1/*
2 * Support rsync daemon authentication.
3 *
4 * Copyright (C) 1998-2000 Andrew Tridgell
5 * Copyright (C) 2002, 2004, 2005, 2006 Wayne Davison
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License along
18 * with this program; if not, write to the Free Software Foundation, Inc.,
19 * 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.
20 */
21
22#include "rsync.h"
23
24extern char *password_file;
25
26/***************************************************************************
27encode a buffer using base64 - simple and slow algorithm. null terminates
28the result.
29  ***************************************************************************/
30void base64_encode(char *buf, int len, char *out, int pad)
31{
32	char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
33	int bit_offset, byte_offset, idx, i;
34	unsigned char *d = (unsigned char *)buf;
35	int bytes = (len*8 + 5)/6;
36
37	for (i = 0; i < bytes; i++) {
38		byte_offset = (i*6)/8;
39		bit_offset = (i*6)%8;
40		if (bit_offset < 3) {
41			idx = (d[byte_offset] >> (2-bit_offset)) & 0x3F;
42		} else {
43			idx = (d[byte_offset] << (bit_offset-2)) & 0x3F;
44			if (byte_offset+1 < len) {
45				idx |= (d[byte_offset+1] >> (8-(bit_offset-2)));
46			}
47		}
48		out[i] = b64[idx];
49	}
50
51	while (pad && (i % 4))
52		out[i++] = '=';
53
54	out[i] = '\0';
55}
56
57/* Generate a challenge buffer and return it base64-encoded. */
58static void gen_challenge(char *addr, char *challenge)
59{
60	char input[32];
61	char md4_out[MD4_SUM_LENGTH];
62	struct timeval tv;
63
64	memset(input, 0, sizeof input);
65
66	strlcpy((char *)input, addr, 17);
67	sys_gettimeofday(&tv);
68	SIVAL(input, 16, tv.tv_sec);
69	SIVAL(input, 20, tv.tv_usec);
70	SIVAL(input, 24, getpid());
71
72	sum_init(0);
73	sum_update(input, sizeof input);
74	sum_end(md4_out);
75
76	base64_encode(md4_out, MD4_SUM_LENGTH, challenge, 0);
77}
78
79
80/* Return the secret for a user from the secret file, null terminated.
81 * Maximum length is len (not counting the null). */
82static int get_secret(int module, char *user, char *secret, int len)
83{
84	char *fname = lp_secrets_file(module);
85	STRUCT_STAT st;
86	int fd, ok = 1;
87	char ch, *p;
88
89	if (!fname || !*fname)
90		return 0;
91
92	if ((fd = open(fname, O_RDONLY)) < 0)
93		return 0;
94
95	if (do_stat(fname, &st) == -1) {
96		rsyserr(FLOG, errno, "stat(%s)", fname);
97		ok = 0;
98	} else if (lp_strict_modes(module)) {
99		if ((st.st_mode & 06) != 0) {
100			rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");
101			ok = 0;
102		} else if (MY_UID() == 0 && st.st_uid != 0) {
103			rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");
104			ok = 0;
105		}
106	}
107	if (!ok) {
108		rprintf(FLOG, "continuing without secrets file\n");
109		close(fd);
110		return 0;
111	}
112
113	if (*user == '#') {
114		/* Reject attempt to match a comment. */
115		close(fd);
116		return 0;
117	}
118
119	/* Try to find a line that starts with the user name and a ':'. */
120	p = user;
121	while (1) {
122		if (read(fd, &ch, 1) != 1) {
123			close(fd);
124			return 0;
125		}
126		if (ch == '\n')
127			p = user;
128		else if (p) {
129			if (*p == ch)
130				p++;
131			else if (!*p && ch == ':')
132				break;
133			else
134				p = NULL;
135		}
136	}
137
138	/* Slurp the secret into the "secret" buffer. */
139	p = secret;
140	while (len > 0) {
141		if (read(fd, p, 1) != 1 || *p == '\n')
142			break;
143		if (*p == '\r')
144			continue;
145		p++;
146		len--;
147	}
148	*p = '\0';
149	close(fd);
150
151	return 1;
152}
153
154static char *getpassf(char *filename)
155{
156	STRUCT_STAT st;
157	char buffer[512], *p;
158	int fd, n, ok = 1;
159	char *envpw = getenv("RSYNC_PASSWORD");
160
161	if (!filename)
162		return NULL;
163
164	if ((fd = open(filename,O_RDONLY)) < 0) {
165		rsyserr(FERROR, errno, "could not open password file \"%s\"",
166			filename);
167		if (envpw)
168			rprintf(FERROR, "falling back to RSYNC_PASSWORD environment variable.\n");
169		return NULL;
170	}
171
172	if (do_stat(filename, &st) == -1) {
173		rsyserr(FERROR, errno, "stat(%s)", filename);
