ssh-agent.c - security/openssh-library - Rivoreo Source Code Repositories

 /*	$OpenBSD: ssh-agent.c,v 1.36 2000/09/15 07:13:49 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".
  *
  * SSH2 implementation,
  * Copyright (c) 2000 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"
 RCSID("$OpenBSD: ssh-agent.c,v 1.36 2000/09/15 07:13:49 deraadt Exp $");

 #include "ssh.h"
 #include "rsa.h"
 #include "buffer.h"
 #include "bufaux.h"
 #include "xmalloc.h"
 #include "packet.h"
 #include "getput.h"
 #include "mpaux.h"

 #include <openssl/evp.h>
 #include <openssl/md5.h>
 #include <openssl/dsa.h>
 #include <openssl/rsa.h>
 #include "key.h"
 #include "authfd.h"
 #include "dsa.h"
 #include "kex.h"

 typedef struct {
 	int fd;
 	enum {
 		AUTH_UNUSED, AUTH_SOCKET, AUTH_CONNECTION
 	} type;
 	Buffer input;
 	Buffer output;
 } SocketEntry;

 unsigned int sockets_alloc = 0;
 SocketEntry *sockets = NULL;

 typedef struct {
 	Key *key;
 	char *comment;
 } Identity;

 typedef struct {
 	int nentries;
 	Identity *identities;
 } 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;

 /* pathname and directory for AUTH_SOCKET */
 char socket_name[1024];
 char socket_dir[1024];

 #ifdef HAVE___PROGNAME
 extern char *__progname;
 #else /* HAVE___PROGNAME */
 static const char *__progname = "ssh-agent";
 #endif /* HAVE___PROGNAME */

 void
 idtab_init(void)
 {
 	int i;
 	for (i = 0; i <=2; i++){
 		idtable[i].identities = NULL;
 		idtable[i].nentries = 0;
 	}
 }

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

 /* return matching private key for given public key */
 Key *
 lookup_private_key(Key *key, int *idx, int version)
 {
 	int i;
 	Idtab *tab = idtab_lookup(version);
 	for (i = 0; i < tab->nentries; i++) {
 		if (key_equal(key, tab->identities[i].key)) {
 			if (idx != NULL)
 				*idx = i;
 			return tab->identities[i].key;
 		}
 	}
 	return NULL;
 }

 /* send list of supported public keys to 'client' */
 void
 process_request_identities(SocketEntry *e, int version)
 {
 	Idtab *tab = idtab_lookup(version);
 	Buffer msg;
 	int i;

 	buffer_init(&msg);
 	buffer_put_char(&msg, (version == 1) ?
 	    SSH_AGENT_RSA_IDENTITIES_ANSWER : SSH2_AGENT_IDENTITIES_ANSWER);
 	buffer_put_int(&msg, tab->nentries);
 	for (i = 0; i < tab->nentries; i++) {
 		Identity *id = &tab->identities[i];
 		if (id->key->type == KEY_RSA) {
 			buffer_put_int(&msg, BN_num_bits(id->key->rsa->n));
 			buffer_put_bignum(&msg, id->key->rsa->e);
 			buffer_put_bignum(&msg, id->key->rsa->n);
 		} else {
 			unsigned char *blob;
 			unsigned int blen;
 			dsa_make_key_blob(id->key, &blob, &blen);
 			buffer_put_string(&msg, blob, blen);
 			xfree(blob);
 		}
 		buffer_put_cstring(&msg, id->comment);
 	}
 	buffer_put_int(&e->output, buffer_len(&msg));
 	buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
 	buffer_free(&msg);
 }

 /* ssh1 only */
 void
 process_authentication_challenge1(SocketEntry *e)
 {
 	Key *key, *private;
 	BIGNUM *challenge;
 	int i, len;
 	Buffer msg;
 	MD5_CTX md;
 	unsigned char buf[32], mdbuf[16], session_id[16];
 	unsigned int response_type;

 	buffer_init(&msg);
 	key = key_new(KEY_RSA);
 	challenge = BN_new();

 	buffer_get_int(&e->input);				/* ignored */
 	buffer_get_bignum(&e->input, key->rsa->e);
 	buffer_get_bignum(&e->input, key->rsa->n);
 	buffer_get_bignum(&e->input, challenge);

 	/* Only protocol 1.1 is supported */
 	if (buffer_len(&e->input) == 0)
 		goto failure;
 	buffer_get(&e->input, (char *) session_id, 16);
 	response_type = buffer_get_int(&e->input);
 	if (response_type != 1)
 		goto failure;

 	private = lookup_private_key(key, NULL, 1);
 	if (private != NULL) {
 		/* Decrypt the challenge using the private key. */
 		rsa_private_decrypt(challenge, challenge, private->rsa);

 		/* The response is MD5 of decrypted challenge plus session id. */
 		len = BN_num_bytes(challenge);
 		if (len <= 0 || len > 32) {
 			log("process_authentication_challenge: bad challenge length %d", len);
 			goto failure;
 		}
 		memset(buf, 0, 32);
 		BN_bn2bin(challenge, buf + 32 - len);
 		MD5_Init(&md);
 		MD5_Update(&md, buf, 32);
 		MD5_Update(&md, session_id, 16);
 		MD5_Final(mdbuf, &md);

