diff -r -u popa3d-0.4/Makefile popa3d-0.4-apop/Makefile
--- popa3d-0.4/Makefile	Mon Jan 31 22:56:46 2000
+++ popa3d-0.4-apop/Makefile	Thu May 25 20:12:37 2000
@@ -12,6 +12,11 @@
 	protocol.o database.o mailbox.o \
 	misc.o
 
+all: popauth popa3d
+
+popauth: popauth.o
+	$(LD) $(LDFLAGS) -o $@ popauth.o
+
 popa3d: $(OBJS)
 	$(LD) $(LDFLAGS) $(OBJS) -o popa3d
 
@@ -22,4 +27,4 @@
 	$(CC) $(CFLAGS) $*.c
 
 clean:
-	$(RM) $(PROJ) $(OBJS)
+	$(RM) $(PROJ) $(OBJS) *.o popauth *~
diff -r -u popa3d-0.4/params.h popa3d-0.4-apop/params.h
--- popa3d-0.4/params.h	Tue Feb  1 01:16:24 2000
+++ popa3d-0.4-apop/params.h	Sat May 27 03:37:36 2000
@@ -65,6 +65,12 @@
 #define AUTH_SHADOW			1
 
 /*
+ * RFC 1460 APOP authentication support by Dug Song <dugsong@monkey.org>
+ */
+#define AUTH_APOP			1
+#define POP_AUTH_DB			"/etc/pop.auth"
+
+/*
  * A salt used to waste some CPU time on dummy crypt(3) calls and make
  * it harder (but still far from impossible, on most systems) to check
  * for valid usernames. Adjust it for your crypt(3).
diff -r -u popa3d-0.4/pop_auth.c popa3d-0.4-apop/pop_auth.c
--- popa3d-0.4/pop_auth.c	Wed Mar 24 23:25:55 1999
+++ popa3d-0.4-apop/pop_auth.c	Sat May 27 01:36:12 2000
@@ -20,6 +20,20 @@
 	return POP_LEAVE;
 }
 
+#if AUTH_APOP
+static int pop_auth_apop(char *params)
+{
+	char *user, *pass;
+
+	user = pop_get_param(&params);
+	if (!user || pop_user) return POP_ERROR;
+	pass = pop_get_param(&params);
+	if (!pass || pop_pass) return POP_ERROR;
+	if (!(pop_user = strdup(user)) || !(pop_pass = strdup(pass)))
+		return POP_CRASH;
+	return POP_STATE;
+}
+#else
 static int pop_auth_user(char *params)
 {
 	char *user;
@@ -36,23 +50,42 @@
 	if (!(pop_pass = strdup(params))) return POP_CRASH;
 	return POP_STATE;
 }
+#endif /* AUTH_APOP */
 
 static struct pop_command pop_auth_commands[] = {
 	{"QUIT", pop_auth_quit},
+#if AUTH_APOP
+	{"APOP", pop_auth_apop},
+#else
 	{"USER", pop_auth_user},
 	{"PASS", pop_auth_pass},
+#endif
 	{NULL}
 };
 
 int do_pop_auth(int channel)
 {
+#if AUTH_APOP
+	char challenge[512], hostname[512];
+
+	if (gethostname(hostname, sizeof(hostname))) return 1;
+#endif	
 	pop_init();
 
+#if AUTH_APOP
+	snprintf(challenge, sizeof(challenge), "<%d.%d@%s>",
+		 getpid(), time(NULL), hostname);
+	
+	if (pop_reply("+OK %s", challenge)) return 1;
+#else
 	if (pop_reply_ok()) return 1;
-
+#endif
 	pop_user = NULL;
 	if (pop_handle_state(pop_auth_commands) == POP_STATE) {
 		write_loop(channel, (char *)&pop_buffer, sizeof(pop_buffer));
+#if AUTH_APOP
+		write_loop(channel, challenge, strlen(challenge) + 1);
+#endif
 		write_loop(channel, pop_user, strlen(pop_user) + 1);
 		write_loop(channel, pop_pass, strlen(pop_pass) + 1);
 		if (close(channel)) return 1;
diff -r -u popa3d-0.4/pop_root.c popa3d-0.4-apop/pop_root.c
--- popa3d-0.4/pop_root.c	Tue Feb  1 01:18:12 2000
+++ popa3d-0.4-apop/pop_root.c	Sat May 27 03:36:00 2000
@@ -21,13 +21,32 @@
 #include "pop_auth.h"
 #include "pop_trans.h"
 
