1/*
2 * Copyright (c) 2006 - 2007 Kungliga Tekniska H�gskolan
3 * (Royal Institute of Technology, Stockholm, Sweden).
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * 3. Neither the name of the Institute nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include "kdc_locl.h"
35#include <hex.h>
36#include <rfc2459_asn1.h>
37#include <hx509.h>
38
39RCSID("$Id: kx509.c 21607 2007-07-17 07:04:52Z lha $");
40
41/*
42 *
43 */
44
45krb5_error_code
46_kdc_try_kx509_request(void *ptr, size_t len, Kx509Request *req, size_t *size)
47{
48    if (len < 4)
49	return -1;
50    if (memcmp("\x00\x00\x02\x00", ptr, 4) != 0)
51	return -1;
52    return decode_Kx509Request(((unsigned char *)ptr) + 4, len - 4, req, size);
53}
54
55/*
56 *
57 */
58
59static const unsigned char version_2_0[4] = {0 , 0, 2, 0};
60
61static krb5_error_code
62verify_req_hash(krb5_context context,
63		const Kx509Request *req,
64		krb5_keyblock *key)
65{
66    unsigned char digest[SHA_DIGEST_LENGTH];
67    HMAC_CTX ctx;
68
69    if (req->pk_hash.length != sizeof(digest)) {
70	krb5_set_error_string(context, "pk-hash have wrong length: %lu",
71			      (unsigned long)req->pk_hash.length);
72	return KRB5KDC_ERR_PREAUTH_FAILED;
73    }
74
75    HMAC_CTX_init(&ctx);
76    HMAC_Init_ex(&ctx,
77		 key->keyvalue.data, key->keyvalue.length,
78		 EVP_sha1(), NULL);
79    if (sizeof(digest) != HMAC_size(&ctx))
80	krb5_abortx(context, "runtime error, hmac buffer wrong size in kx509");
81    HMAC_Update(&ctx, version_2_0, sizeof(version_2_0));
82    HMAC_Update(&ctx, req->pk_key.data, req->pk_key.length);
83    HMAC_Final(&ctx, digest, 0);
84    HMAC_CTX_cleanup(&ctx);
85
86    if (memcmp(req->pk_hash.data, digest, sizeof(digest)) != 0) {
87	krb5_set_error_string(context, "pk-hash is not correct");
88	return KRB5KDC_ERR_PREAUTH_FAILED;
89    }
90    return 0;
91}
92
93static krb5_error_code
94calculate_reply_hash(krb5_context context,
95		     krb5_keyblock *key,
96		     Kx509Response *rep)
97{
98    HMAC_CTX ctx;
99
100    HMAC_CTX_init(&ctx);
101
102    HMAC_Init_ex(&ctx,
103		 key->keyvalue.data, key->keyvalue.length,
104		 EVP_sha1(), NULL);
105    rep->hash->length = HMAC_size(&ctx);
106    rep->hash->data = malloc(rep->hash->length);
107    if (rep->hash->data == NULL) {
108	HMAC_CTX_cleanup(&ctx);
109	krb5_set_error_string(context, "out of memory");
110	return ENOMEM;
111    }
112
113    HMAC_Update(&ctx, version_2_0, sizeof(version_2_0));
114    if (rep->error_code) {
115	int32_t t = *rep->error_code;
116	do {
117	    unsigned char p = (t & 0xff);
118	    HMAC_Update(&ctx, &p, 1);
119	    t >>= 8;
120	} while (t);
121    }
122    if (rep->certificate)
123	HMAC_Update(&ctx, rep->certificate->data, rep->certificate->length);
124    if (rep->e_text)
125	HMAC_Update(&ctx, (unsigned char *)*rep->e_text, strlen(*rep->e_text));
126
127    HMAC_Final(&ctx, rep->hash->data, 0);
128    HMAC_CTX_cleanup(&ctx);
129
130    return 0;
131}
132
133/*
134 * Build a certifate for `principal� that will expire at `endtime�.
