aboutsummaryrefslogtreecommitdiffstats
path: root/src/kdc/kdc_preauth_ec.c
blob: 7e636b3f9fed2f1f90322869e534ca29f3460dc9 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* kdc/kdc_preauth_ec.c - Encrypted challenge kdcpreauth module */
/*
 * Copyright (C) 2009 by the Massachusetts Institute of Technology.
 * All rights reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 *
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 */

/*
 * Implement Encrypted Challenge fast factor from
 * draft-ietf-krb-wg-preauth-framework
 */

#include <k5-int.h>
#include <krb5/kdcpreauth_plugin.h>
#include "kdc_util.h"

static void
ec_edata(krb5_context context, krb5_kdc_req *request,
         krb5_kdcpreauth_callbacks cb, krb5_kdcpreauth_rock rock,
         krb5_kdcpreauth_moddata moddata, krb5_preauthtype pa_type,
         krb5_kdcpreauth_edata_respond_fn respond, void *arg)
{
    krb5_keyblock *armor_key = cb->fast_armor(context, rock);

    /* Encrypted challenge only works with FAST, and requires a client key. */
    if (armor_key == NULL || !cb->have_client_keys(context, rock))
        (*respond)(arg, ENOENT, NULL);
    else
        (*respond)(arg, 0, NULL);
}

static void
ec_verify(krb5_context context, krb5_data *req_pkt, krb5_kdc_req *request,
          krb5_enc_tkt_part *enc_tkt_reply, krb5_pa_data *data,
          krb5_kdcpreauth_callbacks cb, krb5_kdcpreauth_rock rock,
          krb5_kdcpreauth_moddata moddata,
          krb5_kdcpreauth_verify_respond_fn respond, void *arg)
{
    krb5_error_code retval = 0;
    krb5_enc_data *enc = NULL;
    krb5_data scratch, plain;
    krb5_keyblock *armor_key = cb->fast_armor(context, rock);
    krb5_pa_enc_ts *ts = NULL;
    krb5_keyblock *client_keys = NULL;
    krb5_keyblock *challenge_key = NULL;
    krb5_keyblock *kdc_challenge_key;
    krb5_kdcpreauth_modreq modreq = NULL;
    int i = 0;
    char *ai = NULL, *realmstr = NULL;
    krb5_data realm = request->server->realm;

    plain.data = NULL;

    if (armor_key == NULL) {
        retval = ENOENT;
        k5_setmsg(context, ENOENT,
                  _("Encrypted Challenge used outside of FAST tunnel"));
    }
    scratch.data = (char *) data->contents;
    scratch.length = data->length;
    if (retval == 0)
        retval = decode_krb5_enc_data(&scratch, &enc);
    if (retval == 0) {
        plain.data =  malloc(enc->ciphertext.length);
        plain.length = enc->ciphertext.length;
        if (plain.data == NULL)
            retval = ENOMEM;
    }

    /* Check for a configured FAST ec auth indicator. */
    realmstr = k5memdup0(realm.data, realm.length, &retval);
    if (realmstr != NULL)
        retval = profile_get_string(context->profile, KRB5_CONF_REALMS,
                                    realmstr,
                                    KRB5_CONF_ENCRYPTED_CHALLENGE_INDICATOR,
                                    NULL, &ai);

