each 16 bytes. We require two valid
* and different RANDs */
if ((rands.len != 2 * RAND_LEN && rands.len != 3 * RAND_LEN) ||
memeq(rands.ptr, rands.ptr + RAND_LEN, RAND_LEN))
{
DBG1(DBG_IKE, "no valid AT_RAND received");
*out = build_payload(this, identifier, SIM_CLIENT_ERROR,
AT_CLIENT_ERROR_CODE, client_error_insufficient,
AT_END);
return NEED_MORE;
}
if (mac.len != MAC_LEN)
{
DBG1(DBG_IKE, "no valid AT_MAC received");
*out = build_payload(this, identifier, SIM_CLIENT_ERROR,
AT_CLIENT_ERROR_CODE, client_error_general,
AT_END);
return NEED_MORE;
}
/* get two or three KCs/SRESes from SIM using RANDs */
kcs = kc = chunk_alloca(rands.len / 2);
sreses = sres = chunk_alloca(rands.len / 4);
while (rands.len > 0)
{
int kc_len = kc.len, sres_len = sres.len;
if (this->alg(rands.ptr, RAND_LEN, sres.ptr, &sres_len, kc.ptr, &kc_len))
{
DBG1(DBG_IKE, "unable to get triplets from SIM");
*out = build_payload(this, identifier, SIM_CLIENT_ERROR,
AT_CLIENT_ERROR_CODE, client_error_general,
AT_END);
return NEED_MORE;
}
DBG3(DBG_IKE, "got triplet for RAND %b\n Kc %b\n SRES %b",
rands.ptr, RAND_LEN, sres.ptr, sres_len, kc.ptr, kc_len);
kc = chunk_skip(kc, kc_len);
sres = chunk_skip(sres, sres_len);
rands = chunk_skip(rands, RAND_LEN);
}
/* build MK = SHA1(Identity|n*Kc|NONCE_MT|Version List|Selected Version) */
tmp = chunk_cata("ccccc", this->peer->get_encoding(this->peer), kcs,
this->nonce, this->version_list, this->version);
hasher = hasher_create(HASH_SHA1);
mk = chunk_alloca(hasher->get_hash_size(hasher));
hasher->get_hash(hasher, tmp, mk.ptr);
hasher->destroy(hasher);
DBG3(DBG_IKE, "MK = SHA1(%B\n) = %B", &tmp, &mk);
/* K_encr | K_auth | MSK | EMSK = prf() | prf() | prf() | prf()
* FIPS PRF has 320 bit block size, we need 160 byte for keys
* => run prf four times */
prf = prf_create(PRF_FIPS_SHA1_160);
prf->set_key(prf, mk);
tmp = chunk_alloca(prf->get_block_size(prf) * 4);
for (i = 0; i < 4; i++)
{
prf->get_bytes(prf, chunk_empty, tmp.ptr + tmp.len / 4 * i);
}
prf->destroy(prf);
chunk_free(&this->k_encr);
chunk_free(&this->k_auth);
chunk_free(&this->msk);
chunk_free(&this->emsk);
chunk_split(tmp, "aaaa", KENCR_LEN, &this->k_encr, KAUTH_LEN, &this->k_auth,
MSK_LEN, &this->msk, EMSK_LEN, &this->emsk);
DBG3(DBG_IKE, "K_encr %B\nK_auth %B\nMSK %B\nEMSK %B",
&this->k_encr, &this->k_auth, &this->msk, &this->emsk);
/* verify AT_MAC attribute, signature is over "EAP packet | NONCE_MT" */
signer = signer_create(AUTH_HMAC_SHA1_128);
signer->set_key(signer, this->k_auth);
tmp = chunk_cata("cc", in->get_data(in), this->nonce);
if (!signer->verify_signature(signer, tmp, mac))
{
DBG1(DBG_IKE, "AT_MAC verification failed");
signer->destroy(signer);
*out = build_payload(this, identifier, SIM_CLIENT_ERROR,
AT_CLIENT_ERROR_CODE, client_error_general,
AT_END);
return NEED_MORE;
}
signer->destroy(signer);
/* build response, AT_MAC is built over "EAP packet | n*SRES" */
*out = build_payload(this, identifier, SIM_CHALLENGE,
AT_MAC, sreses,
AT_END);
return NEED_MORE;
}
/**
* process an EAP-SIM/Request/Notification message
*/
static status_t process_notification(private_eap_sim_t *this, eap_payload_t *in,
eap_payload_t **out)
{
chunk_t message, data;
sim_attribute_t attribute;
message = in->get_data(in);
read_header(&message);
while ((attribute = read_attribute(&message, &data)) != AT_END)
{
switch (attribute)
{
case AT_NOTIFICATION:
{
u_int16_t code = 0;
if (data.len == 2)
{
code = ntohs(*(u_int16_t*)data.ptr);
}
if (code <= 32767) /* no success bit */
{
DBG1(DBG_IKE, "received %N error %d",
sim_attribute_names, attribute, code);
*out = build_payload(this,
in->get_identifier(in), SIM_CLIENT_ERROR,
AT_CLIENT_ERROR_CODE, client_error_general,
AT_END);
return NEED_MORE;
}
else
{
DBG1(DBG_IKE, "received %N code %d",
