- (djm) Added patch from Nalin Dahyabhai <nalin@redhat.com> to enable

PAM authentication using KbdInteractive.
 - (djm) Added another TODO

ChangeLog

@@ -29,6 +29,9 @@
     [sshd.c]
     sshd -D, startup w/o deamon(), for monitoring scripts or inittab;
     from handler@sub-rosa.com and eric@urbanrange.com; ok niels@
+ - (djm) Added patch from Nalin Dahyabhai <nalin@redhat.com> to enable
+   PAM authentication using KbdInteractive.
+ - (djm) Added another TODO
 
 20001202
  - (bal) Backed out of part of Alain St-Denis' loginrec.c patch.

Makefile.in

@@ -42,7 +42,7 @@ LIBOPENBSD_COMPAT_OBJS=bsd-arc4random.o bsd-base64.o bsd-bindresvport.o bsd-daem
 
 SSHOBJS= ssh.o sshconnect.o sshconnect1.o sshconnect2.o log-client.o readconf.o clientloop.o
 
-SSHDOBJS= sshd.o auth.o auth1.o auth2.o auth-skey.o auth2-skey.o auth-rhosts.o auth-options.o auth-krb4.o auth-pam.o auth-passwd.o auth-rsa.o auth-rh-rsa.o dh.o pty.o log-server.o login.o loginrec.o servconf.o serverloop.o md5crypt.o session.o
+SSHDOBJS= sshd.o auth.o auth1.o auth2.o auth-skey.o auth2-skey.o auth-rhosts.o auth-options.o auth-krb4.o auth-pam.o auth2-pam.o auth-passwd.o auth-rsa.o auth-rh-rsa.o dh.o pty.o log-server.o login.o loginrec.o servconf.o serverloop.o md5crypt.o session.o
 
 TROFFMAN	= scp.1 ssh-add.1 ssh-agent.1 ssh-keygen.1 ssh.1 sshd.8 sftp-server.8
 CATMAN		= scp.0 ssh-add.0 ssh-agent.0 ssh-keygen.0 ssh.0 sshd.0 sftp-server.0

TODO

@@ -19,6 +19,8 @@ Programming:
   select() under Linux is not as nice as others, and two the children
   of the shell are not killed on exiting the shell.
 
+- Build an automated test suite
+
 Documentation:
 - More and better
 

auth-pam.c

@@ -29,7 +29,7 @@
 #include "xmalloc.h"
 #include "servconf.h"
 
-RCSID("$Id: auth-pam.c,v 1.18 2000/10/14 15:08:49 stevesk Exp $");
+RCSID("$Id: auth-pam.c,v 1.19 2000/12/03 00:51:51 djm Exp $");
 
 #define NEW_AUTHTOK_MSG \
 	"Warning: Your password has expired, please change it now"
@@ -50,10 +50,26 @@ static const char *pampasswd = NULL;
 static char *pam_msg = NULL;
 
 /* states for pamconv() */
-typedef enum { INITIAL_LOGIN, OTHER } pamstates;
-static pamstates pamstate = INITIAL_LOGIN;
+enum { INITIAL_LOGIN, OTHER } pamstate = INITIAL_LOGIN;
 /* remember whether pam_acct_mgmt() returned PAM_NEWAUTHTOK_REQD */
 static int password_change_required = 0;
+/* remember whether the last pam_authenticate() succeeded or not */
+static int was_authenticated = 0;
+
+/* accessor which allows us to switch conversation structs according to
+ * the authentication method being used */
+void pam_set_conv(struct pam_conv *conv)
+{
+	pam_set_item(pamh, PAM_CONV, conv);
+}
+
+/* start an authentication run */
+int do_pam_authenticate(int flags)
+{
+	int retval = pam_authenticate(pamh, flags);
+	was_authenticated = (retval == PAM_SUCCESS);
+	return retval;
+}
 
 /*
  * PAM conversation function.
@@ -163,6 +179,8 @@ int auth_pam_password(struct passwd *pw, const char *password)
 	extern ServerOptions options;
 	int pam_retval;
 