174		ok = 0;
175	} else if ((st.st_mode & 06) != 0) {
176		rprintf(FERROR,"password file must not be other-accessible\n");
177		ok = 0;
178	} else if (MY_UID() == 0 && st.st_uid != 0) {
179		rprintf(FERROR,"password file must be owned by root when running as root\n");
180		ok = 0;
181	}
182	if (!ok) {
183		rprintf(FERROR,"continuing without password file\n");
184		if (envpw)
185			rprintf(FERROR, "using RSYNC_PASSWORD environment variable.\n");
186		close(fd);
187		return NULL;
188	}
189
190	if (envpw)
191		rprintf(FERROR, "RSYNC_PASSWORD environment variable ignored\n");
192
193	n = read(fd, buffer, sizeof buffer - 1);
194	close(fd);
195	if (n > 0) {
196		buffer[n] = '\0';
197		if ((p = strtok(buffer, "\n\r")) != NULL)
198			return strdup(p);
199	}
200
201	return NULL;
202}
203
204/* Generate an MD4 hash created from the combination of the password
205 * and the challenge string and return it base64-encoded. */
206static void generate_hash(char *in, char *challenge, char *out)
207{
208	char buf[MD4_SUM_LENGTH];
209
210	sum_init(0);
211	sum_update(in, strlen(in));
212	sum_update(challenge, strlen(challenge));
213	sum_end(buf);
214
215	base64_encode(buf, MD4_SUM_LENGTH, out, 0);
216}
217
218/* Possibly negotiate authentication with the client.  Use "leader" to
219 * start off the auth if necessary.
220 *
221 * Return NULL if authentication failed.  Return "" if anonymous access.
222 * Otherwise return username.
223 */
224char *auth_server(int f_in, int f_out, int module, char *host, char *addr,
225		  char *leader)
226{
227	char *users = lp_auth_users(module);
228	char challenge[MD4_SUM_LENGTH*2];
229	char line[BIGPATHBUFLEN];
230	char secret[512];
231	char pass2[MD4_SUM_LENGTH*2];
232	char *tok, *pass;
233
234	/* if no auth list then allow anyone in! */
235	if (!users || !*users)
236		return "";
237
238	gen_challenge(addr, challenge);
239
240	io_printf(f_out, "%s%s\n", leader, challenge);
241
242	if (!read_line(f_in, line, sizeof line - 1)
243	 || (pass = strchr(line, ' ')) == NULL) {
244		rprintf(FLOG, "auth failed on module %s from %s (%s): "
245			"invalid challenge response\n",
246			lp_name(module), host, addr);
247		return NULL;
248	}
249	*pass++ = '\0';
250
251	if (!(users = strdup(users)))
252		out_of_memory("auth_server");
253
254	for (tok = strtok(users, " ,\t"); tok; tok = strtok(NULL, " ,\t")) {
255		if (wildmatch(tok, line))
256			break;
257	}
258	free(users);
259
260	if (!tok) {
261		rprintf(FLOG, "auth failed on module %s from %s (%s): "
262			"unauthorized user\n",
263			lp_name(module), host, addr);
264		return NULL;
265	}
266
267	memset(secret, 0, sizeof secret);
268	if (!get_secret(module, line, secret, sizeof secret - 1)) {
269		memset(secret, 0, sizeof secret);
270		rprintf(FLOG, "auth failed on module %s from %s (%s): "
271			"missing secret for user \"%s\"\n",
272			lp_name(module), host, addr, line);
273		return NULL;
274	}
275
276	generate_hash(secret, challenge, pass2);
277	memset(secret, 0, sizeof secret);
278
279	if (strcmp(pass, pass2) != 0) {
280		rprintf(FLOG, "auth failed on module %s from %s (%s): "
281			"password mismatch\n",
282			lp_name(module), host, addr);
283		return NULL;
284	}
285
286	return strdup(line);
287}
288
289
290void auth_client(int fd, char *user, char *challenge)
291{
292	char *pass;
293	char pass2[MD4_SUM_LENGTH*2];
294
295	if (!user || !*user)
296		user = "nobody";
297
298	if (!(pass = getpassf(password_file))
299	 && !(pass = getenv("RSYNC_PASSWORD"))) {
300		/* XXX: cyeoh says that getpass is deprecated, because
301		 * it may return a truncated password on some systems,
302		 * and it is not in the LSB.
303                 *
304                 * Andrew Klein says that getpassphrase() is present
305                 * on Solaris and reads up to 256 characters.
306                 *
307                 * OpenBSD has a readpassphrase() that might be more suitable.
308                 */
309		pass = getpass("Password: ");
310	}
311
312	if (!pass)
313		pass = "";
314
315	generate_hash(pass, challenge, pass2);
316	io_printf(fd, "%s %s\n", user, pass2);
317}
318