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dfb8e514cf
Some tunable values and their minimum/maximum values must be determinted at run-time. Add TUNABLE_SET_WITH_BOUNDS and TUNABLE_SET_WITH_BOUNDS_FULL to update tunable value together with minimum and maximum values. __tunable_set_val is updated to set tunable value as well as min/max values.
439 lines
11 KiB
C
439 lines
11 KiB
C
/* The tunable framework. See the README.tunables to know how to use the
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tunable in a glibc module.
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Copyright (C) 2016-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <startup.h>
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#include <stdint.h>
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#include <stdbool.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <sysdep.h>
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#include <fcntl.h>
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#include <ldsodefs.h>
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#define TUNABLES_INTERNAL 1
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#include "dl-tunables.h"
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#include <not-errno.h>
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#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
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# define GLIBC_TUNABLES "GLIBC_TUNABLES"
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#endif
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#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
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static char *
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tunables_strdup (const char *in)
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{
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size_t i = 0;
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while (in[i++] != '\0');
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char *out = __sbrk (i);
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/* For most of the tunables code, we ignore user errors. However,
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this is a system error - and running out of memory at program
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startup should be reported, so we do. */
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if (out == (void *)-1)
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_dl_fatal_printf ("sbrk() failure while processing tunables\n");
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i--;
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while (i-- > 0)
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out[i] = in[i];
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return out;
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}
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#endif
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static char **
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get_next_env (char **envp, char **name, size_t *namelen, char **val,
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char ***prev_envp)
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{
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while (envp != NULL && *envp != NULL)
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{
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char **prev = envp;
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char *envline = *envp++;
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int len = 0;
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while (envline[len] != '\0' && envline[len] != '=')
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len++;
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/* Just the name and no value, go to the next one. */
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if (envline[len] == '\0')
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continue;
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*name = envline;
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*namelen = len;
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*val = &envline[len + 1];
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*prev_envp = prev;
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return envp;
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}
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return NULL;
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}
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#define TUNABLE_SET_VAL_IF_VALID_RANGE(__cur, __val, __type) \
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({ \
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__type min = (__cur)->type.min; \
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__type max = (__cur)->type.max; \
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\
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if ((__type) (__val) >= min && (__type) (__val) <= max) \
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{ \
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(__cur)->val.numval = (__val); \
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(__cur)->initialized = true; \
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} \
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})
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#define TUNABLE_SET_BOUNDS_IF_VALID(__cur, __minp, __maxp, __type) \
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({ \
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if (__minp != NULL) \
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{ \
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/* MIN is specified. */ \
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__type min = *((__type *) __minp); \
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if (__maxp != NULL) \
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{ \
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/* Both MIN and MAX are specified. */ \
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__type max = *((__type *) __maxp); \
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if (max >= min \
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&& max <= (__cur)->type.max \
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&& min >= (__cur)->type.min) \
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{ \
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(__cur)->type.min = min; \
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(__cur)->type.max = max; \
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} \
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} \
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else if (min > (__cur)->type.min && min <= (__cur)->type.max) \
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{ \
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/* Only MIN is specified. */ \
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(__cur)->type.min = min; \
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} \
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} \
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else if (__maxp != NULL) \
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{ \
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/* Only MAX is specified. */ \
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__type max = *((__type *) __maxp); \
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if (max < (__cur)->type.max && max >= (__cur)->type.min) \
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(__cur)->type.max = max; \
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} \
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})
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static void
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do_tunable_update_val (tunable_t *cur, const void *valp,
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const void *minp, const void *maxp)
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{
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uint64_t val;
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if (cur->type.type_code != TUNABLE_TYPE_STRING)
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val = *((int64_t *) valp);
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switch (cur->type.type_code)
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{
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case TUNABLE_TYPE_INT_32:
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{
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TUNABLE_SET_BOUNDS_IF_VALID (cur, minp, maxp, int64_t);
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TUNABLE_SET_VAL_IF_VALID_RANGE (cur, val, int64_t);
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break;
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}
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case TUNABLE_TYPE_UINT_64:
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{
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TUNABLE_SET_BOUNDS_IF_VALID (cur, minp, maxp, uint64_t);
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TUNABLE_SET_VAL_IF_VALID_RANGE (cur, val, uint64_t);
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break;
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}
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case TUNABLE_TYPE_SIZE_T:
