- (djm) Add new UsePAM configuration directive to allow runtime control

over usage of PAM. This allows non-root use of sshd when built with
   --with-pam

ChangeLog

@@ -68,6 +68,9 @@
      implement kerberos over ssh2 ("kerberos-2@ssh.com"); tested with jakob@
      server interops with commercial client; ok jakob@ djm@
  - (djm) Make portable build with MIT krb5 (some issues remain)
+ - (djm) Add new UsePAM configuration directive to allow runtime control
+   over usage of PAM. This allows non-root use of sshd when built with
+   --with-pam
 
 20030512
  - (djm) Redhat spec: Don't install profile.d scripts when not 
@@ -1455,4 +1458,4 @@
      save auth method before monitor_reset_key_state(); bugzilla bug #284;
      ok provos@
 
-$Id: ChangeLog,v 1.2693 2003/05/14 04:31:11 djm Exp $
+$Id: ChangeLog,v 1.2694 2003/05/14 05:11:48 djm Exp $

auth-pam.c

@@ -49,6 +49,8 @@ RCSID("$FreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:
 #include "ssh2.h"
 #include "xmalloc.h"
 
+extern ServerOptions options;
+
 #define __unused
 
 #ifdef USE_POSIX_THREADS
@@ -276,7 +278,6 @@ sshpam_cleanup(void *arg)
 static int
 sshpam_init(const char *user)
 {
-	extern ServerOptions options;
 	extern u_int utmp_len;
 	const char *pam_rhost, *pam_user;
 
@@ -313,6 +314,10 @@ sshpam_init_ctx(Authctxt *authctxt)
 	struct pam_ctxt *ctxt;
 	int socks[2];
 
+	/* Refuse to start if we don't have PAM enabled */
+	if (!options.use_pam)
+		return NULL;
+
 	/* Initialize PAM */
 	if (sshpam_init(authctxt->user) == -1) {
 		error("PAM: initialization failed");

auth.c

@@ -78,8 +78,8 @@ allowed_user(struct passwd * pw)
 #ifdef WITH_AIXAUTHENTICATE
 	char *loginmsg;
 #endif /* WITH_AIXAUTHENTICATE */
-#if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \
-    !defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
+#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) && \
+    defined(HAS_SHADOW_EXPIRE)
 	struct spwd *spw;
 	time_t today;
 #endif
@@ -88,10 +88,10 @@ allowed_user(struct passwd * pw)
 	if (!pw || !pw->pw_name)
 		return 0;
 
-#if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \
-    !defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE)
+#if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) && \
+    defined(HAS_SHADOW_EXPIRE)
 #define	DAY		(24L * 60 * 60) /* 1 day in seconds */
-	if ((spw = getspnam(pw->pw_name)) != NULL) {
+	if (!options.use_pam && (spw = getspnam(pw->pw_name)) != NULL) {
 		today = time(NULL) / DAY;
 		debug3("allowed_user: today %d sp_expire %d sp_lstchg %d"
 		    " sp_max %d", (int)today, (int)spw->sp_expire,

auth1.c

@@ -342,11 +342,6 @@ do_authloop(Authctxt *authctxt)
 		    !auth_root_allowed(get_authname(type)))
 			authenticated = 0;
 #endif
-#ifdef USE_PAM
-		if (!use_privsep && authenticated && 
-		    !do_pam_account(pw->pw_name, client_user))
-			authenticated = 0;
-#endif
 
 		/* Log before sending the reply */
 		auth_log(authctxt, authenticated, get_authname(type), info);
@@ -413,7 +408,8 @@ do_authentication(void)
 	    use_privsep ? " [net]" : "");
 
 #ifdef USE_PAM
-	PRIVSEP(start_pam(user));
+	if (options.use_pam)
+		PRIVSEP(start_pam(user));
 #endif
 
 	/*

auth2.c

@@ -91,10 +91,6 @@ do_authentication2(void)
 	/* challenge-response is implemented via keyboard interactive */
 	if (options.challenge_response_authentication)
 		options.kbd_interactive_authentication = 1;
-	if (options.pam_authentication_via_kbd_int)
-		options.kbd_interactive_authentication = 1;
-	if (use_privsep)
-		options.pam_authentication_via_kbd_int = 0;
 
 	dispatch_init(&dispatch_protocol_error);
 	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
@@ -163,12 +159,14 @@ input_userauth_request(int type, u_int32_t seq, void *ctxt)
 			authctxt->valid = 1;
 			debug2("input_userauth_request: setting up authctxt for %s", user);
 #ifdef USE_PAM
-			PRIVSEP(start_pam(authctxt->pw->pw_name));
+			if (options.use_pam)
+				PRIVSEP(start_pam(authctxt->pw->pw_name));
 #endif
 		} else {
 			logit("input_userauth_request: illegal user %s", user);
 #ifdef USE_PAM
-			PRIVSEP(start_pam(user));
+			if (options.use_pam)
+				PRIVSEP(start_pam(user));
 #endif
 		}
 		setproctitle("%s%s", authctxt->pw ? user : "unknown",
@@ -215,12 +213,6 @@ userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 	    !auth_root_allowed(method))
 		authenticated = 0;
 
