1/*	$NetBSD: kx509.c,v 1.4 2023/06/19 21:41:42 christos Exp $	*/
2
3/*
4 * Copyright (c) 2006 - 2007 Kungliga Tekniska H��gskolan
5 * (Royal Institute of Technology, Stockholm, Sweden).
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * 3. Neither the name of the Institute nor the names of its contributors
20 *    may be used to endorse or promote products derived from this software
21 *    without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36#include "kdc_locl.h"
37#include <krb5/hex.h>
38#include <krb5/rfc2459_asn1.h>
39#include <krb5/hx509.h>
40
41#ifdef KX509
42
43/*
44 *
45 */
46
47krb5_error_code
48_kdc_try_kx509_request(void *ptr, size_t len, struct Kx509Request *req, size_t *size)
49{
50    if (len < 4)
51	return -1;
52    if (memcmp("\x00\x00\x02\x00", ptr, 4) != 0)
53	return -1;
54    return decode_Kx509Request(((unsigned char *)ptr) + 4, len - 4, req, size);
55}
56
57/*
58 *
59 */
60
61static const unsigned char version_2_0[4] = {0 , 0, 2, 0};
62
63static krb5_error_code
64verify_req_hash(krb5_context context,
65		const Kx509Request *req,
66		krb5_keyblock *key)
67{
68    unsigned char digest[SHA_DIGEST_LENGTH];
69    HMAC_CTX *ctx;
70
71    if (req->pk_hash.length != sizeof(digest)) {
72	krb5_set_error_message(context, KRB5KDC_ERR_PREAUTH_FAILED,
73			       "pk-hash have wrong length: %lu",
74			       (unsigned long)req->pk_hash.length);
75	return KRB5KDC_ERR_PREAUTH_FAILED;
76    }
77
78#if OPENSSL_VERSION_NUMBER < 0x10100000UL
79    HMAC_CTX ctxs;
80    ctx = &ctxs;
81    HMAC_CTX_init(ctx);
82#else
83    ctx = HMAC_CTX_new();
84#endif
85    HMAC_Init_ex(ctx,
86		 key->keyvalue.data, key->keyvalue.length,
87		 EVP_sha1(), NULL);
88    if (sizeof(digest) != HMAC_size(ctx))
89	krb5_abortx(context, "runtime error, hmac buffer wrong size in kx509");
90    HMAC_Update(ctx, version_2_0, sizeof(version_2_0));
91    HMAC_Update(ctx, req->pk_key.data, req->pk_key.length);
92    HMAC_Final(ctx, digest, 0);
93#if OPENSSL_VERSION_NUMBER < 0x10100000UL
94    HMAC_CTX_cleanup(ctx);
95#else
96    HMAC_CTX_free(ctx);
97#endif
98
99    if (memcmp(req->pk_hash.data, digest, sizeof(digest)) != 0) {
100	krb5_set_error_message(context, KRB5KDC_ERR_PREAUTH_FAILED,
101			       "pk-hash is not correct");
102	return KRB5KDC_ERR_PREAUTH_FAILED;
103    }
104    return 0;
105}
106
107static krb5_error_code
108calculate_reply_hash(krb5_context context,
109		     krb5_keyblock *key,
110		     Kx509Response *rep)
111{
112    krb5_error_code ret;
113    HMAC_CTX *ctx;
114
115#if OPENSSL_VERSION_NUMBER < 0x10100000UL
116    HMAC_CTX ctxs;
117    ctx = &ctxs;
118    HMAC_CTX_init(ctx);
119#else
120    ctx = HMAC_CTX_new();
121#endif
122
123    HMAC_Init_ex(ctx, key->keyvalue.data, key->keyvalue.length,
124		 EVP_sha1(), NULL);
125    ret = krb5_data_alloc(rep->hash, HMAC_size(ctx));
126    if (ret) {
127#if OPENSSL_VERSION_NUMBER < 0x10100000UL
128	HMAC_CTX_cleanup(ctx);
129#else
130	HMAC_CTX_free(ctx);
131#endif
132	krb5_set_error_message(context, ENOMEM, "malloc: out of memory");
133	return ENOMEM;
134    }
135
136    HMAC_Update(ctx, version_2_0, sizeof(version_2_0));
137    if (rep->error_code) {
138	int32_t t = *rep->error_code;
139	do {
140	    unsigned char p = (t & 0xff);
141	    HMAC_Update(ctx, &p, 1);
142	    t >>= 8;
143	} while (t);
144    }
145    if (rep->certificate)
146	HMAC_Update(ctx, rep->certificate->data, rep->certificate->length);
147    if (rep->e_text)
148	HMAC_Update(ctx, (unsigned char *)*rep->e_text, strlen(*rep->e_text));
149
150    HMAC_Final(ctx, rep->hash->data, 0);
151#if OPENSSL_VERSION_NUMBER < 0x10100000UL
152    HMAC_CTX_cleanup(ctx);
153#else
154    HMAC_CTX_free(ctx);
155#endif
156
157    return 0;
158}
159
160/*
161 * Build a certifate for `principal�� that will expire at `endtime��.
