diff --git a/ssh-pkcs11-helper.c b/ssh-pkcs11-helper.c
new file mode 100644
index 0000000..f996270
--- /dev/null
+++ b/ssh-pkcs11-helper.c
@@ -0,0 +1,349 @@
+/*
+ * Copyright (c) 2010 Markus Friedl.  All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/queue.h>
+#include <sys/types.h>
+#include <sys/time.h>
+
+#include <stdarg.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "xmalloc.h"
+#include "buffer.h"
+#include "log.h"
+#include "misc.h"
+#include "key.h"
+#include "authfd.h"
+#include "ssh-pkcs11.h"
+
+/* borrows code from sftp-server and ssh-agent */
+
+struct pkcs11_keyinfo {
+	Key		*key;
+	char		*providername;
+	TAILQ_ENTRY(pkcs11_keyinfo) next;
+};
+
+TAILQ_HEAD(, pkcs11_keyinfo) pkcs11_keylist;
+
+#define MAX_MSG_LENGTH		10240 /*XXX*/
+
+/* helper */
+#define get_int()			buffer_get_int(&iqueue);
+#define get_string(lenp)		buffer_get_string(&iqueue, lenp);
+
+/* input and output queue */
+Buffer iqueue;
+Buffer oqueue;
+
+static void
+add_key(Key *k, char *name)
+{
+	struct pkcs11_keyinfo *ki;
+
+	ki = xcalloc(1, sizeof(*ki));
+	ki->providername = xstrdup(name);
+	ki->key = k;
+	TAILQ_INSERT_TAIL(&pkcs11_keylist, ki, next);
+}
+
+static void
+del_keys_by_name(char *name)
+{
+	struct pkcs11_keyinfo *ki, *nxt;
+
+	for (ki = TAILQ_FIRST(&pkcs11_keylist); ki; ki = nxt) {
+		nxt = TAILQ_NEXT(ki, next);
+		if (!strcmp(ki->providername, name)) {
+			TAILQ_REMOVE(&pkcs11_keylist, ki, next);
+			xfree(ki->providername);
+			key_free(ki->key);
+			free(ki);
+		}
+	}
+}
+
+/* lookup matching 'private' key */
+static Key *
+lookup_key(Key *k)
+{
+	struct pkcs11_keyinfo *ki;
+
+	TAILQ_FOREACH(ki, &pkcs11_keylist, next) {
+		debug("check %p %s", ki, ki->providername);
+		if (key_equal(k, ki->key))
+			return (ki->key);
+	}
+	return (NULL);
+}
+
+static void
+send_msg(Buffer *m)
+{
+	int mlen = buffer_len(m);
+
+	buffer_put_int(&oqueue, mlen);
+	buffer_append(&oqueue, buffer_ptr(m), mlen);
+	buffer_consume(m, mlen);
+}
+
+static void
+process_add(void)
+{
+	char *name, *pin;
+	Key **keys;
+	int i, nkeys;
+	u_char *blob;
+	u_int blen;
+	Buffer msg;
+
+	buffer_init(&msg);
+	name = get_string(NULL);
+	pin = get_string(NULL);
+	if ((nkeys = pkcs11_add_provider(name, pin, &keys)) > 0) {
+		buffer_put_char(&msg, SSH2_AGENT_IDENTITIES_ANSWER);
+		buffer_put_int(&msg, nkeys);
+		for (i = 0; i < nkeys; i++) {
+			key_to_blob(keys[i], &blob, &blen);
+			buffer_put_string(&msg, blob, blen);
+			buffer_put_cstring(&msg, name);
+			xfree(blob);
+			add_key(keys[i], name);
+		}
+		xfree(keys);
+	} else {
+		buffer_put_char(&msg, SSH_AGENT_FAILURE);
+	}
+	xfree(pin);
+	xfree(name);
+	send_msg(&msg);
+	buffer_free(&msg);
+}
+
+static void
+process_del(void)
+{
+	char *name, *pin;
+	Buffer msg;
+
+	buffer_init(&msg);
+	name = get_string(NULL);
+	pin = get_string(NULL);
+	del_keys_by_name(name);
+	if (pkcs11_del_provider(name) == 0)
+		 buffer_put_char(&msg, SSH_AGENT_SUCCESS);
+	else
+		 buffer_put_char(&msg, SSH_AGENT_FAILURE);
+	xfree(pin);
+	xfree(name);
+	send_msg(&msg);
+	buffer_free(&msg);
+}
+
+static void
+process_sign(void)
+{
+	u_char *blob, *data, *signature = NULL;
+	u_int blen, dlen, slen = 0;
+	int ok = -1, flags, ret;
+	Key *key, *found;
+	Buffer msg;
+
+	blob = get_string(&blen);
+	data = get_string(&dlen);
+	flags = get_int(); /* XXX ignore */
+
+	if ((key = key_from_blob(blob, blen)) != NULL) {
+		if ((found = lookup_key(key)) != NULL) {
+			slen = RSA_size(key->rsa);
+			signature = xmalloc(slen);
+			if ((ret = RSA_private_encrypt(dlen, data, signature,
+			    found->rsa, RSA_PKCS1_PADDING)) != -1) {
+				slen = ret;
+				ok = 0;
+			}
+		}
+		key_free(key);
+	}
+	buffer_init(&msg);
+	if (ok == 0) {
+		buffer_put_char(&msg, SSH2_AGENT_SIGN_RESPONSE);
