summaryrefslogtreecommitdiff
path: root/authenticate.c
blob: 3af7337ac74fadcfe73651cda87df2f687dc9eae (plain)
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
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
/*
 * Support rsync daemon authentication.
 *
 * Copyright (C) 1998-2000 Andrew Tridgell
 * Copyright (C) 2002-2009 Wayne Davison
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, visit the http://fsf.org website.
 */

#include "rsync.h"

extern char *password_file;

/***************************************************************************
encode a buffer using base64 - simple and slow algorithm. null terminates
the result.
  ***************************************************************************/
void base64_encode(const char *buf, int len, char *out, int pad)
{
	char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
	int bit_offset, byte_offset, idx, i;
	const uchar *d = (const uchar *)buf;
	int bytes = (len*8 + 5)/6;

	for (i = 0; i < bytes; i++) {
		byte_offset = (i*6)/8;
		bit_offset = (i*6)%8;
		if (bit_offset < 3) {
			idx = (d[byte_offset] >> (2-bit_offset)) & 0x3F;
		} else {
			idx = (d[byte_offset] << (bit_offset-2)) & 0x3F;
			if (byte_offset+1 < len) {
				idx |= (d[byte_offset+1] >> (8-(bit_offset-2)));
			}
		}
		out[i] = b64[idx];
	}

	while (pad && (i % 4))
		out[i++] = '=';

	out[i] = '\0';
}

/* Generate a challenge buffer and return it base64-encoded. */
static void gen_challenge(const char *addr, char *challenge)
{
	char input[32];
	char digest[MAX_DIGEST_LEN];
	struct timeval tv;
	int len;

	memset(input, 0, sizeof input);

	strlcpy(input, addr, 17);
	sys_gettimeofday(&tv);
	SIVAL(input, 16, tv.tv_sec);
	SIVAL(input, 20, tv.tv_usec);
	SIVAL(input, 24, getpid());

	sum_init(0);
	sum_update(input, sizeof input);
	len = sum_end(digest);

	base64_encode(digest, len, challenge, 0);
}


/* Return the secret for a user from the secret file, null terminated.
 * Maximum length is len (not counting the null). */
static int get_secret(int module, const char *user, char *secret, int len)
{
	const char *fname = lp_secrets_file(module);
	STRUCT_STAT st;
	int fd, ok = 1;
	const char *p;
	char ch, *s;

	if (!fname || !*fname)
		return 0;

	if ((fd = open(fname, O_RDONLY)) < 0)
		return 0;

	if (do_stat(fname, &st) == -1) {
		rsyserr(FLOG, errno, "stat(%s)", fname);
		ok = 0;
	} else if (lp_strict_modes(module)) {
		if ((st.st_mode & 06) != 0) {
			rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");
			ok = 0;
		} else if (MY_UID() == 0 && st.st_uid != 0) {
			rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");
			ok = 0;
		}
	}
	if (!ok) {
		rprintf(FLOG, "continuing without secrets file\n");
		close(fd);
		return 0;
	}

	if (*user == '#') {
		/* Reject attempt to match a comment. */
		close(fd);
		return 0;
	}

	/* Try to find a line that starts with the user name and a ':'. */
	p = user;
	while (1) {
		if (read(fd, &ch, 1) != 1) {
			close(fd);
			return 0;
		}
		if (ch == '\n')
			p = user;
		else if (p) {
			if (*p == ch)
				p++;
			else if (!*p && ch == ':')
				break;
			else
				p = NULL;
		}
	}

	/* Slurp the secret into the "secret" buffer. */
	s = secret;
	while (len > 0) {
		if (read(fd, s, 1) != 1 || *s == '\n')
			break;
		if (*s == '\r')
			continue;
		s++;
		len--;
	}
	*s = '\0';
	close(fd);

	return 1;
}

static const char *getpassf(const char *filename)
{
	STRUCT_STAT st;
	char buffer[512], *p;
	int fd, n, ok = 1;
	const char *envpw = getenv("RSYNC_PASSWORD");

	if (!filename)
		return NULL;

	if ((fd = open(filename,O_RDONLY)) < 0) {
		rsyserr(FWARNING, errno, "could not open password file \"%s\"",
			filename);
		if (envpw)
			rprintf(FINFO, "falling back to RSYNC_PASSWORD environment variable.\n");
		return NULL;
	}