135 */
136
137static krb5_error_code
138build_certificate(krb5_context context,
139		  krb5_kdc_configuration *config,
140		  const krb5_data *key,
141		  time_t endtime,
142		  krb5_principal principal,
143		  krb5_data *certificate)
144{
145    hx509_context hxctx = NULL;
146    hx509_ca_tbs tbs = NULL;
147    hx509_env env = NULL;
148    hx509_cert cert = NULL;
149    hx509_cert signer = NULL;
150    int ret;
151
152    if (krb5_principal_get_comp_string(context, principal, 1) != NULL) {
153	kdc_log(context, config, 0, "Principal is not a user");
154	return EINVAL;
155    }
156
157    ret = hx509_context_init(&hxctx);
158    if (ret)
159	goto out;
160
161    ret = hx509_env_init(hxctx, &env);
162    if (ret)
163	goto out;
164
165    ret = hx509_env_add(hxctx, env, "principal-name",
166			krb5_principal_get_comp_string(context, principal, 0));
167    if (ret)
168	goto out;
169
170    {
171	hx509_certs certs;
172	hx509_query *q;
173
174	ret = hx509_certs_init(hxctx, config->kx509_ca, 0,
175			       NULL, &certs);
176	if (ret) {
177	    kdc_log(context, config, 0, "Failed to load CA %s",
178		    config->kx509_ca);
179	    goto out;
180	}
181	ret = hx509_query_alloc(hxctx, &q);
182	if (ret) {
183	    hx509_certs_free(&certs);
184	    goto out;
185	}
186
187	hx509_query_match_option(q, HX509_QUERY_OPTION_PRIVATE_KEY);
188	hx509_query_match_option(q, HX509_QUERY_OPTION_KU_KEYCERTSIGN);
189
190	ret = hx509_certs_find(hxctx, certs, q, &signer);
191	hx509_query_free(hxctx, q);
192	hx509_certs_free(&certs);
193	if (ret) {
194	    kdc_log(context, config, 0, "Failed to find a CA in %s",
195		    config->kx509_ca);
196	    goto out;
197	}
198    }
199
200    ret = hx509_ca_tbs_init(hxctx, &tbs);
201    if (ret)
202	goto out;
203
204    {
205	SubjectPublicKeyInfo spki;
206	heim_any any;
207
208	memset(&spki, 0, sizeof(spki));
209
210	spki.subjectPublicKey.data = key->data;
211	spki.subjectPublicKey.length = key->length * 8;
212
213	ret = der_copy_oid(oid_id_pkcs1_rsaEncryption(),
214			   &spki.algorithm.algorithm);
215
216	any.data = "\x05\x00";
217	any.length = 2;
218	spki.algorithm.parameters = &any;
219
220	ret = hx509_ca_tbs_set_spki(hxctx, tbs, &spki);
221	der_free_oid(&spki.algorithm.algorithm);
222	if (ret)
223	    goto out;
224    }
225
226    {
227	hx509_certs certs;
228	hx509_cert template;
229
230	ret = hx509_certs_init(hxctx, config->kx509_template, 0,
231			       NULL, &certs);
232	if (ret) {
233	    kdc_log(context, config, 0, "Failed to load template %s",
234		    config->kx509_template);
235	    goto out;
236	}
237	ret = hx509_get_one_cert(hxctx, certs, &template);
238	hx509_certs_free(&certs);
239	if (ret) {
240	    kdc_log(context, config, 0, "Failed to find template in %s",
241		    config->kx509_template);
242	    goto out;
243	}
244	ret = hx509_ca_tbs_set_template(hxctx, tbs,
245					HX509_CA_TEMPLATE_SUBJECT|
246					HX509_CA_TEMPLATE_KU|
247					HX509_CA_TEMPLATE_EKU,
248					template);
249	hx509_cert_free(template);
250	if (ret)
251	    goto out;
252    }
253
254    hx509_ca_tbs_set_notAfter(hxctx, tbs, endtime);
255
256    hx509_ca_tbs_subject_expand(hxctx, tbs, env);
257    hx509_env_free(&env);
258
259    ret = hx509_ca_sign(hxctx, tbs, signer, &cert);
260    hx509_cert_free(signer);
261    if (ret)
262	goto out;
263
264    hx509_ca_tbs_free(&tbs);
265
266    ret = hx509_cert_binary(hxctx, cert, certificate);
267    hx509_cert_free(cert);
268    if (ret)
269	goto out;
270
271    hx509_context_free(&hxctx);
272
273    return 0;
274out:
275    if (env)
276	hx509_env_free(&env);
277    if (tbs)
278	hx509_ca_tbs_free(&tbs);
279    if (signer)
280	hx509_cert_free(signer);
281    if (hxctx)
282	hx509_context_free(&hxctx);
283    krb5_set_error_string(context, "cert creation failed");
284    return ret;
285}
286
287/*
288 *
289 */
290
291krb5_error_code
292_kdc_do_kx509(krb5_context context,
293	      krb5_kdc_configuration *config,
294	      const Kx509Request *req, krb5_data *reply,
295	      const char *from, struct sockaddr *addr)
296{
297    krb5_error_code ret;
298    krb5_ticket *ticket = NULL;
299    krb5_flags ap_req_options;
300    krb5_auth_context ac = NULL;