 		/* Send the response. */
 		buffer_put_char(&msg, SSH_AGENT_RSA_RESPONSE);
 		for (i = 0; i < 16; i++)
 			buffer_put_char(&msg, mdbuf[i]);
 		goto send;
 	}

 failure:
 	/* Unknown identity or protocol error.  Send failure. */
 	buffer_put_char(&msg, SSH_AGENT_FAILURE);
 send:
 	buffer_put_int(&e->output, buffer_len(&msg));
 	buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
 	key_free(key);
 	BN_clear_free(challenge);
 	buffer_free(&msg);
 }

 /* ssh2 only */
 void
 process_sign_request2(SocketEntry *e)
 {
 	extern int datafellows;
 	Key *key, *private;
 	unsigned char *blob, *data, *signature = NULL;
 	unsigned int blen, dlen, slen = 0;
 	Buffer msg;
 	int ok = -1;

 	datafellows = 0;

 	blob = buffer_get_string(&e->input, &blen);
 	data = buffer_get_string(&e->input, &dlen);
 	buffer_get_int(&e->input);			/* flags, unused */

 	key = dsa_key_from_blob(blob, blen);
 	if (key != NULL) {
 		private = lookup_private_key(key, NULL, 2);
 		if (private != NULL)
 			ok = dsa_sign(private, &signature, &slen, data, dlen);
 	}
 	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);
 	}
 	buffer_put_int(&e->output, buffer_len(&msg));
 	buffer_append(&e->output, buffer_ptr(&msg),
 	    buffer_len(&msg));
 	buffer_free(&msg);
 	xfree(data);
 	xfree(blob);
 	if (signature != NULL)
 		xfree(signature);
 }

 /* shared */
 void
 process_remove_identity(SocketEntry *e, int version)
 {
 	Key *key = NULL, *private;
 	unsigned char *blob;
 	unsigned int blen;
 	unsigned int bits;
 	int success = 0;

 	switch(version){
 	case 1:
 		key = key_new(KEY_RSA);
 		bits = buffer_get_int(&e->input);
 		buffer_get_bignum(&e->input, key->rsa->e);
 		buffer_get_bignum(&e->input, key->rsa->n);

 		if (bits != key_size(key))
 			log("Warning: identity keysize mismatch: actual %d, announced %d",
 			      key_size(key), bits);
 		break;
 	case 2:
 		blob = buffer_get_string(&e->input, &blen);
 		key = dsa_key_from_blob(blob, blen);
 		xfree(blob);
 		break;
 	}
 	if (key != NULL) {
 		int idx;
 		private = lookup_private_key(key, &idx, version);
 		if (private != 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 copy
 			 * data from the last entry.
 			 */
 			Idtab *tab = idtab_lookup(version);
 			key_free(tab->identities[idx].key);
 			xfree(tab->identities[idx].comment);
 			if (idx != tab->nentries)
 				tab->identities[idx] = tab->identities[tab->nentries];
 			tab->nentries--;
 			success = 1;
 		}
 		key_free(key);
 	}
 	buffer_put_int(&e->output, 1);
 	buffer_put_char(&e->output,
 	    success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
 }

 void
 process_remove_all_identities(SocketEntry *e, int version)
 {
 	unsigned int i;
 	Idtab *tab = idtab_lookup(version);

 	/* Loop over all identities and clear the keys. */
 	for (i = 0; i < tab->nentries; i++) {
 		key_free(tab->identities[i].key);
 		xfree(tab->identities[i].comment);
 	}

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

 	/* Send success. */
 	buffer_put_int(&e->output, 1);
 	buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
 	return;
 }

 void
 process_add_identity(SocketEntry *e, int version)
 {
 	Key *k = NULL;
 	RSA *rsa;
 	BIGNUM *aux;
 	BN_CTX *ctx;
 	char *type;
 	char *comment;
 	int success = 0;
 	Idtab *tab = idtab_lookup(version);

 	switch (version) {
 	case 1:
 		k = key_new(KEY_RSA);
 		rsa = k->rsa;

 		/* allocate mem for private key */
 		/* XXX rsa->n and rsa->e are already allocated */
 		rsa->d = BN_new();
 		rsa->iqmp = BN_new();
 		rsa->q = BN_new();
 		rsa->p = BN_new();
 		rsa->dmq1 = BN_new();
 		rsa->dmp1 = BN_new();

 		buffer_get_int(&e->input);		 /* ignored */

 		buffer_get_bignum(&e->input, rsa->n);
 		buffer_get_bignum(&e->input, rsa->e);
 		buffer_get_bignum(&e->input, rsa->d);
 		buffer_get_bignum(&e->input, rsa->iqmp);

 		/* SSH and SSL have p and q swapped */
 		buffer_get_bignum(&e->input, rsa->q);	/* p */
 		buffer_get_bignum(&e->input, rsa->p);	/* q */

 		/* Generate additional parameters */
 		aux = BN_new();
 		ctx = BN_CTX_new();

 		BN_sub(aux, rsa->q, BN_value_one());
 		BN_mod(rsa->dmq1, rsa->d, aux, ctx);

 		BN_sub(aux, rsa->p, BN_value_one());
 		BN_mod(rsa->dmp1, rsa->d, aux, ctx);

