Adding upstream version 1:8.4p1.upstream/1%8.4p1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1549 insertions, 0 deletions

diff --git a/ssh-agent.c b/ssh-agent.c
new file mode 100644
index 0000000..e1fd1f3
--- /dev/null
+++ b/ssh-agent.c
@@ -0,0 +1,1549 @@
+/* $OpenBSD: ssh-agent.c,v 1.264 2020/09/18 08:16:38 djm 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 "includes.h"
+
+#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/resource.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#ifdef HAVE_SYS_TIME_H
+# include <sys/time.h>
+#endif
+#ifdef HAVE_SYS_UN_H
+# include <sys/un.h>
+#endif
+#include "openbsd-compat/sys-queue.h"
+
+#ifdef WITH_OPENSSL
+#include <openssl/evp.h>
+#include "openbsd-compat/openssl-compat.h"
+#endif
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#ifdef HAVE_PATHS_H
+# include <paths.h>
+#endif
+#ifdef HAVE_POLL_H
+# include <poll.h>
+#endif
+#include <signal.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <string.h>
+#include <unistd.h>
+#ifdef HAVE_UTIL_H
+# include <util.h>
+#endif
+
+#include "xmalloc.h"
+#include "ssh.h"
+#include "ssh2.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"
+#include "match.h"
+#include "msg.h"
+#include "ssherr.h"
+#include "pathnames.h"
+#include "ssh-pkcs11.h"
+#include "sk-api.h"
+
+#ifndef DEFAULT_ALLOWED_PROVIDERS
+# define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/local/lib*/*"
+#endif
+
+/* Maximum accepted message length */
+#define AGENT_MAX_LEN	(256*1024)
+/* Maximum bytes to read from client socket */
+#define AGENT_RBUF_LEN	(4096)
+
+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;
+	char *sk_provider;
+} Identity;
+
+struct idtable {
+	int nentries;
+	TAILQ_HEAD(idqueue, identity) idlist;
+};
+
+/* private key table */
+struct idtable *idtab;
+
+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];
+
+/* Pattern-list of allowed PKCS#11/Security key paths */
+static char *allowed_providers;
+
+/* locking */
+#define LOCK_SIZE	32
+#define LOCK_SALT_SIZE	16
+#define LOCK_ROUNDS	1
+int locked = 0;
+u_char lock_pwhash[LOCK_SIZE];
+u_char lock_salt[LOCK_SALT_SIZE];
+
+extern char *__progname;
+
+/* Default lifetime in seconds (0 == forever) */
+static long lifetime = 0;
+
+static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
+
+/* Refuse signing of non-SSH messages for web-origin FIDO keys */
+static int restrict_websafe = 1;
+
+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)
+{
+	idtab = xcalloc(1, sizeof(*idtab));
+	TAILQ_INIT(&idtab->idlist);
+	idtab->nentries = 0;
+}
+
+static void
+free_identity(Identity *id)
+{
+	sshkey_free(id->key);
+	free(id->provider);
+	free(id->comment);
+	free(id->sk_provider);
+	free(id);
+}
+
+/* return matching private key for given public key */
+static Identity *
+lookup_identity(struct sshkey *key)
+{
+	Identity *id;
+
+	TAILQ_FOREACH(id, &idtab->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 (p != NULL &&
+	    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)
+{
+	Identity *id;
+	struct sshbuf *msg;
+	int r;
+
+	if ((msg = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
+	if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
+	    (r = sshbuf_put_u32(msg, idtab->nentries)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	TAILQ_FOREACH(id, &idtab->idlist, next) {
+		if ((r = sshkey_puts_opts(id->key, msg, SSHKEY_SERIALIZE_INFO))
+		     != 0 ||
+		    (r = sshbuf_put_cstring(msg, id->comment)) != 0) {
+			error("%s: put key/comment: %s", __func__,
+			    ssh_err(r));
+			continue;
+		}
+	}
+	if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	sshbuf_free(msg);
+}
+
+
+static char *
+agent_decode_alg(struct sshkey *key, u_int flags)
+{
+	if (key->type == KEY_RSA) {
+		if (flags & SSH_AGENT_RSA_SHA2_256)
+			return "rsa-sha2-256";
+		else if (flags & SSH_AGENT_RSA_SHA2_512)
+			return "rsa-sha2-512";
+	} else if (key->type == KEY_RSA_CERT) {
+		if (flags & SSH_AGENT_RSA_SHA2_256)
+			return "rsa-sha2-256-cert-v01@openssh.com";
+		else if (flags & SSH_AGENT_RSA_SHA2_512)
+			return "rsa-sha2-512-cert-v01@openssh.com";
+	}
+	return NULL;
+}
+
+/*
+ * This function inspects a message to be signed by a FIDO key that has a
+ * web-like application string (i.e. one that does not begin with "ssh:".
