#

# Make pam_set_data/pam_get_data work with OpenSSH

#

# The way PAM is implemented in OpenSSH makes pam_set_data unusable

# for passing data between PAM stacks.

#

# The problem is, that pam_authenticate and pam_acct_mgmt are called

# in a separate auxiliary process. Any data stored using pam_set_data

# and any  other state information stored by those two functions are

# lost when the auxiliary process exits (with exceptions like

# environment variables, which are sent over between the processes).

#

# This patch fixes this by switching the roles of the monitor and the

# auxiliary process when doing PAM authentication. In the new code the

# monitor will be the one calling pam_authenticate and pam_acct_mgmt

# (eventually blocking and calling callbacks), whereas the other

# process (callback child) will be sending messages to the client

# (either directly or through privsep child).

#

# Patch origin: in-house

#

# Reported upstream:

# https://bugzilla.mindrot.org/show_bug.cgi?id=2548

#

diff -pur old/auth-pam.c new/auth-pam.c

--- old/auth-pam.c

+++ new/auth-pam.c

@@ -97,6 +97,7 @@

 #include "ssh-gss.h"

 #endif

 #include "monitor_wrap.h"

+#include "ssherr.h"

 extern ServerOptions options;

 extern Buffer loginmsg;

@@ -109,38 +110,26 @@ extern u_int utmp_len;

 #endif

 /*

- * Formerly known as USE_POSIX_THREADS, using this is completely unsupported

- * and generally a bad idea.  Use at own risk and do not expect support if

- * this breaks.

+ * PAM processing model has been rewritten.

+ * Now all the calls to PAM are within the monitor process,

+ * pam_get_data/pam_set_data works as designed and there is no need

+ * for the threads anymore.

  */

 #ifdef UNSUPPORTED_POSIX_THREADS_HACK

-#include <pthread.h>

-/*

- * Avoid namespace clash when *not* using pthreads for systems *with*

- * pthreads, which unconditionally define pthread_t via sys/types.h

- * (e.g. Linux)

- */

-typedef pthread_t sp_pthread_t;

-#else

-typedef pid_t sp_pthread_t;

+# error "UNSUPPORTED_POSIX_THREADS_HACK no longer supported"

 #endif

 struct pam_ctxt {

-	sp_pthread_t	 pam_thread;

-	int		 pam_psock;

-	int		 pam_csock;

-	int		 pam_done;

+	pid_t	 pam_child;

+	int	 pam_psock;

+	int	 pam_csock;

+	int	 pam_done;

 };

 static void sshpam_free_ctx(void *);

 static struct pam_ctxt *cleanup_ctxt;

-#ifndef UNSUPPORTED_POSIX_THREADS_HACK

-/*

- * Simulate threads with processes.

- */

-

-static int sshpam_thread_status = -1;

+static int sshpam_child_status = -1;

 static mysig_t sshpam_oldsig;

 static void

@@ -149,78 +138,22 @@ sshpam_sigchld_handler(int sig)

 	signal(SIGCHLD, SIG_DFL);

 	if (cleanup_ctxt == NULL)

 		return;	/* handler called after PAM cleanup, shouldn't happen */

-	if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)

+	if (waitpid(cleanup_ctxt->pam_child, &sshpam_child_status, WNOHANG)

 	    <= 0) {

-		/* PAM thread has not exitted, privsep slave must have */

-		kill(cleanup_ctxt->pam_thread, SIGTERM);

-		if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)

+		/* callback child has not exited, privsep slave must have */

+		kill(cleanup_ctxt->pam_child, SIGTERM);

+		if (waitpid(cleanup_ctxt->pam_child, &sshpam_child_status, 0)

 		    <= 0)

 			return; /* could not wait */

 	}

-	if (WIFSIGNALED(sshpam_thread_status) &&

-	    WTERMSIG(sshpam_thread_status) == SIGTERM)

-		return;	/* terminated by pthread_cancel */

-	if (!WIFEXITED(sshpam_thread_status))

-		sigdie("PAM: authentication thread exited unexpectedly");

-	if (WEXITSTATUS(sshpam_thread_status) != 0)

-		sigdie("PAM: authentication thread exited uncleanly");

-}

-

-/* ARGSUSED */

-static void

-pthread_exit(void *value)

-{

-	_exit(0);

-}

-

-/* ARGSUSED */

-static int

-pthread_create(sp_pthread_t *thread, const void *attr,

-    void *(*thread_start)(void *), void *arg)

-{

-	pid_t pid;

-	struct pam_ctxt *ctx = arg;

-

-	sshpam_thread_status = -1;

-	switch ((pid = fork())) {

-	case -1:

-		error("fork(): %s", strerror(errno));