 		BN_clear_free(aux);
 		BN_CTX_free(ctx);

 		break;
 	case 2:
 		type = buffer_get_string(&e->input, NULL);
 		if (strcmp(type, KEX_DSS)) {
 			buffer_clear(&e->input);
 			xfree(type);
 			goto send;
 		}
 		xfree(type);

 		k = key_new(KEY_DSA);

 		/* allocate mem for private key */
 		k->dsa->priv_key = BN_new();

 		buffer_get_bignum2(&e->input, k->dsa->p);
 		buffer_get_bignum2(&e->input, k->dsa->q);
 		buffer_get_bignum2(&e->input, k->dsa->g);
 		buffer_get_bignum2(&e->input, k->dsa->pub_key);
 		buffer_get_bignum2(&e->input, k->dsa->priv_key);

 		break;
 	}

 	comment = buffer_get_string(&e->input, NULL);
 	if (k == NULL) {
 		xfree(comment);
 		goto send;
 	}
 	success = 1;
 	if (lookup_private_key(k, NULL, version) == NULL) {
 		if (tab->nentries == 0)
 			tab->identities = xmalloc(sizeof(Identity));
 		else
 			tab->identities = xrealloc(tab->identities,
 			    (tab->nentries + 1) * sizeof(Identity));
 		tab->identities[tab->nentries].key = k;
 		tab->identities[tab->nentries].comment = comment;
 		/* Increment the number of identities. */
 		tab->nentries++;
 	} else {
 		key_free(k);
 		xfree(comment);
 	}
 send:
 	buffer_put_int(&e->output, 1);
 	buffer_put_char(&e->output,
 	    success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
 }

 /* dispatch incoming messages */

 void
 process_message(SocketEntry *e)
 {
 	unsigned int msg_len;
 	unsigned int type;
 	unsigned char *cp;
 	if (buffer_len(&e->input) < 5)
 		return;		/* Incomplete message. */
 	cp = (unsigned char *) buffer_ptr(&e->input);
 	msg_len = GET_32BIT(cp);
 	if (msg_len > 256 * 1024) {
 		shutdown(e->fd, SHUT_RDWR);
 		close(e->fd);
 		e->type = AUTH_UNUSED;
 		return;
 	}
 	if (buffer_len(&e->input) < msg_len + 4)
 		return;
 	buffer_consume(&e->input, 4);
 	type = buffer_get_char(&e->input);

 	switch (type) {
 	/* 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:
 		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;
 	/* 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:
 		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;
 	default:
 		/* Unknown message.  Respond with failure. */
 		error("Unknown message %d", type);
 		buffer_clear(&e->input);
 		buffer_put_int(&e->output, 1);
 		buffer_put_char(&e->output, SSH_AGENT_FAILURE);
 		break;
 	}
 }

 void
 new_socket(int type, int fd)
 {
 	unsigned int i, old_alloc;
 	if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0)
 		error("fcntl O_NONBLOCK: %s", strerror(errno));

 	if (fd > max_fd)
 		max_fd = fd;

 	for (i = 0; i < sockets_alloc; i++)
 		if (sockets[i].type == AUTH_UNUSED) {
 			sockets[i].fd = fd;
 			sockets[i].type = type;
 			buffer_init(&sockets[i].input);
 			buffer_init(&sockets[i].output);
 			return;
 		}
 	old_alloc = sockets_alloc;
 	sockets_alloc += 10;
 	if (sockets)
 		sockets = xrealloc(sockets, sockets_alloc * sizeof(sockets[0]));
 	else
 		sockets = xmalloc(sockets_alloc * sizeof(sockets[0]));
 	for (i = old_alloc; i < sockets_alloc; i++)
 		sockets[i].type = AUTH_UNUSED;
 	sockets[old_alloc].type = type;
 	sockets[old_alloc].fd = fd;
 	buffer_init(&sockets[old_alloc].input);
 	buffer_init(&sockets[old_alloc].output);
 }

 void
 prepare_select(fd_set *readset, fd_set *writeset)
 {
 	unsigned int i;
 	for (i = 0; i < sockets_alloc; i++)
 		switch (sockets[i].type) {
 		case AUTH_SOCKET:
 		case AUTH_CONNECTION:
 			FD_SET(sockets[i].fd, readset);
 			if (buffer_len(&sockets[i].output) > 0)
 				FD_SET(sockets[i].fd, writeset);
 			break;
 		case AUTH_UNUSED:
 			break;
 		default:
 			fatal("Unknown socket type %d", sockets[i].type);
 			break;
 		}
 }

 void
 after_select(fd_set *readset, fd_set *writeset)
 {
 	unsigned int i;
 	int len, sock;
 	socklen_t slen;
 	char buf[1024];
 	struct sockaddr_un sunaddr;