+ * It checks that the message is one of those expected for SSH operations
+ * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges
+ * for the web.
+ */
+static int
+check_websafe_message_contents(struct sshkey *key,
+    const u_char *msg, size_t len)
+{
+	int matched = 0;
+	struct sshbuf *b;
+	u_char m, n;
+	char *cp1 = NULL, *cp2 = NULL;
+	int r;
+	struct sshkey *mkey = NULL;
+
+	if ((b = sshbuf_from(msg, len)) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+
+	/* SSH userauth request */
+	if ((r = sshbuf_get_string_direct(b, NULL, NULL)) == 0 && /* sess_id */
+	    (r = sshbuf_get_u8(b, &m)) == 0 && /* SSH2_MSG_USERAUTH_REQUEST */
+	    (r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* server user */
+	    (r = sshbuf_get_cstring(b, &cp1, NULL)) == 0 && /* service */
+	    (r = sshbuf_get_cstring(b, &cp2, NULL)) == 0 && /* method */
+	    (r = sshbuf_get_u8(b, &n)) == 0 && /* sig-follows */
+	    (r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* alg */
+	    (r = sshkey_froms(b, &mkey)) == 0 && /* key */
+	    sshbuf_len(b) == 0) {
+		debug("%s: parsed userauth", __func__);
+		if (m == SSH2_MSG_USERAUTH_REQUEST && n == 1 &&
+		    strcmp(cp1, "ssh-connection") == 0 &&
+		    strcmp(cp2, "publickey") == 0 &&
+		    sshkey_equal(key, mkey)) {
+			debug("%s: well formed userauth", __func__);
+			matched = 1;
+		}
+	}
+	free(cp1);
+	free(cp2);
+	sshkey_free(mkey);
+	sshbuf_free(b);
+	if (matched)
+		return 1;
+
+	if ((b = sshbuf_from(msg, len)) == NULL)
+		fatal("%s: sshbuf_new", __func__);
+	cp1 = cp2 = NULL;
+	mkey = NULL;
+
+	/* SSHSIG */
+	if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) == 0 &&
+	    (r = sshbuf_consume(b, 6)) == 0 &&
+	    (r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* namespace */
+	    (r = sshbuf_get_string_direct(b, NULL, NULL)) == 0 && /* reserved */
+	    (r = sshbuf_get_cstring(b, NULL, NULL)) == 0 && /* hashalg */
+	    (r = sshbuf_get_string_direct(b, NULL, NULL)) == 0 && /* H(msg) */
+	    sshbuf_len(b) == 0) {
+		debug("%s: parsed sshsig", __func__);
+		matched = 1;
+	}
+
+	sshbuf_free(b);
+	if (matched)
+		return 1;
+
+	/* XXX CA signature operation */
+
+	error("web-origin key attempting to sign non-SSH message");
+	return 0;
+}
+
+/* ssh2 only */
+static void
+process_sign_request2(SocketEntry *e)
+{
+	const u_char *data;
+	u_char *signature = NULL;
+	size_t dlen, slen = 0;
+	u_int compat = 0, flags;
+	int r, ok = -1;
+	char *fp = NULL;
+	struct sshbuf *msg;
+	struct sshkey *key = NULL;
+	struct identity *id;
+	struct notifier_ctx *notifier = NULL;
+
+	if ((msg = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
+	if ((r = sshkey_froms(e->request, &key)) != 0 ||
+	    (r = sshbuf_get_string_direct(e->request, &data, &dlen)) != 0 ||
+	    (r = sshbuf_get_u32(e->request, &flags)) != 0) {
+		error("%s: couldn't parse request: %s", __func__, ssh_err(r));
+		goto send;
+	}
+
+	if ((id = lookup_identity(key)) == 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 (sshkey_is_sk(id->key)) {
+		if (strncmp(id->key->sk_application, "ssh:", 4) != 0 &&