-		return (-1);

-	case 0:

-		close(ctx->pam_psock);

-		ctx->pam_psock = -1;

-		thread_start(arg);

-		_exit(1);

-	default:

-		*thread = pid;

-		close(ctx->pam_csock);

-		ctx->pam_csock = -1;

-		sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);

-		return (0);

-	}

-}

-

-static int

-pthread_cancel(sp_pthread_t thread)

-{

-	signal(SIGCHLD, sshpam_oldsig);

-	return (kill(thread, SIGTERM));

-}

-

-/* ARGSUSED */

-static int

-pthread_join(sp_pthread_t thread, void **value)

-{

-	int status;

-

-	if (sshpam_thread_status != -1)

-		return (sshpam_thread_status);

-	signal(SIGCHLD, sshpam_oldsig);

-	waitpid(thread, &status, 0);

-	return (status);

+	if (WIFSIGNALED(sshpam_child_status) &&

+	    WTERMSIG(sshpam_child_status) == SIGTERM)

+		return;

+	if (!WIFEXITED(sshpam_child_status))

+		sigdie("PAM: callback child exited unexpectedly");

+	if (WEXITSTATUS(sshpam_child_status) != 0)

+		sigdie("PAM: callback child exited uncleanly");

 }

-#endif

-

 static pam_handle_t *sshpam_handle = NULL;

 static int sshpam_err = 0;

@@ -290,55 +223,11 @@ sshpam_password_change_required(int reqd

 	}

 }

-/* Import regular and PAM environment from subprocess */

-static void

-import_environments(Buffer *b)

-{

-	char *env;

-	u_int i, num_env;

-	int err;

-

-	debug3("PAM: %s entering", __func__);

-

-#ifndef UNSUPPORTED_POSIX_THREADS_HACK

-	/* Import variables set by do_pam_account */

-	sshpam_account_status = buffer_get_int(b);

-	sshpam_password_change_required(buffer_get_int(b));

-

-	/* Import environment from subprocess */

-	num_env = buffer_get_int(b);

-	if (num_env > 1024)

-		fatal("%s: received %u environment variables, expected <= 1024",

-		    __func__, num_env);

-	sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));

-	debug3("PAM: num env strings %d", num_env);

-	for(i = 0; i < num_env; i++)

-		sshpam_env[i] = buffer_get_string(b, NULL);

-

-	sshpam_env[num_env] = NULL;

-

-	/* Import PAM environment from subprocess */

-	num_env = buffer_get_int(b);

-	debug("PAM: num PAM env strings %d", num_env);

-	for(i = 0; i < num_env; i++) {

-		env = buffer_get_string(b, NULL);

-

-#ifdef HAVE_PAM_PUTENV

-		/* Errors are not fatal here */

-		if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {

-			error("PAM: pam_putenv: %s",

-			    pam_strerror(sshpam_handle, sshpam_err));

-		}

-#endif

-	}

-#endif

-}

-

 /*

- * Conversation function for authentication thread.

+ * Conversation function for keyboard-interactive authentication.

  */

 static int

-sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,

+sshpam_child_conv(int n, sshpam_const struct pam_message **msg,

     struct pam_response **resp, void *data)

 {

 	Buffer buffer;

@@ -420,48 +309,84 @@ sshpam_thread_conv(int n, sshpam_const s

 }

 /*

- * Authentication thread.

+ * Terminates the call back child.

+ *

+ * Sends a message of type PAM_SUCCESS or PAM_AUTH_ERR to the child.

+ * In response receives a message with remaining PAM prompts.

+ * When not using privilege separation, receives serialized packet state too.

+ *

+ * After that, the child exits.

  */

-static void *

-sshpam_thread(void *ctxtp)

+void

+relieve_from_duty(struct pam_ctxt *ctxt)

 {

-	struct pam_ctxt *ctxt = ctxtp;

 	Buffer buffer;

-	struct pam_conv sshpam_conv;

-	int flags = (options.permit_empty_passwd == 0 ?

-	    PAM_DISALLOW_NULL_AUTHTOK : 0);

-#ifndef UNSUPPORTED_POSIX_THREADS_HACK

-	extern char **environ;

-	char **env_from_pam;

-	u_int i;

-	const char *pam_user;

-	const char **ptr_pam_user = &pam_user;

-	char *tz = getenv("TZ");

+	struct ssh *ssh = active_state;

+	int r;

+	u_char type;

+	char *msg;

+	u_int len;

-	sshpam_err = pam_get_item(sshpam_handle, PAM_USER,

-	    (sshpam_const void **)ptr_pam_user);

-	if (sshpam_err != PAM_SUCCESS)

-		goto auth_fail;

+	buffer_init(&buffer);