162 */
163
164static krb5_error_code
165build_certificate(krb5_context context,
166		  krb5_kdc_configuration *config,
167		  const krb5_data *key,
168		  time_t endtime,
169		  krb5_principal principal,
170		  krb5_data *certificate)
171{
172    char *name = NULL;
173    const char *kx509_ca;
174    hx509_ca_tbs tbs = NULL;
175    hx509_env env = NULL;
176    hx509_cert cert = NULL;
177    hx509_cert signer = NULL;
178    krb5_boolean def_bool;
179    int ret;
180
181    ret = krb5_unparse_name_flags(context, principal,
182				  KRB5_PRINCIPAL_UNPARSE_NO_REALM,
183				  &name);
184    if (ret)
185	goto out;
186
187    ret = hx509_env_add(context->hx509ctx, &env, "principal-name-without-realm",
188			name);
189    krb5_xfree(name);
190    name = NULL;
191    if (ret)
192	goto out;
193
194    /*
195     * Include the realm in the principal-name env var; the template
196     * might not use $principal-name-realm after all.
197     */
198    ret = krb5_unparse_name(context, principal, &name);
199    if (ret)
200	goto out;
201
202    ret = hx509_env_add(context->hx509ctx, &env, "principal-name",
203			name);
204    if (ret)
205	goto out;
206
207    ret = hx509_env_add(context->hx509ctx, &env, "principal-name-realm",
208			krb5_principal_get_realm(context, principal));
209    if (ret)
210	goto out;
211
212    /* Pick an issuer based on the crealm if we can */
213    kx509_ca = krb5_config_get_string(context, NULL, "kdc",
214                                      krb5_principal_get_realm(context,
215                                                               principal),
216                                      "kx509_ca", NULL);
217    if (kx509_ca == NULL)
218        kx509_ca = config->kx509_ca;
219
220    {
221	hx509_certs certs;
222	hx509_query *q;
223
224	ret = hx509_certs_init(context->hx509ctx, config->kx509_ca, 0,
225			       NULL, &certs);
226	if (ret) {
227	    kdc_log(context, config, 0, "Failed to load CA %s",
228		    config->kx509_ca);
229	    goto out;
230	}
231	ret = hx509_query_alloc(context->hx509ctx, &q);
232	if (ret) {
233	    hx509_certs_free(&certs);
234	    goto out;
235	}
236
237	hx509_query_match_option(q, HX509_QUERY_OPTION_PRIVATE_KEY);
238	hx509_query_match_option(q, HX509_QUERY_OPTION_KU_KEYCERTSIGN);
239
240	ret = hx509_certs_find(context->hx509ctx, certs, q, &signer);
241	hx509_query_free(context->hx509ctx, q);
242	hx509_certs_free(&certs);
243	if (ret) {
244	    kdc_log(context, config, 0, "Failed to find a CA in %s",
245		    config->kx509_ca);
246	    goto out;
247	}
248    }
249
250    ret = hx509_ca_tbs_init(context->hx509ctx, &tbs);
251    if (ret)
252	goto out;
253
254    {
255	SubjectPublicKeyInfo spki;
256	heim_any any;
257
258	memset(&spki, 0, sizeof(spki));
259
260	spki.subjectPublicKey.data = key->data;
261	spki.subjectPublicKey.length = key->length * 8;
262
263	ret = der_copy_oid(&asn1_oid_id_pkcs1_rsaEncryption,
264			   &spki.algorithm.algorithm);
265
266	any.data = "\x05\x00";
267	any.length = 2;
268	spki.algorithm.parameters = &any;
269
270	ret = hx509_ca_tbs_set_spki(context->hx509ctx, tbs, &spki);
271	der_free_oid(&spki.algorithm.algorithm);
272	if (ret)
273	    goto out;
274    }
275
276    {
277	hx509_certs certs;
278	hx509_cert template;
279
280	ret = hx509_certs_init(context->hx509ctx, config->kx509_template, 0,
281			       NULL, &certs);
282	if (ret) {
283	    kdc_log(context, config, 0, "Failed to load template %s",
284		    config->kx509_template);
285	    goto out;
286	}
287	ret = hx509_get_one_cert(context->hx509ctx, certs, &template);
288	hx509_certs_free(&certs);
289	if (ret) {
290	    kdc_log(context, config, 0, "Failed to find template in %s",
291		    config->kx509_template);
292	    goto out;
293	}
294	ret = hx509_ca_tbs_set_template(context->hx509ctx, tbs,
295					HX509_CA_TEMPLATE_SUBJECT|
296					HX509_CA_TEMPLATE_KU|
297					HX509_CA_TEMPLATE_EKU,
298					template);
