1/*
2 * Copyright (c) 1995 - 2005 Kungliga Tekniska Högskolan
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 "kx.h"
35
36RCSID("$Id$");
37
38#ifdef KRB5
39
40struct krb5_kx_context {
41    krb5_context context;
42    krb5_keyblock *keyblock;
43    krb5_crypto crypto;
44    krb5_principal client;
45    krb5_log_facility *log;
46
47};
48
49typedef struct krb5_kx_context krb5_kx_context;
50
51#define K5DATA(kc) ((krb5_kx_context*)kc->data)
52#define CONTEXT(kc) (K5DATA(kc)->context)
53
54/*
55 *
56 */
57
58static void
59ksyslog(krb5_context context, krb5_error_code ret, const char *fmt, ...)
60	__attribute__((__format__(__printf__, 3, 0)));
61
62static void
63ksyslog(krb5_context context, krb5_error_code ret, const char *fmt, ...)
64{
65    const char *msg;
66    char *str = NULL;
67    va_list va;
68
69    msg = krb5_get_error_message(context, ret);
70
71    va_start(va, fmt);
72    vasprintf(&str, fmt, va);
73    va_end(va);
74
75    syslog(LOG_ERR, "%s: %s", str, msg);
76
77    krb5_free_error_message(context, msg);
78    free(str);
79}
80
81/*
82 * Destroy the krb5 context in `c'.
83 */
84
85static void
86krb5_destroy (kx_context *kc)
87{
88    if (K5DATA(kc)->keyblock)
89	krb5_free_keyblock (CONTEXT(kc), K5DATA(kc)->keyblock);
90    if (K5DATA(kc)->crypto)
91	krb5_crypto_destroy (CONTEXT(kc), K5DATA(kc)->crypto);
92    if (K5DATA(kc)->client)
93	krb5_free_principal (CONTEXT(kc), K5DATA(kc)->client);
94    if (CONTEXT(kc))
95	krb5_free_context (CONTEXT(kc));
96    memset (kc->data, 0, sizeof(krb5_kx_context));
97    free (kc->data);
98}
99
100/*
101 * Read the authentication information from `s' and return 0 if
102 * succesful, else -1.
103 */
104
105static int
106krb5_authenticate (kx_context *kc, int s)
107{
108    krb5_auth_context auth_context = NULL;
109    krb5_error_code ret;
110    krb5_principal server;
111    const char *host = kc->host;
112
113    ret = krb5_sname_to_principal (CONTEXT(kc),
114				   host, "host", KRB5_NT_SRV_HST, &server);
115    if (ret) {
116	krb5_warn (CONTEXT(kc), ret, "krb5_sname_to_principal: %s", host);
117	return 1;
118    }
119
120    ret = krb5_sendauth (CONTEXT(kc),
121			 &auth_context,
122			 &s,
123			 KX_VERSION,
124			 NULL,
125			 server,
126			 AP_OPTS_MUTUAL_REQUIRED | AP_OPTS_USE_SUBKEY,
127			 NULL,
128			 NULL,
129			 NULL,
130			 NULL,
131			 NULL,
132			 NULL);
133    if (ret) {
134	if(ret != KRB5_SENDAUTH_BADRESPONSE)
135	    krb5_warn (CONTEXT(kc), ret, "krb5_sendauth: %s", host);
136	return 1;
137    }
138
139    ret = krb5_auth_con_getkey (CONTEXT(kc), auth_context,
140				&K5DATA(kc)->keyblock);
141    if (ret) {
142	krb5_warn (CONTEXT(kc), ret, "krb5_auth_con_getkey: %s", host);
143	krb5_auth_con_free (CONTEXT(kc), auth_context);
144	return 1;
145    }
146
147    ret = krb5_crypto_init (CONTEXT(kc), K5DATA(kc)->keyblock,
148			    0, &K5DATA(kc)->crypto);
149    if (ret) {
150	krb5_warn (CONTEXT(kc), ret, "krb5_crypto_init");
151	krb5_auth_con_free (CONTEXT(kc), auth_context);
152	return 1;
153    }
154    return 0;
155}
156
157/*
158 * Read an encapsulated krb5 packet from `fd' into `buf' (of size
159 * `len').  Return the number of bytes read or 0 on EOF or -1 on
160 * error.
