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/* 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;
unsigned user_len;
int old_fd;
int new_fd;
int i;
int changed_lines;
int ret = -1; /* failure */
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 = xasprintf("%s:", name);
user_len = strlen(name);
if (ENABLE_FEATURE_SHADOWPASSWDS && strstr(filename, "shadow"))
old_fp = fopen(filename, "r+");
else
old_fp = fopen_or_warn(filename, "r+");
if (!old_fp)
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 = fdopen(new_fd, "w");
if (!new_fp) {
bb_perror_nomsg();
close(new_fd);
goto unlink_new;
}
/* 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, 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 */
/* name: + new_passwd + :rest of line */
fprintf(new_fp, "%s%s%s\n", name, new_passwd, cp);
changed_lines++;
} /* else delete user or group: skip the line */
next:
free(line);
}
if (changed_lines == 0) {
#if ENABLE_FEATURE_DEL_USER_FROM_GROUP
if (member)
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, 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((char *)name);
return ret;
}
|