+		buffer_put_string(&msg, signature, slen);
+	} else {
+		buffer_put_char(&msg, SSH_AGENT_FAILURE);
+	}
+	xfree(data);
+	xfree(blob);
+	if (signature != NULL)
+		xfree(signature);
+	send_msg(&msg);
+	buffer_free(&msg);
+}
+
+static void
+process(void)
+{
+	u_int msg_len;
+	u_int buf_len;
+	u_int consumed;
+	u_int type;
+	u_char *cp;
+
+	buf_len = buffer_len(&iqueue);
+	if (buf_len < 5)
+		return;		/* Incomplete message. */
+	cp = buffer_ptr(&iqueue);
+	msg_len = get_u32(cp);
+	if (msg_len > MAX_MSG_LENGTH) {
+		error("bad message len %d", msg_len);
+		cleanup_exit(11);
+	}
+	if (buf_len < msg_len + 4)
+		return;
+	buffer_consume(&iqueue, 4);
+	buf_len -= 4;
+	type = buffer_get_char(&iqueue);
+	switch (type) {
+	case SSH_AGENTC_ADD_SMARTCARD_KEY:
+		debug("process_add");
+		process_add();
+		break;
+	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
+		debug("process_del");
+		process_del();
+		break;
+	case SSH2_AGENTC_SIGN_REQUEST:
+		debug("process_sign");
+		process_sign();
+		break;
+	default:
+		error("Unknown message %d", type);
+		break;
+	}
+	/* discard the remaining bytes from the current packet */
+	if (buf_len < buffer_len(&iqueue)) {
+		error("iqueue grew unexpectedly");
+		cleanup_exit(255);
+	}
+	consumed = buf_len - buffer_len(&iqueue);
+	if (msg_len < consumed) {
+		error("msg_len %d < consumed %d", msg_len, consumed);
+		cleanup_exit(255);
+	}
+	if (msg_len > consumed)
+		buffer_consume(&iqueue, msg_len - consumed);
+}
+
+void
+cleanup_exit(int i)
+{
+	/* XXX */
+	_exit(i);
+}
+
+int
+main(int argc, char **argv)
+{
+	fd_set *rset, *wset;
+	int in, out, max, log_stderr = 0;
+	ssize_t len, olen, set_size;
+	SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
+	LogLevel log_level = SYSLOG_LEVEL_ERROR;
+	char buf[4*4096];
+
+	TAILQ_INIT(&pkcs11_keylist);
+	pkcs11_init(0);
+
+	extern char *optarg;
+	extern char *__progname;
+
+	log_init(__progname, log_level, log_facility, log_stderr);
+
+	in = STDIN_FILENO;
+	out = STDOUT_FILENO;
+
+	max = 0;
+	if (in > max)
+		max = in;
+	if (out > max)
+		max = out;
+
+	buffer_init(&iqueue);
+	buffer_init(&oqueue);
+
+	set_size = howmany(max + 1, NFDBITS) * sizeof(fd_mask);
+	rset = (fd_set *)xmalloc(set_size);
+	wset = (fd_set *)xmalloc(set_size);
+
+	for (;;) {
+		memset(rset, 0, set_size);
+		memset(wset, 0, set_size);
+
+		/*
+		 * Ensure that we can read a full buffer and handle
+		 * the worst-case length packet it can generate,
+		 * otherwise apply backpressure by stopping reads.
+		 */
+		if (buffer_check_alloc(&iqueue, sizeof(buf)) &&
+		    buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
+			FD_SET(in, rset);
+
+		olen = buffer_len(&oqueue);
+		if (olen > 0)
+			FD_SET(out, wset);
+
+		if (select(max+1, rset, wset, NULL, NULL) < 0) {
+			if (errno == EINTR)
+				continue;
+			error("select: %s", strerror(errno));
+			cleanup_exit(2);
+		}
+
+		/* copy stdin to iqueue */
+		if (FD_ISSET(in, rset)) {
+			len = read(in, buf, sizeof buf);
+			if (len == 0) {
+				debug("read eof");
+				cleanup_exit(0);
+			} else if (len < 0) {
+				error("read: %s", strerror(errno));
+				cleanup_exit(1);
+			} else {
+				buffer_append(&iqueue, buf, len);
+			}
+		}
+		/* send oqueue to stdout */
+		if (FD_ISSET(out, wset)) {
+			len = write(out, buffer_ptr(&oqueue), olen);
+			if (len < 0) {
+				error("write: %s", strerror(errno));
+				cleanup_exit(1);
+			} else {
+				buffer_consume(&oqueue, len);
+			}
+		}
+
+		/*
+		 * Process requests from client if we can fit the results
+		 * into the output buffer, otherwise stop processing input
+		 * and let the output queue drain.
+		 */
+		if (buffer_check_alloc(&oqueue, MAX_MSG_LENGTH))
+			process();
+	}
+}