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{
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TUNABLE_SET_BOUNDS_IF_VALID (cur, minp, maxp, uint64_t);
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TUNABLE_SET_VAL_IF_VALID_RANGE (cur, val, uint64_t);
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break;
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}
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case TUNABLE_TYPE_STRING:
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{
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cur->val.strval = valp;
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break;
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}
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default:
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__builtin_unreachable ();
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}
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}
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/* Validate range of the input value and initialize the tunable CUR if it looks
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good. */
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static void
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tunable_initialize (tunable_t *cur, const char *strval)
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{
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uint64_t val;
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const void *valp;
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if (cur->type.type_code != TUNABLE_TYPE_STRING)
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{
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val = _dl_strtoul (strval, NULL);
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valp = &val;
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}
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else
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{
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cur->initialized = true;
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valp = strval;
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}
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do_tunable_update_val (cur, valp, NULL, NULL);
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}
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void
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__tunable_set_val (tunable_id_t id, void *valp, void *minp, void *maxp)
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{
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tunable_t *cur = &tunable_list[id];
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do_tunable_update_val (cur, valp, minp, maxp);
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}
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#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
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/* Parse the tunable string TUNESTR and adjust it to drop any tunables that may
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be unsafe for AT_SECURE processes so that it can be used as the new
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environment variable value for GLIBC_TUNABLES. VALSTRING is the original
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environment variable string which we use to make NULL terminated values so
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that we don't have to allocate memory again for it. */
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static void
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parse_tunables (char *tunestr, char *valstring)
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{
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if (tunestr == NULL || *tunestr == '\0')
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return;
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char *p = tunestr;
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while (true)
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{
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char *name = p;
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size_t len = 0;
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/* First, find where the name ends. */
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while (p[len] != '=' && p[len] != ':' && p[len] != '\0')
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len++;
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/* If we reach the end of the string before getting a valid name-value
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pair, bail out. */
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if (p[len] == '\0')
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return;
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/* We did not find a valid name-value pair before encountering the
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colon. */
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if (p[len]== ':')
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{
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p += len + 1;
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continue;
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}
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p += len + 1;
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/* Take the value from the valstring since we need to NULL terminate it. */
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char *value = &valstring[p - tunestr];
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len = 0;
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while (p[len] != ':' && p[len] != '\0')
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len++;
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/* Add the tunable if it exists. */
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for (size_t i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
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{
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tunable_t *cur = &tunable_list[i];
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if (tunable_is_name (cur->name, name))
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{
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/* If we are in a secure context (AT_SECURE) then ignore the tunable
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unless it is explicitly marked as secure. Tunable values take
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precedence over their envvar aliases. */
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if (__libc_enable_secure)
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{
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if (cur->security_level == TUNABLE_SECLEVEL_SXID_ERASE)
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{
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if (p[len] == '\0')
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{
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/* Last tunable in the valstring. Null-terminate and
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return. */
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*name = '\0';
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return;
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}
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else
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{
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/* Remove the current tunable from the string. We do
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this by overwriting the string starting from NAME
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(which is where the current tunable begins) with
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the remainder of the string. We then have P point
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to NAME so that we continue in the correct
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position in the valstring. */
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char *q = &p[len + 1];
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p = name;
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while (*q != '\0')
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*name++ = *q++;
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name[0] = '\0';
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len = 0;
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}
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}
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if (cur->security_level != TUNABLE_SECLEVEL_NONE)
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break;
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}
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value[len] = '\0';
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tunable_initialize (cur, value);
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break;
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}
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}
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if (p[len] == '\0')
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return;
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else
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p += len + 1;
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}