301    krb5_keytab id = NULL;
302    krb5_principal sprincipal = NULL, cprincipal = NULL;
303    char *cname = NULL;
304    Kx509Response rep;
305    size_t size;
306    krb5_keyblock *key = NULL;
307
308    krb5_data_zero(reply);
309    memset(&rep, 0, sizeof(rep));
310
311    if(!config->enable_kx509) {
312	kdc_log(context, config, 0,
313		"Rejected kx509 request (disabled) from %s", from);
314	return KRB5KDC_ERR_POLICY;
315    }
316
317    kdc_log(context, config, 0, "Kx509 request from %s", from);
318
319    ret = krb5_kt_resolve(context, "HDB:", &id);
320    if (ret) {
321	kdc_log(context, config, 0, "Can't open database for digest");
322	goto out;
323    }
324
325    ret = krb5_rd_req(context,
326		      &ac,
327		      &req->authenticator,
328		      NULL,
329		      id,
330		      &ap_req_options,
331		      &ticket);
332    if (ret)
333	goto out;
334
335    ret = krb5_ticket_get_client(context, ticket, &cprincipal);
336    if (ret)
337	goto out;
338
339    ret = krb5_unparse_name(context, cprincipal, &cname);
340    if (ret)
341	goto out;
342
343    /* verify server principal */
344
345    ret = krb5_sname_to_principal(context, NULL, "kca_service",
346				  KRB5_NT_UNKNOWN, &sprincipal);
347    if (ret)
348	goto out;
349
350    {
351	krb5_principal principal = NULL;
352
353	ret = krb5_ticket_get_server(context, ticket, &principal);
354	if (ret)
355	    goto out;
356
357	ret = krb5_principal_compare(context, sprincipal, principal);
358	krb5_free_principal(context, principal);
359	if (ret != TRUE) {
360	    ret = KRB5KDC_ERR_SERVER_NOMATCH;
361	    krb5_set_error_string(context,
362				  "User %s used wrong Kx509 service principal",
363				  cname);
364	    goto out;
365	}
366    }
367
368    ret = krb5_auth_con_getkey(context, ac, &key);
369    if (ret || key == NULL) {
370	krb5_set_error_string(context, "Kx509 can't get session key");
371	goto out;
372    }
373
374    ret = verify_req_hash(context, req, key);
375    if (ret)
376	goto out;
377
378    /* Verify that the key is encoded RSA key */
379    {
380	RSAPublicKey key;
381	size_t size;
382
383	ret = decode_RSAPublicKey(req->pk_key.data, req->pk_key.length,
384				  &key, &size);
385	if (ret)
386	    goto out;
387	free_RSAPublicKey(&key);
388	if (size != req->pk_key.length)
389	    ;
390    }
391
392    ALLOC(rep.certificate);
393    if (rep.certificate == NULL)
394	goto out;
395    krb5_data_zero(rep.certificate);
396    ALLOC(rep.hash);
397    if (rep.hash == NULL)
398	goto out;
399    krb5_data_zero(rep.hash);
400
401    ret = build_certificate(context, config, &req->pk_key,
402			    krb5_ticket_get_endtime(context, ticket),
403			    cprincipal, rep.certificate);
404    if (ret)
405	goto out;
406
407    ret = calculate_reply_hash(context, key, &rep);
408    if (ret)
409	goto out;
410
411    /*
412     * Encode reply, [ version | Kx509Response ]
413     */
414
415    {
416	krb5_data data;
417
418	ASN1_MALLOC_ENCODE(Kx509Response, data.data, data.length, &rep,
419			   &size, ret);
420	if (ret) {
421	    krb5_set_error_string(context, "Failed to encode kx509 reply");
422	    goto out;
423	}
424	if (size != data.length)
425	    krb5_abortx(context, "ASN1 internal error");
426
427	ret = krb5_data_alloc(reply, data.length + sizeof(version_2_0));
428	if (ret) {
429	    free(data.data);
430	    goto out;
431	}
432	memcpy(reply->data, version_2_0, sizeof(version_2_0));
433	memcpy(((unsigned char *)reply->data) + sizeof(version_2_0),
434	       data.data, data.length);
435	free(data.data);
436    }
437
438    kdc_log(context, config, 0, "Successful Kx509 request for %s", cname);
439
440out:
441    if (ac)
442	krb5_auth_con_free(context, ac);
443    if (ret)
444	krb5_warn(context, ret, "Kx509 request from %s failed", from);
445    if (ticket)
446	krb5_free_ticket(context, ticket);
447    if (id)
448	krb5_kt_close(context, id);
449    if (sprincipal)
450	krb5_free_principal(context, sprincipal);
451    if (cprincipal)
452	krb5_free_principal(context, cprincipal);
453    if (key)
454	krb5_free_keyblock (context, key);
455    if (cname)
456	free(cname);
457    free_Kx509Response(&rep);
458
459    return 0;
460}
461