More funny code from fetchmail

Posted by Nico Golde in
Thursday, March 29. 2007

Another nice piece of code made by ESR you know, the guy who writes books about "The art of UNIX programming" for example

From sink.c:

if (strcmp(ctl->bsmtp, "-") == 0)
sinkfp = stdout;
else
sinkfp = fopen(ctl->bsmtp, "a");
/* see the ap computation under the SMTP branch */
need_anglebrs = (msg->return_path[0] != '<');
fprintf(sinkfp,
"MAIL FROM:%s%s%s",
need_anglebrs ? "<" : "",
(msg->return_path[0]) ? msg->return_path : user,
need_anglebrs ? ">" : "");
/* DO SOME UNIMPORTANT STUFF HERE aka ...... CODE STRIPPED */
fputs("DATA\r\n", sinkfp);
if (ferror(sinkfp))
{
report(stderr, GT_("BSMTP file open or preamble write failed\n"));
return(PS_BSMTP);
}

This code will segfault if the fopen call in line 4 fails, sinkfp will become NULL then which leads
to a segfault when writing more than once into it with fprintf/fputs.

What I find funny now is the check in line 17 to test the error indicator for the stream pointed to by sinkfp AFTER actually writing into it.
But what is even more funny is that also the check would segfault in this case since ferror will if it gets a NULL pointer.

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Well, now you know why he wrote "The Art of Unix Programming" and not "The Art of Software Security Assessment".

#1 ak (Homepage) on 2007-03-29 16:53 (Reply)

I want to correct: esr didn't wrote TAOCP but "The cathedral and the basaar". Donald E. Knuth wrote TAOCP.

#2 Meillo (Homepage) on 2007-04-03 13:35 (Reply)

okay, I should allways read every single word.

or in other words: UNIX != Computer

#2.1 Meillo on 2007-04-03 13:44 (Reply)

? ak wrote: "why he wrote "The Art of Unix Programming" and NOT "The Art of Software Security Assessment"

looks like you didn't understand it?

#3 nion on 2007-04-03 13:41 (Reply)

lol

#4 nion on 2007-04-03 14:04 (Reply)

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