busybox/libbb/update_passwd.c

/* vi: set sw=4 ts=4: */
/*
 * update_passwd
 *
 * update_passwd is a common function for passwd and chpasswd applets;
 * it is responsible for updating password file (i.e. /etc/passwd or
 * /etc/shadow) for a given user and password.
 *
 * Moved from loginutils/passwd.c by Alexander Shishkin <virtuoso@slind.org>
 *
 * Modified to be able to add or delete users, groups and users to/from groups
 * by Tito Ragusa <farmatito@tiscali.it>
 *
 * Licensed under GPLv2, see file LICENSE in this tarball for details.
 */
#include "libbb.h"

#if ENABLE_SELINUX
static void check_selinux_update_passwd(const char *username)
{
	security_context_t context;
	char *seuser;

	if (getuid() != (uid_t)0 || is_selinux_enabled() == 0)
		return;		/* No need to check */

	if (getprevcon_raw(&context) < 0)
		bb_perror_msg_and_die("getprevcon failed");
	seuser = strtok(context, ":");
	if (!seuser)
		bb_error_msg_and_die("invalid context '%s'", context);
	if (strcmp(seuser, username) != 0) {
		if (checkPasswdAccess(PASSWD__PASSWD) != 0)
			bb_error_msg_and_die("SELinux: access denied");
	}
	if (ENABLE_FEATURE_CLEAN_UP)
		freecon(context);
}
#else
# define check_selinux_update_passwd(username) ((void)0)
#endif

/*
 1) add a user: update_passwd(FILE, USER, REMAINING_PWLINE, NULL)
    only if CONFIG_ADDUSER=y and applet_name[0] == 'a' like in adduser

 2) add a group: update_passwd(FILE, GROUP, REMAINING_GRLINE, NULL)
    only if CONFIG_ADDGROUP=y and applet_name[0] == 'a' like in addgroup

 3) add a user to a group: update_passwd(FILE, GROUP, NULL, MEMBER)
    only if CONFIG_FEATURE_ADDUSER_TO_GROUP=y, applet_name[0] == 'a'
    like in addgroup and member != NULL

 4) delete a user: update_passwd(FILE, USER, NULL, NULL)

 5) delete a group: update_passwd(FILE, GROUP, NULL, NULL)

 6) delete a user from a group: update_passwd(FILE, GROUP, NULL, MEMBER)
    only if CONFIG_FEATURE_DEL_USER_FROM_GROUP=y and member != NULL

 7) change user's passord: update_passwd(FILE, USER, NEW_PASSWD, NULL)
    only if CONFIG_PASSWD=y and applet_name[0] == 'p' like in passwd
    or if CONFIG_CHPASSWD=y and applet_name[0] == 'c' like in chpasswd

 This function does not validate the arguments fed to it
 so the calling program should take care of that.

 Returns number of lines changed, or -1 on error.
*/
int FAST_FUNC update_passwd(const char *filename,
		const char *name,
		const char *new_passwd,
		const char *member)
{
#if !(ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP)
#define member NULL
#endif
	struct stat sb;
	struct flock lock;
	FILE *old_fp;
	FILE *new_fp;
	char *fnamesfx;
	char *sfx_char;
	char *name_colon;
	unsigned user_len;
	int old_fd;
	int new_fd;
	int i;
	int changed_lines;
	int ret = -1; /* failure */
	/* used as a bool: "are we modifying /etc/shadow?" */
#if ENABLE_FEATURE_SHADOWPASSWDS
	const char *shadow = strstr(filename, "shadow");
#else
# define shadow NULL
#endif

	filename = xmalloc_follow_symlinks(filename);
	if (filename == NULL)
		return ret;

	check_selinux_update_passwd(name);

	/* New passwd file, "/etc/passwd+" for now */
	fnamesfx = xasprintf("%s+", filename);
	sfx_char = &fnamesfx[strlen(fnamesfx)-1];
	name_colon = xasprintf("%s:", name);
	user_len = strlen(name_colon);

	if (shadow)
		old_fp = fopen(filename, "r+");
	else
		old_fp = fopen_or_warn(filename, "r+");
	if (!old_fp) {
		if (shadow)
			ret = 0; /* missing shadow is not an error */
		goto free_mem;
	}
	old_fd = fileno(old_fp);

	selinux_preserve_fcontext(old_fd);