+		    !check_websafe_message_contents(key, data, dlen)) {
+			/* error already logged */
+			goto send;
+		}
+		if ((id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD)) {
+			if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT,
+			    SSH_FP_DEFAULT)) == NULL)
+				fatal("%s: fingerprint failed", __func__);
+			notifier = notify_start(0,
+			    "Confirm user presence for key %s %s",
+			    sshkey_type(id->key), fp);
+		}
+	}
+	/* XXX support PIN required FIDO keys */
+	if ((r = sshkey_sign(id->key, &signature, &slen,
+	    data, dlen, agent_decode_alg(key, flags),
+	    id->sk_provider, NULL, compat)) != 0) {
+		error("%s: sshkey_sign: %s", __func__, ssh_err(r));
+		goto send;
+	}
+	/* Success */
+	ok = 0;
+ send:
+	notify_complete(notifier);
+	sshkey_free(key);
+	free(fp);
+	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(signature);
+}
+
+/* shared */
+static void
+process_remove_identity(SocketEntry *e)
+{
+	int r, success = 0;
+	struct sshkey *key = NULL;
+	Identity *id;
+
+	if ((r = sshkey_froms(e->request, &key)) != 0) {
+		error("%s: get key: %s", __func__, ssh_err(r));
+		goto done;
+	}
+	if ((id = lookup_identity(key)) == NULL) {
+		debug("%s: key not found", __func__);
+		goto done;
+	}
+	/* We have this key, free it. */
+	if (idtab->nentries < 1)
+		fatal("%s: internal error: nentries %d",
+		    __func__, idtab->nentries);
+	TAILQ_REMOVE(&idtab->idlist, id, next);
+	free_identity(id);
+	idtab->nentries--;
+	sshkey_free(key);
+	success = 1;
+ done:
+	send_status(e, success);
+}
+
+static void
+process_remove_all_identities(SocketEntry *e)
+{
+	Identity *id;
+
+	/* Loop over all identities and clear the keys. */
+	for (id = TAILQ_FIRST(&idtab->idlist); id;
+	    id = TAILQ_FIRST(&idtab->idlist)) {
+		TAILQ_REMOVE(&idtab->idlist, id, next);
+		free_identity(id);
+	}
+
+	/* Mark that there are no identities. */
+	idtab->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;
+
+	for (id = TAILQ_FIRST(&idtab->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(&idtab->idlist, id, next);
+			free_identity(id);
+			idtab->nentries--;
+		} else
+			deadline = (deadline == 0) ? id->death :
+			    MINIMUM(deadline, id->death);
+	}
+	if (deadline == 0 || deadline <= now)
+		return 0;
+	else
+		return (deadline - now);
+}
+
+static void
+process_add_identity(SocketEntry *e)
+{
+	Identity *id;
+	int success = 0, confirm = 0;
+	u_int seconds = 0, maxsign;
+	char *fp, *comment = NULL, *ext_name = NULL, *sk_provider = NULL;
+	char canonical_provider[PATH_MAX];
+	time_t death = 0;
+	struct sshkey *k = NULL;
+	u_char ctype;
+	int r = SSH_ERR_INTERNAL_ERROR;
+
+	if ((r = sshkey_private_deserialize(e->request, &k)) != 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;
+		case SSH_AGENT_CONSTRAIN_MAXSIGN:
+			if ((r = sshbuf_get_u32(e->request, &maxsign)) != 0) {
+				error("%s: bad maxsign constraint: %s",
+				    __func__, ssh_err(r));
+				goto err;
+			}
+			if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) {
+				error("%s: cannot enable maxsign: %s",
+				    __func__, ssh_err(r));
+				goto err;
+			}
+			break;