+	buffer_put_cstring(&buffer, "OK");

+	type = (ctxt->pam_done == 1) ? PAM_SUCCESS : PAM_AUTH_ERR;

+	if (ssh_msg_send(ctxt->pam_csock, type, &buffer) == -1) {

+		buffer_free(&buffer);

+		fatal("%s: cannnot terminate callback child (send)", __func__);

+	}

-	environ[0] = NULL;

-	if (tz != NULL)

-		if (setenv("TZ", tz, 1) == -1)

-			error("PAM: could not set TZ environment: %s",

-			    strerror(errno));

-

-	if (sshpam_authctxt != NULL) {

-		setproctitle("%s [pam]",

-		    sshpam_authctxt->valid ? pam_user : "unknown");

+	buffer_clear(&buffer);

+	if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1) {

+		buffer_free(&buffer);

+		fatal("%s: cannnot terminate callback child (receive)",

+		    __func__);

 	}

-#endif

+	type = buffer_get_char(&buffer);

+	msg = buffer_get_cstring(&buffer, &len);

+	if (len)

+		buffer_append(&loginmsg, msg, len);

+	/* if not using privsep child, sync packet state from callback child */	

+	if (!use_privsep) {

+		if ((r = ssh_packet_set_state(ssh, &buffer)) != 0)

+			fatal("%s: set_state failed: %s",

+			   __func__, ssh_err(r));

+	}

+	free(msg);

+	buffer_free(&buffer);

+	close(ctxt->pam_csock);

+	ctxt->pam_csock = -1;

+}

+

+int

+get_pam_done(void *ctxt)

+{

+	struct pam_ctxt *pctxt = (struct pam_ctxt *)ctxt;

+	return (pctxt->pam_done);

+}

-	sshpam_conv.conv = sshpam_thread_conv;

+/*

+ * Perform PAM authentication.

+ *

+ * PAM APIs (pam_authenticate, pam_acct_mgmt, ...) block and call the

+ * provided callback conversation function (sshpam_conv). The conversation

+ * function sends messages to the callback child (pam_ctxt.pam_child), which

+ * communicates with the client directly, or indirectly through privsep child.

+ */

+void

+do_pam_auth(struct pam_ctxt *ctxt)

+{

+	struct pam_conv sshpam_conv;

+	int flags = (options.permit_empty_passwd == 0 ?

+	    PAM_DISALLOW_NULL_AUTHTOK : 0);

+

+	sshpam_conv.conv = sshpam_child_conv;

 	sshpam_conv.appdata_ptr = ctxt;

+	ctxt->pam_done = -1;

+

 	if (sshpam_authctxt == NULL)

 		fatal("%s: PAM authctxt not initialized", __func__);

-	buffer_init(&buffer);

 	sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,

 	    (const void *)&sshpam_conv);

 	if (sshpam_err != PAM_SUCCESS)

@@ -484,60 +409,34 @@ sshpam_thread(void *ctxtp)

 		}

 	}

-	buffer_put_cstring(&buffer, "OK");

-

-#ifndef UNSUPPORTED_POSIX_THREADS_HACK

-	/* Export variables set by do_pam_account */

-	buffer_put_int(&buffer, sshpam_account_status);

-	buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);

-

-	/* Export any environment strings set in child */

-	for(i = 0; environ[i] != NULL; i++)

-		; /* Count */

-	buffer_put_int(&buffer, i);

-	for(i = 0; environ[i] != NULL; i++)

-		buffer_put_cstring(&buffer, environ[i]);

-

-	/* Export any environment strings set by PAM in child */

-	env_from_pam = pam_getenvlist(sshpam_handle);

-	for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)

-		; /* Count */

-	buffer_put_int(&buffer, i);

-	for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)

-		buffer_put_cstring(&buffer, env_from_pam[i]);

-#endif /* UNSUPPORTED_POSIX_THREADS_HACK */

-

-	/* XXX - can't do much about an error here */

-	ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);

-	buffer_free(&buffer);

-	pthread_exit(NULL);

+	ctxt->pam_done = 1;

  auth_fail:

-	buffer_put_cstring(&buffer,

-	    pam_strerror(sshpam_handle, sshpam_err));

-	/* XXX - can't do much about an error here */

-	if (sshpam_err == PAM_ACCT_EXPIRED)

-		ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer);

-	else

-		ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);

-	buffer_free(&buffer);

-	pthread_exit(NULL);

-

-	return (NULL); /* Avoid warning for non-pthread case */

+	if (sshpam_err != PAM_SUCCESS)

+		error("PAM: %s for %s%.100s from %.100s",

+		    pam_strerror(sshpam_handle, sshpam_err),

+		    sshpam_authctxt->valid ? "" : "illegal user ",

+		    sshpam_authctxt->user,

+		    get_remote_name_or_ip(utmp_len, options.use_dns));