	/* 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(fnamesfx, 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("can't create '%s'", fnamesfx);
	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);
	}
	errno = 0;
	new_fp = xfdopen_for_write(new_fd);

	/* Backup file is "/etc/passwd-" */
	*sfx_char = '-';
	/* Delete old backup */
	i = (unlink(fnamesfx) && errno != ENOENT);
	/* Create backup as a hardlink to current */
	if (i || link(filename, fnamesfx))
		bb_perror_msg("warning: can't create backup copy '%s'",
				fnamesfx);
	*sfx_char = '+';

	/* 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: can't lock '%s'", filename);
	lock.l_type = F_UNLCK;

	/* Read current password file, write updated /etc/passwd+ */
	changed_lines = 0;
	while (1) {
		char *cp, *line;

		line = xmalloc_fgetline(old_fp);
		if (!line) /* EOF/error */
			break;
		if (strncmp(name_colon, line, user_len) != 0) {
			fprintf(new_fp, "%s\n", line);
			goto next;
		}

		/* We have a match with "name:"... */
		cp = line + user_len; /* move past name: */

#if ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP
		if (member) {
			/* It's actually /etc/group+, not /etc/passwd+ */
			if (ENABLE_FEATURE_ADDUSER_TO_GROUP
			 && applet_name[0] == 'a'
			) {
				/* Add user to group */
				fprintf(new_fp, "%s%s%s\n", line,
					last_char_is(line, ':') ? "" : ",",
					member);
				changed_lines++;
			} else if (ENABLE_FEATURE_DEL_USER_FROM_GROUP
			/* && applet_name[0] == 'd' */
			) {
				/* Delete user from group */
				char *tmp;
				const char *fmt = "%s";

				/* find the start of the member list: last ':' */
				cp = strrchr(line, ':');
				/* cut it */
				*cp++ = '\0';
				/* write the cut line name:passwd:gid:
				 * or name:!:: */
				fprintf(new_fp, "%s:", line);
				/* parse the tokens of the member list */
				tmp = cp;
				while ((cp = strsep(&tmp, ",")) != NULL) {
					if (strcmp(member, cp) != 0) {
						fprintf(new_fp, fmt, cp);
						fmt = ",%s";
					} else {
						/* found member, skip it */
						changed_lines++;
					}
				}
				fprintf(new_fp, "\n");
			}
		} else
#endif
		if ((ENABLE_PASSWD && applet_name[0] == 'p')
		 || (ENABLE_CHPASSWD && applet_name[0] == 'c')
		) {
			/* Change passwd */
			cp = strchrnul(cp, ':'); /* move past old passwd */

			if (shadow && *cp == ':') {
				/* /etc/shadow's field 3 (passwd change date) needs updating */
				/* move past old change date */
				cp = strchrnul(cp + 1, ':');
				/* "name:" + "new_passwd" + ":" + "change date" + ":rest of line" */
				fprintf(new_fp, "%s%s:%u%s\n", name_colon, new_passwd,
					(unsigned)(time(NULL)) / (24*60*60), cp);
			} else {
				/* "name:" + "new_passwd" + ":rest of line" */
				fprintf(new_fp, "%s%s%s\n", name_colon, new_passwd, cp);
			}
			changed_lines++;
		} /* else delete user or group: skip the line */
 next:
		free(line);
	}

	if (changed_lines == 0) {
#if ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP
		if (member) {
			if (ENABLE_ADDGROUP && applet_name[0] == 'a')
				bb_error_msg("can't find %s in %s", name, filename);
			if (ENABLE_DELGROUP && applet_name[0] == 'd')
				bb_error_msg("can't find %s in %s", member, filename);
		}
#endif
		if ((ENABLE_ADDUSER || ENABLE_ADDGROUP)
		 && applet_name[0] == 'a' && !member
		) {
			/* add user or group */
			fprintf(new_fp, "%s%s\n", name_colon, new_passwd);
			changed_lines++;
		}
	}

	fcntl(old_fd, F_SETLK, &lock);