+		case SSH_AGENT_CONSTRAIN_EXTENSION:
+			if ((r = sshbuf_get_cstring(e->request,
+			    &ext_name, NULL)) != 0) {
+				error("%s: cannot parse extension: %s",
+				    __func__, ssh_err(r));
+				goto err;
+			}
+			debug("%s: constraint ext %s", __func__, ext_name);
+			if (strcmp(ext_name, "sk-provider@openssh.com") == 0) {
+				if (sk_provider != NULL) {
+					error("%s already set", ext_name);
+					goto err;
+				}
+				if ((r = sshbuf_get_cstring(e->request,
+				    &sk_provider, NULL)) != 0) {
+					error("%s: cannot parse %s: %s",
+					    __func__, ext_name, ssh_err(r));
+					goto err;
+				}
+			} else {
+				error("%s: unsupported constraint \"%s\"",
+				    __func__, ext_name);
+				goto err;
+			}
+			free(ext_name);
+			break;
+		default:
+			error("%s: Unknown constraint %d", __func__, ctype);
+ err:
+			free(sk_provider);
+			free(ext_name);
+			sshbuf_reset(e->request);
+			free(comment);
+			sshkey_free(k);
+			goto send;
+		}
+	}
+	if (sk_provider != NULL) {
+		if (!sshkey_is_sk(k)) {
+			error("Cannot add provider: %s is not an "
+			    "authenticator-hosted key", sshkey_type(k));
+			free(sk_provider);
+			goto send;
+		}
+		if (strcasecmp(sk_provider, "internal") == 0) {
+			debug("%s: internal provider", __func__);
+		} else {
+			if (realpath(sk_provider, canonical_provider) == NULL) {
+				verbose("failed provider \"%.100s\": "
+				    "realpath: %s", sk_provider,
+				    strerror(errno));
+				free(sk_provider);
+				goto send;
+			}
+			free(sk_provider);
+			sk_provider = xstrdup(canonical_provider);
+			if (match_pattern_list(sk_provider,
+			    allowed_providers, 0) != 1) {
+				error("Refusing add key: "
+				    "provider %s not allowed", sk_provider);
+				free(sk_provider);
+				goto send;
+			}
+		}
+	}
+	if ((r = sshkey_shield_private(k)) != 0) {
+		error("%s: shield private key: %s", __func__, ssh_err(r));
+		goto err;
+	}
+
+	success = 1;
+	if (lifetime && !death)
+		death = monotime() + lifetime;
+	if ((id = lookup_identity(k)) == NULL) {
+		id = xcalloc(1, sizeof(Identity));
+		TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
+		/* Increment the number of identities. */
+		idtab->nentries++;
+	} else {
+		/* key state might have been updated */
+		sshkey_free(id->key);
+		free(id->comment);
+		free(id->sk_provider);
+	}
+	id->key = k;
+	id->comment = comment;
+	id->death = death;
+	id->confirm = confirm;
+	id->sk_provider = sk_provider;
+
+	if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT,
+	    SSH_FP_DEFAULT)) == NULL)
+		fatal("%s: sshkey_fingerprint failed", __func__);
+	debug("%s: add %s %s \"%.100s\" (life: %u) (confirm: %u) "
+	    "(provider: %s)", __func__, sshkey_ssh_name(k), fp, comment,
+	    seconds, confirm, sk_provider == NULL ? "none" : sk_provider);
+	free(fp);
+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, delay;
+	char *passwd;
+	u_char passwdhash[LOCK_SIZE];
+	static u_int fail_count = 0;
+	size_t pwlen;
+
+	/*
+	 * This is deliberately fatal: the user has requested that we lock,
+	 * but we can't parse their request properly. The only safe thing to
+	 * do is abort.
