1/*
2   Unix SMB/CIFS implementation.
3
4   Functions to create reasonable random numbers for crypto use.
5
6   Copyright (C) Jeremy Allison 2001
7
8   This program is free software; you can redistribute it and/or modify
9   it under the terms of the GNU General Public License as published by
10   the Free Software Foundation; either version 2 of the License, or
11   (at your option) any later version.
12
13   This program is distributed in the hope that it will be useful,
14   but WITHOUT ANY WARRANTY; without even the implied warranty of
15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16   GNU General Public License for more details.
17
18   You should have received a copy of the GNU General Public License
19   along with this program; if not, write to the Free Software
20   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21*/
22
23#include "includes.h"
24
25static unsigned char smb_arc4_state[258];
26static uint32 counter;
27
28static BOOL done_reseed = False;
29static void (*reseed_callback)(int *newseed);
30
31/****************************************************************
32 Copy any user given reseed data.
33*****************************************************************/
34
35void set_rand_reseed_callback(void (*fn)(int *))
36{
37	reseed_callback = fn;
38	set_need_random_reseed();
39}
40
41void set_need_random_reseed(void)
42{
43	done_reseed = False;
44}
45
46static void get_rand_reseed_data(int *reseed_data)
47{
48	if (reseed_callback) {
49		reseed_callback(reseed_data);
50	} else {
51		*reseed_data = 0;
52	}
53}
54
55/****************************************************************
56 Get a 16 byte hash from the contents of a file.
57 Note that the hash is not initialised.
58*****************************************************************/
59
60static void do_filehash(const char *fname, unsigned char *the_hash)
61{
62	unsigned char buf[1011]; /* deliberate weird size */
63	unsigned char tmp_md4[16];
64	int fd, n;
65
66	fd = sys_open(fname,O_RDONLY,0);
67	if (fd == -1)
68		return;
69
70	while ((n = read(fd, (char *)buf, sizeof(buf))) > 0) {
71		mdfour(tmp_md4, buf, n);
72		for (n=0;n<16;n++)
73			the_hash[n] ^= tmp_md4[n];
74	}
75	close(fd);
76}
77
78/**************************************************************
79 Try and get a good random number seed. Try a number of
80 different factors. Firstly, try /dev/urandom - use if exists.
81
82 We use /dev/urandom as a read of /dev/random can block if
83 the entropy pool dries up. This leads clients to timeout
84 or be very slow on connect.
85
86 If we can't use /dev/urandom then seed the stream random generator
87 above...
88**************************************************************/
89
90static int do_reseed(BOOL use_fd, int fd)
91{
92	unsigned char seed_inbuf[40];
93	uint32 v1, v2; struct timeval tval; pid_t mypid;
94	struct passwd *pw;
95	int reseed_data = 0;
96
97	if (use_fd) {
98		if (fd != -1)
99			return fd;
100
101		fd = sys_open( "/dev/urandom", O_RDONLY,0);
102		if(fd >= 0)
103			return fd;
104	}
105
106	/* Add in some secret file contents */
107
108	do_filehash("/etc/shadow", &seed_inbuf[0]);
109	do_filehash(lp_smb_passwd_file(), &seed_inbuf[16]);
110
111	/*
112	 * Add in the root encrypted password.
113	 * On any system where security is taken
114	 * seriously this will be secret.
115	 */
116
117	pw = getpwnam_alloc(NULL, "root");
118	if (pw && pw->pw_passwd) {
119		size_t i;
120		unsigned char md4_tmp[16];
121		mdfour(md4_tmp, (unsigned char *)pw->pw_passwd, strlen(pw->pw_passwd));
122		for (i=0;i<16;i++)
123			seed_inbuf[8+i] ^= md4_tmp[i];
124		TALLOC_FREE(pw);
125	}
126
127	/*
128	 * Add the counter, time of day, and pid.
129	 */
130
131	GetTimeOfDay(&tval);
132	mypid = sys_getpid();
133	v1 = (counter++) + mypid + tval.tv_sec;
134	v2 = (counter++) * mypid + tval.tv_usec;
135
136	SIVAL(seed_inbuf, 32, v1 ^ IVAL(seed_inbuf, 32));
137	SIVAL(seed_inbuf, 36, v2 ^ IVAL(seed_inbuf, 36));
138
139	/*
140	 * Add any user-given reseed data.
141	 */
142
143	get_rand_reseed_data(&reseed_data);
144	if (reseed_data) {
145		size_t i;
146		for (i = 0; i < sizeof(seed_inbuf); i++)
147			seed_inbuf[i] ^= ((char *)(&reseed_data))[i % sizeof(reseed_data)];
148	}
149
150	smb_arc4_init(smb_arc4_state, seed_inbuf, sizeof(seed_inbuf));
151
152	return -1;
153}
154
155/*******************************************************************
156 Interface to the (hopefully) good crypto random number generator.
157********************************************************************/
158
159void generate_random_buffer( unsigned char *out, int len)
160{
161	static int urand_fd = -1;
162	unsigned char md4_buf[64];
163	unsigned char tmp_buf[16];
164	unsigned char *p;
165
166	if(!done_reseed) {
167		urand_fd = do_reseed(True, urand_fd);
168		done_reseed = True;
169	}
170
171	if (urand_fd != -1 && len > 0) {
172
173		if (read(urand_fd, out, len) == len)
174			return; /* len bytes of random data read from urandom. */
175
176		/* Read of urand error, drop back to non urand method. */
177		close(urand_fd);
178		urand_fd = -1;
179		do_reseed(False, -1);
180		done_reseed = True;
181	}
182
183	/*
184	 * Generate random numbers in chunks of 64 bytes,
185	 * then md4 them & copy to the output buffer.
186	 * This way the raw state of the stream is never externally
187	 * seen.
188	 */
189
190	p = out;
191	while(len > 0) {
192		int copy_len = len > 16 ? 16 : len;
193
194		smb_arc4_crypt(smb_arc4_state, md4_buf, sizeof(md4_buf));
195		mdfour(tmp_buf, md4_buf, sizeof(md4_buf));
196		memcpy(p, tmp_buf, copy_len);
197		p += copy_len;
198		len -= copy_len;
199	}
200}
201
202/*******************************************************************
203 Use the random number generator to generate a random string.
204********************************************************************/
205
206static char c_list[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+_-#.,";
207
208char *generate_random_str(size_t len)
209{
210	static unsigned char retstr[256];
211	size_t i;
212
213	memset(retstr, '\0', sizeof(retstr));
214
215	if (len > sizeof(retstr)-1)
216		len = sizeof(retstr) -1;
217	generate_random_buffer( retstr, len);
218	for (i = 0; i < len; i++)
219		retstr[i] = c_list[ retstr[i] % (sizeof(c_list)-1) ];
220
221	retstr[i] = '\0';
222
223	return (char *)retstr;
224}
225