Add the "SITE MD5 filename" facility.

This allows you to determine if the file on the other side is the same
as the one you have without transferring the entire file to compare.

Needless to say, if the server end lies to you this check doesn't work,
but on the other hand, if it lies to you about the files checksum,
what can you trust from it ?

libexec/ftpd/ftpcmd.y

@@ -69,6 +69,7 @@ static const char rcsid[] =
 #include <time.h>
 #include <unistd.h>
 #include <libutil.h>
+#include <md5.h>
 
 #include "extern.h"
 
@@ -126,7 +127,7 @@ extern int epsvall;
 	CDUP	STOU	SMNT	SYST	SIZE	MDTM
 	LPRT	LPSV	EPRT	EPSV
 
-	UMASK	IDLE	CHMOD
+	UMASK	IDLE	CHMOD	MDFIVE
 
 	LEXERR
 
@@ -586,6 +587,18 @@ cmd
 		{
 			help(sitetab, $5);
 		}
+	| SITE SP MDFIVE check_login SP pathname CRLF
+		{
+			char p[64], *q;
+
+			if ($4) {
+				q = MD5File($6, p);
+				if (q != NULL)
+					reply(200, "MD5(%s) = %s", $6, p);
+				else
+					perror_reply(550, $6);
+			}
+		}
 	| SITE SP UMASK check_login CRLF
 		{
 			int oldmask;
@@ -1084,6 +1097,7 @@ struct tab cmdtab[] = {		/* In order defined in RFC 765 */
 };
 
 struct tab sitetab[] = {
+	{ "MD5", MDFIVE, STR1, 1,	"[ <sp> file-name ]" },
 	{ "UMASK", UMASK, ARGS, 1,	"[ <sp> umask ]" },
 	{ "IDLE", IDLE, ARGS, 1,	"[ <sp> maximum-idle-time ]" },
 	{ "CHMOD", CHMOD, NSTR, 1,	"<sp> mode <sp> file-name" },

libexec/ftpd/ftpd.8

@@ -247,6 +247,7 @@ SITE request.
 .It UMASK Ta change umask, e.g. ``SITE UMASK 002''
 .It IDLE Ta set idle-timer, e.g. ``SITE IDLE 60''
 .It CHMOD Ta "change mode of a file [RW], e.g. ``SITE CHMOD 755 filename''"
+.It MD5 Ta "report the files MD5 checksum, e.g. ``SITE MD5 filename''"
 .It HELP Ta give help information
 .El
 .Pp