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libc: add clearenv function

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The clearenv(3) function allows us to clear all environment
variable in one shot. This may be useful for security programs that
want to control the environment or what variables are passed to new
spawned programs.

Reviewed by:	scf, markj (secteam), 0mp (manpages)
Differential Revision:	https://reviews.freebsd.org/D28223
This commit is contained in:
Mariusz Zaborski 2021-11-07 16:15:28 +01:00
parent e9c7c6f5a0
commit 597b026757
7 changed files with 228 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/stdlib.h
View File

@ -283,6 +283,8 @@ int cgetset(const char *);
int cgetstr(char *, const char *, char **);
int cgetustr(char *, const char *, char **);
int clearenv(void);
int daemon(int, int);
int daemonfd(int, int);
char *devname(__dev_t, __mode_t);

3
lib/libc/stdlib/Makefile.inc
View File

@ -46,7 +46,8 @@ MAN+= a64l.3 abort.3 abs.3 alloca.3 atexit.3 atof.3 \
MLINKS+=a64l.3 l64a.3 a64l.3 l64a_r.3
MLINKS+=atol.3 atoll.3
MLINKS+=exit.3 _Exit.3
MLINKS+=getenv.3 putenv.3 getenv.3 setenv.3 getenv.3 unsetenv.3
MLINKS+=getenv.3 clearenv.3 getenv.3 putenv.3 getenv.3 setenv.3 \
getenv.3 unsetenv.3
MLINKS+=getopt_long.3 getopt_long_only.3
MLINKS+=hcreate.3 hdestroy.3 hcreate.3 hsearch.3
MLINKS+=hcreate.3 hcreate_r.3 hcreate.3 hdestroy_r.3 hcreate.3 hsearch_r.3

4
lib/libc/stdlib/Symbol.map
View File

@ -128,6 +128,10 @@ FBSD_1.6 {
srand;
};
FBSD_1.7 {
clearenv;
};
FBSDprivate_1.0 {
__system;
_system;

20
lib/libc/stdlib/getenv.3
View File

@ -32,10 +32,11 @@
.\" @(#)getenv.3 8.2 (Berkeley) 12/11/93
.\" $FreeBSD$
.\"
.Dd June 20, 2007
.Dd November 7, 2021
.Dt GETENV 3
.Os
.Sh NAME
.Nm clearenv ,
.Nm getenv ,
.Nm putenv ,
.Nm setenv ,
@ -45,6 +46,8 @@
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft int
.Fn clearenv "void"
.Ft char *
.Fn getenv "const char *name"
.Ft int
@ -59,6 +62,14 @@ host
.Em environment list .
.Pp
The
.Fn clearenv
function clears all environment variables.
New variables can be added using
.Fn setenv
and
.Fn putenv .
.Pp
The
.Fn getenv
function obtains the current value of the environment variable,
.Fa name .
@ -128,7 +139,7 @@ is not in the current environment,
.Dv NULL
is returned.
.Pp
.Rv -std setenv putenv unsetenv
.Rv -std clearenv setenv putenv unsetenv
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EINVAL
@ -211,6 +222,11 @@ This was changed to use
as the memory location of the ``name=value'' pair to follow the
.Tn POSIX
specification.
.Pp
The
.Fn clearenv
was added in
.Fx 14 .
.Sh BUGS
Successive calls to
.Fn setenv

25
lib/libc/stdlib/getenv.c
View File

@ -691,3 +691,28 @@ unsetenv(const char *name)
return (0);
}
/*
* Unset all variable by flagging them as inactive. No variable is
* ever freed.
*/
int
clearenv(void)
{
int ndx;
/* Initialize environment. */
if (__merge_environ() == -1 || (envVars == NULL && __build_env() == -1))
return (-1);
/* Remove from the end to not shuffle memory too much. */
for (ndx = envVarsTotal - 1; ndx >= 0; ndx--) {
envVars[ndx].active = false;
if (envVars[ndx].putenv)
__remove_putenv(ndx);
}
__rebuild_environ(0);
return (0);
}

1
lib/libc/tests/stdlib/Makefile
View File

@ -2,6 +2,7 @@
.include <src.opts.mk>
ATF_TESTS_C+= clearenv_test
ATF_TESTS_C+= dynthr_test
ATF_TESTS_C+= heapsort_test
ATF_TESTS_C+= mergesort_test