-#ifdef USE_PAM
-	if (!use_privsep && authenticated && authctxt->user && 
-	    !do_pam_account(authctxt->user, NULL))
-		authenticated = 0;
-#endif /* USE_PAM */
-
 #ifdef _UNICOS
 	if (authenticated && cray_access_denied(authctxt->user)) {
 		authenticated = 0;

monitor.c

@@ -567,7 +567,8 @@ mm_answer_pwnamallow(int socket, Buffer *m)
 	}
 
 #ifdef USE_PAM
-	monitor_permit(mon_dispatch, MONITOR_REQ_PAM_START, 1);
+	if (options.use_pam)
+		monitor_permit(mon_dispatch, MONITOR_REQ_PAM_START, 1);
 #endif
 
 	return (0);
@@ -750,6 +751,9 @@ mm_answer_pam_start(int socket, Buffer *m)
 {
 	char *user;
 	
+	if (!options.use_pam)
+		fatal("UsePAM not set, but ended up in %s anyway", __func__);
+
 	user = buffer_get_string(m, NULL);
 
 	start_pam(user);

monitor_wrap.c

@@ -47,6 +47,7 @@ RCSID("$OpenBSD: monitor_wrap.c,v 1.26 2003/04/07 08:29:57 markus Exp $");
 #include "atomicio.h"
 #include "monitor_fdpass.h"
 #include "getput.h"
+#include "servconf.h"
 
 #include "auth.h"
 #include "channels.h"
@@ -59,6 +60,7 @@ extern z_stream incoming_stream;
 extern z_stream outgoing_stream;
 extern struct monitor *pmonitor;
 extern Buffer input, output;
+extern ServerOptions options;
 
 void
 mm_request_send(int socket, enum monitor_reqtype type, Buffer *m)
@@ -669,6 +671,8 @@ mm_start_pam(char *user)
 	Buffer m;
 
 	debug3("%s entering", __func__);
+	if (!options.use_pam)
+		fatal("UsePAM=no, but ended up in %s anyway", __func__);
 
 	buffer_init(&m);
 	buffer_put_cstring(&m, user);

servconf.c

@@ -59,8 +59,10 @@ initialize_server_options(ServerOptions *options)
 {
 	memset(options, 0, sizeof(*options));
 
+#ifdef USE_PAM
 	/* Portable-specific options */
-	options->pam_authentication_via_kbd_int = -1;
+	options->use_pam = -1;
+#endif
 
 	/* Standard Options */
 	options->num_ports = 0;
@@ -136,8 +138,10 @@ void
 fill_default_server_options(ServerOptions *options)
 {
 	/* Portable-specific options */
-	if (options->pam_authentication_via_kbd_int == -1)
-		options->pam_authentication_via_kbd_int = 0;
+#ifdef USE_PAM
+	if (options->use_pam == -1)
+		options->use_pam = 1;
+#endif
 
 	/* Standard Options */
 	if (options->protocol == SSH_PROTO_UNKNOWN)
@@ -279,7 +283,7 @@ fill_default_server_options(ServerOptions *options)
 typedef enum {
 	sBadOption,		/* == unknown option */
 	/* Portable-specific options */
-	sPAMAuthenticationViaKbdInt,
+	sUsePAM,
 	/* Standard Options */
 	sPort, sHostKeyFile, sServerKeyBits, sLoginGraceTime, sKeyRegenerationTime,
 	sPermitRootLogin, sLogFacility, sLogLevel,
@@ -315,7 +319,7 @@ static struct {
 	ServerOpCodes opcode;
 } keywords[] = {
 	/* Portable-specific options */
-	{ "PAMAuthenticationViaKbdInt", sPAMAuthenticationViaKbdInt },
+	{ "UsePAM", sUsePAM },
 	/* Standard Options */
 	{ "port", sPort },
 	{ "hostkey", sHostKeyFile },
@@ -462,8 +466,8 @@ process_server_config_line(ServerOptions *options, char *line,
 	opcode = parse_token(arg, filename, linenum);
 	switch (opcode) {
 	/* Portable-specific options */
-	case sPAMAuthenticationViaKbdInt:
-		intptr = &options->pam_authentication_via_kbd_int;
+	case sUsePAM:
+		intptr = &options->use_pam;
 		goto parse_flag;
 
