summaryrefslogtreecommitdiff
path: root/loginutils/passwd.c
blob: bcb7f2b26114b87940076b957f9278abd47f2ad7 (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
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
/* vi: set sw=4 ts=4: */
/*
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

#include "busybox.h"
#include <syslog.h>


static void nuke_str(char *str)
{
	if (str) memset(str, 0, strlen(str));
}


static int i64c(int i)
{
	i &= 0x3f;
	if (i == 0)
		return '.';
	if (i == 1)
		return '/';
	if (i < 12)
		return ('0' - 2 + i);
	if (i < 38)
		return ('A' - 12 + i);
	return ('a' - 38 + i);
}


static void crypt_make_salt(char *p, int cnt)
{
	unsigned x = x; /* it's pointless to initialize it anyway :) */

	x += getpid() + time(NULL) + clock();
	do {
		/* x = (x*1664525 + 1013904223) % 2^32 generator is lame
		 * (low-order bit is not "random", etc...),
		 * but for our purposes it is good enough */
		x = x*1664525 + 1013904223;
		/* BTW, Park and Miller's "minimal standard generator" is
		 * x = x*16807 % ((2^31)-1)
		 * It has no problem with visibly alternating lowest bit
		 * but is also weak in cryptographic sense + needs div,
		 * which needs more code (and slower) on many CPUs */
		*p++ = i64c(x >> 16);
		*p++ = i64c(x >> 22);
	} while (--cnt);
	*p = '\0';
}


static char* new_password(const struct passwd *pw, uid_t myuid, int algo)
{
	char salt[sizeof("$N$XXXXXXXX")]; /* "$N$XXXXXXXX" or "XX" */
	char *orig = "";
	char *newp = NULL;
	char *cipher = NULL;
	char *cp = NULL;
	char *ret = NULL; /* failure so far */

	if (myuid && pw->pw_passwd[0]) {
		orig = bb_askpass(0, "Old password:"); /* returns ptr to static */
		if (!orig)
			goto err_ret;
		cipher = pw_encrypt(orig, pw->pw_passwd); /* returns ptr to static */
		if (strcmp(cipher, pw->pw_passwd) != 0) {
			syslog(LOG_WARNING, "incorrect password for '%s'",
				pw->pw_name);
			bb_do_delay(FAIL_DELAY);
			puts("Incorrect password");
			goto err_ret;
		}
	}
	orig = xstrdup(orig); /* or else bb_askpass() will destroy it */
	newp = bb_askpass(0, "New password:"); /* returns ptr to static */
	if (!newp)
		goto err_ret;
	newp = xstrdup(newp); /* we are going to bb_askpass() again, so save it */
	if (obscure(orig, newp, pw) && myuid)
		goto err_ret; /* non-root is not allowed to have weak passwd */

	cp = bb_askpass(0, "Retype password:");
	if (!cp)
		goto err_ret;
	if (strcmp(cp, newp)) {
		puts("Passwords don't match");
		goto err_ret;
	}

	/*memset(salt, 0, sizeof(salt)); - why?*/
	crypt_make_salt(salt, 1); /* des */
	if (algo) { /* MD5 */
		strcpy(salt, "$1$");
		crypt_make_salt(salt + 3, 4);
	}
	ret = xstrdup(pw_encrypt(newp, salt)); /* returns ptr to static */
	/* whee, success! */

 err_ret:
	nuke_str(orig);
	if (ENABLE_FEATURE_CLEAN_UP) free(orig);
	nuke_str(newp);
	if (ENABLE_FEATURE_CLEAN_UP) free(newp);
	nuke_str(cipher);
	nuke_str(cp);
	return ret;
}


#if 0
static int get_algo(char *a)
{
	/* standard: MD5 */
	int x = 1;
	if (strcasecmp(a, "des") == 0)
		x = 0;
	return x;
}
#endif


static int update_passwd(const char *filename, const char *username,
			const char *new_pw)
{
	struct stat sb;
	struct flock lock;
	FILE *old_fp;
	FILE *new_fp;
	char *new_name;
	char *last_char;
	unsigned user_len;
	int old_fd;
	int new_fd;
	int i;
	int ret = 1; /* failure */

	logmode = LOGMODE_STDIO;
	/* New passwd file, "/etc/passwd+" for now */
	new_name = xasprintf("%s+", filename);
	last_char = &new_name[strlen(new_name)-1];
	username = xasprintf("%s:", username);
	user_len = strlen(username);

	old_fp = fopen(filename, "r+");
	if (!old_fp)
		goto free_mem;
	old_fd = fileno(old_fp);

	/* Try to create "/etc/passwd+". Wait if it exists. */
	i = 30;
	do {
		// FIXME: on last iteration try w/o O_EXCL but with O_TRUNC?
		new_fd = open(new_name, O_WRONLY|O_CREAT|O_EXCL,0600);
		if (new_fd >= 0) goto created;
		if (errno != EEXIST) break;
		usleep(100000); /* 0.1 sec */
	} while (--i);
	bb_perror_msg("cannot create '%s'", new_name);
	goto close_old_fp;
 created:
	if (!fstat(old_fd, &sb)) {
		fchmod(new_fd, sb.st_mode & 0777); /* ignore errors */
		fchown(new_fd, sb.st_uid, sb.st_gid);
	}
	new_fp = fdopen(new_fd, "w");
	if (!new_fp) {
		close(new_fd);
		goto unlink_new;
	}

	/* Backup file is "/etc/passwd-" */
	last_char[0] = '-';
	/* Delete old one, create new as a hardlink to current */
	i = (unlink(new_name) && errno != ENOENT);
	if (i || link(filename, new_name))
		bb_perror_msg("warning: cannot create backup copy '%s'", new_name);
	last_char[0] = '+';