-#if AUTH_SHADOW
+#if AUTH_APOP
+#include <fcntl.h>
+#include <md5.h>
+#if GDBM
+# include <gdbm.h>
+#else
+# include <ndbm.h>
+#endif
+#elif AUTH_SHADOW
 #include <shadow.h>
 #ifdef __GLIBC__
 #include <crypt.h>
 #endif
 #endif
 
+/* *DBM compatibility nonsense. */
+#if GDBM
+#define DBM			GDBM_FILE
+#define F_RDONLY		GDBM_READER
+#define dbm_open(x, y, z)	gdbm_open(x, 512, y, z, 0)
+#define dbm_fetch		gdbm_fetch
+#define dbm_close		gdbm_close
+#else
+#define F_RDONLY		O_RDONLY
+#endif
+
 static struct passwd pop_pw;
 static char *mailbox;
 
@@ -73,7 +92,51 @@
 	return offset;
 }
 
-#if AUTH_SHADOW
+#if AUTH_APOP
+/*
+ * RFC 1460 APOP authentication routine.
+ */
+static struct passwd *do_apop_auth(char *user, char *pass, char *challenge)
+{
+	struct passwd *pw;
+	DB *db;
+	datum key, value;
+	MD5_CTX ctx;
+	char hash[33];
+	int i;
+	
+	pw = getpwnam(user);
+	endpwent();
+	
+	if (!pw) return (NULL);
+	memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
+	mailbox = user;
+	
+	if ((db = dbm_open(POP_AUTH_DB, F_RDONLY, 0)) == NULL)
+		return NULL;
+	
+	key.dptr = user;
+	key.dsize = strlen(user) + 1;
+	value = dbm_fetch(db, key);
+	
+	if (value.dptr == NULL) {
+		dbm_close(db);
+		return NULL;
+	}
+	for (i = 0; i < value.dsize - 1; i++)
+		value.dptr[i] ^= 0xff;
+
+	MD5Init(&ctx);
+	MD5Update(&ctx, challenge, strlen(challenge));
+	MD5Update(&ctx, value.dptr, strlen(value.dptr));
+	MD5End(&ctx, hash);
+	dbm_close(db);
+	
+	if (strcmp(pass, hash)) pw = NULL;
+	
+	return (pw);
+}
+#elif AUTH_SHADOW
 /*
  * The /etc/shadow authentication routine. This one is really tricky,
  * in order to make sure we don't have an /etc/shadow fd or sensitive
@@ -162,6 +225,9 @@
 static int do_root_auth(int channel)
 {
 	static char auth[AUTH_BUFFER_SIZE + 2];
+#if AUTH_APOP
+	char *challenge;
+#endif
 	char *user, *pass;
 	struct passwd *pw;
 
@@ -176,11 +242,17 @@
 /* Now, the authentication data. */
 	memset(auth, 0, sizeof(auth));	/* Ensure the NUL termination */
 	if (read_loop(channel, auth, AUTH_BUFFER_SIZE) < 0) return AUTH_NONE;
-
+#if AUTH_APOP
+	challenge = auth;
+	user = &challenge[strlen(challenge) + 1];
+#else
 	user = auth;
+#endif
 	pass = &user[strlen(user) + 1];
 