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}
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#endif
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/* Enable the glibc.malloc.check tunable in SETUID/SETGID programs only when
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the system administrator has created the /etc/suid-debug file. This is a
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special case where we want to conditionally enable/disable a tunable even
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for setuid binaries. We use the special version of access() to avoid
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setting ERRNO, which is a TLS variable since TLS has not yet been set
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up. */
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static __always_inline void
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maybe_enable_malloc_check (void)
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{
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tunable_id_t id = TUNABLE_ENUM_NAME (glibc, malloc, check);
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if (__libc_enable_secure && __access_noerrno ("/etc/suid-debug", F_OK) == 0)
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tunable_list[id].security_level = TUNABLE_SECLEVEL_NONE;
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}
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/* Initialize the tunables list from the environment. For now we only use the
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ENV_ALIAS to find values. Later we will also use the tunable names to find
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values. */
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void
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__tunables_init (char **envp)
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{
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char *envname = NULL;
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char *envval = NULL;
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size_t len = 0;
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char **prev_envp = envp;
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maybe_enable_malloc_check ();
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while ((envp = get_next_env (envp, &envname, &len, &envval,
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&prev_envp)) != NULL)
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{
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#if TUNABLES_FRONTEND == TUNABLES_FRONTEND_valstring
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if (tunable_is_name (GLIBC_TUNABLES, envname))
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{
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char *new_env = tunables_strdup (envname);
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if (new_env != NULL)
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parse_tunables (new_env + len + 1, envval);
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/* Put in the updated envval. */
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*prev_envp = new_env;
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continue;
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}
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#endif
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for (int i = 0; i < sizeof (tunable_list) / sizeof (tunable_t); i++)
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{
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tunable_t *cur = &tunable_list[i];
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/* Skip over tunables that have either been set already or should be
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skipped. */
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if (cur->initialized || cur->env_alias == NULL)
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continue;
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const char *name = cur->env_alias;
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/* We have a match. Initialize and move on to the next line. */
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if (tunable_is_name (name, envname))
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{
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/* For AT_SECURE binaries, we need to check the security settings of
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the tunable and decide whether we read the value and also whether
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we erase the value so that child processes don't inherit them in
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the environment. */
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if (__libc_enable_secure)
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{
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if (cur->security_level == TUNABLE_SECLEVEL_SXID_ERASE)
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{
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/* Erase the environment variable. */
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char **ep = prev_envp;
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while (*ep != NULL)
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{
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if (tunable_is_name (name, *ep))
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{
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char **dp = ep;
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do
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dp[0] = dp[1];
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while (*dp++);
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}
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else
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++ep;
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}
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/* Reset the iterator so that we read the environment again
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from the point we erased. */
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envp = prev_envp;
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}
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if (cur->security_level != TUNABLE_SECLEVEL_NONE)
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continue;
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}
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tunable_initialize (cur, envval);
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break;
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}
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}
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}
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}
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/* Set the tunable value. This is called by the module that the tunable exists
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in. */
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void
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__tunable_get_val (tunable_id_t id, void *valp, tunable_callback_t callback)
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{
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tunable_t *cur = &tunable_list[id];
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switch (cur->type.type_code)
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{
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case TUNABLE_TYPE_UINT_64:
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{
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*((uint64_t *) valp) = (uint64_t) cur->val.numval;
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break;
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}
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case TUNABLE_TYPE_INT_32:
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{
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*((int32_t *) valp) = (int32_t) cur->val.numval;
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break;
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}
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case TUNABLE_TYPE_SIZE_T:
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{
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*((size_t *) valp) = (size_t) cur->val.numval;
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break;
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}
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case TUNABLE_TYPE_STRING:
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{
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*((const char **)valp) = cur->val.strval;
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break;
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}
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default:
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__builtin_unreachable ();
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}
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if (cur->initialized && callback != NULL)
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callback (&cur->val);
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}
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rtld_hidden_def (__tunable_get_val)
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