	/* We do want all of them to execute, thus | instead of || */
	errno = 0;
	if ((ferror(old_fp) | fflush(new_fp) | fsync(new_fd) | fclose(new_fp))
	 || rename(fnamesfx, filename)
	) {
		/* At least one of those failed */
		bb_perror_nomsg();
		goto unlink_new;
	}
	/* Success: ret >= 0 */
	ret = changed_lines;

 unlink_new:
	if (ret < 0)
		unlink(fnamesfx);

 close_old_fp:
	fclose(old_fp);

 free_mem:
	free(fnamesfx);
	free((char *)filename);
	free(name_colon);
	return ret;
}
1	niro	816	/* vi: set sw=4 ts=4: */
2			/*
3			* update_passwd
4			*
5			* update_passwd is a common function for passwd and chpasswd applets;
6			* it is responsible for updating password file (i.e. /etc/passwd or
7			* /etc/shadow) for a given user and password.
8			*
9			* Moved from loginutils/passwd.c by Alexander Shishkin <virtuoso@slind.org>
10	niro	984	*
11			* Modified to be able to add or delete users, groups and users to/from groups
12			* by Tito Ragusa <farmatito@tiscali.it>
13			*
14			* Licensed under GPLv2, see file LICENSE in this tarball for details.
15	niro	816	*/
16			#include "libbb.h"
17
18			#if ENABLE_SELINUX
19			static void check_selinux_update_passwd(const char *username)
20			{
21			security_context_t context;
22			char *seuser;
23
24			if (getuid() != (uid_t)0 \|\| is_selinux_enabled() == 0)
25			return; /* No need to check */
26
27			if (getprevcon_raw(&context) < 0)
28			bb_perror_msg_and_die("getprevcon failed");
29			seuser = strtok(context, ":");
30			if (!seuser)
31			bb_error_msg_and_die("invalid context '%s'", context);
32			if (strcmp(seuser, username) != 0) {
33			if (checkPasswdAccess(PASSWD__PASSWD) != 0)
34			bb_error_msg_and_die("SELinux: access denied");
35			}
36			if (ENABLE_FEATURE_CLEAN_UP)
37			freecon(context);
38			}
39			#else
40	niro	984	# define check_selinux_update_passwd(username) ((void)0)
41	niro	816	#endif
42
43	niro	984	/*
44			1) add a user: update_passwd(FILE, USER, REMAINING_PWLINE, NULL)
45			only if CONFIG_ADDUSER=y and applet_name[0] == 'a' like in adduser
46
47			2) add a group: update_passwd(FILE, GROUP, REMAINING_GRLINE, NULL)
48			only if CONFIG_ADDGROUP=y and applet_name[0] == 'a' like in addgroup
49
50			3) add a user to a group: update_passwd(FILE, GROUP, NULL, MEMBER)
51			only if CONFIG_FEATURE_ADDUSER_TO_GROUP=y, applet_name[0] == 'a'
52			like in addgroup and member != NULL
53
54			4) delete a user: update_passwd(FILE, USER, NULL, NULL)
55
56			5) delete a group: update_passwd(FILE, GROUP, NULL, NULL)
57
58			6) delete a user from a group: update_passwd(FILE, GROUP, NULL, MEMBER)
59			only if CONFIG_FEATURE_DEL_USER_FROM_GROUP=y and member != NULL
60
61			7) change user's passord: update_passwd(FILE, USER, NEW_PASSWD, NULL)
62			only if CONFIG_PASSWD=y and applet_name[0] == 'p' like in passwd
63			or if CONFIG_CHPASSWD=y and applet_name[0] == 'c' like in chpasswd
64
65			This function does not validate the arguments fed to it
66			so the calling program should take care of that.
67
68			Returns number of lines changed, or -1 on error.
69			*/
70			int FAST_FUNC update_passwd(const char *filename,
71			const char *name,
72			const char *new_passwd,
73			const char *member)
74	niro	816	{
75	niro	984	#if !(ENABLE_FEATURE_ADDUSER_TO_GROUP \|\| ENABLE_FEATURE_DEL_USER_FROM_GROUP)