 	/* Standard Options */

servconf.h

@@ -131,7 +131,7 @@ typedef struct {
 
 	char   *authorized_keys_file;	/* File containing public keys */
 	char   *authorized_keys_file2;
-	int	pam_authentication_via_kbd_int;
+	int	use_pam;		/* Enable auth via PAM */
 }       ServerOptions;
 
 void	 initialize_server_options(ServerOptions *);

session.c

@@ -456,11 +456,13 @@ do_exec_no_pty(Session *s, const char *command)
 	session_proctitle(s);
 
 #if defined(USE_PAM)
-	do_pam_session(s->pw->pw_name, NULL);
-	do_pam_setcred(1);
-	if (is_pam_password_change_required())
-		packet_disconnect("Password change required but no "
-		    "TTY available");
+	if (options.use_pam) {
+		do_pam_session(s->pw->pw_name, NULL);
+		do_pam_setcred(1);
+		if (is_pam_password_change_required())
+			packet_disconnect("Password change required but no "
+			    "TTY available");
+	}
 #endif /* USE_PAM */
 
 	/* Fork the child. */
@@ -583,8 +585,10 @@ do_exec_pty(Session *s, const char *command)
 	ttyfd = s->ttyfd;
 
 #if defined(USE_PAM)
-	do_pam_session(s->pw->pw_name, s->tty);
-	do_pam_setcred(1);
+	if (options.use_pam) {
+		do_pam_session(s->pw->pw_name, s->tty);
+		do_pam_setcred(1);
+	}
 #endif
 
 	/* Fork the child. */
@@ -753,7 +757,7 @@ do_login(Session *s, const char *command)
 	 * If password change is needed, do it now.
 	 * This needs to occur before the ~/.hushlogin check.
 	 */
-	if (is_pam_password_change_required()) {
+	if (options.use_pam && is_pam_password_change_required()) {
 		print_pam_messages();
 		do_pam_chauthtok();
 	}
@@ -763,7 +767,7 @@ do_login(Session *s, const char *command)
 		return;
 
 #ifdef USE_PAM
-	if (!is_pam_password_change_required())
+	if (options.use_pam && !is_pam_password_change_required())
 		print_pam_messages();
 #endif /* USE_PAM */
 #ifdef WITH_AIXAUTHENTICATE
@@ -1077,10 +1081,9 @@ do_setup_env(Session *s, const char *shell)
 	 * Pull in any environment variables that may have
 	 * been set by PAM.
 	 */
-	{
-		char **p;
+	if (options.use_pam) {
+		char **p = fetch_pam_environment();
 
-		p = fetch_pam_environment();
 		copy_environment(p, &env, &envsize);
 		free_pam_environment(p);
 	}
@@ -1248,7 +1251,8 @@ do_setusercontext(struct passwd *pw)
 		 * These will have been wiped by the above initgroups() call.
 		 * Reestablish them here.
 		 */
-		do_pam_setcred(0);
+		if (options.use_pam)
+			do_pam_setcred(0);
 # endif /* USE_PAM */
 # if defined(WITH_IRIX_PROJECT) || defined(WITH_IRIX_JOBS) || defined(WITH_IRIX_ARRAY)
 		irix_setusercontext(pw);

sshd.c

@@ -1544,7 +1544,8 @@ main(int ac, char **av)
 	verbose("Closing connection to %.100s", remote_ip);
 
 #ifdef USE_PAM
-	finish_pam();
+	if (options.use_pam)
+		finish_pam();
 #endif /* USE_PAM */
 
 	packet_close();

sshd_config.5

@@ -422,12 +422,15 @@ The probability increases linearly and all connection attempts
 are refused if the number of unauthenticated connections reaches
 .Dq full
 (60).
-.It Cm PAMAuthenticationViaKbdInt
-Specifies whether PAM challenge response authentication is allowed. This
-allows the use of most PAM challenge response authentication modules, but
-it will allow password authentication regardless of whether
-.Cm PasswordAuthentication
-is enabled.
+
+.It Cm UsePAM
+Enables PAM authentication (via challenge-response) and session set up. 
+If you enable this, you should probably disable 
+.Cm PasswordAuthentication .
+If you enable 
+.CM UsePAM
+then you will not be able to run sshd as a non-root user.
+
 .It Cm PasswordAuthentication
 Specifies whether password authentication is allowed.
 The default is