    if (retval == 0)
        retval = cb->client_keys(context, rock, &client_keys);
    if (retval == 0) {
        for (i = 0; client_keys[i].enctype&& (retval == 0); i++ ) {
            retval = krb5_c_fx_cf2_simple(context,
                                          armor_key, "clientchallengearmor",
                                          &client_keys[i], "challengelongterm",
                                          &challenge_key);
            if (retval == 0)
                retval  = krb5_c_decrypt(context, challenge_key,
                                         KRB5_KEYUSAGE_ENC_CHALLENGE_CLIENT,
                                         NULL, enc, &plain);
            if (challenge_key)
                krb5_free_keyblock(context, challenge_key);
            challenge_key = NULL;
            if (retval == 0)
                break;
            /*We failed to decrypt. Try next key*/
            retval = 0;
        }
        if (client_keys[i].enctype == 0) {
            retval = KRB5KDC_ERR_PREAUTH_FAILED;
            k5_setmsg(context, retval,
                      _("Incorrect password in encrypted challenge"));
        }
    }
    if (retval == 0)
        retval = decode_krb5_pa_enc_ts(&plain, &ts);
    if (retval == 0)
        retval = krb5_check_clockskew(context, ts->patimestamp);
    if (retval == 0) {
        enc_tkt_reply->flags |= TKT_FLG_PRE_AUTH;
        /*
         * If this fails, we won't generate a reply to the client.  That may
         * cause the client to fail, but at this point the KDC has considered
         * this a success, so the return value is ignored.
         */
        if (krb5_c_fx_cf2_simple(context, armor_key, "kdcchallengearmor",
                                 &client_keys[i], "challengelongterm",
                                 &kdc_challenge_key) == 0) {
            modreq = (krb5_kdcpreauth_modreq)kdc_challenge_key;
            if (ai != NULL)
                cb->add_auth_indicator(context, rock, ai);
        }
    }
    cb->free_keys(context, rock, client_keys);
    if (plain.data)
        free(plain.data);
    if (enc)
        krb5_free_enc_data(context, enc);
    if (ts)
        krb5_free_pa_enc_ts(context, ts);
    free(realmstr);
    free(ai);

    (*respond)(arg, retval, modreq, NULL, NULL);
}

static krb5_error_code
ec_return(krb5_context context, krb5_pa_data *padata, krb5_data *req_pkt,
          krb5_kdc_req *request, krb5_kdc_rep *reply,
          krb5_keyblock *encrypting_key, krb5_pa_data **send_pa,
          krb5_kdcpreauth_callbacks cb, krb5_kdcpreauth_rock rock,
          krb5_kdcpreauth_moddata moddata, krb5_kdcpreauth_modreq modreq)
{
    krb5_error_code retval = 0;
    krb5_keyblock *challenge_key = (krb5_keyblock *)modreq;
    krb5_pa_enc_ts ts;
    krb5_data *plain = NULL;
    krb5_enc_data enc;
    krb5_data *encoded = NULL;
    krb5_pa_data *pa = NULL;

    if (challenge_key == NULL)
        return 0;
    enc.ciphertext.data = NULL; /* In case of error pass through */

    retval = krb5_us_timeofday(context, &ts.patimestamp, &ts.pausec);
    if (retval == 0)
        retval = encode_krb5_pa_enc_ts(&ts, &plain);
    if (retval == 0)
        retval = krb5_encrypt_helper(context, challenge_key,
                                     KRB5_KEYUSAGE_ENC_CHALLENGE_KDC,
                                     plain, &enc);
    if (retval == 0)
        retval = encode_krb5_enc_data(&enc, &encoded);
    if (retval == 0) {
        pa = calloc(1, sizeof(krb5_pa_data));
        if (pa == NULL)
            retval = ENOMEM;
    }
    if (retval == 0) {
        pa->pa_type = KRB5_PADATA_ENCRYPTED_CHALLENGE;
        pa->contents = (unsigned char *) encoded->data;
        pa->length = encoded->length;
        encoded->data = NULL;
        *send_pa = pa;
        pa = NULL;
    }
    if (challenge_key)
        krb5_free_keyblock(context, challenge_key);
    if (encoded)
        krb5_free_data(context, encoded);
    if (plain)
        krb5_free_data(context, plain);
    if (enc.ciphertext.data)
        krb5_free_data_contents(context, &enc.ciphertext);
    return retval;
}

static krb5_preauthtype ec_types[] = {
    KRB5_PADATA_ENCRYPTED_CHALLENGE, 0};

krb5_error_code
kdcpreauth_encrypted_challenge_initvt(krb5_context context, int maj_ver,
                                      int min_ver, krb5_plugin_vtable vtable)
{
    krb5_kdcpreauth_vtable vt;

    if (maj_ver != 1)
        return KRB5_PLUGIN_VER_NOTSUPP;
    vt = (krb5_kdcpreauth_vtable)vtable;
    vt->name = "encrypted_challenge";
    vt->pa_type_list = ec_types;
    vt->edata = ec_edata;
    vt->verify = ec_verify;
    vt->return_padata = ec_return;
    return 0;
}