secure_sid_scripts.5 (2010 09)

s
secure_sid_scripts(5) secure_sid_scripts(5)
(Tunable Kernel Parameters)
NAME
secure_sid_scripts - controls whether setuid and setgid bits on scripts are honored
VALUES
Failsafe
0
Default
1
Allowed values
0-1
Recommended values
0-1
DESCRIPTION
This tunable controls whether setuid and setgid bits on executable scripts have any effect. Honoring
set*id on scripts make a system vulnerable to attack by malicious users.
The default value for this variable is 1, indicating that
set*id bits are to be ignored by the execve (2)
system call for higher security. The tunable can be set to 0 for a compatibility with older releases at the
expense of security. Hewlett-Packard strongly recommends that you not change the value of this tunable
unless there is an urgent need to do so.
When a script with
set*id bits is executed, the kernel generates the following error message to both the
terminal controlling and the system log. (To view the error message, use dmesg(1M) or inspect
/var/adm/syslog/syslog.log
.)
Warning: Ignoring set*id bit on program_name as the tunable
secure_sid_scripts is set.
Who is Expected to Change This Tunable?
Administrator.
Restrictions on Changing
Changes to this tunable take effect for new scripts started after the change.
When Should the Value of This Tunable Be Changed?
This tunable controls operational modes rather than data structure sizes and limits. The appropriate set-
ting for a system depends on whether you consider security or compatibility to be most important.
A value of
0 is compatible with previous releases of HP-UX, but it is also less secure.
A value of
1 provides security against race condition attacks exploiting set*id scripts.
What Are the Side Effects of Changing the Value
This tunable controls only executable scripts (not programs) with
set*id bit set. HP-UX does not ship
with any such scripts. If the customer wishes to use set*id scripts, third party applications such as
suidperl or sudo can be used. Alternatively, the shell script can be wrapped in a simple C program
that runs the shell script with appropriate permissions:
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#define SETUID_SCRIPT "/usr/local/bin/cdeject"
int main(int argc, char *const argv[])
{
if (strcmp(argv[1], SETUID_SCRIPT) == 0) {
execv(argv[1], argv+1);
perror(argv[0]);
} else {
fprintf(stderr, "%s is not a known setuid script\n",
argv[1] ? argv[1] : "unspecified-script" );
}
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1