libbb/update_passwd.c - busybox - Git at Google

 /* 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 source tree.
  */
 #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) {
 		security_class_t tclass;
 		access_vector_t av;

 		tclass = string_to_security_class("passwd");
 		if (tclass == 0)
 			goto die;
 		av = string_to_av_perm(tclass, "passwd");
 		if (av == 0)
 			goto die;

 		if (selinux_check_passwd_access(av) != 0)
  die:
 			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 password: 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

  8) delete a user from all groups: update_passwd(FILE, NULL, NULL, MEMBER)

  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;
 	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;

 	if (name)
 		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 ? name : "");

 	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) == 0) {
 		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 ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP
 		if (!name && member) {
 			/* Delete member from all groups */
 			/* line is "GROUP:PASSWD:[member1[,member2]...]" */
 			unsigned member_len = strlen(member);
 			char *list = strrchr(line, ':');
 			while (list) {
 				list++;
  next_list_element:
 				if (is_prefixed_with(list, member)) {
 					char c;
 					changed_lines++;
 					c = list[member_len];
 					if (c == '\0') {
 						if (list[-1] == ',')
 							list--;
 						*list = '\0';
 						break;
 					}
 					if (c == ',') {
 						overlapping_strcpy(list, list + member_len + 1);
 						goto next_list_element;
 					}
 					changed_lines--;
 				}
 				list = strchr(list, ',');
 			}
 			fprintf(new_fp, "%s\n", line);
 			goto next;
 		}
 #endif

 		cp = is_prefixed_with(line, name_colon);
 		if (!cp) {
 			fprintf(new_fp, "%s\n", line);
 			goto next;
 		}

 		/* We have a match with "name:"... */
 		/* cp points 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;
 }
	/* 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 source tree.
	*/
	#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) {
	security_class_t tclass;
	access_vector_t av;

	tclass = string_to_security_class("passwd");
	if (tclass == 0)
	goto die;
	av = string_to_av_perm(tclass, "passwd");
	if (av == 0)
	goto die;

	if (selinux_check_passwd_access(av) != 0)
	die:
	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 password: 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

	8) delete a user from all groups: update_passwd(FILE, NULL, NULL, MEMBER)

	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;
	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;

	if (name)
	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 ? name : "");

	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) == 0) {
	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 ENABLE_FEATURE_ADDUSER_TO_GROUP \|\| ENABLE_FEATURE_DEL_USER_FROM_GROUP
	if (!name && member) {
	/* Delete member from all groups */
	/* line is "GROUP:PASSWD:[member1[,member2]...]" */
	unsigned member_len = strlen(member);
	char *list = strrchr(line, ':');
	while (list) {
	list++;
	next_list_element:
	if (is_prefixed_with(list, member)) {
	char c;
	changed_lines++;
	c = list[member_len];
	if (c == '\0') {
	if (list[-1] == ',')
	list--;
	*list = '\0';
	break;
	}
	if (c == ',') {
	overlapping_strcpy(list, list + member_len + 1);
	goto next_list_element;
	}
	changed_lines--;
	}
	list = strchr(list, ',');
	}
	fprintf(new_fp, "%s\n", line);
	goto next;
	}
	#endif

	cp = is_prefixed_with(line, name_colon);
	if (!cp) {
	fprintf(new_fp, "%s\n", line);
	goto next;
	}

	/* We have a match with "name:"... */
	/* cp points 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)) / (246060), 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;
	}