+	 */
+	if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	if (pwlen == 0) {
+		debug("empty password not supported");
+	} else if (locked && !lock) {
+		if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
+		    passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
+			fatal("bcrypt_pbkdf");
+		if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
+			debug("agent unlocked");
+			locked = 0;
+			fail_count = 0;
+			explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
+			success = 1;
+		} else {
+			/* delay in 0.1s increments up to 10s */
+			if (fail_count < 100)
+				fail_count++;
+			delay = 100000 * fail_count;
+			debug("unlock failed, delaying %0.1lf seconds",
+			    (double)delay/1000000);
+			usleep(delay);
+		}
+		explicit_bzero(passwdhash, sizeof(passwdhash));
+	} else if (!locked && lock) {
+		debug("agent locked");
+		locked = 1;
+		arc4random_buf(lock_salt, sizeof(lock_salt));
+		if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
+		    lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
+			fatal("bcrypt_pbkdf");
+		success = 1;
+	}
+	freezero(passwd, pwlen);
+	send_status(e, success);
+}
+
+static void
+no_identities(SocketEntry *e)
+{
+	struct sshbuf *msg;
+	int r;
+
+	if ((msg = sshbuf_new()) == NULL)
+		fatal("%s: sshbuf_new failed", __func__);
+	if ((r = sshbuf_put_u8(msg, 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 = NULL, canonical_provider[PATH_MAX];
+	char **comments = NULL;
+	int r, i, count = 0, success = 0, confirm = 0;
+	u_int seconds;
+	time_t death = 0;
+	u_char type;
+	struct sshkey **keys = NULL, *k;
+	Identity *id;
+
+	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
+		error("%s: buffer error: %s", __func__, ssh_err(r));
+		goto send;
+	}
+
+	while (sshbuf_len(e->request)) {
+		if ((r = sshbuf_get_u8(e->request, &type)) != 0) {
+			error("%s: buffer error: %s", __func__, ssh_err(r));
+			goto send;
+		}
+		switch (type) {
+		case SSH_AGENT_CONSTRAIN_LIFETIME:
+			if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
+				error("%s: buffer error: %s",
+				    __func__, ssh_err(r));
+				goto send;
+			}
+			death = monotime() + seconds;
+			break;
+		case SSH_AGENT_CONSTRAIN_CONFIRM:
+			confirm = 1;
+			break;
+		default:
+			error("%s: Unknown constraint type %d", __func__, type);
+			goto send;
+		}
+	}
+	if (realpath(provider, canonical_provider) == NULL) {
+		verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
+		    provider, strerror(errno));
+		goto send;
+	}
+	if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
+		verbose("refusing PKCS#11 add of \"%.100s\": "
+		    "provider not allowed", canonical_provider);
+		goto send;
+	}
+	debug("%s: add %.100s", __func__, canonical_provider);
+	if (lifetime && !death)
+		death = monotime() + lifetime;
+
+	count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments);
+	for (i = 0; i < count; i++) {
+		k = keys[i];
+		if (lookup_identity(k) == NULL) {
+			id = xcalloc(1, sizeof(Identity));
+			id->key = k;
+			keys[i] = NULL; /* transferred */
+			id->provider = xstrdup(canonical_provider);
+			if (*comments[i] != '\0') {
+				id->comment = comments[i];
+				comments[i] = NULL; /* transferred */
+			} else {
+				id->comment = xstrdup(canonical_provider);
+			}
+			id->death = death;
+			id->confirm = confirm;
+			TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
+			idtab->nentries++;
+			success = 1;
+		}
+		sshkey_free(keys[i]);
+		free(comments[i]);
+	}
+send:
+	free(pin);
+	free(provider);
+	free(keys);
+	free(comments);
+	send_status(e, success);
+}
+
+static void
+process_remove_smartcard_key(SocketEntry *e)
+{
+	char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
+	int r, success = 0;
+	Identity *id, *nxt;
+
+	if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
+	    (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) {
+		error("%s: buffer error: %s", __func__, ssh_err(r));
+		goto send;
+	}
+	free(pin);
+
+	if (realpath(provider, canonical_provider) == NULL) {
+		verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
+		    provider, strerror(errno));
+		goto send;
+	}
+
+	debug("%s: remove %.100s", __func__, canonical_provider);
+	for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
+		nxt = TAILQ_NEXT(id, next);
+		/* Skip file--based keys */
+		if (id->provider == NULL)
+			continue;
+		if (!strcmp(canonical_provider, id->provider)) {
+			TAILQ_REMOVE(&idtab->idlist, id, next);
+			free_identity(id);
+			idtab->nentries--;
+		}
+	}
+	if (pkcs11_del_provider(canonical_provider) == 0)
+		success = 1;
+	else
+		error("%s: pkcs11_del_provider failed", __func__);
+send:
+	free(provider);
+	send_status(e, success);
+}
+#endif /* ENABLE_PKCS11 */
+
+/*
+ * dispatch incoming message.
+ * returns 1 on success, 0 for incomplete messages or -1 on error.