 	for (i = 0; i < sockets_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) {
 					perror("accept from AUTH_SOCKET");
 					break;
 				}
 				new_socket(AUTH_CONNECTION, sock);
 			}
 			break;
 		case AUTH_CONNECTION:
 			if (buffer_len(&sockets[i].output) > 0 &&
 			    FD_ISSET(sockets[i].fd, writeset)) {
 				len = write(sockets[i].fd, buffer_ptr(&sockets[i].output),
 					 buffer_len(&sockets[i].output));
 				if (len <= 0) {
 					shutdown(sockets[i].fd, SHUT_RDWR);
 					close(sockets[i].fd);
 					sockets[i].type = AUTH_UNUSED;
 					buffer_free(&sockets[i].input);
 					buffer_free(&sockets[i].output);
 					break;
 				}
 				buffer_consume(&sockets[i].output, len);
 			}
 			if (FD_ISSET(sockets[i].fd, readset)) {
 				len = read(sockets[i].fd, buf, sizeof(buf));
 				if (len <= 0) {
 					shutdown(sockets[i].fd, SHUT_RDWR);
 					close(sockets[i].fd);
 					sockets[i].type = AUTH_UNUSED;
 					buffer_free(&sockets[i].input);
 					buffer_free(&sockets[i].output);
 					break;
 				}
 				buffer_append(&sockets[i].input, buf, len);
 				process_message(&sockets[i]);
 			}
 			break;
 		default:
 			fatal("Unknown type %d", sockets[i].type);
 		}
 }

 void
 check_parent_exists(int sig)
 {
 	if (parent_pid != -1 && kill(parent_pid, 0) < 0) {
 		/* printf("Parent has died - Authentication agent exiting.\n"); */
 		exit(1);
 	}
 	signal(SIGALRM, check_parent_exists);
 	alarm(10);
 }

 void
 cleanup_socket(void)
 {
 	remove(socket_name);
 	rmdir(socket_dir);
 }

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

 void
 usage()
 {
 	fprintf(stderr, "ssh-agent version %s\n", SSH_VERSION);
 	fprintf(stderr, "Usage: %s [-c | -s] [-k] [command {args...]]\n",
 		__progname);
 	exit(1);
 }

 int
 main(int ac, char **av)
 {
 	fd_set readset, writeset;
 	int sock, c_flag = 0, k_flag = 0, s_flag = 0, ch;
 	struct sockaddr_un sunaddr;
 	pid_t pid;
 	char *shell, *format, *pidstr, pidstrbuf[1 + 3 * sizeof pid];
 	extern int optind;

 	init_rng();

 	/* check if RSA support exists */
 	if (rsa_alive() == 0) {
 		fprintf(stderr,
 			"%s: no RSA support in libssl and libcrypto.  See ssl(8).\n",
 			__progname);
 		exit(1);
 	}
 #ifdef __GNU_LIBRARY__
 	while ((ch = getopt(ac, av, "+cks")) != -1) {
 #else /* __GNU_LIBRARY__ */
 	while ((ch = getopt(ac, av, "cks")) != -1) {
 #endif /* __GNU_LIBRARY__ */
 		switch (ch) {
 		case 'c':
 			if (s_flag)
 				usage();
 			c_flag++;
 			break;
 		case 'k':
 			k_flag++;
 			break;
 		case 's':
 			if (c_flag)
 				usage();
 			s_flag++;
 			break;
 		default:
 			usage();
 		}
 	}
 	ac -= optind;
 	av += optind;

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

 	if (ac == 0 && !c_flag && !k_flag && !s_flag) {
 		shell = getenv("SHELL");
 		if (shell != NULL && strncmp(shell + strlen(shell) - 3, "csh", 3) == 0)
 			c_flag = 1;
 	}
 	if (k_flag) {
 		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 = atoi(pidstr);
 		if (pid < 1) {	/* XXX PID_MAX check too */
 		/* Yes, PID_MAX check please */
 			fprintf(stderr, "%s=\"%s\", which is not a good PID\n",
 				SSH_AGENTPID_ENV_NAME, pidstr);
 			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 %d killed;\n", pid);
 		exit(0);
 	}
 	parent_pid = getpid();

 	/* Create private directory for agent socket */
 	strlcpy(socket_dir, "/tmp/ssh-XXXXXXXX", sizeof socket_dir);
 	if (mkdtemp(socket_dir) == NULL) {
 		perror("mkdtemp: private socket dir");
 		exit(1);
 	}
 	snprintf(socket_name, sizeof socket_name, "%s/agent.%d", socket_dir,
 		 parent_pid);

 	/*
 	 * Create socket early so it will exist before command gets run from
 	 * the parent.
 	 */
 	sock = socket(AF_UNIX, SOCK_STREAM, 0);
 	if (sock < 0) {
 		perror("socket");
 		cleanup_exit(1);
 	}
 	memset(&sunaddr, 0, sizeof(sunaddr));
 	sunaddr.sun_family = AF_UNIX;
 	strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path));
 	if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0) {
 		perror("bind");
 		cleanup_exit(1);
 	}
 	if (listen(sock, 5) < 0) {
 		perror("listen");
 		cleanup_exit(1);
 	}
 	/*
 	 * Fork, and have the parent execute the command, if any, or present
 	 * the socket data.  The child continues as the authentication agent.
 	 */
 	pid = fork();
 	if (pid == -1) {
 		perror("fork");
 		exit(1);
 	}
 	if (pid != 0) {		/* Parent - execute the given command. */
 		close(sock);
 		snprintf(pidstrbuf, sizeof pidstrbuf, "%d", 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 %d;\n", 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);
 	}
 	close(0);
 	close(1);
 	close(2);