+	relieve_from_duty(ctxt);

 }

 void

-sshpam_thread_cleanup(void)

+sshpam_child_cleanup(void)

 {

 	struct pam_ctxt *ctxt = cleanup_ctxt;

 	debug3("PAM: %s entering", __func__);

-	if (ctxt != NULL && ctxt->pam_thread != 0) {

-		pthread_cancel(ctxt->pam_thread);

-		pthread_join(ctxt->pam_thread, NULL);

-		close(ctxt->pam_psock);

-		close(ctxt->pam_csock);

-		memset(ctxt, 0, sizeof(*ctxt));

+	if (ctxt != NULL && ctxt->pam_child != 0) {

+		signal(SIGCHLD, sshpam_oldsig);

+		/* callback child should have had exited by now */

+		kill(ctxt->pam_child, SIGTERM);

+		if (ctxt->pam_psock != -1)

+			close(ctxt->pam_psock);

+		if (ctxt->pam_csock != -1)

+			close(ctxt->pam_csock);

+		if (sshpam_child_status == -1)

+			waitpid(ctxt->pam_child, &sshpam_child_status, 0);

 		cleanup_ctxt = NULL;

 	}

 }

@@ -686,7 +585,6 @@ derive_pam_service_name(Authctxt *authct

 static int

 sshpam_init(Authctxt *authctxt)

 {

-	extern char *__progname;

 	const char *pam_rhost, *pam_user, *user = authctxt->user;

 	const char **ptr_pam_user = &pam_user;

@@ -792,6 +690,7 @@ sshpam_init_ctx(Authctxt *authctxt)

 {

 	struct pam_ctxt *ctxt;

 	int socks[2];

+	pid_t pid;

 	debug3("PAM: %s entering", __func__);

 	/*

@@ -809,7 +708,7 @@ sshpam_init_ctx(Authctxt *authctxt)

 	ctxt = xcalloc(1, sizeof *ctxt);

-	/* Start the authentication thread */

+	/* Fork the callback child and start PAM authentication */

 	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {

 		error("PAM: failed create sockets: %s", strerror(errno));

 		free(ctxt);

@@ -817,15 +716,29 @@ sshpam_init_ctx(Authctxt *authctxt)

 	}

 	ctxt->pam_psock = socks[0];

 	ctxt->pam_csock = socks[1];

-	if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {

-		error("PAM: failed to start authentication thread: %s",

-		    strerror(errno));

+

+	sshpam_child_status = -1;

+	switch ((pid = fork())) {

+	case -1:

+		error("fork(): %s", strerror(errno));

 		close(socks[0]);

 		close(socks[1]);

 		free(ctxt);

 		return (NULL);

+	case 0:

+		/* child processes query & respond for kbdint */

+		close(ctxt->pam_csock);

+		ctxt->pam_csock = -1;

+		break;

+	default:

+		/* parent does PAM */

+		ctxt->pam_child = pid;

+		close(ctxt->pam_psock);

+		ctxt->pam_psock = -1;

+		sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);

+		cleanup_ctxt = ctxt;

+		do_pam_auth(ctxt);

 	}

-	cleanup_ctxt = ctxt;

 	return (ctxt);

 }

@@ -839,8 +752,11 @@ sshpam_query(void *ctx, char **name, cha

 	u_char type;

 	char *msg;

 	size_t len, mlen;

+	struct ssh *ssh;

+	int r;

 	debug3("PAM: %s entering", __func__);

+

 	buffer_init(&buffer);

 	*name = xstrdup("");

 	*info = xstrdup("");

@@ -848,6 +764,17 @@ sshpam_query(void *ctx, char **name, cha

 	**prompts = NULL;

 	plen = 0;

 	*echo_on = xmalloc(sizeof(u_int));

+

+	/* in case PAM was already done in callback child */

+	switch (ctxt->pam_done) {

+	case 1:

+		return (0);

+	case 0:

+		break;

+	default:

+		return (-1);

+	}

+

 	while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {

 		type = buffer_get_char(&buffer);

 		msg = buffer_get_string(&buffer, NULL);

@@ -879,15 +806,6 @@ sshpam_query(void *ctx, char **name, cha

 			/* FALLTHROUGH */

 		case PAM_AUTH_ERR:

 			debug3("PAM: %s", pam_strerror(sshpam_handle, type));

-			if (**prompts != NULL && strlen(**prompts) != 0) {

-				*info = **prompts;

-				**prompts = NULL;

-				*num = 0;

-				**echo_on = 0;

-				ctxt->pam_done = -1;

-				free(msg);