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/**
* $Id$
* @file decrypt.c
* @brief Authentication for yubikey OTP tokens using the yubikey library.
*
* @author Arran Cudbard-Bell <a.cudbardb@networkradius.com>
* @copyright 2013 The FreeRADIUS server project
* @copyright 2013 Network RADIUS <info@networkradius.com>
*/
#include "rlm_yubikey.h"
#ifdef HAVE_YUBIKEY
/** Decrypt a Yubikey OTP AES block
*
* @param inst Module configuration.
* @param request The current request.
* @param passcode string to decrypt.
* @return one of the RLM_RCODE_* constants.
*/
rlm_rcode_t rlm_yubikey_decrypt(rlm_yubikey_t *inst, REQUEST *request, char const *passcode)
{
uint32_t counter;
yubikey_token_st token;
DICT_ATTR const *da;
char private_id[(YUBIKEY_UID_SIZE * 2) + 1];
VALUE_PAIR *key, *vp;
da = dict_attrbyname("Yubikey-Key");
if (!da) {
REDEBUG("Dictionary missing entry for 'Yubikey-Key'");
return RLM_MODULE_FAIL;
}
key = fr_pair_find_by_da(request->config, da, TAG_ANY);
if (!key) {
REDEBUG("Yubikey-Key attribute not found in control list, can't decrypt OTP data");
return RLM_MODULE_INVALID;
}
if (key->vp_length != YUBIKEY_KEY_SIZE) {
REDEBUG("Yubikey-Key length incorrect, expected %u got %zu", YUBIKEY_KEY_SIZE, key->vp_length);
return RLM_MODULE_INVALID;
}
yubikey_parse((uint8_t const *) passcode + inst->id_len, key->vp_octets, &token);
/*
* Apparently this just uses byte offsets...
*/
if (!yubikey_crc_ok_p((uint8_t *) &token)) {
REDEBUG("Decrypting OTP token data failed, rejecting");
return RLM_MODULE_REJECT;
}
RDEBUG("Token data decrypted successfully");
if (RDEBUG_ENABLED2) {
(void) fr_bin2hex((char *) &private_id, (uint8_t*) &token.uid, YUBIKEY_UID_SIZE);
RDEBUG2("Private ID : 0x%s", private_id);
RDEBUG2("Session counter : %u", yubikey_counter(token.ctr));
RDEBUG2("# used in session : %u", token.use);
RDEBUG2("Token timestamp : %u",
(token.tstph << 16) | token.tstpl);
RDEBUG2("Random data : %u", token.rnd);
RDEBUG2("CRC data : 0x%x", token.crc);
}
/*
* Private ID used for validation purposes
*/
vp = fr_pair_make(request->packet, &request->packet->vps, "Yubikey-Private-ID", NULL, T_OP_SET);
if (!vp) {
REDEBUG("Failed creating Yubikey-Private-ID");
return RLM_MODULE_FAIL;
}
fr_pair_value_memcpy(vp, token.uid, YUBIKEY_UID_SIZE);
/*
* Token timestamp
*/
vp = fr_pair_make(request->packet, &request->packet->vps, "Yubikey-Timestamp", NULL, T_OP_SET);
if (!vp) {
REDEBUG("Failed creating Yubikey-Timestamp");
return RLM_MODULE_FAIL;
}
vp->vp_integer = (token.tstph << 16) | token.tstpl;
vp->vp_length = 4;
/*
* Token random
*/
vp = fr_pair_make(request->packet, &request->packet->vps, "Yubikey-Random", NULL, T_OP_SET);
if (!vp) {
REDEBUG("Failed creating Yubikey-Random");
return RLM_MODULE_FAIL;
}
vp->vp_integer = token.rnd;
vp->vp_length = 4;
/*
* Combine the two counter fields together so we can do
* replay attack checks.
*/
counter = (yubikey_counter(token.ctr) << 8) | token.use;
vp = fr_pair_make(request->packet, &request->packet->vps, "Yubikey-Counter", NULL, T_OP_SET);
if (!vp) {
REDEBUG("Failed creating Yubikey-Counter");
return RLM_MODULE_FAIL;
}
vp->vp_integer = counter;
vp->vp_length = 4;
/*
* Now we check for replay attacks
*/
vp = fr_pair_find_by_da(request->config, vp->da, TAG_ANY);
if (!vp) {
RWDEBUG("Yubikey-Counter not found in control list, skipping replay attack checks");
return RLM_MODULE_OK;
}
if (counter <= vp->vp_integer) {
REDEBUG("Replay attack detected! Counter value %u, is lt or eq to last known counter value %u",
counter, vp->vp_integer);
return RLM_MODULE_REJECT;
}
return RLM_MODULE_OK;
}
#endif
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