 	if (setsid() == -1) {
 		perror("setsid");
 		cleanup_exit(1);
 	}
 	if (atexit(cleanup_socket) < 0) {
 		perror("atexit");
 		cleanup_exit(1);
 	}
 	new_socket(AUTH_SOCKET, sock);
 	if (ac > 0) {
 		signal(SIGALRM, check_parent_exists);
 		alarm(10);
 	}
 	idtab_init();
 	signal(SIGINT, SIG_IGN);
 	signal(SIGPIPE, SIG_IGN);
 	signal(SIGHUP, cleanup_exit);
 	signal(SIGTERM, cleanup_exit);
 	while (1) {
 		FD_ZERO(&readset);
 		FD_ZERO(&writeset);
 		prepare_select(&readset, &writeset);
 		if (select(max_fd + 1, &readset, &writeset, NULL, NULL) < 0) {
 			if (errno == EINTR)
 				continue;
 			exit(1);
 		}
 		after_select(&readset, &writeset);
 	}
 	/* NOTREACHED */
 }
	/* $OpenBSD: ssh-agent.c,v 1.36 2000/09/15 07:13:49 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".
	*
	* SSH2 implementation,
	* Copyright (c) 2000 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"
	RCSID("$OpenBSD: ssh-agent.c,v 1.36 2000/09/15 07:13:49 deraadt Exp $");

	#include "ssh.h"
	#include "rsa.h"
	#include "buffer.h"
	#include "bufaux.h"
	#include "xmalloc.h"
	#include "packet.h"
	#include "getput.h"
	#include "mpaux.h"

	#include <openssl/evp.h>
	#include <openssl/md5.h>
	#include <openssl/dsa.h>
	#include <openssl/rsa.h>
	#include "key.h"
	#include "authfd.h"
	#include "dsa.h"
	#include "kex.h"

	typedef struct {
	int fd;
	enum {
	AUTH_UNUSED, AUTH_SOCKET, AUTH_CONNECTION
	} type;
	Buffer input;
	Buffer output;
	} SocketEntry;

	unsigned int sockets_alloc = 0;
	SocketEntry *sockets = NULL;

	typedef struct {
	Key *key;
	char *comment;
	} Identity;

	typedef struct {
	int nentries;
	Identity *identities;
	} 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;

	/* pathname and directory for AUTH_SOCKET */
	char socket_name[1024];
	char socket_dir[1024];

	#ifdef HAVE___PROGNAME
	extern char *__progname;
	#else /* HAVE___PROGNAME */
	static const char *__progname = "ssh-agent";
	#endif /* HAVE___PROGNAME */

	void
	idtab_init(void)
	{
	int i;
	for (i = 0; i <=2; i++){
	idtable[i].identities = NULL;
	idtable[i].nentries = 0;
	}
	}

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

	/* return matching private key for given public key */
	Key *
	lookup_private_key(Key key, int idx, int version)
	{
	int i;
	Idtab *tab = idtab_lookup(version);
	for (i = 0; i < tab->nentries; i++) {
	if (key_equal(key, tab->identities[i].key)) {
	if (idx != NULL)
	*idx = i;
	return tab->identities[i].key;
	}
	}
	return NULL;
	}

	/* send list of supported public keys to 'client' */
	void
	process_request_identities(SocketEntry *e, int version)
	{
	Idtab *tab = idtab_lookup(version);
	Buffer msg;
	int i;

	buffer_init(&msg);
	buffer_put_char(&msg, (version == 1) ?
	SSH_AGENT_RSA_IDENTITIES_ANSWER : SSH2_AGENT_IDENTITIES_ANSWER);
	buffer_put_int(&msg, tab->nentries);
	for (i = 0; i < tab->nentries; i++) {
	Identity *id = &tab->identities[i];
	if (id->key->type == KEY_RSA) {
	buffer_put_int(&msg, BN_num_bits(id->key->rsa->n));
	buffer_put_bignum(&msg, id->key->rsa->e);
	buffer_put_bignum(&msg, id->key->rsa->n);
	} else {
	unsigned char *blob;
	unsigned int blen;
	dsa_make_key_blob(id->key, &blob, &blen);
	buffer_put_string(&msg, blob, blen);
	xfree(blob);
	}
	buffer_put_cstring(&msg, id->comment);
	}
	buffer_put_int(&e->output, buffer_len(&msg));
	buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
	buffer_free(&msg);
	}

	/* ssh1 only */
	void
	process_authentication_challenge1(SocketEntry *e)
	{
	Key key, private;
	BIGNUM *challenge;
	int i, len;
	Buffer msg;
	MD5_CTX md;
	unsigned char buf[32], mdbuf[16], session_id[16];
	unsigned int response_type;

	buffer_init(&msg);
	key = key_new(KEY_RSA);
	challenge = BN_new();

	buffer_get_int(&e->input); /* ignored */
	buffer_get_bignum(&e->input, key->rsa->e);
	buffer_get_bignum(&e->input, key->rsa->n);
	buffer_get_bignum(&e->input, challenge);

	/* Only protocol 1.1 is supported */
	if (buffer_len(&e->input) == 0)
	goto failure;
	buffer_get(&e->input, (char *) session_id, 16);
	response_type = buffer_get_int(&e->input);
	if (response_type != 1)
	goto failure;

	private = lookup_private_key(key, NULL, 1);
	if (private != NULL) {
	/* Decrypt the challenge using the private key. */
	rsa_private_decrypt(challenge, challenge, private->rsa);