299	hx509_cert_free(template);
300	if (ret)
301	    goto out;
302    }
303
304    def_bool = krb5_config_get_bool_default(context, NULL, TRUE, "kdc",
305                                            "kx509_include_pkinit_san",
306                                            NULL);
307    if (krb5_config_get_bool_default(context, NULL, def_bool, "kdc",
308                                     krb5_principal_get_realm(context,
309                                                              principal),
310                                     "kx509_include_pkinit_san",
311                                     NULL)) {
312        ret = hx509_ca_tbs_add_san_pkinit(context->hx509ctx, tbs, name);
313        if (ret)
314            goto out;
315    }
316
317    hx509_ca_tbs_set_notAfter(context->hx509ctx, tbs, endtime);
318
319    hx509_ca_tbs_subject_expand(context->hx509ctx, tbs, env);
320    hx509_env_free(&env);
321
322    ret = hx509_ca_sign(context->hx509ctx, tbs, signer, &cert);
323    hx509_cert_free(signer);
324    if (ret)
325	goto out;
326
327    hx509_ca_tbs_free(&tbs);
328
329    ret = hx509_cert_binary(context->hx509ctx, cert, certificate);
330    hx509_cert_free(cert);
331    if (ret)
332	goto out;
333
334    /* cleanup on success */
335    krb5_xfree(name);
336
337    return 0;
338out:
339    if (name)
340	krb5_xfree(name);
341    if (env)
342	hx509_env_free(&env);
343    if (tbs)
344	hx509_ca_tbs_free(&tbs);
345    if (signer)
346	hx509_cert_free(signer);
347    krb5_set_error_message(context, ret, "cert creation failed");
348    return ret;
349}
350
351krb5_error_code
352kdc_kx509_verify_service_principal(krb5_context context,
353				   const char *cname,
354				   krb5_principal sprincipal)
355{
356    krb5_error_code ret, aret;
357    krb5_boolean bret;
358    krb5_principal principal = NULL;
359    char *expected = NULL;
360    char localhost[MAXHOSTNAMELEN];
361
362    ret = gethostname(localhost, sizeof(localhost) - 1);
363    if (ret != 0) {
364	ret = errno;
365	krb5_set_error_message(context, ret,
366			       N_("Failed to get local hostname", ""));
367	return ret;
368    }
369    localhost[sizeof(localhost) - 1] = '\0';
370
371    ret = krb5_make_principal(context, &principal, "", "kca_service",
372			      localhost, NULL);
373    if (ret)
374	goto out;
375
376    bret = krb5_principal_compare_any_realm(context, sprincipal, principal);
377    if (bret == TRUE)
378	goto out;	/* found a match */
379
380    ret = KRB5KDC_ERR_SERVER_NOMATCH;
381
382    aret = krb5_unparse_name(context, sprincipal, &expected);
383    if (aret)
384	goto out;
385
386    krb5_set_error_message(context, ret,
387			   "User %s used wrong Kx509 service "
388			   "principal, expected: %s",
389			   cname, expected);
390
391  out:
392    krb5_xfree(expected);
393    krb5_free_principal(context, principal);
394
395    return ret;
396}
397
398/*
399 *
400 */
401
402krb5_error_code
403_kdc_do_kx509(krb5_context context,
404	      krb5_kdc_configuration *config,
405	      const struct Kx509Request *req, krb5_data *reply,
406	      const char *from, struct sockaddr *addr)
407{
408    krb5_error_code ret;
409    krb5_ticket *ticket = NULL;
410    krb5_flags ap_req_options;
411    krb5_auth_context ac = NULL;
412    krb5_keytab id = NULL;
413    krb5_principal sprincipal = NULL, cprincipal = NULL;
414    char *cname = NULL;
415    Kx509Response rep;
416    size_t size;
417    krb5_keyblock *key = NULL;
418    krb5_boolean def_bool;
419
420    krb5_data_zero(reply);
421    memset(&rep, 0, sizeof(rep));
422
423    if(!config->enable_kx509) {
424	kdc_log(context, config, 0,
425		"Rejected kx509 request (disabled) from %s", from);
426	return KRB5KDC_ERR_POLICY;
427    }
428
429    kdc_log(context, config, 0, "Kx509 request from %s", from);
430
431    ret = krb5_kt_resolve(context, "HDBGET:", &id);
432    if (ret) {