161 */
162
163static ssize_t
164krb5_read (kx_context *kc,
165	   int fd, void *buf, size_t len)
166{
167    size_t data_len, outer_len;
168    krb5_error_code ret;
169    unsigned char tmp[4];
170    krb5_data data;
171    int l;
172
173    l = krb5_net_read (CONTEXT(kc), &fd, tmp, 4);
174    if (l == 0)
175	return l;
176    if (l != 4)
177	return -1;
178    data_len  = (tmp[0] << 24) | (tmp[1] << 16) | (tmp[2] << 8) | tmp[3];
179    outer_len = krb5_get_wrapped_length (CONTEXT(kc),
180					 K5DATA(kc)->crypto, data_len);
181    if (outer_len > len)
182	return -1;
183    if (krb5_net_read (CONTEXT(kc), &fd, buf, outer_len) != outer_len)
184	return -1;
185
186    ret = krb5_decrypt (CONTEXT(kc), K5DATA(kc)->crypto,
187			KRB5_KU_OTHER_ENCRYPTED,
188			buf, outer_len, &data);
189    if (ret) {
190	krb5_warn (CONTEXT(kc), ret, "krb5_decrypt");
191	return -1;
192    }
193    if (data_len > data.length) {
194	krb5_data_free (&data);
195	return -1;
196    }
197    memmove (buf, data.data, data_len);
198    krb5_data_free (&data);
199    return data_len;
200}
201
202/*
203 * Write an encapsulated krb5 packet on `fd' with the data in `buf,
204 * len'.  Return len or -1 on error.
205 */
206
207static ssize_t
208krb5_write(kx_context *kc,
209	   int fd, const void *buf, size_t len)
210{
211    krb5_data data;
212    krb5_error_code ret;
213    unsigned char tmp[4];
214    size_t outlen;
215
216    ret = krb5_encrypt (CONTEXT(kc), K5DATA(kc)->crypto,
217			KRB5_KU_OTHER_ENCRYPTED,
218			buf, len, &data);
219    if (ret){
220	krb5_warn (CONTEXT(kc), ret, "krb5_write");
221	return -1;
222    }
223
224    outlen = data.length;
225    tmp[0] = (len >> 24) & 0xFF;
226    tmp[1] = (len >> 16) & 0xFF;
227    tmp[2] = (len >>  8) & 0xFF;
228    tmp[3] = (len >>  0) & 0xFF;
229
230    if (krb5_net_write (CONTEXT(kc), &fd, tmp, 4) != 4 ||
231	krb5_net_write (CONTEXT(kc), &fd, data.data, outlen) != outlen) {
232	krb5_data_free (&data);
233	return -1;
234    }
235    krb5_data_free (&data);
236    return len;
237}
238
239/*
240 * Copy from the unix socket `from_fd' encrypting to `to_fd'.
241 * Return 0, -1 or len.
242 */
243
244static int
245copy_out (kx_context *kc, int from_fd, int to_fd)
246{
247    char buf[32768];
248    ssize_t len;
249
250    len = read (from_fd, buf, sizeof(buf));
251    if (len == 0)
252	return 0;
253    if (len < 0) {
254	krb5_warn (CONTEXT(kc), errno, "read");
255	return len;
256    }
257    return krb5_write (kc, to_fd, buf, len);
258}
259
260/*
261 * Copy from the socket `from_fd' decrypting to `to_fd'.
262 * Return 0, -1 or len.
263 */
264
265static int
266copy_in (kx_context *kc, int from_fd, int to_fd)
267{
268    char buf[33000];		/* XXX */
269
270    ssize_t len;
271
272    len = krb5_read (kc, from_fd, buf, sizeof(buf));
273    if (len == 0)
274	return 0;
275    if (len < 0) {
276	krb5_warn (CONTEXT(kc), errno, "krb5_read");
277	return len;
278    }
279
280    return krb5_net_write (CONTEXT(kc), &to_fd, buf, len);
281}
282
283/*
284 * Copy data between `fd1' and `fd2', encrypting in one direction and
285 * decrypting in the other.
286 */
287
288static int
289krb5_copy_encrypted (kx_context *kc, int fd1, int fd2)
290{
291    for (;;) {
292	fd_set fdset;
293	int ret;
294
295	if (fd1 >= FD_SETSIZE || fd2 >= FD_SETSIZE) {
296	    krb5_warnx (CONTEXT(kc), "fd too large");
297	    return 1;
298	}
299
300	FD_ZERO(&fdset);
301	FD_SET(fd1, &fdset);
302	FD_SET(fd2, &fdset);
303
304	ret = select (max(fd1, fd2)+1, &fdset, NULL, NULL, NULL);
305	if (ret < 0 && errno != EINTR) {
306	    krb5_warn (CONTEXT(kc), errno, "select");
307	    return 1;
308	}
309	if (FD_ISSET(fd1, &fdset)) {
310	    ret = copy_out (kc, fd1, fd2);
311	    if (ret <= 0)
312		return ret;
313	}
314	if (FD_ISSET(fd2, &fdset)) {
315	    ret = copy_in (kc, fd2, fd1);
316	    if (ret <= 0)
317		return ret;
318	}
319    }
320}
321
322/*
323 * Return 0 if the user authenticated on `kc' is allowed to login as
324 * `user'.