	/* The response is MD5 of decrypted challenge plus session id. */
	len = BN_num_bytes(challenge);
	if (len <= 0 \|\| len > 32) {
	log("process_authentication_challenge: bad challenge length %d", len);
	goto failure;
	}
	memset(buf, 0, 32);
	BN_bn2bin(challenge, buf + 32 - len);
	MD5_Init(&md);
	MD5_Update(&md, buf, 32);
	MD5_Update(&md, session_id, 16);
	MD5_Final(mdbuf, &md);

	/* Send the response. */
	buffer_put_char(&msg, SSH_AGENT_RSA_RESPONSE);
	for (i = 0; i < 16; i++)
	buffer_put_char(&msg, mdbuf[i]);
	goto send;
	}

	failure:
	/* Unknown identity or protocol error. Send failure. */
	buffer_put_char(&msg, SSH_AGENT_FAILURE);
	send:
	buffer_put_int(&e->output, buffer_len(&msg));
	buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
	key_free(key);
	BN_clear_free(challenge);
	buffer_free(&msg);
	}

	/* ssh2 only */
	void
	process_sign_request2(SocketEntry *e)
	{
	extern int datafellows;
	Key key, private;
	unsigned char blob, data, *signature = NULL;
	unsigned int blen, dlen, slen = 0;
	Buffer msg;
	int ok = -1;

	datafellows = 0;

	blob = buffer_get_string(&e->input, &blen);
	data = buffer_get_string(&e->input, &dlen);
	buffer_get_int(&e->input); /* flags, unused */

	key = dsa_key_from_blob(blob, blen);
	if (key != NULL) {
	private = lookup_private_key(key, NULL, 2);
	if (private != NULL)
	ok = dsa_sign(private, &signature, &slen, data, dlen);
	}
	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);
	}
	buffer_put_int(&e->output, buffer_len(&msg));
	buffer_append(&e->output, buffer_ptr(&msg),
	buffer_len(&msg));
	buffer_free(&msg);
	xfree(data);
	xfree(blob);
	if (signature != NULL)
	xfree(signature);
	}

	/* shared */
	void
	process_remove_identity(SocketEntry *e, int version)
	{
	Key key = NULL, private;
	unsigned char *blob;
	unsigned int blen;
	unsigned int bits;
	int success = 0;

	switch(version){
	case 1:
	key = key_new(KEY_RSA);
	bits = buffer_get_int(&e->input);
	buffer_get_bignum(&e->input, key->rsa->e);
	buffer_get_bignum(&e->input, key->rsa->n);

	if (bits != key_size(key))
	log("Warning: identity keysize mismatch: actual %d, announced %d",
	key_size(key), bits);
	break;
	case 2:
	blob = buffer_get_string(&e->input, &blen);
	key = dsa_key_from_blob(blob, blen);
	xfree(blob);
	break;
	}
	if (key != NULL) {
	int idx;
	private = lookup_private_key(key, &idx, version);
	if (private != 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 copy
	* data from the last entry.
	*/
	Idtab *tab = idtab_lookup(version);
	key_free(tab->identities[idx].key);
	xfree(tab->identities[idx].comment);
	if (idx != tab->nentries)
	tab->identities[idx] = tab->identities[tab->nentries];
	tab->nentries--;
	success = 1;
	}
	key_free(key);
	}
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output,
	success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
	}

	void
	process_remove_all_identities(SocketEntry *e, int version)
	{
	unsigned int i;
	Idtab *tab = idtab_lookup(version);

	/* Loop over all identities and clear the keys. */
	for (i = 0; i < tab->nentries; i++) {
	key_free(tab->identities[i].key);
	xfree(tab->identities[i].comment);
	}

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

	/* Send success. */
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
	return;
	}

	void
	process_add_identity(SocketEntry *e, int version)
	{
	Key *k = NULL;
	RSA *rsa;
	BIGNUM *aux;
	BN_CTX *ctx;
	char *type;
	char *comment;
	int success = 0;
	Idtab *tab = idtab_lookup(version);

	switch (version) {
	case 1:
	k = key_new(KEY_RSA);
	rsa = k->rsa;

	/* allocate mem for private key */
	/* XXX rsa->n and rsa->e are already allocated */
	rsa->d = BN_new();
	rsa->iqmp = BN_new();
	rsa->q = BN_new();
	rsa->p = BN_new();
	rsa->dmq1 = BN_new();
	rsa->dmp1 = BN_new();

	buffer_get_int(&e->input); /* ignored */

	buffer_get_bignum(&e->input, rsa->n);
	buffer_get_bignum(&e->input, rsa->e);
	buffer_get_bignum(&e->input, rsa->d);
	buffer_get_bignum(&e->input, rsa->iqmp);

	/* SSH and SSL have p and q swapped */
	buffer_get_bignum(&e->input, rsa->q); /* p */
	buffer_get_bignum(&e->input, rsa->p); /* q */

	/* Generate additional parameters */
	aux = BN_new();
	ctx = BN_CTX_new();

	BN_sub(aux, rsa->q, BN_value_one());
	BN_mod(rsa->dmq1, rsa->d, aux, ctx);

	BN_sub(aux, rsa->p, BN_value_one());
	BN_mod(rsa->dmp1, rsa->d, aux, ctx);