433	kdc_log(context, config, 0, "Can't open database for digest");
434	goto out;
435    }
436
437    ret = krb5_rd_req(context,
438		      &ac,
439		      &req->authenticator,
440		      NULL,
441		      id,
442		      &ap_req_options,
443		      &ticket);
444    if (ret)
445	goto out;
446
447    ret = krb5_ticket_get_client(context, ticket, &cprincipal);
448    if (ret)
449	goto out;
450
451    def_bool = krb5_config_get_bool_default(context, NULL, TRUE, "kdc",
452                                            "require_initial_kca_tickets",
453                                            NULL);
454    if (!ticket->ticket.flags.initial &&
455        krb5_config_get_bool_default(context, NULL, def_bool, "kdc",
456                                      krb5_principal_get_realm(context,
457                                                               cprincipal),
458                                      "require_initial_kca_tickets", NULL)) {
459        ret = KRB5KDC_ERR_POLICY;
460        goto out;
461    }
462
463    ret = krb5_unparse_name(context, cprincipal, &cname);
464    if (ret)
465	goto out;
466
467    ret = krb5_ticket_get_server(context, ticket, &sprincipal);
468    if (ret)
469	goto out;
470
471    ret = kdc_kx509_verify_service_principal(context, cname, sprincipal);
472    if (ret)
473	goto out;
474
475    ret = krb5_auth_con_getkey(context, ac, &key);
476    if (ret == 0 && key == NULL)
477	ret = KRB5KDC_ERR_NULL_KEY;
478    if (ret) {
479	krb5_set_error_message(context, ret, "Kx509 can't get session key");
480	goto out;
481    }
482
483    ret = verify_req_hash(context, req, key);
484    if (ret)
485	goto out;
486
487    /* Verify that the key is encoded RSA key */
488    {
489	RSAPublicKey rsapkey;
490	size_t rsapkeysize;
491
492	ret = decode_RSAPublicKey(req->pk_key.data, req->pk_key.length,
493				  &rsapkey, &rsapkeysize);
494	if (ret)
495	    goto out;
496	free_RSAPublicKey(&rsapkey);
497	if (rsapkeysize != req->pk_key.length) {
498	    ret = ASN1_EXTRA_DATA;
499	    goto out;
500	}
501    }
502
503    ALLOC(rep.certificate);
504    if (rep.certificate == NULL)
505	goto out;
506    krb5_data_zero(rep.certificate);
507    ALLOC(rep.hash);
508    if (rep.hash == NULL)
509	goto out;
510    krb5_data_zero(rep.hash);
511
512    ret = build_certificate(context, config, &req->pk_key,
513			    krb5_ticket_get_endtime(context, ticket),
514			    cprincipal, rep.certificate);
515    if (ret)
516	goto out;
517
518    ret = calculate_reply_hash(context, key, &rep);
519    if (ret)
520	goto out;
521
522    /*
523     * Encode reply, [ version | Kx509Response ]
524     */
525
526    {
527	krb5_data data;
528
529	ASN1_MALLOC_ENCODE(Kx509Response, data.data, data.length, &rep,
530			   &size, ret);
531	if (ret) {
532	    krb5_set_error_message(context, ret, "Failed to encode kx509 reply");
533	    goto out;
534	}
535	if (size != data.length)
536	    krb5_abortx(context, "ASN1 internal error");
537
538	ret = krb5_data_alloc(reply, data.length + sizeof(version_2_0));
539	if (ret) {
540	    free(data.data);
541	    goto out;
542	}
543	memcpy(reply->data, version_2_0, sizeof(version_2_0));
544	memcpy(((unsigned char *)reply->data) + sizeof(version_2_0),
545	       data.data, data.length);
546	free(data.data);
547    }
548
549    kdc_log(context, config, 0, "Successful Kx509 request for %s", cname);
550
551out:
552    if (ac)
553	krb5_auth_con_free(context, ac);
554    if (ret)
555	krb5_warn(context, ret, "Kx509 request from %s failed", from);
556    if (ticket)
557	krb5_free_ticket(context, ticket);
558    if (id)
559	krb5_kt_close(context, id);
560    if (sprincipal)
561	krb5_free_principal(context, sprincipal);
562    if (cprincipal)
563	krb5_free_principal(context, cprincipal);
564    if (key)
565	krb5_free_keyblock (context, key);
566    if (cname)
567	free(cname);
568    free_Kx509Response(&rep);
569
570    return 0;
571}
572
573#endif /* KX509 */
574