176
lib/libc/tests/stdlib/clearenv_test.c Normal file
View File

@ -0,0 +1,176 @@
/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (C) 2021 Mariusz Zaborski <oshogbo@FreeBSD.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Test for clearenv(3) routine.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <atf-c.h>
#include <stdio.h>
#include <stdlib.h>
#define TEST_VARIABLE "TEST_VAR"
#define TEST_SYSTEM_VARIABLE "PWD"
extern char **environ;
void
create_multiple_variables(int num)
{
char name[64];
char value[64];
int i;
for (i = 0; i < num; i++) {
snprintf(name, sizeof(name), "%s_%d", TEST_VARIABLE, i);
snprintf(value, sizeof(value), "%d", i);
ATF_CHECK(getenv(name) == NULL);
ATF_CHECK(setenv(name, value, 0) != -1);
ATF_CHECK_STREQ(getenv(name), value);
}
}
void
check_if_nulled_variables(int num)
{
char name[64];
int i;
for (i = 0; i < num; i++) {
snprintf(name, sizeof(name), "%s_%d", TEST_VARIABLE, i);
ATF_CHECK(getenv(name) == NULL);
}
}
ATF_TC_WITHOUT_HEAD(clearenv__single_var_test);
ATF_TC_BODY(clearenv__single_var_test, tc)
{
ATF_CHECK(setenv(TEST_VARIABLE, "true", 0) != -1);
ATF_CHECK_STREQ(getenv(TEST_VARIABLE), "true");
ATF_CHECK(clearenv() == 0);
ATF_CHECK(getenv(TEST_VARIABLE) == NULL);
}
ATF_TC_WITHOUT_HEAD(clearenv__multiple_vars_test);
ATF_TC_BODY(clearenv__multiple_vars_test, tc)
{
create_multiple_variables(10);
ATF_CHECK(clearenv() == 0);
check_if_nulled_variables(10);
}
ATF_TC_WITHOUT_HEAD(clearenv__recreated_vars_test);
ATF_TC_BODY(clearenv__recreated_vars_test, tc)
{
create_multiple_variables(10);
ATF_CHECK(clearenv() == 0);
check_if_nulled_variables(10);
create_multiple_variables(10);
}
ATF_TC_WITHOUT_HEAD(clearenv__system_var_test);
ATF_TC_BODY(clearenv__system_var_test, tc)
{
ATF_CHECK(getenv(TEST_SYSTEM_VARIABLE) != NULL);
ATF_CHECK(clearenv() == 0);
ATF_CHECK(getenv(TEST_SYSTEM_VARIABLE) == NULL);
}
ATF_TC_WITHOUT_HEAD(clearenv__recreated_system_var_test);
ATF_TC_BODY(clearenv__recreated_system_var_test, tc)
{
ATF_CHECK(getenv(TEST_SYSTEM_VARIABLE) != NULL);
ATF_CHECK(clearenv() == 0);
ATF_CHECK(getenv(TEST_SYSTEM_VARIABLE) == NULL);
ATF_CHECK(setenv(TEST_SYSTEM_VARIABLE, "test", 0) != -1);
ATF_CHECK_STREQ(getenv(TEST_SYSTEM_VARIABLE), "test");
}
ATF_TC_WITHOUT_HEAD(clearenv__double_clear_vars);
ATF_TC_BODY(clearenv__double_clear_vars, tc)
{
create_multiple_variables(10);
ATF_CHECK(clearenv() == 0);
check_if_nulled_variables(10);
ATF_CHECK(clearenv() == 0);
check_if_nulled_variables(10);
create_multiple_variables(10);
}
ATF_TC_WITHOUT_HEAD(clearenv__environ_null);
ATF_TC_BODY(clearenv__environ_null, tc)
{
ATF_CHECK(clearenv() == 0);
ATF_CHECK(environ == NULL);
}
ATF_TC_WITHOUT_HEAD(clearenv__putenv_vars);
ATF_TC_BODY(clearenv__putenv_vars, tc)
{
char buf[64], ref[64];
snprintf(buf, sizeof(buf), "%s=1", TEST_VARIABLE);
strcpy(ref, buf);
ATF_CHECK(getenv(TEST_VARIABLE) == NULL);
ATF_CHECK(putenv(buf) != -1);
ATF_CHECK(strcmp(getenv(TEST_VARIABLE), "1") == 0);
ATF_CHECK(clearenv() == 0);
ATF_CHECK(getenv(TEST_VARIABLE) == NULL);
ATF_CHECK(strcmp(buf, ref) == 0);
}
ATF_TP_ADD_TCS(tp)
{
ATF_TP_ADD_TC(tp, clearenv__single_var_test);
ATF_TP_ADD_TC(tp, clearenv__multiple_vars_test);
ATF_TP_ADD_TC(tp, clearenv__recreated_vars_test);
ATF_TP_ADD_TC(tp, clearenv__system_var_test);
ATF_TP_ADD_TC(tp, clearenv__recreated_system_var_test);
ATF_TP_ADD_TC(tp, clearenv__double_clear_vars);
ATF_TP_ADD_TC(tp, clearenv__environ_null);
ATF_TP_ADD_TC(tp, clearenv__putenv_vars);
return (atf_no_error());
}