Re: [Nmh-workers] proposed patch for shell metacharacter failure in nmh-1.7

[Paul Vixie]

i do not think that we can ask for the shell's help with metacharacter 
expansion, because even on unix, the syntax it understands may not be 
what the user expects.

because i call sendmail from popen() in cron, i had this problem with 
MAILTO= values. i first decided to accept only @, %, ::, and %. but then 
people with strange login shells or strange non-posix /bin/sh 
implementations reported trouble. now i allow isalnum() only, and if 
they want something else, they can put it in /etc/aliases or whatever.

for MH we should allow only metacharacters we handle explicitly, and we 
should use strsep() rather than /bin/sh to make our argument vectors, 
and we should call execve() rather than popen().

in other words, the reason this is hard to do, is that it's a bad idea.

vixie