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/* SAMHAIN file system integrity testing */
/* Copyright (C) 2018 Rainer Wichmann */
/* */
/* This program is free software; you can redistribute it */
/* and/or modify */
/* it under the terms of the GNU General Public License as */
/* published by */
/* the Free Software Foundation; either version 2 of the License, or */
/* (at your option) any later version. */
/* */
/* This program is distributed in the hope that it will be useful, */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
/* GNU General Public License for more details. */
/* */
/* You should have received a copy of the GNU General Public License */
/* along with this program; if not, write to the Free Software */
/* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
#include "config_xor.h"
#undef FIL__
#define FIL__ _("sh_subuid.c")
#include <sys/types.h>
#include <time.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#if defined(__linux__)
#include "samhain.h"
#include "sh_unix.h"
#define SH_SUBUID_FILE _("/etc/subuid")
#define SH_SUBGID_FILE _("/etc/subgid")
struct subuid_t {
char name[32];
unsigned long first;
unsigned long last;
struct subuid_t * next;
};
static time_t last_subuid = 0;
static time_t last_subgid = 0;
struct subuid_t * list_subuid = NULL;
struct subuid_t * list_subgid = NULL;
/* Check whether we need to re-read the subuid/subgid file
*/
static int needs_reread (char * file, time_t * last)
{
int retval = S_FALSE;
struct stat buf;
int status = retry_lstat (FIL__, __LINE__, file, &buf);
if (status == 0)
{
if ((buf.st_mtime - *last) > 1)
{
*last = buf.st_mtime;
retval = S_TRUE;
}
}
else if (status && errno == ENOENT)
{
/* If there was a file make sure we attempt to re-read
* to zero out the list.
*/
if (*last > 0) retval = S_TRUE;
*last = 0;
}
return retval;
}
/* free the whole list
*/
static void free_subordinate(struct subuid_t * head)
{
struct subuid_t * prev;
struct subuid_t * curr = head;
while (curr)
{
prev = curr;
curr = curr->next;
SH_FREE(prev);
}
return;
}
#define NFIELDS_SUBUID 3
static int get_ulong(char * str, unsigned long * result)
{
char * endptr;
errno = 0;
*result = strtoul(str, &endptr, 0);
if (*str != '\0' && *endptr == '\0' && errno != ERANGE)
return S_TRUE;
return S_FALSE;
}
/* Parse a single line into name / startuid / lastuid
*/
static struct subuid_t * parse_subordinate(char * line)
{
unsigned int nfields = NFIELDS_SUBUID;
size_t lengths[NFIELDS_SUBUID];
unsigned long start, count;
struct subuid_t * new;
char ** array = split_array(line, &nfields, ':', lengths);
if (nfields != NFIELDS_SUBUID)
{ SH_FREE(array); return NULL; }
if (S_TRUE != get_ulong(array[1], &start))
{ SH_FREE(array); return NULL; }
if ((S_TRUE != get_ulong(array[2], &count)) || (count == 0))
{ SH_FREE(array); return NULL; }
if (lengths[0] == 0)
{ SH_FREE(array); return NULL; }
/* we have checked that count != 0 */
--count;
if (start > (ULONG_MAX - count))
{ SH_FREE(array); return NULL; }
new = SH_ALLOC(sizeof(struct subuid_t));
sl_strlcpy(new->name, array[0], 32);
new->first = start;
new->last = start + count; /* start+count-1, but we already did --count */
new->next = NULL;
SH_FREE(array);
return new;
}
/* (re-)read the subuid/subgid file
*/
static void reread_subordinate (char * file, struct subuid_t ** head_ref)
{
SL_TICKET fd = (-1);
char line[1024];
if (*head_ref) { free_subordinate(*head_ref); *head_ref = NULL; }
fd = sl_open_read (FIL__, __LINE__, file, SL_YESPRIV);
if (!SL_ISERROR(fd))
{
while ( sh_unix_getline(fd, line, sizeof(line)) > 0 )
{
/* for invalid lines, NULL will be returned
*/
struct subuid_t * new = parse_subordinate(line);
if (new)
{
new->next = *head_ref;
*head_ref = new;
}
}
sl_close(fd);
}
return;
}
/* Return the username for a given subuid/subgid
*/
static char * get_name4id (unsigned long id, struct subuid_t * head)
{
struct subuid_t * cur = head;
while (cur)
{
if (id >= cur->first && id <= cur->last)
return cur->name;
cur = cur->next;
}
return NULL;
}
/***********************************************
*
* Public functions
*
***********************************************/
/* Returns username or NULL for a subuid
*/
char * sh_get_subuid (unsigned long subuid)
{
static int init = 0;
static char file[256];
if (!init) { sl_strlcpy(file, SH_SUBUID_FILE, sizeof(file)); init = 1; }
if (S_TRUE == needs_reread(file, &last_subuid))
reread_subordinate(file, &list_subuid);
return get_name4id (subuid, list_subuid);
}
/* Returns group name or NULL for subgid
*/
char * sh_get_subgid (unsigned long subgid)
{
static int init = 0;
static char file[256];
if (!init) { sl_strlcpy(file, SH_SUBGID_FILE, sizeof(file)); init = 1; }
if (S_TRUE == needs_reread(file, &last_subgid))
reread_subordinate(file, &list_subgid);
return get_name4id (subgid, list_subgid);
}
/* Not Linux, hence no sub(u|g)id
*/
#else
char * sh_get_subuid (unsigned long subuid)
{
(void) subuid;
return NULL;
}
char * sh_get_subgid (unsigned long subgid)
{
(void) subgid;
return NULL;
}
#endif
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