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    <p>Since the <code>suid</code> bit on executables only changes the effective UID (EUID) the executable will run as, and not the real UID (RUID) which <code>getuid()</code> returns, and in addition to the restriction on <code>suid</code> interpreted scripts (any executable beginning with "<code>#!</code>"), some shells like <code>bash</code> as an extra safety measure will set the EUID back to the RUID in this case, you will need to use the call <code>setuid(0)</code> in the C code before executing the script.</p> <p>See the <code>man</code> pages of the <code>setuid</code>, <code>seteuid</code>, <code>getuid</code>, and <code>geteuid</code> to learn the exact semantics of the real and effective UIDs.</p> <p>(<em>WARNING</em>) Of course, this is an appropriate point to mention that the restriction on <code>suid</code> scripts in many Unix systems, shells and interpreters, are there for a reason, which is that if the script is not very careful about sanitizing its input and the state of environment when it is executed, they are dangerous and can be exploited for security escalation. So be very careful when doing this. Set the access to your script and wrapper as strict as you can, only allow this very specific script which you intend to be executed, and clear the environment within your C program before starting the script, setting environment variables such as <code>PATH</code> to contain exactly what is necessary in the right order and no directories that are writable to others.</p>
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    1. POCalling a script from a setuid root C program - script does not run as root
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    1. COIs it safer to save the original UID and reset it at the end of the program?
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    2. COIf your program does other things after the script finishes, that do not need this, then yes. If all you do is return, then it doesn't really matter. In the typical case a script wrapper will use exec and not system(...), so anyway the wrapper will not run after the script ends anymore.
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    3. CO@TomAlsberg Do you know the source code/documentation to confirm the Bash's behavior for this 'auto reset uid'?
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