76			#define member NULL
77			#endif
78	niro	816	struct stat sb;
79			struct flock lock;
80			FILE *old_fp;
81			FILE *new_fp;
82			char *fnamesfx;
83			char *sfx_char;
84	niro	984	char *name_colon;
85	niro	816	unsigned user_len;
86			int old_fd;
87			int new_fd;
88			int i;
89	niro	984	int changed_lines;
90	niro	816	int ret = -1; /* failure */
91	niro	984	/* used as a bool: "are we modifying /etc/shadow?" */
92			#if ENABLE_FEATURE_SHADOWPASSWDS
93			const char *shadow = strstr(filename, "shadow");
94			#else
95			# define shadow NULL
96			#endif
97	niro	816
98			filename = xmalloc_follow_symlinks(filename);
99			if (filename == NULL)
100	niro	984	return ret;
101	niro	816
102	niro	984	check_selinux_update_passwd(name);
103	niro	816
104			/* New passwd file, "/etc/passwd+" for now */
105			fnamesfx = xasprintf("%s+", filename);
106			sfx_char = &fnamesfx[strlen(fnamesfx)-1];
107	niro	984	name_colon = xasprintf("%s:", name);
108			user_len = strlen(name_colon);
109	niro	816
110	niro	984	if (shadow)
111			old_fp = fopen(filename, "r+");
112			else
113			old_fp = fopen_or_warn(filename, "r+");
114			if (!old_fp) {
115			if (shadow)
116			ret = 0; /* missing shadow is not an error */
117	niro	816	goto free_mem;
118	niro	984	}
119	niro	816	old_fd = fileno(old_fp);
120
121			selinux_preserve_fcontext(old_fd);
122
123			/* Try to create "/etc/passwd+". Wait if it exists. */
124			i = 30;
125			do {
126			// FIXME: on last iteration try w/o O_EXCL but with O_TRUNC?
127			new_fd = open(fnamesfx, O_WRONLY\|O_CREAT\|O_EXCL, 0600);
128			if (new_fd >= 0) goto created;
129			if (errno != EEXIST) break;
130			usleep(100000); /* 0.1 sec */
131			} while (--i);
132	niro	984	bb_perror_msg("can't create '%s'", fnamesfx);
133	niro	816	goto close_old_fp;
134
135			created:
136			if (!fstat(old_fd, &sb)) {
137			fchmod(new_fd, sb.st_mode & 0777); /* ignore errors */
138			fchown(new_fd, sb.st_uid, sb.st_gid);
139			}
140	niro	984	errno = 0;
141			new_fp = xfdopen_for_write(new_fd);
142	niro	816
143			/* Backup file is "/etc/passwd-" */
144			*sfx_char = '-';
145			/* Delete old backup */
146			i = (unlink(fnamesfx) && errno != ENOENT);
147			/* Create backup as a hardlink to current */
148			if (i \|\| link(filename, fnamesfx))
149	niro	984	bb_perror_msg("warning: can't create backup copy '%s'",
150			fnamesfx);
151	niro	816	*sfx_char = '+';
152
153			/* Lock the password file before updating */
154			lock.l_type = F_WRLCK;
155			lock.l_whence = SEEK_SET;
156			lock.l_start = 0;
157			lock.l_len = 0;
158			if (fcntl(old_fd, F_SETLK, &lock) < 0)
159	niro	984	bb_perror_msg("warning: can't lock '%s'", filename);
160	niro	816	lock.l_type = F_UNLCK;
161
162			/* Read current password file, write updated /etc/passwd+ */
163	niro	984	changed_lines = 0;
164	niro	816	while (1) {
165	niro	984	char cp, line;
166
167			line = xmalloc_fgetline(old_fp);
168			if (!line) /* EOF/error */
169			break;
170			if (strncmp(name_colon, line, user_len) != 0) {
171			fprintf(new_fp, "%s\n", line);
172			goto next;
173			}
174
175			/* We have a match with "name:"... */
176			cp = line + user_len; /* move past name: */
177
178			#if ENABLE_FEATURE_ADDUSER_TO_GROUP \|\| ENABLE_FEATURE_DEL_USER_FROM_GROUP