-#if AUTH_SHADOW
+#if AUTH_APOP
+	if (!(pw = do_apop_auth(user, pass, challenge))) return AUTH_FAILED;
+#elif AUTH_SHADOW
 	if (!(pw = do_shadow_auth(user, pass))) return AUTH_FAILED;
 #else
 	if (!(pw = do_passwd_auth(user, pass))) return AUTH_FAILED;
diff -r -u popa3d-0.4/popauth.8 popa3d-0.4-apop/popauth.8
--- popa3d-0.4/popauth.8	Sat May 27 01:39:31 2000
+++ popa3d-0.4-apop/popauth.8	Sat May 27 01:38:40 2000
@@ -0,0 +1,34 @@
+.TH POPAUTH 8
+.ad
+.fi
+.SH NAME
+popauth
+\-
+manipulate POP authentication DB
+.SH SYNOPSIS
+.na
+.nf
+.fi
+\fBpopauth\fR [\fB-d\fR|\fB-l\fR] [\fIuser\fR]
+.SH DESCRIPTION
+.ad
+.fi
+\fBpopauth\fR allows a user to change their POP password. In
+addition, the superuser may use this program to either add or remove a
+user's entry, or to print public information from it.
+.LP
+Under normal usage, \fBpopauth\fR will prompt to change the user's
+password, like passwd(8).
+.SH OPTIONS
+.IP \fB-l\fR
+List the entry for the user, or for all users.
+.IP \fB-d\fR
+Delete the entry for the user, or for all users.
+.SH FILES
+\fI/etc/pop.auth.*\fR	POP authentication DB
+.SH "SEE ALSO"
+passwd(8), popa3d(8)
+.SH AUTHOR
+.na
+.nf
+Dug Song <dugsong@monkey.org>
diff -r -u popa3d-0.4/popauth.c popa3d-0.4-apop/popauth.c
--- popa3d-0.4/popauth.c	Sat May 27 01:39:31 2000
+++ popa3d-0.4-apop/popauth.c	Sat May 27 02:36:19 2000
@@ -0,0 +1,307 @@
+/*
+  popauth.c
+
+  qpopper-compatible APOP password utility for Solar Designer's popa3d.
+
+  Copyright (c) 2000 Dug Song <dugsong@monkey.org>
+  All rights reserved, all wrongs reversed.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
+
+  1. Redistributions of source code must retain the above copyright
+     notice, this list of conditions and the following disclaimer.
+  2. Redistributions in binary form must reproduce the above copyright
+     notice, this list of conditions and the following disclaimer in the
+     documentation and/or other materials provided with the distribution.
+  3. The name of author may not be used to endorse or promote products
+     derived from this software without specific prior written permission.
+
+  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
+  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+  AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+  THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+  OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <pwd.h>
+#include <grp.h>
+#if GDBM
+# include <gdbm.h>
+#else
+# include <ndbm.h>
+#endif
+
+#include "params.h"
+
+/* *DBM compatibility nonsense. */
+#if GDBM
+#define DBM			GDBM_FILE
+#define F_WRCREAT		GDBM_WRCREAT
+#define F_RDONLY		GDBM_READER
+#define F_RDWR			GDBM_WRITER
+#define F_WRTRUNC		GDBM_NEWDB
+#define dbm_open(x, y, z)	gdbm_open(x, 512, y, z, 0)
+#define dbm_firstkey		gdbm_firstkey
+#define dbm_fetch		gdbm_fetch
+#define dbm_delete		gdbm_delete
+#define dbm_close		gdbm_close
+#else
+#define F_WRCREAT		O_RDWR|O_CREAT
+#define F_RDONLY		O_RDONLY
+#define F_RDWR			O_RDWR
+#define F_WRTRUNC		O_RDWR|O_TRUNC
+#endif
+
+int	Opt_delete = 0;
+int	Opt_list = 0;
+
+struct passwd *pw;
+
+void
+usage(void)
+{
+	fprintf(stderr, "Usage: popauth [-d|-l] [user]\n");
+	exit(1);
+}
+
+int
+check_privs(char *user)
+{
+	if ((pw = getpwuid(getuid())) == NULL) {
+		perror("getpwuid");
+		return (0);
+	}	
+	if (pw->pw_uid != 0) {
+		if (user == NULL) {
+			if (Opt_delete || Opt_list)
+				return (0);
+		}
+		else if (strcmp(user, pw->pw_name) != 0)
+			return (0);
+	}
+	return (1);
+}
+
+void
+revoke_privs(void)
+{
+	gid_t groups[2];
+	
+	if (!pw->pw_uid) return;
+	
