The var is looked up to see whether it is already a part of the delivery agent??™s environment.
If it is, it is redefined to be the new value. If it is not, it is added to that list
of variables. If that addition will cause the list to exceed MAXUSERENVIRON variables
(currently defined as 100 in conf.h, ?§3.4.22 on page 120), the definition is
silently ignored.
Whether or not the var was added to, or updated in, the delivery agent??™s environment,
it is always added or updated to sendmail??™s environment with putenv(2). If this
call fails, sendmail logs and prints the following message:
setuserenv: putenv(var=value) failed
Only one var can be defined per E command. Additional environment variables
require multiple E commands. Each E command affects all delivery agents. There is
no way to tune the environment on a per-delivery-agent basis.
4.3 SMTP Probes
Although SMTP probes can be legitimate uses of the network, they can also pose
potential risks. They are sometimes used to see whether a bug remains unfixed.
Sometimes they are used to try to gather user login names or to feed a program unexpected
input in such a way that it breaks and gives away root privilege.
4.3.1 SMTP Debug
An ???unfixed bug??? probe can use the SMTP debug and showq commands. The SMTP
debug command allows the local sendmail to be placed into debugging mode (as with
the -d command-line switch, ?§15.
Pages:
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307