+ */
+static int
+process_message(u_int socknum)
+{
+	u_int msg_len;
+	u_char type;
+	const u_char *cp;
+	int r;
+	SocketEntry *e;
+
+	if (socknum >= sockets_alloc) {
+		fatal("%s: socket number %u >= allocated %u",
+		    __func__, socknum, sockets_alloc);
+	}
+	e = &sockets[socknum];
+
+	if (sshbuf_len(e->input) < 5)
+		return 0;		/* Incomplete message header. */
+	cp = sshbuf_ptr(e->input);
+	msg_len = PEEK_U32(cp);
+	if (msg_len > AGENT_MAX_LEN) {
+		debug("%s: socket %u (fd=%d) message too long %u > %u",
+		    __func__, socknum, e->fd, msg_len, AGENT_MAX_LEN);
+		return -1;
+	}
+	if (sshbuf_len(e->input) < msg_len + 4)
+		return 0;		/* Incomplete message body. */
+
+	/* 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) {
+		if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
+		    r == SSH_ERR_STRING_TOO_LARGE) {
+			debug("%s: buffer error: %s", __func__, ssh_err(r));
+			return -1;
+		}
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	}
+
+	debug("%s: socket %u (fd=%d) type %d", __func__, socknum, e->fd, type);
+
+	/* check whether agent is locked */
+	if (locked && type != SSH_AGENTC_UNLOCK) {
+		sshbuf_reset(e->request);
+		switch (type) {
+		case SSH2_AGENTC_REQUEST_IDENTITIES:
+			/* send empty lists */
+			no_identities(e);
+			break;
+		default:
+			/* send a fail message for all other request types */
+			send_status(e, 0);
+		}
+		return 1;
+	}
+
+	switch (type) {
+	case SSH_AGENTC_LOCK:
+	case SSH_AGENTC_UNLOCK:
+		process_lock_agent(e, type == SSH_AGENTC_LOCK);
+		break;
+	case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
+		process_remove_all_identities(e); /* safe for !WITH_SSH1 */
+		break;
+	/* ssh2 */
+	case SSH2_AGENTC_SIGN_REQUEST:
+		process_sign_request2(e);
+		break;
+	case SSH2_AGENTC_REQUEST_IDENTITIES:
+		process_request_identities(e);
+		break;
+	case SSH2_AGENTC_ADD_IDENTITY:
+	case SSH2_AGENTC_ADD_ID_CONSTRAINED:
+		process_add_identity(e);
+		break;
+	case SSH2_AGENTC_REMOVE_IDENTITY:
+		process_remove_identity(e);
+		break;
+	case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
+		process_remove_all_identities(e);
+		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;
+	}
+	return 1;
+}
+
+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 = xreallocarray(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
+handle_socket_read(u_int socknum)
+{
+	struct sockaddr_un sunaddr;
+	socklen_t slen;
+	uid_t euid;
+	gid_t egid;
+	int fd;
+
+	slen = sizeof(sunaddr);
+	fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
+	if (fd == -1) {
+		error("accept from AUTH_SOCKET: %s", strerror(errno));
+		return -1;
+	}
+	if (getpeereid(fd, &euid, &egid) == -1) {
+		error("getpeereid %d failed: %s", fd, strerror(errno));
+		close(fd);
+		return -1;
+	}
+	if ((euid != 0) && (getuid() != euid)) {
+		error("uid mismatch: peer euid %u != uid %u",
+		    (u_int) euid, (u_int) getuid());
+		close(fd);
+		return -1;
+	}
+	new_socket(AUTH_CONNECTION, fd);
+	return 0;
+}
+
+static int
+handle_conn_read(u_int socknum)
+{
+	char buf[AGENT_RBUF_LEN];
+	ssize_t len;
+	int r;
+
+	if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
+		if (len == -1) {
+			if (errno == EAGAIN || errno == EINTR)
+				return 0;
+			error("%s: read error on socket %u (fd %d): %s",
+			    __func__, socknum, sockets[socknum].fd,
+			    strerror(errno));
+		}
+		return -1;
+	}