sim_attribute_names, attribute, code);
}
break;
}
default:
DBG1(DBG_IKE, "ignoring EAP_SIM attribute %N",
sim_attribute_names, attribute);
break;
}
}
/* reply with empty notification */
*out = build_payload(this, in->get_identifier(in), SIM_NOTIFICATION, AT_END);
return NEED_MORE;
}
/**
* Implementation of eap_method_t.process for the peer
*/
static status_t process(private_eap_sim_t *this,
eap_payload_t *in, eap_payload_t **out)
{
sim_subtype_t type;
chunk_t message;
message = in->get_data(in);
type = read_header(&message);
switch (type)
{
case SIM_START:
return process_start(this, in, out);
case SIM_CHALLENGE:
return process_challenge(this, in, out);
case SIM_NOTIFICATION:
return process_notification(this, in, out);
default:
DBG1(DBG_IKE, "unable to process EAP_SIM subtype %N",
sim_subtype_names, type);
*out = build_payload(this, in->get_identifier(in), SIM_CLIENT_ERROR,
AT_CLIENT_ERROR_CODE, client_error_general, AT_END);
return NEED_MORE;
}
}
/**
* Implementation of eap_method_t.initiate for the peer
*/
static status_t initiate(private_eap_sim_t *this, eap_payload_t **out)
{
/* peer never initiates */
return FAILED;
}
/**
* Implementation of eap_method_t.get_type.
*/
static eap_type_t get_type(private_eap_sim_t *this, u_int32_t *vendor)
{
*vendor = 0;
return EAP_SIM;
}
/**
* Implementation of eap_method_t.get_msk.
*/
static status_t get_msk(private_eap_sim_t *this, chunk_t *msk)
{
if (this->msk.ptr)
{
*msk = this->msk;
return SUCCESS;
}
return FAILED;
}
/**
* Implementation of eap_method_t.is_mutual.
*/
static bool is_mutual(private_eap_sim_t *this)
{
return TRUE;
}
/**
* Implementation of eap_method_t.destroy.
*/
static void destroy(private_eap_sim_t *this)
{
dlclose(this->handle);
chunk_free(&this->nonce);
chunk_free(&this->version_list);
chunk_free(&this->k_auth);
chunk_free(&this->k_encr);
chunk_free(&this->msk);
chunk_free(&this->emsk);
free(this);
}
/*
* Described in header.
*/
eap_sim_t *eap_create(eap_role_t role,
identification_t *server, identification_t *peer)
{
private_eap_sim_t *this;
randomizer_t *randomizer;
static char version[] = {0x00,0x01};
if (role != EAP_PEER)
{
return NULL;
}
this = malloc_thing(private_eap_sim_t);
this->handle = dlopen(SIM_READER_LIB, RTLD_LAZY);
if (this->handle == NULL)
{
DBG1(DBG_IKE, "unable to open SIM reader '%s'", SIM_READER_LIB);
free(this);
return NULL;
}
this->alg = dlsym(this->handle, SIM_READER_ALG);
if (this->alg == NULL)
{
DBG1(DBG_IKE, "unable to open SIM reader function '%s' in '%s'",
SIM_READER_ALG, SIM_READER_LIB);
dlclose(this->handle);
free(this);
return NULL;
}
randomizer = randomizer_create();
if (randomizer->allocate_pseudo_random_bytes(randomizer, NONCE_LEN,
&this->nonce))
{
DBG1(DBG_IKE, "unable to generate NONCE for EAP_SIM");
randomizer->destroy(randomizer);
free(this);
return NULL;
}
randomizer->destroy(randomizer);
/* public functions */
this->public.eap_method_interface.initiate = (status_t(*)(eap_method_t*,eap_payload_t**))initiate;
this->public.eap_method_interface.process = (status_t(*)(eap_method_t*,eap_payload_t*,eap_payload_t**))process;
this->public.eap_method_interface.get_type = (eap_type_t(*)(eap_method_t*,u_int32_t*))get_type;
this->public.eap_method_interface.is_mutual = (bool(*)(eap_method_t*))is_mutual;
this->public.eap_method_interface.get_msk = (status_t(*)(eap_method_t*,chunk_t*))get_msk;
this->public.eap_method_interface.destroy = (void(*)(eap_method_t*))destroy;
/* private data */
this->peer = peer;
this->tries = MAX_TRIES;
this->version.ptr = version;
this->version.len = sizeof(version);
this->version_list = chunk_empty;
this->k_auth = chunk_empty;
this->k_encr = chunk_empty;
this->msk = chunk_empty;
this->emsk = chunk_empty;
return &this->public;
}
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