libbb: new function bb_getgroups() - allocating wrapper around getgroups()

function                                             old     new   delta
bb_getgroups                                           -     111    +111
nexpr                                                843     757     -86
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 0/1 up/down: 111/-86)            Total: 25 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2017-07-04 18:49:24 +02:00
parent 6a3bcf340a
commit a8cf9c5a3f
3 changed files with 63 additions and 26 deletions

View File

@ -563,26 +563,11 @@ static int binop(void)
/*return 1; - NOTREACHED */
}
static void initialize_group_array(void)
{
int n;
/* getgroups may be expensive, try to use it only once */
ngroups = 32;
do {
/* FIXME: ash tries so hard to not die on OOM,
* and we spoil it with just one xrealloc here */
/* We realloc, because test_main can be entered repeatedly by shell.
* Testcase (ash): 'while true; do test -x some_file; done'
* and watch top. (some_file must have owner != you) */
n = ngroups;
group_array = xrealloc(group_array, n * sizeof(gid_t));
ngroups = getgroups(n, group_array);
} while (ngroups > n);
group_array = bb_getgroups(&ngroups, NULL);
}
/* Return non-zero if GID is one that we have in our groups list. */
//XXX: FIXME: duplicate of existing libbb function?
// see toplevel TODO file:
@ -610,14 +595,10 @@ static int is_a_group_member(gid_t gid)
/* Do the same thing access(2) does, but use the effective uid and gid,
and don't make the mistake of telling root that any file is
executable. */
static int test_eaccess(char *path, int mode)
static int test_eaccess(struct stat *st, int mode)
{
struct stat st;
unsigned int euid = geteuid();
if (stat(path, &st) < 0)
return -1;
if (euid == 0) {
/* Root can read or write any file. */
if (mode != X_OK)
@ -625,16 +606,16 @@ static int test_eaccess(char *path, int mode)
/* Root can execute any file that has any one of the execute
* bits set. */
if (st.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))
if (st->st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))
return 0;
}
if (st.st_uid == euid) /* owner */
if (st->st_uid == euid) /* owner */
mode <<= 6;
else if (is_a_group_member(st.st_gid))
else if (is_a_group_member(st->st_gid))
mode <<= 3;
if (st.st_mode & mode)
if (st->st_mode & mode)
return 0;
return -1;
@ -667,7 +648,7 @@ static int filstat(char *nm, enum token mode)
i = W_OK;
if (mode == FILEX)
i = X_OK;
return test_eaccess(nm, i) == 0;
return test_eaccess(&s, i) == 0;
}
if (is_file_type(mode)) {
if (mode == FILREG)

View File

@ -1033,6 +1033,15 @@ void die_if_bad_username(const char* name) FAST_FUNC;
#else
#define die_if_bad_username(name) ((void)(name))
#endif
/*
* Returns (-1) terminated malloced result of getgroups().
* Reallocs group_array (useful for repeated calls).
* ngroups is an initial size of array. It is rounded up to 32 for realloc.
* ngroups is updated on return.
* ngroups can be NULL: bb_getgroups(NULL, NULL) is valid usage.
* Dies on errors (on Linux, only xrealloc can cause this, not internal getgroups call).
*/
gid_t *bb_getgroups(int *ngroups, gid_t *group_array) FAST_FUNC;
#if ENABLE_FEATURE_UTMP
void FAST_FUNC write_new_utmp(pid_t pid, int new_type, const char *tty_name, const char *username, const char *hostname);

47
libbb/bb_getgroups.c Normal file
View File

@ -0,0 +1,47 @@
/*
* Utility routines.
*
* Copyright (C) 2017 Denys Vlasenko
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
//kbuild:lib-y += bb_getgroups.o
#include "libbb.h"
gid_t* FAST_FUNC bb_getgroups(int *ngroups, gid_t *group_array)
{
int n = ngroups ? *ngroups : 0;
/* getgroups may be a bit expensive, try to use it only once */
if (n < 32)
n = 32;
for (;;) {
// FIXME: ash tries so hard to not die on OOM (when we are called from test),
// and we spoil it with just one xrealloc here
group_array = xrealloc(group_array, (n+1) * sizeof(group_array[0]));
n = getgroups(n, group_array);
/*
* If buffer is too small, kernel does not return new_n > n.
* It returns -1 and EINVAL:
*/
if (n >= 0) {
/* Terminator for bb_getgroups(NULL, NULL) usage */
group_array[n] = (gid_t) -1;
break;
}
if (errno == EINVAL) { /* too small? */
/* This is the way to ask kernel how big the array is */
n = getgroups(0, group_array);
continue;
}
/* Some other error (should never happen on Linux) */
bb_perror_msg_and_die("getgroups");
}
if (ngroups)
*ngroups = n;
return group_array;
}