+	if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	explicit_bzero(buf, sizeof(buf));
+	for (;;) {
+		if ((r = process_message(socknum)) == -1)
+			return -1;
+		else if (r == 0)
+			break;
+	}
+	return 0;
+}
+
+static int
+handle_conn_write(u_int socknum)
+{
+	ssize_t len;
+	int r;
+
+	if (sshbuf_len(sockets[socknum].output) == 0)
+		return 0; /* shouldn't happen */
+	if ((len = write(sockets[socknum].fd,
+	    sshbuf_ptr(sockets[socknum].output),
+	    sshbuf_len(sockets[socknum].output))) <= 0) {
+		if (len == -1) {
+			if (errno == EAGAIN || errno == EINTR)
+				return 0;
+			error("%s: read error on socket %u (fd %d): %s",
+			    __func__, socknum, sockets[socknum].fd,
+			    strerror(errno));
+		}
+		return -1;
+	}
+	if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
+		fatal("%s: buffer error: %s", __func__, ssh_err(r));
+	return 0;
+}
+
+static void
+after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds)
+{
+	size_t i;
+	u_int socknum, activefds = npfd;
+
+	for (i = 0; i < npfd; i++) {
+		if (pfd[i].revents == 0)
+			continue;
+		/* Find sockets entry */
+		for (socknum = 0; socknum < sockets_alloc; socknum++) {
+			if (sockets[socknum].type != AUTH_SOCKET &&
+			    sockets[socknum].type != AUTH_CONNECTION)
+				continue;
+			if (pfd[i].fd == sockets[socknum].fd)
+				break;
+		}
+		if (socknum >= sockets_alloc) {
+			error("%s: no socket for fd %d", __func__, pfd[i].fd);
+			continue;
+		}
+		/* Process events */
+		switch (sockets[socknum].type) {
+		case AUTH_SOCKET:
+			if ((pfd[i].revents & (POLLIN|POLLERR)) == 0)
+				break;
+			if (npfd > maxfds) {
+				debug3("out of fds (active %u >= limit %u); "
+				    "skipping accept", activefds, maxfds);
+				break;
+			}
+			if (handle_socket_read(socknum) == 0)
+				activefds++;
+			break;
+		case AUTH_CONNECTION:
+			if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 &&
+			    handle_conn_read(socknum) != 0) {
+				goto close_sock;
+			}
+			if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
+			    handle_conn_write(socknum) != 0) {
+ close_sock:
+				if (activefds == 0)
+					fatal("activefds == 0 at close_sock");
+				close_socket(&sockets[socknum]);
+				activefds--;
+				break;
+			}
+			break;
+		default:
+			break;
+		}
+	}
+}
+
+static int
+prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds)
+{
+	struct pollfd *pfd = *pfdp;
+	size_t i, j, npfd = 0;
+	time_t deadline;
+	int r;
+
+	/* Count active sockets */
+	for (i = 0; i < sockets_alloc; i++) {
+		switch (sockets[i].type) {
+		case AUTH_SOCKET:
+		case AUTH_CONNECTION:
+			npfd++;
+			break;
+		case AUTH_UNUSED:
+			break;
+		default:
+			fatal("Unknown socket type %d", sockets[i].type);
+			break;
+		}
+	}
+	if (npfd != *npfdp &&
+	    (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
+		fatal("%s: recallocarray failed", __func__);
+	*pfdp = pfd;
+	*npfdp = npfd;
+
+	for (i = j = 0; i < sockets_alloc; i++) {
+		switch (sockets[i].type) {
+		case AUTH_SOCKET:
+			if (npfd > maxfds) {
+				debug3("out of fds (active %zu >= limit %u); "
+				    "skipping arming listener", npfd, maxfds);
+				break;
+			}
+			pfd[j].fd = sockets[i].fd;
+			pfd[j].revents = 0;
+			pfd[j].events = POLLIN;
+			j++;
+			break;
+		case AUTH_CONNECTION:
+			pfd[j].fd = sockets[i].fd;
+			pfd[j].revents = 0;
+			/*
+			 * Only prepare to read if we can handle a full-size
+			 * input read buffer and enqueue a max size reply..