+	pam_set_conv(&conv);
+
 	/* deny if no user. */
 	if (pw == NULL)
 		return 0;
@@ -174,7 +192,7 @@ int auth_pam_password(struct passwd *pw, const char *password)
 	pampasswd = password;
 	
 	pamstate = INITIAL_LOGIN;
-	pam_retval = pam_authenticate(pamh, 0);
+	pam_retval = do_pam_authenticate(0);
 	if (pam_retval == PAM_SUCCESS) {
 		debug("PAM Password authentication accepted for user \"%.100s\"", 
 			pw->pw_name);
@@ -256,8 +274,13 @@ void do_pam_setcred(void)
 	debug("PAM establishing creds");
 	pam_retval = pam_setcred(pamh, PAM_ESTABLISH_CRED);
 	if (pam_retval != PAM_SUCCESS) {
-		fatal("PAM setcred failed[%d]: %.200s", 
-			pam_retval, PAM_STRERROR(pamh, pam_retval));
+		if(was_authenticated) {
+			fatal("PAM setcred failed[%d]: %.200s", 
+				pam_retval, PAM_STRERROR(pamh, pam_retval));
+		} else {
+			debug("PAM setcred failed[%d]: %.200s", 
+				pam_retval, PAM_STRERROR(pamh, pam_retval));
+		}
 	}
 }
 

auth-pam.h

@@ -7,11 +7,13 @@ void start_pam(struct passwd *pw);
 void finish_pam(void);
 int auth_pam_password(struct passwd *pw, const char *password);
 char **fetch_pam_environment(void);
+int do_pam_authenticate(int flags);
 int do_pam_account(char *username, char *remote_user);
 void do_pam_session(char *username, const char *ttyname);
 void do_pam_setcred(void);
 void print_pam_messages(void);
 int pam_password_change_required(void);
 void do_pam_chauthtok(void);
+void pam_set_conv(struct pam_conv *);
 
 #endif /* USE_PAM */

auth.h

@@ -34,6 +34,9 @@ struct Authctxt {
 	struct passwd *pw;
 };
 
+#include "auth-pam.h"
+#include "auth2-pam.h"
+
 void	do_authentication(void);
 void	do_authentication2(void);
 

