docs/166497: crypt(3) man page incorrectly documents modular crypt numbers for SHA256, SHA512

[Mike Kelly]

>Number:         166497
>Category:       docs
>Synopsis:       crypt(3) man page incorrectly documents modular crypt numbers for SHA256, SHA512
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-doc
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          doc-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Mar 29 17:40:13 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Mike Kelly
>Release:        9.0-RELEASE
>Organization:
>Environment:
FreeBSD nas.home.pioto.org 9.0-RELEASE FreeBSD 9.0-RELEASE #5: Tue Jan 17 00:17:39 EST 2012     root at nas.home.pioto.org:/usr/obj/usr/src/sys/NAS  i386

>Description:
The man page, as currently written, seems to imply that FreeBSD uses $4$ for SHA-256, and $5$ for SHA-512. The section in question currently renders as:

     Currently supported algorithms are:

           1.   MD5
           2.   Blowfish
           3.   NT-Hash
           4.   SHA-256
           5.   SHA-512

That would be different from what Linux uses, and would be a point of potential confusion. That isn't the case, however; the code confirms that things match up with Linux:

  lib/libcrypt/crypt-sha256.c:48:static const char sha256_salt_prefix[] = "$5$";
  lib/libcrypt/crypt-sha512.c:48:static const char sha512_salt_prefix[] = "$6$";

So, rather than using what seems to be an auto-numbering formatting in the man page, things should be enumerated explicitly. Or, maybe, some placeholder like "RESERVED" or "UNUSED" should be put into the fourth spot in the list.
>How-To-Repeat:
$ man 3 crypt
>Fix:
diff --git a/lib/libcrypt/crypt.3 b/lib/libcrypt/crypt.3
index d3f89e2..724d482 100644
--- a/lib/libcrypt/crypt.3
+++ b/lib/libcrypt/crypt.3
@@ -189,6 +189,8 @@ Blowfish
 .It
 NT-Hash
 .It
+(Reserved for future use)
+.It
 SHA-256
 .It
 SHA-512


>Release-Note:
>Audit-Trail:
>Unformatted: