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Replace <sys/param.h> with <limits.h> and other less dirty headers where
possible.  Annotate <sys/param.h> lines with their current reasons.  Switch
to PATH_MAX, NGROUPS_MAX, HOST_NAME_MAX+1, LOGIN_NAME_MAX, etc.  Change
MIN() and MAX() to local definitions of MINIMUM() and MAXIMUM() where
sensible to avoid pulling in the pollution.  These are the files confirmed
through binary verification.
ok guenther, millert, doug (helped with the verification protocol)

/* $OpenBSD: ssh-agent.c,v 1.196 2015/01/16 06:40:12 deraadt Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * The authentication agent program.
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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/param.h>	/* MIN MAX */
#include <sys/types.h>
#include <sys/time.h>
#include <sys/queue.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>

#ifdef WITH_OPENSSL
#include <openssl/evp.h>
#endif

#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <time.h>
#include <unistd.h>

#include "key.h"	/* XXX for typedef */
#include "buffer.h"	/* XXX for typedef */

#include "xmalloc.h"
#include "ssh.h"
#include "rsa.h"
#include "sshbuf.h"
#include "sshkey.h"
#include "authfd.h"
#include "compat.h"
#include "log.h"
#include "misc.h"
#include "digest.h"
#include "ssherr.h"

#ifdef ENABLE_PKCS11
#include "ssh-pkcs11.h"
#endif

typedef enum {
	AUTH_UNUSED,
	AUTH_SOCKET,
	AUTH_CONNECTION
} sock_type;

typedef struct {
	int fd;
	sock_type type;
	struct sshbuf *input;
	struct sshbuf *output;
	struct sshbuf *request;
} SocketEntry;

u_int sockets_alloc = 0;
SocketEntry *sockets = NULL;

typedef struct identity {
	TAILQ_ENTRY(identity) next;
	struct sshkey *key;
	char *comment;
	char *provider;
	time_t death;
	u_int confirm;
} Identity;

typedef struct {
	int nentries;
	TAILQ_HEAD(idqueue, identity) idlist;
} Idtab;

/* private key table, one per protocol version */
Idtab idtable[3];

int max_fd = 0;

/* pid of shell == parent of agent */
pid_t parent_pid = -1;
time_t parent_alive_interval = 0;

/* pid of process for which cleanup_socket is applicable */
pid_t cleanup_pid = 0;

/* pathname and directory for AUTH_SOCKET */
char socket_name[PATH_MAX];
char socket_dir[PATH_MAX];

/* locking */
int locked = 0;
char *lock_passwd = NULL;

extern char *__progname;

/* Default lifetime in seconds (0 == forever) */
static long lifetime = 0;

static int fingerprint_hash = SSH_FP_HASH_DEFAULT;

static void
close_socket(SocketEntry *e)
{
	close(e->fd);
	e->fd = -1;
	e->type = AUTH_UNUSED;
	sshbuf_free(e->input);
	sshbuf_free(e->output);
	sshbuf_free(e->request);
}

static void
idtab_init(void)
{
	int i;

	for (i = 0; i <=2; i++) {
		TAILQ_INIT(&idtable[i].idlist);
		idtable[i].nentries = 0;
	}
}

/* return private key table for requested protocol version */
static Idtab *
idtab_lookup(int version)
{
	if (version < 1 || version > 2)
		fatal("internal error, bad protocol version %d", version);
	return &idtable[version];
}

static void
free_identity(Identity *id)
{
	sshkey_free(id->key);
	free(id->provider);
	free(id->comment);
	free(id);
}

/* return matching private key for given public key */
static Identity *
lookup_identity(struct sshkey *key, int version)
{
	Identity *id;

	Idtab *tab = idtab_lookup(version);
	TAILQ_FOREACH(id, &tab->idlist, next) {
		if (sshkey_equal(key, id->key))
			return (id);
	}
	return (NULL);
}

/* Check confirmation of keysign request */
static int
confirm_key(Identity *id)
{
	char *p;
	int ret = -1;

	p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
	if (ask_permission("Allow use of key %s?\nKey fingerprint %s.",
	    id->comment, p))
		ret = 0;
	free(p);

	return (ret);
}

static void
send_status(SocketEntry *e, int success)
{
	int r;

	if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
	    (r = sshbuf_put_u8(e->output, success ?
	    SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
}

/* send list of supported public keys to 'client' */
static void
process_request_identities(SocketEntry *e, int version)
{
	Idtab *tab = idtab_lookup(version);
	Identity *id;
	struct sshbuf *msg;
	int r;

	if ((msg = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((r = sshbuf_put_u8(msg, (version == 1) ?
	    SSH_AGENT_RSA_IDENTITIES_ANSWER :
	    SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
	    (r = sshbuf_put_u32(msg, tab->nentries)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	TAILQ_FOREACH(id, &tab->idlist, next) {
		if (id->key->type == KEY_RSA1) {
#ifdef WITH_SSH1
			if ((r = sshbuf_put_u32(msg,
			    BN_num_bits(id->key->rsa->n))) != 0 ||
			    (r = sshbuf_put_bignum1(msg,
			    id->key->rsa->e)) != 0 ||
			    (r = sshbuf_put_bignum1(msg,
			    id->key->rsa->n)) != 0)
				fatal("%s: buffer error: %s",
				    __func__, ssh_err(r));
#endif
		} else {
			u_char *blob;
			size_t blen;

			if ((r = sshkey_to_blob(id->key, &blob, &blen)) != 0) {
				error("%s: sshkey_to_blob: %s", __func__,
				    ssh_err(r));
				continue;
			}
			if ((r = sshbuf_put_string(msg, blob, blen)) != 0)
				fatal("%s: buffer error: %s",
				    __func__, ssh_err(r));
			free(blob);
		}
		if ((r = sshbuf_put_cstring(msg, id->comment)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
	}
	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	sshbuf_free(msg);
}

#ifdef WITH_SSH1
/* ssh1 only */
static void
process_authentication_challenge1(SocketEntry *e)
{
	u_char buf[32], mdbuf[16], session_id[16];
	u_int response_type;
	BIGNUM *challenge;
	Identity *id;
	int r, len;
	struct sshbuf *msg;
	struct ssh_digest_ctx *md;
	struct sshkey *key;

	if ((msg = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((key = sshkey_new(KEY_RSA1)) == NULL)
		fatal("%s: sshkey_new failed", __func__);
	if ((challenge = BN_new()) == NULL)
		fatal("%s: BN_new failed", __func__);

	if ((r = sshbuf_get_u32(e->request, NULL)) != 0 || /* ignored */
	    (r = sshbuf_get_bignum1(e->request, key->rsa->e)) != 0 ||
	    (r = sshbuf_get_bignum1(e->request, key->rsa->n)) != 0 ||
	    (r = sshbuf_get_bignum1(e->request, challenge)))
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	/* Only protocol 1.1 is supported */
	if (sshbuf_len(e->request) == 0)
		goto failure;
	if ((r = sshbuf_get(e->request, session_id, sizeof(session_id))) != 0 ||
	    (r = sshbuf_get_u32(e->request, &response_type)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (response_type != 1)
		goto failure;

	id = lookup_identity(key, 1);
	if (id != NULL && (!id->confirm || confirm_key(id) == 0)) {
		struct sshkey *private = id->key;
		/* Decrypt the challenge using the private key. */
		if ((r = rsa_private_decrypt(challenge, challenge,
		    private->rsa) != 0)) {
			fatal("%s: rsa_public_encrypt: %s", __func__,
			    ssh_err(r));
			goto failure;	/* XXX ? */
		}

		/* The response is MD5 of decrypted challenge plus session id */
		len = BN_num_bytes(challenge);
		if (len <= 0 || len > 32) {
			logit("%s: bad challenge length %d", __func__, len);
			goto failure;
		}
		memset(buf, 0, 32);
		BN_bn2bin(challenge, buf + 32 - len);
		if ((md = ssh_digest_start(SSH_DIGEST_MD5)) == NULL ||
		    ssh_digest_update(md, buf, 32) < 0 ||
		    ssh_digest_update(md, session_id, 16) < 0 ||
		    ssh_digest_final(md, mdbuf, sizeof(mdbuf)) < 0)
			fatal("%s: md5 failed", __func__);
		ssh_digest_free(md);

		/* Send the response. */
		if ((r = sshbuf_put_u8(msg, SSH_AGENT_RSA_RESPONSE)) != 0 ||
		    (r = sshbuf_put(msg, mdbuf, sizeof(mdbuf))) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
		goto send;
	}

 failure:
	/* Unknown identity or protocol error.  Send failure. */
	if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
 send:
	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	sshkey_free(key);
	BN_clear_free(challenge);
	sshbuf_free(msg);
}
#endif

/* ssh2 only */
static void
process_sign_request2(SocketEntry *e)
{
	u_char *blob, *data, *signature = NULL;
	size_t blen, dlen, slen = 0;
	u_int compat = 0, flags;
	int r, ok = -1;
	struct sshbuf *msg;
	struct sshkey *key;
	struct identity *id;

	if ((msg = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((r = sshbuf_get_string(e->request, &blob, &blen)) != 0 ||
	    (r = sshbuf_get_string(e->request, &data, &dlen)) != 0 ||
	    (r = sshbuf_get_u32(e->request, &flags)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (flags & SSH_AGENT_OLD_SIGNATURE)
		compat = SSH_BUG_SIGBLOB;
	if ((r = sshkey_from_blob(blob, blen, &key)) != 0) {
		error("%s: cannot parse key blob: %s", __func__, ssh_err(ok));
		goto send;
	}
	if ((id = lookup_identity(key, 2)) == NULL) {
		verbose("%s: %s key not found", __func__, sshkey_type(key));
		goto send;
	}
	if (id->confirm && confirm_key(id) != 0) {
		verbose("%s: user refused key", __func__);
		goto send;
	}
	if ((r = sshkey_sign(id->key, &signature, &slen,
	    data, dlen, compat)) != 0) {
		error("%s: sshkey_sign: %s", __func__, ssh_err(ok));
		goto send;
	}
	/* Success */
	ok = 0;
 send:
	sshkey_free(key);
	if (ok == 0) {
		if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
		    (r = sshbuf_put_string(msg, signature, slen)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
	} else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	sshbuf_free(msg);
	free(data);
	free(blob);
	free(signature);
}

/* shared */
static void
process_remove_identity(SocketEntry *e, int version)
{
	size_t blen;
	int r, success = 0;
	struct sshkey *key = NULL;
	u_char *blob;
#ifdef WITH_SSH1
	u_int bits;
#endif /* WITH_SSH1 */

	switch (version) {
#ifdef WITH_SSH1
	case 1:
		if ((key = sshkey_new(KEY_RSA1)) == NULL) {
			error("%s: sshkey_new failed", __func__);
			return;
		}
		if ((r = sshbuf_get_u32(e->request, &bits)) != 0 ||
		    (r = sshbuf_get_bignum1(e->request, key->rsa->e)) != 0 ||
		    (r = sshbuf_get_bignum1(e->request, key->rsa->n)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));

		if (bits != sshkey_size(key))
			logit("Warning: identity keysize mismatch: "
			    "actual %u, announced %u",
			    sshkey_size(key), bits);
		break;
#endif /* WITH_SSH1 */
	case 2:
		if ((r = sshbuf_get_string(e->request, &blob, &blen)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
		if ((r = sshkey_from_blob(blob, blen, &key)) != 0)
			error("%s: sshkey_from_blob failed: %s",
			    __func__, ssh_err(r));
		free(blob);
		break;
	}
	if (key != NULL) {
		Identity *id = lookup_identity(key, version);
		if (id != NULL) {
			/*
			 * We have this key.  Free the old key.  Since we
			 * don't want to leave empty slots in the middle of
			 * the array, we actually free the key there and move
			 * all the entries between the empty slot and the end
			 * of the array.
			 */
			Idtab *tab = idtab_lookup(version);
			if (tab->nentries < 1)
				fatal("process_remove_identity: "
				    "internal error: tab->nentries %d",
				    tab->nentries);
			TAILQ_REMOVE(&tab->idlist, id, next);
			free_identity(id);
			tab->nentries--;
			success = 1;
		}
		sshkey_free(key);
	}
	send_status(e, success);
}

static void
process_remove_all_identities(SocketEntry *e, int version)
{
	Idtab *tab = idtab_lookup(version);
	Identity *id;

	/* Loop over all identities and clear the keys. */
	for (id = TAILQ_FIRST(&tab->idlist); id;
	    id = TAILQ_FIRST(&tab->idlist)) {
		TAILQ_REMOVE(&tab->idlist, id, next);
		free_identity(id);
	}

	/* Mark that there are no identities. */
	tab->nentries = 0;

	/* Send success. */
	send_status(e, 1);
}

/* removes expired keys and returns number of seconds until the next expiry */
static time_t
reaper(void)
{
	time_t deadline = 0, now = monotime();
	Identity *id, *nxt;
	int version;
	Idtab *tab;

	for (version = 1; version < 3; version++) {
		tab = idtab_lookup(version);
		for (id = TAILQ_FIRST(&tab->idlist); id; id = nxt) {
			nxt = TAILQ_NEXT(id, next);
			if (id->death == 0)
				continue;
			if (now >= id->death) {
				debug("expiring key '%s'", id->comment);
				TAILQ_REMOVE(&tab->idlist, id, next);
				free_identity(id);
				tab->nentries--;
			} else
				deadline = (deadline == 0) ? id->death :
				    MIN(deadline, id->death);
		}
	}
	if (deadline == 0 || deadline <= now)
		return 0;
	else
		return (deadline - now);
}

/*
 * XXX this and the corresponding serialisation function probably belongs
 * in key.c
 */
static int
agent_decode_rsa1(struct sshbuf *m, struct sshkey **kp)
{
	struct sshkey *k = NULL;
	int r = SSH_ERR_INTERNAL_ERROR;

	*kp = NULL;
	if ((k = sshkey_new_private(KEY_RSA1)) == NULL)
		return SSH_ERR_ALLOC_FAIL;

	if ((r = sshbuf_get_u32(m, NULL)) != 0 ||		/* ignored */
	    (r = sshbuf_get_bignum1(m, k->rsa->n)) != 0 ||
	    (r = sshbuf_get_bignum1(m, k->rsa->e)) != 0 ||
	    (r = sshbuf_get_bignum1(m, k->rsa->d)) != 0 ||
	    (r = sshbuf_get_bignum1(m, k->rsa->iqmp)) != 0 ||
	    /* SSH1 and SSL have p and q swapped */
	    (r = sshbuf_get_bignum1(m, k->rsa->q)) != 0 ||	/* p */
	    (r = sshbuf_get_bignum1(m, k->rsa->p)) != 0) 	/* q */
		goto out;

	/* Generate additional parameters */
	if ((r = rsa_generate_additional_parameters(k->rsa)) != 0)
		goto out;
	/* enable blinding */
	if (RSA_blinding_on(k->rsa, NULL) != 1) {
		r = SSH_ERR_LIBCRYPTO_ERROR;
		goto out;
	}

	r = 0; /* success */
 out:
	if (r == 0)
		*kp = k;
	else
		sshkey_free(k);
	return r;
}

static void
process_add_identity(SocketEntry *e, int version)
{
	Idtab *tab = idtab_lookup(version);
	Identity *id;
	int success = 0, confirm = 0;
	u_int seconds;
	char *comment = NULL;
	time_t death = 0;
	struct sshkey *k = NULL;
	u_char ctype;
	int r = SSH_ERR_INTERNAL_ERROR;

	switch (version) {
#ifdef WITH_SSH1
	case 1:
		r = agent_decode_rsa1(e->request, &k);
		break;
#endif /* WITH_SSH1 */
	case 2:
		r = sshkey_private_deserialize(e->request, &k);
		break;
	}
	if (r != 0 || k == NULL ||
	    (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
		error("%s: decode private key: %s", __func__, ssh_err(r));
		goto err;
	}

	while (sshbuf_len(e->request)) {
		if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) {
			error("%s: buffer error: %s", __func__, ssh_err(r));
			goto err;
		}
		switch (ctype) {
		case SSH_AGENT_CONSTRAIN_LIFETIME:
			if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
				error("%s: bad lifetime constraint: %s",
				    __func__, ssh_err(r));
				goto err;
			}
			death = monotime() + seconds;
			break;
		case SSH_AGENT_CONSTRAIN_CONFIRM:
			confirm = 1;
			break;
		default:
			error("%s: Unknown constraint %d", __func__, ctype);
 err:
			sshbuf_reset(e->request);
			free(comment);
			sshkey_free(k);
			goto send;
		}
	}

	success = 1;
	if (lifetime && !death)
		death = monotime() + lifetime;
	if ((id = lookup_identity(k, version)) == NULL) {
		id = xcalloc(1, sizeof(Identity));
		id->key = k;
		TAILQ_INSERT_TAIL(&tab->idlist, id, next);
		/* Increment the number of identities. */
		tab->nentries++;
	} else {
		sshkey_free(k);
		free(id->comment);
	}
	id->comment = comment;
	id->death = death;
	id->confirm = confirm;
send:
	send_status(e, success);
}

/* XXX todo: encrypt sensitive data with passphrase */
static void
process_lock_agent(SocketEntry *e, int lock)
{
	int r, success = 0;
	char *passwd;

	if ((r = sshbuf_get_cstring(e->request, &passwd, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	if (locked && !lock && strcmp(passwd, lock_passwd) == 0) {
		locked = 0;
		explicit_bzero(lock_passwd, strlen(lock_passwd));
		free(lock_passwd);
		lock_passwd = NULL;
		success = 1;
	} else if (!locked && lock) {
		locked = 1;
		lock_passwd = xstrdup(passwd);
		success = 1;
	}
	explicit_bzero(passwd, strlen(passwd));
	free(passwd);
	send_status(e, success);
}

static void
no_identities(SocketEntry *e, u_int type)
{
	struct sshbuf *msg;
	int r;

	if ((msg = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((r = sshbuf_put_u8(msg,
	    (type == SSH_AGENTC_REQUEST_RSA_IDENTITIES) ?
	    SSH_AGENT_RSA_IDENTITIES_ANSWER :
	    SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
	    (r = sshbuf_put_u32(msg, 0)) != 0 ||
	    (r = sshbuf_put_stringb(e->output, msg)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	sshbuf_free(msg);
}

#ifdef ENABLE_PKCS11
static void
process_add_smartcard_key(SocketEntry *e)
{
	char *provider = NULL, *pin;
	int r, i, version, count = 0, success = 0, confirm = 0;
	u_int seconds;
	time_t death = 0;
	u_char type;
	struct sshkey **keys = NULL, *k;
	Identity *id;
	Idtab *tab;

	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	while (sshbuf_len(e->request)) {
		if ((r = sshbuf_get_u8(e->request, &type)) != 0)
			fatal("%s: buffer error: %s", __func__, ssh_err(r));
		switch (type) {
		case SSH_AGENT_CONSTRAIN_LIFETIME:
			if ((r = sshbuf_get_u32(e->request, &seconds)) != 0)
				fatal("%s: buffer error: %s",
				    __func__, ssh_err(r));
			death = monotime() + seconds;
			break;
		case SSH_AGENT_CONSTRAIN_CONFIRM:
			confirm = 1;
			break;
		default:
			error("process_add_smartcard_key: "
			    "Unknown constraint type %d", type);
			goto send;
		}
	}
	if (lifetime && !death)
		death = monotime() + lifetime;

	count = pkcs11_add_provider(provider, pin, &keys);
	for (i = 0; i < count; i++) {
		k = keys[i];
		version = k->type == KEY_RSA1 ? 1 : 2;
		tab = idtab_lookup(version);
		if (lookup_identity(k, version) == NULL) {
			id = xcalloc(1, sizeof(Identity));
			id->key = k;
			id->provider = xstrdup(provider);
			id->comment = xstrdup(provider); /* XXX */
			id->death = death;
			id->confirm = confirm;
			TAILQ_INSERT_TAIL(&tab->idlist, id, next);
			tab->nentries++;
			success = 1;
		} else {
			sshkey_free(k);
		}
		keys[i] = NULL;
	}
send:
	free(pin);
	free(provider);
	free(keys);
	send_status(e, success);
}

static void
process_remove_smartcard_key(SocketEntry *e)
{
	char *provider = NULL, *pin = NULL;
	int r, version, success = 0;
	Identity *id, *nxt;
	Idtab *tab;

	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));
	free(pin);

	for (version = 1; version < 3; version++) {
		tab = idtab_lookup(version);
		for (id = TAILQ_FIRST(&tab->idlist); id; id = nxt) {
			nxt = TAILQ_NEXT(id, next);
			/* Skip file--based keys */
			if (id->provider == NULL)
				continue;
			if (!strcmp(provider, id->provider)) {
				TAILQ_REMOVE(&tab->idlist, id, next);
				free_identity(id);
				tab->nentries--;
			}
		}
	}
	if (pkcs11_del_provider(provider) == 0)
		success = 1;
	else
		error("process_remove_smartcard_key:"
		    " pkcs11_del_provider failed");
	free(provider);
	send_status(e, success);
}
#endif /* ENABLE_PKCS11 */

/* dispatch incoming messages */

static void
process_message(SocketEntry *e)
{
	u_int msg_len;
	u_char type;
	const u_char *cp;
	int r;

	if (sshbuf_len(e->input) < 5)
		return;		/* Incomplete message. */
	cp = sshbuf_ptr(e->input);
	msg_len = PEEK_U32(cp);
	if (msg_len > 256 * 1024) {
		close_socket(e);
		return;
	}
	if (sshbuf_len(e->input) < msg_len + 4)
		return;

	/* move the current input to e->request */
	sshbuf_reset(e->request);
	if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
	    (r = sshbuf_get_u8(e->request, &type)) != 0)
		fatal("%s: buffer error: %s", __func__, ssh_err(r));

	/* check wheter agent is locked */
	if (locked && type != SSH_AGENTC_UNLOCK) {
		sshbuf_reset(e->request);
		switch (type) {
		case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
		case SSH2_AGENTC_REQUEST_IDENTITIES:
			/* send empty lists */
			no_identities(e, type);
			break;
		default:
			/* send a fail message for all other request types */
			send_status(e, 0);
		}
		return;
	}

	debug("type %d", type);
	switch (type) {
	case SSH_AGENTC_LOCK:
	case SSH_AGENTC_UNLOCK:
		process_lock_agent(e, type == SSH_AGENTC_LOCK);
		break;
#ifdef WITH_SSH1
	/* ssh1 */
	case SSH_AGENTC_RSA_CHALLENGE:
		process_authentication_challenge1(e);
		break;
	case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
		process_request_identities(e, 1);
		break;
	case SSH_AGENTC_ADD_RSA_IDENTITY:
	case SSH_AGENTC_ADD_RSA_ID_CONSTRAINED:
		process_add_identity(e, 1);
		break;
	case SSH_AGENTC_REMOVE_RSA_IDENTITY:
		process_remove_identity(e, 1);
		break;
	case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
		process_remove_all_identities(e, 1);
		break;
#endif
	/* ssh2 */
	case SSH2_AGENTC_SIGN_REQUEST:
		process_sign_request2(e);
		break;
	case SSH2_AGENTC_REQUEST_IDENTITIES:
		process_request_identities(e, 2);
		break;
	case SSH2_AGENTC_ADD_IDENTITY:
	case SSH2_AGENTC_ADD_ID_CONSTRAINED:
		process_add_identity(e, 2);
		break;
	case SSH2_AGENTC_REMOVE_IDENTITY:
		process_remove_identity(e, 2);
		break;
	case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
		process_remove_all_identities(e, 2);
		break;
#ifdef ENABLE_PKCS11
	case SSH_AGENTC_ADD_SMARTCARD_KEY:
	case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
		process_add_smartcard_key(e);
		break;
	case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
		process_remove_smartcard_key(e);
		break;
#endif /* ENABLE_PKCS11 */
	default:
		/* Unknown message.  Respond with failure. */
		error("Unknown message %d", type);
		sshbuf_reset(e->request);
		send_status(e, 0);
		break;
	}
}

