INTERVIEW QUESTIONS PROGRAMMING LANGUAGES CGI PROGRAMMING DETAILS

Question: How can I stop my CGI script reading and writing files as "nobody"?

Answer: CGI scripts are run by the HTTPD, and therefore by the UID of the HTTPD
process, which is (by convention) usually a special user "nobody".

There are two basic ways to run a script under your own userid:
(1) The direct approach: use a setuid program.
(2) The double-server approach: have your CGI script communicate
with a second process (e.g. a daemon) running under your userid,
which is responsible for the actual file management.

The direct approach is usually faster, but the client-server architecture
may help with other problems, such as maintaining integrity of a database.

When running a compiled CGI program (e.g. C, C++), you can make it
setuid by simply setting the setuid bit:
e.g. "chmod 4755 myprog.cgi"

For security reasons, this is not possible with scripting languages
(eg Perl, Tcl, shell). A workaround is to run them from a setuid
program, such as cgiwrap.

In most cases where you'd want to use the client-server approach,
the server is a finished product (such as an SQL server) with its
own CGI interface.
A lightweight alternative to this is Don Libes' "expect" package.

CGI scripts are run by the HTTPD, and therefore by the UID of the HTTPD
process, which is (by convention) usually a special user "nobody".

There are two basic ways to run a script under your own userid:
(1) The direct approach: use a setuid program.
(2) The double-server approach: have your CGI script communicate
with a second process (e.g. a daemon) running under your userid,
which is responsible for the actual file management.

The direct approach is usually faster, but the client-server architecture
may help with other problems, such as maintaining integrity of a database.

When running a compiled CGI program (e.g. C, C++), you can make it
setuid by simply setting the setuid bit:
e.g. "chmod 4755 myprog.cgi"

For security reasons, this is not possible with scripting languages
(eg Perl, Tcl, shell). A workaround is to run them from a setuid
program, such as cgiwrap.

In most cases where you'd want to use the client-server approach,
the server is a finished product (such as an SQL server) with its
own CGI interface.
A lightweight alternative to this is Don Libes' "expect" package.
Source: CoolInterview.com

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