179			if (member) {
180			/* It's actually /etc/group+, not /etc/passwd+ */
181			if (ENABLE_FEATURE_ADDUSER_TO_GROUP
182			&& applet_name[0] == 'a'
183			) {
184			/* Add user to group */
185			fprintf(new_fp, "%s%s%s\n", line,
186			last_char_is(line, ':') ? "" : ",",
187			member);
188			changed_lines++;
189			} else if (ENABLE_FEATURE_DEL_USER_FROM_GROUP
190			/* && applet_name[0] == 'd' */
191			) {
192			/* Delete user from group */
193			char *tmp;
194			const char *fmt = "%s";
195
196			/* find the start of the member list: last ':' */
197			cp = strrchr(line, ':');
198			/* cut it */
199			*cp++ = '\0';
200			/* write the cut line name:passwd:gid:
201			* or name:!:: */
202			fprintf(new_fp, "%s:", line);
203			/* parse the tokens of the member list */
204			tmp = cp;
205			while ((cp = strsep(&tmp, ",")) != NULL) {
206			if (strcmp(member, cp) != 0) {
207			fprintf(new_fp, fmt, cp);
208			fmt = ",%s";
209			} else {
210			/* found member, skip it */
211			changed_lines++;
212			}
213			}
214			fprintf(new_fp, "\n");
215			}
216	niro	816	} else
217	niro	984	#endif
218			if ((ENABLE_PASSWD && applet_name[0] == 'p')
219			\|\| (ENABLE_CHPASSWD && applet_name[0] == 'c')
220			) {
221			/* Change passwd */
222			cp = strchrnul(cp, ':'); /* move past old passwd */
223
224			if (shadow && *cp == ':') {
225			/* /etc/shadow's field 3 (passwd change date) needs updating */
226			/* move past old change date */
227			cp = strchrnul(cp + 1, ':');
228			/* "name:" + "new_passwd" + ":" + "change date" + ":rest of line" */
229			fprintf(new_fp, "%s%s:%u%s\n", name_colon, new_passwd,
230			(unsigned)(time(NULL)) / (246060), cp);
231			} else {
232			/* "name:" + "new_passwd" + ":rest of line" */
233			fprintf(new_fp, "%s%s%s\n", name_colon, new_passwd, cp);
234			}
235			changed_lines++;
236			} /* else delete user or group: skip the line */
237			next:
238	niro	816	free(line);
239			}
240	niro	984
241			if (changed_lines == 0) {
242			#if ENABLE_FEATURE_ADDUSER_TO_GROUP \|\| ENABLE_FEATURE_DEL_USER_FROM_GROUP
243			if (member) {
244			if (ENABLE_ADDGROUP && applet_name[0] == 'a')
245			bb_error_msg("can't find %s in %s", name, filename);
246			if (ENABLE_DELGROUP && applet_name[0] == 'd')
247			bb_error_msg("can't find %s in %s", member, filename);
248			}
249			#endif
250			if ((ENABLE_ADDUSER \|\| ENABLE_ADDGROUP)
251			&& applet_name[0] == 'a' && !member
252			) {
253			/* add user or group */
254			fprintf(new_fp, "%s%s\n", name_colon, new_passwd);
255			changed_lines++;
256			}
257			}
258
259	niro	816	fcntl(old_fd, F_SETLK, &lock);
260
261			/* We do want all of them to execute, thus \| instead of \|\| */
262	niro	984	errno = 0;
263	niro	816	if ((ferror(old_fp) \| fflush(new_fp) \| fsync(new_fd) \| fclose(new_fp))
264			\|\| rename(fnamesfx, filename)
265			) {
266			/* At least one of those failed */
267	niro	984	bb_perror_nomsg();
268	niro	816	goto unlink_new;
269			}
270	niro	984	/* Success: ret >= 0 */
271			ret = changed_lines;
272	niro	816
273			unlink_new:
274	niro	984	if (ret < 0)
275			unlink(fnamesfx);
276	niro	816
277			close_old_fp:
278			fclose(old_fp);
279
280			free_mem:
281			free(fnamesfx);
282			free((char *)filename);
283	niro	984	free(name_colon);
284	niro	816	return ret;
285			}