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https://github.com/sheumann/hush.git
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286 lines
7.7 KiB
C
286 lines
7.7 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* update_passwd
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*
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* update_passwd is a common function for passwd and chpasswd applets;
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* it is responsible for updating password file (i.e. /etc/passwd or
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* /etc/shadow) for a given user and password.
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*
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* Moved from loginutils/passwd.c by Alexander Shishkin <virtuoso@slind.org>
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*
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* Modified to be able to add or delete users, groups and users to/from groups
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* by Tito Ragusa <farmatito@tiscali.it>
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*
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* Licensed under GPLv2, see file LICENSE in this source tree.
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*/
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#include "libbb.h"
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#if ENABLE_SELINUX
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static void check_selinux_update_passwd(const char *username)
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{
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security_context_t context;
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char *seuser;
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if (getuid() != (uid_t)0 || is_selinux_enabled() == 0)
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return; /* No need to check */
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if (getprevcon_raw(&context) < 0)
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bb_perror_msg_and_die("getprevcon failed");
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seuser = strtok(context, ":");
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if (!seuser)
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bb_error_msg_and_die("invalid context '%s'", context);
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if (strcmp(seuser, username) != 0) {
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if (checkPasswdAccess(PASSWD__PASSWD) != 0)
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bb_error_msg_and_die("SELinux: access denied");
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}
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if (ENABLE_FEATURE_CLEAN_UP)
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freecon(context);
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}
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#else
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# define check_selinux_update_passwd(username) ((void)0)
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#endif
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/*
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1) add a user: update_passwd(FILE, USER, REMAINING_PWLINE, NULL)
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only if CONFIG_ADDUSER=y and applet_name[0] == 'a' like in adduser
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2) add a group: update_passwd(FILE, GROUP, REMAINING_GRLINE, NULL)
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only if CONFIG_ADDGROUP=y and applet_name[0] == 'a' like in addgroup
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3) add a user to a group: update_passwd(FILE, GROUP, NULL, MEMBER)
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only if CONFIG_FEATURE_ADDUSER_TO_GROUP=y, applet_name[0] == 'a'
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like in addgroup and member != NULL
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4) delete a user: update_passwd(FILE, USER, NULL, NULL)
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5) delete a group: update_passwd(FILE, GROUP, NULL, NULL)
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6) delete a user from a group: update_passwd(FILE, GROUP, NULL, MEMBER)
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only if CONFIG_FEATURE_DEL_USER_FROM_GROUP=y and member != NULL
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7) change user's password: update_passwd(FILE, USER, NEW_PASSWD, NULL)
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only if CONFIG_PASSWD=y and applet_name[0] == 'p' like in passwd
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or if CONFIG_CHPASSWD=y and applet_name[0] == 'c' like in chpasswd
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This function does not validate the arguments fed to it
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so the calling program should take care of that.
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Returns number of lines changed, or -1 on error.
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*/
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int FAST_FUNC update_passwd(const char *filename,
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const char *name,
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const char *new_passwd,
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const char *member)
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{
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#if !(ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP)
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#define member NULL
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#endif
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struct stat sb;
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struct flock lock;
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FILE *old_fp;
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FILE *new_fp;
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char *fnamesfx;
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char *sfx_char;
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char *name_colon;
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unsigned user_len;
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int old_fd;
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int new_fd;
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int i;
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int changed_lines;
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int ret = -1; /* failure */
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/* used as a bool: "are we modifying /etc/shadow?" */
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#if ENABLE_FEATURE_SHADOWPASSWDS
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const char *shadow = strstr(filename, "shadow");
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#else
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# define shadow NULL
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#endif
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filename = xmalloc_follow_symlinks(filename);
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if (filename == NULL)
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return ret;
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check_selinux_update_passwd(name);
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/* New passwd file, "/etc/passwd+" for now */
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fnamesfx = xasprintf("%s+", filename);
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sfx_char = &fnamesfx[strlen(fnamesfx)-1];
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name_colon = xasprintf("%s:", name);
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user_len = strlen(name_colon);
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if (shadow)
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old_fp = fopen(filename, "r+");
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else
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old_fp = fopen_or_warn(filename, "r+");
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if (!old_fp) {
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if (shadow)
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ret = 0; /* missing shadow is not an error */
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goto free_mem;
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}
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old_fd = fileno(old_fp);
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selinux_preserve_fcontext(old_fd);
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/* Try to create "/etc/passwd+". Wait if it exists. */
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i = 30;
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do {
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// FIXME: on last iteration try w/o O_EXCL but with O_TRUNC?