+			 */
+			if ((r = sshbuf_check_reserve(sockets[i].input,
+			    AGENT_RBUF_LEN)) == 0 &&
+			    (r = sshbuf_check_reserve(sockets[i].output,
+			     AGENT_MAX_LEN)) == 0)
+				pfd[j].events = POLLIN;
+			else if (r != SSH_ERR_NO_BUFFER_SPACE) {
+				fatal("%s: buffer error: %s",
+				    __func__, ssh_err(r));
+			}
+			if (sshbuf_len(sockets[i].output) > 0)
+				pfd[j].events |= POLLOUT;
+			j++;
+			break;
+		default:
+			break;
+		}
+	}
+	deadline = reaper();
+	if (parent_alive_interval != 0)
+		deadline = (deadline == 0) ? parent_alive_interval :
+		    MINIMUM(deadline, parent_alive_interval);
+	if (deadline == 0) {
+		*timeoutp = -1; /* INFTIM */
+	} else {
+		if (deadline > INT_MAX / 1000)
+			*timeoutp = INT_MAX / 1000;
+		else
+			*timeoutp = deadline * 1000;
+	}
+	return (1);
+}
+
+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] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
+	    "                 [-P allowed_providers] [-t life]\n"
+	    "       ssh-agent [-a bind_address] [-E fingerprint_hash] [-P allowed_providers]\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, D_flag = 0, k_flag = 0, s_flag = 0;
+	int sock, fd, ch, result, saved_errno;
+	char *shell, *format, *pidstr, *agentsocket = NULL;
+#ifdef HAVE_SETRLIMIT
+	struct rlimit rlim;
+#endif
+	extern int optind;
+	extern char *optarg;
+	pid_t pid;
+	char pidstrbuf[1 + 3 * sizeof pid];
+	size_t len;
+	mode_t prev_mask;
+	int timeout = -1; /* INFTIM */
+	struct pollfd *pfd = NULL;
+	size_t npfd = 0;
+	u_int maxfds;
+
+	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
+	sanitise_stdfd();
+
+	/* drop */
+	setegid(getgid());
+	setgid(getgid());
+
+	platform_disable_tracing(0);	/* strict=no */
+
+#ifdef RLIMIT_NOFILE
+	if (getrlimit(RLIMIT_NOFILE, &rlim) == -1)
+		fatal("%s: getrlimit: %s", __progname, strerror(errno));
+#endif
+
+	__progname = ssh_get_progname(av[0]);
+	seed_rng();
+
+	while ((ch = getopt(ac, av, "cDdksE:a:O:P: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 'O':
+			if (strcmp(optarg, "no-restrict-websafe") == 0)
+				restrict_websafe  = 0;
+			else
+				fatal("Unknown -O option");
+			break;
+		case 'P':
+			if (allowed_providers != NULL)
+				fatal("-P option already specified");
+			allowed_providers = xstrdup(optarg);
+			break;
+		case 's':
+			if (c_flag)
+				usage();
+			s_flag++;
+			break;
+		case 'd':
+			if (d_flag || D_flag)
+				usage();
+			d_flag++;
+			break;
+		case 'D':
+			if (d_flag || 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 || D_flag))
+		usage();
+
+	if (allowed_providers == NULL)
+		allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS);
+
+	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);
+	}
+
+	/*
+	 * Minimum file descriptors:
+	 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) +
+	 * a few spare for libc / stack protectors / sanitisers, etc.
+	 */
+#define SSH_AGENT_MIN_FDS (3+1+1+1+4)
+	if (rlim.rlim_cur < SSH_AGENT_MIN_FDS)
+		fatal("%s: file descriptor rlimit %lld too low (minimum %u)",
+		    __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS);
+	maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS;
+
+	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 || d_flag) {
+		log_init(__progname,
+		    d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
+		    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);
+		fflush(stdout);
+		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);
+	}
+
+#ifdef HAVE_SETRLIMIT
+	/* deny core dumps, since memory contains unencrypted private keys */
+	rlim.rlim_cur = rlim.rlim_max = 0;
+	if (setrlimit(RLIMIT_CORE, &rlim) == -1) {
+		error("setrlimit RLIMIT_CORE: %s", strerror(errno));
+		cleanup_exit(1);
+	}
+#endif
+
+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();
+	ssh_signal(SIGPIPE, SIG_IGN);
+	ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
+	ssh_signal(SIGHUP, cleanup_handler);
+	ssh_signal(SIGTERM, cleanup_handler);
+
+	if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
+		fatal("%s: pledge: %s", __progname, strerror(errno));
+	platform_pledge_agent();
+
+	while (1) {
+		prepare_poll(&pfd, &npfd, &timeout, maxfds);
+		result = poll(pfd, npfd, timeout);
+		saved_errno = errno;
+		if (parent_alive_interval != 0)
+			check_parent_exists();
+		(void) reaper();	/* remove expired keys */
+		if (result == -1) {
+			if (saved_errno == EINTR)
+				continue;
+			fatal("poll: %s", strerror(saved_errno));
+		} else if (result > 0)
+			after_poll(pfd, npfd, maxfds);
+	}
+	/* NOTREACHED */
+}