busybox/libbb/update_passwd.c
Denys Vlasenko 8dff01d06a libbb: introduce and use is_prefixed_with()
function                                             old     new   delta
is_prefixed_with                                       -      18     +18
complete_username                                     78      77      -1
man_main                                             737     735      -2
fsck_device                                          429     427      -2
unpack_ar_archive                                     80      76      -4
strip_unsafe_prefix                                  105     101      -4
singlemount                                         1054    1050      -4
rtc_adjtime_is_utc                                    90      86      -4
resolve_mount_spec                                    88      84      -4
parse_one_line                                      1029    1025      -4
parse_conf                                          1460    1456      -4
may_wakeup                                            83      79      -4
loadkmap_main                                        219     215      -4
get_irqs_from_stat                                   103      99      -4
get_header_cpio                                      913     909      -4
findfs_main                                           79      75      -4
fbsplash_main                                       1230    1226      -4
load_crontab                                         776     771      -5
expand_vars_to_list                                 1151    1146      -5
date_main                                            881     876      -5
skip_dev_pfx                                          30      24      -6
make_device                                         2199    2193      -6
complete_cmd_dir_file                                773     767      -6
run_applet_and_exit                                  715     708      -7
uudecode_main                                        321     313      -8
pwdx_main                                            197     189      -8
execute                                              568     560      -8
i2cdetect_main                                      1186    1176     -10
procps_scan                                         1242    1230     -12
procps_read_smaps                                   1017    1005     -12
process_module                                       746     734     -12
patch_main                                          1903    1891     -12
nfsmount                                            3572    3560     -12
stack_machine                                        126     112     -14
process_timer_stats                                  449     435     -14
match_fstype                                         111      97     -14
do_ipaddr                                           1344    1330     -14
open_list_and_close                                  359     343     -16
get_header_tar                                      1795    1779     -16
prepend_new_eth_table                                340     323     -17
fsck_main                                           1811    1794     -17
find_iface_state                                      56      38     -18
dnsd_main                                           1321    1303     -18
base_device                                          179     158     -21
find_keyword                                         104      82     -22
handle_incoming_and_exit                            2785    2762     -23
parse_and_put_prompt                                 774     746     -28
modinfo                                              347     317     -30
find_action                                          204     171     -33
update_passwd                                       1470    1436     -34
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/49 up/down: 18/-540)         Total: -522 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2015-03-12 17:48:34 +01:00

319 lines
8.4 KiB
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 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) {
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 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 (!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;
}
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;
}