Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Fix error messages containing the executed command name

Before, we took the first argument to pam_exec(8). With the addition of
options in front of the command, this could be wrong.

Now, options are parsed before calling _pam_exec() and messages contain
the proper command name.

While here, fix a warning.

Sponsored by: Yakaz (http://www.yakaz.com)

Use program exit status as pam_exec return code (optional)

pam_exec(8) now accepts a new option "return_prog_exit_status". When
set, the program exit status is used as the pam_exec return code. It
allows the program to tell why the step failed (eg. user unknown).
However, if it exits with a code not allowed by the calling PAM service
module function (see $PAM_SM_FUNC below), a warning is logged and
PAM_SERVICE_ERR is returned.

The following changes are related to this new feature but they apply no
matter if the "return_prog_exit_status" option is set or not.

The environment passed to the program is extended:
o $PAM_SM_FUNC contains the name of the PAM service module function
(eg. pam_sm_authenticate).
o All valid PAM return codes' numerical values are available
through variables named after the return code name. For instance,
$PAM_SUCCESS, $PAM_USER_UNKNOWN or $PAM_PERM_DENIED.

pam_exec return code better reflects what went on:
o If the program exits with !0, the return code is now
PAM_PERM_DENIED, not PAM_SYSTEM_ERR.
o If the program fails because of a signal (WIFSIGNALED) or doesn't
terminate normally (!WIFEXITED), the return code is now
PAM_SERVICE_ERR, not PAM_SYSTEM_ERR.
o If a syscall in pam_exec fails, the return code remains
PAM_SYSTEM_ERR.

waitpid(2) is called in a loop. If it returns because of EINTR, do it
again. Before, it would return PAM_SYSTEM_ERR without waiting for the
child to exit.

Several log messages now include the PAM service module function name.

The man page is updated accordingly.

Reviewed by: gleb@, des@
Sponsored by: Yakaz (http://www.yakaz.com)
MFC after: 2 weeks

Include <stdio.h> for asprintf().

Submitted by: Pawel Worach

childerr needs to be volatile so gcc won't optimize it away.

PR: bin/85830
MFC after: 1 week

When (re)allocating space for an array of pointers to char, use
sizeof(*list), not sizeof(**list). (i.e., sizeof(pointer) rather than
sizeof(char)).

It is possible that this buffer overflow is exploitable, but it was
added after RELENG_5 forked and hasn't been MFCed, so this will not
receive an advisory.

Submitted by: Vitezslav Novy
MFC after: 1 day

In addition to the PAM environment, export a handful of useful PAM items.

Suggested by: Ed Maste <emaste@phaedrus.sandvine.ca>

Update copyright.

Export the PAM environment to the child process instead of the "normal"
environment list, which may be unsafe and / or sensitive.

Sponsored by: DARPA, NAI Labs

Just to show that PAM can do almost anything from the ridiculous to the
obscene, or - as they say in New York - sophisticated, add pam_echo(8) and
pam_exec(8) to our ever-lengthening roster of PAM modules.

Sponsored by: DARPA, NAI Labs.