static void
new_socket(sock_type type, int fd)
{
	u_int i, old_alloc, new_alloc;

	set_nonblock(fd);

	if (fd > max_fd)
		max_fd = fd;

	for (i = 0; i < sockets_alloc; i++)
		if (sockets[i].type == AUTH_UNUSED) {
			sockets[i].fd = fd;
			if ((sockets[i].input = sshbuf_new()) == NULL)
				fatal("%s: sshbuf_new failed", __func__);
			if ((sockets[i].output = sshbuf_new()) == NULL)
				fatal("%s: sshbuf_new failed", __func__);
			if ((sockets[i].request = sshbuf_new()) == NULL)
				fatal("%s: sshbuf_new failed", __func__);
			sockets[i].type = type;
			return;
		}
	old_alloc = sockets_alloc;
	new_alloc = sockets_alloc + 10;
	sockets = xrealloc(sockets, new_alloc, sizeof(sockets[0]));
	for (i = old_alloc; i < new_alloc; i++)
		sockets[i].type = AUTH_UNUSED;
	sockets_alloc = new_alloc;
	sockets[old_alloc].fd = fd;
	if ((sockets[old_alloc].input = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((sockets[old_alloc].output = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	if ((sockets[old_alloc].request = sshbuf_new()) == NULL)
		fatal("%s: sshbuf_new failed", __func__);
	sockets[old_alloc].type = type;
}

static int
prepare_select(fd_set **fdrp, fd_set **fdwp, int *fdl, u_int *nallocp,
    struct timeval **tvpp)
{
	u_int i, sz;
	int n = 0;
	static struct timeval tv;
	time_t deadline;

	for (i = 0; i < sockets_alloc; i++) {
		switch (sockets[i].type) {
		case AUTH_SOCKET:
		case AUTH_CONNECTION:
			n = MAX(n, sockets[i].fd);
			break;
		case AUTH_UNUSED:
			break;
		default:
			fatal("Unknown socket type %d", sockets[i].type);
			break;
		}
	}

	sz = howmany(n+1, NFDBITS) * sizeof(fd_mask);
	if (*fdrp == NULL || sz > *nallocp) {
		free(*fdrp);
		free(*fdwp);
		*fdrp = xmalloc(sz);
		*fdwp = xmalloc(sz);
		*nallocp = sz;
	}
	if (n < *fdl)
		debug("XXX shrink: %d < %d", n, *fdl);
	*fdl = n;
	memset(*fdrp, 0, sz);
	memset(*fdwp, 0, sz);

	for (i = 0; i < sockets_alloc; i++) {
		switch (sockets[i].type) {
		case AUTH_SOCKET:
		case AUTH_CONNECTION:
			FD_SET(sockets[i].fd, *fdrp);
			if (sshbuf_len(sockets[i].output) > 0)
				FD_SET(sockets[i].fd, *fdwp);
			break;
		default:
			break;
		}
	}
	deadline = reaper();
	if (parent_alive_interval != 0)
		deadline = (deadline == 0) ? parent_alive_interval :
		    MIN(deadline, parent_alive_interval);
	if (deadline == 0) {
		*tvpp = NULL;
	} else {
		tv.tv_sec = deadline;
		tv.tv_usec = 0;
		*tvpp = &tv;
	}
	return (1);
}

static void
after_select(fd_set *readset, fd_set *writeset)
{
	struct sockaddr_un sunaddr;
	socklen_t slen;
	char buf[1024];
	int len, sock, r;
	u_int i, orig_alloc;
	uid_t euid;
	gid_t egid;