+	groups[0] = groups[1] = pw->pw_gid;
+
+	if (setgroups(1, groups)) {
+		perror("setgroups");
+		exit(1);
+	}
+	if (setgid(pw->pw_gid)) {
+		perror("setgid");
+		exit(1);
+	}
+	if (setuid(pw->pw_uid)) {
+		perror("setuid");
+		exit(1);
+	}
+}
+
+int
+popauth_modify(char *user)
+{
+	DB *db;
+	datum key, value;
+	char *p, pass[128];
+	
+	if (user == NULL) {
+		user = pw->pw_name;
+	}
+	if ((db = dbm_open(POP_AUTH_DB, F_WRCREAT, S_IRUSR|S_IWUSR)) == NULL) {
+		perror("dbm_open");
+		return (1);
+	}
+	revoke_privs();
+	
+	key.dptr = user;
+	key.dsize = strlen(user) + 1;
+
+	printf("Changing POP password for %s\n", user);
+
+	for (;;) {
+		p = getpass("New password:");
+		if (*p == '\0') break;
+		
+		if (strlen(p) < 6) {
+			printf("Please enter a longer password.\n");
+			continue;
+		}
+		strncpy(pass, p, sizeof(pass) - 1);
+		pass[sizeof(pass) - 1] = '\0';
+		
+		p = getpass("Retype new password:");
+		if (strcmp(pass, p) == 0) break;
+		
+		printf("Passwords don't match, try again.\n");
+	}
+	if (*pass != '\0') {
+		for (p = pass; *p != '\0'; p++)
+			*p ^= 0xff;
+		
+		value.dptr = pass;
+		value.dsize = strlen(pass) + 1;
+		
+		if (dbm_store(db, key, value, DBM_REPLACE) != 0) {
+			fprintf(stderr, "dbm_store: database corrupt?\n");
+			dbm_close(db);
+			return (1);
+		}
+	}
+	else printf("Password unchanged.\n");
+	
+	dbm_close(db);
+	return (0);
+}
+
+int
+popauth_list(char *user)
+{	
+	DB *db;
+	datum key, value;
+
+	if ((db = dbm_open(POP_AUTH_DB, F_RDONLY, 0)) == NULL) {
+		perror("dbm_open");
+		return (1);
+	}
+	revoke_privs();
+	
+	if (user != NULL) {
+		key.dptr = user;
+		key.dsize = strlen(user) + 1;
+
+		value = dbm_fetch(db, key);
+
+		if (value.dptr == NULL) {
+			dbm_close(db);
+			return (1);
+		}
+		printf("%-16s: APOP\n", user);
+	}
+	else {
+		for (key = dbm_firstkey(db); key.dptr != NULL;
+		     key = dbm_nextkey(db)) {
+			value = dbm_fetch(db, key);
+
+			if (value.dptr != NULL)
+				printf("%-16s: APOP\n", key.dptr);
+		}
+	}
+	dbm_close(db);
+	return (0);
+}
+
+int
+popauth_delete(char *user)
+{
+	DB *db;
+	datum key, value;
+	char buf[32];
+	
+	if (user != NULL) {
+		if ((db = dbm_open(POP_AUTH_DB, F_RDWR, 0)) == NULL) {
+			perror("dbm_open");
+			return (1);
+		}
+		revoke_privs();
+		
+		key.dptr = user;
+		key.dsize = strlen(user) + 1;
+
+		value = dbm_fetch(db, key);
+
+		if (value.dptr == NULL) {
+			printf("Unknown user %s.\n", user);
+			dbm_close(db);
+			return (1);
+		}
+		if (dbm_delete(db, key) < 0) {
+			fprintf(stderr, "dbm_delete: unable to delete "
+				"user %s\n", user);
+			dbm_close(db);
+			return (1);
+		}
+	}
+	else {
+		printf("Delete all POP authentication entries? ");
+		
+		if (fgets(buf, sizeof(buf), stdin) == NULL || *buf != 'y')
+			return (1);
+		
+		if ((db = dbm_open(POP_AUTH_DB, F_WRTRUNC, 0)) == NULL) {
+			perror("dbm_open");
+			return (1);
+		}
+	}
+	dbm_close(db);
+	return (0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	char *user;
+	int c;
+
+	user = NULL;
+	
+	while ((c = getopt(argc, argv, "dlh")) != -1) {
+		switch (c) {
+		case 'd':
+			Opt_delete = 1;
+			break;
+		case 'l':
+			Opt_list = 1;
+			break;
+		case '?':
+		default:
+			usage();
+			break;
+		}
+	}
+	argc -= optind;
+	argv += optind;
+
+	if (argc == 1)
+		user = argv[0];
+	else if (argc > 1)
+		usage();
+
+	if (Opt_delete && Opt_list)
+		usage();
+	
+	if (!check_privs(user)) {
+		printf("Permission denied.\n");
+		return (1);
+	}
+	if (Opt_delete) {
+		return (popauth_delete(user));
+	}
+	else if (Opt_list) {
+		return (popauth_list(user));
+	}
+	return (popauth_modify(user));
+}
+
+/* 5000. */