325 */
326
327static int
328krb5_userok (kx_context *kc, char *user)
329{
330    krb5_error_code ret;
331    char *tmp;
332
333    ret = krb5_unparse_name (CONTEXT(kc), K5DATA(kc)->client, &tmp);
334    if (ret)
335	krb5_err (CONTEXT(kc), 1, ret, "krb5_unparse_name");
336    kc->user = tmp;
337
338    return !krb5_kuserok (CONTEXT(kc), K5DATA(kc)->client, user);
339}
340
341/*
342 * Create an instance of an krb5 context.
343 */
344
345void
346krb5_make_context (kx_context *kc)
347{
348    krb5_kx_context *c;
349    krb5_error_code ret;
350
351    kc->authenticate	= krb5_authenticate;
352    kc->userok		= krb5_userok;
353    kc->read		= krb5_read;
354    kc->write		= krb5_write;
355    kc->copy_encrypted	= krb5_copy_encrypted;
356    kc->destroy		= krb5_destroy;
357    kc->user		= NULL;
358    kc->data		= malloc(sizeof(krb5_kx_context));
359
360    if (kc->data == NULL) {
361	syslog (LOG_ERR, "failed to malloc %lu bytes",
362		(unsigned long)sizeof(krb5_kx_context));
363	exit(1);
364    }
365    memset (kc->data, 0, sizeof(krb5_kx_context));
366    c = (krb5_kx_context *)kc->data;
367    ret = krb5_init_context (&c->context);
368    if (ret) {
369	syslog (LOG_ERR, "failed initialise krb5 context");
370	exit(1);
371    }
372}
373
374/*
375 * Receive authentication information on `sock' (first four bytes
376 * in `buf').
377 */
378
379int
380recv_v5_auth (kx_context *kc, int sock, u_char *buf)
381{
382    uint32_t len;
383    krb5_error_code ret;
384    krb5_principal server;
385    krb5_auth_context auth_context = NULL;
386    krb5_ticket *ticket;
387
388    if (memcmp (buf, "\x00\x00\x00\x13", 4) != 0)
389	return 1;
390    len = (buf[0] << 24) | (buf[1] << 16) | (buf[2] << 8) | (buf[3]);
391    if (net_read(sock, buf, len) != len) {
392	syslog (LOG_ERR, "read: %m");
393	exit (1);
394    }
395    if (len != sizeof(KRB5_SENDAUTH_VERSION)
396	|| memcmp (buf, KRB5_SENDAUTH_VERSION, len) != 0) {
397	syslog (LOG_ERR, "bad sendauth version: %.8s", buf);
398	exit (1);
399    }
400
401    krb5_make_context (kc);
402    krb5_openlog(CONTEXT(kc), "kxd", &K5DATA(kc)->log);
403    krb5_set_warn_dest(CONTEXT(kc), K5DATA(kc)->log);
404
405    ret = krb5_sock_to_principal (CONTEXT(kc), sock, "host",
406				  KRB5_NT_SRV_HST, &server);
407    if (ret) {
408	ksyslog (CONTEXT(kc), ret, "krb5_sock_to_principal");
409	exit (1);
410    }
411
412    ret = krb5_recvauth (CONTEXT(kc),
413			 &auth_context,
414			 &sock,
415			 KX_VERSION,
416			 server,
417			 KRB5_RECVAUTH_IGNORE_VERSION,
418			 NULL,
419			 &ticket);
420    krb5_free_principal (CONTEXT(kc), server);
421    if (ret) {
422	ksyslog (CONTEXT(kc), ret, "krb5_recvauth");
423	exit (1);
424    }
425
426    ret = krb5_auth_con_getkey (CONTEXT(kc), auth_context, &K5DATA(kc)->keyblock);
427    if (ret) {
428	ksyslog (CONTEXT(kc), ret, "krb5_auth_con_getkey");
429	exit (1);
430    }
431
432    ret = krb5_crypto_init (CONTEXT(kc), K5DATA(kc)->keyblock, 0, &K5DATA(kc)->crypto);
433    if (ret) {
434	ksyslog (CONTEXT(kc), ret, "krb5_crypto_init");
435	exit (1);
436    }
437
438    K5DATA(kc)->client = ticket->client;
439    ticket->client = NULL;
440    krb5_free_ticket (CONTEXT(kc), ticket);
441
442    krb5_auth_con_free(CONTEXT(kc), auth_context);
443
444    return 0;
445}
446
447#endif /* KRB5 */
448