	for (i = 0, orig_alloc = sockets_alloc; i < orig_alloc; i++)
		switch (sockets[i].type) {
		case AUTH_UNUSED:
			break;
		case AUTH_SOCKET:
			if (FD_ISSET(sockets[i].fd, readset)) {
				slen = sizeof(sunaddr);
				sock = accept(sockets[i].fd,
				    (struct sockaddr *)&sunaddr, &slen);
				if (sock < 0) {
					error("accept from AUTH_SOCKET: %s",
					    strerror(errno));
					break;
				}
				if (getpeereid(sock, &euid, &egid) < 0) {
					error("getpeereid %d failed: %s",
					    sock, strerror(errno));
					close(sock);
					break;
				}
				if ((euid != 0) && (getuid() != euid)) {
					error("uid mismatch: "
					    "peer euid %u != uid %u",
					    (u_int) euid, (u_int) getuid());
					close(sock);
					break;
				}
				new_socket(AUTH_CONNECTION, sock);
			}
			break;
		case AUTH_CONNECTION:
			if (sshbuf_len(sockets[i].output) > 0 &&
			    FD_ISSET(sockets[i].fd, writeset)) {
				len = write(sockets[i].fd,
				    sshbuf_ptr(sockets[i].output),
				    sshbuf_len(sockets[i].output));
				if (len == -1 && (errno == EAGAIN ||
				    errno == EINTR))
					continue;
				if (len <= 0) {
					close_socket(&sockets[i]);
					break;
				}
				if ((r = sshbuf_consume(sockets[i].output,
				    len)) != 0)
					fatal("%s: buffer error: %s",
					    __func__, ssh_err(r));
			}
			if (FD_ISSET(sockets[i].fd, readset)) {
				len = read(sockets[i].fd, buf, sizeof(buf));
				if (len == -1 && (errno == EAGAIN ||
				    errno == EINTR))
					continue;
				if (len <= 0) {
					close_socket(&sockets[i]);
					break;
				}
				if ((r = sshbuf_put(sockets[i].input,
				    buf, len)) != 0)
					fatal("%s: buffer error: %s",
					    __func__, ssh_err(r));
				explicit_bzero(buf, sizeof(buf));
				process_message(&sockets[i]);
			}
			break;
		default:
			fatal("Unknown type %d", sockets[i].type);
		}
}

static void
cleanup_socket(void)
{
	if (cleanup_pid != 0 && getpid() != cleanup_pid)
		return;
	debug("%s: cleanup", __func__);
	if (socket_name[0])
		unlink(socket_name);
	if (socket_dir[0])
		rmdir(socket_dir);
}

void
cleanup_exit(int i)
{
	cleanup_socket();
	_exit(i);
}

/*ARGSUSED*/
static void
cleanup_handler(int sig)
{
	cleanup_socket();
#ifdef ENABLE_PKCS11
	pkcs11_terminate();
#endif
	_exit(2);
}

static void
check_parent_exists(void)
{
	/*
	 * If our parent has exited then getppid() will return (pid_t)1,
	 * so testing for that should be safe.
	 */
	if (parent_pid != -1 && getppid() != parent_pid) {
		/* printf("Parent has died - Authentication agent exiting.\n"); */
		cleanup_socket();
		_exit(2);
	}
}

static void
usage(void)
{
	fprintf(stderr,
	    "usage: ssh-agent [-c | -s] [-d] [-a bind_address] [-E fingerprint_hash]\n"
	    "                 [-t life] [command [arg ...]]\n"
	    "       ssh-agent [-c | -s] -k\n");
	exit(1);
}

int
main(int ac, char **av)
{
	int c_flag = 0, d_flag = 0, k_flag = 0, s_flag = 0;
	int sock, fd, ch, result, saved_errno;
	u_int nalloc;
	char *shell, *format, *pidstr, *agentsocket = NULL;
	fd_set *readsetp = NULL, *writesetp = NULL;
	struct rlimit rlim;
	extern int optind;
	extern char *optarg;
	pid_t pid;
	char pidstrbuf[1 + 3 * sizeof pid];
	struct timeval *tvp = NULL;
	size_t len;
	mode_t prev_mask;

	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
	sanitise_stdfd();

	/* drop */
	setegid(getgid());
	setgid(getgid());

#ifdef WITH_OPENSSL
	OpenSSL_add_all_algorithms();
#endif

	while ((ch = getopt(ac, av, "cdksE:a:t:")) != -1) {
		switch (ch) {
		case 'E':
			fingerprint_hash = ssh_digest_alg_by_name(optarg);
			if (fingerprint_hash == -1)
				fatal("Invalid hash algorithm \"%s\"", optarg);
			break;
		case 'c':
			if (s_flag)
				usage();
			c_flag++;
			break;
		case 'k':
			k_flag++;
			break;
		case 's':
			if (c_flag)
				usage();
			s_flag++;
			break;
		case 'd':
			if (d_flag)
				usage();
			d_flag++;
			break;
		case 'a':
			agentsocket = optarg;
			break;
		case 't':
			if ((lifetime = convtime(optarg)) == -1) {
				fprintf(stderr, "Invalid lifetime\n");
				usage();
			}
			break;
		default:
			usage();
		}
	}
	ac -= optind;
	av += optind;

	if (ac > 0 && (c_flag || k_flag || s_flag || d_flag))
		usage();