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new_fd = open(fnamesfx, O_WRONLY|O_CREAT|O_EXCL, 0600);
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if (new_fd >= 0) goto created;
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if (errno != EEXIST) break;
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usleep(100000); /* 0.1 sec */
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} while (--i);
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bb_perror_msg("can't create '%s'", fnamesfx);
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goto close_old_fp;
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created:
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if (fstat(old_fd, &sb) == 0) {
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fchmod(new_fd, sb.st_mode & 0777); /* ignore errors */
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fchown(new_fd, sb.st_uid, sb.st_gid);
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}
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errno = 0;
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new_fp = xfdopen_for_write(new_fd);
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/* Backup file is "/etc/passwd-" */
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*sfx_char = '-';
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/* Delete old backup */
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i = (unlink(fnamesfx) && errno != ENOENT);
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/* Create backup as a hardlink to current */
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if (i || link(filename, fnamesfx))
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bb_perror_msg("warning: can't create backup copy '%s'",
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fnamesfx);
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*sfx_char = '+';
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/* Lock the password file before updating */
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lock.l_type = F_WRLCK;
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lock.l_whence = SEEK_SET;
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lock.l_start = 0;
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lock.l_len = 0;
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if (fcntl(old_fd, F_SETLK, &lock) < 0)
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bb_perror_msg("warning: can't lock '%s'", filename);
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lock.l_type = F_UNLCK;
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/* Read current password file, write updated /etc/passwd+ */
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changed_lines = 0;
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while (1) {
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char *cp, *line;
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line = xmalloc_fgetline(old_fp);
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if (!line) /* EOF/error */
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break;
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if (strncmp(name_colon, line, user_len) != 0) {
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fprintf(new_fp, "%s\n", line);
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goto next;
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}
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/* We have a match with "name:"... */
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cp = line + user_len; /* move past name: */
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#if ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP
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if (member) {
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/* It's actually /etc/group+, not /etc/passwd+ */
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if (ENABLE_FEATURE_ADDUSER_TO_GROUP
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&& applet_name[0] == 'a'
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) {
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/* Add user to group */
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fprintf(new_fp, "%s%s%s\n", line,
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last_char_is(line, ':') ? "" : ",",
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member);
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changed_lines++;
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} else if (ENABLE_FEATURE_DEL_USER_FROM_GROUP
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/* && applet_name[0] == 'd' */
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) {
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/* Delete user from group */
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char *tmp;
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const char *fmt = "%s";
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/* find the start of the member list: last ':' */
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cp = strrchr(line, ':');
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/* cut it */
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*cp++ = '\0';
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/* write the cut line name:passwd:gid:
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* or name:!:: */
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fprintf(new_fp, "%s:", line);
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/* parse the tokens of the member list */
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tmp = cp;
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while ((cp = strsep(&tmp, ",")) != NULL) {
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if (strcmp(member, cp) != 0) {
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fprintf(new_fp, fmt, cp);
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fmt = ",%s";
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} else {
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/* found member, skip it */
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changed_lines++;
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}
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}
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fprintf(new_fp, "\n");
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}
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} else
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#endif
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if ((ENABLE_PASSWD && applet_name[0] == 'p')
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|| (ENABLE_CHPASSWD && applet_name[0] == 'c')
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) {
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/* Change passwd */
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cp = strchrnul(cp, ':'); /* move past old passwd */
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if (shadow && *cp == ':') {
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/* /etc/shadow's field 3 (passwd change date) needs updating */
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/* move past old change date */
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cp = strchrnul(cp + 1, ':');
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/* "name:" + "new_passwd" + ":" + "change date" + ":rest of line" */
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fprintf(new_fp, "%s%s:%u%s\n", name_colon, new_passwd,
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(unsigned)(time(NULL)) / (24*60*60), cp);
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} else {
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/* "name:" + "new_passwd" + ":rest of line" */
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fprintf(new_fp, "%s%s%s\n", name_colon, new_passwd, cp);
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}
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changed_lines++;
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} /* else delete user or group: skip the line */
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next:
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free(line);
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}
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if (changed_lines == 0) {
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#if ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP
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if (member) {
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if (ENABLE_ADDGROUP && applet_name[0] == 'a')
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bb_error_msg("can't find %s in %s", name, filename);
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if (ENABLE_DELGROUP && applet_name[0] == 'd')
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bb_error_msg("can't find %s in %s", member, filename);
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}
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#endif
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if ((ENABLE_ADDUSER || ENABLE_ADDGROUP)
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&& applet_name[0] == 'a' && !member
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) {
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/* add user or group */
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fprintf(new_fp, "%s%s\n", name_colon, new_passwd);
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changed_lines++;
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}
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}
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fcntl(old_fd, F_SETLK, &lock);
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/* We do want all of them to execute, thus | instead of || */
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errno = 0;
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if ((ferror(old_fp) | fflush(new_fp) | fsync(new_fd) | fclose(new_fp))
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|| rename(fnamesfx, filename)
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) {
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/* At least one of those failed */
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bb_perror_nomsg();
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goto unlink_new;
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}
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/* Success: ret >= 0 */
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ret = changed_lines;
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unlink_new:
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if (ret < 0)
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unlink(fnamesfx);
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close_old_fp:
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fclose(old_fp);
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free_mem:
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free(fnamesfx);
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free((char *)filename);
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free(name_colon);
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return ret;
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}
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