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Testcase: setuidgid 1:1 strace ash -c 'test -x TODO; test -x TODO; echo $?' should show that second "test -x" does not query ids again. function old new delta ash_main 1236 1256 +20 get_cached_euid - 19 +19 get_cached_egid - 19 +19 test_main 56 72 +16 test_exec 119 135 +16 is_in_supplementary_groups 52 57 +5 nexpr 718 702 -16 ------------------------------------------------------------------------------ (add/remove: 2/0 grow/shrink: 4/1 up/down: 95/-16) Total: 79 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
81 lines
1.8 KiB
C
81 lines
1.8 KiB
C
/*
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* Utility routines.
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*
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* Copyright (C) 2017 Denys Vlasenko
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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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//kbuild:lib-y += bb_getgroups.o
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#include "libbb.h"
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gid_t* FAST_FUNC bb_getgroups(int *ngroups, gid_t *group_array)
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{
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int n = ngroups ? *ngroups : 0;
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/* getgroups may be a bit expensive, try to use it only once */
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if (n < 32)
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n = 32;
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for (;;) {
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// FIXME: ash tries so hard to not die on OOM (when we are called from test),
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// and we spoil it with just one xrealloc here
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group_array = xrealloc(group_array, (n+1) * sizeof(group_array[0]));
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n = getgroups(n, group_array);
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/*
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* If buffer is too small, kernel does not return new_n > n.
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* It returns -1 and EINVAL:
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*/
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if (n >= 0) {
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/* Terminator for bb_getgroups(NULL, NULL) usage */
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group_array[n] = (gid_t) -1;
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break;
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}
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if (errno == EINVAL) { /* too small? */
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/* This is the way to ask kernel how big the array is */
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n = getgroups(0, group_array);
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continue;
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}
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/* Some other error (should never happen on Linux) */
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bb_simple_perror_msg_and_die("getgroups");
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}
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if (ngroups)
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*ngroups = n;
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return group_array;
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}
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uid_t FAST_FUNC get_cached_euid(uid_t *euid)
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{
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if (*euid == (uid_t)-1)
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*euid = geteuid();
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return *euid;
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}
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gid_t FAST_FUNC get_cached_egid(gid_t *egid)
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{
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if (*egid == (gid_t)-1)
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*egid = getegid();
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return *egid;
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}
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/* Return non-zero if GID is in our supplementary group list. */
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int FAST_FUNC is_in_supplementary_groups(struct cached_groupinfo *groupinfo, gid_t gid)
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{
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int i;
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int ngroups;
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gid_t *group_array;
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if (groupinfo->ngroups == 0)
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groupinfo->supplementary_array = bb_getgroups(&groupinfo->ngroups, NULL);
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ngroups = groupinfo->ngroups;
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group_array = groupinfo->supplementary_array;
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/* Search through the list looking for GID. */
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for (i = 0; i < ngroups; i++)
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if (gid == group_array[i])
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return 1;
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return 0;
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}
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