	BN_clear_free(aux);
	BN_CTX_free(ctx);

	break;
	case 2:
	type = buffer_get_string(&e->input, NULL);
	if (strcmp(type, KEX_DSS)) {
	buffer_clear(&e->input);
	xfree(type);
	goto send;
	}
	xfree(type);

	k = key_new(KEY_DSA);

	/* allocate mem for private key */
	k->dsa->priv_key = BN_new();

	buffer_get_bignum2(&e->input, k->dsa->p);
	buffer_get_bignum2(&e->input, k->dsa->q);
	buffer_get_bignum2(&e->input, k->dsa->g);
	buffer_get_bignum2(&e->input, k->dsa->pub_key);
	buffer_get_bignum2(&e->input, k->dsa->priv_key);

	break;
	}

	comment = buffer_get_string(&e->input, NULL);
	if (k == NULL) {
	xfree(comment);
	goto send;
	}
	success = 1;
	if (lookup_private_key(k, NULL, version) == NULL) {
	if (tab->nentries == 0)
	tab->identities = xmalloc(sizeof(Identity));
	else
	tab->identities = xrealloc(tab->identities,
	(tab->nentries + 1) * sizeof(Identity));
	tab->identities[tab->nentries].key = k;
	tab->identities[tab->nentries].comment = comment;
	/* Increment the number of identities. */
	tab->nentries++;
	} else {
	key_free(k);
	xfree(comment);
	}
	send:
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output,
	success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
	}

	/* dispatch incoming messages */

	void
	process_message(SocketEntry *e)
	{
	unsigned int msg_len;
	unsigned int type;
	unsigned char *cp;
	if (buffer_len(&e->input) < 5)
	return; /* Incomplete message. */
	cp = (unsigned char *) buffer_ptr(&e->input);
	msg_len = GET_32BIT(cp);
	if (msg_len > 256 * 1024) {
	shutdown(e->fd, SHUT_RDWR);
	close(e->fd);
	e->type = AUTH_UNUSED;
	return;
	}
	if (buffer_len(&e->input) < msg_len + 4)
	return;
	buffer_consume(&e->input, 4);
	type = buffer_get_char(&e->input);

	switch (type) {
	/* 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:
	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;
	/* 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:
	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;
	default:
	/* Unknown message. Respond with failure. */
	error("Unknown message %d", type);
	buffer_clear(&e->input);
	buffer_put_int(&e->output, 1);
	buffer_put_char(&e->output, SSH_AGENT_FAILURE);
	break;
	}
	}

	void
	new_socket(int type, int fd)
	{
	unsigned int i, old_alloc;
	if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0)
	error("fcntl O_NONBLOCK: %s", strerror(errno));

	if (fd > max_fd)
	max_fd = fd;

	for (i = 0; i < sockets_alloc; i++)
	if (sockets[i].type == AUTH_UNUSED) {
	sockets[i].fd = fd;
	sockets[i].type = type;
	buffer_init(&sockets[i].input);
	buffer_init(&sockets[i].output);
	return;
	}
	old_alloc = sockets_alloc;
	sockets_alloc += 10;
	if (sockets)
	sockets = xrealloc(sockets, sockets_alloc * sizeof(sockets[0]));
	else
	sockets = xmalloc(sockets_alloc * sizeof(sockets[0]));
	for (i = old_alloc; i < sockets_alloc; i++)
	sockets[i].type = AUTH_UNUSED;
	sockets[old_alloc].type = type;
	sockets[old_alloc].fd = fd;
	buffer_init(&sockets[old_alloc].input);
	buffer_init(&sockets[old_alloc].output);
	}

	void
	prepare_select(fd_set readset, fd_set writeset)
	{
	unsigned int i;
	for (i = 0; i < sockets_alloc; i++)
	switch (sockets[i].type) {
	case AUTH_SOCKET:
	case AUTH_CONNECTION:
	FD_SET(sockets[i].fd, readset);
	if (buffer_len(&sockets[i].output) > 0)
	FD_SET(sockets[i].fd, writeset);
	break;
	case AUTH_UNUSED:
	break;
	default:
	fatal("Unknown socket type %d", sockets[i].type);
	break;
	}
	}

	void
	after_select(fd_set readset, fd_set writeset)
	{
	unsigned int i;
	int len, sock;
	socklen_t slen;
	char buf[1024];
	struct sockaddr_un sunaddr;

	for (i = 0; i < sockets_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) {
	perror("accept from AUTH_SOCKET");
	break;
	}
	new_socket(AUTH_CONNECTION, sock);
	}
	break;
	case AUTH_CONNECTION:
	if (buffer_len(&sockets[i].output) > 0 &&
	FD_ISSET(sockets[i].fd, writeset)) {
	len = write(sockets[i].fd, buffer_ptr(&sockets[i].output),
	buffer_len(&sockets[i].output));
	if (len <= 0) {
	shutdown(sockets[i].fd, SHUT_RDWR);
	close(sockets[i].fd);
	sockets[i].type = AUTH_UNUSED;
	buffer_free(&sockets[i].input);
	buffer_free(&sockets[i].output);
	break;
	}
	buffer_consume(&sockets[i].output, len);
	}
	if (FD_ISSET(sockets[i].fd, readset)) {
	len = read(sockets[i].fd, buf, sizeof(buf));
	if (len <= 0) {
	shutdown(sockets[i].fd, SHUT_RDWR);
	close(sockets[i].fd);
	sockets[i].type = AUTH_UNUSED;
	buffer_free(&sockets[i].input);
	buffer_free(&sockets[i].output);
	break;
	}
	buffer_append(&sockets[i].input, buf, len);
	process_message(&sockets[i]);
	}
	break;
	default:
	fatal("Unknown type %d", sockets[i].type);
	}
	}