auth2-pam.c

@@ -0,0 +1,170 @@
+#include "includes.h"
+RCSID("$Id: auth2-pam.c,v 1.1 2000/12/03 00:51:51 djm Exp $");
+
+#ifdef USE_PAM
+#include "ssh.h"
+#include "ssh2.h"
+#include "auth.h"
+#include "packet.h"
+#include "xmalloc.h"
+#include "dispatch.h"
+#include <security/pam_appl.h>
+
+struct {
+	int finished, num_received, num_expected;
+	int *prompts;
+	struct pam_response *responses;
+} context_pam2 = {0, 0, 0, NULL};
+
+static int do_conversation2(int num_msg, const struct pam_message **msg,
+			    struct pam_response **resp, void *appdata_ptr);
+
+static struct pam_conv
+conv2 = {
+	do_conversation2,
+	NULL,
+};
+
+void input_userauth_info_response_pam(int type, int plen, void *ctxt);
+
+int
+auth2_pam(Authctxt *authctxt)
+{
+	int retval = -1;
+	char *method = "PAM";
+
+	if (authctxt->user == NULL)
+		fatal("auth2_pam: internal error: no user");
+
+	if (authctxt->valid) {
+		conv2.appdata_ptr = authctxt;
+		pam_set_conv(&conv2);
+	}
+
+	dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
+		     &input_userauth_info_response_pam);
+	retval = (do_pam_authenticate(0) == PAM_SUCCESS);
+	dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
+
+	userauth_log(authctxt, retval, method);
+
+	return retval;
+}
+
+static int
+do_conversation2(int num_msg, const struct pam_message **msg,
+		 struct pam_response **resp, void *appdata_ptr)
+{
+	int echo = 0, i = 0, j = 0, done = 0;
+	char *tmp = NULL, *text = NULL;
+
+	context_pam2.finished = 0;
+	context_pam2.num_received = 0;
+	context_pam2.num_expected = 0;
+	context_pam2.prompts = xmalloc(sizeof(int) * num_msg);
+	context_pam2.responses = xmalloc(sizeof(struct pam_response) * num_msg);
+	memset(context_pam2.responses, 0, sizeof(struct pam_response) * num_msg);
+
+	packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
+	packet_put_cstring("");				/* Name */
+	packet_put_cstring("");				/* Instructions */
+	packet_put_cstring("");				/* Language */
+	for (i = 0, j = 0; i < num_msg; i++) {
+		if(((*msg)[i].msg_style == PAM_PROMPT_ECHO_ON) ||
+		   ((*msg)[i].msg_style == PAM_PROMPT_ECHO_OFF) ||
+		   (i == num_msg - 1)) {
+			j++;
+		}
+	}
+	packet_put_int(j);				/* Number of prompts. */
+	context_pam2.num_expected = j;
+	for (i = 0, j = 0; i < num_msg; i++) {
+		switch((*msg)[i].msg_style) {
+			case PAM_PROMPT_ECHO_ON:
+				echo = 1;
+				break;
+			case PAM_PROMPT_ECHO_OFF:
+				echo = 0;
+				break;
+			default:
+				echo = 0;
+				break;
+		}
+		if(text) {
+			tmp = xmalloc(strlen(text) + strlen((*msg)[i].msg) + 2);
+			strcpy(tmp, text);
+			strcat(tmp, "\n");
+			strcat(tmp, (*msg)[i].msg);
+			xfree(text);
+			text = tmp;
+			tmp = NULL;
+		} else {
+			text = xstrdup((*msg)[i].msg);
+		}
+		if(((*msg)[i].msg_style == PAM_PROMPT_ECHO_ON) ||
+		   ((*msg)[i].msg_style == PAM_PROMPT_ECHO_OFF) ||
+		   (i == num_msg - 1)) {
+			debug("sending prompt ssh-%d(pam-%d) = \"%s\"",
+			      j, i, text);
+			context_pam2.prompts[j++] = i;
+			packet_put_cstring(text);
+			packet_put_char(echo);
+			xfree(text);
+			text = NULL;
+		}
+	}
+	packet_send();
+	packet_write_wait();
+
+	/* Grabbing control of execution and spinning until we get what
+	 * we want is probably rude, but it seems to work properly, and
+	 * the client *should* be in lock-step with us, so the loop should
+	 * only be traversed once. */
+	while(context_pam2.finished == 0) {
+		done = 1;
+		dispatch_run(DISPATCH_BLOCK, &done, appdata_ptr);
+		if(context_pam2.finished == 0) {
+			debug("extra packet during conversation");
+		}
+	}
+
+	if(context_pam2.num_received == context_pam2.num_expected) {
+		*resp = context_pam2.responses;
+		return PAM_SUCCESS;
+	} else {
+		return PAM_CONV_ERR;
+	}
+}
+
+void
+input_userauth_info_response_pam(int type, int plen, void *ctxt)
+{
+	Authctxt *authctxt = ctxt;
+	unsigned int nresp = 0, rlen = 0, i = 0;
+	char *resp;
+
+	if (authctxt == NULL)
+		fatal("input_userauth_info_response_pam: no authentication context");
+
+	if (authctxt->attempt++ >= AUTH_FAIL_MAX)
+		packet_disconnect("too many failed userauth_requests");
+
+	nresp = packet_get_int();	/* Number of responses. */
+	debug("got %d responses", nresp);
+
+	for (i = 0; i < nresp; i++) {
+		int j = context_pam2.prompts[i];
+		resp = packet_get_string(&rlen);
+		debug("response ssh-%d(pam-%d) = \"%s\"", i, j, resp);
+		context_pam2.responses[j].resp_retcode = PAM_SUCCESS;
+		context_pam2.responses[j].resp = xstrdup(resp);
+		xfree(resp);
+		context_pam2.num_received++;
+	}
+
+	context_pam2.finished = 1;
+
+	packet_done();
+}
+
+#endif

auth2-pam.h

@@ -0,0 +1,6 @@
+#include "includes.h"
+#ifdef USE_PAM
+
+int	auth2_pam(Authctxt *authctxt);
+
+#endif /* USE_PAM */

auth2.c

@@ -400,10 +400,15 @@ userauth_kbdint(Authctxt *authctxt)
 	packet_done();
 
 	debug("keyboard-interactive language %s devs %s", lang, devs);
+#ifdef USE_PAM
+	if (authenticated == 0)
+		authenticated = auth2_pam(authctxt);
+#endif
 #ifdef SKEY
 	/* XXX hardcoded, we should look at devs */
-	if (options.skey_authentication != 0)
-		authenticated = auth2_skey(authctxt);
+	if (authenticated == 0)
+		if (options.skey_authentication != 0)
+			authenticated = auth2_skey(authctxt);
 #endif
 	xfree(lang);
 	xfree(devs);

ssh.h

@@ -558,8 +558,4 @@ int	auth_skey_password(struct passwd * pw, const char *password);
 /* AF_UNSPEC or AF_INET or AF_INET6 */
 extern int IPv4or6;
 
-#ifdef USE_PAM
-#include "auth-pam.h"
-#endif /* USE_PAM */
-
 #endif				/* SSH_H */