	if (do_stat(filename, &st) == -1) {
		rsyserr(FWARNING, errno, "stat(%s)", filename);
		ok = 0;
	} else if ((st.st_mode & 06) != 0) {
		rprintf(FWARNING, "password file must not be other-accessible\n");
		ok = 0;
	} else if (MY_UID() == 0 && st.st_uid != 0) {
		rprintf(FWARNING, "password file must be owned by root when running as root\n");
		ok = 0;
	}
	if (!ok) {
		close(fd);
		rprintf(FWARNING, "continuing without password file\n");
		if (envpw)
			rprintf(FINFO, "falling back to RSYNC_PASSWORD environment variable.\n");
		return NULL;
	}

	n = read(fd, buffer, sizeof buffer - 1);
	close(fd);
	if (n > 0) {
		buffer[n] = '\0';
		if ((p = strtok(buffer, "\n\r")) != NULL)
			return strdup(p);
	}

	return NULL;
}

/* Generate an MD4 hash created from the combination of the password
 * and the challenge string and return it base64-encoded. */
static void generate_hash(const char *in, const char *challenge, char *out)
{
	char buf[MAX_DIGEST_LEN];
	int len;

	sum_init(0);
	sum_update(in, strlen(in));
	sum_update(challenge, strlen(challenge));
	len = sum_end(buf);

	base64_encode(buf, len, out, 0);
}

/* Possibly negotiate authentication with the client.  Use "leader" to
 * start off the auth if necessary.
 *
 * Return NULL if authentication failed.  Return "" if anonymous access.
 * Otherwise return username.
 */
char *auth_server(int f_in, int f_out, int module, const char *host,
		  const char *addr, const char *leader)
{
	char *users = lp_auth_users(module);
	char challenge[MAX_DIGEST_LEN*2];
	char line[BIGPATHBUFLEN];
	char secret[512];
	char pass2[MAX_DIGEST_LEN*2];
	char *tok, *pass;

	/* if no auth list then allow anyone in! */
	if (!users || !*users)
		return "";

	gen_challenge(addr, challenge);

	io_printf(f_out, "%s%s\n", leader, challenge);

	if (!read_line_old(f_in, line, sizeof line)
	 || (pass = strchr(line, ' ')) == NULL) {
		rprintf(FLOG, "auth failed on module %s from %s (%s): "
			"invalid challenge response\n",
			lp_name(module), host, addr);
		return NULL;
	}
	*pass++ = '\0';

	if (!(users = strdup(users)))
		out_of_memory("auth_server");

	for (tok = strtok(users, " ,\t"); tok; tok = strtok(NULL, " ,\t")) {
		if (wildmatch(tok, line))
			break;
	}
	free(users);

	if (!tok) {
		rprintf(FLOG, "auth failed on module %s from %s (%s): "
			"unauthorized user\n",
			lp_name(module), host, addr);
		return NULL;
	}

	memset(secret, 0, sizeof secret);
	if (!get_secret(module, line, secret, sizeof secret - 1)) {
		memset(secret, 0, sizeof secret);
		rprintf(FLOG, "auth failed on module %s from %s (%s): "
			"missing secret for user \"%s\"\n",
			lp_name(module), host, addr, line);
		return NULL;
	}

	generate_hash(secret, challenge, pass2);
	memset(secret, 0, sizeof secret);

	if (strcmp(pass, pass2) != 0) {
		rprintf(FLOG, "auth failed on module %s from %s (%s): "
			"password mismatch\n",
			lp_name(module), host, addr);
		return NULL;
	}

	return strdup(line);
}

void auth_client(int fd, const char *user, const char *challenge)
{
	const char *pass;
	char pass2[MAX_DIGEST_LEN*2];

	if (!user || !*user)
		user = "nobody";

	if (!(pass = getpassf(password_file))
	 && !(pass = getenv("RSYNC_PASSWORD"))) {
		/* XXX: cyeoh says that getpass is deprecated, because
		 * it may return a truncated password on some systems,
		 * and it is not in the LSB.
                 *
                 * Andrew Klein says that getpassphrase() is present
                 * on Solaris and reads up to 256 characters.
                 *
                 * OpenBSD has a readpassphrase() that might be more suitable.
                 */
		pass = getpass("Password: ");
	}

	if (!pass)
		pass = "";

	generate_hash(pass, challenge, pass2);
	io_printf(fd, "%s %s\n", user, pass2);
}