	void
	check_parent_exists(int sig)
	{
	if (parent_pid != -1 && kill(parent_pid, 0) < 0) {
	/* printf("Parent has died - Authentication agent exiting.\n"); */
	exit(1);
	}
	signal(SIGALRM, check_parent_exists);
	alarm(10);
	}

	void
	cleanup_socket(void)
	{
	remove(socket_name);
	rmdir(socket_dir);
	}

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

	void
	usage()
	{
	fprintf(stderr, "ssh-agent version %s\n", SSH_VERSION);
	fprintf(stderr, "Usage: %s [-c \| -s] [-k] [command {args...]]\n",
	__progname);
	exit(1);
	}

	int
	main(int ac, char **av)
	{
	fd_set readset, writeset;
	int sock, c_flag = 0, k_flag = 0, s_flag = 0, ch;
	struct sockaddr_un sunaddr;
	pid_t pid;
	char shell, format, pidstr, pidstrbuf[1 + 3 sizeof pid];
	extern int optind;

	init_rng();

	/* check if RSA support exists */
	if (rsa_alive() == 0) {
	fprintf(stderr,
	"%s: no RSA support in libssl and libcrypto. See ssl(8).\n",
	__progname);
	exit(1);
	}
	#ifdef __GNU_LIBRARY__
	while ((ch = getopt(ac, av, "+cks")) != -1) {
	#else /* __GNU_LIBRARY__ */
	while ((ch = getopt(ac, av, "cks")) != -1) {
	#endif /* __GNU_LIBRARY__ */
	switch (ch) {
	case 'c':
	if (s_flag)
	usage();
	c_flag++;
	break;
	case 'k':
	k_flag++;
	break;
	case 's':
	if (c_flag)
	usage();
	s_flag++;
	break;
	default:
	usage();
	}
	}
	ac -= optind;
	av += optind;

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

	if (ac == 0 && !c_flag && !k_flag && !s_flag) {
	shell = getenv("SHELL");
	if (shell != NULL && strncmp(shell + strlen(shell) - 3, "csh", 3) == 0)
	c_flag = 1;
	}
	if (k_flag) {
	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 = atoi(pidstr);
	if (pid < 1) { /* XXX PID_MAX check too */
	/* Yes, PID_MAX check please */
	fprintf(stderr, "%s=\"%s\", which is not a good PID\n",
	SSH_AGENTPID_ENV_NAME, pidstr);
	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 %d killed;\n", pid);
	exit(0);
	}
	parent_pid = getpid();

	/* Create private directory for agent socket */
	strlcpy(socket_dir, "/tmp/ssh-XXXXXXXX", sizeof socket_dir);
	if (mkdtemp(socket_dir) == NULL) {
	perror("mkdtemp: private socket dir");
	exit(1);
	}
	snprintf(socket_name, sizeof socket_name, "%s/agent.%d", socket_dir,
	parent_pid);

	/*
	* Create socket early so it will exist before command gets run from
	* the parent.
	*/
	sock = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sock < 0) {
	perror("socket");
	cleanup_exit(1);
	}
	memset(&sunaddr, 0, sizeof(sunaddr));
	sunaddr.sun_family = AF_UNIX;
	strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path));
	if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0) {
	perror("bind");
	cleanup_exit(1);
	}
	if (listen(sock, 5) < 0) {
	perror("listen");
	cleanup_exit(1);
	}
	/*
	* Fork, and have the parent execute the command, if any, or present
	* the socket data. The child continues as the authentication agent.
	*/
	pid = fork();
	if (pid == -1) {
	perror("fork");
	exit(1);
	}
	if (pid != 0) { /* Parent - execute the given command. */
	close(sock);
	snprintf(pidstrbuf, sizeof pidstrbuf, "%d", 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 %d;\n", 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);
	}
	close(0);
	close(1);
	close(2);

	if (setsid() == -1) {
	perror("setsid");
	cleanup_exit(1);
	}
	if (atexit(cleanup_socket) < 0) {
	perror("atexit");
	cleanup_exit(1);
	}
	new_socket(AUTH_SOCKET, sock);
	if (ac > 0) {
	signal(SIGALRM, check_parent_exists);
	alarm(10);
	}
	idtab_init();
	signal(SIGINT, SIG_IGN);
	signal(SIGPIPE, SIG_IGN);
	signal(SIGHUP, cleanup_exit);
	signal(SIGTERM, cleanup_exit);
	while (1) {
	FD_ZERO(&readset);
	FD_ZERO(&writeset);
	prepare_select(&readset, &writeset);
	if (select(max_fd + 1, &readset, &writeset, NULL, NULL) < 0) {
	if (errno == EINTR)
	continue;
	exit(1);
	}
	after_select(&readset, &writeset);
	}
	/* NOTREACHED */
	}