	/* Lock the password file before updating */
	lock.l_type = F_WRLCK;
	lock.l_whence = SEEK_SET;
	lock.l_start = 0;
	lock.l_len = 0;
	if (fcntl(old_fd, F_SETLK, &lock) < 0)
		bb_perror_msg("warning: cannot lock '%s'", filename);
	lock.l_type = F_UNLCK;

	/* Read current password file, write updated one */
	while (1) {
		char *line = xmalloc_fgets(old_fp);
		if (!line) break; /* EOF/error */
		if (strncmp(username, line, user_len) == 0) {
			/* we have a match with "username:"... */
			const char *cp = line + user_len;
			/* now cp -> old passwd, skip it: */
			cp = strchr(cp, ':');
			if (!cp) cp = "";
			/* now cp -> ':' after old passwd or -> "" */
			fprintf(new_fp, "%s%s%s", username, new_pw, cp);
			/* Erase password in memory */
		} else
			fputs(line, new_fp);
		free(line);
	}
	fcntl(old_fd, F_SETLK, &lock);

	/* We do want all of them to execute, thus | instead of || */
	if ((ferror(old_fp) | fflush(new_fp) | fsync(new_fd) | fclose(new_fp))
	 || rename(new_name, filename)
	) {
		/* At least one of those failed */
		goto unlink_new;
	}
	ret = 0; /* whee, success! */

 unlink_new:
	if (ret) unlink(new_name);

 close_old_fp:
	fclose(old_fp);

 free_mem:
	if (ENABLE_FEATURE_CLEAN_UP) free(new_name);
	if (ENABLE_FEATURE_CLEAN_UP) free((char*)username);
	logmode = LOGMODE_BOTH;
	return ret;
}


int passwd_main(int argc, char **argv)
{
	enum {
		OPT_algo = 0x1, /* -a - password algorithm */
		OPT_lock = 0x2, /* -l - lock account */
		OPT_unlock = 0x4, /* -u - unlock account */
		OPT_delete = 0x8, /* -d - delete password */
		OPT_lud = 0xe,
		STATE_ALGO_md5 = 0x10,
		/*STATE_ALGO_des = 0x20, not needed yet */
	};
	unsigned opt;
	char *opt_a = "";
	const char *filename;
	char *myname;
	char *name;
	char *newp;
	struct passwd *pw;
	uid_t myuid;
	struct rlimit rlimit_fsize;
	char c;

	logmode = LOGMODE_BOTH;
	openlog(applet_name, LOG_NOWAIT, LOG_AUTH);
	opt = getopt32(argc, argv, "a:lud", &opt_a);
	argc -= optind;
	argv += optind;

	if (strcasecmp(opt_a, "des") != 0) /* -a */
		opt |= STATE_ALGO_md5;
	//else
	//	opt |= STATE_ALGO_des;
	myuid = getuid();
	if ((opt & OPT_lud) && (!argc || myuid))
		bb_show_usage();

	myname = xstrdup(bb_getpwuid(NULL, myuid, -1));
	name = argc ? argv[0] : myname;

	pw = getpwnam(name);
	if (!pw) bb_error_msg_and_die("unknown user %s", name);
	if (myuid && pw->pw_uid != myuid) {
		/* LOGMODE_BOTH */
		bb_error_msg_and_die("%s can't change password for %s", myname, name);
	}

	filename = bb_path_passwd_file;
	if (ENABLE_FEATURE_SHADOWPASSWDS) {
		struct spwd *sp = getspnam(name);
		if (!sp) {
			/* LOGMODE_BOTH */
			bb_error_msg("no record of %s in %s, using %s",
					name, bb_path_shadow_file,
					bb_path_passwd_file);
		} else {
			filename = bb_path_shadow_file;
			pw->pw_passwd = sp->sp_pwdp;
		}
	}

	/* Decide what the new password will be */
	newp = NULL;
	c = pw->pw_passwd[0] - '!';
	if (!(opt & OPT_lud)) {
		if (myuid && !c) { /* passwd starts with '!' */
			/* LOGMODE_BOTH */
			bb_error_msg_and_die("cannot change "
					"locked password for %s", name);
		}
		printf("Changing password for %s\n", name);
		newp = new_password(pw, myuid, opt & STATE_ALGO_md5);
		if (!newp) {
			logmode = LOGMODE_STDIO;
			bb_error_msg_and_die("password for %s is unchanged", name);
		}
	} else if (opt & OPT_lock) {
		if (!c) goto skip; /* passwd starts with '!' */
		newp = xasprintf("!%s", pw->pw_passwd);
	} else if (opt & OPT_unlock) {
		if (c) goto skip; /* not '!' */
		newp = xstrdup(&pw->pw_passwd[1]);
	} else if (opt & OPT_delete) {
		newp = xstrdup("");
	}

	rlimit_fsize.rlim_cur = rlimit_fsize.rlim_max = 512L * 30000;
	setrlimit(RLIMIT_FSIZE, &rlimit_fsize);
	signal(SIGHUP, SIG_IGN);
	signal(SIGINT, SIG_IGN);
	signal(SIGQUIT, SIG_IGN);
	umask(077);
	xsetuid(0);
	if (update_passwd(filename, name, newp) != 0) {
		/* LOGMODE_BOTH */
		bb_error_msg_and_die("cannot update password file %s",
				filename);
	}
	/* LOGMODE_BOTH */
	bb_info_msg("Password for %s changed by %s", name, myname);

	if (ENABLE_FEATURE_CLEAN_UP) free(newp);
skip:
	if (!newp) {
		bb_error_msg_and_die("password for %s is already %slocked",
			name, (opt & OPT_unlock) ? "un" : "");
	}
	if (ENABLE_FEATURE_CLEAN_UP) free(myname);
	return 0;
}