	if (ac == 0 && !c_flag && !s_flag) {
		shell = getenv("SHELL");
		if (shell != NULL && (len = strlen(shell)) > 2 &&
		    strncmp(shell + len - 3, "csh", 3) == 0)
			c_flag = 1;
	}
	if (k_flag) {
		const char *errstr = NULL;

		pidstr = getenv(SSH_AGENTPID_ENV_NAME);
		if (pidstr == NULL) {
			fprintf(stderr, "%s not set, cannot kill agent\n",
			    SSH_AGENTPID_ENV_NAME);
			exit(1);
		}
		pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
		if (errstr) {
			fprintf(stderr,
			    "%s=\"%s\", which is not a good PID: %s\n",
			    SSH_AGENTPID_ENV_NAME, pidstr, errstr);
			exit(1);
		}
		if (kill(pid, SIGTERM) == -1) {
			perror("kill");
			exit(1);
		}
		format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
		printf(format, SSH_AUTHSOCKET_ENV_NAME);
		printf(format, SSH_AGENTPID_ENV_NAME);
		printf("echo Agent pid %ld killed;\n", (long)pid);
		exit(0);
	}
	parent_pid = getpid();

	if (agentsocket == NULL) {
		/* Create private directory for agent socket */
		mktemp_proto(socket_dir, sizeof(socket_dir));
		if (mkdtemp(socket_dir) == NULL) {
			perror("mkdtemp: private socket dir");
			exit(1);
		}
		snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
		    (long)parent_pid);
	} else {
		/* Try to use specified agent socket */
		socket_dir[0] = '\0';
		strlcpy(socket_name, agentsocket, sizeof socket_name);
	}

	/*
	 * Create socket early so it will exist before command gets run from
	 * the parent.
	 */
	prev_mask = umask(0177);
	sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
	if (sock < 0) {
		/* XXX - unix_listener() calls error() not perror() */
		*socket_name = '\0'; /* Don't unlink any existing file */
		cleanup_exit(1);
	}
	umask(prev_mask);

	/*
	 * Fork, and have the parent execute the command, if any, or present
	 * the socket data.  The child continues as the authentication agent.
	 */
	if (d_flag) {
		log_init(__progname, SYSLOG_LEVEL_DEBUG1, SYSLOG_FACILITY_AUTH, 1);
		format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
		printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
		    SSH_AUTHSOCKET_ENV_NAME);
		printf("echo Agent pid %ld;\n", (long)parent_pid);
		goto skip;
	}
	pid = fork();
	if (pid == -1) {
		perror("fork");
		cleanup_exit(1);
	}
	if (pid != 0) {		/* Parent - execute the given command. */
		close(sock);
		snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
		if (ac == 0) {
			format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
			printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
			    SSH_AUTHSOCKET_ENV_NAME);
			printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
			    SSH_AGENTPID_ENV_NAME);
			printf("echo Agent pid %ld;\n", (long)pid);
			exit(0);
		}
		if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
		    setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
			perror("setenv");
			exit(1);
		}
		execvp(av[0], av);
		perror(av[0]);
		exit(1);
	}
	/* child */
	log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);

	if (setsid() == -1) {
		error("setsid: %s", strerror(errno));
		cleanup_exit(1);
	}

	(void)chdir("/");
	if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
		/* XXX might close listen socket */
		(void)dup2(fd, STDIN_FILENO);
		(void)dup2(fd, STDOUT_FILENO);
		(void)dup2(fd, STDERR_FILENO);
		if (fd > 2)
			close(fd);
	}

	/* deny core dumps, since memory contains unencrypted private keys */
	rlim.rlim_cur = rlim.rlim_max = 0;
	if (setrlimit(RLIMIT_CORE, &rlim) < 0) {
		error("setrlimit RLIMIT_CORE: %s", strerror(errno));
		cleanup_exit(1);
	}

skip:

	cleanup_pid = getpid();

#ifdef ENABLE_PKCS11
	pkcs11_init(0);
#endif
	new_socket(AUTH_SOCKET, sock);
	if (ac > 0)
		parent_alive_interval = 10;
	idtab_init();
	signal(SIGPIPE, SIG_IGN);
	signal(SIGINT, d_flag ? cleanup_handler : SIG_IGN);
	signal(SIGHUP, cleanup_handler);
	signal(SIGTERM, cleanup_handler);
	nalloc = 0;

	while (1) {
		prepare_select(&readsetp, &writesetp, &max_fd, &nalloc, &tvp);
		result = select(max_fd + 1, readsetp, writesetp, NULL, tvp);
		saved_errno = errno;
		if (parent_alive_interval != 0)
			check_parent_exists();
		(void) reaper();	/* remove expired keys */
		if (result < 0) {
			if (saved_errno == EINTR)
				continue;
			fatal("select: %s", strerror(saved_errno));
		} else if (result > 0)
			after_select(readsetp, writesetp);
	}
	/* NOTREACHED */
}